JP2012139687A - Pure water manufacturing apparatus and pure water manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pure water manufacturing apparatus capable of manufacturing pure water with an extremely low boron concentration by a high water recovery rate, and a method for manufacturing the pure water.SOLUTION: The pure water manufacturing apparatus includes: a pre-treating apparatus 5 for treating raw water W0; a first electric deionization apparatus 6A which receives treated water W1 from the pre-treating apparatus 5 into a desalination chamber 11A and performs a deionization treatment to eliminate boron; and a second electric deionization apparatus 6B which receives concentrated water W4 obtained by introducing a part of the desalinated water from the first electric desalination apparatus 6A into a concentration chamber of the first electric deionization apparatus 6A into a desalination chamber 11B, and performs deionization treatment to eliminate boron, and supplies the desalinated water W5 from the second electric deionization apparatus 6B to a front stage of the first electric deionization apparatus 6A.

Description

  The present invention relates to a pure water production apparatus suitable for incorporation into an ultrapure water production system or the like, and more particularly to a pure water production apparatus for producing pure water having a low boron concentration. The present invention also relates to a pure water production method suitable for an ultrapure water production system or the like, and more particularly to a pure water production method for producing pure water having a low boron concentration.

  The ultrapure water production system is generally composed of a pretreatment system, a primary pure water system, and a subsystem. The pretreatment system is composed of a turbidity treatment device such as coagulation filtration, MF membrane (microfiltration membrane), UF membrane (ultrafiltration membrane), etc., and a dechlorination treatment device such as activated carbon.

  The primary pure water system is composed of an RO (reverse osmosis membrane) device, a degassing membrane device, an electrodeionization device, and the like, and most of the ion components and TOC components are removed by the primary pure water system. In addition, the subsystem is composed of a UV device (ultraviolet oxidation device), a non-regenerative ion exchange device, a UF device (ultrafiltration device), etc., and removes trace ions, particularly low-molecular trace organic substances, and particulates. Removal is performed. In general, the ultrapure water produced by this subsystem is sent to the point of use, and the excess ultrapure water is generally returned to the tank in the previous stage of the subsystem.

  By the way, the required water quality of ultrapure water becomes stricter year by year, and ultrapure water having a boron concentration of 1 ppt or less is now required in the state-of-the-art electronics industry. This boron exists almost as borate ions in ultrapure water, but these borate ions are weak ions and are difficult to remove. Therefore, in order to produce pure water with a low boron concentration, it has been proposed to improve the boron removal rate in the RO device by setting the water supply of the RO device to pH 10 or higher (see Patent Document 1).

  Also, the treated water after pretreatment is brought into contact with a boron-selective ion exchange resin (see Patent Document 2), and the raw water is desalted with a desalinator such as an RO device and then passed through a boron adsorption resin tower. Has been proposed (see Patent Document 3).

  Furthermore, an ultrapure water production apparatus has been proposed in which treated water obtained by passing raw water through a pretreatment device, a two-stage RO device, an electric regeneration type desalination device, etc. is brought into contact with a boron selective ion exchange resin (patent) Reference 4).

Japanese Patent No. 3321179 Japanese Patent No. 3200301 JP-A-8-89956 JP-A-9-192661

  In the pure water production method described in Patent Document 1, it is necessary to use an alkali or to provide an anion exchange resin tower in order to adjust the feed water of the RO device to pH 10 or higher, which increases chemical costs or equipment load. However, there is a problem that continuous operation is not possible.

  Moreover, although the pure water manufacturing method described in patent documents 2-4 distribute | circulates treated water to boron selective ion exchange resin or boron adsorption resin, it removes boron, If the concentration is high, these boron adsorbent resins and the like break through in a short period of time, and if the boron concentration of the water to be treated is low, for example, about 10 ppb or less, the boron removal rate is lowered. is there. Furthermore, since there is a possibility that the TOC is eluted from the boron adsorbing resin, there is a problem that the boron adsorbing resin needs to be washed and conditioned.

  Furthermore, it is conceivable to simultaneously remove borate ions, which are anions, using an electrodeionization device. However, borate ions are weak ions, so even if the current density of the electrodeionization device is increased and operated. It is difficult to make the removal rate 90% or more. In addition, it is difficult to increase the boron removal rate to 98% or more even when the RO device is combined.

  In recent years, the required water quality of ultrapure water has become stricter year by year. Even though the water concentration of boron concentration of 100 ppt or less, boron concentration of 10 ppt or less, and in some cases 1 ppt or less is required in the state-of-the-art electronics industry, it has a simple structure. There was no pure water production apparatus that could achieve this. In order to achieve this using an electrodeionization apparatus, it is necessary that at least the boron removal rate in the electrodeionization apparatus is 99% or more, particularly 99.5% or more.

  In order to achieve a boron removal rate of 99% or more in the electrodeionization apparatus, the electrodeionization apparatus is set by setting the water recovery rate to about 80% in order to suppress boron concentration in the pure water production system. It is necessary to operate and to discharge about 20% concentrated water out of the system. For this reason, there is a problem that the water recovery rate is low when the electrodeionization apparatus is used.

  This invention is made | formed in view of the said subject, and it aims at providing the pure water manufacturing apparatus which can manufacture the pure water with very low boron concentration with a high water recovery rate. Another object of the present invention is to provide a pure water production method capable of producing pure water having a low boron concentration with a high water recovery rate.

