U.S. patent application number 10/507539 was filed with the patent office on 2005-05-05 for continuous dissolving device, continuous dissolving method, and gas-dissolved water supply.
This patent application is currently assigned to KURITA WATER INDUSTRIES LTD. Invention is credited to Ida, Junichi, Morita, Hiroshi, Tsukamoto, Kazumi.
Application Number | 20050093182 10/507539 |
Document ID | / |
Family ID | 29544968 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050093182 |
Kind Code |
A1 |
Morita, Hiroshi ; et
al. |
May 5, 2005 |
Continuous dissolving device, continuous dissolving method, and
gas-dissolved water supply
Abstract
An apparatus for continuous dissolution comprising a dissolution
portion for dissolving a gas into a main stream liquid, which
comprises a flow meter measuring the flow rate of the main stream
liquid and outputting a signal of the value obtained by the
measurement and a mechanism for controlling the flow rate which
controls the amount of supply of the gas based on the input signal;
and a process for continuously dissolving a gas into the main
stream liquid, wherein the amount of the gas is controlled based on
the flow rate of the main stream liquid. Since a solution having a
constant concentration can be obtained with stability even when the
flow rate of the main stream liquid changes, cleaning water or
surface treatment water used for electronic materials which
particularly require a precisely clean surface can be supplied
without loss.
Inventors: |
Morita, Hiroshi; (Kanagawa,
JP) ; Ida, Junichi; (Ibaraki, JP) ; Tsukamoto,
Kazumi; (Miyagi, JP) |
Correspondence
Address: |
FRISHAUF, HOLTZ, GOODMAN & CHICK, PC
767 THIRD AVENUE
25TH FLOOR
NEW YORK
NY
10017-2023
US
|
Assignee: |
KURITA WATER INDUSTRIES LTD
4-7 NISHI-SHINJUKU 3 CHOME
SHINJUKU-KU, TOYKO
JP
160-8383
|
Family ID: |
29544968 |
Appl. No.: |
10/507539 |
Filed: |
September 13, 2004 |
PCT Filed: |
March 18, 2003 |
PCT NO: |
PCT/JP03/03289 |
Current U.S.
Class: |
261/26 |
Current CPC
Class: |
B01F 15/0479 20130101;
B01F 15/0412 20130101; B01F 15/00344 20130101; B01F 15/00136
20130101; B01F 3/0446 20130101; B01F 2215/0036 20130101; B01F
2215/0096 20130101; B01F 15/00123 20130101; B01F 3/04985 20130101;
C02F 2103/346 20130101; B01F 2201/01 20130101 |
Class at
Publication: |
261/026 |
International
Class: |
B01D 047/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2002 |
JP |
2002-142032 |
Claims
1. An apparatus for continuous dissolution which comprises a
dissolution portion for dissolving a gas into a main stream liquid,
the apparatus further comprising a flow meter which measures a flow
rate of the main stream liquid and outputs a signal of a value
obtained by the measurement, a mechanism for controlling a flow
rate which controls an amount of supply of the gas based on the
signal input from the flow meter and an apparatus for degassing the
main stream liquid which is disposed at a position at an upstream
of the dissolution portion for dissolving a gas.
2. An apparatus for continuous dissolution according to claim 1,
wherein the main stream liquid is pure water or ultra-pure
water.
3. An apparatus for continuous dissolution according to claim 2,
which comprises a means for injecting an other liquid into the main
stream liquid and controls an amount of addition of the other
liquid based on the signal.
4. A process for continuous dissolution which comprises
continuously dissolving a gas or a gas and an other liquid into a
main stream liquid, wherein the main stream liquid is degassed
before the gas is dissolved and an amount of supply of the gas or
amounts of supply of the gas and the other liquid are controlled
based on a flow rate of the main stream liquid before the degassing
or after the degassing.
5. An apparatus for supplying water containing a dissolved gas
which comprises: a portion for producing the water containing a
dissolved gas comprising: an apparatus for dissolving a gas which
comprises a flow meter measuring a flow rate of pure water or
ultra-pure water and outputting a signal of a value obtained by the
measurement and a mechanism for controlling a flow rate which
controls an amount of a gas to be dissolved into the pure water or
the ultra-pure water based on the signal input from the flow meter,
and a means for adjusting an amount of water which adjusts an
amount of the pure water or the ultra-pure water supplied to the
apparatus for dissolving a gas, and a portion for supplying the
water containing a dissolved gas comprising: a water tank which
receives the water containing a dissolved gas in an excess amount
which is not used at a point of use, a piping system through which
the water containing a dissolved gas flows from the water tank
towards the point of use and the water containing a dissolved gas
in an excess amount returns to the water tank, and a piping for
supplying the water containing a dissolved gas which supplies the
water containing a dissolved gas obtained in the portion for
producing the water containing a dissolved gas to the water tank;
and controls the means for adjusting an amount of water based on a
water level in the water tank.
6. An apparatus for supplying water containing a dissolved gas
according to claim 5, wherein the water tank is a water tank of a
sealed type equipped with a portion for supplying a sealing gas and
the sealing gas is a same gas as the gas dissolved in the water
containing a dissolved gas.
