JP7205263B2 - Water treatment method and water treatment system - Google Patents

Description

The present invention relates to a water treatment method and a water treatment system, and more particularly to a water treatment method and a water treatment system capable of safely treating hydrogen gas generated in a cathode chamber of an electrodeionization apparatus.

Electrodeionization equipment is often used in treatment equipment and treatment systems for raw water containing organic substances, especially persistent organic substances. For example, it produces ultrapure water used in semiconductor manufacturing processes. In the ultrapure water production equipment for , an electrodeionization equipment is used to remove the TOC component and produce deionized water in the primary pure water system. Such an electrodeionization apparatus typically has a plurality of anion exchange membranes and cation exchange membranes alternately arranged between an anode compartment having an anode and a cathode compartment having a cathode, as shown in FIG. Thus, it has a configuration in which the concentration chambers and the deionization chambers are alternately partitioned. The desalting chamber is filled with an ion exchange resin, and electrode water is passed through the anode chamber and the cathode chamber to ensure conductivity.

When raw water is passed through the desalting chamber of the electrodeionization apparatus as described above, the impurity ions in the raw water are adsorbed by the ion exchange resin in the desalting chamber, resulting in highly desalted pure water (deionized water). manufactured. On the other hand, the impurity ions adsorbed by the ion exchange resin in the demineralization chamber move to the concentration chamber by applying a direct current through the ion exchange membrane, so the concentration chamber produces concentrated water in which ions are concentrated. leak. At this time, in the cathode chamber of the electrodeionization apparatus, hydrogen is generated together with OH ^- by the reaction represented by the following formula (1). hydrogen gas is mixed in.
2H ₂ O + 2e ⁻ → 2OH ⁻ +H ₂ (1)

Since hydrogen gas is an explosive and combustible gas, it is essential to deal with this hydrogen gas when treating the waste water flowing out of the cathode chamber of the electrodeionization apparatus. Therefore, usually, the wastewater flowing out from the cathode chamber of the electrodeionization apparatus is transferred to the hydrogen treatment apparatus through a transfer line, and after gas-liquid separation using a bubble column or a scrubber, the separated hydrogen gas is treated with nitrogen or the like. Safety is ensured by diluting it with an inert gas and then exhausting it to the outside.

The evacuation method itself using the above-described hydrogen treatment apparatus does not pose any particular safety problems. However, during the transfer to the hydrogen treatment apparatus, hydrogen gas generated as bubbles from the waste water containing hydrogen gas may accumulate in the bent parts of the pipes that make up the transfer line. This could pose a security problem. As a countermeasure, the piping route is configured and the flow velocity is ensured so that hydrogen gas does not accumulate in the piping. Since there are cases, further measures are desired.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a water treatment method and a water treatment system capable of safely treating hydrogen gas generated in the cathode chamber of an electrodeionization apparatus. .

The first aspect of the present invention is a water treatment method for treating hydrogen gas-containing water in a transfer line that connects an electrodeionization apparatus and a hydrogen treatment apparatus that treats hydrogen gas generated by the electrodeionization apparatus, A bubble observing step of observing whether bubbles are mixed in the hydrogen gas-containing water, a pressure measuring step of measuring the pressure in the transfer line, an observation result of the bubble observing step and a measurement of the pressure measuring step. and a pressure adjustment step of adjusting the pressure in the transfer line based on the result (Invention 1).

According to this invention (Invention 1), in the bubble observation step, it is observed whether bubbles are mixed in the hydrogen gas-containing water, and in the pressure measurement step, the pressure in the transfer line is measured, and in the pressure adjustment step, By adjusting the pressure in the transfer line based on the observation result of the bubble observation process and the measurement result of the pressure measurement process, hydrogen gas generated as bubbles in the transfer line can be dissolved in water. Even if the flow rate of gas-containing water is reduced, it is possible to prevent hydrogen gas from being generated as bubbles in the transfer line. Therefore, no matter what piping route the transfer line connecting the electrodeionization apparatus and the hydrogen treatment apparatus has, the hydrogen gas-containing water is transferred to the hydrogen treatment apparatus. It is possible to prevent hydrogen gas from accumulating, so that hydrogen gas generated in the electrodeionization apparatus can be safely treated.

In the above invention (Invention 1), it is preferable that the set range of the pressure in the transfer line adjusted in the pressure adjustment step is 0.1 MPa to 0.99 MPa (Invention 2).

According to this invention (Invention 2), the hydrogen gas generated as bubbles in the transfer line can be more efficiently dissolved in water.

