JP2004181369A - Ultrapure water making apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrapure water making apparatus constituted so as to eliminate the mixing with even a very small amount of hydrogen peroxide at a use point. <P>SOLUTION: The ultrapure water making apparatus, which has a pretreatment system, a primary pure water system, a secondary pure water system and a recovery system, has a hydrogen peroxide monitor arranged at an arbitrary place between the primary pure water system and the recovery system to detect hydrogen peroxide up to 10 ppb in ultrapure water and the branch pipe equipped with a changeover valve provided on the downstream side of the hydrogen peroxide monitor. When hydrogen peroxide with a predetermined concentration is detected by the hydrogen peroxide monitor, ultrapure water containing hydrogen peroxide is discharged so as not to go to the use point. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrapure water production apparatus.
[0002]
[Prior art]
Ultrapure water used in semiconductor manufacturing processes, etc. is generally purified by a pretreatment system and a primary pure water system, and once stored in an ultrapure water tank, the ultrapure water stored in the ultrapure water tank is secondary pure water. It is supplied to the use point through the water system and used.
[0003]
The pretreatment system is composed of coagulation sedimentation method, sand filtration method, activated carbon adsorption method, pH adjustment, etc. The primary pure water system is filtration separation treatment device, adsorption treatment device, reverse osmosis membrane (RO) device, UV oxidation device The secondary pure water system is composed of an ultraviolet oxidation device, an ion exchange treatment device, an ultrafiltration device, and the like.
If a large amount of chemicals such as hydrogen peroxide is not mixed in the ultrapure water used at the use point, it is recovered for use as raw water for the production of ultrapure water again. The recovered water is returned to the pretreatment system or the primary pure water system after chemicals are removed or decomposed in the recovery line.
An activated carbon treatment apparatus for decomposing hydrogen peroxide and the like mixed as a chemical is also inserted in the recovery line.
[0004]
Recently, it has been found that functional water in which active gases such as hydrogen, oxygen, and ozone are dissolved is effective for cleaning silicon wafers, and it is now possible to install a functional water production device in a secondary pure water system. However, there is a problem that the concentration control is very difficult.
[0005]
As a result of researches on this problem, the present inventor has not been able to completely decompose hydrogen peroxide with the activated carbon inserted in the conventional recovery line, and hydrogen peroxide remains in the ppb order in the recovered water. However, this trace amount of remaining hydrogen peroxide reaches the terminal ultrapure water device without being decomposed in the primary pure water system and the secondary pure water system, and the concentration of functional water using ultrapure water is changed. I found out.
[0006]
In other words, ultrapure water that was 0 ppm by the conventional detection method using hydrogen peroxide test paper or the hydrogen peroxide monitor using permanganic acid method or iodine electrode method is hydrogen peroxide using iodine electrode titration method. When measured with a monitor, hydrogen peroxide was detected in the range of 5 to 30 ppb, and this trace amount of remaining hydrogen peroxide varied the concentration of functional water.
[0007]
The hydrogen peroxide monitor using the iodine electrode titration method puts ultrapure water of a sample in an acidic solution in which sodium thiosulfate and potassium iodide are dissolved, and quantitatively analyzes iodine ions with hydrogen peroxide in ultrapure water. The hydrogen peroxide concentration is obtained by oxidizing and quantitatively reacting iodine produced by the oxidation with sodium thiosulfate.
[0008]
Hydrogen peroxide generates iodine by quantitatively oxidizing iodine ions in an acidic solution containing a reaction catalyst.
[0009]
H ₂ O ₂ + 2KI → I ₂ + 2KOH
[0010]
The produced iodine reacts quantitatively with sodium thiosulfate in acidic solution.
[0011]
I ₂ + 2Na ₂ O ₃ → 2NaI + Na ₂ S ₄ O ₆
[0012]
As a commercially available hydrogen peroxide monitor that can detect hydrogen peroxide in ultrapure water up to 5 ppb using this principle, the “Process Titrator AHP-310L Hydrogen Peroxide Full-Automatic Analyzer” (Hiranuma Sangyo Co., Ltd.) )).
[0013]
[Problems to be solved by the invention]
The present invention has been made on the basis of such knowledge, and this high-accuracy trace hydrogen peroxide monitor is disposed at an arbitrary location of the ultrapure water production apparatus, particularly at the downstream side of the activated carbon treatment apparatus or in the vicinity of the use point. Thus, an object of the present invention is to provide an ultrapure water producing apparatus that prevents ultrapure water containing hydrogen peroxide from flowing downstream when hydrogen peroxide exceeds a reference value.
