JP2019111467A - Electric deionization system - Google Patents

Abstract

To provide an electric deionization system constituted of a plurality of electric deionization devices connected in series, with a part of product water at least from an electric deionization device on the last stage being made to counter-currently flow to a concentration chamber, which system is capable of reducing a feed water pressure to a desalination chamber of an electric deionization device on the first stage.SOLUTION: Product water of an electric deionization device 1 on the front stage side is introduced into a desalination chamber 16B of an electric deionization device 2 on the rear stage side as water to be treated, and product water from the desalination chamber 16B of the electric deionization device 2 on the last stage is introduced into a tank 22. A part of product water present in the tank 22 is made to flow into a concentration chamber 15B from one side thereof near the outlet of the adjacent desalination chamber and is made to flow out from another side thereof near the inlet of the adjacent desalination chamber, as concentrated water by a pump 23 and a pipe 24.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an electrodeionization system, and more particularly to an electrodeionization system in which electrodeionization devices are provided in multiple stages.

  The electrodeionization apparatus generally forms a desalting chamber and a concentration chamber by alternately arranging a cation exchange membrane and an anion exchange membrane between the cathode and the anode, and forming a section with the cation exchange membrane and the anion exchange membrane, The deionization chamber and the concentration chamber are filled with an ion exchange resin.

  When the raw water is passed to the deionization compartment of the electrodeionization apparatus and the concentrated water is passed to the concentration compartment, and an electric current is applied between the cathode and the anode, the ions pass through the ion exchange resin from the demineralization compartment and the anion exchange membrane and cation Transfer to the concentration chamber through the exchange membrane. Thereby, deionized water (pure water) flows out from the deionization chamber. Concentrated water having ions concentrated flowing in the concentration chamber is discarded or partially recycled. Such an electrodeionization apparatus is used as a pure water production apparatus used in various industries, for example, production of semiconductor chips, operation of a power plant, petrochemical applications, pharmaceutical production and the like.

  In recent years, the requirement level for ultrapure water production technology has been increased, and for boron, a severe water quality of, for example, 1 ppt or less has been required.

  An electrodeionization device with a high boron removal rate (for example, “KCDI-UPz” manufactured by Kurita Kogyo Co., Ltd., etc.) in which the RO membrane separation device and the electrodeionization device are combined is commercially available. Even in the electrodeionization device of the above, the boron removal rate is about 99.9%. Therefore, for example, treated water with a boron concentration of about 20 ppb is treated with an RO membrane separation device to obtain RO permeated water with a boron concentration of about 10 ppb, which is treated with an electrodeionization device with a boron removal rate of 99.9%. Even then, the boron concentration of the resulting treated water (deionized water) is only 10 ppt, and treated water having a boron concentration of 1 ppt or less can not be obtained.

  According to Patent Document 1, in order to improve the quality of treated water, part of the production water from the demineralization chamber may be diverted to the concentration chamber (flow in the opposite direction to the flow direction of the deionization chamber) Have been described.

  Patent Document 2 describes that a treated water boron concentration of 1 ppt or less is achieved by passing water through two electrodeionization apparatuses in series. Also in Patent Document 2, in the concentration chamber of each electrodeionization device, part of the production water from the deionization chamber is directed to flow.

JP 2002-20506 A Unexamined-Japanese-Patent No. 2006-51423

  In the electrodeionization system in which a plurality of electrodeionization devices are installed in series, when part of the production water is directed to the concentrating chamber of the electrodeionization device of the last stage, the electrodeionization device of the last stage is dewatered A back pressure valve is provided on the product water line from the salt chamber to apply a back pressure, and a portion of the product water is separated from the product water line and introduced into the concentration chamber of the electrodeionization device at the last stage. For this reason, it is necessary to increase the inlet pressure of the deionization chamber of the electrodeionization apparatus by this back pressure. In order to increase the inlet pressure, it is necessary to increase the head of the water pump. In addition, if the inlet pressure is increased, the electrodeionization device is likely to leak. In addition, when part of the production water is circulated to the concentration chamber, the pressure difference between the inlet of the demineralization chamber and the outlet of the adjacent concentration chamber becomes large, and breakage of the ion exchange membrane, or from the deionization chamber to the concentration chamber There is also a risk of leaks.

  In the electrodeionization system according to the present invention, a plurality of electrodeionization apparatuses are connected in series, and at least the electrodeonion apparatus in the final stage distributes part of the produced water from the deionization chamber to the concentration chamber. An object of the present invention is to provide an electrodeionization system capable of reducing the feed water pressure to the deionization chamber of the first electrodeionization apparatus.

  In the electrodeionization system of the present invention, between the anode and the cathode, a concentration chamber and a desalting chamber are partitioned by an ion exchange membrane, concentrated water is circulated in the concentration chamber, and treated water is introduced into the desalting chamber A plurality of electrodeionization devices to be extracted as production water, and the production water of the electrodeionization device on the front side is introduced as the water to be treated to the deionization chamber of the electrodeionization device on the rear side, In the electrodeionization apparatus, a portion of the product water from the demineralization chamber is made to flow from the side near the outlet of the deionization chamber to the concentration chamber as concentrated water by the supply line, and it flows out from the side near the inlet of the deionization chamber An electrodeionization system that is configured to operate, wherein the supply line is provided with a pump.