In the above inventions (inventions 1 and 2), it is preferable that the pressure adjustment step is performed immediately before the hydrogen gas-containing water is supplied to the hydrogen treatment device (invention 3).

Hydrogen gas bubbles dissolved in the water by adjusting the pressure in the transfer line may regenerate over time. According to this invention (invention 3), immediately before supplying the hydrogen gas-containing water to the hydrogen treatment device, the hydrogen gas generated as bubbles can be dissolved in the water, so that hydrogen can be produced in a safe state. Gas-laden water can be fed to the hydrotreating unit.

Secondly, the present invention provides an electrodeionization device, a hydrogen treatment device for separating and removing hydrogen gas from hydrogen gas-containing water flowing out of the electrodeionization device, and a discharge port of the cathode chamber, which communicates with the hydrogen gas. and a transfer line capable of supplying the contained water to the hydrogen treatment device, wherein the transfer line is provided with an area flow meter, a pressure gauge and a pressure regulating valve (Invention 4).

According to this invention (Invention 4), when it is observed that bubbles are mixed in the hydrogen gas-containing water with the area flow meter, based on the pressure in the transfer line measured by the pressure gauge, By adjusting the pressure in the transfer line with the pressure regulating valve, the hydrogen gas generated as bubbles in the transfer line can be dissolved in water. Even so, it is possible to prevent the generation of hydrogen gas as bubbles in the transfer line. Therefore, no matter what piping route the transfer line connecting the electrodeionization apparatus and the hydrogen treatment apparatus has, the hydrogen gas-containing water is transferred to the hydrogen treatment apparatus. It is possible to prevent hydrogen gas from accumulating, so that hydrogen gas generated in the electrodeionization apparatus can be safely treated.

In the above invention (invention 4), it is preferable that the set range of the pressure in the transfer line adjusted by the pressure regulating valve is 0.1 MPa to 0.99 MPa (invention 5).

According to this invention (Invention 2), the hydrogen gas generated as bubbles in the transfer line can be more efficiently dissolved in water.

In the above inventions (inventions 4 and 5), it is preferable that the pressure regulating valve is provided in the immediate vicinity of the hydrogen treatment device (invention 6).

Since there is no back pressure on the secondary side of the pressure regulating valve, bubbles of hydrogen gas dissolved in the water by adjusting the pressure in the transfer line may be generated again. According to this invention (Invention 3), the hydrogen gas generated as bubbles in the immediate vicinity of the hydrogen treatment device can be dissolved in water by the pressure regulating valve. can be fed to the hydrotreating unit.

According to the water treatment method and water treatment system of the present invention, in the bubble observation step, it is observed whether or not bubbles are mixed in the hydrogen gas-containing water, and in the pressure measurement step, the pressure in the transfer line is measured, and the pressure In the adjustment process, the pressure in the transfer line is adjusted based on the observation result in the bubble observation process and the measurement result in the pressure measurement process, so that the hydrogen gas generated as bubbles in the transfer line can be dissolved in water. Therefore, even if the flow rate of the hydrogen gas-containing water is reduced, it is possible to prevent hydrogen gas from being generated as bubbles in the transfer line. Therefore, no matter what piping route the transfer line connecting the electrodeionization apparatus and the hydrogen treatment apparatus has, the hydrogen gas-containing water is transferred to the hydrogen treatment apparatus. It is possible to prevent hydrogen gas from accumulating, so that hydrogen gas generated in the electrodeionization apparatus can be safely treated.

It is a mimetic diagram showing a water treatment system concerning one embodiment of the present invention. It is a schematic diagram showing a general electrodeionization apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a water treatment method and a water treatment system of the present invention will be described with reference to the drawings as appropriate. The embodiments described below are intended to facilitate understanding of the present invention, and are not intended to limit the present invention.

[Water treatment system]
FIG. 1 is a schematic diagram showing a water treatment system 10 according to one embodiment of the invention. A water treatment system 10 shown in FIG. The electrodeionization apparatus 1 removes impurity ions in raw water W to produce deionized water W1. The hydrogen treatment device 2 separates and removes hydrogen gas from the hydrogen gas-containing water D flowing out from the cathode chamber 12 of the electrodeionization device 1 . The area-type flowmeter 3 measures the flow rate of the hydrogen gas-containing water D flowing through the transfer line L3. The pressure gauge 4 measures the pressure inside the transfer line L3. The pressure regulating valve 5 regulates the pressure inside the transfer line L3. The pressure control means 6 controls the pressure regulating valve 5 based on the pressure in the transfer line L3 measured by the pressure gauge 4. As shown in FIG.