[0014]
[Means for Solving the Problems]
The ultrapure water production method of the present invention includes a pretreatment system for removing suspended substances contained in raw water, and treating the treated water of the pretreatment system to form ultrapure water. The primary pure water system to be stored and the ultrapure water stored in the ultrapure water tank are processed by a processing means including an ultraviolet oxidizer and an ion exchanger and supplied to the use point. A secondary pure water system that recirculates pure water to the ultrapure water tank, and the pretreatment system or primary pure water through a processing means that collects the ultrapure water used at the use point and includes an activated carbon treatment device. In an ultrapure water production apparatus having a recovery line to be refluxed to the system, at least 10 ppb, preferably at least 5 disposed at any location from the primary pure water system to the recovery line And hydrogen peroxide monitor capable of detecting the ultrapure water of hydrogen peroxide up to pb, is characterized by having a branch pipe provided with a switching valve provided on the downstream side of the hydrogen peroxide monitor.
[0015]
It is particularly preferable that the hydrogen peroxide monitor and the branch pipe are arranged in the vicinity of the use point of the secondary pure water system, particularly on the downstream side of the activated carbon treatment apparatus in the recovery line.
[0016]
As the activated carbon treatment apparatus used in the ultrapure water production apparatus of the present invention, particularly as the activated carbon treatment apparatus used in the recovery line, at least two kinds of activated carbons having different resolutions against hydrogen peroxide are used, and those having lower resolution against hydrogen peroxide. It is suitable to arrange the activated carbon having the higher resolution against hydrogen peroxide on the upstream side. Activated carbon having a low resolution for hydrogen peroxide is used for ordinary water treatment, and examples thereof include coconut shell activated carbon and coal-based activated carbon. These activated carbons have innumerable pores of about 10 to 10000 A (most of which are 10 to 20 A) inside and have a specific surface area of about 500 to 1500 m 2. In addition, the pore distribution and specific surface area of activated carbon in the present specification are values measured by an adsorption method using a nitrogen gas (N ₂ ), an argon gas (Ar), or the like, or a mercury intrusion method.
[0017]
The activated carbon used for these normal water treatments is, for example, when hydrogen peroxide of 10 mg / l is passed in pure water at SV = 10 h ⁻¹ , the hydrogen peroxide in the treated water is 0.1-1 mg / l ( = × 1000 μg / l). In addition, said SV is the meaning of space velocity (Space Velocity), and is represented by SV = flow velocity (l (liter) / h (hour)) / filled activated carbon amount (l).
[0018]
The activated carbon having a higher resolution with respect to hydrogen peroxide used in the present invention increases the proportion of pores of 20 to 1000 A (A = 10 nm) to 10 Vol% or more, preferably 20 Vol% or more, or platinum, palladium, A decomposition catalyst such as silver is supported to increase the resolution for hydrogen peroxide. When hydrogen peroxide of 10 mg / l, for example, in pure water is passed at SV = 10 h ⁻¹ , hydrogen peroxide in the treated water is used. Is capable of degrading to 50 μg / l, preferably 10 μg / l, more preferably less than 5 μg / l.
[0019]
An example of the activated carbon having improved pore resolution and improved resolution against hydrogen peroxide is CENTAUR (trade name) sold by Calgon Carbon Corporation. Moreover, as activated carbon which carried | supported the hydrogen peroxide high decomposition catalyst, Kuraray Chemical Co., Ltd. T-SB (brand name) is illustrated.
[0020]
As the activated carbon having a lower resolution with respect to hydrogen peroxide in the present invention, ordinary activated carbon conventionally used for water treatment can be used.
[0021]
The ion exchange apparatus used for the ion exchange treatment of the present invention includes a mixed bed type ion exchange tower using a cation / anion exchange resin or a single bed tower using a cation exchange resin and a single bed tower using an anion exchange resin. An electric ion exchange resin apparatus that continuously performs combination, ion adsorption and regeneration is exemplified.
[0022]
The ion exchange apparatus used for the ion exchange treatment of the present invention includes a mixed bed type ion exchange tower using a cation / anion exchange resin or a single bed tower using a cation exchange resin and a single bed tower using an anion exchange resin. An electric ion exchange resin apparatus that continuously performs combination, ion adsorption and regeneration is exemplified.
