JP2005329311A - Method for sterilizing demineralizer and demineralizer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for sterilizing a demineralizer capable of preventing deposition of a scale on the surface of a reverse osmosis membrane even if sterilization using hot water is repeated and simply sterilizing the demineralizer, and to provide the demineralizer. <P>SOLUTION: Raw water in a raw water tank 2 storing water to be treated used in the demineralizer 1 is heated by a first heat exchanger 3 as hot water supply means. Hydrochloric acid is loaded into the heated hot water from a hydrochloric acid supply device 9 as acid loading means and acid hot water the pH of which is adjusted at not more than the saturated solubility of calcium carbonate is supplied to the reverse osmosis membrane 5. Sterilization by the acid hot water continues for 10 to 60 minutes, the temperature of the reverse osmosis membrane 5 is gradually increased and the sterilization is completed. After the sterilization is completed, the demineralizer 1 is wholly rinsed by pure water or the like when required, thereafter the raw water is removed from the raw water tank 2, the raw water is treated by the reverse osmosis membrane 5, and then the pure water is produced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sterilization method for a pure water production apparatus and a pure water production apparatus, and more particularly to a sterilization method and a pure water production apparatus for sterilizing a pure water production apparatus having a reverse osmosis membrane apparatus with hot water.

  2. Description of the Related Art Conventionally, a pure water production apparatus including a deionization apparatus, a reverse osmosis membrane apparatus, and the like is known as an apparatus for producing pure water used for manufacturing foods, pharmaceuticals, semiconductor products, and other applications. In such a pure water production apparatus, city water or industrial water (hereinafter referred to as “raw water”) containing impurities such as organic matter and ions is treated water, and pure water is produced by removing impurities in the raw water.

  Such a pure water production apparatus is sterilized as necessary in order to prevent bacteria from growing inside the apparatus. As a sterilization method inside the pure water production apparatus, a method in which a sterilizing agent such as hydrogen peroxide is passed through the apparatus or a method in which hot water of 60 ° C. or higher is passed through the apparatus is known.

  As a method of sterilizing by passing hot water through the inside of the pure water production apparatus, there is a method of heating the treated water supplied to the pure water production apparatus and passing it through the pure water production apparatus (for example, Patent Document 1). The pure water production apparatus described in Patent Document 1 includes a raw water tank storing treated water of the pure water production apparatus, and water treatment equipment such as a reverse osmosis membrane apparatus and an electric regeneration type deionization apparatus. A heat exchanger is provided between the water treatment device and the raw water tank. And when sterilizing this pure water manufacturing apparatus, the raw | natural water taken out from the raw | natural water tank is heated with a heat exchanger, and is supplied to water treatment apparatuses, such as a reverse osmosis membrane apparatus.

  According to the above method for sterilizing a pure water production apparatus using hot water, the pure water production apparatus can be sterilized by heat sterilizing bacteria inside the apparatus by a simple operation of heating the raw water supplied from the raw water tank. Can do.

However, in the above method, when the sterilization treatment with hot water is repeated, the precipitated substance containing calcium or the like (hereinafter referred to as “scale”) adheres to the inside of the device, and the treatment due to the deterioration of the quality of the produced pure water or the blockage of the device It became clear that it caused problems such as a decrease in efficiency. In particular, when sterilization is performed by heating raw water containing calcium ions and the like, it has been clarified that calcium carbonate is easily concentrated on the surface of the reverse osmosis membrane, and scale is likely to adhere to the surface of the reverse osmosis membrane.
JP 2001-47054 A

  The present invention has been made in view of the above problems, and an object thereof is to provide a sterilization method and a pure water production method for a pure water production apparatus capable of performing hot water sterilization that is simple and prevents the generation of scale. To do.

  The pure water production apparatus sterilization method of the present invention is characterized by passing acidic hot water through a reverse osmosis membrane apparatus.

  Specifically, acidic hot water is adjusted to have a pH of 3 to 6.5, particularly about 3 to 6, and heated to a temperature of 60 ° C or higher, particularly 80 ° C or higher. It is preferable that

  As a method for obtaining acidic hot water by adjusting the pH of neutral water, there is a method of adding an acid such as hydrochloric acid, sulfuric acid, citric acid, and nitric acid to raw water used as water to be treated in a pure water production apparatus. Can be mentioned. The acid may be added to the front stage of the reverse osmosis membrane device, and when the permeated water from the reverse osmosis membrane device is circulated to the front stage of the reverse osmosis membrane device, an acid may be added to the permeated water. Moreover, when circulating the concentrated water from a reverse osmosis membrane apparatus to this reverse osmosis membrane apparatus, you may add an acid to this concentrated water.

