JP6559082B2 - Isopropyl alcohol recovery device and recovery method - Google Patents

Description

  The present invention relates to an apparatus and a method for recovering isopropyl alcohol from isopropyl alcohol-containing water containing basic impurities.

Isopropyl alcohol (IPA) is used in large quantities as a cleaning agent, solvent, and synthetic raw material for the chemical industry. In particular, in a semiconductor manufacturing process in manufacturing a semiconductor device, a large amount of IPA is used for cleaning and drying. For example, a drying method using IPA for removing moisture after performing pure water cleaning on a semiconductor device is effective as a step of removing moisture. High purity IPA is used for this moisture removal step.
The manufacturing cost of high-purity IPA is high, which may contribute to an increase in the manufacturing cost of semiconductor devices.
Therefore, if IPA can be concentrated and recovered from the IPA-containing water discharged from the semiconductor manufacturing process, and supplied to the purification process for reuse, the purchase cost of high-purity IPA can be reduced. The manufacturing cost can be reduced. Furthermore, the reuse of IPA can contribute to a reduction in the cost of using IPA in various applications.
As a method for obtaining an alcohol concentrate from an alcohol-containing aqueous solution, a method using an ultrasonic atomization method is known. Patent Document 1 discloses a method for producing an alcohol concentrate containing high-concentration alcohol by mist-forming an alcohol-containing aqueous solution by ultrasonic vibration to generate a mist having a high alcohol concentration and separating and recovering the mist. ing.

JP 2007-118055 A

In the waste liquid containing isopropyl alcohol used as a cleaning agent or a solvent in various manufacturing processes, basic impurities such as ammonia may be contained.
Accordingly, an object of the present invention is to provide an apparatus and a method for efficiently recovering isopropyl alcohol from isopropyl alcohol-containing water containing basic impurities.

The isopropyl alcohol recovery device according to the present invention is:
An apparatus for recovering isopropyl alcohol from isopropyl alcohol-containing water containing basic impurities,
Acid addition means for adding an acid to the isopropyl alcohol-containing water;
Ultrasonic atomizing means for generating a mist of isopropyl alcohol-containing water to which the acid is added;
Mist condensing means for obtaining an isopropyl alcohol concentrate by condensation of the mist;
Have
The method for recovering isopropyl alcohol according to the present invention includes:
A method for recovering isopropyl alcohol from isopropyl alcohol-containing water containing basic impurities,
An acid addition step of adding an acid to the isopropyl alcohol-containing water;
An ultrasonic atomization step of generating a mist of isopropyl alcohol-containing water to which the acid is added;
A mist condensation step for obtaining an isopropyl alcohol concentrate by condensation of the mist;
Have

  ADVANTAGE OF THE INVENTION According to this invention, the apparatus and method which collect | recover isopropyl alcohol efficiently from IPA containing water containing a basic impurity can be provided.

It is a figure which shows an example of an apparatus structure at the time of applying the isopropyl alcohol collection | recovery apparatus concerning this invention to a semiconductor device manufacturing apparatus.

An isopropyl alcohol (IPA) recovery apparatus according to the present invention is an apparatus for recovering IPA from IPA-containing water containing basic impurities, and an acid addition means for adding an acid to IPA-containing water containing basic impurities; It comprises at least ultrasonic atomizing means for generating mist from IPA-containing water to which an acid has been added, and mist condensing means for obtaining an IPA concentrate by condensation of mist.
The acid addition means includes a mixing region in which IPA-containing water containing basic impurities and acid are mixed, a supply system that supplies IPA-containing water containing basic impurities to the mixing region, and a supply system that supplies acid to the mixing region. Can be configured. For example, a pump for supplying an amount of acid required for the acid addition treatment to the mixing region and a flow rate control device may be connected by piping.
IPA-containing water containing a salt of a basic impurity by adding an acid by the acid addition means is supplied to the ultrasonic atomization means as treated water.

