JP2004050048A - Washing device for piping and ultrapure water making system provided with washing device for piping - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a washing device for piping which can drastically shorten the time required for initial rise after construction and an ultrapure water making apparatus using the same. <P>SOLUTION: A compressed gas supplied to a piping to be washed through an automatic stop valve for supplying the compressed gas from a supply source for compressed gas and an ultrapure water for washing supplied to the piping to be washed through an automatic stop valve for supplying the ultrapure water from a supply source for the ultrapure water for washing are alternately supplied to the piping to be washed by alternately opening and closing the automatic stop valve for supplying the compressed gas and the automatic stop valve for supplying the ultrapure water by an automatic stop valve controller for a prescribed interval, by which the deposits sticking to the inner wall of the piping to be washed are washed away. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pipe cleaning apparatus and an ultrapure water producing apparatus provided with the pipe cleaning apparatus, and particularly to a pipe cleaning apparatus for supplying ultrapure water used for manufacturing a semiconductor integrated circuit and the like, and an ultrapure water equipped with the pipe cleaning apparatus. Related to water production equipment.
[0002]
[Prior art]
Ultrapure water is highly purified and highly purified water obtained by repeatedly removing impurities from water containing various impurities. Particularly, in the manufacture of semiconductor devices that have been significantly increased in scale and miniaturization, ultrapure water of extremely high purity has been required. The design rule for microfabrication of semiconductor devices has already reached 0.13 μm, and ultrapure water used in the manufacture of semiconductor devices under this design rule has a particle diameter of less than one tenth of 0.13 μm. In such ultrapure water, the number of fine particles of 0.05 μm or more contained in the ultrapure water is specified, for example, to 100 particles / L or less.
[0003]
When the ultrapure water supply device for supplying such ultrapure water starts up, many fine particles are present at first. For this reason, conventionally, a start-up operation has been performed for a predetermined time, and these particles have been sequentially discharged from the inside of the apparatus and removed to reach a target value.
[0004]
However, recently, as described above, the state in which the number of fine particles contained in ultrapure water is extremely small has become the goal of reaching ultrapure water, and the time required to reach this target is one week or more, or one month or more. It took an extremely long time to start up the ultrapure water system. For these reasons, a method capable of appropriately reducing the rise time in the operation of the ultrapure water apparatus has been strongly desired.
[0005]
In the ultrapure water apparatus, an ultrafiltration membrane (UF) is used at the end of the apparatus, and the ultrapure water generated by passing through the ultrafiltration membrane is carried to each use point. At that time, almost all the fine particles including viable bacteria are removed in the UF, and the removal rate of the fine particles in the UF is very close to 100%. For example, in a test in which the removal performance was confirmed using 0.1 μm latex standard particles, the removal performance was 99.999999% or more, and virtually no leakage of fine particles from the UF was detected. The fine particles present on the supply side of the UF are thus removed by the UF, and almost no fine particles are present on the UF permeate side.
[0006]
Therefore, when the apparatus is started up, for example, after the installation of the apparatus, the fine particles to be removed as remaining fine particles are limited to those remaining after being attached to the pipe from the UF to the point of use. It takes more than one week or one month for the number of fine particles in the ultrapure water supplied to the point of use to decrease to the target value by performing the normal operation of flowing the ultrapure water filtered by the UF through this pipe. This is because it takes such a long time to reduce the fine particles adhering to the piping in this portion.
[0007]
[Problems to be solved by the invention]
The present invention solves such a problem and significantly reduces the time required for startup after construction by providing a pipe cleaning device and a pipe cleaning device that can significantly reduce the time required for startup after construction. It is an object of the present invention to provide an ultrapure water production apparatus capable of performing the above.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a pipe cleaning device of the present invention includes a compressed gas supply pipe for supplying compressed gas from a compressed gas supply source to a pipe to be cleaned through a compressed gas supply automatic opening / closing valve, and an ultrapure cleaning pipe. A cleaning ultrapure water supply pipe for supplying ultrapure water for cleaning from the water supply source to the pipe to be cleaned through the ultrapure water supply automatic on / off valve for cleaning, the compressed gas supply automatic on / off valve and the ultrapure An automatic opening and closing valve control device for alternately opening and closing a water supply automatic opening and closing valve at a predetermined time interval is provided, and the compressed gas and the ultrapure water are alternately supplied to the pipe to be cleaned, The present invention is characterized in that the adhered matter adhering to the inner wall of the pipe to be cleaned is washed and removed.