Description
TECHNICAL FIELD
[0001] The present invention relates to an apparatus for continuous
dissolution and a process for continuous dissolution. More
particularly, the present invention relates to an apparatus for
continuous dissolution and a process for continuous dissolution
which can supply, without loss, cleaning water or surface treatment
water used for electronic materials which particularly requires a
precisely clean surface and to an apparatus for supplying water for
cleaning containing a dissolved gas which is equipped with the
apparatus for continuous dissolution.
BACKGROUND ART
[0002] In the wet cleaning process for electronic materials, the
so-called functional water for cleaning which is prepared by
dissolving a minute amount of a specific gas or a specific chemical
into ultra-pure water has been recognized to be useful and is being
used more widely. Apparatus using a module having a built-in
gas-permeating membrane in the portion for dissolution or in the
portion for degassing and dissolution are widely used. These
apparatuses are useful since the entire amount of the gas to be
supplied can be dissolved as long as the concentration does not
exceed the concentration of saturation when the main stream liquid
is preliminarily treated by degassing.
[0003] However, an apparatus for dissolving a specific gas such as
hydrogen or a specific gas and a specific chemical can provide a
functional water containing the gas or the chemical in the
prescribed concentration only when the main stream liquid is
supplied at a constant flow rate. When the amount of supply of the
main stream liquid changes due to some outside factors or due to
saving of water, a problem arises in the practical operation that
the concentration of the gas or the chemical in the produced
functional water fluctuates.
[0004] During the period of time when the functional water is not
used, occasionally, a small amount of the main stream liquid alone
is continuously supplied without supplying the specific gas. This
causes another problem in the practical operation in that, at the
start of the period of time when the functional water is used, it
takes a considerable time until the concentration of the dissolved
gas reaches the prescribed value and is stabilized at this value
after the start of the supply of the specific gas.
[0005] To stabilize the concentration of the dissolved gas, a feed
back mechanism in which an output signal is received from the
portion for measurement of the concentration placed at the down
stream side of the dissolution apparatus and the amount of supply
of the gas to be dissolved is controlled, is widely used. However,
the desirable results cannot be obtained even when this mechanism
is applied to preparation of the functional water. The reason is
that a functional water having an undesired concentration is
prepared at least during the period of time lag by the feed back
and the hunting phenomenon in the concentration cannot be prevented
even when the so-called PID control is conducted.
[0006] Therefore, an apparatus for continuous dissolution and a
process for continuous dissolution which can maintain the quality
of the functional water, i.e., the condition in which the
concentrations of the gas and the chemical can be kept stable, even
when the flow rate of the main stream water changes, has been
desired.
[0007] The present invention has an object of providing an
apparatus for continuous dissolution and a process for continuous
dissolution which provides a solution having a constant
concentration with stability even when the flow rate of the main
stream liquid changes and can supply cleaning water or surface
treatment water used for electronic materials which particularly
requires a precisely clean surface without loss.
[0008] The present invention has another object of providing an
apparatus for supplying water containing a dissolved gas which
utilizes the apparatus for continuous dissolution providing a
solution having a constant concentration with stability.
DISCLOSURE OF THE INVENTION
[0009] As the result of the intensive studies by the present
inventors to overcome the above problems, it was found that a
functional water having a constant concentration of a gas and a
chemical could be produced with stability, even when the flow rate
of the main stream liquid changed, by disposing a flow meter which
measured the flow rate of the main stream liquid and output the
signal of the value obtained by the measurement and a mechanism for
controlling the flow rate which controlled the amount of supply of
the gas or the amounts of supply of the gas and the other chemical
based on the signal input from the flow meter. The present
invention has been completed based on the above knowledge.
