JP2004167308A - Ultrapure water making apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrapure water making apparatus for making ultrapure water extremely reduced in the concentration of metals. <P>SOLUTION: In a primary pure water making apparatus having a pretreatment system 1, a primary pure water making apparatus 10 and a secondary pure water making apparatus 20, the heat exchanger of the secondary pure water making apparatus 20 is transferred to be provided in the primary pure water making apparatus 10. The respective devices of the secondary pure water making apparatus 10 are made of a synthetic resin or lined with the synthetic resin. A part of the return ultrapure water from a use point 40 is returned to the primary pure water making apparatus 10 to be controlled in its temperature. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrapure water production apparatus, and more particularly to an ultrapure water production apparatus capable of producing ultrapure water having a very low metal concentration.
[0002]
[Prior art]
As shown in FIG. 2, the ultrapure water used as the semiconductor cleaning water is a raw water (raw water) composed of a pretreatment system 1, a primary pure water production apparatus 10, and a secondary pure water production apparatus 20. Manufactured by treating industrial water, city water, well water, etc.). In FIG. 2, the role of each system is as follows.
[0003]
In the pretreatment system 1 comprising agglomeration, pressurized flotation (precipitation), filtration (membrane filtration) apparatus and the like (in this conventional example, agglomeration filtration apparatus), suspended substances and colloidal substances in raw water are removed. In this process, it is also possible to remove high molecular organic substances, hydrophobic organic substances and the like.
[0004]
In a primary pure water production apparatus 10 including a pretreated water tank 11, a reverse osmosis membrane separation device (RO device) 12, an ion exchange device (such as a mixed bed type or a four-bed five-column type) 13, and a deaeration device 14. Removes ions and organic components from raw water. The reverse osmosis membrane separator 12 removes salts and removes ionic and colloidal TOC. The ion exchange device 13 removes TOC components adsorbed or ion exchanged by an ion exchange resin while removing salts. In the deaeration device 14, inorganic carbon (IC) and dissolved oxygen are removed.
[0005]
The primary pure water produced by the primary pure water production apparatus is sent to the secondary pure water production apparatus 20 via the pipe 16. The secondary pure water production apparatus 20 includes a pure water tank 21, a pump 22, a heat exchanger 23, a low-pressure ultraviolet oxidation apparatus (UV apparatus) 24, an ion exchange apparatus 25, and an ultrafiltration membrane (UF membrane) separation apparatus 26. I have. In the low-pressure ultraviolet oxidizer 24, TOC is decomposed into an organic acid and further to CO ₂ by 185 nm ultraviolet rays emitted from a low-pressure ultraviolet lamp. Organic substances and CO ₂ generated by the decomposition are removed by the ion exchange device 25 at the subsequent stage. In the ultrafiltration membrane separation device 26, the fine particles are removed, and the outflow particles from the ion exchange resin are also removed.
[0006]
The ultrapure water produced by the secondary pure water production apparatus 20 is sent to the use point 40 via the pipe 30, and the unused ultrapure water is returned to the tank 21 via the pipe 50. Note that a booster pump may be installed in the pipe 30.
[0007]
The heat exchanger 23 is for maintaining the temperature of the ultrapure water sent from the secondary pure water production apparatus 20 to the use point 40 at a predetermined temperature (for example, about 25 ° C.).
[0008]
In general, the ultrapure water produced by the secondary pure water production apparatus 20 is supplied to the use point, and surplus ultrapure water (unused) is returned from the use point 40 to the secondary pure water production apparatus 20 and again It is processed by the secondary pure water production apparatus 20 and circulates while maintaining a certain ultrapure water quality. And since it does not stagnate by always circulating, the reproduction of microorganisms is suppressed. During this circulation, the heat exchanger 23 removes the temperature of the circulating ultrapure water due to the heat of the pump and the ultraviolet irradiation lamp of the low-pressure ultraviolet oxidizer 24, and the temperature of the circulating ultrapure water is set to a predetermined temperature. To maintain.
[0009]
By the way, with the miniaturization and high integration of LSIs, the influence of impurities in ultrapure water as cleaning water in the manufacture of VLSI chips is increasing.
[0010]
In LSIs with an integration level of 1 megabit or less, there was no trouble with semiconductor products (LSIs, etc.) due to the quality of conventional ultrapure water, but now the degree of integration of LSIs has improved. Product defects (mainly lifetime defects) due to metals have occurred.