As the ultrasonic atomizing means, an ultrasonic atomizing device capable of generating mist of water to be treated by ultrasonic waves can be used, and an apparatus capable of generating mist from IPA-containing water containing a salt of basic impurities as water to be treated. If so, the configuration is not limited. For example, a liquid phase region for generating mist by applying ultrasonic waves to water to be treated from an ultrasonic generator having an ultrasonic vibrator, and a gas phase region that can hold the generated mist in a state where it can be taken out. An apparatus having an ultrasonic atomization tank to be formed can be used.
In order to increase the IPA concentration in the mist, a multi-stage ultrasonic atomizing apparatus in which a plurality of ultrasonic atomizing tanks are connected in series can also be used.
In addition, you may utilize an ultrasonic atomization tank as a mixing area | region for the acid addition to the IPA containing water containing a basic impurity.
The mist generated from the water to be treated by the ultrasonic atomizing means is transported to the condensing means and liquefied by condensation, so that the concentration of IPA is higher than the water to be treated and the concentration of basic impurities is low. Can be obtained.
As the condensing means, various condensing devices such as a condenser having a built-in cooling device can be used.
The mist can be transported from the ultrasonic atomizing means to the condensing means by placing the mist on an airflow generated by an airflow generating means such as a blower pump.

  Patent Document 1 discloses that an ultrasonic atomization method can be used to recover alcohol from an alcohol-containing aqueous solution. It is thought that water-soluble basic impurities such as ammonia have a high affinity with water and remain relatively more on the treated water phase side than the mist side generated in the gas phase in the ultrasonic atomization tank. . However, according to the study of the present inventor, in the case of basic impurities such as ammonia, the mist in which the amount of basic impurities is not sufficiently reduced is generated in the gas phase due to transfer to the mist together with IPA. Was found. Further, according to the study by the present inventor, the basic impurities in the water phase to be treated are in a salt state, that is, the IPA-containing water is in a state containing basic impurities and an acid salt. It was found that the migration from the water phase to be treated to the mist side released into the gas phase is suppressed. The reason is that the basic impurities are strongly bonded to the water molecules, and the portion where the basic impurities and the water molecules are combined is in the gas phase as compared with the IPA molecules and water molecules which are free from the basic impurities. It is thought that it is difficult to be released as a mist. For these reasons, it is considered that the addition of an acid for forming a salt of a basic impurity can suppress the transfer of the basic impurity to the mist.

Airflow classification means for classifying mist generated in the ultrasonic atomization means can be disposed between the ultrasonic atomization means and the condensation means as necessary.
The mist generated in the ultrasonic atomizing means includes mists having different particle sizes (mass). According to the study of the present inventor, it has been found that the content of basic impurities is reduced in a mist having a high IPA concentration.
Therefore, the mist obtained from the water to be treated includes a small particle size mist containing IPA at a higher concentration than the water to be treated and a reduced content of basic impurities, and a lower concentration than the small particle size mist. IPA and high-concentration basic impurities are contained, and mists with a large particle size are classified, and small-particle mists are collected and liquefied by condensation. An IPA concentrated water with a reduced content can be obtained.
As the airflow classifying means, various airflow classifying devices can be used, and the configuration is not limited as long as the above-described classification is possible. From the viewpoint that the small particle size mist can be more efficiently supplied to the condensing means and can be efficiently concentrated even for water to be treated having a low IPA concentration, a cyclone classifier is preferable.
In addition, in order to prevent the condensation of the target mist in the path | route from an ultrasonic atomization means to a condensation means, the temperature control of the apparatus which comprises a path | route can be performed as needed.

