JP2000229214A - Recovering device and recovering method for hydrophilic solvent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recovering device and a recovering method for a water- containing solvent, which is for recovering a high purity solvent from a hydrophilic solvent containing water by the adsorption and separation of water, made compact and highly efficient and secured in all of the safety and durability. SOLUTION: An air tight vessel 2 is provided with a solvent introducing part 3 for introducing the hydrophilic solvent containing water, a vaporizing part 4 of the solvent and a water adsorption part 5 filled with an adsorbent capable of adsorbing and desorbing vaporized water in the part 4, a heater 8 and a cooler 9 in direct contact with the adsorbent are provided together in the water adsorbing part 5, the solvent introducing part 3 is arranged at the uppermost part of the air tight vessel 2, the vaporizing part 4 and the water adsorption part 5 are arranged successively below the solvent introducing part 3 to enable to rapidly heat and cool and to attain uniform adsorption and efficient desorption in the adsorption part 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for efficiently recovering a high-purity solvent by absorbing and removing water from a hydrophilic solvent such as alcohol or acetone containing water (hereinafter referred to as a water-containing solvent). Apparatus and method.

[0002]

2. Description of the Related Art Typical methods for recovering this kind of aqueous solvent include a distillation method, a membrane separation method and an adsorption method. A general method of removing water from a water-containing solvent is a distillation method, but an azeotropic phenomenon occurs even in the case of a hydrophilic solvent, so that a general distillation cannot obtain a solvent having a certain concentration or more. . Although there is an extractive distillation method for recovering a high-concentration solvent, it is not energy efficient and it is difficult to reduce the size.

[0003] As the membrane separation method, there are a perpetualization (PV) method and a gas separation method (GS method). In the PV method, not only the temperature inside the system decreases due to the latent heat of moisture evaporation, but also the permeation rate decreases. When the amount of moisture is large, the membrane area required for permeation increases. Further, in order to ensure a constant transmission speed, the size of the vacuum device is increased, and a problem occurs in the durability of the film. The GS method also requires a vacuum pump, which inevitably increases the size of the apparatus.

In the adsorption method, the water in a water-containing solvent is adsorbed on an adsorbent to recover the solvent. In order to uniformly contact the water-containing solvent and the adsorbent, the adsorbent is formed into particles or spheres. . In general, a method in which a hydrated solvent is brought into contact with an adsorbent in a liquid state, but there is also a method in which the solvent is vaporized and adsorbed by the adsorbent.

When the water-containing solvent is liquid, local flow (drift) is likely to occur, and it is difficult to use the adsorbent effectively. Since the water is unbalanced during regeneration (during heat desorption), the water concentration is low. In the high portion, the adsorbing ability of the adsorbent was reduced, or the shape was easily broken, and powder or particles were easily formed. Usually, as a method of heating the adsorbent, a gas that removes moisture adsorbed by the adsorbent in the regeneration process is often used as an indirect heat medium, and when the gas is air, it is dangerous, The running cost is increased due to heat loss and the like, and it is uneconomical to use an inert gas such as nitrogen. In any case, the apparatus becomes large and the initial cost cannot be avoided.

According to the invention described in Japanese Patent Publication No. 6-103132, for example, according to the reversible cold heat generator, heating at the time of reactivating the adsorbent is performed by heating a heater attached to the outer wall of the container. According to this heating method, it takes a long time for the adsorbent at the center of the container to reach a predetermined temperature, and the portion of the adsorbent in contact with the inner wall of the container has a large temperature difference as compared with the adsorbent at the center. Since the adsorbent is used in a state in which the adsorbent is generated, it is difficult for the adsorbent to be in a sufficiently reactivated state, and it is difficult for the adsorbent to exhibit its originally required capacity. Therefore, according to the invention described in this publication, the sheath heater is disposed directly in the container filled with the adsorbent, and the adsorbent is directly heated. At the time of this heating, a porous metal or a metal plate is arranged so as to maintain a gap between the heating surface of the sheathed heater and the heat generating surface of the sheathed heater, thereby preventing the adsorbent from deteriorating and realizing uniform heating.

However, when such an adsorbent is used as a solvent recovery device as described above, it is necessary to rapidly heat the adsorbent to desorb adsorbed water when reactivating the adsorbent. In addition, rapid cooling at the time of adsorption is strongly required in order to ensure efficiency and the life of the adsorbent. That is, it is preferable that the switching from the desorption to the adsorption be performed in as short a time as possible. However, according to the invention described in the above publication, rapid heating and temperature unevenness during reactivation can be eliminated, but rapid cooling during adsorption is impossible.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a specific object of the present invention is to provide an apparatus for recovering a solvent by absorbing and separating water from a water-containing solvent. Another object of the present invention is to provide a high-purity aqueous solvent recovery apparatus and a method for recovering the same, which ensure safety and durability.

[0009]

In order to achieve the above object, in particular, for the cleaning solvent such as IPA used in a clean room such as a semiconductor manufacturing process, an adsorption method among the above-mentioned solvent recovery methods. Was determined to be desirable because a high-purity solvent was obtained and the recovery rate was high. Therefore, the present invention basically provides a method for recovering a solvent from a water-containing solvent by adsorbing water efficiently on an adsorbent to separate and recover the solvent, and efficiently reactivating the adsorbent. I decided to adopt the law.

[0010] By adopting the configuration described in the claims of the present application, the above-mentioned problem is solved more efficiently and economically. That is, in the invention according to claim 1, there is provided an apparatus for recovering a solvent from a hydrophilic solvent containing water, which is housed in an airtight container and introduces a hydrophilic solvent containing water, A vaporizing section for the solvent, and a water adsorbing section filled with an adsorbent capable of adsorbing and desorbing water vaporized in the vaporizing section, and the water adsorbing section is in direct contact with the adsorbent. A heater and a cooler are juxtaposed to constitute a hydrophilic solvent recovery device.