[0011]
As a result of investigation and analysis, the metal in the raw water was removed by the ultrapure water production system, but it was confirmed that the metal generated (eluting) in the secondary pure water production system was mixed in the ultrapure water. As a result of the trace analysis, the metal concentration of the ultrapure water quality is about 0.1 to 5 ng / L.
[0012]
The metal eluted in ultrapure water is combined with a small amount of oxygen to form colloidal particles, which cannot be removed by the ion exchange device of the secondary pure water production system, and is captured by the ultrafiltration membrane in the subsequent stage. Contaminates the membrane surface. It is recognized that the metal concentrated on the ultrafiltration membrane surface is dissolved again in ultrapure water to increase the metal concentration in the ultrapure water. It was found to be higher.
[0013]
As a result of investigating metal elution from equipment in secondary pure water production equipment, it was found that the main cause of metal concentration in ultrapure water was metal elution from supply pumps, heat exchangers, and booster pumps. It was.
[0014]
Conventionally, the pump 22 in the secondary pure water production apparatus 20 has a water contact surface made of stainless steel.
[0015]
The heat exchanger 23 is installed to control ultrapure water at about 24 ° C. The heat exchanger 23 currently used is made of stainless steel or titanium excellent in corrosion resistance, but has a trace amount of metal elution.
[0016]
Although it is conceivable to use a heat exchanger lined with a fluororesin or the like for preventing metal elution (Japanese Patent No. 3172730), the thermal conductivity is poor and the size becomes large (volume).
[0017]
[Patent Document 1]
Japanese Patent No. 3172730 [0018]
[Problems to be solved by the invention]
An object of the present invention is to solve such problems of the prior art and to provide an ultrapure water production apparatus capable of producing ultrapure water having a remarkably low metal concentration.
[0019]
[Means for Solving the Problems]
The ultrapure water production apparatus of the present invention produces primary pure water by passing water through a primary pure water production apparatus, and produces ultrapure water by passing this primary pure water through a secondary pure water production apparatus. In the pure water production apparatus, all or most of the water contact portion of the secondary pure water production apparatus is made of a non-metallic material.
[0020]
According to the present invention, since the elution of metal from the secondary pure water production apparatus is prevented, the metal concentration in the ultrapure water becomes extremely low.
[0021]
In the present invention, it is preferable that the water supply pump has a drainage mechanism in which the water contact portion is made of a non-metallic material and the water passing through the pump bearing portion is discharged without being mixed with the pump discharge water. According to this pump, the metal is prevented from eluting from the pump into pure water or ultrapure water, and the metal concentration in the ultrapure water is further reduced.
[0022]
In the present invention, the secondary pure water production apparatus is not provided with a heat exchanger, thereby preventing metal contamination in the ultrapure water caused by elution of metal from the heat exchanger of the secondary pure water production apparatus. You may make it do.
[0023]
For example, a secondary pure water production apparatus is provided with a heat exchanger by configuring the secondary pure water production apparatus with a pure water tank, a pump, an ultraviolet irradiation device, a membrane separation device, and a connecting means for connecting them. (In addition, if necessary, a booster pump may be further provided.) In this case, the heat exchanger may be installed in the primary pure water production apparatus, or may not be provided in either the primary pure water production apparatus or the secondary pure water production apparatus.
[0024]
In the present invention, the ultrapure water supply means for supplying ultrapure water from the secondary pure water production apparatus to the use point and the water contact of the return pipe for returning the ultrapure water unused at the use point to the secondary pure water production apparatus. The part is preferably made of a non-metallic material. In this way, the metal is not eluted into the ultrapure water supplied to the use point, and the metal is prevented from being eluted into the unused ultrapure water that is returned from the use point and reused. The In addition, as this ultrapure water supply means, piping or the pump and valve provided in this piping are illustrated.
[0025]
In this invention, you may provide the return means for returning a part of ultrapure water returned via return piping to the said primary pure water manufacturing apparatus. This configuration is particularly suitable when the heat exchanger is provided in the primary pure water production apparatus. In this case, the temperature of the secondary pure water production apparatus can be adjusted by providing means for controlling the amount of ultrapure water returned to the primary pure water production apparatus by the return means.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a system diagram of an ultrapure water production apparatus according to an embodiment.
[0027]
In this embodiment, in the conventional ultrapure water production apparatus of FIG. 2, a heat exchanger 15 is provided between the tank 11 and the reverse osmosis membrane separation apparatus 12, and water to be treated in the primary pure water production apparatus 10 is supplied. The temperature is lowered. In the secondary pure water production apparatus 20, the heat exchanger 23 is omitted, and the water supplied from the pump 22 is directly supplied to the low-pressure ultraviolet oxidizer 24. In the secondary pure water production apparatus 20, a pump 27 (a pressure pump) is provided in a pipe 30 that supplies ultrapure water from the ultrafiltration membrane separation apparatus 26 to the use point 40.
