JP2017176968A - Electric deionization apparatus, and production method of deionization water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric deionization apparatus that keeps a sufficient boron removal capacity with even a small number of cells in a desalination chamber, and a production method of deionization water using the electric deionization apparatus.SOLUTION: In an electric deionization apparatus, ion exchange membranes 13, 14 partition a space between an anode 11 and a cathode 12 into a concentration chamber 15 and a desalination chamber 16. Concentrated water is introduced into the concentration chamber and raw water is introduced into the desalination chamber 16 as water to be treated and taken out as product water. A part of the product water is introduced into the concentration chamber 15 as concentrated water in the counterflow direction to the flow in the desalination chamber 16. The desalination chamber 16 has a thickness of 10-20 mm, while an ion exchange resin packed in the desalination chamber 16 has an average particle diameter of 0.2-0.3 mm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrodeionization apparatus capable of highly removing boron in water to be treated and a method for producing deionized water using the electrodeionization apparatus.

  Conventionally, an ultrapure water production apparatus that produces ultrapure water from raw water such as city water, groundwater, and industrial water basically includes a pretreatment apparatus, a primary pure water production apparatus, and a secondary pure water production apparatus. . Among these, the pretreatment device is composed of agglomeration, levitation, filtration, a turbidity removal membrane device and the like. The primary pure water production apparatus is composed of one or more of activated carbon adsorption tower, ultraviolet (UV) oxidizer, chemical oxidizer, degasser, and the like, and a demineralizer. The desalting apparatus is constituted by one or a combination of two or more of a reverse osmosis (RO) membrane separation apparatus, an electrodeionization apparatus, and an ion exchange apparatus (mixed bed ion exchange apparatus or ion exchange pure water apparatus). The secondary pure water production apparatus is a combination of the same apparatus units as those of the primary pure water production apparatus. Generally, a low pressure UV oxidation apparatus, a mixed bed ion exchange apparatus, and an ultrafiltration (UF) ) Consists of a membrane separator.

  In each of these apparatus units, the raw water is desalted by an RO membrane separation apparatus, an electrodeionization apparatus, and a mixed bed ion exchange apparatus. The removal of fine particles in the raw water is performed by the RO membrane separation device and the UF membrane separation device, and the removal of the TOC component is performed by the RO membrane separation device, the ion-exchange pure water device, and the low-pressure UV oxidation device.

  In recent years, in the production of ultrapure water, strict water quality of, for example, 1 ppt or less has been demanded for boron.

  Conventionally, in a combination of an RO membrane separation device and an electrodeionization device, an electrodeionization device having a high boron removal rate (for example, “KCDI-UPz” manufactured by Kurita Kogyo Co., Ltd.) has been proposed. Even a high-performance electrodeionization apparatus has a boron removal rate of about 99.9%. For this reason, for example, treated water with a boron concentration of about 20 ppb is treated with an RO membrane separator to obtain RO permeated water with a boron concentration of about 10 ppb, and this is treated with an electrodeionization device with a boron removal rate of 99.9%. However, the boron concentration of the treated water (deionized water) obtained is only 10 ppt, and treated water having a boron concentration of 1 ppt or less cannot be obtained.

  A general electrodeionization apparatus is configured by alternately forming a plurality of cation exchange membranes and anion exchange membranes between a cathode and an anode, thereby alternately forming a concentration chamber and a desalting chamber. There are also provided those in which the ion exchange resin is filled and the concentration chamber is also filled with the ion exchange resin.

  In the electrodeionization apparatus, it is advantageous to reduce the thickness of the demineralization chamber in order to improve the boron removal rate. Patent Document 1 describes an electrodeionization apparatus with a high boron removal rate in which the thickness of the demineralization chamber is 5 mm or less.

  In a conventional electrodeionization apparatus, the ion exchange resin filled in the demineralization chamber and further the concentration chamber has a particle size of about 500 to 600 μm, and in many cases, consideration is given to the uniformity of the particle size. Has not been made.

  For example, in the example of Patent Document 2, “Diaion (registered trademark) SA10A” (average particle size: 540 μm) manufactured by Mitsubishi Chemical Corporation as an anion exchange resin in the demineralization chamber of an electrodeionization apparatus and a cation exchange resin Filled with “Diaion (registered trademark) SK1B” (average particle size: 620 μm) manufactured by Mitsubishi Chemical Corporation.