[0010] The present invention provides:
[0011] (1) An apparatus for continuous dissolution which comprises
a dissolution portion for dissolving a gas into a main stream
liquid, the apparatus further comprising a flow meter which
measures a flow rate of the main stream liquid and outputs a signal
of a value obtained by the measurement, a mechanism for controlling
a flow rate which controls an amount of supply of the gas based on
the signal input from the flow meter and an apparatus for degassing
the main stream liquid which is disposed at a position at an
upstream of the dissolution portion for dissolving a gas;
[0012] (2) An apparatus for continuous dissolution as described in
(1), wherein the main stream liquid is pure water or ultra-pure
water;
[0013] (3) An apparatus for continuous dissolution as described in
(2), which comprises a means for injecting an other liquid into the
main stream liquid and controls an amount of addition of the other
liquid based on the signal;
[0014] (4) A process for continuous dissolution which comprises
continuously dissolving a gas or a gas and an other liquid into a
main stream liquid, wherein the main stream liquid is degassed
before the gas is dissolved and an amount of supply of the gas or
amounts of supply of the gas and the other liquid are controlled
based on a flow rate of the main stream liquid before the degassing
or after the degassing;
[0015] (5) An apparatus for supplying water containing a dissolved
gas which comprises:
[0016] a portion for producing the water containing a dissolved gas
comprising:
[0017] an apparatus for dissolving a gas which comprises a flow
meter measuring a flow rate of pure water or ultra-pure water and
outputting a signal of a value obtained by the measurement and a
mechanism for controlling a flow rate which controls an amount of a
gas to be dissolved into the pure water or the ultra-pure water
based on the signal input from the flow meter, and
[0018] a means for adjusting an amount of water which adjusts an
amount of the pure water or the ultra-pure water supplied to the
apparatus for dissolving a gas, and
[0019] a portion for supplying the water containing a dissolved gas
comprising:
[0020] a water tank which receives the water containing a dissolved
gas in an excess amount which is not used at a point of use,
[0021] a piping system through which the water containing a
dissolved gas flows from the water tank towards the point of use
and the water containing a dissolved gas in an excess amount
returns to the water tank, and
[0022] a piping for supplying the water containing a dissolved gas
which supplies the water containing a dissolved gas obtained in the
portion for producing the water containing a dissolved gas to the
water tank; and
[0023] controls the means for adjusting an amount of water based on
a water level in the water tank; and
[0024] (6) An apparatus for supplying water containing a dissolved
gas described in (5), wherein the water tank is a water tank of a
sealed type equipped with a portion for supplying a sealing gas and
the sealing gas is a same gas as the gas dissolved in the water
containing a dissolved gas.
[0025] As the preferable embodiments, the present invention further
provides:
[0026] (7) An apparatus for continuous dissolution as described in
(1), wherein the flow rate of the gas is controlled in accordance
with the proportional control or the PID control;
[0027] (8) An apparatus for continuous dissolution as described in
(1), wherein the dissolution portion comprises a module comprising
a built-in gas-permeating membrane;
[0028] (9) An apparatus for continuous dissolution as described in
(1), wherein the apparatus for degassing comprises a module
comprising a built-in gas-permeating membrane;
[0029] (10) An apparatus for continuous dissolution as described in
(1), which comprises a mechanism for controlling the flow rate
comprising a mass flow controller;
[0030] (11) An apparatus for continuous dissolution as described in
(1), wherein the gas is hydrogen, oxygen, nitrogen, helium, argon,
ozone, ammonia, carbon dioxide or a mixture of these gases;
[0031] (12) An apparatus for continuous dissolution as described in
(3), wherein a piping for transporting the main stream liquid has a
portion for adding the other liquid which is disposed at a stage
before a means for mixing.
[0032] (13) An apparatus for continuous dissolution as described in
(3), which comprises a mechanism for controlling the flow rate
comprising a pump for injecting a chemical which can change the
flow rate.
[0033] (14) An apparatus for continuous dissolution as described in
(3), wherein the other liquid is ammonia, sodium hydroxide,
potassium hydroxide, tetramethylammonium hydroxide, hydrochloric
acid, sulfuric acid, nitric acid, hydrofluoric acid, phosphoric
acid, acetic acid, oxalic acid, a solution containing hydrogen
peroxide or a mixture of these liquids; and
[0034] (15) An apparatus for continuous dissolution as described in
(4), wherein the flow rate of the gas is controlled in accordance
with the proportional control or the PID control
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 shows a process flow chart of an embodiment of the
apparatus of the present invention.
[0036] FIG. 2 shows a process flow chart of another embodiment of
the apparatus of the present invention for supplying water
containing a dissolved gas.
[0037] In the Figures, reference number 6 means an injection
portion, reference number 7 means a membrane apparatus for
degassing, reference number 8 means a flow meter, reference number
9 means a mass flow controller, reference number 10 means a
hydrogen gas generator, reference number 11 means a membrane module
for dissolution of a gas, reference number 13 means a tank for
aqueous ammonia, reference number 14 means a chemical-injection
pump, reference number 15 means an inline mixer, reference number
16 means a concentration monitor for dissolved hydrogen, reference
number 17 means a pH meter, reference number 19 means a valve,
reference number 21 means a water tank, reference number 22 and
reference number 22' mean pipings, reference number 25 means a
water level meter, reference number 26 means a piping for supplying
a sealing gas, reference number 28 means a piping for supplying
gas-dissolved water and reference number 30 means a cover.
THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION
[0038] The apparatus for continuous dissolution of the present
invention comprises a dissolution portion for dissolving a gas into
a main stream liquid, wherein the apparatus further comprises a
flow meter which measures the flow rate of the main stream liquid
and outputs a signal of a value obtained by the measurement and a
mechanism for controlling the flow rate which controls the amount
of supply of the gas based on the signal input from the flow meter.
The process for continuous dissolution of the present invention
comprises continuously dissolving a gas or a gas and an other
liquid into a main stream liquid, wherein the amount of the gas or
the amounts of the gas and the other liquid are controlled based on
the flow rate of the main stream liquid.