[0028]
A pipe 50 for returning unused ultrapure water from the use point 40 includes a pipe 51 for returning the ultrapure water to the tank 11 of the primary pure water production apparatus and a pipe 52 for returning the ultrapure water to the pure water tank 21 of the secondary pure water production apparatus. It is divided into and. One or both of the pipes 51 and 52 are provided with a flow rate adjusting means (not shown) such as a flow rate adjusting valve.
[0029]
The tank 21, the pump 22, the low-pressure ultraviolet oxidizer 24, the ion exchange device 25, the ultrafiltration membrane separator 26, and the pump 27, which are the components constituting the secondary pure water production apparatus 20, The water connection member and the water contact surfaces of the pipes 30, 50, 51, 52 are all made of synthetic resin lining or made of a synthetic resin member. The tank 21, the water flow connecting member, and the pipes 30, 50, 51, 52 may be made of synthetic resin as a whole.
[0030]
Other configurations in FIG. 1 are the same as those in FIG. 2, and the same reference numerals denote the same parts.
[0031]
In the ultrapure water production apparatus configured as described above, the raw water is subjected to processing such as coagulation filtration in the pretreatment system 1, and then returned unused ultrapure water from the pipe 51 is mixed in the tank 11. Next, the water to be treated is cooled by the heat exchanger 15 and then flows in the order of the reverse osmosis membrane separation device 12, the ion exchange device 13, and the deaeration device 14. Thereafter, the water is sent to the pure water tank 21 of the secondary pure water production apparatus 20 through the pipe 16, and the returned unused ultrapure water from the pipe 52 is mixed here. The water in the tank 21 is processed by the pump 22, the low-pressure ultraviolet oxidizer 24, the ion exchange device 25, and the ultrafiltration membrane separator 26 to become ultrapure water, and the use point 40 is supplied from the pump 27 through the pipe 30. Water is sent to
[0032]
In this embodiment, since the water contact surface of each device of the secondary pure water production apparatus 20 is a synthetic resin, the metal does not elute and the metal concentration in the ultrapure water is extremely low.
[0033]
Further, the heat exchanger is arranged not in the secondary pure water production apparatus 20 but in the primary pure water production apparatus 10, and the heat exchanger 15 has a water contact surface (heat exchange surface) as a metal surface not subjected to synthetic resin lining. Yes. For this reason, the heat exchange characteristics of the heat exchanger 15 are extremely good, and the heat exchanger does not increase in size.
[0034]
Examples of the synthetic resin include polyethylene, polypropylene, polyether ether ketone, polyvinyl chloride, polysulfone, and the like, in addition to fluorine resins such as polytetrafluoroethylene and polyvinyl difluoride. As described above, this synthetic resin may be used as a lining material, or may be used as a constituent material of equipment or members. When used as a lining material, the metal material to be lined is preferably a highly corrosion-resistant metal material such as stainless steel, titanium, or a titanium alloy, but is not limited thereto.
[0035]
The synthetic resin may be a fiber reinforced synthetic resin (FRP) reinforced with glass fiber, carbon fiber or the like. This is suitable as a constituent material of the tank.
[0036]
The pure water tank 21 is specifically exemplified by those made of fluororesin, polyethylene, and stainless steel lined with polypropylene.
[0037]
Examples of the pipe include those made of fluororesin, polyether ether ketone, and polyvinyl chloride.
[0038]
The container of the low-pressure ultraviolet oxidizer 24 is preferably made of stainless steel lined with a fluororesin excellent in ultraviolet resistance. Since the water contact surface of the container of the low-pressure ultraviolet oxidizer 24 is small, the synthetic resin lining may be omitted and a stainless steel surface may be used. The lamp protection surface is preferably made of quartz.
[0039]
The container of the ion exchange device 25 is preferably composed of FRP, synthetic resin lining stainless steel, or the like. The ion exchange device 25 is preferably a mixed bed ion exchange device filled with a cation exchange resin and an anion exchange resin, and may be either a regenerative type or a non-regenerative type. It may be an electric regenerative ion exchange device.
[0040]
The container of the ultrafiltration membrane separator 26 is preferably made of polysulfone, FRP, or synthetic resin lining stainless steel.
