JP2941121B2 - Ultrapure water production equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an apparatus for producing ultrapure water.

[0002]

2. Description of the Related Art Conventionally, for example, ultrapure water has been used as boiler water in nuclear power plants and thermal power plants, pharmaceutical manufacturing water, and various cleaning waters used in the semiconductor industry. For example, ultrapure water production equipment currently used in the semiconductor industry includes pretreatment, RO (reverse osmosis membrane), ion exchange,
Primary pure water system consisting of UV sterilization, vacuum degassing, etc., and UV oxidation equipment, ion exchange, UF (ultrafiltration) etc.
A system comprising a secondary water system and a recovery system comprising activated carbon, ion exchange, an ultraviolet oxidizer, activated carbon and the like is widely used.

However, the required water quality of ultrapure water for semiconductors has become increasingly severe in recent years. For ion exchange of the secondary pure water system, an ion exchange resin which has been subjected to special conditioning and regeneration outside is packed in the column. A cartridge polisher (hereinafter simply abbreviated as CP) that does not have a dedicated regeneration facility is used, and the above-mentioned long-term stable operation of the CP is indispensable for improving the water quality of the entire system of the ultrapure water production system. I have.

[0004]

The life of the CP and the quality of the treated water depend on the silica concentration of the inlet water of the CP. If the silica concentration at the inlet of the CP is high, treated water of stable water quality cannot be obtained. The life of the CP is also shortened. For this purpose, it has been found that it is important to reduce the silica concentration in the primary pure water system and reduce the silica load of the CP in the secondary pure water system.

Accordingly, the present inventors have made one
By installing a silica polisher in the next pure water system, in which a strong basic anion exchange resin is filled in the tower without gaps with a margin for the regeneration swelling of the resin and countercurrent regeneration is performed.
By reducing the silica concentration as much as possible in the secondary pure water system,
The present invention has been made possible by reducing the silica load of the CP of the next pure water system to obtain a more stable treatment for a long time than before.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an ion exchange type pure water production system with a margin in the column for regeneration swelling of the strong basic anion exchange resin. It is intended to provide an ultrapure water apparatus characterized by installing a packed silica polisher that performs countercurrent regeneration by filling without gaps, and further incorporates an ion exchange type pure water apparatus to relatively reduce raw water. A primary system for treating water quality close to ultrapure water and an ion exchange type cartridge polisher, which is used to further purify the treated water of the primary pure water system into ultrapure water and send it to the point of use An ultrapure water production apparatus comprising a secondary pure water system and a silica polisher for reducing the silica concentration of the treated water of the primary pure water system after the ion exchange pure water system in the primary pure water system. , Strong inside the tower An ultrapure water production apparatus characterized in that a packed type silica polisher for performing countercurrent regeneration is installed by filling a basic anion exchange resin with a margin for regeneration swelling of the resin without any gap and installing counter-current regeneration. It is.

[0007]

The present invention will be described below in detail by taking as an example the case where the present invention is applied to ultrapure water production in the semiconductor industry. 1 above
The silica polisher installed in the secondary pure water system must be sufficient to reduce the silica load of the CP incorporated in the secondary pure water system. Specifically, the primary pure water silica concentration is preferably 3 ppb or less. Has to be reduced from 1 ppb or less to 0, and it is difficult to achieve this object with the conventionally known co-current regeneration type silica polisher. The present invention reduces the silica concentration of the treated water of the primary pure water system to the low value as described above, and reduces the silica load of the CP of the secondary pure water system, thereby providing a more stable treated water for a long time than before. It is something that can be obtained.

In order to achieve the above object, in the present invention, the silica polisher installed in the primary pure water system is provided with a space between the strong basic anion exchange resin and the resin swelling of the resin so that the resin swells. A packed apparatus was used in which the resin was packed in the column and, at the time of regeneration, countercurrent regeneration was performed without performing backwashing of the resin which is usually performed in an ion exchange tower. By making the silica polisher into such a pack type, the regeneration efficiency of the silica polisher can be improved, and extremely high quality treated water having a silica concentration of 1 ppb or less can be obtained.

