JP6907514B2 - Ultrapure water production system and ultrapure water production method - Google Patents

Description

The present invention relates to an ultrapure water production system capable of efficiently reducing boron existing in water to be treated, and an ultrapure water production method using the same.

Conventionally, in the field of manufacturing electronic devices such as semiconductors and liquid crystal panels, ultrapure water having an extremely small content of impurities such as organic substances, fine particles, and ionic substances has been used for cleaning the system. Above all, in the semiconductor manufacturing process, the ultrapure water used is required to have extremely high purity as the semiconductor becomes finer and has a larger capacity.

Such ultrapure water used in the semiconductor manufacturing process is mainly manufactured in an ultrapure water manufacturing system including a pretreatment system, a primary pure water system, and a secondary pure water system, and is supplied to use points. NS. The pretreatment system is for decontaminating raw water using a decontamination treatment device using coagulation filtration, microfiltration membrane (MF membrane), ultrafiltration membrane (UF membrane), etc., or a dechlorination treatment device using activated carbon, etc. be. The primary pure water system is for removing impurities such as ion components and TOC components contained in pretreated water by a two-bed, three-tower ion exchange device, a reverse osmosis membrane (RO membrane) device, and the like. The secondary pure water system is also called a subsystem, and is provided in the primary pure water by an ultraviolet oxidizing device (UV device), a mixed bed ion exchange device, a membrane degassing device, an ultrafiltration membrane device (UF device), etc. This is for producing ultrapure water having higher purity by removing impurities such as extremely small amounts of fine particles and minute amounts of ions, particularly low-molecular-weight trace organic substances. In such an ultrapure water production system, a water supply pipe that circulates ultrapure water from the subsystem to the use point and a return pipe for returning and circulating ultrapure water that was not used at the use point to the tip of the subsystem. It is common to have and.

In recent years, adverse effects of ions contained in ultrapure water, especially boron, on semiconductor products have become a problem, and reducing the concentration of boron in ultrapure water has become an important issue. If the water to be treated (primary pure water) supplied to the subsystem contains a large amount of ionic components and TOC components, the ion exchange resin of the mixed-bed ion exchange device that constitutes the subsystem is frequently regenerated. This is not preferable because it leads to an increase in the cost of the entire ultrapure water production system. Therefore, most of the ionic components and TOC components contained in the water to be treated are usually removed in the primary pure water system.

Boron contained in the water to be treated can also be removed by a general ion exchange resin (for example, a strong basic anion exchange resin). However, since boron exists as an extremely weak boric acid in an aqueous solution, its ion exchange capacity is smaller than that of silica (silicic acid) and other anions, and it breaks through the ion exchange resin relatively early and enters the treated water. It leaks. Therefore, if it is attempted to reduce boron to the concentration required for ultrapure water using such a general ion exchange resin, frequent regeneration of the ion exchange resin is required, and the cost of chemicals for regeneration is high. Will take.

In order to prevent the cost increase due to the regenerated chemicals of the so-called regenerative ion exchange device as described above, for example, Patent Document 1 describes an anion exchange resin in an ultrapure water production device not provided with the regenerative ion exchange device. A method using a boron-selective ion exchange resin having a larger ion exchange capacity than that in Patent Document 2 is a method using an organic porous body having a boron selective adsorption capacity, and Patent Document 3 is a method using a boron-selective removable ion. Methods using exchange fibers have been proposed respectively. However, in the method described in Patent Document 1-3, in addition to the need for additional equipment, the water to be treated containing the TOC component eluted from the member is supplied to the subsequent subsystem, so that the sub There is a problem that it is necessary to reduce the TOC component to the level required for ultrapure water in the system, which leads to an increase in the cost of the entire ultrapure water production system.

