Apparatus for producing gas-dissolved water and method for producing gas-dissolved water

Abstract

The present invention provides a gas-dissolved water production apparatus that can reliably discharge condensed water accumulated in the gas phase chamber of a gas dissolution module without altering the gas pressure or gas volume within the gas phase chamber. [Solution] A gas-dissolved water production apparatus for producing gas-dissolved water by dissolving gas in water to be treated, comprising: a gas-dissolved membrane module in which a gas phase chamber and a liquid phase chamber are separated by a gas-dissolved membrane; and a condensed water discharge mechanism for discharging condensed water condensed in the gas phase chamber, wherein the condensed water discharge mechanism comprises: a condensed water storage section for storing condensed water discharged from the gas phase chamber; a first valve disposed on the primary side of the condensed water storage section, which is on the gas phase chamber side; a second valve disposed on the secondary side, which is on the opposite side of the condensed water storage section from the first valve; and a drainage control unit that alternately opens and closes the first valve and the second valve while discharging the condensed water discharged from the gas phase chamber to the outside via the condensed water storage section.

Description

Technical Field

[0001] The present invention relates to a gas-dissolved water production apparatus and a gas-dissolved water production method using a gas-dissolving membrane module for producing gas-dissolved water.

Background Art

[0002] In the cleaning of parts for the electronics industry and in cutting and polishing processes, gas-dissolved water in which a specific gas is dissolved in a predetermined amount is used. The gas varies depending on the cleaning purpose and the material of the parts for the electronics industry, such as hydrogen gas or nitrogen gas. Regardless of the type of gas, gas-dissolved water is produced by dissolving the gas in ultrapure water.

[0003] As a means for dissolving a gas in ultrapure water to produce gas-dissolved water, a method using a gas-dissolving module partitioned into a gas phase chamber and a liquid phase chamber by a gas permeable membrane is generally known (see, for example, Patent Document 1).

[0004] In the gas-dissolving module, a gas such as hydrogen gas or nitrogen gas moves from the gas phase chamber through the gas-dissolving membrane to the liquid phase chamber and dissolves in the water on the liquid phase chamber side. At this time, the water does not move from the liquid phase chamber through the gas permeable membrane to the gas phase chamber. However, water vapor generated from the water in the liquid phase chamber may diffuse through the gas permeable membrane into the gas phase chamber, condense in the gas phase chamber, and accumulate as condensed water on the gas phase chamber side.

[0005] [[ID=Four]]

[0006] Here, Patent Document 1 describes a method for discharging condensed water in the gas phase chamber. In this method, the condensed water is stored in a condensed water storage section communicated with the gas phase chamber, and when the amount of condensed water reaches a certain level or more, a valve provided on the secondary side of the condensed water storage section is opened to discharge the condensed water.

[0007] ​ Furthermore, in the invention described in Patent Document 1, when discharging condensed water from the gas phase chamber, the opening time of the secondary valve of the condensed water storage section is controlled so that the condensed water in the condensed water storage section does not run out and the decrease in gas pressure in the gas phase chamber is 5 kPa or less. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 7328840 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, the invention described in Patent Document 1 had the problem that condensed water could not be reliably drained. Specifically, when discharging condensed water from the gas phase chamber, the opening time of the secondary valve in the condensed water storage section is controlled so that the condensed water in the storage section does not run out and the decrease in gas pressure in the gas phase chamber is 5 kPa or less. In this case, even a slight fluctuation in the gas pressure in the gas phase chamber leads to a problem where the dissolved gas concentration in the gas-dissolved water fluctuates, making it impossible to reliably discharge the condensed water.

[0010] The object of the present invention is to provide a gas-dissolved water production apparatus and a gas-dissolved water production method that can reliably discharge condensed water accumulated in the gas phase chamber of a gas dissolution module without changing the gas pressure or gas volume in the gas phase chamber. [Means for solving the problem]

[0011] In other words, the present invention provides, for example, the following means to solve the above problems. According to an embodiment of the present invention, A gas-dissolved water production apparatus that produces gas-dissolved water by dissolving gas in water to be treated, A gas-dissolved membrane module in which a gas-phase chamber and a liquid-phase chamber are separated by a gas-dissolved membrane, A condensate discharge mechanism for discharging the condensed water condensed in the gas phase chamber, Equipped with, The aforementioned condensate discharge mechanism is A condensate storage section for storing condensate discharged from the gas phase chamber, A first valve is provided on the primary side of the condensate storage section, which is the gas phase chamber side. A second valve is located on the secondary side, opposite to the first valve, with the aforementioned condensate storage section in between. A drainage control unit that alternately opens and closes the first valve and the second valve, and discharges the condensed water discharged from the gas phase chamber to the outside via the condensed water storage unit, A gas-dissolved water production apparatus is provided, which includes the following features.