  Patent Document 3 discloses a mixture of ion exchange resin particle groups having a plurality of uniform particle diameters having different particle diameters in the desalting chamber, and the particle diameter of the ion exchange resin particle group having the largest uniform particle diameter is An apparatus for producing deionized water filled with particles having a particle diameter of 1.5 times or more of the ion exchange resin particle group having the smallest uniform particle diameter has been proposed, and the ion exchange resin particles having the smallest uniform particle diameter Although the particle size of the group is said to be 30 to 600 μm, the ion exchange resin specifically used in the examples includes a cation exchange resin having an average particle size of 630 μm, a cation exchange resin having an average particle size of 220 μm, This is a 25 / 22.5 / 52.5 (weight ratio) mixture of anion exchange resins having an average particle size of 575 μm.

JP 2011-110515 A JP 2001-113281 A Japanese Patent Laid-Open No. 10-258289

  An object of the present invention is to provide an electrodeionization apparatus having sufficient boron removal performance even if the number of cells in the desalination chamber is reduced, and a method for producing deionized water using the electrodeionization apparatus. .

  In the electrodeionization apparatus of the present invention, a concentration chamber and a desalination chamber are partitioned by an ion exchange membrane between an anode and a cathode, concentrated water is circulated to the concentration chamber, and raw water is treated as desalting chamber. In the deionization apparatus in which a part of the production water is circulated in the concentration chamber as concentrated water in the flow direction and the counterflow direction of the demineralization chamber. It is 10-20 mm, The average diameter of the ion exchange resin with which this desalination chamber is filled is 0.2-0.3 mm, It is characterized by the above-mentioned.

  The method for producing deionized water of the present invention produces deionized water using this electrodeionization device.

  In the electrodeionization apparatus of the present invention, the thickness of the demineralization chamber is increased to 10 to 20 mm. Thereby, the number of anion exchange membranes and cation exchange membranes is reduced, and the configuration cost of the electrodeionization apparatus is reduced. However, if the thickness of the desalting chamber is increased, the boron removal efficiency decreases. Therefore, in the present invention, an ion exchange resin having an average particle size as small as 0.2 to 0.3 mm is used to ensure boron removal efficiency. Therefore, according to the present invention, an electrodeionization apparatus having a low apparatus construction cost and having a sufficient boron removal capability is provided.

  When an ion exchange resin having a small average particle size is used, the surface area of the ion exchange resin is increased, so that the electric resistance is reduced and a current is ensured even when the applied voltage is lowered (that is, the operation is performed with the same current). Therefore, the power cost can be reduced.

It is typical sectional drawing of the electrodeionization apparatus which concerns on embodiment.

  FIG. 1 is a schematic cross-sectional view of an electrodeionization apparatus showing an embodiment of the present invention. In this electrodeionization apparatus, a plurality of anion exchange membranes (A membranes) 13 and cation exchange membranes (C membranes) 14 are alternately arranged between electrodes (anode 11 and cathode 12), and a concentrating chamber 15 and a desalting chamber. 16 are alternately formed, and the desalting chamber 16 is filled with an ion exchange resin having an average particle diameter of 0.2 to 0.3 mm.

  The concentration chamber 15, the anode chamber 17, and the cathode chamber 18 are also filled with an electric conductor such as an ion exchanger, activated carbon, or metal.

  Raw water is introduced from the inlet side of the desalting chamber 16, and product water is taken out from the outlet side of the desalting chamber 16. A part of this product water is passed through the concentrating chamber 15 in a counter-current and transient manner in the direction opposite to the water passing direction of the desalting chamber 16, and the outflow water of the concentrating chamber 15 is discharged out of the system. That is, in this electric deionization apparatus, the concentrating chambers 15 and the desalting chambers 16 are alternately arranged in parallel, and the inlet of the concentrating chamber 15 is provided on the product water take-out side of the desalting chamber 16. An outlet of the concentrating chamber 15 is provided on the 16 raw water inflow side. A part of the production water is sent to the inlet side of the anode chamber 17, the effluent water of the anode chamber 17 is fed to the inlet side of the cathode chamber 18, and the effluent water of the cathode chamber 18 is discharged out of the system as drainage. Discharged.

  In this way, by passing the production water through the concentration chamber 15 in a counter-current and transient manner with the desalination chamber 16, the concentration of the concentrated water in the concentration chamber 15 becomes lower toward the production water take-out side, which is caused by concentration diffusion. The influence on the desalting chamber 16 is reduced, and the removal rate of ions such as boron can be increased.

