JP2001353498A - Production method of pure water, and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pure water production method in which stable operation is obtained without installing two stages of RO devices at a front stage of an EDI and highly pure water is efficiently obtained, and to provide its device. SOLUTION: In the pure water production method, raw water is flowed into a reverse osmosis device to produce pure from city water and the permeated water is flowed into Na type cation exchange resin, and then later it is flowed into an electric regeneration type ion exchange device. Also this device is connected a first stage of the reverse osmosis device 4, a Na type cation exchange device 5 and the electric regeneration type ion exchange device 6 in this order.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing pure water, and more particularly to a method for producing pure water capable of preventing scale, which is a problem of an electric regeneration type ion exchange apparatus (hereinafter abbreviated as EDI). And an apparatus.

[0002]

2. Description of the Related Art An apparatus for producing pure water removes ions and organic substances in water.
The system configuration is a combination of devices (abbreviated as RO). FIG. 2 shows an example of a conventional pure water production apparatus. This deionized water production device is equipped with a deaeration tower 1 for removing dissolved oxygen in city water,
Raw water tank 2, activated carbon tower 3, 2 for removing residual chlorine and organic matter
A stage RO device 4 and EDI 6 are provided. EDI is composed of a plurality of anion exchange membranes and cation exchange membranes arranged alternately to form a concentrated water chamber and a treated water chamber alternately, and to fill the treated water chamber with a mixture of an anion exchange resin and a cation exchange resin. so,
It has a structure combining ion exchange and electrodialysis. This device has both an action of trapping sodium and chloride ions in water with the ion exchange resin and an action of transferring trapped ions to the concentrated water chamber by electrolysis. That is, the EDI electrically regenerates the resin simultaneously with the ion exchange. For this reason, unlike the ion exchange resin, there is a feature that a chemical regeneration is not required and high-purity water can be obtained.

[0003] EDI has a treated water chamber and a concentrated water chamber separated by an ion exchange membrane. Since a large amount of ions are concentrated in the concentrated water, there is a problem that scale is easily generated in the ion exchange membrane. . Therefore, it is important for EDI to keep the scale components such as calcium and magnesium at 10 ppb or less. In order to remove the scale components to a trace concentration as described above, there is a limit to the ion rejection ratio of RO, so it is necessary to use a so-called two-stage RO facility in which ROs are arranged in two stages as a pretreatment for EDI. is there. However, as a pre-treatment of EDI, it is necessary to remove trace scale components such as calcium and magnesium.
The stage RO device simply doubles the number of elements and increases the cost in terms of facilities and operation management, which is not a good idea.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art, to enable stable operation without installing a two-stage RO device in front of EDI, and to achieve high-purity pure water. It is an object of the present invention to provide a pure water production method and apparatus capable of efficiently obtaining water.

[0005]

In order to solve the above-mentioned problems, the present invention provides an EDI system in which calcium and magnesium remaining in permeated water are removed by a first-stage RO apparatus with a cation-exchange resin in a subsequent stage. This is to make it possible to obtain the required water quality as supply water. As a means for this,
A Na-type cation exchange resin is installed between the first-stage RO device and EDI, and scale components that cannot be completely removed by the first-stage RO device are replaced with Na to selectively remove scale components. Things. Placing the cation exchange resin in front of the RO device can also remove scale components, but with such a device configuration, the frequency of resin regeneration increases in proportion to the calcium and magnesium concentrations in the raw water. However, there is a disadvantage that efficient operation cannot be performed.

According to the method for producing pure water of the present invention, in order to produce pure water from city water, raw water is passed through a reverse osmosis device, the permeated water is passed through a Na-type cation exchange resin, and then the electricity is regenerated. It is characterized by passing water through a type ion exchange device. Further, the apparatus for producing pure water according to the present invention includes a one-stage reverse osmosis device 4, N
The a-type cation exchange device 5 and the electric regeneration type ion exchange device 6 are connected in this order.