  The electrodeionization system according to one aspect of the present invention comprises a tank for receiving the produced water from the deionization chamber of the last-stage electrodeionization apparatus, and the supply line carries out the water in the tank as the last-stage electricity. It is characterized in that it is provided to be supplied to the concentration chamber of the deionization apparatus.

  The electrodeionization system according to one aspect of the present invention is characterized in that a supply line is provided in each of the concentration chambers of all the electrodeionization devices so as to counterflow the water in the tank.

  In the electrodeionization system of the present invention, it is not necessary to apply a back pressure for passing a part of the production water to the concentration chamber, and the inlet pressure in the deionization chamber of the electrodeionization apparatus is reduced. It becomes possible.

  In addition, the differential pressure between the demineralization chamber inlet and the concentration chamber inlet can be reduced, and the membrane breakage and the leak from the deionization chamber to the concentration chamber can be prevented.

It is a typical sectional view of an electrodeionization device used for an electrodeionization system concerning an embodiment. It is a block diagram of the electrodeionization system which concerns on embodiment. It is a block diagram of the electrodeionization system which concerns on embodiment. It is a block diagram of the electrodeionization system which concerns on embodiment. It is a block diagram of the electrodeionization system which concerns on a prior art example.

  An example of a structure of the electrodeionization apparatus used for the electrodeionization system which concerns on FIG. 1 at embodiment is shown. In addition, RO (reverse osmosis) treated water etc. are illustrated as raw water processed with this apparatus.

  In this electrodeionization apparatus, a plurality of anion exchange membranes (A membrane) 13 and cation exchange membranes (C membrane) 14 are alternately arranged between the electrodes (anode 11 and cathode 12), and a concentration chamber 15 and a desalting chamber are provided. The deionization chamber 16 is filled with an anion exchanger composed of ion exchange resin, ion exchange fiber, graft exchanger or the like and a cation exchanger in a mixed or multilayered form. Further, 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 into the demineralization chamber 16, from which product water is taken out. A portion of the produced water is passed through the concentration chamber 15 in a countercurrent flow direction opposite to the direction of water flow in the deionization chamber 16, and the outflow water of the concentration chamber 15 is discharged out of the system. That is, in this electrodeionization apparatus, the concentration chamber 15 and the desalting chamber 16 are alternately arranged side by side, and the inlet of the concentration chamber 15 is provided on the product water removal side of the desalting chamber 16 The outlet of the concentration chamber 15 is provided on the raw water inlet side of 16. Also, part of the production water is fed to the inlet side of the anode chamber 17, and 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 as drainage. It is discharged outside.

  Thus, by passing the production water through the concentration chamber 15 in a countercurrent flow with the deionization chamber 16, the concentration of the concentrated water in the concentration chamber 15 becomes lower toward the production water take-out side, and concentration diffusion is achieved. The influence on the deionization chamber 16 is reduced, and the removal rate of ions such as boron can be increased.

  The electrodeionization system of the present embodiment has two stages of the electrodeionization apparatus shown in FIG. 1 installed in series. An example of this electrodeionization system is shown in FIG. The electrodeionization system of FIG. 2 connects the first electrodeionization device 1 and the second electrodeionization device 2 in series to deionize the raw water in multiple stages. In this electrodeionization system, the entire amount of raw water is supplied to the deionization chamber 16A of the first electrodeionization apparatus 1 to become primary product water.

  A back pressure valve 20 is provided in a line for supplying product water from the deionization chamber 16A to the deionization chamber 16B in order to flow part of primary production water to the concentration chamber 15A. A portion of the primary production water branches from the upstream side of the back pressure valve 20, passes through the concentration chamber 15A in a countercurrent flow manner, and is discharged as concentrated drainage. The remainder of the primary production water is passed through the deionization chamber 16B of the second electrodeionization device 2 to become secondary production water.

  The secondary production water is introduced into the production water tank 22 through the pipe 21. A part of the production water in the tank 22 is supplied to the concentration chamber 15B of the second electrodeionization device 2 through the pump 23 and the pipe 24, and is water-flowed in a countercurrent to the concentration chamber 15B. It flows out as secondary concentrated water. The secondary concentrated water is returned to, for example, raw water.

  According to this water flow system, it is not necessary to provide the pipe 21 with the back pressure valve 27 (FIG. 5 described later) for passing the produced water in the concentration chamber 15B of the second electrodeionization device 2. Therefore, the inlet pressure of the deionization chambers 16A and 16B of the electrodeionization devices 1 and 2 can be lowered by the pressure loss of the back pressure valve 27.

  In FIG. 2, part of the production water of the first electrodeionization device 1 is circulated to the concentration chamber 15A, but as shown in FIG. 3, the concentration chamber of the first electrodeionization device 1 is Alternatively, the produced water in the tank 22 may be circulated by the pipe 25. In this case, the back pressure valve 20 of the piping between the deionization chambers 16A and 16B is unnecessary. Therefore, the inlet pressure of the deionization chamber 16A of the first electrodeionization device 1 can be further lowered by the pressure loss of the back pressure valve 20.