That is, the ion exchange tower has a cocurrent regeneration system in which the flow direction of the water to be treated at the time of water passage is the same as the flow direction of the regenerant during regeneration, and There is a countercurrent regeneration system in which the chemical is passed in the opposite direction to the flow direction of the treated water, but the countercurrent regeneration system is superior from the viewpoint of improving the regeneration efficiency and the quality of the treated water. In order to sufficiently exhibit such advantages of the countercurrent regeneration method, the ion exchange resin layer should not be disturbed as much as possible in the regeneration step at the end of the water supply as well as during the passage of the water to be treated. This is very important. However, in the conventional counter-current regeneration type ion exchange tower, since the suspended matter in the raw water is captured and accumulated in the resin tank by the flow of the raw water, the resin is always backwashed as the first stage of the regeneration process. ,
Since the operation of removing the turbidity in the column was performed, the ion exchange resin layer was remarkably disturbed, so that the above advantage of the countercurrent regeneration method was not sufficiently exhibited.

In order to eliminate such inconvenience, it is only necessary to pass the regenerant without performing the above-mentioned back washing in the regeneration step. However, in conventional ion exchange towers, it was common sense to carry out backwashing of the resin as the first stage of the regeneration process, so the tower above the resin layer contained
Usually, a considerably large space portion (hereinafter, referred to as a free board) substantially equal to the height of the resin layer is provided. However, when such a free board exists,
For example, in a counter-current regeneration system in which the water to be treated is passed in a downward flow and the regenerant is passed in an upward flow, the ion exchange resin is fluidized when the regenerant flows upward as it is. In order to prevent this, a special device on the device is required, and conversely, countercurrent regeneration is performed in which the water to be treated is passed through the upflow and the regenerant is passed through the downflow. In the system, there is a problem that the ion-exchange resin is easily fluidized when the water to be treated flows, and thus there is a possibility that high quality treated water may not be obtained.

The inventors of the present invention have conducted intensive studies on a method for efficiently regenerating silica polisher by the countercurrent regeneration method. A structure in which a strong basic anion exchange resin is filled without gaps with a margin only for the regenerated swelling of the resin (the swelling when it changes from Cl form to OH form). This led to the development of a silica polisher that did not do this.

That is, since the silica polisher in the present invention is installed after the ion-exchange type pure water apparatus as described above, the suspended matter in the water to be treated is mostly removed by the preceding pure water apparatus. Almost no turbidity is brought into the silica polisher, and therefore it is not necessary to perform a backwash for removing the turbidity in the regeneration step.

As a specific structure of the silica polisher, for example, a perforated plate attached with a cloth screen that allows water to pass through but does not pass ion-exchange resin is attached to the upper and lower portions in the tower, and the gap between these perforated plates is provided. The column is filled with a strong basic anion exchange resin with sufficient space for the regenerated swelling of the resin, with almost no gap, and the water to be treated is passed downflow into the column, and a sodium hydroxide solution or the like is used. Silica polisher may be configured to pass an alkaline regenerating agent in ascending flow, or may be configured to pass water to be treated in ascending flow and pass an alkaline regenerating agent in descending flow. In the silica polisher of such a structure, the strong basic anion exchange resin is filled in the tower with little clearance, though there is some margin, so that in the method of flowing the regenerant in an upward flow, the regeneration is performed. The resin layer can be easily pressed against the upper perforated plate by allowing the agent to flow in at a slightly higher flow rate than the normal flow rate. Since the speed is usually much higher than the flow rate of the regenerant, the resin layer can be easily pressed against the upper face plate in this case, and in each case, the strong basic anion exchange resin in the column flows. Will not be. Therefore, the advantage of the countercurrent regeneration system is maximized, the regeneration efficiency can be improved, and treated water having an extremely low silica content can be obtained.