Boron contained in the water to be treated can also be removed by a general reverse osmosis membrane (RO membrane). However, as described above, since boric acid in the aqueous solution is an extremely weak acid, only a small part of it is dissociated, and most of it exists in the form of _{H 3} BO _4. Therefore, the removal rate of boron by the RO membrane is extremely low, and if it is attempted to reduce the boron to the concentration required for ultrapure water, the RO membrane apparatus itself becomes heavy, which is not realistic in terms of cost.

In order to increase the removal rate of boron by the RO membrane as described above, for example, in Patent Document 4, the pH of the water to be treated introduced into the RO apparatus is made alkaline and the weak ion component of boron is ionized. A method of removing ionized boron with an RO device has been proposed. However, in the method described in Patent Document 4, in addition to requiring equipment for adding chemicals to make the pH of the water to be treated introduced into the RO apparatus alkaline, an increase in the amount of chemicals used directly increases the cost. There is a problem that leads to. Further, when the pH is set to a high value, hardness components (Ca, Mg, etc.) in water may precipitate as hydroxides, which may clog the RO film.

Japanese Unexamined Patent Publication No. 9-192661 Japanese Unexamined Patent Publication No. 2004-066153 Japanese Unexamined Patent Publication No. 2005-246126 Japanese Unexamined Patent Publication No. 2004-283710

The present invention has been made based on the above circumstances, and a TOC load is applied to the subsystem by supplying water to be treated after reducing boron and TOC components in the primary pure water system to the subsystem. It is an object of the present invention to provide an ultrapure water production system and an ultrapure water production method capable of stably obtaining ultrapure water having a low concentration of boron.

In order to solve the above problems, firstly, the present invention is an ultrapure water production system including a pretreatment system, a primary pure water system and a secondary pure water system in this order, wherein the primary pure water system is provided. An ion exchange device for treating water to be treated containing boron with an ion exchange resin is provided, and the ion exchange device is used to supply an accommodating portion for filling the ion exchange resin and water to be treated to the accommodating portion. It has a supply unit and a discharge unit for discharging treated water from the storage unit. The storage unit has a boron-selective ion exchange resin on the supply unit side and a boron-selective ion on the discharge unit side. Provided is an ultrapure water production system filled with ion exchange resins other than exchange resins (Invention 1).

According to the present invention (Invention 1), in the ion exchange device provided in the primary pure water system, a boron-selective ion exchange resin is on the supply part side of the accommodating part, and an ion exchange other than the boron-selective ion exchange resin is on the discharge part side. By filling the resin, boron is first adsorbed and removed from the supplied water to be treated containing boron by a boron-selective ion exchange resin, and then boron-selective ions are removed by an ion exchange resin other than the boron-selective ion exchange resin. Since the TOC component eluted from the exchange resin is adsorbed and removed, it is possible to supply the primary treated water having a reduced boron concentration without imposing a TOC load on the subsequent subsystem. As a result, ultrapure water having a low concentration of boron can be stably obtained. In addition, it is possible to reduce the processing cost due to the increase in the TOC load in the subsystem.

In the above invention (Invention 1), the accommodating portion is erected, the supply portion is arranged on the upper side of the accommodating portion, and the discharging portion is arranged on the lower side of the accommodating portion. Preferred (Invention 2).

According to the present invention (Invention 2), the water to be treated can be supplied from the supply part to the storage part filled with the ion exchange resin so that the flow direction is from the upper side to the lower side of the storage part. Can be efficiently brought into contact with the ion exchange resin, and the adsorption capacity of each ion exchange resin is highly exhibited. Therefore, the TOC component eluted from boron and the boron-selective ion exchange resin contained in the water to be treated can be effectively removed.

In the above inventions (Inventions 1 and 2), it is preferable that the ion exchange resin has a structure in which the boron-selective ion exchange resin and an ion exchange resin other than the boron-selective ion exchange resin are laminated (Invention 3). ).

According to the present invention (Invention 3), the ion exchange resin has a two-layer structure of a boron-selective ion exchange resin and an ion exchange resin other than the boron-selective ion exchange resin, so that each of the above ion exchange resins is adsorbed. Since the efficiency can be easily predicted, the treatment with an ion exchange resin can be performed efficiently.