When the gas containing water is boiled and vaporized, when the gas comes into contact with a low-temperature wall surface or gas, its heat capacity is liquefied. The liquefied part flows locally, or the adsorbent that comes into contact with the liquefied part and the gas part that has vaporized the water-containing solvent, respectively, has a significantly different amount of adsorbed moisture.
The overall adsorption efficiency also decreases. As a method of not partially liquefying the vaporized gas, there is a method of heating the temperature of the vaporized gas to a temperature equal to or higher than the evaporation temperature. However, if the adsorption temperature is too high, the adsorption capacity of moisture decreases. In order to keep the water-containing solvent gas near the evaporation temperature and to uniformly distribute the vapor concentration and the temperature on the cross section of the container, an evaporating means for that is necessary. The following methods can be considered as the means.

1. A portion below the evaporation temperature, a portion much higher than the gas and the evaporation temperature, and the like are eliminated between the evaporation surface and the surface of the adsorbent so that a uniform and necessary amount of heat is supplied to all the portions. 2. A non-combustible gas heated to near the evaporation temperature of the water-containing solvent is supplied, and the partial pressure of the solvent gas is reduced to prevent condensation and liquefaction. 3. Even if the water-containing solvent once vaporized condenses and liquefies through an inorganic fiber structural material such as alumina cloth or metal fiber, the liquid is uniformly dispersed. Here, the inorganic fiber structural material refers to a nonwoven fabric, a woven knitted fabric, a net, a braid, or the like manufactured from a metal fiber, a carbon fiber, or the like.

In addition, in the adsorption method, after adsorbing moisture by the adsorbent, heated air or an inert gas is brought into contact with the adsorbent, and the heated air is used as a heat medium to evaporate (desorb) moisture to remove the adsorbent. Playing. When such a gas having a small heat capacity is used as a heat medium, a large amount of gas is required,
Not only is the transfer power and heat loss high, but the use of an inert gas such as nitrogen as a heat medium to ensure safety is extremely uneconomical.

In the present invention, when an inert gas is introduced into the vaporizing section for explosion protection when moisture is adsorbed by the adsorbent, the inert gas for reducing the partial pressure of water during regeneration of the adsorbent is used. The active gas functions as a carrier gas, and it is possible to heat the adsorbent by direct heat conduction from a heat source such as a heater to perform desorption of moisture in the adsorbent while maintaining the desorption performance of the adsorbent. Become. Thereafter, the adsorbent is forcibly cooled, and the next cycle of moisture adsorption is performed again.

That is, at the time of regeneration, a heater is energized and heated to desorb moisture from an adsorbent such as zeolite that has absorbed moisture by heat conduction. Usually, zeolite has low values of thermal conductivity and specific heat (0.00147 cal / cm. ° C, sec., 0.24 cal /
℃ .g), unlike other materials with high thermal conductivity, even if a temperature difference is given to zeolite by a heater, heat is not easily transmitted, and it becomes a partially overheated state where the temperature becomes extremely high locally.
Hydrous zeolites are also destroyed when heated rapidly to high temperatures. In order to avoid this partial overheating, it is necessary to increase the surface area of the heater for the zeolite per unit volume as much as possible. Therefore, in the present invention, the cooler is made to function as a part of the heater by utilizing the heat conduction from the heater at the time of heating.

The cooler of the present invention functions as a part of the heater at the time of heating as described above, and cools the adsorbent to a temperature at which the adsorbent exerts its adsorbing performance because the adsorbent cannot adsorb moisture at a high temperature. Means. For this cooling, there are methods of natural cooling and contact with gas, but because the cooling rate is slow, a refrigerant liquid such as water is passed through the pipe, the zeolite is rapidly cooled by latent heat of evaporation and heat conduction, and the cycle time is shortened. , To reduce the size of the device. At this time, a jacket is preferably attached to the outer wall of the airtight container to cool the entire container from the outside.

In the invention according to claim 2, the solvent introduction section is arranged at the uppermost portion of the closed vessel, and the vaporization section and the water adsorption section are arranged sequentially below the solvent introduction section. . If the adsorbent and the water-containing solvent to be treated can be brought into direct contact with each other in a liquid state, the device can be made compact,
Since the adsorption temperature is low, the adsorption efficiency is increased. However, since the liquid hydrated solvent flows locally in the adsorption tank (drift), it is generally difficult to uniformly contact the adsorbent.
For this reason, in the present invention, before the water-containing solvent is brought into contact with the adsorbent, the water-containing solvent is vaporized in the vaporizing section to reduce the drift of the water-containing solvent. Further, the apparatus can be made compact by arranging the solvent introduction section at the uppermost part of the closed vessel and sequentially arranging the vaporization section and the adsorption section below it. This is based on the fact that the vapor from the vaporization of a water-containing solvent flows downward because the molecular weight of the vapor is heavy compared to the molecular weight of air. This is because it can be done.

According to a third aspect of the present invention, the heater and the cooler are arranged side by side in a crosswise manner inside the water adsorption section.
No matter how the shape of the heater and cooler is improved to rapidly heat and cool the adsorbent, there is a limit in increasing their surface area. Therefore, in the present invention, in order to further increase the heat conduction surface, a pipe-shaped metal cooler, which is much more excellent in heat conduction than zeolite, is juxtaposed by contacting with a pipe-shaped sheathed heater and heating. Sometimes a cooler is also used as a heat conductor for a part of the heating element, and at the time of cooling, the sheath heater functions as a cooling element. By adopting such a configuration, it is possible to greatly increase the surface area for heat conduction to the adsorbent, not only to enable rapid heating and rapid cooling, but also to perform uniform heat conduction to the adsorbent. Can be. Of course, it is necessary to remove moisture in the cooler at the time of desorption heating.

