JP2006255651A - Pure water producing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pure water producing system which prevents variation in water quality of obtained pure water without using a heat exchanger. <P>SOLUTION: Raw water is filtered by an activated carbon filtration device 1, passed through a feed water pump 2 for a reverse osmosis membrane device, and sent to a reverse osmosis membrane device 3 to be desalinated. The desalinated water in the reverse osmosis membrane device 3 is brought into contact with a water quality sensor 4 equipped with a water temperature sensor 4a, thereafter sent to an electric deionization device 5 to be electrically deionized. The electrically deionized water is brought into contact with a water quality sensor 6 equipped with a water temperature sensor 6a to be extracted as a treated water, i.e. pure water. A sensing signal from the water temperature sensor 6a is input to a current control circuit 8 of the electric deionization device, and controls applied voltage and/or energizing current to the electric deionization device 5 so that electric conductivity or specific resistance of the treated water from the electric deionization device 5 becomes constant. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pure water production apparatus, and more particularly to a pure water production apparatus in which raw water is treated by a reverse osmosis membrane apparatus and an electrodeionization apparatus.

As a system for producing pure water by treating recovered water from industrial water, city water, well water, or semiconductor manufacturing processes, etc., an apparatus that treats raw water with a reverse osmosis membrane device and then with an electrodeionization device is well known. (For example, Patent Documents 1 and 2 below).
JP 2003-1259 A JP 2001-29752 A

  In a pure water production apparatus that produces pure water by treating raw water with a reverse osmosis membrane apparatus and an electrodeionization apparatus, if the temperature of the water treated by the electrodeionization apparatus fluctuates, the treated water from the electrodeionization apparatus The water quality varies.

  Conventionally, in order to prevent fluctuations in water quality due to fluctuations in the water temperature, a heat exchanger is installed on the upstream side of the electrodeionization apparatus so that the temperature of the inflow water to the electrodeionization apparatus is constant. However, when such a heat exchanger is provided, the equipment cost of a pure water manufacturing apparatus will increase.

  An object of this invention is to provide the pure water manufacturing apparatus by which the quality change of the pure water obtained is prevented, without using a heat exchanger.

  The pure water production apparatus of the present invention (Claim 1) is a pure water production apparatus for producing pure water by treating raw water with a reverse osmosis membrane device and then treating it with an electrodeionization device. Alternatively, a detection means for the temperature of the pure water obtained by the treatment, and an applied voltage to the electrodeionization device and / or so that the quality of the pure water produced is constant based on the water temperature detected by the detection means. Alternatively, a control means for controlling the energization current is provided.

  The pure water production apparatus according to claim 2 is characterized in that, in claim 1, the water temperature detecting means is also used as a temperature correction detector of the produced pure water conductivity meter or resistivity meter. To do.

  The pure water production apparatus of the present invention detects the water temperature of raw water, water in the middle of processing, or pure water obtained by processing, and based on this detected water temperature, applies an applied voltage and / or current to the electrodeionization device. By controlling, the quality of pure water is made constant. By controlling the applied voltage and / or energization current of the electrodeionization device in this way, fluctuations in the quality of pure water can be prevented, so there is no need to provide a heat exchanger on the front side of the electrodeionization device. Equipment costs for water production equipment are reduced.

  In particular, it is possible to further reduce the equipment cost by using a conductivity meter for detecting the water quality of pure water or a temperature correction detector of a specific resistance meter as the water temperature detecting means.

  Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a system diagram of a pure water production apparatus according to an embodiment.

  The raw water is filtered by the activated carbon filtration device 1, then sent to the reverse osmosis membrane device 3 through the reverse osmosis membrane device (shown as RO in FIG. 1) feed water pump 2, and desalted. . The water demineralized by the reverse osmosis membrane device 3 is brought into contact with the water quality sensor 4 provided with the water temperature sensor 4a, and then sent to the electrodeionization device 5 and subjected to electrodeionization treatment. This electrodeionized treated water is taken out as treated water (pure water) after contacting the water quality sensor 6 having the water temperature sensor 6a.

  The detection signal of the water temperature sensor 4a is input to the pump control circuit 7 and controls the discharge amount of the pump 2 so that the amount of osmotic water in the reverse osmosis membrane device 3 is constant even when the water temperature changes.

  The detection signal of the water temperature sensor 6a is input to the electrodeionization device energization control circuit 8, and the electrodeionization device 5 so that the conductivity or specific resistance of the treated water from the electrodeionization device 5 is constant. The applied voltage and / or the energizing current is controlled. Specifically, when the water temperature decreases, the applied voltage and / or energization current to the electrodeionization device 5 is increased, and when the water temperature decreases, the application voltage and / or energization current to the electrodeionization device 5 is decreased, The conductivity or specific resistance of the permeated water of the deionizer 5 is made constant.