  In this electrodeionization apparatus, the thickness of the demineralization chamber 16 is increased to 10 to 20 mm. Thereby, the number of anion exchange membranes and cation exchange membranes is reduced, and the configuration cost of the electrodeionization apparatus is reduced. However, when the thickness of the desalting chamber 16 is increased, the boron removal efficiency decreases. To compensate for this, an ion exchange resin having a small average particle size of 0.2 to 0.3 mm is used to remove boron. Ensure efficiency. If an ion exchange resin having a small average particle diameter is used, the surface area of ions increases, so the electric resistance decreases, and even when the applied voltage is reduced, the current is secured, so the power cost Can be reduced. The number of desalting chambers is preferably about 10 to 100, especially about 40 to 60.

  When water to be treated is passed through the desalting chamber 16 in the vertical direction, the ion exchange resin filling height of the desalting chamber 16 is preferably 40 to 80 mm, and the width is preferably 30 to 60 mm. The current value is preferably 10 to 20 A in order to obtain a high boron removal rate.

  In addition, although the average particle diameter of this ion exchange resin can also be measured by using a sieve, it is preferable to adopt the catalog value of the ion exchange resin manufacturer.

  When an ion exchange resin having a small particle size with an average particle size of 0.2 to 0.3 mm is used, the surface area of the ion exchange resin involved in the adsorption removal of boron is increased with respect to the same amount of ion exchange resin. The efficiency with which the boron adsorbed on the exchange resin is transferred to the concentration chamber through the surface of the ion exchange resin is greatly improved.

  When the average particle diameter of the ion exchange resin filled in the desalting chamber 16 exceeds 0.3 mm, the effect of the present invention by using the ion exchange resin having a small particle diameter cannot be sufficiently obtained. On the other hand, an ion exchange resin having an average particle size of less than 0.2 mm may not be preferable in terms of handleability and water resistance.

  The desalting chamber 16 is usually filled with a mixed resin of an anion exchange resin and a cation exchange resin as an ion exchange resin. Therefore, it is preferable that each of the anion exchange resin and the cation exchange resin satisfy the aforementioned average particle diameter.

  The mixing ratio of the mixed resin of the anion exchange resin and the cation exchange resin to be filled in the desalting chamber 16 is anion exchange resin: cation exchange resin = 60 to 90:40 to 10, particularly 60 to 80:40 to 20 (dry weight ratio). ) Is preferable. The mixed resin filled in the desalting chamber 16 may be the same in all locations within the range of the mixing ratio described above, and is different between the inlet side and the outlet side of the desalting chamber 16 in the water flow direction. Also good. For example, in the region of 1/2 to 1/3 of the length of the water passage on the inlet side (upstream side) in the water passage direction of the desalting chamber 16, anion exchange resin: cation exchange resin = 70 to 80: 30 to 20 (dry weight ratio) of the mixed resin is filled, and the other part (exit side part) is anion exchange resin: cation exchange resin = 40 to 60:60 to 40, preferably 50 to 60:50 to A mixed resin of 40 (dry weight ratio) may be filled. By doing so, anions are effectively removed on the inlet side and an alkaline atmosphere is formed, so that carbonic acid, silica, and boron are more easily ionized, and are easily removed by an electrodeionization apparatus.

  In the electrodeionization apparatus of the present invention, in order to achieve a high boron removal rate, the concentration chamber 15 is preferably filled with an ion exchange resin. In this case, the ion exchange resin filled in the concentration chamber 15 is also dehydrated. For the same reason as the ion exchange resin filled in the salt chamber 16, an ion exchange resin having an average particle size of 0.2 to 0.3 mm is preferable.

  The ion exchange resin filled in the concentration chamber 15 is also preferably a mixed resin of an anion exchange resin and a cation exchange resin. In particular, a mixed resin of anion exchange resin: cation exchange resin = 40 to 70:60 to 30, preferably 50 to 70:50 to 30 (dry weight ratio) is preferable. The thickness of the concentration chamber 15 is preferably equal to the thickness of the desalting chamber.

  The method for producing deionized water of the present invention is a method in which water to be treated is passed through such an electrodeionization apparatus of the present invention for deionization treatment, and preferably, the demineralization chamber 16 of the electrodeionization apparatus. Water to be treated, and a part of the treated water (outflowing water from the desalting chamber), for example, about 10 to 30%, is passed through the concentrating chamber 15 in the direction opposite to the water passing direction of the desalting chamber 16. It is preferable to obtain a high boron removal rate. Moreover, as the water flow rate at that time, the water flow LV of the desalting chamber 16 is about 50 to 150 m / hr, and the water flow LV of the concentration chamber 15 is about 10 to 30 m / hr in terms of boron removal rate and treatment efficiency. It is preferable that

The current density of the electrodeionization apparatus of the water passing through the treatment of the water to be treated is 500mA / dm ² or more is preferably, for example, 1000~1500mA / dm ^2.