On the other hand, at the time of rapid heating or rapid cooling, the cooler and the heater which are in contact with each other as described above come into friction with each other due to thermal expansion. Due to this friction, minute metal powder is generated from the friction surface. When the metal powder comes into contact with the adsorbent, for example, zeolite exerts a catalytic action such as dehydrogenation or dehydration of the organic gas in the system to promote carbonization or tarification of the organic gas, and impurities are mixed into the solvent. Or adversely affect the durability of the zeolite. Therefore, it is necessary to adopt a structure in which the heater and the cooler do not rub against each other even when the temperature changes. The structure is such that pipe-shaped heaters and coolers are arranged in a meandering manner, and are arranged so as to intersect each other in the vertical and horizontal directions. This is preferable because it can be suppressed to a minimum.

According to a fourth aspect of the present invention, the structure of the vaporizing section for a water-containing solvent is specified. According to the invention,
The vaporization section has a solvent supply pipe for dropping a water-containing solvent, and a sheath heater and an inert gas supply pipe disposed below the solvent supply pipe and covered with the inorganic fiber structural material described above. . Then, it is preferable that the shapes of the supply pipes and the sheathed heaters are made substantially the same, and the members are arranged vertically so that the projections of the respective members become the same.

As described above, it is better to adsorb a water-containing solvent in a gaseous state than to adsorb it in a liquid state as it is in a liquid state.
This is preferable because it can uniformly contact the adsorbent without drifting. Moreover, in order to efficiently evaporate and evaporate the water-containing solvent, it is desirable that the water-containing solvent be brought into direct contact with the heater. However, if the water-containing solvent is directly dropped or flowed on the heater surface, only a part of the water-containing solvent dropped on the heater surface is rapidly heated and the liquid is scattered, so-called puffing occurs. Loss and carbonization or tarification produce impurities such as carbides, and reduce the heating efficiency of the heater.

Therefore, in the present invention, an inert gas supply pipe is provided below the sheathed heater so that the inert gas is supplied when necessary. In addition, if the water-containing solvent is dropped directly from above the heater, the solvent is tarred or carbonized due to non-uniform contact, so it is necessary to control the heater to a temperature at which the solvent, including moisture, evaporates. is there. With the sheathed heater and the inert gas supply pipe arranged vertically, the peripheral surface is covered with at least a metal fiber structure and an inorganic fiber structure. Due to the presence of these fibrous structures, the hydrated solvent dropped from the hydrated solvent supply pipe forms a uniform liquid film on the entire surface of the fibrous structures, during which it is completely vaporized. If not covered with a fibrous structure, in particular, water may run down the heater surface before evaporation, or liquid splashed off by puffing may flow as a drift through voids in the adsorbent below.

At this time, since the molecular weight of the water-containing solvent is larger than the molecular weight of nitrogen, the solvent vapor moves downward. Therefore, a carrier gas, a gas compressor, and the like, which are necessary for safely moving the space between the adsorbents filled in the closed container with the solvent vapor downward safely, are not required. Here, the inert gas as a carrier gas refers to a gas component for preventing the solvent remaining in the system at the time of desorption from evaporating into a combustible gas, but burning this gas.

In the above-described combustible gas system, according to experiments by the present inventors, if the oxygen concentration value in the system is below a predetermined value, the explosion range disappears and artificial ignition occurs. It has been found that combustion does not occur. The value of the oxygen concentration at this time differs depending on the type of combustible gas. In addition, the concentration of the combustible gas in the system decreases with the elapse of the heating time and becomes lower than the lower limit explosion range after a predetermined time. Therefore, even if ordinary air is used as the carrier gas, no explosion or combustion occurs. Therefore, if the concentration of the flammable gas in the system is equal to or lower than the lower limit of the explosion even in the air, it can be referred to as an inert gas in the system, and safety is ensured.

In the present invention, in order to reduce the size of the apparatus and increase the efficiency of desorption, the temperature in the system is rapidly increased at the time of desorption. The higher the temperature in a high-temperature atmosphere and the higher the partial pressure of water, the more easily the zeolite is destroyed. Therefore, as one means for ensuring the durability of the adsorbent, at the time of desorption, the heater is actively heated rapidly, and at the same time, a minimum amount of inert gas or non-combustible gas is allowed to flow into the system. The partial pressure of water vapor is reduced. That is, in the present invention, expensive inert gas such as nitrogen or carbon dioxide is not used to ensure the safety of the apparatus and the durability of zeolite, but only when necessary. It supplies an active gas. Therefore, the amount of use of an inert gas such as nitrogen can be greatly reduced, which is economical and at the same time ensures safety.

According to a fifth aspect of the present invention, a plurality of the water adsorbing portions are vertically arranged in multiple stages in the same closed container, and the respective stages are communicated with each other. When the solvent has a high affinity for water, it is difficult to completely separate the water in the solvent by the adsorbent simply by providing a set of water adsorbing portions. Therefore, in the present invention, a plurality of water adsorbing parts are arranged vertically communicating with each other,
A similar adsorption process is performed in multiple stages. At this time, it is preferable to change the performance of the adsorbent for each stage because a high-purity solvent can be recovered. That is, in the first stage, an adsorbent having a large amount of adsorbed water is selected, and an adsorbent having a high adsorptivity that strongly adsorbs water is disposed in a lower stage. This is because the lower the concentration, the higher the concentration of the solvent, and if the solvent has a high water absorption capacity, it absorbs the surrounding water, making it difficult to obtain a high-purity solvent. An adsorbent having an adsorbing power is provided.

According to a sixth aspect of the present invention, there is provided an efficient method for recovering a solvent from a water-containing solvent. The method includes introducing the hydrophilic solvent containing water toward a heater and vaporizing the hydrophilic solvent. The desorbable water adsorbent is directly cooled or heated by using both a pipe-shaped cooler and a pipe-shaped heater to control a predetermined temperature required for adsorption and desorption, and the adsorbent is maintained at a predetermined temperature by the cooler. While being performed, the vaporized water and the hydrophilic solvent are brought into contact with the adsorbent to adsorb the water, the solvent is collected simultaneously with the adsorption of water, and the adsorbent is collected after the solvent is collected. The method includes heating by the heater to desorb water.