An embodiment of an IPA recovery apparatus according to the present invention is shown in FIG.
The IPA recovery apparatus shown in FIG. 1 is connected to a semiconductor manufacturing apparatus.
The IPA recovery apparatus shown in FIG. 1A includes a recovery tank 2 that stores IPA-containing water recovered from the semiconductor manufacturing apparatus 1, an acid aqueous solution supply system 4, an ultrasonic atomization tank 5, a blower pump 9, a cyclone 6, It has a condenser 7 and a concentrate recovery tank 8.
The acid aqueous solution supply means 4 has a tank (not shown) for storing the acid aqueous solution, and a supply system for supplying the acid aqueous solution from the tank to a mixing region for adding and mixing the IPA-containing water. The acid aqueous solution supply system may be provided with a liquid feed pump and a flow rate control device. The IPA-containing water fed by the liquid feed pump 3 contains basic impurities, and a salt of basic impurities and acid is formed in the IPA-containing water by the addition of the acid aqueous solution. That is, at least a part of the basic impurities (preferably 90% by mass or more of the total amount of basic impurities) is contained in the IPA-containing water in a salt state with the added acid.
The ultrasonic atomization tank 5 constitutes an ultrasonic atomization means. The ultrasonic atomization tank 5 is supplied with IPA-containing water containing a salt of a basic impurity and an acid generated by adding an acid aqueous solution as treated water. Mist is generated by applying ultrasonic waves to the water to be treated supplied to the ultrasonic atomization tank 5.
Further, the mist contains a small particle mist containing a higher concentration of IPA than the water to be treated and having a reduced content of salt of basic impurities and acid, and a lower concentration than the small particle mist. A large particle size mist containing IPA and a high concentration of basic impurities and having a large particle size is included. These small particle size mist and large particle size mist are classified by a blower pump 9 and a cyclone 6, and the classified small particle size mist is supplied to a condenser 7 which is a condensing means to condense and liquefy the small particle size mist. And collect in the concentrate recovery tank 8 as an IPA concentrate.
The air flow by the blower gas supplied to the gas phase region of the ultrasonic atomization tank 5 by the blower pump 9 is returned to the blower pump 9 through the cyclone 6 and the condenser 7 to form a blower gas circulation system. Moreover, the residual liquid of the ultrasonic atomization tank 5 and the cyclone 6 is returned to the collection tank 2.

The recovery device shown in FIG. 1 (B) connects a dehydration membrane 10 to the concentrated liquid recovery tank 8 in the recovery device shown in FIG. 1 (A), and sends purified IPA through a dehydration treatment by the dehydration membrane 10. The liquid pump 12 has a configuration in which a liquid feeding system to be sent to the supply tank 11 to the semiconductor manufacturing apparatus 1 is added.
The dehydration membrane 10 is a membrane that performs membrane dehydration by pervaporation (PV) or vapor permeation (VP) on the IPA concentrate collected in the concentrate collection tank 8, and further passes through the dehydration membrane. Concentration can be performed. The dehydration membrane 10 can take the form of a water permeable membrane module, for example. Examples of the material constituting the membrane include polymer materials such as polyimide, cellulose, and polyvinyl alcohol, and inorganic materials such as zeolite. From the viewpoints of mechanical strength, dehydration performance, heat resistance, etc., a zeolite membrane is preferred.

An ultrasonic atomization apparatus having an ultrasonic atomization tank can have a multistage configuration in which a plurality of ultrasonic wave atomization tanks and a condenser are connected in series.
Also, the cyclone classifier may be a multistage type in which a plurality of cyclone towers are connected in series.
In the recovery apparatus shown in FIGS. 1 (A) and 1 (B), IPA can be recovered batchwise or continuously. Moreover, since IPA is volatile, it is preferable that the part which processes the to-be-processed water, mist, concentrated liquid, etc. which contain IPA of a collection | recovery apparatus be a closed system.

An IPA recovery method using the IPA recovery apparatus having the above configuration will be described below.
The method for recovering IPA according to the present invention can include the following steps.
(A) The ultrasonic atomization process which produces | generates mist from the to-be-processed water containing a basic impurity, an acid salt, and IPA.
Step (B) A mist condensation step for obtaining an IPA concentrate by condensation of mist.
Examples of the IPA-containing water containing basic impurities include drainage from various processes in which IPA used as a cleaning agent, a desiccant, a solvent, and the like is recovered. Among these, IPA-containing water discharged from the washing and drying process in the semiconductor manufacturing process can be mentioned.
The water to be treated which is subjected to ultrasonic atomization in the step (A) is IPA-containing water which is in a state containing a salt of basic impurities by adding an acid to IPA-containing water containing basic impurities.
The acid added to form the salt of the basic impurity in the IPA-containing water is not particularly limited as long as the target salt formation is possible, but the basic impurity such as sulfuric acid, nitric acid, hydrochloric acid, etc. has an affinity for water. An acid capable of forming a highly soluble salt can be mentioned. At least one of these acids can be used as an aqueous solution at a concentration suitable for salt formation.
For example, when sulfuric acid is added to IPA-containing water containing ammonia, ammonium sulfate or ammonium hydrogen sulfate is formed by reaction with ammonia, and is present in the IPA-containing water. Since ammonium sulfate and ammonium hydrogen sulfate have high affinity with water, the distribution of these salts to mist with high IPA concentration generated from the treated water by ultrasonic atomization is suppressed, and the IPA concentration is higher than the treated water. It is considered that a mist having a high ammonia concentration and a low ammonia concentration can be obtained.

