JPH03293087A - Production of ultra-pure water - Google Patents

Abstract

PURPOSE:To prevent the increase of pressure drop in a membrane separator fitted with a built-in permeable membrane by treating primary pure water by successive passing through a UV irradiation device, a polisher device, a cartridge type micro-filter and the membrane separator fitted with a built-in permeable membrane. CONSTITUTION:When primary pure water 1 obtd. from an apparatus for producing primary pure water is further treated to obtain ultra-pure water, the primary pure water 1 is treated by successive passing through a UV irradiation device 3, a polisher device 4 packed with ion exchange resin, a cartridge type micro- filter 5 and membrane separator 6 fitted with a build-in permeable membrane. The UV irradiation device 3 and the polisher device 4 may be reversed. In order to maintain high quality of water at a use point 7, water passed through the separator 6 is circulated through a circulating line 8.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for producing ultrapure water used for semiconductor manufacturing, pharmaceutical manufacturing, etc. The present invention relates to a method of further processing pure water to obtain ultrapure water.

<Prior art> Water used in semiconductor manufacturing and pharmaceutical manufacturing contains electrolytes,
There is a need for highly purified ultra-pure water, so-called ultra-pure water, which contains extremely few particles, viable bacteria, and the like.

In recent years, as these industrial technologies have become more sophisticated, the required water quality has also become higher, and it has become necessary to produce even more highly purified ultrapure water.

Ultrapure water has conventionally been generally produced using a combination of the following systems. First, colloidal substances in the raw water are removed using a flocculation device, filtration device, etc., then a water purification device,
Most electrolytes, particulates, viable bacteria, etc. are removed using reverse osmosis equipment, deaerators, mixed bed polishers, etc., and the primary pure water obtained from such primary water purification equipment is further sterilized and/or organic matter decomposed. UV irradiation equipment for
A secondary pure water production device consisting of a polisher device, a membrane separation device, etc. is used to finally remove extremely small amounts of impurities remaining in the primary pure water to produce ultrapure water.

The ultrapure water produced by the above series of equipment is supplied to each use point, but the secondary pure water production equipment is separated from the primary water production equipment to prevent contamination within the supply piping. They are often installed near points of use.

Membrane separation equipment used in secondary pure water production equipment has a built-in permeation membrane selected from ultrafiltration membranes and reverse osmosis membranes, and is particularly effective against the contamination of fine nonionic substances into ultrapure water. In order to prevent this, it is essential to install the membrane separation device in the secondary pure water production equipment, and it is installed at the end of the secondary pure water production equipment.

However, the membrane separator used in this secondary water purification system traps fine particles that could not be removed by the primary system on the surface of the permeable membrane, or fine nonionic substances such as organic matter eluted from piping materials, etc. This adheres to the membrane surface, increasing pressure loss and reducing the amount of ultrapure water produced.

For this reason, conventionally, permeable membranes whose pressure loss has increased and the production amount of ultrapure water has decreased have been cleaned to recover the pressure loss. The permeable membrane is cleaned when the pressure drop reaches a predetermined value, but chemicals are often used in this cleaning process, and because the chemicals contaminate the system, it is usually not cleaned within the series. Therefore, permeable membranes with increased pressure loss are cleaned using appropriate chemicals in a separate dedicated cleaning facility, but the chemicals used for cleaning must be further cleaned before being reinstalled in the system. Yes, a large amount of ultrapure water is consumed. Furthermore, cleaning the permeable membrane requires extremely advanced technology and a large amount of cost, as it is necessary to clean up the entire secondary pure water production equipment after reinstallation.

Furthermore, repeated cleaning may cause deterioration of the permeable membrane.

<Problems to be Solved by the Invention> The present invention provides a method for producing ultrapure water that can prevent an increase in pressure loss in the membrane separation device used in the conventional secondary pure water production device described above. The purpose is to

Furthermore, by preventing an increase in the pressure loss of the membrane separator, it is an object of the present invention to reduce the number of times the chemical cleaning is performed, and to significantly reduce the consumption of ultrapure water required for cleaning.