[0039] The apparatus and the process of the present invention can
be advantageously applied to the production of the functional water
which is an aqueous solution dissolving a gas or a combination of a
gas and an alkali or an acid into pure water or ultra-pure water as
the main stream liquid. In the present invention, pure water means
water having a high purity which can be regarded to be almost the
same as pure water from which impurities have been removed as much
as possible. Ultra-pure water means water having an extremely high
purity from which substances suspended or dissolved in water have
been removed extremely so that the concentration of the dissolved
substances is at the level of 1 .mu.g/liter. The aqueous solution
obtained by dissolving a gas into the pure water or the ultra-pure
water or the functional water obtained by dissolving a gas and an
aqueous solution comprising a dissolved alkali or acid into the
pure water or the ultra-pure water can be advantageously used as
cleaning water and surface treatment water for electronic materials
such as substrates of semiconductors, substrates of liquid crystal
displays, substrates of photomasks and substrates of hard
disks.
[0040] In the present invention, it is preferable that the amount
of supply of the gas is controlled in accordance with the
proportional control or the PID control. By the proportional
control or the PID control of the amount of supply of the gas in
accordance with the change in the flow rate of the main stream
liquid, the functional water into which the gas is dissolved in a
constant concentration can be constantly produced.
[0041] The flow meter used for measuring the flow rate of the main
stream liquid in the present invention is not particularly limited.
Examples of the flow meter include flow meters of the restricted
flow type such as the orifice flow meter and the Venturi flow
meter; flow meters of the liquid resistance type such as the
resistance flow meter, the flow meter of the area type and the flow
meter of the laminar flow type; flow meters of the liquid vibration
type such as the Karman's vortex flow meter, the swirl flow meter
and the fluidic flow meter; flow meters of the volume type; flow
meters of the blade wheel type; flow meters of the water blow type;
flow meters of the electromagnetic type; and flow meters of the
ultrasonic type. Among these flow meters, Karman's vortex flow
meter and the flow meter of the ultrasonic type having no sliding
portions are preferable since contamination of water can be
prevented. In the present invention, the flow rate of the main
stream liquid is measured by the above flow meter and the amount of
supply of the gas or the amounts of supply of the gas and the other
liquid are controlled based on the output signal of the value
obtained by the measurement.
[0042] In the present invention, when the gas is dissolved into the
main stream liquid (the pure water or the ultra-pure water), it is
preferable that the supplied gas is completely dissolved into the
supplied pure water or ultra-pure water. To completely dissolve the
supplied gas into the pure water or the ultra-pure water, it is
necessary that the main stream liquid is degassed in advance. By
degassing the main stream liquid in advance, ideally, various gases
dissolved in the main stream liquid (the pure water or the
ultra-pure water) are removed and the gas dissolution capacity for
the desired gas increases. In the main stream liquid (the pure
water or the ultra-pure water) in the above condition, it is
possible that the supplied gas is completely dissolved when the gas
dissolution capacity is greater than the amount of the supplied
desired gas. On the contrary, when various gases are left remaining
in the main stream liquid (the pure water or the ultra-pure water)
before the desired gas is dissolved, the capacity to dissolve a gas
into the main stream liquid (the pure water or the ultra-pure
water) is insufficient and the desired concentration cannot be
achieved. In the latter condition, there is the possibility that
the concentration of the gas dissolved into the main stream liquid
(the pure water or the ultra-pure water) cannot be adjusted at the
desired concentration in accordance with the change in the flow
rate of the main stream liquid (the pure water or the ultra-pure
water). In particular, when a gas having a small solubility such as
hydrogen is dissolved into the main stream liquid (the pure water
or the ultra-pure water), it is necessary that the main stream
liquid (the pure water or the ultra-pure water) be degassed in
advance to keep the concentration constant even when the flow rate
of the main stream liquid (the pure water or the ultra-pure water)
changes. When the main stream liquid (the pure water or the
ultra-pure water) is degassed in advance before the gas is
dissolved, the signal of the meter measuring the flow rate of the
main stream liquid (the pure water or the ultra-pure water) is
input to rapidly control the amount of the supplied gas and then
the gas in the supplied amount is completely dissolved so that the
concentration can be set at the desired value. Even when the flow
rate of the main stream liquid (the pure water or the ultra-pure
water) changes, the concentration can be recovered rapidly to the
desired value due to the above mechanism.
[0043] The process for degassing the main stream liquid (the pure
water or the ultra-pure water) is not particularly limited. It is
preferable that the gas in an amount smaller than the solubility at
saturation is supplied after the pure water or the ultra-pure water
is treated by a membrane apparatus for degassing comprising a
module having a built-in gas-permeating membrane, and thus the
capacity to dissolve a gas into water is increased by removing
dissolved gases. The dissolution portion for dissolving the gas is
not particularly limited. It is preferable that the dissolution
portion comprises a module having a built-in gas-permeating
membrane. Since the main stream liquid and the supplied gas flowing
into the dissolution portion each stagnates at the liquid phase and
the gas phase of the dissolution portion for a prescribed period of
time, the module exhibits the buffering function offsetting the
change in the amount of supply of the gas and a little time lag and
thus the functional water having little fluctuation of the
concentration of the dissolved gas can be produced with stability.