[0012] Furthermore, according to another aspect of the present invention, Using the gas-dissolved water production apparatus described above, A method for producing gas-dissolved water is provided, which includes a control step in which the drainage control unit alternately opens and closes the first valve and the second valve, and discharges the condensed water discharged from the gas phase chamber to the outside through the condensed water storage unit. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a gas-dissolved water production apparatus and a gas-dissolved water production method that can reliably discharge condensed water accumulated in the gas phase chamber without changing the gas pressure or gas volume in the gas phase chamber of the gas dissolution module. [Brief explanation of the drawing]

[0014] [Figure 1] This diagram shows an overview of the configuration of a gas-dissolved water production apparatus according to an embodiment. [Figure 2] This diagram shows an overview of the configuration of the gas dissolution membrane module and condensate discharge mechanism according to the embodiment. [Figure 3] This diagram shows an overview of the configuration of a gas-dissolved water production apparatus according to another embodiment. [Modes for carrying out the invention]

[0015] Hereinafter, a gas-dissolved water production apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an outline of the configuration of the gas-dissolved water production apparatus according to the embodiment. As shown in FIG. 1, the gas-dissolved water production apparatus 2 is an apparatus that dissolves gas in treated water to produce gas-dissolved water, and is connected to a semiconductor component cleaning apparatus 100 via a gas-dissolved water drainage line L10 described later. In the following description, the side where the fluid flows in as viewed from the reference object is defined as the primary side, and the side where the fluid flows in is defined as the secondary side.

[0016] <Gas-dissolved water production apparatus> The gas-dissolved water production apparatus 2 includes a gas-dissolving membrane module 4 and a condensate discharge mechanism 6. The gas-dissolving membrane module 4 is connected to a treated water supply line L2 for supplying treated water, a gas supply line L4 for supplying gas, a surplus gas discharge line L6 for discharging surplus gas, a condensate discharge line L8 for discharging condensate, and a gas-dissolved water drainage line L10 for discharging gas-dissolved water, respectively.

[0017] (Gas-dissolving membrane module) The gas-dissolving membrane module 4 includes a gas phase chamber 4a and a liquid phase chamber 4b partitioned by a gas-dissolving membrane 4x. The gas-dissolving membrane 4x has gas permeability and has a membrane structure in which liquid water cannot substantially permeate. A membrane having such a structure is also referred to as a gas-liquid separation membrane or a gas separation membrane.

[0018] Here, as an example of the gas-dissolving membrane 4x, a fluororesin hollow fiber membrane can be mentioned. In this case, as shown in FIG. 2, the gas-dissolving membrane module 4 is filled with a large number of fluororesin hollow fiber membranes, a liquid phase chamber 4b is formed inside the fluororesin hollow fiber membrane, and a gas phase chamber 4a is formed outside the fluororesin hollow fiber membrane.

[0019] (Condensate discharge mechanism) The condensate discharge mechanism 6 includes a condensate storage section 8 for storing condensate condensed in the gas phase chamber 4a, a first valve V8a disposed on the primary side (gas phase chamber 4a side) of the condensate storage section 8, a second valve V8b disposed on the secondary side (opposite the first valve V8a across the condensate storage section 8), a drainage control unit 12 that alternately opens and closes the first valve V8a and the second valve V8b to discharge the condensate discharged from the gas phase chamber 4a to the outside via the condensate storage section 8, and a liquid level sensor 14 (LS) for detecting the liquid level of condensate stored in the condensate storage section 8.