[0023]
The hydrogen peroxide decomposition performance of the high-performance activated carbon depends on the pH of the water to be treated, and the neutral or alkaline decomposition performance of hydrogen peroxide is higher than that of acid. Therefore, if necessary, an alkaline agent such as casisoda may be added to make the pH alkaline before passing the activated carbon. In addition, ultrapure water used in semiconductor manufacturing contains acidic chemicals. In this case, it is conceivable to add an alkali agent as described above, but if it is about 30 ppm hydrogen peroxide, it can be decomposed without any problem even if the pH is low.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Next, examples of the present invention will be described in detail.
[0025]
[Example 1]
FIG. 1 is a diagram schematically showing an embodiment of the ultrapure water production apparatus of the present invention. The apparatus includes a primary pure water system 1 and a secondary pure water system 2 including an ultrapure water tank 21 that stores ultrapure water produced by the primary pure water system 1. The pre-processing system in the previous stage is not shown.
[0026]
The secondary pure water system 2 includes an ultrapure water tank 21, an ultraviolet oxidation device 22, non-regenerative ion exchange treatment devices 23a and 23b, an ultrafiltration membrane device 24, a use point 25, and a pipe 27 including a return line 27 '. A hydrogen peroxide monitor 28 capable of measuring hydrogen peroxide up to 10 ppb is installed between the ultrafiltration membrane device 24 and the use point 25. The pipe 27 leading to the use point 25 is provided with electromagnetic opening / closing valves 29a and 29b. When the hydrogen peroxide monitor 28 detects a predetermined concentration of hydrogen peroxide, the electromagnetic opening / closing valve 29a is closed and 29b is opened. This ultrapure water does not go to the use point.
[0027]
FIG. 2 shows the hydrogen peroxide concentration measured at each part when the secondary pure water system 2 is in a normal state. Since the secondary pure water system 2 is a circulation line, when the performance of the non-regenerative ion exchange apparatus deteriorates, for example, when primary pure water mixed with hydrogen peroxide flows from the primary pure water system 1 in FIG. As shown in the figure, the concentration of hydrogen peroxide in the entire secondary pure water system becomes high. In the figure, the solid line indicates when primary pure water that does not contain hydrogen peroxide flows (when recovered water is shut off), and the chain line indicates when primary pure water that contains hydrogen peroxide flows (when recovered water flows).
[0028]
In this embodiment, a hydrogen peroxide monitor 28 capable of measuring up to 5 ppb is installed between the ultrafiltration membrane device 24 and the use point 25. However, the ultraviolet oxidation device 22 and the non-regenerative ion exchange treatment device 23b are connected to each other. It is also possible to install a hydrogen peroxide monitor 28 between the primary pure water system 1 and the secondary pure water system 2.
[0029]
Example 2
FIG. 4 schematically shows a main part of another embodiment of the present invention. A supply path 31a is a supply path for supplying water to be treated to the primary pure water system 1 from a pretreatment system (not shown). The supply path 31b is a supply path for supplying the water to be treated to the primary pure water system 1 from the recovery line, for example, other than the pretreatment system.
[0030]
These supply paths 31 a and 31 b supply treated water in parallel to the primary pure water system 1, respectively, and the primary pure water generated in the primary pure water system 1 is supplied to the secondary pure water system 2. . Between the supply paths 31a and 31b and the primary pure water system 1, flow rate adjusting valves 32a and 32b are respectively inserted. In addition, a hydrogen peroxide monitor 28 capable of measuring hydrogen peroxide of up to 5 ppb is installed at an arbitrary location of the primary pure water system 1, and when this hydrogen peroxide monitor 28 detects a predetermined concentration of hydrogen peroxide. The opening ratios of the flow rate adjusting valves 32a and 32b are adjusted to change the supply ratios of the supply paths 31a and 31b, or one of them is closed.
[0031]
In this embodiment, for example, if the supply path 31b is a recovery line in which hydrogen peroxide may be mixed, when the hydrogen peroxide monitor 28 detects a predetermined concentration of hydrogen peroxide, the flow rate adjustment valve 32a Opening / closing control is performed so that the opening degree is increased and the flow rate adjusting valve 32b is closed.
[0032]
When the hydrogen peroxide monitor 28 detects a predetermined concentration of hydrogen peroxide, this hydrogen peroxide is caused by the recovered water from the secondary pure water system 2, so the supply path 21 is adjusted by adjusting the flow rate adjustment valve. , 22 can be changed to reduce the hydrogen peroxide concentration below the standard.