As described above, even in the present invention, the water-containing solvent is vaporized and then brought into contact with an adsorbent rapidly cooled to a predetermined temperature by a pipe-shaped cooler to adsorb water.
Separate and recover the solvent. When the recovery of the solvent is completed, the adsorbent is rapidly heated by the same pipe-shaped heater to perform desorption. At the time of cooling by the cooler, the components of the heater arranged in parallel are used as a heat conductor, and at the time of heating by the heater, the components of the cooler are also used as a heat conductor. For this reason, the heat conduction surface area at the time of heating and cooling with respect to the adsorbent increases, and uniform and rapid heating and cooling over the entire adsorbent becomes possible, and efficient adsorption and desorption of moisture becomes possible.

The invention according to claim 7 includes introducing an inert gas at the time of vaporization of the water-containing solvent and at the time of desorption of water adsorbed on the adsorbent. The introduction of the inert gas prevents the explosion of the solvent gas, which is a combustible gas, rather than the carrier gas used to transport the boiling vaporized water-containing solvent gas, and at the same time lowers the partial pressure of water to improve the performance of the adsorbent. It has a function as a carrier gas to be maintained. Therefore, its introduction is not performed at the time of adsorption, but at the time of vaporization and desorption of the water-containing solvent. In the flammable gas system, no explosion occurs when the oxygen concentration value is equal to or less than a predetermined value. In some cases, air and nitrogen gas may be mixed and introduced at a predetermined ratio.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below along with comparative examples with reference to the drawings. FIG. 1 schematically shows an apparatus for recovering a water-containing solvent according to a typical embodiment of the present invention. The water-containing solvent recovery device according to the present invention,
A vaporizing section for vaporizing the water-containing solvent and a water adsorbing section which is arranged in communication with the lower side of the vaporizing section and is filled with an adsorbent capable of adsorbing and desorbing water vaporized in the vaporizing section are provided as a single unit. It is housed in an airtight container, and adopts a structure in which a heater and a cooler that are in direct contact with the adsorbent are provided side by side in the water adsorbing section.

Here, in the present invention, the vaporized portion of the water-containing solvent and the water adsorbing portion which adsorbs water in the vaporized solvent to the adsorbent and separates the solvent from the solvent are formed as one set. However, in order to recover a high-purity (99.9% by weight or more) solvent, a plurality of sets of water-containing solvents are continuously connected to a plurality of water adsorption sections. Through which water is adsorbed in multiple stages.

In the illustrated example, the vaporizing section and the water adsorbing section are arranged at the uppermost stage in a single closed container 1, and the lower part thereof is disposed below the vaporizing section and the water adsorbing section.
Arrange the water adsorbing parts of the steps and connect them to each other
Fig. 3 shows a water-containing solvent recovery device composed of a water adsorption section in a stage. In FIG. 1, reference numeral 1 denotes a water-containing solvent recovery device, and a water-containing solvent introduction unit 3 for introducing a water-containing solvent into a vaporization unit 4 in the container is disposed on a ceiling portion of a single closed container 2. A water-containing solvent vaporizer 4 and a water adsorber 5 are disposed immediately below the water-containing solvent inlet 3, and the second and third water adsorbers 5 are further disposed below the water adsorber 5. Arranged over the bottom. Further, a solvent recovery port 6 is provided on the bottom surface of the closed vessel 2, and is connected to a solvent recovery tank (not shown) via an open / close valve and a cooler (not shown).

In this embodiment, the water-containing solvent introducing section 3
Comprises a solvent dropping pipe 3 having a structure as shown in FIGS. 2 to 4, and both ends 3a and 3b of the solvent dropping pipe 3 are circulated through an open / close valve (not shown) to a water-containing solvent supply source outside the container. Have been. According to the illustrated example, the solvent dropping tube 3 is constituted by a metal tube bent in a substantially M shape, and the solvent dropping tube 3 thus configured is horizontally installed. The lower surface of the solvent dropping tube 3 has a number of small holes 3 communicating with the inside of the tube.
a is formed, and the water-containing solvent flowing in the pipe is dripped downward from the small hole 3a.

A plurality of (four in the illustrated example) water-containing solvent vaporizers 4 provided from the top to the bottom of the closed vessel 2 all have the same structure, each of which has a sheath heater 4a and nitrogen gas supply / discharge. It has a tube 4b, of which the sheathed heater 4a and the nitrogen gas supply / discharge tube 4b have substantially the same dimensions and substantially the same M shape as the solvent dropping tube 3. Numerous small holes (not shown) are also formed in the nitrogen gas supply / discharge pipe 4b. The sheathed heater 4a and the nitrogen gas supply / discharge tube 4b are laminated according to their tube shapes as shown in FIGS. 2 to 4, and the sheathed heater 4a and the nitrogen gas supply / discharge tube 4b are spotted. They are integrated by welding. The sheath heater 4a is automatically turned on and off by a switching circuit (not shown). The nitrogen gas supply / discharge pipe 4b has a gas supply port 4b-1 at one end thereof and a gas discharge port 4b-2 at the other end thereof respectively shown via open / close valves (not shown). Connected to a nitrogen gas supply source and a discharge pipe.

Further, in this embodiment, the sheathed heater 4a
The peripheral surface of the nitrogen gas supply / discharge pipe 4b is covered with an inorganic fiber structure 7. Examples of the material of the fibrous structure 7 include metal fibers such as stainless steel and ceramic fibers. The fibrous structure 7 is manufactured from these fibers as a fibrous structure 7 such as a nonwoven fabric, a woven or knitted fabric, a braid, or a net. The structure 7 is wound around and fixed to the peripheral surfaces of the sheathed heater 4a and the nitrogen gas supply / discharge pipe 4b. When the sheath heater 4a and the nitrogen gas supply / discharge pipe 4b are covered with the fiber structure 7, heat exchange is sufficiently performed, and the nitrogen gas is quickly heated to a required temperature. Accordingly, the periphery of the sheathed heater is made to have a uniform inert atmosphere, and at the same time, the water-containing solvent dropped from above is uniformly distributed around the heater through the fibers, and can be efficiently and safely vaporized and vaporized.

