JPS60172390A - Manufacture of highly demineralized water - Google Patents

Abstract

PURPOSE:To omit the pretreatment, and to obtain economically the titled highly demineralized water by supplying the steam of original water which is generated by evaporation with heating into a heat demanding stage which is indirectly heated, and precision-filtering the condensate of said steam with a permeable membrane, etc. CONSTITUTION:The original water 1 such as industrial water is supplied into a steam generating stage 13 such as a boiler, and the steam 14 generated in said stage is supplied into an indirect-heating drying stage 15. The heat retained by the steam 14 is utilized for drying a water-contg. material 16, and the condensed water 17 is obtained from the steam 14. The condensed water (hot water) 17 is then treated in an ion-exchange polisher stage 9, and precision-filtered with a membrane filter 18 using a reverse osmosis membrane, an ultrafiltration membrane, etc. to obtain the highly demineralized water 12 which is supplied to necessary places. Either the ion-exchange polisher stage 9 or the membrane filter 18 can be omitted in accordance with the desired water quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing highly purified water, so-called ultrapure water, used in water cleaning processes in the semiconductor manufacturing industry and other various industries.

[Prior art]

As shown in FIG. 1, a typical conventional ultrapure water production system processes raw water 1 through a coagulation and precipitation process 2, followed by a decarboxylation process 3, a filtration process 4, a reverse osmosis membrane process 5, and an ion exchange process 6. , further sequentially perform filtration step 7 to produce primary pure water,
In order to obtain even higher level ultrapure water, the above-described ultrapure water is subjected to an ultraviolet sterilization process 8, an ion exchange bolisha process 9, an ultrafiltration process 1O, and a precision filtration process 11, and then this ultrapure water 12 is required. It is sent to individual locations.

As described above, conventional ultrapure water production systems have a large number of unit operations (mostly separation operations) arranged in series, and therefore have many problems as described below.

■ Maintenance is complicated.

■ Reverse osmosis membrane needs to be cleaned and replaced.

■ Ion exchange resin needs to be regenerated and replenished.

■ The sterilizing effect of ultraviolet sterilization is not sufficient.

■ It is necessary to treat and dispose of sludge generated during pretreatment operations such as coagulation and sedimentation operations.

■ When raw water contains a large amount of silica, extra measures such as lowering the water recovery rate or removing silica through ion exchange treatment in advance should be taken to avoid scaling problems during reverse osmosis membrane operation. I have no choice but to take it.

■ In order to prevent membrane contamination during reverse osmosis membrane operation, complicated pretreatments such as chlorine injection, dechlorination, and coagulation solid-liquid separation are required.

■ Since a large number of unit operations are required, the number of devices, tanks, and piping increases, which increases the overall equipment cost and installation area, and also tends to cause troubles such as after-pollution.

[Purpose of the invention]

An object of the present invention is to provide a method for producing ultrapure water that accurately solves the problems of conventional ultrapure water production systems.

Still another object of the present invention is to achieve energy saving and rationalization of heat utilization processes in factories that use ultrapure water.

[Structure of the invention]

The present invention heats and evaporates raw water, supplies the generated steam to a process that requires heat through indirect heating, utilizes the heat retained in the steam, and then processes the condensed water of the steam through precision filtration using an ion exchange polisher and a permeable membrane. It is characterized by processing using at least one of the following.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings. In FIG. 2, fresh water such as well water, industrial water, tap water, lake water, river water, etc. is used as raw water, and this raw water is used to steam steam from a boiler or the like. The steam 14 generated here is supplied to a drying step 15 by indirect heating, and the heat capacity of the steam 14 is used to dry the water-containing material 16, and then condensed water 17 from the steam 14 is obtained.

Next, this condensed water 17 (warm water) is treated in an ion exchange polisher step 9, and subjected to precision filtration through a membrane filter 18 using a reverse osmosis membrane, an ultrafiltration membrane, etc. to obtain ultrapure water 12, which is then delivered to the required location. supply

Note that either the ion exchange polisher step 9 or the membrane filter 18 can be omitted depending on the required water quality.