[0020] Here, the first valve V8a and the second valve V8b can be automatic valves such as electromagnetic, electric, or pneumatic valves. The first valve V8a and the second valve V8b may also be on-off valves. In addition, the liquid level sensor 14 can be a liquid level gauge that utilizes light, ultrasound, capacitance, etc., and at least one is installed between the gas phase chamber 4a and the condensate storage section 8.

[0021] <Method for producing gas-dissolved water> Hereinafter, a method for producing gas-dissolved water using a gas-dissolved water production apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[0022] First, the water to be treated is supplied to the gas dissolution membrane module 4 via the water to be treated supply line L2, and the information obtained by the flow indicator alarm meter 17 (FIA) is transmitted to the control unit 19 via wireless or wired connection.

[0023] The water to be treated is basically pure water. The resistivity of pure water (at 25°C) is, for example, 0.1 MΩ·cm or higher. Here, pure water includes ultrapure water with a resistivity of more than 15 MΩ·cm or more than 18 MΩ·cm. In this embodiment, the case in which pure water is used as the water to be treated is illustrated.

[0024] Meanwhile, the gas-dissolved membrane module 4 is supplied with gas via the gas supply line L4. The gas used can be hydrogen gas, nitrogen gas, oxygen gas, carbon dioxide gas, or ozone gas. This embodiment describes an example where ozone gas is supplied.

[0025] In the ozone gas production process, first, oxygen gas to which a small amount of nitrogen gas has been added is ozonated in an ozone gas generator (not shown) to produce ozone-containing gas, and then carbon dioxide gas is added to the ozone-containing gas to produce ozone gas.

[0026] In this process, the supply amounts of oxygen, nitrogen, and carbon dioxide are controlled by the Mass Flow Controller (MFC) 16. The supply amounts are instructed by the control unit 19 via electrical signals, either wirelessly or via a wired connection.

[0027] The addition of carbon dioxide to ozone-containing gas is done to suppress the self-decomposition characteristic of ozone. This self-decomposition is more pronounced in the state of ozone-dissolved water than in the state of ozone-containing gas, hence the addition of carbon dioxide to the ozone-containing gas.

[0028] As described above, pure water is supplied to the liquid phase chamber 4b of the gas dissolution membrane module 4, i.e., the inside of the fluororesin hollow fiber membrane, via the treated water supply line L2, and ozone gas is supplied to the gas phase chamber 4a of the gas dissolution membrane module 4, i.e., the outside of the fluororesin hollow fiber membrane, via the gas supply line L4. Any method can be used to supply ozone gas to the gas phase chamber 4a, such as a flow rate proportional control method or a pressure PID control method [a pressure control method combining three elements: proportional (P), integral (I), and differential (D)].

[0029] (Ozone gas dissolution) Ozone gas supplied to the gas phase chamber 4a permeates through the gas dissolution membrane 4x and moves to the liquid phase chamber 4b, where it dissolves in the pure water in the liquid phase chamber 4b, producing ozone-dissolved water. Here, water vapor generated from the pure water in the liquid phase chamber 4b may permeate through the gas dissolution membrane 4x and move to the gas phase chamber 4a. In this case, the water vapor that moves to the gas phase chamber 4a condenses to form condensed water, which may remain in the gas phase chamber 4a. If condensed water is formed, it is discharged from the gas phase chamber 4a by the condensed water discharge mechanism 6.

[0030] (Excess gas emissions) A portion of the ozone-containing gas supplied to the gas phase chamber 4a is detoxified by an excess ozone gas decomposition catalyst cylinder (not shown) and then discharged to the outside through the excess gas discharge line L6.

[0031] Here, a treated water pressure sensor 18 is installed in the treated water supply line L2 to measure the water pressure of the treated water, an exhaust pressure sensor 20 is installed in the excess gas discharge line L6 to measure the exhaust pressure of the gas phase chamber 4a, and a gas dissolved water pressure sensor 22 is installed in the gas dissolved water drainage line L10 to measure the water pressure of the gas dissolved water discharged from the liquid phase chamber 4b.

[0032] The pressure control unit 15 appropriately detects the operating pressure of the gas phase chamber 4a, the supply air pressure to the liquid phase chamber 4b, and the water pressure on the secondary side of the liquid phase chamber 4b (gas-dissolved water drainage line L10 side) using the treated water pressure sensor 18, the exhaust pressure sensor 20, and the gas-dissolved water pressure sensor 22.