Means for Solving the Problems〉 The method for producing ultrapure water according to the present invention, which has been made to achieve the above objects, further processes primary pure water obtained from a primary pure water production apparatus to obtain ultrapure water. To obtain water, the primary pure water is processed in the order of an ultraviolet irradiation device and a polisher device filled with ion exchange resin, or a polisher device filled with ion exchange resin and an ultraviolet irradiation device, and then cartridge-type precision filtration. It is characterized by processing in the following order: first, a membrane separation device containing a permeable membrane.

The present invention will be explained in detail below.

In the ultrapure water production process, as described above, primary pure water is produced using a primary pure water production apparatus using tap water, well water, river water, etc. as raw water, but first, pretreatment is performed depending on the quality of the raw water. As a pretreatment device, a combination of collection treatment, filtration treatment, activated carbon treatment, etc. is used.

The raw water that has passed through the pretreatment is then treated with, for example, a two-bed, three-column type water purification device and/or hot bed type water purification device, which is applied to normal pure water production, and further with a reverse osmosis membrane device. Alternatively, the reverse osmosis membrane device may be placed first, followed by a two-bed, three-column type water purification device and/or a hot bed type water purification device.

Most of the electrolytes, particulates, living bacteria, etc. in the raw water are removed in this type of primary water purification equipment, and the specific resistance is usually 10~10.
15 MΩ・1, the number of fine particles is 100 to 500/ml, and the number of viable bacteria is about 10/m1 or less. Primary pure water can be obtained.

The primary pure water obtained in the primary pure water production device is then further processed in the secondary pure water production device of the present invention to remove electrolytes, particulates, living bacteria, etc. that could not be removed by the primary pure water production device. It is further removed and supplied to the point of use of ultrapure water.

FIG. 1 is an explanatory diagram showing the flow of a secondary pure water production apparatus as an example of an embodiment of the present invention.

In order to maintain the water quality at the use point 7, a system is used in which permeated water from the membrane separation device 6 installed at the end of the secondary pure water production device is constantly circulated using a circulation line 8.

Although not shown in the figure, non-permeated water from the membrane separation device 6 is returned to the primary pure water production device and recovered.

1 in the figure is the primary pure water tank and the primary pure water production equipment (not shown)
The primary pure water produced in the above is temporarily stored, and the primary pure water is first introduced into the ultraviolet irradiation device 3 by the water pump 2.

The ultraviolet irradiation device uses ultraviolet rays to sterilize living bacteria such as bacteria in primary pure water by utilizing the sterilizing effect of ultraviolet rays. The wavelength used is around 254 nm, and the irradiation amount is about 50,000 μW/sec/d. Note 2
Wavelengths around 54 nm are generally referred to as germicidal radiation.
Although it is mainly used for the purpose of sterilization, it also includes a wavelength around 185 nm, which is particularly effective in decomposing organic matter in water, so that it decomposes organic matter in water as well as sterilization. Further, the ultraviolet irradiation device can mainly irradiate ultraviolet rays around 185 nm to decompose organic matter in water, and simultaneously sterilize with the wavelength around 25 dnm contained therein.

The ultraviolet irradiated pure water is subsequently introduced into the polisher device 4.

The polisher device 4 consists of a mixed layer of a strongly basic anion exchange resin and a strongly acidic cation exchange resin that have been almost completely regenerated. The resin is regenerated outside the system, mixed, and filled into a cartridge-type ion exchange tower for use.

The pure water flowing out from the above-mentioned polisher device 4 has a pleat shape, a flat plate shape, etc. of 0.1. It is supplied to a cartridge-type precision filter 5 which has a built-in cartridge filter with a pore size of ~1 μm, and the entire amount is filtered by a so-called cross-flow type, and the filtered water is then filtered using mainly polyacrylonitrile, polyamide, polysulfone, etc. The water is supplied to a membrane separation device 6 which has a built-in permeation membrane such as an ultrafiltration membrane or a reverse osmosis membrane. The membrane separator 6 removes particularly fine nonionic substances that could not be removed by the various processes upstream, and the resulting permeated water, highly purified ultra-high purity water, is used as ultra-pure water. fed to point 7.