[0033]
Example 3
In this embodiment, as shown in FIG. 5, hydrogen peroxide monitors 28a and 28b capable of measuring hydrogen peroxide of up to 5 ppb are installed at arbitrary locations of the primary pure water system 1 and the secondary pure water system 2, Branch pipes 41a and 41b are provided in the main pipe 40 between the pretreatment system 30 and the primary pure water system 1 and between the primary pure water system 1 and the secondary pure water system 2, respectively, and electromagnetic switching is performed on the downstream side of the branch part. Valves 32a, 32b, 33a, 33b are installed.
[0034]
Also in this embodiment, when the hydrogen peroxide monitor 28a or 28b detects a predetermined concentration of hydrogen peroxide, the electromagnetic open / close valve 32b or 33b of the branch pipes 41a and 41b on the upstream side is opened to open the electromagnetic open / close valve 32a or 32b closes and it suppresses that the to-be-processed water containing hydrogen peroxide flows into the secondary pure water system 2. FIG.
[0035]
Example 4
In this embodiment, as shown in FIG. 6, hydrogen peroxide monitors 28a and 28b are installed between the pretreatment system 30 and the primary pure water system 1, and the primary treatment between the pretreatment system 30 and the primary pure water system 1 is the primary. The main pipe 40 between the pure water system 1 and the secondary pure water system 2 is provided with branch pipes 41a and 41b, respectively, and electromagnetic open / close valves 32a, 32b, 33a and 33b are respectively installed downstream of the branch parts. is there.
[0036]
According to this embodiment, the quality of the water to be treated flowing into the primary pure water system 1 and the secondary pure water system 2 can be managed as in the case of the third embodiment.
[0037]
Example 5
In this embodiment, as shown in FIG. 7, hydrogen peroxide monitors 28 a, 28 b, and 28 c are installed in the upstream and downstream piping and the primary pure water system 1 across the branch pipe 51 provided in the recovery line 50. It is a thing. In this embodiment, the electromagnetic open / close valve 32a provided in the recovery line 50 and the electromagnetic open / close valve 32b provided in the branch pipe 51 can be controlled from any of the hydrogen peroxide monitors 28a, 28b, 28c.
[0038]
According to this embodiment, since the electromagnetic on-off valve is controlled by hydrogen peroxide monitors installed at a plurality of locations, the possibility that the treated water containing hydrogen peroxide will be supplied to the secondary pure water system is further reduced. Become.
[0039]
【The invention's effect】
As is clear from the above examples, according to the present invention, it is possible to almost completely remove the residual hydrogen peroxide in the ultrapure water used at the use point, thereby controlling the concentration of functional water. Becomes easy.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing the configuration of an embodiment of the present invention.
FIG. 2 is a graph showing the hydrogen peroxide concentration of each part in the secondary pure water system.
FIG. 3 is a graph showing the effect of the present invention.
FIG. 4 is a diagram schematically showing the configuration of another embodiment of the present invention.
FIG. 5 is a diagram schematically showing the configuration of another embodiment of the present invention.
FIG. 6 is a diagram schematically showing the configuration of another embodiment of the present invention.
FIG. 7 is a diagram schematically showing the configuration of another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Primary pure water system, 2 ... Secondary pure water system, 21 ... Ultrapure water tank, 22 ... Ultraviolet oxidizer, 23a, 23b ... Non-regenerative ion exchange treatment device, 24 ... Ultra Filtration membrane device, 25 ... use point, 27 '... return line, 28 ... hydrogen peroxide monitor, 29 ... electromagnetic on-off valve

Claims (2)

A pretreatment system for removing suspended substances contained in raw water; a primary pure water system for treating the treated water of the pretreatment system to form ultrapure water; and storing the ultrapure water in an ultrapure water tank; The ultrapure water stored in the pure water tank is treated with processing means including an ultraviolet oxidizer and an ion exchanger and supplied to the use point, and the ultrapure water not used at the use point is returned to the ultrapure water tank. A secondary pure water system to be recovered, and a recovery line for recovering the ultrapure water used at the use point and returning it to the pretreatment system or the primary pure water system through a processing means including an activated carbon processing apparatus. In pure water production equipment,
A hydrogen peroxide monitor capable of detecting hydrogen peroxide in ultrapure water of at least 10 ppb disposed at any location from the primary pure water system to the recovery line, and downstream or upstream of the hydrogen peroxide monitor An ultrapure water production apparatus comprising: a branch pipe provided with a switching valve provided on the side. 2. The apparatus for producing ultrapure water according to claim 1, wherein the hydrogen peroxide monitor and the branch pipe are arranged immediately before a use point of the secondary pure water system and / or an activated carbon treatment device of a recovery line. .

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