In the above invention (Invention 1-3), it is preferable that the ion exchange device is provided at the end of the primary pure water system (Invention 4).

In general, in order to maximize the adsorption capacity of the boron-selective ion exchange resin, it is preferable that the load of the supplied water to be treated is only boron. According to the present invention (Invention 4), an ion exchange device having a boron-selective ion exchange resin is provided at the end of the primary pure water system to exchange the water to be treated with a reduced load other than boron. Since it can be supplied to the apparatus, the adsorption capacity of the boron-selective ion exchange resin can be maximized, and the boron removal efficiency can be improved.

In the above invention (Invention 1-4), the ion exchange resin other than the boron-selective ion exchange resin is selected from a strong basic anion exchange resin, a mixture of an anion exchange resin and a cation exchange resin, and an amphoteric ion exchange resin. It is preferably at least one of the above (Invention 5).

According to the present invention (Invention 5), the TOC component eluted from the boron-selective ion exchange resin can be more efficiently adsorbed and removed.

Secondly, the present invention provides an ultrapure water production method using the ultrapure water production system (Invention 6).

According to the ultrapure water production system and the ultrapure water production method of the present invention, water to be treated after reducing boron and TOC components in the primary pure water system is supplied to the subsystem (secondary pure water system). , Ultrapure water with a low concentration of boron can be stably obtained without applying a TOC load to the subsystem.

It is a block diagram which shows the ultrapure water production system which concerns on one Embodiment of this invention. It is the schematic which shows the ion exchange apparatus which has the boron selective ion exchange resin provided in the ultrapure water production system which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the ultrapure water production system and the ultrapure water production method of the present invention will be described with reference to the drawings as appropriate. The embodiments described below are for facilitating the understanding of the present invention and do not limit the present invention in any way.

(Ultrapure water)
The ultrapure water produced in this embodiment preferably has a boron concentration of between 0.5 ppt and 50 ppt. If the boron concentration is out of the above range, it may adversely affect the semiconductor product when cleaning the system in the manufacturing process of the semiconductor product, which is not preferable.

(Water to be treated)
The boron-containing water to be treated used in the present embodiment is not particularly limited. Usually, the water to be treated (pre-treated water) after the turbidity treatment by the pretreatment system, that is, the water to be treated supplied to the primary treatment system contains about 30 ppb of boron. Boron is mainly present in the form of boric acid (B (OH) _{3) in the water to be treated.}

[Ultrapure water production system]
FIG. 1 is a block diagram showing an ultrapure water production system according to an embodiment of the present invention. The ultrapure water production system 1 shown in FIG. 1 includes a pretreatment system 2, a primary pure water system 3, and a secondary pure water system (subsystem) 4 in this order. The raw water supplied to the pretreatment system 2 is turbidized by coagulation filtration, MF membrane (microfiltration membrane), UF membrane (ultrafiltration membrane), etc., dechlorinated by activated carbon, etc., and then passed through the water supply pipe L1. , Is supplied to the primary pure water system 3. The pretreated water supplied to the primary pure water system 3 is supplied to the subsystem 4 via the water supply pipe L2 after impurities such as ionic components and TOC components are removed. In the subsystem 4, trace amounts of fine particles and trace ion components in the water to be treated, particularly impurities such as low molecular weight trace organic substances, are removed, and ultrapure water having higher purity is produced. The ultrapure water produced in the subsystem 4 is sent to the use point 5 via the water supply pipe L3.