The amount of acid added to the IPA-containing water containing basic impurities is preferably such that at least 90% by mass of the total amount of basic impurities is in a salt state with the added acid. From such a viewpoint, it is preferable to add an amount of acid that assumes that the total amount of basic impurities in the IPA-containing water is assumed to be a salt.
The acid addition step of adding the IPA-containing water acid containing basic impurities may be performed separately for the recovery method of the present invention, or may be incorporated in the previous stage of the step (A) as a step of the recovery method of the present invention. Good. In addition, you may utilize an ultrasonic atomization tank as a mixing area | region for acid addition.

In the recovery method of this invention, it can use suitably for IPA concentration of IPA containing water whose IPA density | concentration is 0.1-50 mass%. Moreover, the IPA containing water whose water content is 45 mass% or more can be made into a process target.
In addition, when the concentration of IPA containing IPA is less than 0.1% by mass, the acid concentration is set to 0.1% by mass or more by acid addition before the acid addition treatment. It can be used for preparation of water to be treated.
A basic impurity may be ammonia. The recovery method of the present invention can be suitably used for the treatment of IPA-containing water containing 1 mg / L to 100 mg / L of ammonia.
The frequency and output of the ultrasonic wave for performing the ultrasonic atomization are not particularly limited, and may be set so that the target mist can be generated.

In the ultrasonic atomization method, it is considered that the concentration of IPA contained in the concentrate is generally determined according to the IPA concentration of the liquid to be treated. For example, when the IPA concentration of the liquid to be treated is 20% by mass, the IPA concentration of the concentrated solution after concentration by the ultrasonic atomization method is about 50 to 80% by mass.
When it is desired to further increase the IPA concentration rate, for example, up to about 90% by mass, a multistage ultrasonic atomizer can be used.
The frequency of ultrasonic waves, the temperature of the ultrasonic atomization tank, the pressure of the gas phase, etc. in the step (A) are not particularly limited, and are set according to the IPA concentration of the water to be treated, the type and concentration of basic impurities, etc. can do. The frequency of the ultrasonic wave can be selected from the range of 15 kHz to 400 MHz.

A process (B) can be performed using various mist condensation means. As the mist condensing means, various condensing devices such as a condenser having a built-in cooling device can be used.
The transport of the mist from the step (A) to the step (B) can be performed, for example, by placing the mist on an airflow generated by an airflow generating means such as a blower pump.
Between the step (A) and the step (B), the mist obtained in the step (A) is converted into a small particle size mist having a higher IPA concentration than the water to be treated and a mist having a larger particle size than the small particle size mist. It is possible to add a classification step for classifying airflow. Various methods can be used as the airflow classification method used in the classification step. Among these, it is preferable to use a classification method using a cyclone classifier. It is possible to obtain an IPA concentrated solution in which the IPA concentration is further increased and the concentration of basic impurities is greatly reduced by classifying and separating a small particle size mist having a higher IPA concentration than the water to be treated and condensing it into a condensed liquid. it can.
In order to further increase the IPA concentration of the IPA concentrate thus obtained, a dehydration treatment step using a dehydration membrane can be performed on the IPA concentrate. By adding a dehydration treatment step, for example, the IPA content can be increased to about 99.9% by mass.
As the dehydration film, a dehydration film made of the above-described materials can be used.

  According to the recovery method of the present invention, the concentration of basic impurities in the IPA concentrate can be greatly reduced. For example, when the basic impurity is ammonia, the content of ammonia in the IPA concentrate can be reduced to less than 10 mg / L and lower than the water to be treated.

