Deionized water or high purity water producing method and appara

Details Deionized water or high purity water producing method and appara Deionized water or high purity water producing method and appara

1996-01-24

1998-09-22

Cintins, Ivars

Liquid purification or separation

Processes

Ion exchange or selective sorption

210202, 2102572, 210266, 210269, 210290, 210900, C02F 900

Patent

active

058110127

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to a method for producing deionized water or high purity water, and to an apparatus for producing the same. It also relates to a method and apparatus for producing deionized water or high purity water wherein the boron concentration is largely reduced. This water is used for example in electronics industries such as the semiconductor manufacturing industry, or related fields.


BACKGROUND OF THE INVENTION

This invention will be described as applied to the production of deionized water or high purity water, which is used in the electronics industry. In this field, in addition to the increasingly stringent requirements for the cleanliness of the production machinery, gases and reagents used in manufacturing processes, higher and higher purity water (and in some cases, hyperpurity water) is required as the circuitry density of microelectronics devices becomes high. In this way, the yields of these products are maintained and enhanced. In the future, such demand for water of higher purity will continue. Consequently, attempts are now being made to remove fine particulates, colloids and minute amounts of other impurities which had previously been ignored in earlier deionized water producing processes. Boron, for example, is generally present in well water and river water used as feed water in high purity water producing plants only to the extent of several tens of ppb. Since it is present in far lower levels than other impurities, it tended to be ignored, and was not included in the quality analysis items of water produced by these systems. However, with the advances made in water purification technology, it has become possible to reduce impurities to the level of ppt, but boron is now regarded as one of those impurities that are more difficult to remove using the conventional deionized water and high purity water producing systems.
This problem of boron will now be discussed with reference to the conventional high purity water purification system shown as an example in FIG. 17.
In FIG. 17, 1 is a pretreatment unit for removing suspended solids and some of the organic matter from feed water such for example as industrial water. Pretreated water, after passing through a filtered water tank 2, is sent to a two bed ion exchange deionization system (two-bed with a degasifier type) 3 comprising a cation exchange resin column (K column) 31, a decarbonating column 32 and an anion exchange resin column (A column) 33 where ionic impurities are removed. 4 is a demineralized water storage tank for storing treated water after removal of these ionic impurities.
5 is an RO (Reverse Osmosis) apparatus comprising a reverse osmosis membrane which removes impurities such as residual inorganic ions, organic matter and minute particles in the treated water from which most of the impurity ions have been removed by the two bed ion exchange deionized system 3. 6 is a tank for storing RO treated water.
7 is a vacuum degasifier which removes dissolved gases such as dissolved oxygen and carbon dioxide gas in the treated water from the RO apparatus 5. 8 is a regenerative type mixed bed ion exchanger which produces primary deionized water. This water is supplied to a primary deionized water tank 9.
10 is an ultra-violet oxidizer wherein primary deionized water from the tank 9 is irradiated by ultra-violet rays so as to cause oxidative decomposition of organic matter and to kill bacteria in the primary deionized water. 11 is a non-regenerative type mixed bed cartridge polisher which is designed to remove last traces of impurity ions from the deionized water which has already been refined to a high level.
From the effluent of this cartridge polisher 11, minute particles are removed by an ultrafiltration apparatus 12 comprising an ultrafiltration membrane, and the resulting high purity water is supplied to points of use 13 where it is used.
However, when the water quality of the high purity water produced by the above system was analyzed at points of use 13, it was found that the concentration

REFERENCES:
patent: 2813838 (1957-11-01), Lyman et al.
patent: 3567369 (1971-03-01), Chemtob
patent: 3870033 (1975-03-01), Faylor et al.
patent: 5250185 (1993-10-01), Tao et al.

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