<Primary pure water system>
The primary pure water system 3 includes a two-bed, three-tower type ion exchange device (first ion exchange device) 31, a reverse osmosis membrane (RO membrane) device 32, and a mixed-bed type ion exchange device (second ion exchange device) 33. , An ion exchange device (third ion exchange device) 34 having a boron-selective ion exchange resin is provided in this order. The first ion exchange device 31 includes a cation exchange tower (H tower), a decarbonization tower, and an anion exchange tower (OH tower) in this order, and is for desalting the water to be treated supplied from the pretreatment system 2. Is. The reverse osmosis membrane (RO membrane) device 32 is for removing impurities such as ionic components and TOC components in the water to be treated. Water to be treated with a reduced salt concentration is supplied to the reverse osmosis membrane (RO membrane) apparatus 32 by the desalting treatment by the first ion exchange apparatus 31, so that the water in the reverse osmosis membrane (RO membrane) apparatus 32 The recovery rate is improved, and the removal rate of impurities such as ionic components and TOC components contained in the water to be treated is also improved accordingly. The second ion exchange device 33 includes a tower in which an anion exchange resin and a cation exchange resin are uniformly mixed and filled, in order to remove low molecular weight cations and anions existing in the water to be treated and to increase the purity of the treated water. belongs to.

The mixed bed type ion exchange device provided in the primary pure water system may be either a regenerative type or a non-renewable type, but a non-regenerative type ion exchange device is preferable. This is because when a regenerative ion exchange device is used in the primary pure water system, not only the cost increases depending on the chemicals used when regenerating the ion exchange resin, but also the chemicals required for regenerating the ion exchange resin. This is because the amount of wastewater tends to increase. Normally, when a non-regenerative ion exchange device is used in the primary pure water system, the removal rate of ion components is improved by using it in combination with a reverse osmosis membrane (RO membrane) device or the like as in the present embodiment. Is being done.

(Ion exchange device with boron selective ion exchange resin)
Next, an ion exchange device (third ion exchange device) 34 having a boron-selective ion exchange resin provided in the primary pure water system 3 of the present embodiment will be described in detail with reference to FIG.

The third ion exchange device 34 removes boron contained in the water to be treated with a boron-selective ion exchange resin, and removes the TOC component eluted from the boron-selective ion exchange resin into an ion exchange resin other than the boron-selective ion exchange resin. Is for removal by. In order to maximize the adsorption capacity of the boron-selective ion exchange resin, it is desirable that the load of the water to be treated supplied to the third ion exchange device 34 is only boron, so that the third ion exchange device 34 is installed at the end of the primary pure water system 3. Further, the ultraviolet oxidizing device (UV device) 41 installed at the tip of the subsequent subsystem 4 is required to be as small as possible because the device itself is large and bulky and expensive. To this end, the UV oxidizing device (UV device) installed at the tip of the subsystem 4 is installed at the tip of the subsystem 4 by removing the TOC component in the water to be treated as much as possible in the third ion exchange device 34 installed at the end of the primary pure water system 3. ) 41 should not be loaded with TOC.

FIG. 2 is a schematic view showing the configuration of the third ion exchange device 34 according to the present embodiment. The third ion exchange device 34 has an accommodating portion 341 for filling the ion exchange resin A, a supply unit 342 for supplying the water to be treated to the accommodating unit 341, and a third ion exchange device 34 for discharging the treated water from the accommodating unit 341. It has a discharge unit 343. The accommodating unit 341 is erected, a supply unit 342 is arranged above the accommodating unit 341, and a discharge unit 343 is arranged below the accommodating unit 341, and the boron selective ion exchange resin A1 is provided as a supply unit. On the 342 side, an ion exchange resin A2 other than the boron-selective ion exchange resin is filled on the discharge portion 343 side, respectively.

In the third ion exchange device 34, the supply section 342 is filled with the boron-selective ion exchange resin A1, and the discharge section 343 is filled with the ion exchange resin A2 other than the boron-selective ion exchange resin. Boron is first adsorbed and removed by the boron-selective ion exchange resin A1 from the water to be treated containing boron supplied to 341, and then from the boron-selective ion exchange resin A1 by an ion exchange resin A2 other than the boron-selective ion exchange resin. Since the eluted TOC component is adsorbed and removed, it is possible to supply the primary treated water having a reduced boron concentration without applying a TOC load to the subsystem 4 in the subsequent stage. By suppressing the TOC load on the subsystem 4, it is possible to prevent an increase in the cost of the entire ultrapure water production system.