  In the present invention, as shown in FIG. 4, raw water may be passed through the concentration chamber 15A of the first electrodeionization device 1 in parallel flow in the deionization chamber.

  FIG. 5 shows an electrodeionization system of Comparative Example 1 described later. In this electrodeionization system, a part of the production water of the second electrodeionization device 2 is directly supplied to the concentration chamber 15B without passing through the tank 22 by the pipe 26 branched from the pipe 21 and countercurrent Water is flowing in a temporary manner. In order to separate a part of the production water from the deionization chamber 16B from the pipe 21, the pipe 21 is provided with a back pressure valve 27 downstream of the branch point of the pipe 26, and a back pressure is applied. The pressure at the outlet of the deionization chamber 16B is increased by the amount of back pressure generated by the back pressure valve 27, and as a result, the inlet pressure of the deionization chambers 16A and 16B of the electrodeionization devices 1 and 2 is increased. Is required. As a result, the problems described in the section of the problem to be solved by the invention tend to occur.

  In the above description, the electrodeionization devices are installed in two stages in series, but may be installed in three or more stages in series.

  Hereinafter, Examples and Comparative Examples will be described. In the following examples and comparative examples, water (boron concentration: 3.5 ppt, water temperature: 20 ° C.) obtained by RO treatment of city water was used as raw water.

Example 1
An electrodeionization apparatus (IONPURE (registered trademark) VNX 55EX-2 manufactured by EVOQUA WATER TECHNOLOGIES) was installed in two stages in series as shown in FIG. Concentrating chamber flow rate is preceding electrodeionization apparatus ^{1 m} 3 / Hr, subsequent electrodeionization apparatus 0.5 m ³ / Hr. The results (pressures at points P _{1 to} P _{4 in} FIG. 2) are shown in Table 2.

Comparative Example 1
Water was passed through the electrodeionization system under the same conditions as in Example 1 except that the flow was as shown in FIG. The results are shown in Table 2.

<Discussion>
In Example 1, the pressure loss of the piping 21 from the second electrodeionization apparatus 2 to the production water tank 22 was 0.10 MPa. Since the concentration compartment 15B was set to passing water through the pump 23 the product water from the tank 22, the pressure P ₃ of the desalination chamber outlet may only pressure pipe component to treated water tank 22. Therefore the pressure _{P 3} of the desalination chamber outlet of electrodeionization apparatus 2 can be lowered and 0.10 MPa, the pressure _P 1 of the desalination chamber inlet of electrodeionization apparatus 1, it is possible to lower the _{P 2.} By lowering the pressures P ₁ and P ₂ at the inlet of the demineralization chamber, the risk of breakage and water leakage of the electrodeionization devices 1 and 2 can be reduced. Although concentrating chamber inlet pressure P ₄ is lower than the pressure P ₃ of the desalination chamber outlet principle, in Example 1, from where the water flow of product water in the tank 22, the concentration chamber inlet pressure P ₄ de even slightly larger than the salt chamber outlet pressure P _3, no problem in quality surface of the product water from the electrodeionization apparatus 2.

On the other hand, in Comparative Example 1, since the total pressure loss of the piping 21 and the back pressure valve 27 from the second-stage electrodeionization device 2 to the production water tank 22 is 0.20 MPa, the deionization chamber of the electrodeionization device 2 The outlet pressure had to be 0.20 MPa. Therefore the inlet pressure _{P 1} of the electrodeionization apparatus 1 is required at least 0.40 MPa. The pressure loss during water flow is further increased by the length of the connection piping, so the inlet pressure P1 of the electrodeionization device ₁ is further increased. As described above, by the inlet pressure P ₁ increases, increasing the risk of equipment damage and it by water leakage.

1, 2 Electrodeionization equipment 15, 15A, 15B Concentration chamber 16, 16A, 16B Deionization chamber 23 Piping (supply line)
24 pumps

Claims (3)

Between the anode and the cathode, an ion exchange membrane separates a concentration chamber and a desalting chamber,
A plurality of electrodeionization devices are provided, in which concentrated water is circulated in the concentration chamber and water to be treated is introduced into the deionization chamber and taken out as product water,
Production water of the electrodeionization device on the front side is introduced into the deionization chamber of the electrodeionization device on the rear side as treated water,
At least the last stage of the electrodeionization apparatus allows part of the product water from the demineralization chamber to flow as concentrated water from the side close to the outlet of the deionization chamber as concentrated water by the supply line and is close to the inlet of the deionization chamber In an electrodeionization system configured to flow out of the
An electrodeionization system characterized in that a pump is provided in the supply line. A tank for receiving the produced water from the demineralization chamber of the last-stage electrodeionization device,
The electrodeionization system according to claim 1, wherein the supply line is provided to supply the water in the tank to the concentration chamber of the last electrodeionization apparatus.   3. The electrodeionization system according to claim 2, wherein a supply line is provided in each of the concentration chambers of all the electrodeionization apparatuses so as to circulate water in the tank.

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