  In order to solve the above-mentioned problems, first, the present invention provides a pretreatment device for treating raw water, and a first electrodeionization treatment in which deionization treatment is performed by receiving treated water from the pretreatment device in a demineralization chamber. A deionized water from the second electrodeionization device, and a second electrodeionization device that receives the concentrated water from the first electrodeionization device in a demineralization chamber and performs a deionization process. Is provided to the front stage of the first electrodeionization apparatus (Invention 1).

  In order to improve the water recovery rate in the pure water production apparatus, it is conceivable that the concentrated water from the electrodeionization apparatus is returned to the pure water production system without being discarded. Since it is contained at a high concentration, if it is returned as it is, the boron concentration in the system will increase. However, according to the said invention (invention 1), the concentration of boron from the first electrodeionization device is processed by the second electrodeionization device, so that the boron concentration is higher than the treatment water from the pretreatment device. Since reduced demineralized water can be obtained, supplying the demineralized water to the first stage of the first electrodeionization device effectively reduces the boron concentration of the production water (demineralized water) produced by the pure water production apparatus. However, the water recovery rate can be improved.

  The above invention (Invention 1) further includes a third electrodeionization apparatus that receives the concentrated water from the second electrodeionization apparatus in a demineralization chamber and performs a deionization process, and further includes the second electrodeionization apparatus. It is preferable to supply demineralized water from the ion device and demineralized water from the third electrodeionization device to the first stage of the first electrodeionization device (Invention 2).

  By removing further boron from the concentrated water from the second electrodeionization apparatus, demineralized water having a boron concentration lower than that of the pretreatment apparatus can be obtained. According to the above, by supplying the demineralized water to the front stage of the first electrodeionization device, the water recovery rate can be further improved.

In the above invention (invention 2), the silica concentration in the treated water from the pre-processing device is received in the desalting compartment of the first electrodeionization apparatus is preferably not more than 30 ppb (SiO ₂ equivalent) ( Invention 3).

When treated water containing silica is treated with an electrodeionization device, the silica concentration is concentrated five times per one electrodeionization device, and the silica concentration of the treated water treated with the electrodeionization device is the standard. If the value exceeds 800 ppb, silica scale may be generated in the electrodeionization apparatus. However, as in the above invention (Invention 3), when the silica concentration of the treated water in the pretreatment device is 30 ppb (SiO ₂ equivalent) or less, the treatment to be received in the demineralization chamber of the third electrodeionization device. Since the silica concentration of water (concentrated water from the second electrodeionization device) can be 800 ppb or less, generation of silica scale in the electrodeionization device (particularly the third electrodeionization device) is prevented. It is possible to operate the pure water production apparatus stably.

  In the said invention (invention 1-3), it is provided in the back | latter stage of the said 1st electrodeionization apparatus, deionized water from the said 1st electrodeionization apparatus is received in a desalination chamber, and a deionization process is performed. 4 is further provided, and the concentrated water from the fourth electrodeionization device is preferably supplied to the front stage of the first electrodeionization device (Invention 4).

  Concentrated water from the fourth electrodeionization device has a lower boron concentration than the treated water of the pretreatment device because boron has been removed by the first electrodeionization device in the previous stage. According to the said invention (invention 4), while supplying the concentrated water from a 4th electrodeionization apparatus to the front | former stage of a 1st electrodeionization apparatus, while being able to improve a water recovery rate further, By further treating the demineralized water from the one electrodeionization apparatus with the fourth electrodeionization apparatus, production water (demineralized water) having an extremely low boron concentration can be produced.

  In the said invention (invention 1-4), it is preferable that the demineralization chamber of the said electrodeionization apparatus is provided with the division member which divides the said demineralization chamber into several small chambers (invention 5).

  According to the above invention (Invention 5), in the desalting chamber, since the water to be treated can be passed through substantially the entire interior of each small chamber, a short circuit of the water to be treated can be prevented, and thereby the desalting is performed. When the chamber is filled with an ion exchanger, the ion exchanger and the water to be treated can be more effectively brought into contact with each other to promote the movement of boron in the desalting chamber, thereby further reducing the boron concentration. Production water (demineralized water) can be produced.

  In the said invention (invention 1-5), a part of demineralized water from the said electrodeionization apparatus is made into the concentration chamber of the said electrodeionization apparatus from the direction opposite to the introduction direction of the treated water to the said demineralization chamber. It is preferably introduced excessively (Invention 6).

  By introducing drainage water (demineralized water) from a desalting chamber with good water quality from the outlet side of the desalting chamber toward the inlet side, the concentration of boron between the desalting chamber and the concentration chamber is increased. The concentration gradient can be relaxed. In particular, by introducing desalted water into the concentrating chamber in a countercurrent transient manner, the boron concentration of the concentrated water at the outlet side of the desalting chamber in the concentrating chamber is reduced, and desalination by concentration diffusion is performed. Since the influence on the chamber side (diffusion of boron from the concentrating chamber side to the desalting chamber side) can be suppressed, according to the invention (Invention 6), the boron removal rate by the electrodeionization device is dramatically improved. Can be improved.

  Second, the present invention is a pure water production method for performing deionization treatment by introducing treated water obtained by treating raw water with a pretreatment device into a demineralization chamber of a first electrodeionization device, Concentrated water from the electrodeionization apparatus is introduced into the demineralization chamber of the second electrodeionization apparatus, and the demineralized water from the second electrodeionization apparatus is placed upstream of the first electrodeionization apparatus. A pure water production method is provided (Invention 7).

  According to the said invention (invention 7), the concentration of boron from the first electrodeionization apparatus was processed by the second electrodeionization apparatus, thereby reducing the boron concentration compared to the treated water of the pretreatment apparatus. Demineralized water can be obtained. Therefore, by supplying such demineralized water to the first stage of the first electrodeionization apparatus, the water recovery rate can be improved while effectively reducing the boron concentration of the production water (demineralized water).