On the other hand, the water adsorbing section 5 disposed below the vaporizing section 4 with a required space interposed therebetween is provided with an adsorbent packed layer (not shown) and inside the adsorbent filled layer. And a pipe-shaped cooler 9 as well as a pipe-shaped heater 8. The heater 8 and the cooler 9 are made of stainless steel or Inconel, or a metal tube material plated with chromium, gold, platinum, or the like. An electric heating wire is inserted through the heater 8, and a cooling medium such as water is passed through the cooler 9. Is passed. Both of them are bent in a zigzag shape, and are arranged so that they come into contact with each other and cross each other in the same vertical plane, with the zigzag directions of each other up and down and laterally.

As described above, when the heater 8 and the cooler 9 are crossed and arranged so as to be in contact with each other at the crossing portion, for example, when the heater 8 is energized to generate heat, a heat quantity from the crossing portion is reduced. The part is conducted to the cooler 9, and the cooler itself functions as a heater. Therefore, the heating area for the adsorbent is greatly increased, and uniform and rapid heating becomes possible. The same is true for cooling, enabling rapid cooling. Of course, the cooling medium flows into the cooler 9 during cooling, and the cooling medium is discharged from the cooler 9 during heating.

Also, by arranging the heater 8 and the cooler 9 formed in a zigzag shape as described above so as to intersect each other and to make contact at the intersection, the heater 8 and the cooler 9 can be used for rapid heating and rapid cooling. As described above, the cooler and the heater that are in contact with each other do not rub against each other due to thermal expansion. If the cooler 8 and the heater 9 rub against each other, fine metal powder is generated from the friction surface due to the friction.
When the metal powder comes into contact with the adsorbent, for example, zeolite exerts a catalytic action such as dehydrogenation or dehydration of the organic gas in the system to promote carbonization or tarification of the organic gas, and impurities are mixed into the solvent. Or reduces the durability of the zeolite. Therefore, it is necessary to adopt a structure in which the heater 8 and the cooler 9 do not rub against each other even when the temperature changes. As the structure, the present invention employs the above-described configuration to minimize the movement of the contact portion even when the heater 8 and the cooler 9 behave due to thermal expansion of each other.

On the other hand, zeolite is used as the adsorbent. The upper water adsorbing section 5 has an X-type zeolite having a high water absorbing capacity, and the suspended water adsorbing section 5 has a quantitative water absorbing capacity. A type zeolite having low but strong adsorption power is used, and Y type zeolite having high adsorption power and ion exchange capacity is used for the lower water adsorption section 5.

Next, a solvent recovery procedure and a recovery mechanism by the apparatus of this embodiment having the above-described configuration will be described. First, the upper and lower four-stage sheath heaters 4a are energized to generate heat, and a two-way control valve (not shown) is switched to introduce nitrogen gas from the gas supply port 4b-1 of the uppermost nitrogen gas supply / discharge pipe 4b. At this time, the oxygen in the air inside the sealed container 2 is diluted with nitrogen gas, and the amount of nitrogen gas introduced is controlled so that the concentration becomes lower than the explosion lower limit range.

Next, the open / close valve (not shown) of the solvent dropping pipe 3 is opened to introduce the water-containing solvent into the solvent dropping pipe 3. The water-containing solvent introduced into the solvent dropping pipe 3 is a small hole 3a of the solvent dropping pipe 3.
From the surface of the inorganic fiber structure 7 wound on the peripheral surface of the sheath heater 4a and the nitrogen gas supply / discharge pipe 4b at the uppermost stage. At this time, the vaporized water vapor and the solvent gas, together with the nitrogen gas, are distributed substantially uniformly in the horizontal cross-sectional direction of the closed vessel 2 due to the presence of the inorganic fiber structure 7, and are transferred to the lower adsorption section 4 having a low internal pressure by the respective sheath heaters. 4a, the flow continues while maintaining the evaporation state,
It contacts the adsorbent 8 filled in the water adsorbing section 5 of each stage evenly without uneven flow.

When the vaporized water vapor and the solvent gas flow down, if the water adsorbing section 5 maintains the high temperature state at the time of the previous desorption, the water adsorbing section 5 does not adsorb water. The power supply of 8 is turned off, water or a water-containing solvent is passed through the inside of the pipe-shaped cooler 9 as a refrigerant liquid, and the adsorbent is actively cooled to a predetermined adsorption temperature. At this time,
At the same time, the heater 8 is also cooled by heat conduction by the cooler 9 and functions as a cooler for cooling the adsorbent that comes into contact with the heater 8, so that the surface area of heat conduction with respect to the adsorbent increases as a whole, and the adsorbing portions are evenly and uniformly formed. Rapid cooling. Here, in particular, when a water-containing solvent is passed as a refrigerant liquid, vaporization is rapidly achieved by introducing the water-containing solvent used during cooling and warmed into the solvent introduction section 2.

Each adsorbing section 5 which has reached a predetermined adsorbing temperature has
Water vapor vaporized from above, solvent gas, and nitrogen gas are flowing down together and continuously.While the residual water vapor is absorbed by zeolite, the molecular weight of the solvent gas must be larger than that of nitrogen gas. From there, the solvent gas flows sequentially to the lower adsorption section 5, is cooled by cooling means through a collection pipe connected to the bottom of the closed vessel 2, becomes liquid, and is sequentially collected in a solvent collection section (not shown) outside the vessel. . Therefore, by the time the collection is completed, the adsorption section 4 in each stage gradually becomes a nitrogen gas atmosphere.