[0009]
Further, the ultrapure water producing apparatus of the present invention comprises a compressed gas supply pipe for supplying a compressed gas from a compressed gas supply source to a pipe to be cleaned via a compressed gas supply automatic opening / closing valve, and a supply source of the ultrapure water for cleaning. A cleaning ultrapure water supply pipe for supplying cleaning ultrapure water to the pipe to be cleaned through a cleaning ultrapure water supply automatic opening / closing valve, the compressed gas supply automatic opening / closing valve, and the ultrapure water supply automatic opening / closing valve And an automatic on-off valve control device that alternately opens and closes at predetermined time intervals, and alternately supplies the compressed gas and the ultrapure water to the pipe to be cleaned, thereby providing a pipe for the pipe to be cleaned. It is characterized by having a pipe cleaning device for cleaning and removing deposits adhering to the inner wall.
[0010]
ADVANTAGE OF THE INVENTION According to this invention, the peeling of the ultrafine particle from the ultrapure water piping after construction can be accelerated, and as a result, the time required for starting the ultrapure water production apparatus can be significantly reduced. Here, in the present invention, the reason why the separation of the ultrafine particles can be accelerated is considered to be due to the following effects.
[0011]
When ordinary water is passed through the pipe, in the initial stage of the water flow, the fine particles existing in the pipe and the fine particles adhering to the inner surface of the pipe are flowed and removed by the physical force of the water flow. Subsequently, when the water flow becomes stable, the peeling and removal of the fine particles is much less. In a state where the water flow is stable, the particles that suddenly exfoliate cannot be explained merely by the force of the water flow. In such a case, the separation of the particles is dominated by local and sudden forces caused by turbulence or the like.
[0012]
FIG. 1 shows a state in which the fine particles adhered to the pipe are separated and removed. In FIG. 1A, the fine particles 100 are separated from the pipe by a local and sudden force, and are flowed and removed by the flow of water in FIG. 1B. At this time, the water is temporarily contaminated by the fine particles 100. In the drawings, an upward arrow 200 indicates the distribution of the flow velocity of water.
[0013]
Such an abrupt force is generated stochastically, for example, in the form of three probabilistic expected values of peeling out of 100 attached fine particles per hour. The ratio of the separation of the fine particles per unit time is referred to as a separation speed.
[0014]
Expressing this numerically, the rate at which the number c of attached fine particles decreases, that is, the peeling rate, can be expressed by (1 / c) dc / dt, and the fact that this amount is constant means that (1 / c) dc / Dt = −k, that is,
−dc / dt = kc
Is represented by
logc = −kt + C ₀
It becomes. Here, C ₀ is a constant.
[0015]
FIG. 2 shows a straight line represented by the above equation, with time t on the horizontal axis and logc on the vertical axis. Even if one value of k in the above equation is given for one factor, since all the factors actually overlap, they are added, and conceptually, as shown by a dotted line in FIG. Time change of logc.
[0016]
Since the number of the attached fine particles is finite, the number c of the attached particles decreases with time and approaches cello without limit. When starting from the same initial state, the time to approach the target value becomes shorter as the inclination is steeper and the peeling speed is higher.
[0017]
For example, assuming that the peeling rate is 3/100 per hour, it takes about three days for the particle concentration to drop by one digit at this peeling rate. If the separation speed of the fine particles from the inner wall of the pipe can be increased, the fine particles can be separated from the inner wall of the pipe in a short time, so that the rising time of the ultrapure water apparatus becomes short.