  In the said invention (invention 7), the concentrated water from said 2nd electrodeionization apparatus is introduce | transduced into the demineralization chamber of a 3rd electrodeionization apparatus, and the desalination water from said 2nd electrodeionization apparatus It is preferable to introduce demineralized water from the third electrodeionization apparatus into the front stage of the first electrodeionization apparatus (Invention 8).

  By removing further boron from the concentrated water from the second electrodeionization apparatus, demineralized water having a boron concentration lower than the treated water of the pretreatment apparatus can be obtained, so that the above invention (Invention 8) According to the above, by supplying the demineralized water to the front stage of the first electrodeionization device, the water recovery rate can be further improved.

In the above inventions (Inventions 7 and 8), the pretreatment apparatus is configured so that the silica concentration of the treated water introduced into the demineralization chamber of the first electrodeionization apparatus is 30 ppb (SiO ₂ equivalent) or less. It is preferable to treat the raw water (Invention 9).

As in the above invention (Invention 9), the raw water is treated in the pretreatment device so that the silica concentration of the treatment water introduced into the demineralization chamber of the first electrodeionization device is 30 ppb (SiO ₂ equivalent) or less. As a result, the silica concentration of the water to be treated (concentrated water from the second electrodeionization device) introduced into the demineralization chamber of the third electrodeionization device can be 800 ppb or less. Generation of silica scale in the ion device can be prevented, and production water (desalted water) having a low boron concentration can be stably produced.

  In the said invention (invention 7-9), the demineralized water from the said 1st electrodeionization apparatus is introduce | transduced into the demineralization chamber of a 4th electrodeionization apparatus, It is preferable to introduce the concentrated water into the first stage of the first electrodeionization apparatus (Invention 10).

  Since the demineralized water from the first electrodeionization apparatus introduced into the demineralization chamber of the fourth electrodeionization apparatus is demineralized water from which boron has been sufficiently removed, the deionized water from the fourth electrodeionization apparatus Since the concentrated water has a lower boron concentration than the treated water of the pretreatment device, according to the above invention (Invention 10), the concentrated water from the fourth electrodeionization device is used as the first electrodeionization device. The water recovery rate can be further improved by supplying it to the front stage, and the deionized water from the first electrodeionization apparatus is further processed by the fourth electrodeionization apparatus, so that extremely low boron Concentrated production water (demineralized water) can be produced.

  In the above inventions (Inventions 7 to 10), a part of the demineralized water from the electrodeionization device is introduced into the concentration chamber of the electrodeionization device from the direction opposite to the direction in which treated water is introduced into the demineralization chamber. It is preferably introduced excessively (Invention 11).

  By introducing drainage water (demineralized water) from a desalting chamber with good water quality from the outlet side of the desalting chamber toward the inlet side, the concentration of boron between the desalting chamber and the concentration chamber is increased. The concentration gradient can be relaxed, and the concentration of boron in the concentrated water at the outlet side of the desalting chamber in the concentrating chamber is lowered by introducing the desalting water into the concentrating chamber in a transient manner. Can be suppressed (diffusion of boron from the concentrating chamber side to the desalting chamber side), so according to the invention (Invention 11), the removal rate of boron by the electrodeionization device is dramatically improved. Production water (desalted water) having a lower boron concentration can be produced.

  ADVANTAGE OF THE INVENTION According to this invention, the pure water manufacturing apparatus which can manufacture the pure water with low boron concentration with a high water recovery rate can be provided. Moreover, according to this invention, the pure water manufacturing method which can manufacture the pure water with low boron concentration with a high water recovery rate can be provided.

It is a flowchart which shows the pure water manufacturing apparatus which concerns on one Embodiment of this invention. It is a schematic block diagram which shows the electrodeionization apparatus in the same embodiment. It is a schematic block diagram which shows the partition member arrange | positioned in the demineralization chamber of the electrodeionization apparatus in the same embodiment. It is a flowchart which shows the pure water manufacturing apparatus of Example 1. FIG.

Hereinafter, an embodiment of a pure water production apparatus of the present invention will be described in detail based on the drawings.
FIG. 1 is a flowchart showing a pure water production apparatus according to the present embodiment, and FIG. 2 is a schematic configuration diagram showing first to fourth electrodeionization apparatuses in the present embodiment.

  As shown in FIG. 1, the pure water production apparatus 10 includes an activated carbon device 1, a heater 2, a membrane filtration device 3, a raw water tank 4, a pretreatment device 5, water storage tanks T <b> 1 to T <b> 3, To fourth electrodeionization devices 6A to 6D and a primary pure water sub-tank 7.

In the present embodiment, the pretreatment device 5 includes a first reverse osmosis membrane (RO) device 51, a second reverse osmosis membrane (RO) device 52, and a decarbonation membrane device 53. This pretreatment device 5 is designed so that treated water W1 having a silica concentration of 30 ppb (SiO ₂ equivalent) or less is introduced into the demineralization chamber of the first electrodeionization device 6A according to the quality of the raw water W0. Just do it.

  In the pure water production apparatus 10 as described above, the first to fourth electrodeionization apparatuses 6A to 6D have a plurality of anion exchanges between the anodes 15A to 15D and the cathodes 16A to 16D, as shown in FIG. Desalination chambers 11A to 11D and concentration chambers 12A to 12D, in which membranes 13A to 13D and cation exchange membranes 14A to 14D are alternately arranged, and are partitioned by these anion exchange membranes 13A to 13D and cation exchange membranes 14A to 14D And.