The gas to be dissolved is not particularly limited. Example of the
gas includes hydrogen, oxygen, nitrogen, helium, argon, ozone,
ammonia and carbon dioxide. With the functional water containing
hydrogen, oxygen, helium or argon dissolved into the pure water or
the ultra-pure water, fine particles attached to the surface of
electronic materials can be removed. With the functional water
prepared by dissolving ozone into the pure water or the ultra-pure
water, organic substances and metal substrates attached to the
surface of electronic materials can be removed. With the functional
water prepared by dissolving carbon dioxide into the pure water or
the ultra-pure water, build-up of static electricity can be
prevented.
[0044] In the present invention, the position of the measurement of
the flow rate of the main stream liquid is not particularly limited
as long as the position is before the dissolution portion where the
gas is dissolved. The flow rate of the main stream liquid may be
measured before or after the portion for degassing.
[0045] In the present invention, when the injection of another
liquid into the pure water or the ultra-pure water is conducted in
combination with the dissolution of the gas, a portion for
injection where the other liquid is injected is disposed at the
piping for transporting the main stream liquid. The portion for
injection is connected to the tank for the other liquid via a
chemical-injection pump. Since the liquid supplied as the other
liquid is, in many cases, an aqueous solution, the other liquid is
homogeneously mixed with the pure water or the ultra-pure water of
the main stream liquid relatively easily. The flow rate of the
other liquid can be controlled by the pulse control of the
chemical-injection pump. In the same manner as that conducted in
the dissolution of the gas, the flow rate of the main stream liquid
is measured by a flow meter. The value obtained by the measurement
is input into a mechanism for controlling the flow rate built in
the chemical-injection pump and the amount of injection of the
liquid into the main stream liquid is controlled.
[0046] In the present invention, the other liquid dissolved into
the main stream liquid is not particularly limited. Examples of the
other liquid include aqueous solutions of alkalis such as ammonia,
sodium hydroxide, potassium hydroxide and tetramethylammonium
hydroxide; aqueous solutions of acids such as hydrochloric acid,
sulfuric acid, nitric acid, hydrofluoric acid, phosphoric acid,
acetic acid and oxalic acids; and an aqueous solution of hydrogen
peroxide. A mixture of these liquids such as a mixed solution of
ammonia and an aqueous solution of hydrogen peroxide and a mixed
solution of ammonia and hydrofluoric acid can be used.
[0047] In the present invention, a combination of the gas and the
other liquid may be dissolved into the main stream liquid. The
amounts of supply of the gas and the other liquid into the main
stream liquid can be controlled in the same manner as that for the
single supply of the gas. As the gas and the other liquid to be
dissolved in combination, a suitable combination of the gasses and
the other liquids exemplified above for single dissolution can be
used. For example, when hydrogen and ammonia are dissolved into the
ultra-pure water in combination, the effect of the functional water
to remove fine particles can be enhanced.
[0048] The present invention is very useful since the functional
water is automatically produced in accordance with the change in
the required amount of water. For example, when the functional
water is supplied to four cleaning machines each requiring water in
an amount of 5 liters/minute, the required amount of water changes
between 0 liter/minute to 20 liters/minute depending on the
condition of the cleaning machines (the functional water is used or
not used). In a conventional apparatus, the supply of the
functional water is continued at the constant condition of 20
liters/minute and the functional water in the excess amount is
discharged from the cleaning machines or from the apparatus for
producing the functional water. In contrast, in the present
invention, the functional water having the constant concentration
can be produced in accordance with the required amount of water and
the discharge of the excess amount of the functional water can be
avoided.
[0049] It is also widely conducted that, during the period of time
when the functional water is not required temporarily, the flow of
the functional water is continued under the ordinary condition so
that deterioration in the quality of the functional water remaining
in the apparatus due to growth of bacteria is prevented or the
limited flow is conducted, i.e., the flow of the pure water or the
ultra-pure water alone in a small amount is continued while the
supply of the gas and the other liquid is stopped. When the
ordinary use of the functional water is resumed after the limited
flow, the flow rate of the water is increased and the supply of the
gas and the chemical is resumed. At this time, in the conventional
process, it takes several minutes to several ten-odd minutes before
the prescribed concentration is achieved and the cleaning cannot be
conducted during this transition period. In accordance with the
present invention, the functional water having the prescribed
concentration can be obtained immediately after resuming the
cleaning by continuing the supply of the gas and the chemical in an
amount in accordance with the flow rate of the water during the
limited flow.