As the primary pure water ion exchange type pure water apparatus, a conventionally known pure water apparatus having a regenerating facility can be used. For example, a cation exchange tower in which a strongly acidic cation exchange resin is filled in a tower, Similarly, a two-bed, three-column (2B3T) pure water apparatus comprising an anion exchange resin tower filled with a strongly basic anion exchange resin and a decarbonation tower, or a weakly acidic cation exchange resin and a strongly acidic cation in the tower A multi-layer bed consisting of a cation exchange tower filled with a stack of exchange resins, an anion tower filled with a stack of a weakly basic anion exchange resin and a strongly basic anion exchange resin in the tower, and a decarbonation tower A 2B3T pure water apparatus of the formula or a mixed-bed type pure water apparatus in which a strongly acidic cation exchange resin and a strongly basic anion exchange resin are mixed and filled in the same column can be used alone or in combination. .

When a type I strongly basic anion exchange resin is used as the filler resin of the silica polisher, the regeneration efficiency can be remarkably increased by regenerating the anion exchange resin at a high temperature and a high flow rate. That is, desorption of the silica adsorbed on the anion exchange resin is more efficient as the regeneration temperature is higher, but it is conventionally performed at 50 ° C. or lower due to the problem of heat resistance of the resin. However, in the regeneration of the anion exchange resin, if the contact time is shortened by passing the alkali regenerant at a higher flow rate than before, the regeneration can be performed at a temperature exceeding the conventional allowable temperature. In particular, when the anion exchange resin is type I, the regeneration can be carried out at a temperature of 55 to 65 ° C. This operation of regenerating the anion exchange resin in a high-temperature high-speed flow can also be applied to an anion exchange column of a 2B3T pure water apparatus.

Thus, according to the present invention, the above-mentioned packed silica polisher is specially provided for the primary pure water system, so that it is indispensable to carry out special conditioning and regeneration outside the secondary pure water system. Reduce the silica burden and C
In addition to enabling long-term safe operation of P and improving the water quality of the primary and secondary systems as a whole, the volume of the CP itself can be reduced, and a small design based on organic matter is possible. The apparatus of the present invention can be applied not only to the production of ultrapure water in the semiconductor industry as described above, but also to the treatment of water in raw and thermal power plants, particularly the treatment of make-up water for nuclear reactors and boilers.

[0017]

EXAMPLES Examples of the present invention and comparative examples are shown below.

The flow sheet of the embodiment is as follows.

The flow sheet of the comparative example is the same as that of the first embodiment except that the primary pure water-based PAC-AP and the mixed-bed polisher of the embodiment are not used. It is the same except that pure water PAC-AP is not used.

The specifications of the devices of the examples and comparative examples are as follows. 1. Raw water Na + K 23.5 mg CaCO ₃ / l HCO ₃ = 35.6 mg CaCO ₃ / l Ca 34.8 {SO ₄ = 15.0} Mg 23.2 {Cl = 15.0} ＮＯ NO ₃ = 4.8 〃 Total Cation = 81.5 〃 ───────────────── Salt constituent anion = 81.5 〃 CO ₂ = 14.3 〃 SiO ₂ = 15.7 〃 ───────────────── Total Anion = 111.5 〃

2. 2B3T of 2nd order pure water system (normal apparatus for backwashing ion exchange resin layer during regeneration) (common to Examples and Comparative Examples)

(Note) K tower: Amberlite (registered trademark)
A multi-bed type tower in which IRC-76 (weakly acidic cation exchange resin) and Amberlite IR-124 (strongly acidic cation exchange resin) are stacked and packed in the same tower. Tower A: Amberlite IRA-94S (weakly) A multi-layered tower in which basic anion exchange resin) and Amberlite IRA-400 (strongly basic anion exchange resin) are laminated.

3. Primary pure water mixed-bed polisher (with regeneration equipment) A strong acid cation exchange resin (IR-124) and a strongly basic anion exchange resin (IRA-400) are used at a ratio of 1: 1 (by volume). ).