Further, the accommodating unit 341 is erected, and the supply unit 342 is arranged on the upper side thereof and the discharge unit 343 is arranged on the lower side so that the flow direction is from the upper side to the lower side of the accommodating unit 341. Since the water to be treated can be supplied from the part 342, the ion exchange resin A is less likely to be agitated by the water to be treated, and the boron-selective ion exchange resin A1 and the ion exchange resin A2 other than the boron-selective ion exchange resin are used. The layered structure is maintained. As a result, the water to be treated and the ion exchange resins A1 and A2 can be efficiently brought into contact with each other, so that the adsorption capacity of the ion exchange resins A1 and A2 is highly exhibited. Therefore, boron and the TOC component eluted from the boron-selective ion exchange resin A1 contained in the water to be treated can be effectively removed.

The ion exchange resin A filled in the accommodating portion 341 may have a structure in which a boron selective ion exchange resin A1 and an ion exchange resin A2 other than the boron selective ion exchange resin are laminated. Since the ion exchange resin A has the above-mentioned two-layer structure, it becomes easy to predict the adsorption efficiency of each of the above ion exchange resins A1 and A2, so that the treatment can be performed efficiently.

The accommodating portion 341 may have a partition plate inside for partitioning the boron-selective ion exchange resin A1 and the ion exchange resin A2 other than the boron-selective ion exchange resin. By having such a partition plate, it is possible to prevent the ion exchange resins A1 and A2 from being mixed or flowing out vertically. Further, the accommodating portion 341 includes, for example, a sub accommodating portion 3411 (not shown) filled with the boron selective ion exchange resin A1 and a sub accommodating portion 3412 filled with an ion exchange resin A2 other than the boron selective ion exchange resin. (Not shown) may have a structure connected in series.

The layer height of the boron-selective ion exchange resin A1 is not particularly limited and can be appropriately set as needed, but it is preferably set to 800 mm or more, and it is preferable to set it to 1000 mm or more. More preferred. By setting the layer height to 800 mm or more, the adsorption efficiency of the boron-selective ion exchange resin A1 is improved. The layer height of the ion exchange resin A2 other than the boron-selective ion exchange resin is not particularly limited and can be appropriately set as needed, but it is preferably set to 100 mm or more, preferably 500 mm or more. It is more preferable to set so as to be. By setting the layer height to 100 mm or more, the adsorption efficiency of the ion exchange resin A2 other than the boron selective ion exchange resin is improved.

(Boron selective ion exchange resin)
The boron-selective ion exchange resin A1 is not particularly limited as long as it has an N-methylglucamine group having boron selectivity as a functional group instead of the ion exchange group in the anion exchange resin (chelate resin). However, the introduction rate of the chelate group having boron selectivity into the anion exchange resin does not reach 100%, and the adsorption rate may decrease due to the adsorption of other ions on the remaining anion group. obtain. Therefore, in order to prevent such a situation, the boron-selective ion exchange resin A1 has less elution of TOC components such as a chelate resin used for producing ultrapure water and a chelate resin washed with ultrapure water. It is preferable that the TOC concentration does not increase as much as possible before and after water flow. As such a chelate resin, one having an N-methylglucamine group is preferable, and for example, CRB03 manufactured by Mitsubishi Chemical Corporation can be used.

(Ion exchange resins other than boron selective ion exchange resins)
The ion exchange resin A2 other than the boron-selective ion exchange resin is not particularly limited, but the elution of TOC components such as the ion exchange resin used for producing ultrapure water and the ion exchange resin washed with ultrapure water is small. The amount of increase in TOC concentration (ΔTOC) before and after water flow is preferably about <1-3 ppb. The ion exchange resin is preferably at least one selected from a strong basic anion exchange resin, a mixture of an anion exchange resin and a cation exchange resin, and an amphoteric ion exchange resin, and more preferably strong. It is a basic anion exchange resin, and for example, SAT10L manufactured by Mitsubishi Chemical Corporation can be used.

