JPH0240220A - Pure water producing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application in Industry A] The present invention relates to a pure water production device that continuously produces pure water or so-called ultrapure water, which is widely used in semiconductor manufacturing factories, nuclear power plants, etc. Regarding.

[Prior Art] In the manufacture of LSIs and VLSIs, large amounts of pure water and ultrapure water are used. Ultrapure water is pure water having a specific resistance of 17 to 18 MΩ·cm, which is extremely close to the specific resistance of theoretically pure water (water consisting only of H2O), which is 1.8.24 MΩ·Cm.

Conventionally, an electrodialyzer (hereinafter referred to as rCDIJ) loaded with an ion exchange membrane and an ion exchange resin has been known as a pure water production device (Japanese Patent Application Laid-open No. 107906/1983). Effective deionization of a wide range of raw water is possible, from removal to purification of manufactured water by reverse osmosis.

The deionization effect of water by CDI will be explained with reference to FIG. 4.

In FIG. 4, the applied DC potentials are represented by (+) and (-). In FIG. 4, a concentration chamber 25a is formed between the anion exchange membrane 21 and the cation exchange membrane 22, and a dilution chamber 25a is formed between the cation exchange membrane 22 and the anion exchange membrane 23.
6 is formed. Further, a concentration chamber 25b is formed between the anion exchange membrane 23 and the cation exchange membrane 24. The dilution chamber 26 is filled with a mixed bed resin of a cation exchange resin 27 and an anion exchange resin 28 .

The ions in the raw water are represented by Na and CJ, and the ions that enter the dilution chamber 26 react with the ion exchange resins 2 and 28 based on their affinity, concentration, and mobility. It moves in the resin in the direction of
or 23 to maintain charge neutralization in all chambers. Due to the semi-permeable property of the membrane and the directionality of the potential gradient, ions in the solution decrease in the dilution chamber 26 and are concentrated in the adjacent concentration chambers 25a and 25b. For this reason, deionized water is recovered from the dilution chamber 26.

Unlike ion-exchange resins, CDI does not require regeneration, allows completely continuous water sampling, and has the excellent effect of producing extremely high-purity water.

However, in order to prevent the deterioration of the ion exchange membrane and ion exchange resin packed in CDI and the deterioration of processing efficiency,
It is necessary to control the quality of the raw water to be supplied to a certain level or higher, and it has the disadvantage that it is not easy to manage the quality of the raw water. For example, the C1- concentration in raw water is O,ippm
Hereinafter, the concentration of iron sulfide and manganese sulfide is required to be 1 ppm or less of O and O.

Conventionally, a reverse osmosis membrane separator (hereinafter abbreviated as rROJ) has generally been used as a pretreatment device for CDI.

[Problem to be solved by the invention] Water quality can be improved to some extent by treating the raw water supplied to the CDI with RO, but the conventional method
In the stage ROfi process, the removal of SiO2 from the raw water was not sufficient, and it was not possible to effectively prevent the deterioration of the CDI ion exchange membrane and ion exchange resin and the deterioration of the treated water.

It is an object of the present invention to solve the above-mentioned conventional problems and to provide a pure water production apparatus that can prevent deterioration of CDI's ion exchange membrane and ion exchange resin and obtain treated water of extremely high purity. do.

[Means for Solving the Problems] The pure water production apparatus of the present invention uses Ml for treating raw water with a reverse osmosis membrane.
a 1 m reverse osmosis membrane device, a second reverse osmosis membrane separator that performs reverse osmosis membrane treatment on the permeated water of the first reverse osmosis membrane separator, and a second reverse osmosis membrane an electrodialyzer for electrodialyzing water; the electrodialyzer is configured by alternately arranging a plurality of anion exchange membranes and cation exchange membranes to form concentration chambers and dilution chambers alternately; is characterized in that it is filled with a mixture of an anion exchange resin and a cation exchange resin.

[Function] When producing pure water with CDI, by performing two-stage ROIA burial using two RO units in series as a pretreatment of CDI, the water supplied to CDI is of extremely high quality, and the SiO2 concentration is particularly low. It is usually a very low value of 20 ppb or less.

Therefore, the ion exchange membrane and ion exchange resin of the CDI do not deteriorate, and it is possible to continuously collect highly purified treated water with a specific resistance of 10 MΩ-cm or more and 5i020 ppb or less, for example.

In general, the SiO2 concentration of the feed water (raw water) of the first stage RO (hereinafter abbreviated as "first RO") is higher than that of the second stage RO (hereinafter referred to as "first RO").
Since the 5LO2 concentration of the concentrated water in the RO of the second stage (hereinafter abbreviated as 2nd RO) is lower, the 5LO2 concentration of the 2nd R
The O enriched water can be returned to the first RO water supply, which allows the first RO treated water to have a lower 5LO2 value.