[0033] Here, the operating pressure of the gas phase chamber 4a is calculated using the correlation between the gas flow rate of the gas phase chamber 4a and a constant pressure loss. The gas flow rate of the gas phase chamber 4a is calculated from the exhaust pressure measured by the exhaust pressure sensor 20. The constant pressure loss can be preset using the pressure control unit 15.

[0034] Next, the pressure control unit 15 uses the pressure regulating valve V6 to adjust the pressure so that the operating pressure of the gas phase chamber 4a exceeds atmospheric pressure and the pressure supplied to the gas phase chamber 4a is lower than the water pressure on the secondary side of the liquid phase chamber 4b (gas dissolved water drainage line L10 side) (pressure adjustment process).

[0035] This prevents ozone gas from flowing from the gas phase chamber 4a into the liquid phase chamber 4b and mixing bubbles into the gas-dissolved water, even if the water pressure in the liquid phase chamber 4b decreases. As a result, the supply pressure to the gas phase chamber 4a is increased, and the dissolved gas concentration in the gas-dissolved water can be maintained at a high level. In addition, condensed water can be easily discharged from the gas phase chamber 4a without the need for a separate pump.

[0036] (Discharge of ozone-dissolved water) The ozone-dissolved water generated in the liquid phase chamber 4b is discharged from the gas-dissolved water drainage line L10. The discharged ozone-dissolved water is used, for example, in semiconductor component cleaning equipment for cleaning silicon wafers and glass substrates, rinsing, promoting oxidation, and inhibiting oxidation.

[0037] When discharging ozone-dissolved water, the pressure control unit 15 measures the ozone concentration of the ozone-dissolved water using a dissolved ozone concentration meter 26, and uses the measured ozone concentration to operate the pressure regulating valve V6 to increase or decrease the supply pressure of ozone gas, thereby obtaining ozone-dissolved water with a predetermined ozone concentration. Note that the increase or decrease in the supply pressure of ozone gas may also be achieved by controlling the output of an ozone gas generator (not shown). Furthermore, it is preferable to use an ultraviolet absorption type dissolved ozone concentration meter 26 that does not contaminate the ozone-dissolved water.

[0038] (Condensate discharge) In the condensate discharge mechanism 6, the first valve V8a and the second valve V8b are normally set to a closed state. When condensate is generated in the gas phase chamber 4a, the condensate is discharged to the condensate discharge line L8 which communicates with the gas phase chamber 4a. When the condensate is discharged, the drainage control unit 12 alternately opens and closes the first valve V8a and the second valve V8b, and the condensate discharged from the gas phase chamber 4a is discharged to the outside via the condensate storage unit 8 (control process). This control process will be described in detail below.

[0039] When the drainage control unit 12 detects, using a sensor (not shown), that condensed water has been discharged from the outlet of the gas phase chamber 4a, it opens the first valve V8a while keeping the second valve V8b closed (first step). As a result, the condensed water discharged from the gas phase chamber 4a is stored in the condensed water storage unit 8.

[0040] Next, the drainage control unit 12 uses the liquid level sensor 14 to detect the liquid level of the condensate stored in the condensate storage unit 8. When the condensate liquid level exceeds a predetermined threshold, the first valve V8a is closed while the second valve V8b remains closed (second step). This blocks communication between the gas phase chamber 4a and the condensate storage unit 8, preventing condensate from moving from the gas phase chamber 4a to the condensate storage unit 8. If the condensate liquid level does not exceed the predetermined threshold, the first valve V8a remains open.

[0041] Here, it is preferable to set the predetermined threshold so that the decrease in operating pressure in the gas phase chamber 4a due to the opening and closing of the first valve V8a and the second valve V8b is 10 kPa or less, in order to maintain a nearly constant dissolved gas concentration in the gas dissolution water. If the decrease in operating pressure in the gas phase chamber 4a due to the opening and closing of the first valve V8a and the second valve V8b exceeds 10 kPa, the dissolved gas concentration will decrease, making it difficult to maintain a constant dissolved gas concentration in the gas dissolution water.