[0050] As described above, the water containing a dissolved gas in
the prescribed concentration (the functional water) which is
obtained by the apparatus of the present invention for continuous
dissolution of a gas is supplied via pipings to and used at one or
more points of use where the water is used as cleaning water and
surface treatment water for electronic materials. The functional
water may be transferred directly from the apparatus for
dissolution to the points of use or may be temporarily stored into
a water tank and, thereafter, supplied to the use points via a
supply piping of the circulation type formed between the water tank
and the points of use. When the functional water is not used or is
used in a small amount, the functional water supplied to the points
of use is not discharged from the piping as unused water in an
excess amount but returns to the water tank via the piping of the
circulation type. Since the recycled functional water containing
the dissolved gas can be reused with little change in the
concentration of the dissolved gas, it is sufficient that the fresh
functional water is supplied into the water tank only in the amount
of a decrease which is shown by the lowering of the water level
from the prescribed position. A meter for measuring the water level
is disposed at the water tank and the construction is formed so
that the freshly prepared functional water is supplied into the
water tank in an amount in accordance with the water level. Since
the concentration of the dissolved gas in the functional water
produced by the apparatus for continuous dissolution of the present
invention can be controlled at the desired value, the concentration
of the gas in the functional water to be freshly supplied to the
water tank can be adjusted at the same value as the concentration
of the dissolved gas in the unused functional water in the water
tank (or the piping of circulation). Therefore, the concentration
of the added component in the functional water supplied to the
points of use can be kept constant and the cleaning of electronic
materials can be conducted with stability.
[0051] FIG. 1 shows a process flow chart of an embodiment of the
apparatus of the present invention. In this embodiment, a
functional water to be used for removing fine particles is produced
by dissolving hydrogen and ammonia into the ultra-pure water.
Dissolved gases are removed from the ultra-pure water by a membrane
apparatus for degassing 7 and, as a result, the capacity to
dissolve a gas is expanded for dissolving hydrogen. The flow rate
of the degassed ultra-pure water is measured by a flow meter 8 and
the signal is sent to a mass flow controller 9 and a
chemical-injection pump 14, having the function of controlling the
flow rate. The amount of supply of hydrogen gas from a hydrogen
source such as a hydrogen gas generator 10 to a membrane module for
dissolution of a gas 11 is controlled by the mass flow controller 9
in accordance with the flow rate of the ultra-pure water and then a
prescribed amount of hydrogen gas is supplied to and dissolved into
the ultra-pure water. In accordance with the flow rate of the
ultra-pure water, aqueous ammonia in a prescribed amount is added
at an injection portion 6 by the chemical-injection pump 14. The
injected aqueous ammonia is homogeneously mixed by an inline mixer
15 and a functional water containing dissolved hydrogen and ammonia
is produced. The injection portion 6 may be disposed at a position
at the upstream of the membrane module for dissolution of a gas 11
or the membrane apparatus for degassing 7. In this case, the
membrane module for dissolution of a gas 11 or the membrane
apparatus for degassing 7 may be used as a means for mixing in
place of the inline mixer 15. After the concentration of hydrogen
dissolved in the functional water is measured by a concentration
monitor for dissolved hydrogen 16 and pH is measured by a pH meter
17 or the like, the functional water is transferred to some points
of use. The concentration monitor for dissolved hydrogen 16 and the
pH meter 17 or the like are used for confirming that the
concentration of hydrogen and the pH are set at the desired
values.
[0052] FIG. 2 shows a process flow chart of an embodiment of the
apparatus for supplying gas-dissolved water (a functional water)
utilizing the apparatus for continuous dissolution of the present
invention. The apparatus for supplying gas-dissolved water is
comprised of a functional water production portion A for producing
a functional water and a functional water supply portion B for
supplying a functional water. The functional water production
portion A has the same construction as that of the apparatus for
dissolution shown in FIG. 1. To a piping for supplying the
ultra-pure water 18 to the membrane apparatus for degassing 7, a
valve 19 is attached as the means for adjusting the flow rate of
water. The flow rate can be adjusted by the valve 19 between zero
to the desired flow rate by adjusting the degree of opening of the
valve. The valve can control the starting and the stopping of the
supply of the ultra-pure water and also the flow rate of the
ultra-pure water. As the means for adjusting the flow rate of
water, a combination of a valve and a pump may be used in place of
the valve.
[0053] In the functional water supply portion B, a water tank 21
and a circulating piping system comprising a piping 22 from the
water tank 21 towards points of use and a piping 22' returning from
the points of use to the water tank 21 are disposed. In the piping
22, a pump 23 is disposed as the driving source for supplying the
functional water through the circulating piping system and a filter
24 is disposed at a position at the downstream of the pump. The
water tank 21 is tightly closed with a cover 30 so that the water
tank is shielded from the atmosphere. To the gas phase portion of
the water tank, a pipe for supplying a sealing gas 26 is connected
so that the inside of the water tank can be sealed and a portion
for discharging a gas is formed so that the pressure inside the
water tank can be kept constant although this is not shown in the
Figure. As the gas used for the sealing, the same gas as that
contained in the gas-dissolved water or an inert gas such as
nitrogen can be used. In the former case, when a plurality of gases
are dissolved into the pure water or the ultra-pure water, the
change in the concentrations of the dissolved gases in the water
tank can be suppressed by using a mixed gas having a composition
such that the pressure of each component gas is the same as the
partial pressures of the corresponding dissolved component gas.