4. CP (cartridge polisher) of secondary pure water system A resin obtained by mixing a strongly acidic cation exchange resin and a strongly basic anion exchange resin, which have been specially conditioned and regenerated outside (EG-EG manufactured by Organo Corporation). 4) packed in a column. Water flow speed is LV = 50m / H

5. PAC-AP (silica polisher) of primary water type (used in the case of the present invention) Type of resin: IRA-400 Resin vol .: 11 liter Layer height: 80 cm Margin height: 8 cm (Note) PAC-AP inlet water quality, ie, 2B3T outlet silica is 0.1 mg SiO ₂ / l (Note) Regeneration 100 g 100% NaOH / lR, 3% NaOH, L
V14m / h Ascending flow Water flow Downflow

(Example) In an ultrapure water system in which a PAC-AP was installed after the primary pure water system 2B3T shown in the above flow sheet, the operation was performed for 12 months in accordance with the above specifications. In addition, the silica concentration at the primary system outlet and the CP inlet is always maintained at 1 ppb or less, and the CP treated water
Maintained below 1 ppb for months.

Comparative Example In the above flow sheet, P
In a conventional system that does not use AC-AP and mixed-bed polisher, silica is 20 to 30 pp at the primary system outlet.
b, and in this case, as shown in FIG.
During the day, 5 ppb of treated water was obtained almost stably.
The silica concentration gradually increased after the day, and reached breakthrough in 120 days. In the conventional system not using only PAC-AP, the silica of the primary purified water is about 5 ppb. In this case, as shown in FIG. 2, the treated water of 1 ppb or less was obtained stably. At the end of the day, a breakthrough was reached.

(Note) Measurement of Silica Using a high-sensitivity silica analyzer SA-500 manufactured by Toray Engineering Co., Ltd. (color-absorption spectrophotometric method, concentrated ion chromatography) Quantitative lower limit of 0.2 ppb SiO ₂

[0029]

According to the apparatus of the present invention, the silica load of the CP of the secondary pure water system can be reduced, and the treated water more stable than before can be obtained for a long time. In the conventional apparatus, the CP must be replaced in six months. According to the present invention, the replacement life of this CP is extended to 12 months, and its industrial and economic value is great. Further, when the apparatus of the present invention is applied to, for example, the supply water treatment of a boiler in a power plant, it is possible to obtain makeup water having a significantly lower silica concentration than before, and to more reliably prevent the formation of silica scale in the boiler. can do.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between an inlet silica concentration and a treated water silica concentration of a secondary pure water type cartridge polisher (CP) in an example of the present invention.

FIG. 2 is a diagram showing a similar relationship in a comparative example.

FIG. 3 is a diagram showing a similar relationship in another comparative example.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-51-5272 (JP, A) JP-A-4-78483 (JP, A) JP-A-57-21093 (JP, U) 21556 (JP, B2) JP 55-41157 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C02F 1/42 B01J 47/02-47/08 B01J 49/00- 49/02

Claims (3)

(57) [Claims] 1. An ion-exchange type pure water production apparatus,
An ultrapure water production apparatus characterized in that a packed silica polisher for countercurrent regeneration is installed in the column with a space filled with a strongly basic anion exchange resin with a margin for the regenerated swelling of the resin without gaps. . 2. A primary pure water system incorporating an ion exchange type pure water system for treating raw water to a water quality relatively close to ultrapure water, and a primary pure water system incorporating an ion exchange type cartridge polisher. In an ultrapure water production system having a secondary pure water system for further purifying the treated water into ultrapure water and sending it to a point of use, the ion exchange type pure water system is installed in the primary pure water system following the ion exchange pure water system. A silica polisher for reducing the silica concentration of treated water in a primary pure water system, in which a strong basic anion exchange resin is filled in a tower without gaps with an allowance for regeneration swelling of the resin, and a countercurrent flow An ultra-pure water production apparatus capable of long-term stable operation, wherein a packed silica polisher for regeneration is installed. 3. The ultrapure water production apparatus according to claim 1, wherein the anion exchange resin of the packed silica polisher is regenerated at a high temperature and a high flow rate.