[0042] Next, the drainage control unit 12 opens the second valve V8b while the first valve V8a is closed. This causes the condensed water stored in the condensed water storage unit 8 to be discharged to the outside of the gas-dissolved water production device 2 (third step).

[0043] Here, the condensed water may be discharged naturally from the condensed water storage section 8 by gravity, or it may be discharged from the condensed water storage section 8 using a vacuum pump. Of course, the condensed water may also be discharged from the condensed water storage section 8 by other methods.

[0044] Next, the drainage control unit 12 closes the second valve V8b while the first valve V8a is closed. This isolates the condensate storage unit 8 from the gas phase chamber 4a and the outside of the gas-dissolved water production device 2 (fourth step).

[0045] In this way, during the control process, by draining the condensed water while alternately opening and closing the first valve V8a and the second valve V8b, while simultaneously shutting off communication between the gas phase chamber 4a and the condensed water storage section 8, the condensed water in the condensed water storage section 8 can be accurately drained without changing the gas pressure or gas volume in the gas phase chamber 4a, and the condensed water remaining in the gas phase chamber 4a can be reliably discharged.

[0046] Furthermore, after the condensate is discharged, the condensate in the condensate storage section 8 is depleted, which allows for a longer interval between condensate discharges and reduces the frequency of opening and closing the first valve V8a and the second valve V8b. Furthermore, after the fourth step is completed, the drainage control unit 12 may return to the first step and repeat the first, second, third, and fourth steps multiple times in the control process. This makes it possible to more reliably empty the condensate in the condensate storage section 8 and discharge the condensate that remains in the gas phase chamber 4a.

[0047] In this embodiment, the example given is the use of pure water as the water to be treated, but the water to be treated is not necessarily limited to pure water. For example, carbonated water (pure water with carbon dioxide dissolved in it beforehand), diluted chemical water (water with added chemicals), or degassed water (ultrapure water from which dissolved gaseous components have been removed) may be used as the water to be treated.

[0048] Furthermore, although this embodiment illustrates the case where carbon dioxide is added to the ozone-containing gas on the secondary side (downstream side) of the ozone gas generator, the suppression of ozone self-decomposition can also be achieved by adding carbon dioxide on the primary side (upstream side) of the ozone gas generator, or by supplying carbonated water, in which carbon dioxide has been pre-dissolved in pure water, to the liquid phase chamber 4b.

[0049] Furthermore, in this embodiment, a pressure regulating valve V6 is provided to adjust the operating pressure of the gas phase chamber 4a to a pressure exceeding atmospheric pressure. However, if the operating pressure of the gas phase chamber 4a exceeds atmospheric pressure, it is not necessary to provide the pressure regulating valve V6.

[0050] Furthermore, the operating pressure of the gas phase chamber 4a may change from positive to negative pressure due to the drainage of condensed water. Considering these circumstances, the pressure regulating valve V6 is not necessarily limited to adjusting the operating pressure of the gas phase chamber 4a to a pressure exceeding atmospheric pressure; it is sufficient to adjust it to any target pressure within a predetermined range based on atmospheric pressure.

[0051] Furthermore, in this embodiment, the operating pressure of the gas phase chamber 4a is calculated using the correlation between the gas flow rate of the gas phase chamber 4a and a constant pressure loss, but other methods may also be used. Specifically, the operating pressure of the gas phase chamber 4a may be calculated using the gas pressure at the condensate outlet if no condensate is present in the gas phase chamber 4a, or using the gas pressure at the point in contact with the condensate if condensate is present in the gas phase chamber 4a. Alternatively, the gas pressure at the gas outlet of the gas phase chamber 4a can be simply adopted as the operating pressure of the gas phase chamber 4a.

[0052] In this embodiment, as shown in Figure 1, a countercurrent configuration is illustrated in which gas is supplied from the top of the gas dissolution membrane module 4 and pure water is supplied from the bottom. However, the embodiment is not necessarily limited to this configuration. For example, gas may be supplied from the bottom of the gas dissolution membrane module 4 and pure water from the top, and these may flow in a countercurrent.

[0053] Furthermore, in this embodiment, the control unit 19 is shown as an example in which the supply amounts of oxygen gas, nitrogen gas, and carbon dioxide gas are adjusted by transmitting information obtained from the flow rate indicator alarm meter 17 to the mass flow controller 16, but the adjustment of the gas supply amounts is not necessarily limited to this.