  The electrodeionization apparatus of the present invention is particularly preferably used as an electrodeionization apparatus provided at the subsequent stage of the RO membrane separation apparatus of the pure water production apparatus, and RO permeated water having a boron concentration of about 10 to 20 ppb from the RO membrane separation apparatus is used. By treating with the electrodeionization apparatus of the present invention, treated water having a boron concentration of 1 ppt or less can be obtained efficiently.

  Hereinafter, the present invention will be described more specifically with reference to examples.

[Example 1]
An electrodeionization apparatus (“KCDI-UPz” manufactured by Kurita Kogyo Co., Ltd.) in which a plurality of anion exchange membranes and cation exchange membranes are alternately arranged between an anode and a cathode to alternately form a concentration chamber and a desalting chamber. -020 ") was modified so that the thickness of the desalting chamber and the concentration chamber was 10 mm, and the number of desalting chambers was 50. This electrodeionization apparatus was installed so that the water flow direction of the demineralization chamber and the concentration chamber was vertical. The desalting chamber and the concentration chamber were filled with an ion exchange resin as follows. The filling height of the ion exchange resin in the desalting chamber and the concentration chamber was 60 mm, and the width was 40 mm.

  In the desalting chamber, an anion exchange resin and a cation exchange resin having an average particle size of 0.3 mm are set to an anion exchange resin: cation exchange resin ratio (dry weight ratio) of 75:25 at the top and 60:40 at the bottom. It was filled with the mixing ratio.

  The concentration chamber was filled with the anion exchange resin and the cation exchange resin at a mixing ratio of anion exchange resin: cation exchange resin = 60: 40 (dry weight ratio).

A current is passed through this electrodeionization apparatus at a current value of 10 A and a current density of 1200 mA / dm ² , water to be treated having a boron concentration of 3 ppb is circulated downwardly into the desalting chamber at LV = 2.5 m / hr, and desalted. 15% of the effluent from the chamber was circulated upward into the concentration chamber at LV = 1.0 m / hr, and the remainder was taken out as treated water.

  The obtained treated water (desalination chamber effluent) had a boron concentration of 1 ppt or less, and a boron removal rate of 99.97% could be achieved. The operating voltage was 100V.

[Comparative Example 1]
In Example 1, the thickness of the desalting chamber and the concentration chamber was 5 mm, and the number of desalting chambers was 100. In addition, as the anion exchange resin and the cation exchange resin, those having a particle diameter of 0.6 mm were used. Except for these, the treated water was passed through the electrodeionization apparatus having the same configuration as in Example 1 under the same conditions, and the boron concentration of the obtained treated water was the same as in Example 1. The operating voltage was 140V.

  From the above results, it was confirmed that according to Example 1, boron can be sufficiently removed even if the number of cells is reduced. Moreover, according to Example 1, it was recognized that the required voltage for driving | running with the same electric current fell.

11 Anode 12 Cathode 13 Anion Exchange Membrane 14 Cation Exchange Membrane 15 Concentration Chamber 16 Desalination Chamber

Claims (4)

A concentration chamber and a desalination chamber are partitioned by an ion exchange membrane between the anode and the cathode,
Concentrated water is circulated to the concentrating chamber, raw water is circulated to the desalting chamber as treated water, taken out as production water,
In the electrodeionization apparatus in which part of the production water is circulated in the concentration chamber as the concentrated water in the flow direction and the countercurrent direction of the demineralization chamber,
The desalting chamber has a thickness of 10 to 20 mm;
An electrodeionization apparatus characterized in that the ion exchange resin filled in the desalting chamber has an average diameter of 0.2 to 0.3 mm.   2. The electrodeionization apparatus according to claim 1, wherein the ion exchange resin filling height of the demineralization chamber is 40 to 80 mm and the width is 30 to 60 mm. In Claim 1 or 2, the desalting chamber is filled with a mixed resin of an anion exchange resin and a cation exchange resin,
The ratio (dry weight ratio) of the anion exchange resin in the mixed resin in the desalting chamber is 70 to 80% on the desalting chamber inlet side and 40 to 60% on the desalting chamber outlet side. Electrodeionization equipment.   The manufacturing method of deionized water using the electrodeionization apparatus of any one of Claim 1 thru | or 3.

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