<Subsystem>
The subsystem 4 includes an ultraviolet oxidizing device (UV device) 41, a membrane degassing device 42, a mixed bed ion exchange device 43, and an ultrafiltration membrane device (UF device) 44 in this order. The ultraviolet oxidizing device (UV device) 41 is for oxidatively decomposing the TOC component remaining in the water to be treated by the oxidation treatment by ultraviolet irradiation. The membrane deaerator 42 is for reducing the amount of dissolved oxygen in the treated water. The mixed bed type ion exchange device 43 is for removing ionized components from the oxidatively decomposed TOC components in the treated water to increase the purity of the treated water. The ultrafiltration membrane device (UF device) 44 is for removing fine particles and the like of the ion exchange resin flowing out from the mixed bed type ion exchange device 43.

In a general ultrapure water production system, there is a considerable difference in scale between the primary pure water system and the subsystem, and the primary pure water system is larger. Also in this embodiment, each device included in the primary pure water system 3 is larger in scale than each device provided in the subsystem 4, and for example, a third ion exchange device 34 provided at the end of the primary pure water system 3 is provided. , It is not common to provide it at the tip of a subsystem 4 of different scale. Similarly, it is not common to provide the ultraviolet oxidizing device (UV device) 41 provided at the tip of the subsystem 4 at the end of the primary pure water system 3 having a different scale.

[Ultrapure water production method]
Next, a method for producing ultrapure water using the ultrapure water production system 1 of the present embodiment as described above will be described.

The raw water supplied to the pretreatment system 2 is subjected to coagulation filtration, turbidity treatment with MF membrane (microfiltration membrane), UF membrane (ultrafiltration membrane), etc., and dechlorination treatment with activated carbon (pretreatment step). It is supplied to the primary pure water system 3 via the water supply pipe L1. The pretreated water supplied to the primary pure water system 3 is supplied to the subsystem 4 via the water supply pipe L2 after the removal treatment of impurities such as ionic components and TOC components (primary pure water production step). The primary pure water supplied to the subsystem 4 removes impurities such as trace amounts of fine particles and trace ion components, especially low-molecular-weight trace organic substances, to produce ultrapure water with higher purity (2). Next pure water production process). The ultrapure water produced in the subsystem 4 is sent to the use point 5 via the water supply pipe L3.

(Processing process by an ion exchange device having a boron-selective ion exchange resin)
Next, the treatment step by the ion exchange device (third ion exchange device) 34 having the boron-selective ion exchange resin provided in the primary pure water system 3 of the present embodiment will be described in detail with reference to FIG.

First, the water to be treated is supplied from the supply unit 342 to the storage unit 341 so that the flow direction is from the upper side to the lower side of the storage unit 341. The accommodating unit 341 is erected, the supply unit 342 is arranged on the upper side thereof, and the discharge unit 343 is arranged on the lower side, and the boron selective ion exchange resin A1 is arranged on the supply unit 342 side for boron selective ion exchange. An ion exchange resin A2 other than the resin is filled on the discharge portion 343 side. The water to be treated supplied to the accommodating portion 341 is first adsorbed and removed by the boron-selective ion exchange resin A1, and then the boron-selective ion exchange resin A1 is used by the ion exchange resin A2 other than the boron-selective ion exchange resin. The TOC component eluted from the is adsorbed and removed. The water to be treated (primary treated water) from which boron and TOC components have been removed is discharged from the discharge unit 343 and transferred to the next step.