  The flow path R11 of the treated water W1 from the pretreatment device 5 is connected to the inlet side of the demineralized chamber 11A of the first electrodeionization device 6A, and the demineralized water W2 is connected to the outlet side of the demineralized chamber 11A. The flow path R12 is connected, and the treated water W1 from the pretreatment device 5 can be treated and taken out as demineralized water W2.

  A branch flow path R13 branched from the flow path R12 and connected to the concentration chamber 12A is provided in the middle of the flow path R12, and a part of the desalted water W2 from the desalination chamber 11A is supplied to the desalination chamber 11A. It can be introduced into the concentrating chamber 12A from the outlet side toward the inlet side. When a part of the desalted water W2 is introduced into the concentration chamber 12A, it is preferably introduced in a transient manner. In this way, by introducing a part of the desalted water W2 into the concentrating chamber 12A in a countercurrent and transient manner, the concentration of boron in the concentrated water at the outlet side of the desalting chamber 11A in the concentrating chamber 12A is lowered, and deconcentration due to concentration diffusion is performed. Since the influence on the salt chamber 11A side (diffusion of boron from the concentration chamber 12A side to the desalting chamber 11A side) can be suppressed, the boron removal rate can be dramatically improved.

  A water storage tank T2 is connected to the outlet side of the concentrating chamber 12A via a flow path R14 of concentrated water so that the concentrated water W4 discharged from the concentrating chamber 12A is stored in the water storage tank T2 through the flow path R14. It is configured.

  A water storage tank T2 is connected to the inlet side of the demineralization chamber 11B of the second electrodeionization device 6B via a flow path R21, so that from the concentration chamber 12A of the first electrodeionization device 6A. The discharged concentrated water W4 is configured to be introduced into the desalting chamber 11B through the flow path R21.

  A water storage tank T1 is connected to the outlet side of the demineralization chamber 11B of the second electrodeionization apparatus 6B via a flow path R22 of the demineralized water W5, and the demineralized water W5 from the demineralization chamber 11B flows through the flow path. It is configured to be stored in the water storage tank T1 through R22.

  A branch flow path R23 branched from the flow path R22 and connected to the concentration chamber 12B is provided in the middle of the flow path R22, and a part of the desalted water W5 from the desalination chamber 11B is supplied to the desalination chamber 11B. It can be introduced into the concentration chamber 12B from the outlet side toward the inlet side. When a part of the desalted water W5 is introduced into the concentration chamber 12B, it is preferably introduced in a transient manner. In this way, by introducing a part of the desalted water W5 into the concentrating chamber 12B in a countercurrent transient manner, the boron concentration of the concentrated water at the outlet side of the desalting chamber 11B in the concentrating chamber 12B is reduced, and deconcentration by concentration diffusion is performed. Since the influence on the salt chamber 11B side (diffusion of boron from the concentration chamber 12B side to the desalting chamber 11B side) can be suppressed, the boron removal rate can be dramatically improved.

  A water storage tank T3 is connected to the outlet side of the concentrating chamber 12B through a flow path R24 of concentrated water so that the concentrated water W6 discharged from the concentrating chamber 12B is stored in the water storage tank T3 through the flow path R24. It is configured.

  A water storage tank T3 is connected to the inlet side of the demineralization chamber 11C of the third electrodeionization device 6C via a flow path R31, so that from the concentration chamber 12B of the second electrodeionization device 6B. The discharged concentrated water W6 is configured to be introduced into the desalting chamber 11C through the flow path 31.

  A water storage tank T1 is connected to the outlet side of the demineralization chamber 11C of the third electric deionization device 6C via a flow path R32 of demineralized water W7, and the demineralized water W7 from the demineralization chamber 11C flows through the flow path. It is configured to be stored in the water storage tank T1 through R32.

  In the middle of the flow path R32, a branch flow path R33 branched from the flow path 32 and connected to the concentration chamber 12C is provided, and a part of the demineralized water W7 from the demineralization chamber 11C is supplied to the demineralization chamber 11C. It can be introduced into the concentration chamber 12C from the outlet side toward the inlet side. When a part of the desalted water W7 is introduced into the concentration chamber 12C, it is preferable to introduce a part of the desalted water W7 in a transient manner. In this way, by introducing a portion of the desalted water W7 into the concentrating chamber 12C in a countercurrent and transient manner, the concentration of the concentrated water at the outlet side of the desalting chamber 11C in the concentrating chamber 12C is reduced, and desalting due to concentration diffusion Since the influence on the chamber 11C side (diffusion of boron from the concentration chamber 12C side to the desalting chamber 11C side) can be suppressed, the boron removal rate can be greatly improved.

  A flow path R41 (R12) of demineralized water W2 from the first electrodeionization device 6A is connected to the inlet side of the demineralization chamber 11D of the fourth electrodeionization device 6D, and the outlet side of the desalination chamber 11D Is connected to a flow path R42 of demineralized water W8. Thereby, it has the structure which can process the desalted water W2 with the 4th electrodeionization apparatus 6D, and can take out as desalted water (final production water) W8.