[0018]
This stripping speed does not double even if the flow rate in the pipe is doubled, and the effect of the increased flow rate is that the increased flow rate causes the content of the separated fine particles per unit volume in the effluent water. Is mainly obtained.
[0019]
The separation speed of the ultrafine particles is the smallest when the flow is laminar, and when the flow is turbulent, the separation speed of the ultrafine particles can be higher than in the case of laminar flow, but it is still not sufficient . In recent years, it has been required that the number of fine particles in ultrapure water is extremely small. In order to obtain ultrapure water that meets this requirement, even if the flow is turbulent, the rise time after construction is one week. It takes ~ 1 month.
[0020]
According to the present invention, by alternately supplying the compressed gas and the ultrapure water, the compressed gas and the ultrapure water are sent in a pulsed manner to the pipe, and not only generates turbulence but also vigorously agitates the water. However, the force can be applied locally and steeply in the pipe. As a result, a remarkable cleaning effect that cannot be obtained when only the compressed gas is supplied or when only the ultrapure water is supplied is obtained.
[0021]
In the present invention, the pressure of the supplied gas can be set higher than the pressure of the ultrapure water. By doing so, the ultrapure water looks like being pushed out by the gas. That is, the gas becomes a driving force for moving the ultrapure water through the pipe at a high speed.
[0022]
Further, at the contact portion between the gas and the ultrapure water, the gas and the water are mixed, and the gas-liquid mixed water generates bubbles. These bubbles strongly agitate the ultrapure water, thereby enhancing the effect of removing particles. Due to changes in pressure and flow rate, these bubbles are generated, disappear, and regenerated again, for example, by applying a large pressure to ultrapure water instantaneously when bubbles disappear, This will increase the speed at which the fine particles are peeled off.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be specifically described with reference to the drawings.
[0024]
FIG. 3 is a diagram showing a configuration of a main part of an embodiment of the ultrapure water production apparatus provided with the pipe cleaning device of the present invention. In FIG. 3, pure water produced in the primary pure water plant 1 is supplied to an ultrapure water production unit 3 via a pure water tank 2. In the ultrapure water production unit 3, ultrapure water is supplied to a pipe 5 from a UF (ultrafiltration membrane) 4 at the end after performing a UV oxidation treatment, an ion exchange treatment, and the like. After the installation of the ultrapure water production apparatus, in a state where the startup is completed and ultrapure water is supplied, the ultrapure water that has passed through the UF is used at the use point 6 via the pipe 5 and the remaining ultrapure water is supplied. The water is returned to the pure water tank 2.
[0025]
When the ultrapure water system is started up, fine particles adhere to the inside of the pipe 5, and thus the fine particles are removed by the pipe cleaning device 7. The removal of the attached fine particles by the pipe cleaning device 7 is performed as follows. First, the ultrapure water supplied to the pipe 5 from the ultrafilter 4 opens the valve 8, further opens the valve 9, closes the valve 10, and opens and closes the ultrapure water supply automatic opening and closing valve 11. Ultrapure water is intermittently fed into the pipe 5. Also, during the intermittent supply of ultrapure water by the ultrapure water automatic on-off valve 11, the compressed gas is sent from the compressed gas supply source 12 to the pipe 5 through the compressed gas supply automatic on-off valve 13. Reference numeral 16 indicates N ₂ purge.
[0026]
As described above, in the pipe cleaning according to the present invention, ultrapure water and compressed gas are alternately supplied to the pipe to perform cleaning. This cleaning is a so-called pulse cleaning in which cleaning is performed by a pulse of gas-liquid mixing. Here, the compressed gas supplied through the compressed gas supply automatic opening / closing valve 13 serves as a driving force to push out ultrapure water in a gas-liquid mixed state. In a state where the gas-liquid is mixed, the liquid has a white color due to fine bubbles and has detergency.
[0027]
Since the pipe cleaning apparatus 7 of the present invention is used only when the ultrapure water apparatus is started, it is desirable to provide the ultrapure water supply pipe 5 in a bypass form as shown in FIG.
