Concentrating evaporators – Closed evaporating chambers – Liquid traps or separators
Patent
1988-11-04
1991-07-02
Bascomb, Wilbur
Concentrating evaporators
Closed evaporating chambers
Liquid traps or separators
159 473, 159DIG12, 159DIG27, 159DIG28, 55158, 202161, 202197, 202200, 203 11, 203 40, 203DIG14, 210640, 252632, B01D 6136, C02F 104
Patent
active
050282980
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a waste water concentrator, a waste water disposal plant and a waste water concentrating method, and especially to a waste water concentrator, a waste water disposal plant and a waste water concentrating method which are suitable for removing a water content from waste water with a high decontamination factor.
BACKGROUND ART
A waste water concentrator which is usually used in a nuclear power station, for instance, is constituted by an evaporator 1 and a condenser 4 as shown in FIG. 12. To the evaporator 1, a heater 14 heating waste water by using station-service heating steam 15 is connected via a circulating pump 13. Steam generated through evaporation in the evaporator 1 is sucked by an eductor 5 and brought to a condenser 4 to be turned into condensed water. The waste water is introduced into a concentrator through a valve 7 on the supplying tank side. Concentrated waste water containing solid-state wastes, which is obtained through concentration in the evaporator 1, on the other hand, is introduced into a subsequent process through a take-out valve 8. Although a vapor-liquid separator is provided in the upper part of the evaporator 1, the rate of removal of mist is low and therefore the mist is often transferred onto the condenser side.
In recent years, a method has been contrived wherein concentration itself is conducted by a membrane and thereby a high decontamination factor is obtained. For instance, a method has been proposed, as described in the Official Gazette on Japanese Patent Laid-Open No. 164195/1986, wherein, a hydrophobic polymer porous membrane allowing steam to permeate but not water to do is employed, nuclear power station waste water at a prescribed temperature is made to contact directly this porous membrane on one side thereof, steam is generated from this water and made to permeate onto the other side of said porous membrane, the steam permeating therethrough is cooled down to be condensed, and thus the waste water is concentrated, while deionized water is collected efficiently. This method is not accompanied by the problem of the transfer of mist onto the condensed water side, which occurs when the evaporator and the condenser are employed.
Out of the above-described prior arts, the method using the combination of the evaporator and the condenser has an inferior efficiency in removing metal ions and inorganic substances existing in the mist, and consequently the decontamination factor (hereinafter mentioned as DF) is improved thereby only to about 10.sup.3. Such an efficiency of removal DF as low as about 10.sup.3 is too low in terms of the prevention of radioactive contamination in the disposal of waste water containing radioactive substances, in particular, and therefore it requires additional introduction of a demineralizer treating condensed water in the posterior stage of a concentrator.
As for the method of concentration using the porous membrane, it has such a problem as stated below owing to the direct contact of waste water with the porous membrane therein. With regard to the waste water which is the object of waste disposal, waste water of high electroconductivity coming out of a power station (mainly waste water called floor drain) contains a variety of metal ions and soap waste, and in a membrane disposal of a contact type, there is a large possibility of a membrane being clogged therewith. Although DF is raised somewhat in the membrane disposal of the contact type, accordingly, it can reasonably be assumed that the reliability of the machinery and the plant dependent on the life of the membrane lowers. Disclosure of Invention
An object of the present invention is to furnish a waste water concentrator and a concentrating method which enable the attainment of high DF and are operable with high reliability for a long time.
A second object of the present invention, in addition to the above object, is to furnish a waste water concentrator and a concentrating method which facilitate the adjustment of a quantity of disposal
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Baba Tsutomu
Chino Koichi
Kikuchi Makoto
Sawa Toshio
Uchida Shunsuke
Bascomb Wilbur
Hitachi , Ltd.
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