[0041]
The pumps 22 and 27 are preferably made of a synthetic resin-lined water contact surface. For example, a synthetic resin-lined stainless steel is applied to the water contact surface of a low dust generation pump such as a clean canned motor pump, clean vortex pump, or clean magnet pump. That is suitable. Further, this pump is preferably configured so that the water passing through the bearing portion is discharged so as not to be mixed with the ultrapure water. An example of this pump will be described later with reference to FIG.
[0042]
In the embodiment of FIG. 1, the heat exchanger of the secondary pure water production apparatus 20 is omitted, and the heat exchanger 15 is installed in the primary pure water production apparatus 10 instead. The heat exchanger has a larger water contact area than other equipment of the secondary pure water production device, and when incorporated in the secondary pure water production device, the metal elution amount is the secondary pure water production device. Most often.
[0043]
Therefore, in the embodiment of FIG. 1, the heat exchanger is moved from the secondary pure water production apparatus 20 to the primary pure water production apparatus 10. In this embodiment, in order to control the temperature of the ultrapure water supplied from the secondary pure water production apparatus 20 to the use point 40, a part of the ultrapure water from the ultrapure water return pipe 50 is piped 51. Then, the temperature is returned to the primary pure water production apparatus 10, and the temperature is lowered by the heat exchanger 15 of the primary pure water production apparatus 10. By adjusting the amount of ultrapure water to be divided into the pipe 51 and the pipe 52, the temperature of the ultrapure water fed from the secondary pure water production apparatus 20 is adjusted.
[0044]
In the embodiment of FIG. 1, the heat exchanger 15 is provided in the primary pure water production apparatus 10, but the heat exchanger of the primary pure water production apparatus 10 may be omitted depending on the temperature of raw water. For example, when the temperature of the raw water flowing into the primary pure water production apparatus 10 through the pretreatment system 1 is about 15 ° C., the secondary pure water from the primary pure water production apparatus 10 is mixed with the returned ultrapure water from the pipe 51. The temperature of the primary pure water sent to the pure water production apparatus 20 is considerably lower than 25 ° C. Even if the return ultrapure water from the pipe 52 is mixed in the pure water tank 21, it is still about 20 ° C. Become. Thereby, the water temperature of the ultrapure water sent from the secondary pure water manufacturing apparatus 20 to the use point 40 can be set to about 25 degreeC.
[0045]
When a part of the returned ultrapure water is returned to the primary pure water production apparatus 10, the water temperature in the primary pure water production apparatus 10 rises. Due to this rise in water temperature, the reverse osmosis membrane separation of the primary pure water production apparatus 10 occurs. The effect that the permeated water amount (flux) of the apparatus 12 increases is obtained. Further, by adding a part of the returned ultrapure water to the raw water of the primary pure water production apparatus 10, the quality of the raw water of the primary pure water production apparatus 10 is improved and added to each treatment device of the primary pure water production apparatus 10. An effect of reducing the load is also obtained.
[0046]
However, it is desirable that at least a part of the return ultrapure water flowing through the pipe 50 is returned to the secondary pure water production apparatus 20. This is because the quality of the returned ultrapure water is better than the primary pure water from the primary pure water production apparatus 10.
[0047]
By returning at least a part of the high-quality returned ultrapure water to the secondary pure water production apparatus 20, the quality of the ultrapure water sent from the secondary pure water production apparatus 20 to the use point 40 is improved. .
[0048]
In the embodiment shown in FIG. 1, the heat exchanger of the secondary pure water production apparatus 20 is omitted. However, when the synthetic resin lining is applied to the heat exchanger, the secondary pure water production apparatus 20 performs heat exchange. A vessel may be provided. However, if the synthetic resin lining is applied, the heat exchange characteristics deteriorate, and the heat exchanger becomes large. Therefore, it is preferable to omit the heat exchanger from the secondary pure water production apparatus 20.
[0049]
Next, with reference to FIG. 3, the suitable example of the pump installed in the secondary pure water manufacturing apparatus 20 is demonstrated.
[0050]
An impeller 62 is disposed in the impeller housing 60. The impeller 62 is rotated by a shaft 64. A water inlet 66 is provided at the center of the housing 60, and an outlet 68 is provided at the outer periphery.