[0007]

Next, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a system diagram of a pure water production apparatus showing one embodiment of the present invention. Raw water first flows into the degassing tower 1 by aeration with nitrogen gas as pretreatment, and is degassed. In the degassing tower 1, dissolved oxygen in raw water is removed by nitrogen gas aeration. The effluent from the degassing tower 1 is supplied to the raw water tank 2
, And then flow into the activated carbon filtration tower 3 to remove residual chlorine and organic substances, and then send the water to the one-stage RO device 4.
In the RO device 4, the amount of ions in the water is reduced to about 1/100, and calcium and magnesium in the permeated water are reduced by more than ten pp.
b.

In the present invention, the permeated water from the one-stage RO apparatus 4 is sent to the Na-type cation exchange resin tower 5. Since this cation exchange resin is of the Na type, it has an action of replacing divalent cations such as calcium and magnesium in water with Na, and other ions flow out of the resin tower without being replaced. By arranging the Na-type cation exchange resin at the subsequent stage of the RO device in this way, it is possible to selectively remove scale components such as calcium and magnesium, and to obtain water quality required as EDI supply water.

An experiment for producing pure water was conducted using the pure water producing apparatus of the present invention shown in FIG. 1, and the quality of the produced pure water was measured. The results are shown in Table 1. Further, pure water was produced under the same conditions except that the conventional pure water producing apparatus using the two-stage RO apparatus shown in FIG. 2 was used, and the quality of the obtained pure water is shown in Table 1.
As is evident from the results shown in Table 1, the effluent of the conventional pure water production apparatus was 10 pp of calcium and magnesium.
In contrast, the effluent of the apparatus of the present invention was less than 1 ppb for both calcium and magnesium.

[0010]

[Table 1]

The pure water producing apparatus of the present invention has a
When water was passed continuously for hours, no scale formation was observed in the EDI, stable production of pure water was possible, and the number of regenerations of the Na-type cation exchange resin in the former stage was only two. The frequency of regeneration of this resin is equivalent to about 1/50 of that when raw water is passed directly, maintenance is extremely easy, and the disposal cost of the amount of waste liquid for regeneration can be greatly reduced.

[0012]

According to the method and the apparatus for producing pure water according to the present invention, an expensive and heavy two-stage RO apparatus can be installed without using an expensive and heavy RO apparatus.
It is possible to use the RO device of the stage and obtain the required water quality as EDI supply water, and long-term stable operation of EDI becomes possible.
It was found that high-purity pure water could be obtained. Further, the frequency of regenerating the resin in the cation exchange resin tower provided between the RO device and the EDI can be significantly reduced, and the disposal cost of the amount of regenerated waste liquid can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a system diagram of an apparatus for producing pure water showing one embodiment of the present invention.

FIG. 2 is a system diagram of a conventional pure water production apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Deaeration tower 2 Raw water tank 3 Activated carbon filtration tower 4 RO apparatus 5 Cation exchange resin tower 6 EDI

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 9/00 504 C02F 9/00 504E 1/42 1/42 B 1/44 1/44 H 1/469 5/00 610C 5/00 610 610Z 620B 620 1/46 103 F term (reference) 4D006 GA03 KB01 KB11 KB12 KB17 PA02 PB27 PC03 4D025 AA03 AB19 BA08 BB02 BB07 CA01 CA05 DA01 DA03 DA05 DA06 4D061 DA02 DB18 EA09 FA08 FA03

Claims (2)

[Claims] 1. In order to produce pure water from city water, raw water is passed through a reverse osmosis device, the permeated water is passed through a Na-type cation exchange resin, and then passed through an electric regeneration type ion exchange device. A method for producing pure water. 2. An apparatus for producing pure water, comprising a single-stage reverse osmosis unit 4, a Na type cation exchange unit 5, and an electric regeneration type ion exchange unit 6 connected in this order.