  Thus, according to this pure water manufacturing apparatus, the quality of the treated water of the electrodeionization apparatus 5 is controlled by controlling the applied voltage and / or energization current to the electrodeionization apparatus 5 based on the detected water temperature of the water temperature sensor 6a. Since the fluctuation is prevented, it is not necessary to provide a heat exchanger on the front side of the electrodeionization apparatus 5, and the equipment cost of the pure water production apparatus is reduced.

  In particular, in this embodiment, the temperature of the demineralized water from the reverse osmosis membrane device 3 is detected by the water temperature sensor 4a, and the discharge rate of the pump 2 is controlled based on the detected temperature to prevent fluctuations in the amount of demineralized water. Therefore, fluctuations in the amount of pure water produced by the pure water production apparatus are prevented.

  In addition, in this embodiment, since the water temperature sensors 4a and 6a for correcting the temperature of the water quality sensors 4 and 6 are used as the water temperature sensors, there is no need to newly install a water temperature sensor, and the pure water production apparatus can be used also by this. The equipment cost is further reduced.

  In the present invention, raw water to be treated is industrial water, city water, well water or manufacturing process recovered water, for example, washing waste water of a manufacturing process such as semiconductor or liquid crystal. It is also good. When manufacturing process recovered water such as semiconductor manufacturing recovered water is used as raw water, and the organic matter (TOC) concentration of the recovered water is high, TOC removal such as biological treatment means, heating means, catalytic decomposition means, etc. You may process beforehand with an apparatus.

  Moreover, it is preferable to pre-process raw water, such as industrial water, city water, and well water, with the activated carbon filtration apparatus 1 etc. like this embodiment as needed. In addition, you may use an ultrafiltration (UF) membrane apparatus, a microfiltration (MF) membrane apparatus, etc. as things other than an activated carbon filtration apparatus.

The raw water or its pretreated water (or TOC removal treated water) may be treated with a deoxygenating apparatus after adding a mineral acid such as HCl and H ₂ SO ₄ to adjust the pH to 4-6.

  Here, the adjusted pH is performed to remove carbon dioxide together with oxygen, and reduces the load on the desalting apparatus in the subsequent stage. As this deoxygenating device, a membrane degassing device, a vacuum degassing device, an air gas degassing device or the like can be used. When the pH is acid and the deoxygenation is performed by the deoxygenation device, an alkali such as NaOH is added to adjust the pH to 7-8.

  There is no restriction | limiting in particular as a film | membrane of a reverse osmosis membrane apparatus, Membranes, such as a polysulfone, polyamide, a polyvinyl acetate, can be used.

As the electrodeionization apparatus 5, a plurality of anion exchange membranes and cation exchange membranes are alternately arranged between an anode chamber having an anode and a cathode chamber having a cathode to alternately form a concentration chamber and a desalting chamber. In addition, a desalting chamber filled with an ion exchanger such as a mixed resin of an anion exchange resin and a cation exchange resin or an ion exchange fiber can be used. The applied voltage of the electrodeionization device 5 is preferably about 10 to 100 V, particularly about 30 to 70 V, and the energization current density is preferably about 4 to 20 A / m ² , particularly about 6 to 10 A / m ² .

  The deionized water of the electrodeionization device 5 is treated with a second reverse osmosis membrane device or an ultrafiltration membrane device (not shown) as necessary to further remove residual traces of TOC and silica. The purity may be increased.

  In the present invention, it is preferable to return the concentrated water of the electrodeionization device 5 to the inlet side of the reverse osmosis membrane device 3 and circulate it in terms of improving the water recovery rate. Also in this case, the water supply to the electrodeionization device 5 is sufficiently improved in quality by the treatment by the reverse osmosis membrane device 3, so the electrodeionization device concentrated water is returned to the inlet side of the reverse osmosis membrane device 3. There is no problem of deterioration of treated water quality.

It is a systematic diagram which shows embodiment of the pure water manufacturing apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Activated carbon filtration apparatus 3 Reverse osmosis membrane apparatus 5 Electrodeionization apparatus 7 Pump control circuit 8 Electrodeionization apparatus electricity supply control circuit

Claims (2)

In a pure water production apparatus that produces pure water by treating raw water with a reverse osmosis membrane device and then treating with an electrodeionization device,
Means for detecting the temperature of raw water, water in the middle of treatment or pure water obtained by treatment;
And a control means for controlling the applied voltage and / or current applied to the electrodeionization device so that the quality of the pure water produced is constant based on the water temperature detected by the detection means. Pure water production equipment.   2. The pure water production apparatus according to claim 1, wherein the water temperature detection means is also used as a temperature correction detector of a manufactured pure water conductivity meter or resistivity meter.

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