Further, according to this embodiment, as described above, the upper water adsorbing section 5 has an X-type zeolite having a high quantitative water absorbing capacity, and the suspended water adsorbing section 5 has a low quantitative water absorbing capacity. Since the A-type zeolite having a strong adsorption force and the Y-type zeolite having the strong adsorption force and the ion-exchange ability are also used in the lower water adsorption section 5, the water vapor and the solvent gas are:
A large amount of water vapor is adsorbed in the upper water adsorbing section 5, and the water vapor concentration in the middle water adsorbing section 5 is drastically reduced but still remains. In addition, when the solvent has a very high affinity for water such as IPA,
Moisture is adsorbed by the solvent gas and cannot be easily adsorbed by the material of the adsorbent arranged in the upper stage. Therefore, in the present embodiment, the A-type zeolite having a strong adsorption force is used as described above, so that even the water adsorbed by the solvent gas can be strongly adsorbed.

On the other hand, the Y-type zeolite disposed in the lower adsorbing section 5 has a strong water-absorbing power similarly to the middle-stage zeolite, and also has an ion exchange reaction with ionized metals contained in the water-containing solvent. To remove metals. Therefore,
The lower adsorption section 5 can strongly absorb water vapor and metal ions from a solvent gas containing a very small amount of water vapor and metal ions, and can recover, for example, 99.9 wt% of high-purity IPA. .

Now, the recovery of the solvent proceeds in this way,
If the amount of water absorbed by the adsorbent increases and the adsorption capacity decreases,
The adsorbent is regenerated by evaporating and removing (desorbing) the adsorbed water. At the time of this regeneration, the refrigerant liquid remaining in the pipe is discharged to the outside from the pipe-shaped cooler 9 of each stage, and then all the pipe-shaped heaters 8 are energized and heated. When the surface of the heater 8 is heated, the cooler 9 which is in contact with the heater 8 in an intersecting state becomes hot due to latent heat of evaporation and heat conduction, and functions as a part of the heater. As a result, despite the fact that the heater 8 and the cooler 9 are juxtaposed, the heating area for the adsorbent is almost doubled, and since the heater 8 and the cooler 9 are distributed over the whole, the zeolite has low specific heat and low thermal conductivity. However, the desorption can be performed efficiently without being locally low or high.

In this embodiment, a necessary amount of nitrogen gas is introduced into the closed vessel 2 at the time of desorption according to a predetermined procedure, and discharged from the inside of the vessel to the outside. These procedures are performed by automatically operating various control (open / close) valves and switches in accordance with a sequence written in a control device (not shown) together with the procedure at the time of suction. Of course, it can also be performed by operation of a worker.

By the way, the higher the rate of temperature rise, the higher the temperature in a high-temperature atmosphere, and the higher the partial pressure of water, the lower the capacity of the zeolite to adsorb water, and finally it may be destroyed. The vaporized vapor, the solvent gas, and the nitrogen gas are simultaneously flowing down from above in the water adsorbing section 5, and as described above, at the time of desorption, rapid heating is actively performed by the heater, and at the same time, the necessary minimum An inert gas, a non-combustible gas, or the like is allowed to flow into the system to reduce the partial pressure of water vapor. As one means for securing the durability of the adsorbent, that is, in the present invention, in order to secure the safety of the apparatus and the durability of the zeolite, inert gas such as expensive nitrogen gas or carbon dioxide gas is used. The gas is not always used but an inert gas such as nitrogen gas is supplied only when necessary. Therefore, the amount of use of an inert gas such as nitrogen can be greatly reduced, and it is economical.
At the same time, safety is ensured.

An example of a procedure for introducing and discharging nitrogen gas at the time of desorption will be described in detail. First, in FIG. 1, the uppermost nitrogen gas supply / discharge pipe 4b of the upper and lower four nitrogen gas supply / discharge pipes 4b is shown. Opening an open / close valve (not shown) of the gas supply port 4b-1 of the pipe 4b, and opening an open / close valve (not shown) of the gas outlet 4b-2 of the nitrogen gas supply / discharge pipe 4b from the second stage to the lowermost stage, A required amount of nitrogen gas is introduced into the closed container 2 from the nitrogen gas supply / discharge pipe 4b. At this time, all the pipe-shaped heaters 8 are energized and heated, and the adsorbed water continues to be desorbed from each adsorbing section 5. In this water vapor, the nitrogen gas introduced from the uppermost nitrogen gas supply / discharge pipe 4b functions as a carrier gas, and is discharged to the outside from each of the middle and lower nitrogen gas supply / discharge pipes 4b together with the nitrogen gas. This operation is continued for a predetermined time. In this embodiment, the operation time is 25 minutes.

When the first-stage desorption operation is completed, the gas supply port 4b of the uppermost nitrogen gas supply / discharge pipe 4b
-1 and a gas supply port of the second-stage nitrogen gas supply / discharge pipe 4b at the same time as opening and closing a valve of the gas discharge port 4b-2 of the uppermost nitrogen gas supply / discharge pipe 4b. 4b-1 An opening / closing valve (not shown) is opened to supply a required amount of nitrogen gas into the closed container 2 from the nitrogen gas supply / discharge pipe 4b.

As a result, the nitrogen gas flows toward the uppermost nitrogen gas exhaust pipe 4c and the third and fourth nitrogen gas exhaust pipes 4c together with the water vapor remaining in the closed vessel 2, and goes to the outside. Is discharged. Next, for example, the opening / closing valve of the gas supply port 4b-1 of the nitrogen gas supply / discharge pipe 4b of the second stage is closed, and the opening / closing valve of the gas discharge port 4b-2 of the gas supply / discharge pipe 4b is opened. The on-off valve of the gas supply port 4b-1 of the nitrogen gas supply / discharge pipe 4b is opened, and a required amount of nitrogen gas is introduced into the closed container 2 from the nitrogen gas supply / discharge pipe 4b. By this operation, all of the water vapor (moisture) remaining inside the closed container 2, especially near the bottom, flows upward together with the nitrogen gas, and is discharged to the outside through the nitrogen gas discharge pipes 4c from the top to the third stage. I do.