Therefore, it is desirable that a mixed gas is used. To the water
tank, a piping for supplying gas-dissolved water 28 through which
the functional water obtained in the functional water production
portion A is supplied is connected. To the water tank 21, a water
level meter 25 is disposed. The signal from the water level meter
is transferred to a valve 19 of the functional water production
portion A and the valve is opened, closed or used by adjustment of
the degree of opening. It is preferable that the volume of the gas
phase portion within the water tank 21 is as small as possible so
that the change in the concentration in the gas-dissolved water is
suppressed. For this purpose, it is preferable that the water level
meter 25 can detect the surface of the gas-dissolved water at a
position close to the lower face of the cover 30. By keeping the
volume of the gas phase portion small, the partial pressure of the
gas dissolved into the aqueous phase and the partial pressure of
the gas in the gas phase portion can be brought into the
equilibrium in a short time and the change in the concentration is
kept small.
[0054] In the apparatus for supplying gas-dissolved water shown in
FIG. 2, the functional water in the water tank 21 is transferred
from the piping 22 to some points of use by the pump 23 and the
functional water in an excess amount and not used at the points of
use returns to the water tank 21 via the piping 22' and circulated
through the circulating piping system. Since there is the
possibility that fine particles are formed from sliding portions of
the pump 23 during the circulation and contained in the functional
water, the fine particles are removed when the functional water
passes through the filter 24. As the filter 24, membrane filters
such as a micro filter or an ultra filter are suitable. When the
functional water is consumed at the points of use, the water level
in the water tank 21 is lowered. When the water level reaches the
lower limit, the signal of the water level meter is transferred to
the valve 19. The supply of the ultra-pure water to the functional
water production portion A starts and the flow rate of the supplied
water is controlled by adjusting the degree of opening of the
valve. In the functional water production portion A, as shown in
the descriptions for FIG. 1, the flow rate of the supplied
ultra-pure water is measured by the flow meter 8 and the gas (for
example, hydrogen) to be dissolved into the ultra-pure water is
supplied to the membrane module for dissolution of a gas 11 under
control of the flow rate in accordance with the value obtained by
the measurement. Thus, the functional water having the same
concentration as that of the gas dissolved in the functional water
in the water tank is produced. In the same manner, the prescribed
amount of the chemical (for example, aqueous ammonia) in accordance
with the flow rate of the ultra-pure water is added to the
functional water. The produced functional water is transferred to
the water tank 21, temporarily stored in the water tank together
with the unused functional water in the excess amount and delivered
for use at the points of use via the circulation water system. When
the freshly produced functional water is supplied to the water tank
and the water level of the water tank reaches the upper limit, the
valve 19 is closed by the signal of the water level meter. The
supply of the ultra-pure water is stopped and the function of gas
dissolution in the functional water producing portion A is
temporarily stopped. Alternatively, even when the water level 25
detects the upper limit, the gas-dissolved water in a small amount
may be continuously passed so that the cleanliness of the
functional water production portion A is maintained. In this case,
a mechanism for overflow which is not shown in the Figure is
disposed at the water tank 21 and the excess amount of the
gas-dissolved water is discharged from the water tank 21 so that
the amount of the stored gas-dissolved water does not exceed the
capacity of the water tank 21. Since the concentration of the
dissolved gas in the produced functional water can be adjusted at
the desired value even when the flow rate of the ultra-pure water
changes, the concentration of the dissolved gas can be kept at the
same value as that of the unused functional water in either case
where the water level in the water tank is recovered rapidly or
slowly to the upper limit and, as a result, the functional water
having a constant concentration can be supplied to the points of
use. Therefore, when the apparatus of the present invention for
supplying gas-dissolved water is used, the functional water in an
excess amount at the points of use can be collected to the water
tank and reused in combination with the freshly supplied functional
water. In conventional processes, since it is difficult that the
functional water having a constant concentration is obtained when
the flow rate of the supplied water changes and it is also
difficult that the concentration of the freshly supplied functional
water is adjusted at the same value as that of the functional water
in the excess amount, the functional water in the excess amount is
discharged to the outside or collected as the ultra-pure water
after the functional water in the excess amount is treated by
degassing. In contrast, the present invention enables remarkably
more efficient recycling.
[0055] It is desirable that the water level in the water tank is
kept at a high position even when the used amount of water changes
since the relative amounts of the gases in the gas phase and the
liquid phase are stabilized and the change in the concentration of
the gas in the water can be suppressed. It is preferable that the
gas phase at the upper portion of the water tank is sealed with a
sealing gas and the relative amounts of the gases in the gas phase
are kept constant.
[0056] It is preferable that a heat exchanger is disposed at a
suitable position in the circulating piping system such as a
position between the pump 23 and the filter 24 so that the
elevation of the temperature of the water due to the heat of the
pump can be suppressed and the temperature of the functional water
can be kept constant.
EXAMPLES
[0057] The present invention will be described more specifically
with reference to examples in the following. However, the present
invention is not limited to the examples.