The quality of this ultrapure water is a specific resistance of 16 to 18 MΩ, a number of fine particles of 20 to 50 particles/ml or less, and a number of viable bacteria of 1 particle/ml or less.

Conventional secondary pure water production equipment does not treat the inflow water of the membrane separator 6 with a cartridge-type precision filter, and therefore, as mentioned above, pressure loss increases in a relatively short period of time. If the inflow water is treated with the cartridge-type precision filter 4 upstream of the membrane separator f6 as in the present invention, the tendency of the pressure loss in the membrane separator 5 to increase is significantly reduced. Moreover, the pressure loss of the cartridge-type precision filter itself hardly increases even if it is used for a relatively long period of time.

<Function> As described above, in a secondary pure water production apparatus, when high-purity pure water that has passed through a cartridge-type precision filter is supplied to a membrane separation apparatus as in the present invention, the pressure loss of the membrane separation apparatus may be reduced for any reason. It is not clear whether the upward trend can be significantly reduced, but fine nonionic substances are electrically adsorbed and removed by the built-in cartridge filter when they pass through the cartridge type filter. it is conceivable that. This phenomenon in which the tendency for pressure loss to rise in a membrane separator is significantly reduced occurs with any membrane, regardless of the type of membrane, and does not appear with respect to a specific membrane. The cartridge filter used in the cartridge type filter used in the present invention may be in any form such as pleated or flat plate, and its material may be polysulfone, polysulfone, etc.
Any of 6-row nylon, polypropylene, polyester, etc. may be used, but the use of a cartridge filter having a positive charge can effectively suppress the tendency for the pressure loss of the downstream membrane separation device to increase.

The water flow rate is 0.7 to 2.9n? /rrLhr vicinity is adopted.

Furthermore, embodiment a shown in Fig. 1 shows an example in which the ultraviolet irradiation device is installed before the polisher device, but the polisher device, the ultraviolet irradiation device, the cartridge type precision filter, and the membrane separation device are processed in this order. The effect of the present invention is also the same.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited to the following Examples.

Example 1 A coagulant was added to industrial water (technical water), and the water was passed through a coagulation filter filled with two layers of anthracite and sand as filter media, and then a strongly acidic cation exchange resin, Amberlite (registered trademark) , the same applies hereafter) After passing through a cation exchange tower filled with IR-124 and a decarboxylation tower for removing free carbonic acid, the weakly basic anion exchange resin Amberlite IRA-94 and the strongly basic anion exchange resin Amberlite ERA are added. Water was sequentially passed through an anion exchange tower filled with 5C-400, and then treated with a reverse osmosis device equipped with a reverse osmosis membrane 5C-1200 (manufactured by Toshi Co., Ltd.) at an operating pressure of 20 kg/aj and a recovery rate of 85%. ,
Furthermore, Amberlight 200C and Amberlight IRA
Water was passed through a mixed bed solution consisting of a mixed resin layer with a ratio of -900 to 1=1 for treatment, and the effluent water was used as primary pure water.

The average quality of the primary pure water was as shown in Table 1.

The above-mentioned primary pure water was used to produce ultrapure water using a secondary pure water production apparatus having the flow according to the present invention shown in FIG.

After storing the primary pure water in a primary pure water storage tank made of -HFRP,
It was supplied by a water pump.

The distance between the primary pure water production equipment and the secondary pure water production equipment is approximately 2
It was 00m.

The secondary pure water production equipment was first equipped with an ultraviolet irradiation device to prevent viable bacteria, and by utilizing UV light of 253.7 layers, the number of sexual bacteria in the system was reduced as much as possible.