Yes, there is a crack 9 from the piping in the condensed water 17.
Because small amounts of fat and oil may be included from the outside,
Ion exchange, Trijiani level 9 and membrane filter 18
In some cases, the microfiltration membrane is subjected to pretreatment such as filtration or activated carbon treatment.

Furthermore, the condensed water 17 has a temperature of around 90°C,
A higher water temperature is extremely convenient for membrane treatment where the permeability improves, but when treating the condensed water 17 in the ion exchange polisher step 9, it is necessary to cool it to below 60°C to prevent deterioration of the ion exchange resin. preferable.

In the above embodiment, the heat retained by the steam 14 is used in the drying process 15 by indirect heating for drying the water-containing material 16, but it can also be used for heating, hot water production, and any other process requiring heat by indirect heating. Needless to say, in some cases, the generated steam 1 from the steam generation step 13
It is also advantageous to further increase the temperature of 4 by means such as adiabatic compression.

Further, when a water heating evaporation device and a process using the obtained steam have already been installed, the present invention can be implemented using them.

[Effects of the Invention] As described above, the present invention generates steam from raw water by heating and evaporating it, uses the heat retained in this steam for heat-requiring processes, and then condenses itself to generate high-grade steam. We have adopted a completely unprecedented configuration in which a specific type of water, condensed water with high quality and high temperature, is processed through microfiltration using an ion exchange polisher and a permeable membrane (hereinafter referred to as the "polishing process"). It is possible to obtain extremely important effects, eliminate the drawbacks of conventional ultrapure water production systems, and make a significant contribution to the development of various industries that utilize ultrapure water.

■ Since condensed water from the indirect steam heating process such as drying is supplied to the borishing process, it is possible to omit the reverse osmosis membrane process, ion exchange process, and other various pretreatment processes that are required before the conventional polishing process, making it more rational. Moreover, a simple ultrapure water production system can be realized.

■ Since the conventional pre-treatment process can be omitted, it is extremely easy to manage the cone retention.

■ Since condensed water from steam is supplied to the polishing process, heat sterilization is far more complete than conventional sterilization by ultraviolet irradiation, and there are almost no problems with contamination caused by microorganisms.

■ The water supplied to the polisher is steam condensed water and has a quality close to that of distilled water, so it does not cause scale formation or membrane contamination during the polishing process.

■ In water cleaning processes such as those in the semiconductor manufacturing industry, the higher the temperature of the cleaning water, the higher the cleaning effect.
Since condensed water of about 0 to 100° C. is used, high-temperature ultrapure water can be obtained, and the cleaning effect is significantly improved.

■ Energy saving and rationalization of heat utilization processes in factories that use ultrapure water can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a system explanatory diagram showing a conventional example, and FIG. 2 is a system explanatory diagram showing an embodiment of the present invention. 1...Raw water, 2...Coagulation sedimentation step, 3
...Decarboxylation step, 4,7...Filtration step, 5...Reverse osmosis membrane step, 6...Ion exchange step, 8... ...Ultraviolet sterilization process, 9...
...Ion exchange borisha process, lO...ultrafiltration process, 11...microfiltration process, 12...ultra pure water, 13...steam generation process, 14 ...
...Steam, 15...Drying process, 16...
... Hydrate, 17 ... Condensed water, 18 ...
...Membrane filter. Patent applicant: Ebara Infilco Co., Ltd. Representative Patent attorney: Masayuki Takagi

Claims (1)

[Claims] 1. Raw water is heated to evaporate, the generated steam is supplied to a process that requires heat by indirect heating, and the retained heat of the steam is utilized, and then the condensed water of the steam is passed through an ion exchange polisher or a permeable membrane. 1. A method for producing ultrapure water, the method comprising treating it with at least one of microfiltration treatments. 2. The method for producing ultrapure water according to claim 1, wherein the temperature of the condensed water is cooled to 60° C. or lower during treatment with the ion exchange polisher.