[0051]
The shaft 64 passes through a sealing water housing 70 provided adjacent to the impeller housing 60. The shaft 64 and the housing 70 are sealed by a mechanical seal mechanism having a seal ring 72. A retainer ring 74 is installed between the outer periphery of the seal ring 72 and the housing 70. The seal ring 72 is urged to the left in the drawing by a spring 76. There is a slight gap between the seal ring 72 and the shaft 64, and the water flowing out through the throat portion 80 and this gap is discharged out of the pump from the drain port 82 of the housing 70. A synthetic resin lining 86 is applied to the inner surface of the housing 60, and a synthetic resin lining 84 is also applied to the outer peripheral surfaces of the impeller 62 and the tip of the shaft 64. The synthetic resin for lining is preferably a fluororesin, polypropylene, polyetheretherketone, but is not limited thereto.
[0052]
【Example】
Hereinafter, examples and comparative examples will be described.
[0053]
1 and 2, the same raw water is passed through to produce ultrapure water, the Fe concentration in the ultrapure water from the secondary pure water production apparatus 20 is measured, and the results are shown. This is shown in FIG.
[0054]
In addition, the heat exchangers 15 and 23 of FIG. 1 and FIG. 2 are the same.
[0055]
In FIG. 1 according to the embodiment, the tank 21, the low-pressure ultraviolet oxidation device 24, the ion exchange device 25, and the ultrafiltration membrane separation device 26 are all lined with fluororesin. In FIG. 2, this fluororesin lining is not applied. Moreover, in FIG. 1, what was shown in FIG.
[0056]
As shown in FIG. 4, according to the example, it is recognized that the Fe concentration is lower than that in the comparative example, and in particular, in the example, it is recognized that the Fe concentration immediately after startup is significantly lower than that in the comparative example.
[0057]
That is, in the ultrapure water production apparatus of the comparative example, the iron concentration in the ultrapure water at the start-up is 5 ng / L or more, and the iron concentration decreases with time, but the steady iron concentration (0.1 ng) / L or less) takes about one month. On the other hand, in the example, the measured value is 0.1 ng / L or less from the initial stage of startup.
[0058]
Further, when the iron concentration at the outlet of the pump 22 at the initial stage of startup (3 to 5 minutes) was measured, it was 21 ng / L in the comparative example, whereas it was 0.1 ng / L or less in the example, and the iron from the pump It was found that the elution of was significantly less.
[0059]
【The invention's effect】
As described above, according to the present invention, it is possible to produce ultrapure water having an extremely low metal concentration.
[Brief description of the drawings]
FIG. 1 is a system diagram of an ultrapure water production apparatus according to an embodiment.
FIG. 2 is a system diagram of an ultrapure water production apparatus according to a conventional example.
FIG. 3 is a sectional view of a pump used in the embodiment.
FIG. 4 is a graph showing measurement results of Examples.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Primary pure water manufacturing apparatus 20 Secondary pure water manufacturing apparatus 40 Use point 50,51,52 Ultrapure water return piping 60,70 Housing 62 Impeller 82 Drain port 84,86 Synthetic resin lining

Claims (8)

In an ultrapure water production apparatus for producing primary pure water by passing water through a primary pure water production apparatus and producing ultrapure water by passing this primary pure water through a secondary pure water production apparatus,
An ultrapure water production apparatus characterized in that all or most of the water contact portion of the secondary pure water production apparatus is made of a non-metallic material. The pump for water supply according to claim 1, wherein the water contact portion is made of a non-metallic material and has a drainage mechanism that discharges the water passing through the pump bearing portion without mixing it with the pump discharge water. Ultrapure water production equipment characterized by The ultrapure water according to claim 1 or 2, wherein the secondary pure water production apparatus comprises a pure water tank, a pump, an ultraviolet irradiation device, a membrane separation device, and a connecting means for connecting them. Water production equipment. 4. The ultrapure water production apparatus according to claim 1, wherein the heat exchanger is installed in the primary pure water production apparatus and is not installed in the secondary pure water production apparatus. 5. The ultrapure water supply means for supplying ultrapure water from the secondary pure water production apparatus to a use point and the production of secondary ultrapure water unused at the use point according to any one of claims 1 to 4. It has a return pipe to return to the equipment,
An ultrapure water production apparatus, wherein the ultrapure water supply means and the water contact portion of the return pipe are made of a non-metallic material. 6. The ultrapure water production apparatus according to claim 5, further comprising a return means for returning a part of the ultrapure water returned through the return pipe to the primary pure water production apparatus. 7. The ultrapure water production apparatus according to claim 6, further comprising means for controlling the amount of ultrapure water returned to the primary pure water production apparatus by the return means. 8. The apparatus for producing ultrapure water according to claim 1, wherein the nonmetallic material is a synthetic resin.

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