[0028]
It is desirable that the compressed gas supply automatic on-off valve 13 can be opened and closed as quickly as possible. On the other hand, the ultrapure water supply automatic opening / closing valve 11 may be opened or closed later than the compressed gas supply automatic opening / closing valve 13. It is preferable to select and use these valves that have a high closed density and do not cause a backflow of water or gas.
[0029]
When turning on and off the UF filtered water by the ultrapure water automatic on-off valve 11, it is desirable to avoid damaging the UF membrane with a water hammer. Therefore, as shown in FIG. 1, a relief valve 14 and a relief line 15 can be provided in front of the ultrapure water supply automatic opening / closing valve 11. This is preferable because the ultrapure water that has passed through the UF membrane 4 can always be in a flowing state. In this case, even if the compressed gas flows backward, there is no problem since the gas is discharged under reduced pressure in this relief line.
[0030]
Further, in order to more reliably protect the UF membrane 4 from damage by the water hammer, water for cleaning from another supply source is used without supplying water for cleaning from the UF membrane 4. You can also.
[0031]
To obtain a higher cleaning effect than water, alkalis such as TMAH (tetramethylammonium hydroxide) and NaOH, alcohols such as isopropyl alcohol, a surfactant, and the like can be used in combination. When injecting these chemicals into the entire circle line including the pure water tank, the mixed bed type ion exchange resin (MB) and the like are bypassed.
[0032]
The compressed gas used is preferably nitrogen gas (N ₂ ), hydrogen gas (H ₂ ), or the like. In the case of hydrogen gas, a higher effect on the separation of fine particles can be obtained due to the high reducing power and the physical action of bubbles generated by the pulse of the compressed gas.
[0033]
Oxygen (O ₂ ) or air can be used as the compressed gas of the present invention. However, when used as an ultrapure water production device for semiconductor processing, dissolved oxygen in ultrapure water is not preferable. Is not used as compressed gas.
[0034]
On the other hand, when hydrogen (H ₂ ) is used as the compressed gas, the effect of removing the fine particles is increased by adding a high reducing power of the hydrogen gas to the physical action of the bubbles generated in a pulsed manner.
[0035]
The washing wastewater may be returned to the pure water tank, where gas-liquid separation may be performed. However, since large garbage and the like may be present at the beginning of water passage, it is preferable to drain the water at the beginning of water passage.
[0036]
In the present invention, the effect of cleaning is not always uniform, such that the effect is high in a pipe near a pipe cleaning apparatus, and the effect decreases as the distance increases. This point can be dealt with, for example, by setting the cleaning time to a location where the cleaning effect is low.
[0037]
If the length of the pipe is too long, in order to obtain a sufficient cleaning effect over the entire pipe, two or more injection points are provided, and ultrapure water and compressed gas are injected from each point to perform cleaning. You may do so.
[0038]
Further, in the cleaning of the pipe according to the present invention, it is possible to monitor that the pulse cleaning is successfully performed by confirming that the liquid is clouded by bubbles. Therefore, if it is difficult to check the inside of the pipe, for example, if the pipe is colored with C-PVC, a part of the pipe is made of transparent vinyl chloride resin so that the inside can be checked. It is preferable to keep it.
[0039]
FIG. 4A shows that the ultrapure water supply automatic on-off valve 11 is opened and the ultrapure water supply 20 is supplied to the pipe 5 in FIG. When the gas supply automatic opening / closing valve 13 is opened and the compressed gas 30 is supplied, the compressed gas 30 is pushed out in the gas-liquid mixed state 32, and further, the gas-liquid mixed state is transferred in (c). is there.
[0040]
The relationship between the flow of ultrapure water and the injection of the compressed gas can be variously set. For example, when water flows through the position of the inlet of the compressed gas about 3 to 10 times the diameter of the pipe, The time setting can be selected such that the compressed gas is introduced. The time setting in this case is performed while referring to the setting result in consideration of the pressure on the water supply side, the pipe diameter, and the like.