  The pH of the acidic hot water is preferably in the range described above, but may be lower than the pH of the raw water supplied to the reverse osmosis membrane device during the production of pure water. Even when the concentration of calcium ions and carbonate ions in the raw water is such that calcium carbonate scales are not generated, calcium ions and carbonate ions are concentrated in the reverse osmosis membrane in the process of hydrothermal sterilization of the reverse osmosis membrane device. And since it is a warming state, there exists a possibility that a scale may be produced | generated on the concentration surface of a reverse osmosis membrane. In order to prevent the formation of such scale, in the present invention, the pH of the hot water is such that the ionic product of calcium ions and carbonate ions (including bicarbonate ions) of the concentrated water of the reverse osmosis membrane device is the temperature of the acidic hot water. It is preferable to adjust to a value that is equal to or lower than the saturation solubility of calcium carbonate.

  The acidic hot water supplied to the reverse osmosis membrane treatment apparatus may be heated either before or after pH adjustment. In particular, a pure water production apparatus such as a reverse osmosis membrane apparatus is prepared by heating the raw water taken out from the raw water tank and adding acid immediately before supplying the heated raw water to the reverse osmosis membrane apparatus to adjust acidic hot water. It is preferable to sterilize.

  The raw water contains impurities such as calcium ions and carbonate ions having a calcium carbonate concentration of about 10 to 150 mg / L. However, according to the present invention, the hot water supplied to the reverse osmosis membrane device is made acidic so that the calcium carbonate It is possible to increase the saturation solubility of and prevent the scale from adhering to the reverse osmosis membrane surface. For this reason, according to this invention, generation | occurrence | production of a scale can be prevented even when the raw | natural water stored by the raw | natural water tank is utilized for hot water sterilization.

  According to the present invention, by using the raw water stored in the raw water tank, it is possible to easily sterilize the pure water production apparatus, and it is possible to prevent a scale that is particularly easily generated when raw water is used. In addition, instead of using raw water, it is conceivable to sterilize with hot water using pure water that does not contain impurities such as calcium ions. In hot water sterilization using pure water, the water in the raw water tank is replaced with pure water. Need to do. In the present invention, hot water sterilization can be performed using the raw water in the raw water tank, so that the time and water required to replace the water in the raw water tank can be saved.

  Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of a pure water production apparatus 1 according to an embodiment of the present invention.

  The pure water production apparatus 1 includes an activated carbon tower 4, a reverse osmosis membrane device 5, a membrane deaeration device 6, an electric regeneration deionization device 8 as water treatment devices, and water to be treated to be supplied to these water treatment devices. A raw water tank 2 for storage is provided. The pure water production apparatus 1 further includes a first heat exchanger 3 as a hot water supply means, a second heat exchanger 7, and a hydrochloric acid supply apparatus 9 as an acid addition means. Raw water tank 2, first heat exchanger 3, activated carbon tower 4, reverse osmosis membrane device 5, membrane deaeration device 6, second heat exchanger 7, and deionization device 8 are arranged in series in this order. It is connected.

  This pure water production apparatus 1 produces pure water (referred to as “primary pure water”) having a specific resistance of about 15 MΩ · cm by removing impurities from raw water. The pure water production apparatus according to the present invention includes at least a reverse osmosis membrane apparatus and produces pure water from water to be treated containing impurities such as city water. The water exemplified in the pure water production apparatus 1 In addition to the processing equipment, a subsystem (or a secondary pure water system) may be included. The subsystem includes, for example, an ultraviolet oxidation device, a deionization device, and an ultrafiltration membrane device, and removes impurities contained in the primary pure water to produce ultrapure water.