Such operations are performed a required number of times to desorb water from each water adsorbing section 5 and to remove water from the inside of the closed vessel 2 to regenerate the zeolite disposed in each water adsorbing section 5. . Note that the above-described procedure for supplying and discharging nitrogen gas is merely an example, and the operating procedure may be changed depending on the situation at that time.

The above is a description of typical examples of the present invention. Next, the present invention will be described more specifically with comparative examples. "Specific Example 1" Using a solvent recovery device having substantially the same basic structure as the solvent recovery device according to the above embodiment,
Solvent recovery operations were performed by a flow-down system in which IPA vapor flows from the top to the bottom of the apparatus and a rising system in which IPA vapor flows from the bottom to the top. Here, in the method in which the solvent vapor flows from the bottom to the top of the apparatus, it is necessary to forcibly collect a solvent having a large molecular weight by suction, and it is necessary to add a suction pump, a cooler, and the like for that purpose.
The entire device had to be enlarged.

Table 1 shows the comparison table. The adsorbent used was Zeolam F9 (trade name) in the upper stage, Zeolam F4 (trade name) in the middle stage, and Zeolam F4 (trade name) in the lower stage. These zeolites are 14 to 30 mesh crushed zeolites 14 to 30 (manufactured by Tosoh Corporation).

[0055]

[Table 1]

As can be understood from Table 1, in the ascending method, the size of the apparatus is increased, and the lower limit of the concentration range of the IPA that can be processed is 0.8 wt%.

Next, the difference in performance between the above-described embodiment of the vaporization method for a water-containing solvent in the present invention and the solvent recovery apparatus according to the modified example was examined. Table 2 shows the results. In the above embodiment, as described above, the supply pipe 3 for the water-containing solvent and the vaporizing section are separated, and in the vaporizing section, the sheath heater 4a and the nitrogen gas supply / discharge pipe 4b are laminated, and the peripheral surface thereof is formed of an inorganic fiber structure. 7. On the other hand, in the modified example, as shown in FIG. 5, a sheath heater 4a and a nitrogen gas supply / discharge pipe 4b whose peripheral surface is covered with an inorganic fiber structure 7 and a supply pipe 3 of the water-containing solvent are provided inside a porous container 10. And a gap formed between the container 10 and the supply pipe 3 and the inorganic fiber structure 7 is filled with an alumina fiber braid. The filler may be a nonwoven fabric of the fibrous metal or various heat-resistant inorganic fibers, the same fiber cloth, the same fiber assembly, or the like. Further, the container 10 is a box-shaped container formed of a punching metal, a wire mesh, or a porous refractory inorganic material.

The apparatus used is a single-stage recovery apparatus comprising the uppermost stage having no three-stage recovery processing section in the above embodiment, the nitrogen gas inflow rate is 10 L / min, and the sheath heater is 1,800 W. Zeolite F-9 (trade name) as adsorbent
2.5 kg, the component ratio of the water-containing solvent was IPA: water = 70: 30, and the throughput was 1.5 kg / h.

[0059]

[Table 2]

As can be understood from Table 2, the modified example is superior in terms of the concentration of IPA and the yield of IPA, despite the small temperature difference of zeolite. This is presumably because the presence of the filler reduces the deviation of the water vapor and the IPA gas in the modified example, and the level difference of the heat of vaporization is small.

Table 3 is based on the difference in the adsorption method between the liquid contact system in which the aqueous solvent is passed through the adsorbent in a liquid state and the gas contact system in which the vaporized aqueous solvent is brought into contact with the adsorbent in three steps according to the above embodiment. The result which compared the performance of each collection | recovery apparatus is shown. However, the liquid contact method is a one-stage process.

[0062]

[Table 3]

However, the vaporizing method is a filling type of the alumina inorganic fiber unbalanced material.

As is apparent from Table 3, there is a large difference between the purity of the recovered IPA and the recovery rate of the IPA between the vaporized contact method according to the present invention and the conventional liquid contact method. Cannot be used as a cleaning liquid in a semiconductor manufacturing process requiring an IPA purity of 99.52%, for example, 99.9%.

Table 4 shows that, in the present invention, when a pipe-shaped cooler is installed in the suction section, when the cooler is not installed,
And a comparison of the cooling time of the adsorption unit when a pipe-shaped cooler is installed and a cooling jacket is installed on the outer wall surface of the closed vessel. From this table, it can be understood whether the installation of the cooler in the present invention leads to a reduction in the cooling time in the following. In addition, it is also shown that, if a cooling jacket is provided on the outer wall surface of the airtight container, the cooling efficiency at the corner of the suction section is further increased. Note that the pipe-shaped cooler is arranged in a zigzag shape that is folded in the horizontal direction.

[0066]

[Table 4]

Table 5 shows the results of comparison of the juxtaposition of heaters and coolers in the suction section according to the present invention and various performances of the juxtaposed arrangement. The heater and the cooler are installed in a zigzag shape and in directions intersecting each other. The symbol PPC in the table indicates a case where the pipe-shaped cooler is folded in the vertical direction and arranged in a zigzag shape. The material of the pipe-shaped cooler is SUS304, the material of the pipe-shaped heater is 316L,
The heater power at the time of desorption is 3 kW, the material of the sealed container is SUS304 with hard chrome plating, and the adsorbent is 2.5 g of Zeorum F9 (Tosoh Corporation, trade name, crushed product of 14-30 mesh). I have.