[0041]
The pressure of the compressed gas used here is preferably higher in order to obtain a cleaning effect, and is actually determined in consideration of the pressure resistance of the pipe. For example, in the case of C-PVC, the pressure may be, for example, about 5 kg / cm ² (4.9 × 10 ⁵ Pa). Note that the pressure resistance at this time is not a permanent pressure resistance, but a pressure resistance when a gas pressure is temporarily applied when the ultrapure water production apparatus starts up. When the pipe to be cleaned is long, it is preferable to set the gas pressure to a higher value. On the liquid sending side, a low pressure may be used. The liquid in the pipe is driven by the pressure of the compressed gas and moves.
[0042]
To thoroughly clean the entire pipe, open the valve of the compressed gas supply automatic opening / closing valve so that the gas-liquid mixed water reaches the end of the pipe to be cleaned, so that the compressed gas supply automatic opening / closing valve is closed. It is desirable to set the opening time. It is needless to say that the setting time is appropriately adjusted according to not only the length of the pipe but also the diameter of the pipe and the like, and it is preferable to set an appropriate setting.
[0043]
Further, when the ultrapure water supply automatic opening / closing valve and the compressed gas supply automatic opening / closing valve are alternately opened and the liquid and the gas are alternately fed into the pipe 4, the time from when one valve is closed to when the other valve is opened. It is better to provide a time during which both are closed, that is, a pause time. By providing this, backflow of gas or liquid can be prevented. The pause time may be appropriately set according to the characteristics of the automatic valve used.
[0044]
As a method of cleaning the pipe, there is a method of using a chemical such as TMAH for cleaning the pipe as described in JP-A-2002-52322, JP-A-2002-52324, and JP-A-2002-317413. However, when a chemical solution is used, there is a problem that the chemical solution must be discharged as a drainage solution, and it takes much time to remove the chemical solution after cleaning. In the present invention, such a chemical solution can be used as an auxiliary means, but is merely used as an auxiliary means in, for example, a cleaning step prior to the cleaning of the present invention. In the present invention, in order to obtain a high level of cleaning result, ultrapure water obtained through an ultrafilter is used as the cleaning liquid as a cleaning liquid, thereby preventing contamination or the like generated by the cleaning process from occurring. As a result, compared to the conventional pipe cleaning method, the cleaning efficiency is higher and a faster rise is obtained.
[0045]
In the practice of the present invention, as in the case of a normal ultrapure water apparatus, a structure that causes accumulation of gas and the like should not be adopted, and it is necessary to sufficiently perform air bleeding after cleaning. Needless to say.
[0046]
(Example)
FIG. 5 shows the configuration of this embodiment. 5, the same reference numerals as those in FIG. 3 are used for those corresponding to FIG. A 25 A clean PVC pipe was used as a test pipe, 10 elbows and 10 sockets were randomly installed as joints, the total length was about 5 m, and both ends were water faucet sockets, which were used as test pipes. Usually, the contaminated area is an installation point such as an elbow or a socket, so such a configuration having the contaminated area was selected. This test pipe was connected with a 1-inch PFA tube to form a test line shown in FIG.
[0047]
In the present embodiment, the ultrapure water that has passed through the ultrafilter and is supplied has already been passed for more than one year, so the number of particles is almost zero, and contamination of the particles is substantially present. That is not done. Incidentally, the UF film used here is OLT6036H manufactured by Asahi Kasei Corporation.
[0048]
As a test method, once a test pipe was installed, water was passed through the test pipe apparatus for one month or more, and the measured value of the particle counter 17 at this time was obtained and used as a blank value. The blank value was about 2 / mL on average. When the number of particles in the ultrapure water is small as described above, it is hindered by noise of the particle counter 17 itself used for measurement and contamination of the measuring instrument due to other factors. Since it was very difficult, such a blank value was measured and used as a reference for the measurement.