  Hereinafter, the pure water manufacturing method by said pure water manufacturing apparatus 1 is demonstrated. Raw water such as city water is supplied to the raw water tank 2 as treated water of the pure water production apparatus 1 through the pipe 21 and stored in the raw water tank 2. The raw water stored in the raw water tank 2 is sent out from the raw water tank 2 by liquid feeding means (not shown) such as a pump, and is adjusted to a temperature suitable for processing (for example, 20 to 25 ° C.) by the first heat exchanger 3. It is adjusted, processed by the activated carbon tower 4, the reverse osmosis membrane device 5, the membrane deaeration device 6, and the deionization device 8, and is taken out from the pipe 28 as pure water from which impurities are removed.

  The pure water taken out from the pipe 28 is used as it is or after further processing by the subsystem, and then used for the production of foods, pharmaceuticals (including purified water and water for injection) or semiconductor products, and steam generation.

  The pure water production apparatus 1 is appropriately sterilized with hot water in order to sterilize the inside of the apparatus. Hereinafter, the sterilization method of the pure water production apparatus 1 according to the present invention will be described.

  When sterilizing the pure water production apparatus 1, first, raw water stored in the raw water tank 2 is supplied to the first heat exchanger 3 through the pipe 22. The raw water is heated by the first heat exchanger 3, passes through the activated carbon tower 4, is adjusted in pH by hydrochloric acid supplied from the hydrochloric acid addition device 9, and is supplied to the reverse osmosis membrane device 5.

  The permeated water of the reverse osmosis membrane device 5 is sent from the pipe 25 to the membrane deaerator 6 and returned to the raw water tank 2 through the circulation pipe 41 and the pipe 21 connected to the pipe 27. On the other hand, the concentrated water of the reverse osmosis membrane device 5 is returned from the circulation pipe 42 to the raw water tank 2. According to such circulation, since the liquid supplied to the reverse osmosis membrane device 5 can be gradually heated, the amount of energy required for heating the raw water can be reduced, and the reverse osmosis membrane device 5 and the like can undergo a rapid temperature change. It can be prevented from being exposed to damage.

  When the temperature of the liquid supplied to the reverse osmosis membrane device 5 reaches a predetermined temperature by the circulation, the output of the first heat exchanger 3 is adjusted, and the acidic hot water at the predetermined temperature is reversed for 10 to 60 minutes. The pure water production apparatus 1 including the reverse osmosis membrane apparatus 5 is sterilized by passing through the osmosis membrane apparatus 5. The temperature of the acidic hot water in this sterilization process is preferably 60 ° C. or higher, particularly preferably 80 ° C. or higher. The pure water production device 1 sterilizes with acidic hot water for a predetermined time, and then receives the raw water from the pipe 21 into the raw water tank 2 and discharges the concentrated liquid from the discharge pipe 43 connected to the circulation pipe 42 and the like. The water production apparatus 1 is gradually cooled to finish sterilization.

Next, an acidic hot water adjustment method by adding hydrochloric acid will be described in detail. In the present embodiment, the hydrochloric acid supply device 9 includes a hydrochloric acid tank that stores hydrochloric acid and an acid supply pipe that is connected to the hydrochloric acid tank and the pipe 24. The hydrochloric acid supply device 9 adds hydrochloric acid to the raw water so that the hot water supplied to the reverse osmosis membrane device 5 has a predetermined pH value that is equal to or lower than the saturated solubility of calcium carbonate even if the hot water is concentrated in the reverse osmosis membrane device 5. Added. The pH of the acidic hot water is determined from the calcium ion concentration and carbonate ion concentration (including bicarbonate ions) of the raw water, the degree of concentration by the reverse osmosis membrane device 5, and the hot water temperature (for example, 80 ° C.). The solubility is obtained, and the calcium carbonate solubility is set to a value that is not more than the saturation solubility.

  The amount of hydrochloric acid added is preferably adjusted so that the acidic hot water passing through the reverse osmosis membrane device 5 has a predetermined pH. For example, the inlet of the reverse osmosis membrane device 5, the outlet of concentrated water, or the inlet It may be adjusted while monitoring the pH of the liquid to be passed at both outlets of the concentrated water. In the present embodiment, the inlet pH meter 11 and the pipe 24 connected to the inlet side of the reverse osmosis membrane device 5 and the pipe 42 or 43 connected to the outlet of the concentrated water of the reverse osmosis membrane device 5, respectively, A pH meter 12 for the outlet of concentrated water is provided to adjust the amount of hydrochloric acid added.