In addition, dissolved salts (T) containing 5102 in concentrated water of CDI
D S ) concentration is lower than the TDS concentration in the feed water of the second RO, so the CDI concentrated water is
It can be returned to the RO water supply, resulting in higher purity treated water.

Also, since concentrated water can be circulated in this way, water can be saved.

Furthermore, since it is not necessary to regenerate the ion exchange resin of CDI, waste liquid that requires IA burial is not generated, and processing costs can be kept low.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

Fig. 1 is a system diagram showing one embodiment of the pure water production apparatus of the present invention, Fig. 2 is a system diagram showing one embodiment of the CDI, and Fig. 3 is another embodiment of the pure water production apparatus of the present invention. FIG.

The pure water production apparatus shown in Fig. 1 includes a first reverse osmosis membrane separator (
1st RO) 1, a second reverse osmosis membrane separator (2nd RO) 2, and an electrodialyzer (CDI) 3 or 6, piping 11 that feeds raw water to the 1st ROI, permeation of the 1st R01 Piping 12 that supplies water to the 2nd RO2, Piping 13 that discharges the concentrated water of the 1st ROI to the outside of the system, Piping 14 that supplies the permeated water of the 2nd R02 to the CD 13 (this piping 14 is connected to the CDI, which will be described later). It branches into a water supply pipe 14a to the concentration chamber and a water supply pipe 14b to the dilution chamber.), 2nd RO2
Piping 15 that returns concentrated water to the upstream side of No. 1R01, CDl
A pipe 16 for taking out the treated water of No. 3, and a pipe 17 for returning the concentrated water of CDl3 to the upstream side of the first ROI or the second R02.

The procedure for treating raw water using the apparatus of the present invention will be described below.

As shown in FIG. 1, raw water such as city water, industrial water, well water, etc. is supplied to the first ROI through a pipe 11. 1st R0
In No. 1, it is preferable to operate at a relatively high recovery rate, for example, 50% or more, particularly about 80 to 90%, from the standpoint of effective utilization of raw water.

In the 1st R01, electrolytes and TOC components in the raw water are removed, but in the 1st R01, most of the electrolytes in the raw water are For example, N a Cf), 2
For a feed water of 00 mg/11, it is preferred to operate to remove more than 97% of the salt, especially more than 99%.

The permeated water of the 1st R01 is then transferred to the 2nd RO through the piping 12.
2. On the other hand, the concentrated water of No. 1R01 is connected to pipe 13.
is discharged out of the system.

In the second R02, the recovery rate is set to about 75 to 90% from the viewpoint of effective use of the treated water, and the concentrated water is returned to the raw water supply system of the first ROI through the pipe 15.

In the second R02, the electrolyte and TOC components in the water to be treated are further removed. In addition, in the second RO2, in order to reduce the load on the downstream CDl3 and obtain high-purity treated water, most of the electrolyte in the water to be treated (i.e., the raw water to the first Ro1), for example, Na CIL200 mg /
For JZ raw water, it is preferable to operate to remove 97% or more, particularly 99% or more of salt.

Due to this 2nd R02, most of the electrolytes in the raw water,
For example, about 99.5% of the water is desalted, and the permeate is usually s i O2? High purity water with a degree of 20 pPb or less can be obtained.

The permeated water of the second RO2 is of sufficiently high purity, but by further feeding it to the CDl3 through the pipe 14 for treatment,
It becomes possible to obtain ultrapure water with even higher purity.

Most of the electrolyte has already been removed from this second R02 permeated water, and the specific resistance value is, for example, about 1 to 2 MΩ·Cm. Therefore, the load on CDl3 is small, and a CDl3 regeneration operation, regeneration device, and waste liquid treatment equipment are unnecessary.

On the other hand, since the SiO2 concentration of the second R02 concentrated water is usually lower than the SiO2 concentration of the raw water and has a high purity, it is circulated from the pipe 15 to the upstream side of the first Rot.

Next, the processing in CDl3 will be explained with reference to FIG.

As shown in the figure, in the CDl3, a plurality of anion exchange membranes A and cation exchange membranes C are alternately arranged in parallel in a container 1, and a concentration chamber 31 and a dilution chamber 32 are alternately separated from each other. . The dilution chamber 32 is filled with a mixture 33 of an anion exchange resin and a cation exchange resin. 34 is one pole, and 35 is ten poles.