After the ultraviolet irradiation device, a cartridge-type column was filled with a 1:1 mixture of a strong acidic cation exchange resin and a strong basic anion exchange resin that had been specially condensed and regenerated externally. Install the polisher device,
The treated water from the ultraviolet irradiation device was passed through. Note that the water flow rate was SV30 hr-1.

Following the polisher device, a cartridge-type precision filter having a mesh opening of 0.2 μm and containing a pleated cartridge filter body having a positive charge was installed, and the entire amount of the water treated by the polisher device was passed through in a perpendicular flow. Also, the filtration flow rate is approximately 0
．． It was set to 6nf/ffr-hr.

As a membrane separation device, a device equipped with an ultrafiltration membrane FCV-3010 (manufactured by Asahi Kasei Industries, Ltd.) was used, and the filtered water of the cartridge-type precision filter was passed through it. The inlet pressure was 3.0 kg/cd and the permeate recovery rate was 90%.

Figure 2A shows the rise in differential pressure in the membrane separation device when ultrapure water is produced in the secondary pure water production device of the present invention as described above.
(solid line).

As shown in Figure 2A (in Example 1, the number of days of water flow was 1)
Even after 00 days, the differential pressure in the membrane separation device remained at the initial differential pressure, and there was no need to clean the permeable membrane with chemicals. Naori-
The differential pressure of the trige type microfilter also hardly increased even after 100 days of water flow.

Comparative Example In the flow of Example 1, the increase in the differential pressure of the membrane separation device when the cartridge-type microfilter is not installed and the conventional treatment method is used, that is, the ultraviolet irradiation device, the polisher device, and the membrane separation device are processed in this order, is as follows. It is shown in Figure 2C (dotted line). In FIG. 2, the portion of graph C with an arrow indicates the chemical cleaning operation.

In the comparative example, after approximately 27 days of water flow, the differential pressure rose to 2.2 kg/-, necessitating chemical cleaning.

When chemical cleaning was performed, the differential pressure recovered, but the differential pressure rose at a similar pace, making chemical cleaning necessary at intervals of approximately 27 days.

Example 2 The conditions were the same as in Example 1, except that a pleated cartridge filter with an opening of 0.2 μm and no charge was used as the cartridge filter used in a cartridge type precision filter, and the increase in the differential pressure of the membrane separation device was It was measured. The results are shown in FIG. 2B (-dotted chain line).

In Example 2, the differential pressure of the membrane separation device tends to increase slightly after the number of days of water flow exceeds 80 days, but even if the number of days of water flow exceeds 100 days, the membrane separation device is not cleaned with chemicals. Similarly to Example 1, the differential pressure of the Naori-Tridge type microfilter did not increase even after 100 days of water flow.

<Effects of the Invention> As is clear from the above examples, the method of the present invention can dramatically reduce the tendency for the pressure loss to increase in the membrane separation device used in the secondary pure water production device, and improve membrane separation. Since the number of cleaning steps for the device can be extremely reduced, the consumption of ultrapure water required for the cleaning step can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a flow of an example of an embodiment of the present invention. Fig. 2 is a graph showing the increase in the differential pressure of the membrane separation device in Example 1, Comparative Example, and Example 2, where the vertical axis is the differential pressure (kg/ci) of the membrane to be passed, and the horizontal axis is the number of days of water flow. (day). 1...Primary pure water storage tank 2...Water pump 3...
・Ultraviolet sterilizer 4...Polisher device 5...
Cartridge type precision filter 6...Membrane separation device 7...Use point 8
...Circulation line procedure amendment form

Claims (1)

[Claims] 1. In order to obtain ultrapure water by further processing the primary pure water obtained from the primary pure water production device, the primary pure water is treated with an ultraviolet irradiation device and a polisher filled with ion exchange resin. or a polisher filled with ion exchange resin, an ultraviolet irradiation device, and then a cartridge-type precision filter and a membrane separation device with a built-in permeable membrane. Production method. 2. The method for producing ultrapure water according to claim 1, which uses a cartridge type precision filter using a cartridge filter body having a positive charge.