  In the middle of the flow path R42, a branch flow path R43 branched from the flow path R42 and connected to the concentration chamber 12D is provided, and a part of the desalted water W8 from the desalting chamber 11D is supplied to the desalting chamber 11D. It can be introduced into the concentrating chamber 12D from the outlet side toward the inlet side. When a part of the desalted water W8 is introduced into the concentration chamber 12D, it is preferable to introduce a part of the desalted water W8 in a transient manner. In this way, by introducing a part of the desalted water W8 into the concentrating chamber 12D in a countercurrent and transient manner, the concentration of the concentrated water on the outlet side of the desalting chamber 11D in the concentrating chamber 12D is reduced, and desalting due to concentration diffusion Since the influence on the chamber 11D side (diffusion of boron from the concentration chamber 12D side to the desalting chamber 11D side) can be suppressed, the boron removal rate can be greatly improved.

  A water storage tank T1 is connected to the outlet side of the concentrating chamber 12D via a concentrated water channel R44 so that the concentrated water W3 discharged from the concentrating chamber 12D is stored in the water tank T1 through the channel R44. It is configured.

  In the demineralization chambers 11A to 11D of the first to fourth electrodeionization devices 6A to 6D, partition members 8 made of a honeycomb structure partitioned into a plurality of small chambers 9 as shown in FIG. Each of the plurality of small chambers 9 is filled with an ion exchanger (not shown). A large number of the small chambers 9 are arranged vertically and horizontally, and a pair of side sides of each small chamber 9 is disposed so as to be in the water passing direction in the desalting chambers 11A to 11D, that is, the vertical direction in FIG.

  The partition member 8 may be integrally formed in advance, or may be formed by combining a plurality of members. As shown in FIG. 3B, the partition member 8 is bent at an angle of 120 ° with respect to the longitudinal surface 81 and the longitudinal surface 81 and has a water permeability that is continuous with the longitudinal surface 81. It is configured by connecting the longitudinal direction surfaces 81 and 81 of the bending plate 83 having the facing surface 82 with an adhesive or the like. The bent plate 83 is preferably made of a material having water permeability, for example, a woven fabric, a nonwoven fabric, a mesh, a porous material, or the like.

  In addition, the longitudinal direction surface 81 of the bending plate 83 may have water permeability or may not have water permeability. If the longitudinal surface 81 does not have water permeability, the water to be treated in the small chamber 9 will flow into the lower small chamber 9 only through the directing surface 82 of the bent plate 83, and the entire small chamber 9 will be covered. Since the treated water flows substantially uniformly, the ion exchanger filled in the desalting chambers 11A to 11D and the treated water (treated water W1, desalted water W2, concentrated water W4, W6) are effectively brought into contact with each other. Can be made.

  Examples of the ion exchanger filled in the desalting chambers 11A to 11D include anion exchangers, cation exchangers, and amphoteric ion exchangers, and these may be used alone or as a mixture of two or more. May be. Also, two or more of these ion exchangers may be filled in the desalting chambers 11A to 11D in multiple layers.

  The concentration chambers 12A to 12D may also be filled with an ion exchanger. Because the ion exchangers are also filled in the concentration chambers 12A to 12D, the current flows more easily, so that the movement of weak ions such as boron from the desalting chambers 11A to 11D to the concentration chambers 12A to 12D is further improved. This can promote the removal rate of boron from the water to be treated.

  In the pure water production apparatus 10 having such a configuration, first, the raw water W0 is introduced into the activated carbon apparatus 1 to remove organic substances, and then heated to a predetermined temperature with the heater 2, and then subjected to membrane filtration. It is introduced into the apparatus 3 to remove the solid fine particles and temporarily stored in the raw water tank 4. Subsequently, the raw water W 0 stored in the raw water tank 4 is processed by the pretreatment device 5.

In the pretreatment device 5, strong ionic impurities in the raw water W0 are removed by the first reverse osmosis membrane (RO) device 51 and the second reverse osmosis membrane (RO) device 52, and decarboxylation is further performed. Carbonate ions (CO ₂ ) are removed by the membrane device 53, and the treated water W1 can be obtained.

The pretreatment device 5 is designed so that the silica concentration in the treated water W1 is 30 ppb (SiO ₂ equivalent) or less, preferably 20 ppb or less, particularly preferably 10 ppb or less. When the silica concentration of the water to be treated in the electrodeionization apparatus exceeds 800 ppb, there is a problem that silica scale is generated. On the other hand, as described later, the boron removal rate of 99% or more in each of the electrodeionization apparatuses 6A to 6D In order to achieve the above, it is necessary to operate the water recovery rate in each of the electrodeionization devices 6A to 6D at about 80%. When the electrodeionization devices 6A to 6D are operated under such conditions, the silica concentration rate Becomes about 5 times. Therefore, when the silica concentration of the treated water W1 exceeds 30 ppb (for example, 40 ppb), the silica concentration of the concentrated water W4 from the first electrodeionization device 6A becomes 200 ppb, and from the second electrodeionization device 6B. The concentrated water W6 has a silica concentration of 1000 ppb, which may cause silica scale in the third electrodeionization apparatus 6C. Therefore, when the silica concentration in the treated water W1 is 30 ppb or less, the silica concentration of the concentrated water W6 introduced into the third electrodeionization apparatus 6C is 800 ppb or less, which is a reference value, and a silica scale is generated. Can be prevented.

The treated water W1 thus obtained is introduced into the demineralization chamber 11A of the first electrodeionization apparatus 6A for treatment. The first electrodeionization apparatus 6A is preferably operated at a current density of 300 mA / dm ² or more. By operating at such a current density, although depending on the performance of the electrodeionization apparatus, a boron removal rate of 99% or more, particularly 99.5% or more, which could not be achieved by the conventional electrodeionization apparatus. be able to.