(Example 1)
1A includes a recovery tank 2, an acid aqueous solution supply system 4, an ultrasonic atomization tank 5, a liquid feed pump 3, a blower pump 9, a cyclone 6, a condenser 7, and a concentrated liquid recovery tank 8. Using a recovery device consisting of the above, the IPA wastewater containing ammonia was separated and concentrated. The IPA wastewater is supplied to the recovery tank 2, and the ammonia contained in the IPA wastewater is converted into (NH ₄ ) ₂ SO ₄ by adding H ₂ SO ₄ aqueous solution from the acid aqueous solution supply system 4. Used as treated water (after adding H ₂ SO ₄ aqueous solution) to be sent to the atomization tank 5. The IPA concentration of the water to be treated was 20.3% by mass, and the ammonia concentration (NH ₃ -N) was 60 mg / L. The pH of the water to be treated was 4.1.
The water to be treated (after addition of H ₂ SO ₄ aqueous solution) was sent to the ultrasonic atomization tank 5 by the liquid feed pump 3, and mist was generated by the ultrasonic vibration generated by the ultrasonic vibrator provided inside. . The generated mist is sent to the subsequent cyclone 6 by the blower pump 9, and the small particle size mist having a high IPA concentration is further cooled and recovered by the subsequent condenser 7, and sent to the concentrate recovery tank 8, where the water concentration is high. The particle size mist was separated by a cyclone 6 and returned to the collection tank 2.
The results are shown in Table 1. The IPA concentration in the concentrated liquid recovered in the concentrated liquid recovery tank 8 by the above processing is 76.3% by mass, the ammonia concentration (NH ₃ -N) <5 mg / L, the IPA is concentrated, and the ammonia is greatly reduced. Results were obtained. Moreover, when the sulfate ion of the IPA concentrate recovered in the concentrate recovery tank 8 was analyzed by ion chromatography, the sulfate ion concentration was <1 mg / L and was not mixed into the IPA concentration side.

(Comparative Example 1)
The IPA concentrated solution was obtained in the same manner as in Example 1 except that the same IPA wastewater containing ammonia as that used in Example 1 was used as it was (without adding H ₂ SO ₄ aqueous solution). Collected in tank 8.
The results are shown in Table 2.
When the H ₂ SO ₄ aqueous solution was not added, ammonia was greatly concentrated on the IPA concentration side.

DESCRIPTION OF SYMBOLS 1 Semiconductor manufacturing apparatus 2 Recovery tank 3 Liquid feed pump 4 Acid aqueous solution supply system 5 Ultrasonic atomization tank 6 Cyclone 7 Condensate 8 Concentrated liquid recovery tank 9 Blower pump 10 Dehydration film 11 Supply tank 12 Liquid feed pump

Claims (8)

An apparatus for recovering isopropyl alcohol from isopropyl alcohol-containing water containing basic impurities,
Acid addition means for adding an acid to the isopropyl alcohol-containing water;
Ultrasonic atomizing means for generating a mist of isopropyl alcohol-containing water to which the acid is added;
Mist condensing means for obtaining an isopropyl alcohol concentrate by condensation of the mist;
I have a,
The basic impurity is ammonia
Recovery apparatus isopropyl alcohol, characterized in that.   The recovery device according to claim 1, wherein the concentration of isopropyl alcohol in the water to be treated is 0.1 to 50 mass%. The recovery device according to claim 1 or 2 , wherein the ammonia concentration of the water to be treated is 1 mg / L to 100 mg / L. The recovery apparatus according to any one of claims 1 to 3 , wherein the acid is at least one of sulfuric acid, nitric acid, and hydrochloric acid. A method for recovering isopropyl alcohol from isopropyl alcohol-containing water containing basic impurities,
An acid addition step of adding an acid to the isopropyl alcohol-containing water;
An ultrasonic atomization step of generating a mist of isopropyl alcohol-containing water to which the acid is added;
A mist condensation step for obtaining an isopropyl alcohol concentrate by condensation of the mist;
I have a,
The basic impurity is ammonia
A method for recovering isopropyl alcohol. The recovery method according to claim 5 , wherein the concentration of isopropyl alcohol in water containing isopropyl alcohol containing basic impurities is 0.1 to 50 mass%. The recovery method according to claim 5 or 6 , wherein the ammonia concentration of the isopropyl alcohol-containing water containing the basic impurities is 1 mg / L to 100 mg / L. The recovery method according to claim 5 , wherein the acid is at least one of sulfuric acid, nitric acid, and hydrochloric acid.

Images