[0068]

[Table 5]

According to Table 5, by arranging the pipe-shaped heater and the pipe-shaped cooler formed in a zigzag shape so as to intersect each other in the vertical direction and the horizontal direction, both are cooled and heated during cooling. It can be understood that it also functions as a heater and a cooler, and the heater and the cooler are connected to each other via a metal joint, when they are simply in point contact, and when the pipe-shaped cross section is slightly flattened to make surface contact. In this case, it can be understood that the most effective case is the case of surface contact. It is also preferable to arrange the pipe-shaped heater in a zigzag manner in the vertical direction, and to arrange the pipe-shaped cooler in the horizontal direction so as to be substantially orthogonal to the heater. It is effective and the device can be made compact.

This is because, when the refrigerant liquid used for cooling is discharged from the pipe-shaped cooler at the time of desorption, if the cooler is folded up and down and arranged in a zigzag manner, the internal refrigerant liquid is forcibly discharged. Unless otherwise, it remains in the pipe. Therefore, not only the heat exchange efficiency is reduced, but also as shown in Table 5, at the time of adsorption, the IPA is cooled by the low-temperature refrigerant liquid remaining inside the pipe-shaped cooler. , The IPA recovery rate decreases. On the other hand, when the pipe-shaped cooler is slightly inclined in the horizontal direction and folded back in a zigzag shape, the refrigerant liquid existing in the pipe flows downward by its own weight and can be efficiently and promptly discharged. That's why.

Table 6 shows the results of combustion experiments based on the mixing ratio of the inert gas and the solvent (IPA) gas in the present invention. FIG. 6 is a cross-sectional view showing a schematic structure of the mixed gas supply device used in the experiment. A mixed gas of IPA gas, nitrogen gas and air was introduced from the mixed gas supply device into the closed space, and an ignition experiment was performed in the same container. As a result, it is understood that there is a case where the air alone does not ignite depending on the situation. In particular, when nitrogen gas is mixed, it can be understood that ignition does not occur if nitrogen is added to air so that the IPA concentration is 2 to 12%.

[0072]

[Table 6]

Table 7 shows IPA obtained by changing the supply / discharge operation procedure of the inert gas at the time of desorption by the apparatus of the present invention.
Shows the difference in the recovery concentration. The water-containing solvent at this time was IPA: water = 90: 10 in weight ratio, and an inert gas (85% by weight of nitrogen and 15% by weight of oxygen) was used as a carrier gas.
Is mixed with the same amount. In addition, the supply temperature of the inert gas is set at 300 ° C. and room temperature. As can be understood from this table, it is necessary to heat the inert gas, and it is important to alternately supply and discharge the gas from above and below.

[0074]

[Table 7]

Table 8 is a comparison table of the energy required for vaporizing water-containing IPA by supplying water-containing IPA, which is a water-containing solvent to be treated, into the pipe cooler instead of tap water as the zeolite refrigerant liquid in the pipe-shaped cooler. is there.
From this table, it can be understood that it is more effective to use water-containing IPA as the refrigerant liquid. This is because the refrigerant liquid is warmed during cooling. The water content of IPA at this time was 3
0 wt%.

[0076]

[Table 8]

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a solvent recovery device of the present invention.

FIG. 2 is a plan view showing a specific example of a vaporizing unit according to the present invention, partially cut away;

FIG. 3 is a front view of the vaporizing section.

FIG. 4 is a side view of the same.

FIG. 5 is a cross-sectional view schematically showing a modification of the vaporizing section.

FIG. 6 is a sectional view showing a schematic structure of an ignition device for a solvent gas.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solvent recovery apparatus 2 Airtight container 3 Hydrous solvent introduction part (hydrous solvent dropping pipe) 3a Small hole 4 Vaporization part 4a Seeds heater 4b Nitrogen gas supply / discharge pipe 4b-1 Gas supply port 4b-2 Gas discharge port 5 Adsorption part 6 Solvent Collection port 7 Inorganic fiber structure 8 Pipe-shaped heater 9 Pipe-shaped cooler 10 Porous container

Claims (7)

[Claims] 1. An apparatus for recovering a solvent from a hydrophilic solvent containing water, comprising: a solvent introduction part accommodated in an airtight container, for introducing a hydrophilic solvent containing water; And a water adsorber filled with an adsorbent capable of adsorbing and desorbing water vaporized in the unit, wherein a heater and a cooler in direct contact with the adsorbent are juxtaposed in the water adsorber. An apparatus for recovering a hydrophilic solvent. 2. The recovery apparatus according to claim 1, wherein the solvent introduction section is arranged at the top of a closed vessel, and the vaporization section and the water adsorption section are arranged sequentially below the solvent introduction section. 3. The apparatus for recovering a hydrophilic solvent according to claim 1, wherein the heater and the cooler are arranged in a cross-shaped surface contact. 4. The vaporizer according to claim 1, wherein the vaporizer has a sheath heater and a nitrogen gas supply pipe disposed below the solvent introduction section and covered with an inorganic fiber structural material. The collecting device according to the above. 5. A plurality of water adsorbing portions are vertically arranged in multiple stages in the same closed container, and each stage communicates with each other.
5. The recovery device according to any one of 4. 6. A method for recovering a solvent from a hydrophilic solvent containing water, the method comprising introducing the hydrophilic solvent containing water toward a heater and vaporizing the same, and adsorbing and desorbing water. Is directly cooled or heated by using a pipe-shaped cooler and a pipe-shaped heater in combination to control the temperature to a predetermined temperature required for adsorption and desorption. While the adsorbent is cooled by the cooler, the vaporized vapor and hydrophilic Contacting a water-soluble solvent with the adsorbent to adsorb moisture, recovering the solvent simultaneously with the adsorption of water, and heating the adsorbent by the heater after the solvent is collected to desorb water. A method for recovering a hydrophilic solvent, comprising: 7. The method according to claim 6, further comprising introducing nitrogen gas during vaporization of the hydrophilic solvent containing water and during desorption of the water adsorbed on the adsorbent.