  At this time, it is preferable to operate the first electrodeionization apparatus 6A so that the recovery rate (demineralized water amount / treated water amount) of the demineralized water W2 from the first electrodeionization apparatus 6A is about 80%. . By setting the recovery rate of the demineralized water W2 within the above range, the boron removal rate in the first electrodeionization device 6A can be 99% or more.

  A part of the demineralized water W2 obtained from the first electrodeionization apparatus 6A is introduced into the concentrating chamber 12A in a countercurrent transient manner. Thereby, the boron concentration of the concentrated water on the inlet side of the concentrating chamber 12A can be lowered, and the influence on the desalting chamber 11A side due to the concentration diffusion can be suppressed, so that the boron removing efficiency is dramatically improved. be able to.

The concentrated water W4 discharged from the concentration chamber 12A of the first electrodeionization device 6A and stored in the water storage tank T2 is introduced into the demineralization chamber 11B of the second electrodeionization device 6B and processed. Similarly, the second electrodeionization apparatus 6B is preferably operated at a current density of 300 mA / dm ² or more in order to ensure a boron removal rate of 99% or more, particularly 99.5% or more.

  At this time, it is preferable to operate the second electrodeionization apparatus 6B so that the recovery rate of the demineralized water W5 from the second electrodeionization apparatus 6B (amount of demineralized water / amount of treated water) is about 80%. . By setting the recovery rate of the demineralized water W5 within the above range, the boron removal rate in the second electrodeionization apparatus 6B can be about 99%.

  Since the demineralized water W5 from the second electrodeionization apparatus 6B thus treated has a boron concentration lower than the boron concentration of the treated water W1 from the pretreatment apparatus 5, the demineralized water W5. Is introduced into the water storage tank T1 at the front stage of the first electrodeionization apparatus 6A. As a result, the water recovery rate can be improved without increasing the boron concentration in the system of the pure water production apparatus 10.

  A part of the demineralized water W5 obtained from the second electrodeionization apparatus 6B is introduced into the concentrating chamber 12B in a countercurrent transient manner. Thereby, the boron concentration of the concentrated water on the inlet side of the concentrating chamber 12B can be lowered, and the influence on the desalting chamber 11B side due to the concentration diffusion can be suppressed, so that the boron removing efficiency is dramatically improved. be able to.

The concentrated water W6 discharged from the concentration chamber 12B of the second electrodeionization device 6B and stored in the water storage tank T3 is introduced into the demineralization chamber 11C of the third electrodeionization device 6C and processed. Similarly, the third electrodeionization apparatus 6C is preferably operated at a current density of 300 mA / dm ² or more in order to ensure a boron removal rate of 99% or more, particularly 99.5% or more.

  At this time, it is preferable to operate the third electrodeionization apparatus 6C so that the recovery rate (demineralized water amount / treated water amount) of the demineralized water W7 from the third electrodeionization apparatus 6C is about 80%. . By setting the recovery rate of the demineralized water W7 within the above range, the boron removal rate in the third electrodeionization device 6C can be about 99%.

  Since the boron concentration of the demineralized water W7 from the third electrodeionization apparatus 6C thus treated is also lower than the boron concentration of the treated water W1 from the pretreatment apparatus 5, the demineralized water W7 is introduced into the water storage tank T1 at the front stage of the first electrodeionization apparatus 6A. Thereby, the water recovery rate can be further improved without increasing the boron concentration in the system of the pure water production apparatus 10.

  A part of the demineralized water W7 obtained from the third electrodeionization apparatus 6C is introduced into the concentrating chamber 12C in a countercurrent transient manner. Thereby, the boron concentration of the concentrated water on the inlet side of the concentration chamber 12C can be lowered, and the influence on the desalting chamber 11C side due to the concentration diffusion can be suppressed, so that the boron removal efficiency is dramatically improved. be able to.

The demineralized water W2 from the first electrodeionization apparatus 6A is introduced into the demineralization chamber 11D of the fourth electrodeionization apparatus 6D for treatment. Thereby, the final production water (desalted water) W8 having a very low boron concentration can be produced. Similarly, the fourth electrodeionization apparatus 6D is preferably operated at a current density of 300 mA / dm ² or more in order to ensure a boron removal rate of 99% or more, particularly 99.5% or more.

  At this time, it is preferable to operate the fourth electrodeionization apparatus 6D so that the recovery rate (demineralized water amount / treated water amount) of the demineralized water W8 from the fourth electrodeionization apparatus 6D is about 80%. . By setting the recovery rate of the demineralized water W8 within the above range, the boron removal rate in the fourth electrodeionization apparatus 6D can be about 99%.

  The concentrated water W3 from the fourth electrodeionization device 6D after being treated in this way has a boron concentration lower than the boron concentration of the treated water W1 from the pretreatment device 5, so that the concentration Water W3 is introduced into a water storage tank T1 at the front stage of the first electrodeionization apparatus 6A. Thereby, the water recovery rate can be further improved without increasing the boron concentration in the system of the pure water production apparatus 10.

  A part of the demineralized water W8 obtained from the fourth electrodeionization apparatus 6D is introduced into the concentrating chamber 12D in a countercurrent transient manner. Thereby, the boron concentration of the concentrated water on the inlet side of the concentrating chamber 12D can be lowered, and the influence on the desalting chamber 11D side due to the concentration diffusion can be suppressed, so that the boron removing efficiency is dramatically improved. be able to.