  The hydrochloric acid may be added to the upstream side of the reverse osmosis membrane device 5, and the acid supply pipe of the hydrochloric acid supply device 9 is connected to the pipe 24 connected to the inlet side of the reverse osmosis membrane device 5 as in this embodiment. Instead of connecting, an acid supply pipe may be connected to the pipe 23 or the circulation pipe 41 or 42. Further, the temperature may be gradually raised without adding hydrochloric acid to the raw water, and hydrochloric acid may be added after reaching a predetermined temperature.

  In this way, by passing the acidic hot water through the reverse osmosis membrane device 5, the raw water in the raw water tank 2 can be used, and further, the scale can be sterilized by preventing the scale from adhering to the surface of the reverse osmosis membrane.

[Example]
The pure water production apparatus 1 shown in FIG. 1 was sterilized under the conditions described below. In the raw water tank 2, water having a carbonate ion concentration (including bicarbonate ions) of 100 mg / L, a calcium ion concentration of 120 mg / L, and a total solid content concentration of 210 mg / L is stored as raw water, and this is stored in the first heat exchanger 3. Then, the mixture was gradually heated, and hydrochloric acid was supplied from the hydrochloric acid supply device 9 to adjust the pH and supplied to the reverse osmosis membrane device 5. The reverse osmosis membrane device 5 includes a heat resistant reverse osmosis membrane (DOW HS-RO, manufactured by The Dow Chemical Company) having a membrane area of 7.9 m ² and 4 inches. The acidic hot water supplied to the reverse osmosis membrane device 5 was subjected to circulation treatment at a pH of 6.0 and a temperature of 80 ° C. for 1 hour. The water permeability in the reverse osmosis membrane device 5 was 30%, the calcium ion concentration of the reverse osmosis membrane concentrated water was 171 mg / L, and the carbonate ion (including bicarbonate ion) concentration was 143 mg / L.

  Sterilization under the above conditions was carried out 100 times at a frequency of 5 times / day, but no increase in the differential pressure of the reverse osmosis membrane device 5 occurred in the operation during the production of pure water after the sterilization. Further, the reverse osmosis membrane device 5 which had been sterilized 100 times was washed with hydrochloric acid (pH 2) using a 50 L washing tank, and the calcium concentration of the washing solution was measured, and it was 30 mg / L.

[Comparative example]
As a comparative example, the pure water production apparatus 1 was sterilized under the same conditions as in Example except that hydrochloric acid was not added to the raw water and hot water having a pH of 7.5 heated to 80 ° C. was used. In the operation at the time of pure water production after the sterilization was finished, the differential pressure gradually increased as the number of sterilizations increased. When the number of sterilizations reached 100, the reverse osmosis membrane device 5 was washed with hydrochloric acid, and the calcium concentration of the washing solution was measured and found to be 30 g / L.

  As shown in the Examples and Comparative Examples, in the present invention, acid hot water is passed through the reverse osmosis membrane device 5 to sterilize the pure water production device 1 so that the scale adheres to the surface of the reverse osmosis membrane and the pure water. The performance deterioration of the manufacturing apparatus 1 can be prevented, and the quality of the pure water produced can be prevented from deteriorating.

  INDUSTRIAL APPLICABILITY The present invention can be used for an ultrapure water manufacturing apparatus used for manufacturing semiconductor products such as LSIs and wafers, pharmaceutical manufacturing, and the like.

It is a schematic diagram of the pure water manufacturing apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pure water manufacturing apparatus 2 Raw water tank 3 1st heat exchanger (hot water supply means)
5 Reverse osmosis membrane device 9 Hydrochloric acid supply device (acid addition means)

Claims (4)

A method for sterilizing a pure water production apparatus comprising a reverse osmosis membrane device,
A method for sterilizing a pure water producing apparatus, wherein acidic hot water is passed through the reverse osmosis membrane apparatus.   The method for sterilizing a pure water production apparatus according to claim 1, wherein the acidic hot water is obtained by adding an acid to hot water.   The method for sterilizing a pure water producing apparatus according to claim 1 or 2, wherein the acidic hot water has a pH of 6.5 or less and a temperature of 60 ° C or more. A pure water production apparatus comprising a reverse osmosis membrane device and hot water supply means for supplying hot water to the reverse osmosis membrane device,
An apparatus for producing pure water, further comprising acid addition means for adding an acid to the hot water.

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