As described above, the accommodation unit 341 is filled with the boron-selective ion exchange resin A1 on the supply unit 342 side and the ion exchange resin A2 other than the boron-selective ion exchange resin on the discharge unit 343 side. From the supplied water to be treated containing boron, boron is first adsorbed and removed by the boron-selective ion exchange resin A1, and then the TOC is eluted from the boron-selective ion exchange resin by an ion exchange resin A2 other than the boron-selective ion exchange resin. Since the components are adsorbed and removed, it is possible to supply the primary treated water having a reduced boron concentration without imposing a TOC load on the subsystem 4 in the subsequent stage. By suppressing the TOC load on the subsystem 4, it is possible to prevent an increase in the cost of the entire ultrapure water production system.

In the ultrapure water production method of the present embodiment, the flow speed of the water to be treated to the third ion exchange device 34 is not particularly limited, but the space speed (SV) is in the range of 30 / h-180 / h. Is preferable, and 60 / h is more preferable. If the passing speed of the water to be treated is less than 30 / h, the treatment speed by the third ion exchange device 34 becomes slow, which is not efficient. Further, when the water flow rate of the water to be treated exceeds 180 / h, the treatment by the third ion exchange device 34 becomes insufficient, and it becomes difficult to sufficiently remove boron in the water to be treated.

According to the ultrapure water production method using the ultrapure water production system 1 of the present embodiment, the water to be treated after reducing boron and TOC components in the primary pure water system 3 is a subsystem (secondary pure water system). By supplying to No. 4, ultrapure water having a low concentration of boron can be stably obtained without applying a TOC load to the subsystem 4.

The above-mentioned ultrapure water production method is a method for producing ultrapure water in which a pretreatment step, a primary pure water production step, and a secondary pure water production step are provided in this order, and the primary pure water production step is boron. A step of treating the water to be treated containing the above with an ion exchange resin is provided, and the treatment step of this ion exchange resin brings the water to be treated containing boron and the boron selective ion exchange resin into contact with each other to remove boron from the water to be treated. The TOC component is removed from the water to be treated after the first separation step by bringing the water to be treated after the first separation step into contact with an ion exchange resin other than the boron-selective ion exchange resin. It can also be regarded as an ultrapure water production method having a second separation step of separation.

Although the present invention has been described above with reference to the drawings, the present invention is not limited to the above embodiment, and various modifications can be made.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the following Examples.

[Example 1]
The water to be treated was treated using the third ion exchange device 34 shown in FIG. A cylindrical acrylic column having a diameter of 40 mm (hereinafter, simply referred to as an "acrylic column") is used as the accommodating portion 341, and a strong base manufactured by Mitsubishi Chemical Corporation is used on the acrylic column so that the layer height is 100 mm. A sex anion exchange resin was filled, and a boron-selective ion exchange resin manufactured by Mitsubishi Chemical Corporation was filled on the upper side thereof so that the layer height was 800 mm. Here, water to be treated having a boron concentration of 0.8 ppb, a specific resistance of 18.2 MΩ · cm, and a TOC component of 0.5 ppb is passed at 60 / h (SV) so that the flow direction is downward, and the treatment is performed. rice field. The boron concentration (ppt) and TOC concentration (ppb) of the obtained treated water were measured.

[Comparative Example 1]
The treatment was carried out under the same conditions as in Example 1 except that the acrylic column was filled with only a boron-selective ion exchange resin manufactured by Mitsubishi Chemical Corporation so that the layer height was 800 mm. The boron concentration (ppt) and TOC concentration (ppb) of the obtained treated water were measured.

[Comparative Example 2]
The treatment was carried out under the same conditions as in Example 1 except that the acrylic column was filled with only a strong basic anion exchange resin manufactured by Mitsubishi Chemical Corporation so that the layer height was 800 mm. The boron concentration (ppt) and TOC concentration (ppb) of the obtained treated water were measured.

[result]
Table 1 shows the changes over time in the boron concentration (ppt) and TOC concentration (ppb) of the treated water. As can be seen from this result, in Example 1, the boron concentration of the treated water could be maintained at a satisfactory level for 24 hours, and the TOC concentration could also be maintained without a significant increase.