  As described above, in the pure water production apparatus 10 according to the present embodiment, the demineralized water W5 from the second electrodeionization device 6B, the desalted water W7 from the third electrodeionization device 6C, and the fourth electrodeionization device. By returning the concentrated water W3 from the ion device 6D to the water storage tank T1 in the first stage of the first electrodeionization device 6A, the water recovery rate in each of the electrodeionization devices 6A to 6D is about 80% and is 99% or more. While ensuring a boron removal rate, the recovery rate of final product water (demineralized water) W8 can be maintained at a high level of 98% or more. Therefore, the pure water producing apparatus 10 according to the present embodiment can produce an effect that the desalted water from which boron is effectively removed can be efficiently produced at a high water recovery rate.

  Moreover, according to the pure water manufacturing apparatus 10 which concerns on this embodiment, sufficient boron from the treated water W1 is provided by providing the 1st and 4th electrodeionization apparatus 6A, 6D connected in two steps in series. Removal is possible, continuous operation is possible, and the use of chemicals such as alkalis reduces the environmental load. Furthermore, it can handle a wide range of boron concentration in feed water (raw water), and does not cause breakthrough compared to boron adsorbent resin, etc., so pure water that has been stably reduced in boron concentration for several years Can be manufactured.

  Furthermore, according to the pure water producing apparatus 10 according to the present embodiment, the desalted waters W5 and W7 and the concentrated water W3 having a lower boron concentration than the treated water W1 are returned to the water storage tank T1, so that the treatment is performed over time. Since the boron concentration of the water W1 is lowered, it is possible to produce pure water having a boron concentration of 1 ppt or less.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, in the above-described embodiment, the third electrodeionization device 6C and the fourth electrodeionization device 6D do not have to include either one or both. Whether to provide the third electrodeionization device 6C and the fourth electrodeionization device 6D according to the boron concentration of the final product water desired in the pure water production apparatus 10 according to the present embodiment is appropriately determined. do it. Further, when ultrapure water having a lower boron concentration is required, an electrodeionization device may be provided in series after the fourth electrodeionization device 6D.

  In the above embodiment, the pretreatment device 5 can supply treated water W1 having a silica concentration of 30 ppb or less to the first electrodeionization device 6A and obtain ultrapure water having a desired boron concentration. Various settings can be made according to the quality of the raw water W0.

Specifically, the pre-processing device 5 can be configured as follows.
(1) RO device + decarbonation membrane device (2) first RO device + second RO device + decarbonation membrane device (3) ion exchange resin device (2B3T) + RO device + decarbonation membrane device (4) ion Exchange resin device (4B5T) + RO device + decarbonation membrane device

  Furthermore, in the said embodiment, the partition member 8 arrange | positioned in the demineralization chambers 11A-11D of the 1st-4th electrodeionization apparatus 6A-6D consists of a honeycomb structure which has the hexagonal small chamber 9. FIG. However, the present invention is not limited to this. For example, it may have a rectangular or triangular chamber, or a rectangular or triangular chamber and a hexagonal chamber. You may have.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited to the following Example.
In the present example, the following electrodeionization apparatus was used.
First electrodeionization apparatus 6A (manufactured by Kurita Kogyo Co., Ltd., product name: KCDI-UPz-250H, amount of treated water: 25 m ³ / hr)
Second electrodeionization apparatus 6B (manufactured by Kurita Kogyo Co., Ltd., product name: KCDI-UPz-150H, amount of treated water: 15 m ³ / hr)
Third electrodeionization device 6C (manufactured by Kurita Kogyo Co., Ltd., product name: KDDI-UPz-020H, amount of treated water: 2 m ³ / hr)
Fourth electrodeionization apparatus 6D (manufactured by Kurita Kogyo Co., Ltd., product name: KDDI-UPz-200H, amount of treated water: 20 m ³ / hr)

[Example 1]
As shown in FIG. 4, the pure water manufacturing apparatus provided with the 1st-4th electrodeionization apparatus 6A-6D was manufactured. And the to-be-processed water W0 (the to-be-processed water corresponded to the treated water processed with the 2 step | paragraph reverse osmosis membrane apparatus) whose boron concentration is 31 ppb is supplied to the water storage tank T1 at 61.9 m < ³ > / hr, This pure water manufacturing apparatus Was processed using.

Water to be treated W1 introduced into the demineralization chamber 11A of the first electrodeionization device 6A after the elapse of a predetermined time from the start of treatment, demineralized water W2, W5, W7, W8 from the electrodeionization devices 6A to 6D, and The boron ion concentrations of concentrated water W3, W4, W6, and W9 and their water amounts (m ³ / hr) were measured, and the water recovery rate (%) was calculated. In addition, the water recovery rates in the first to fourth electrodeionization apparatuses 6A to 6D were set to 82%, 83%, 85%, and 83%, respectively.
The results are shown in Table 1.

[Comparative Example 1]
A pure unit having the same configuration as that of Example 1 except that the second electrodeionization device 6B and the third electrodeionization device 6C are not provided, and the concentrated water W4 from the first electrodeionization device 6A is discarded. The water to be treated W0 is treated in the water production apparatus, and the treated water W1, the first and fourth electric waters introduced into the demineralization chamber 11A of the first electrodeionization apparatus 6A after a predetermined time has elapsed from the start of the treatment. The boron ion concentration and the amount of water (m ³ / hr) of the demineralized water W2 and W8 and the concentrated water W3 and W4 from the deionizers 6A and 6D were measured, and the water recovery rate (%) was calculated. In addition, the water recovery rates in the first and fourth electrodeionization apparatuses 6A and 6D were set to 82% and 83%, respectively.
The results are shown in Table 1.

  As is clear from Table 1, in the pure water production apparatus of Example 1, the boron concentration of final product water (demineralized water) W8 from the fourth electrodeionization apparatus 6D is 0.4 ppt, which is the most advanced It was confirmed that ultrapure water satisfying the required water quality in the electronic industry field (boron concentration: 1 ppt or less) can be produced.