[0049]
Thereafter, the particle counter 17 used the particle counter 17 to determine the time during which ultrapure water was flown and the time when fine particles were removed. FIG. 6 shows the result of plotting the relationship with the concentration.
[0050]
In the pulse cleaning according to the present invention, the automatic valve for water is opened (the automatic valve for gas is closed) for 2 seconds ⇒ 0.2 seconds for rest ⇒ The automatic valve for gas is opened for 2 seconds (automatic valve for water is closed) ⇒ 0.2 seconds for rest , By repeating.
[0051]
As shown in FIG. 6, in this example, when ultrapure water was simply flowed through the test pipe, it took four days for the number of measured particles to reach the minimum value. On the other hand, when the pulse cleaning according to the present invention is performed, it can be seen that the number of particles measured by the particle counter reaches the minimum value in about one day.
[0052]
【The invention's effect】
As described above, according to the present invention, it is possible to quickly remove fine particles adhering to the piping of the ultrapure water device after construction, and also to the ultrapure water device of recent highly required specifications, The rise time after construction can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a state in which fine particles adhered to a pipe are separated and removed.
FIG. 2 illustrates the relationship between the logarithm of the number c of fine particles attached to a pipe and time t.
FIG. 3 is a diagram showing a configuration of a main part of an embodiment of an ultrapure water production apparatus provided with the pipe cleaning device of the present invention.
FIG. 4 schematically shows a state in which compressed gas is supplied after water is supplied to a pipe 5, and the compressed gas is pushed out in a gas-liquid mixed state, and this state is transferred.
FIG. 5 is a diagram illustrating a configuration of a tube cleaning in an embodiment.
FIG. 6 is a graph plotting the relationship between the time of flowing ultrapure water and the concentration of fine particles (black circles) when performing pulse cleaning for 2 hours, and performing no pulse cleaning (white circles) in the example of the present invention. FIG. 7 is a diagram showing the result of comparison with ().
[Explanation of symbols]
1 ... Primary pure water production plant, 2 ... Pure water tank, 3 ... Ultra pure water production unit, 4 ... UF (ultrafiltration membrane), 5 ... Piping, 6 ... Use point, 7 ... ... pipe cleaning device, 8, 9, 10 ... valve, 11 ... ultrapure water supply automatic open / close valve, 12 ... compressed gas supply source, 13 ... compressed gas supply automatic open / close valve, 14 ... relief valve , 15... Relief line, 16... N ₂ purge, 17... Particle counter, 20... Ultrapure water, 30... Compressed gas, 100.

Claims (2)

A compressed gas supply pipe for supplying a compressed gas to a pipe to be cleaned from a compressed gas supply source via a compressed gas supply automatic opening / closing valve;
An ultrapure water supply pipe for cleaning that supplies ultrapure water to the pipe to be cleaned through an ultrapure water automatic opening / closing valve that supplies ultrapure water that has been ultrafiltered,
An automatic opening and closing valve control system for alternately opening and closing the compressed gas supply automatic opening and closing valve and the ultrapure water automatic opening and closing valve at predetermined time intervals,
A pipe cleaning apparatus, characterized in that the compressed gas and the ultrapure water are alternately supplied to the pipe to be cleaned, whereby the deposits adhering to the inner wall of the pipe to be cleaned are removed. . A compressed gas supply pipe for supplying compressed gas to a pipe to be cleaned from a compressed gas supply source via a compressed gas supply automatic opening / closing valve, and an ultrapure water automatic opening / closing valve for supplying ultrafiltered ultrapure water. An ultra-pure water supply pipe for supplying ultra-pure water to a pipe to be cleaned, and an automatic on-off valve control for alternately opening and closing the compressed gas supply automatic on-off valve and the ultra-pure water automatic on-off valve at predetermined time intervals. A pipe cleaning apparatus that cleans and removes deposits adhering to the inner wall of the pipe to be cleaned by alternately supplying the compressed gas and the ultrapure water to the pipe to be cleaned. An ultrapure water production apparatus comprising:

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