In Comparative Example 1, the boron concentration of the treated water could be maintained at a satisfactory level for 24 hours, but the TOC concentration increased significantly in 1 hour, and no significant decrease was observed even at 24 hours. This is because the TOC component was eluted from the boron-selective ion exchange resin. The treated water (primary treated water) of Comparative Example 1 is supplied to the subsystem 4 and treated at a water flow rate of 60 / h (SV) to stably supply treated water having a TOC concentration of 1.0 ppb or less. As a result of making a trial calculation in the case of obtaining it, it was found that a cost equivalent to 10% of the cost of the entire subsystem 4 is required as compared with the case of the first embodiment.

In Comparative Example 2, the boron concentration of the treated water could not be maintained at a satisfactory level for 24 hours due to the low ion exchange capacity, but the TOC concentration did not increase significantly.

As described above, according to the ultrapure water production system and the ultrapure water production method of the present invention, the water to be treated after reducing boron and TOC components in the primary pure water system is a subsystem (secondary pure water system). ), It is possible to stably obtain ultrapure water having a low concentration of boron without imposing a TOC load on the subsystem.

The present invention is useful as an ultrapure water production system and an ultrapure water production method for stably obtaining ultrapure water having a low concentration of boron.

1 ... Ultrapure water production system 2 ... Pretreatment system 3 ... Primary pure water system 31 ... Two-bed, three-tower ion exchange device (first ion exchange device)
32 ... Reverse osmosis membrane (RO membrane) device 33 ... Mixed bed type ion exchange device (second ion exchange device)
34 ... Ion exchange device having a boron-selective ion exchange resin (third ion exchange device)
341 ... Containment section 342 ... Supply section 343 ... Discharge section 4 ... Secondary pure water system (subsystem)
41 ... Ultraviolet oxidizing device (UV device)
42 ... Membrane-type degassing device 43 ... Mixed-bed ion exchange device 44 ... Ultrafiltration membrane device (UF device)
5 ... Use points L1, L2, L3 ... Water supply pipe R1 ... Return pipe A ... Ion exchange resin A1 ... Boron selective ion exchange resin A2 ... Ion exchange resin other than boron selective ion exchange resin

Claims (5)

An ultrapure water production system that includes a pretreatment system, a primary pure water system, and a secondary pure water system in this order.
The primary pure water system includes a first ion exchange device, a reverse osmosis membrane device, a second ion exchange device, and a third ion exchange device in this order.
The second ion exchange device is a non-regenerative mixed bed type ion exchange device.
The third ion exchange device is a non-regenerative ion exchange device that treats water to be treated containing boron with an ion exchange resin , and the third ion exchange device is provided at the end of the primary pure water system. ,
The third ion exchange device
An accommodating part for filling the ion exchange resin,
A supply unit for supplying water to be treated to the storage unit,
It has a discharge part for discharging treated water from the storage part, and has a discharge part.
The accommodating portion is filled with a boron-selective ion exchange resin on the supply portion side and an ion exchange resin other than the boron-selective ion exchange resin on the discharge portion side.
An ultrapure water production system in which an ion exchange resin other than the boron-selective ion exchange resin is a strong basic anion exchange resin. The housing unit is erected,
The ultrapure water production system according to claim 1, wherein the supply unit is arranged on the upper side of the storage unit, and the discharge unit is arranged on the lower side of the storage unit. The ultrapure water production system according to claim 1 or 2, wherein the ion exchange resin has a structure in which the boron selective ion exchange resin and an ion exchange resin other than the boron selective ion exchange resin are laminated. The ultrapure water production system according to claim 3, wherein the layer height of the boron selective ion exchange resin is larger than the layer height of an ion exchange resin other than the boron selective ion exchange resin. The method for producing ultrapure water using the ultrapure water production system according to any one of claims 1 to 4.

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