[0054] For example, as shown in Figure 3, a pressure indicator alarm meter (PIA) may be installed in the gas supply line L4, and the information obtained by the pressure indicator alarm meter 27 may be transmitted to the control unit 19 via wireless or wired connection. The control unit 19 may then use this information to transmit instructions to the mass flow controller 16 to adjust the supply amounts of oxygen gas, nitrogen gas, and carbon dioxide gas. [Explanation of symbols]

[0055] 2. Gas-dissolved water production apparatus 4. Gas-dissolved membrane module 4a Gas phase chamber 4b Liquid phase chamber 4x gas-dissolved membrane 6. Condensate discharge mechanism 8. Condensate storage section 12 Drainage Control Unit 14. Liquid level sensor 15 Pressure Control Unit 16 Mass Flow Controller 17 Flow rate indicator and alarm meter 18. Water pressure sensor for processing 19 Control Unit 20 Exhaust pressure sensor 22 Gas dissolution water pressure sensor 26. Dissolved Ozone Concentration Meter 27 Pressure Indicator Alarm 100 Washing device L2 Water to be treated supply line L4 gas supply line L6 Excess Gas Discharge Line L8 Condensate discharge line V6 Pressure Regulating Valve V8a First valve V8b Second valve L10 Gas-dissolved water drainage line

Claims

1. A gas-dissolved water production apparatus that produces gas-dissolved water by dissolving gas in water to be treated, A gas-dissolved membrane module in which a gas-phase chamber and a liquid-phase chamber are separated by a gas-dissolved membrane, A condensate discharge mechanism for discharging the condensed water condensed in the gas phase chamber, Equipped with, The aforementioned condensate discharge mechanism is A condensate storage section for storing condensate discharged from the gas phase chamber, A first valve is provided on the primary side of the condensate storage section, which is the gas phase chamber side. A second valve is located on the secondary side, opposite to the first valve, with the aforementioned condensate storage section in between. A drainage control unit that alternately opens and closes the first valve and the second valve, and discharges the condensed water discharged from the gas phase chamber to the outside via the condensed water storage unit, A gas-dissolved water production apparatus equipped with the following features.

2. The condensate storage section is equipped with a liquid level sensor that detects the liquid level of the condensate stored in the condensate storage section. The gas-dissolved water production apparatus according to claim 1, wherein the drainage control unit controls the opening and closing of the first valve and the second valve using the liquid level of the condensed water detected by the liquid level sensor as a threshold.

3. The gas-dissolved water production apparatus according to claim 2, wherein the threshold of the liquid level of the condensed water is set such that the decrease in the operating pressure of the gas phase chamber is 10 kPa or less.

4. The gas-dissolved water production apparatus according to claim 1, further comprising a pressure control unit that adjusts the operating pressure of the gas phase chamber to an arbitrary target pressure within a predetermined range based on atmospheric pressure.

5. The gas-dissolved water production apparatus according to any one of claims 1 to 4, wherein the gas is hydrogen gas, nitrogen gas, oxygen gas, carbon dioxide gas, or ozone gas.

6. A method for producing gas-dissolved water using the gas-dissolved water production apparatus described in claim 1, A method for producing gas-dissolved water, comprising a control step in which the drainage control unit alternately opens and closes the first valve and the second valve, and discharges the condensed water discharged from the gas phase chamber to the outside through the condensed water storage unit.

7. The control process described above is: The first step involves opening the first valve and closing the second valve to store the condensed water discharged from the gas phase chamber in the condensed water storage section. The second step involves closing the first valve while the second valve is closed, thereby isolating the gas phase chamber from the condensed water storage section. A third step involves opening the second valve while the first valve is closed, thereby discharging the condensed water stored in the condensed water storage section to the outside. A fourth step involves closing the second valve while the first valve is closed, thereby isolating the condensate storage section from the outside. A method for producing gas-dissolved water according to claim 6, including the method described in claim 6.

8. The method for producing gas-dissolved water according to claim 7, wherein the condensed water discharged from the gas phase chamber is discharged to the outside through the condensed water storage section by repeating the first step, the second step, the third step, and the fourth step.

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