Example 1
[0058] Hydrogen-dissolved water was produced by using the apparatus
for producing a functional cleaning water shown in FIG. 1. The used
ultra-pure water contained 10 to 18 ppm of dissolved nitrogen gas
and 0.01 to 2 ppm of dissolved oxygen gas. The ultra-pure water was
passed through a membrane apparatus for degassing and degassed
until the concentration of the dissolved nitrogen gas was 1.5 ppm
or smaller and the concentration of the dissolved oxygen gas was
0.5 ppm or smaller. The degassed ultra-pure water was supplied to
the dissolution portion. The signal of the flow rate of the
ultra-pure water was output from the Karman's vortex flow meter and
the amount of supply of hydrogen gas was controlled proportionally
to the flow rate of the ultra-pure water by the mass flow
controller. Hydrogen was dissolved into the ultra-pure water at the
dissolution portion having a module having a built-in
gas-permeating membrane and hydrogen-dissolved water was
produced.
[0059] The production of the hydrogen-dissolved water started under
the condition of a flow rate of the ultra-pure water of 20
liters/minute and an amount of supply of hydrogen of 260 ml/minute.
After the start of the production, the flow rate of the ultra-pure
water was changed to 10 liters/minute after 30 minutes, 15
liters/minute after 60 minutes, 20 liters/minute after 80 minutes,
25 liters/minute after 110 minutes, 20 liters/minute after 120
minutes, 2 liters/minute after 150 minutes and 20 liters/minute
after 180 minutes. The production of the hydrogen-dissolved water
was conducted for the total time of 200 minutes.
[0060] The flow rate of the ultra-pure water, the amount of supply
of hydrogen and the concentration of hydrogen in the
hydrogen-dissolved water which were obtained by the measurements
are shown in Table 1.
1TABLE 1 Flow rate of Amount of Concn. of ultra-pure supply of
dissolved Time water hydrogen hydrogen (min) (liter/min) (ml/min)
(mg/min) Note 1 19.45 251 0.08 5 19.73 256 0.80 10 19.24 257 1.01
14 19.64 257 1.11 17 19.59 257 1.12 20 19.75 256 1.15 25 19.53 256
1.12 30 10.87 135 1.11 flow rate of ultra-pure water was changed 35
10.64 132 1.12 40 10.97 136 1.11 50 10.78 138 1.12 60 15.18 192
1.12 flow rate of ultra-pure water was changed 65 15.27 200 1.10 70
15.35 201 1.15 80 19.65 258 1.15 flow rate of ultra-pure water was
changed 90 19.88 256 1.10 100 19.66 256 1.15 110 24.21 323 1.14
flow rate of ultra-pure water was changed 113 24.08 325 1.15 117
24.35 327 1.15 120 19.98 260 1.14 flow rate of ultra-pure water was
changed 130 19.72 257 1.13 140 19.83 258 1.12 150 2.05 26 1.14 flow
rate of ultra-pure water was changed 160 2.04 26 1.15 170 2.10 26
1.13 180 19.94 259 1.11 flow rate of ultra-pure water was changed
182 20.09 258 1.11 185 20.10 260 1.13 190 20.00 259 1.14 200 19.97
257 1.13
[0061] As shown in Table 1, when the production of the
hydrogen-dissolved water was started under the condition of the
flow rate of the ultra-pure water of about 20 liters/minute, the
concentration of the dissolved hydrogen exceeded 1.00 mg/liter
after 10 minutes and reached 1.11 mg/liter after 14 minutes and the
condition which can be used as the functional water for cleaning
electronic members could be achieved. After the start of the
production, the amount of the supply of hydrogen was automatically
controlled in response to the changes in the flow rate of the
ultra-pure water after 30, 60, 80, 110, 120, 150 and 180 minutes
and the concentration of hydrogen in the produced
hydrogen-dissolved water was always kept stable within the range of
1.10 to 1.15 mg/liter.
[0062] By using the apparatus and the process of the present
invention, the formation of hydrogen-dissolved water in a low
concentration was prevented after the start of the production and
the hydrogen-dissolved water always having the prescribed
concentration of the dissolved hydrogen could be produced. Even
when the flow rate of the ultra-pure water changed, the amount of
supply of hydrogen was controlled proportionally to the change in
the amount of the ultra-pure water and therefore, the
hydrogen-dissolved water always having the prescribed concentration
of the dissolved hydrogen could be produced.
INDUSTRIAL APPLICABILITY
[0063] In accordance with the apparatus for continuous dissolution
and the process for continuous dissolution of the present
invention, the solution having a constant concentration of a gas
can be obtained with stability even when the flow rate of the main
stream liquid changes. In particular, cleaning water or surface
treatment water used for electronic materials which particularly
requires a precisely clean surface can be supplied without loss and
the cleaning treatment or the surface treatment can be conducted
with excellent reproducibility. When a small flow rate set for
saving water is increased to a flow rate in the ordinary condition,
the concentration of the gas dissolved into functional water is
always kept constant, the time lag for stabilization is eliminated
and the loss in water can be prevented.
[0064] Using the apparatus for supplying gas-dissolved water,
unused functional water in an excess amount can be collected and
reused.
* * * * *