  On the other hand, also in the pure water production apparatus of Comparative Example 1, the boron concentration of the production water (demineralized water) from the fourth electrodeionization apparatus 6D is 0.5 ppt, and the state-of-the-art electronic industry is the same as in Example 1. It was confirmed that ultrapure water that satisfies the required water quality in the field (boron concentration: 1 ppt or less) can be produced.

  Thus, the pure water which can fully satisfy | fill the required water quality regarding a boron density | concentration can be manufactured by processing with the electrodeionization apparatus which connected the treated water W1 from a pretreatment apparatus in two steps in series. .

  However, the pure water production apparatus of Example 1 had an extremely high water recovery rate of 98%, whereas the pure water production apparatus of Comparative Example 1 had a low water recovery rate of 78%. In the pure water production apparatus of Example 1, the boron concentrations of the demineralized water from the second electrodeionization device 6B and the third electrodeionization device 6C are 2 ppb and 16 ppb, respectively, and the treatment from the pretreatment device 5 is performed. Since the concentration of boron in water is lower than the concentration of boron (31 ppb), the concentration of boron in the system does not increase even if such desalted water is returned to the water storage tank T1, whereas the production of pure water in Comparative Example 1 In the apparatus, since the boron concentration of the concentrated water W4 from the first electrodeionization apparatus 6A is 151 ppb and higher than the boron concentration of the water to be treated W0, the concentrated water W4 can be returned to the storage tank T1. This is due to the inability to do so.

  Thus, according to the pure water manufacturing apparatus of Example 1, it was confirmed that ultrapure water having a low boron concentration can be manufactured while ensuring a very high water recovery rate.

  INDUSTRIAL APPLICABILITY The pure water production apparatus and the pure water production method of the present invention are useful for producing pure water with an extremely high water recovery rate and a very low boron concentration.

5 ... Pretreatment device 51 ... First reverse osmosis membrane (RO) device (pretreatment device)
52 ... Second reverse osmosis membrane (RO) device (pretreatment device)
53 ... Decarbonation membrane device (pretreatment device)
6A ... 1st electrodeionization device 6B ... 2nd electrodeionization device 6C ... 3rd electrodeionization device 6D ... 4th electrodeionization device 8 ... Partition member 11A-D ... Desalination chamber 12A-D ... concentration chamber

Claims (9)

A pretreatment device for treating raw water;
A first electrodeionization apparatus that receives treated water from the pretreatment apparatus in a demineralization chamber and performs deionization to remove boron;
Concentrated water obtained by introducing a portion of demineralized water from the first electrodeionization device into the concentration chamber of the first electrodeionization device is received in the demineralization chamber and subjected to deionization treatment, and then boron. A second electrodeionization device for removing
An apparatus for producing pure water, characterized in that demineralized water from the second electrodeionization device is supplied to the front stage of the first electrodeionization device. _2. The pure water according to claim 1, wherein the silica concentration of the treated water from the pretreatment device received in the demineralization chamber of the first electrodeionization device is 30 ppb (in terms of SiO ₂ ) or less. manufacturing device. A third electrodeionization apparatus provided at a subsequent stage of the first electrodeionization apparatus, wherein demineralized water from the first electrodeionization apparatus is received in a demineralization chamber and deionized to remove boron. Further comprising
Concentrated water obtained by introducing a part of demineralized water from the third electrodeionization device into the concentration chamber of the third electrodeionization device is supplied to the front stage of the first electrodeionization device. The pure water manufacturing apparatus according to claim 1, wherein the apparatus is a pure water manufacturing apparatus.   The deionized chamber of the said electrodeionization apparatus is provided with the division member which divides the said demineralization chamber into several small chambers, The pure water manufacturing apparatus in any one of Claims 1-3 characterized by the above-mentioned. .   A part of the demineralized water from the electrodeionization device is introduced into the concentration chamber of the electrodeionization device in a transient manner from the direction opposite to the direction in which the treated water is introduced into the demineralization chamber. Item 5. The pure water production apparatus according to any one of Items 1 to 4. A pure water production method in which treated water obtained by treating raw water with a pretreatment apparatus is introduced into a demineralization chamber of a first electrodeionization apparatus and deionized to remove boron.
Concentrated water obtained by introducing a part of demineralized water from the first electrodeionization device into the concentration chamber of the first electrodeionization device is supplied to the demineralization chamber of the second electrodeionization device. Introduce and deionize to remove boron,
A method for producing pure water, characterized in that demineralized water from the second electrodeionization apparatus is introduced into a front stage of the first electrodeionization apparatus. The raw water is treated in the pretreatment device so that the silica concentration of the treatment water introduced into the demineralization chamber of the first electrodeionization device is 30 ppb (SiO ₂ equivalent) or less. Item 7. A method for producing pure water according to Item 6. Deionized water from the first electrodeionization device is introduced into a demineralization chamber of the third electrodeionization device to perform deionization treatment to remove boron,
Concentrated water obtained by introducing a part of demineralized water from the third electrodeionization device into the concentration chamber of the third electrodeionization device is introduced to the front stage of the first electrodeionization device. The method for producing pure water according to claim 6 or 7, wherein:   A part of the demineralized water from the electrodeionization device is introduced into the concentration chamber of the electrodeionization device in a transient manner from the direction opposite to the direction in which the treated water is introduced into the demineralization chamber. The pure water manufacturing method in any one of claim | item 6 -8.

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