The permeated water of the 2nd R02 is branched from the pipe 14 to a water supply pipe 14a to the concentration chamber 31 of CDl3 and a water supply pipe 14b to the dilution chamber 32, respectively.
is supplied to

In the permeated water of No. 2R02 supplied to CDl3, cations such as Na10 pass through the cation exchange membrane C, and anions such as CJZ- pass through the anion exchange membrane A according to the principle explained in FIG. 4 above. They pass through and are concentrated in the concentration chambers 31, respectively. The treated water from which anions and cations have been removed in this way is discharged from the dilution chamber 32 via the pipe 16, subjected to post-treatment as required, and then sent to the course point.

On the other hand, the concentrated water in the concentration chamber 31 is discharged from the pipe 17,
It is circulated to the upstream side of the first R01 through the pipe 17g. This concentrated water has a sufficiently lower TDS concentration than the raw water supplied to the 1st R01, so it can be circulated to the 1st R01, resulting in the same raw water supply amount as in the case of conventional one-stage RO treatment. High purity water can be obtained. This CD
The concentrated water 13 may be returned to the upstream side of the second R02 through the pipe 1b.

In the pure water production apparatus of the present invention, a decarbonation tower may be provided before or after the first R01.

FIG. 3 is a system diagram showing an embodiment in which the decarboxylation tower 4 is connected between the first ROI and the second RO2 by pipes 12a and 12b. In FIG. 3, members having the same functions as those shown in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted.

By removing the dissolved gas in the permeated water of the 1st R01 using the decarbonation tower 4, the CO2 component with low removal performance by RO is removed to the maximum extent, increasing the purity of the treated water and reducing the membrane load of the 2nd R02. be done. From the viewpoint of efficient removal of CO2 components in the decarboxylation tower 4, it is particularly preferable to adjust the pH of the raw water to about 5 to 5.5.

In such a pure water production apparatus of the present invention, as the reverse osmosis membrane attached to the first RO or the second RO, ordinary commercially available membranes such as polyamide membranes, cellulose acetate membranes, aramid membranes, etc. can be used.

An experimental example will be explained below.

Experimental Example 1 (Example of the Present Invention) City water in Atsugi City, Kanagawa Prefecture was treated using the pure water production apparatus of the present invention shown in FIG.

As the first RO and the second RO, reverse osmosis separators each having a built-in spiral type 8-inch module using a crosslinked aramid composite membrane were arranged in two stages.

CDI also includes polypropylene resin anion exchange membranes and cation exchange membranes (approximately 0.5 rn" per membrane).
), 30 of each, arranged alternately as shown in Figure 2.
In the figure shown, only three dilution chambers are formed, but in this example, 30 dilution chambers were formed using 30 anion exchange membranes and 30 cation exchange membranes.)
, H-swelled acidic cation exchange resin and OH type strongly basic anion exchange resin mixed at a volume ratio of 40:60, approximately 3
Each dilution chamber was filled with .

The conditions for water flow through the CDI were as follows.

Processed water flow rate: 1.0 go/hr Concentrated water flow rate: 0.2rn”/hr Voltage: 100V Water temperature = 17℃ Table 1 shows the water quality at each site.

/ / / / / / Experimental Example 2 (Comparative Example) The treatment was carried out in the same manner as Experimental Example 1, except that the RO was used in one stage.

The results are shown in Table 2.

Table 2 From Tables 1 and 2, it is clear that the pure water production apparatus of the present invention can produce extremely high purity water.

[Effects of the Invention] As detailed above, the pure water production apparatus of the present invention can: (1) Stably and continuously sample water of extremely high purity.

■ Concentrated water from CDI can be circulated to RO, saving water.

■ No resin regeneration is required and therefore no wastewater discharges requiring treatment.

The following effects are achieved, and it becomes possible to efficiently produce extremely high-purity ultrapure water with a specific resistance of 10 MΩ·Cm or more and 5iO2 of 20 ppb or less.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing one embodiment of the pure water production apparatus of the present invention, Fig. 2 is a system diagram showing one embodiment of the CDI, and Fig. 3 is another embodiment of the pure water production apparatus of the present invention. FIG. 4 is a block diagram illustrating the principle of CDI. 1...1st RO12...2nd R0゜3...CDI
, 4...Decarboxylation tower.

Claims (1)

[Claims] (1) A first reverse osmosis membrane separator that processes raw water with a reverse osmosis membrane, a second reverse osmosis membrane separator that processes the permeated water of the first reverse osmosis membrane separator with a reverse osmosis membrane, and and an electrodialyzer that electrodialyzes the permeated water of the reverse osmosis membrane separator No. 2, and the electrodialyzer has a plurality of anion exchange membranes and cation exchange membranes arranged alternately to alternately serve as a concentration chamber and a dilution chamber. 1. A pure water producing apparatus characterized in that the dilution chamber is filled with a mixture of an anion exchange resin and a cation exchange resin.