As shown in FIG. 1, the electrodeionization apparatus 1 is communicated with a raw water supply line L1 for supplying raw water W, and a process for discharging the deionized water W1 produced in the demineralization chamber. The water discharge line L2 is in communication. Further, the cathode chamber 12 of the electrodeionization device 1 is communicated with a transfer line L3 for supplying the hydrogen gas-containing water D flowing out of the cathode chamber 12 to the hydrogen treatment device 2 . In addition to the raw water supply line L1, the treated water discharge line L2, and the transfer line L3, the electrodeionization apparatus 1 also includes lines for discharging concentrated water from the concentration chamber and waste water flowing out from the anode chamber 11. are in communication with each other, but the illustration thereof is omitted in FIG.

[Electrodeionization device]
The electrodeionization apparatus 1 removes impurity ions in the raw water W to produce deionized water W1, and has a plurality of anion exchanges between an anode chamber 11 having an anode and a cathode chamber 12 having a cathode. By alternately arranging membranes and cation exchange membranes, it has a configuration in which concentration compartments and deionization compartments are alternately partitioned, and the concentration compartments and deionization compartments are filled with an ion exchange resin. In addition, in FIG. 1, the concentrating compartment and the desalting compartment are omitted.

When the raw water W is passed through the desalting chamber of the electrodeionization apparatus 1, impurity ions in the raw water W are adsorbed by the ion exchange resin in the desalting chamber to produce deionized water W1. The produced deionized water is discharged to the outside through the treated water discharge line L2. On the other hand, the impurity ions adsorbed by the ion exchange resin in the demineralization chamber move to the concentration chamber by applying a direct current through the ion exchange membrane, so the concentration chamber produces concentrated water in which ions are concentrated. leak. At this time, in the cathode chamber 12 of the electrodeionization apparatus 1, hydrogen is generated together with OH ⁻ by the reaction represented by the following formula (1). Hydrogen gas generated by the reaction is mixed.
2H ₂ O + 2e ⁻ → 2OH ⁻ +H ₂ (1)

[Hydrogen treatment device]
The hydrogen treatment device 2 separates and removes hydrogen gas from the hydrogen gas-containing water D flowing out from the cathode chamber 12 of the electrodeionization device 1. is connected to the outlet 121 of the The configuration of the hydrogen treatment device 2 is not particularly limited as long as hydrogen can be separated and removed from the hydrogen gas-containing water D, and has a bubble column, a scrubber, etc., and uses these to remove the hydrogen gas-containing water D After gas-liquid separation, the separated hydrogen gas is diluted with an inert gas such as nitrogen and discharged to the outside.

[Area type flow meter]
The area-type flow meter 3 measures the flow rate of the hydrogen gas-containing water D flowing through the transfer line L3. In the present embodiment, in addition to measuring the flow rate of the hydrogen gas-containing water D, It is also used to observe whether or not air bubbles are mixed in the water D. As the area type flowmeter 3, for example, a float type having a vertically extending tapered tube and a float that moves up and down according to the flow rate of the liquid flowing through the tapered tube can be used. can. In the area type flow meter 3, if air bubbles are mixed in the liquid, an abnormal float operation occurs in the tapered pipe, a so-called hunting phenomenon occurs. It is possible to check whether or not When it is observed that bubbles are mixed in the hydrogen gas-containing water D in the area type flow meter 3, the hydrogen gas generated as bubbles in the transfer line L3 is dissolved in the water. The pressure control means 5 may control the pressure regulating valve 5 based on the pressure in the transfer line L3 measured by the pressure gauge 4. The area-type flowmeter 3 is preferably provided on the primary side of the pressure regulating valve 5 in the transfer line L3.

[Pressure gauge]
The pressure gauge 4 measures the pressure inside the transfer line L3. The structure of the pressure gauge 4 is not particularly limited as long as it can measure the pressure in the transfer line L3, and a commercially available one can be applied. Based on the pressure in the transfer line L3 measured by the pressure gauge 4, the pressure control valve 5 is controlled by the pressure control means 6, which will be described later. The pressure gauge 4 is preferably provided on the primary side of the area flow meter 3 in the transfer line L3.

[Pressure control valve]
The pressure regulating valve 5 regulates the pressure inside the transfer line L3. The structure of the pressure regulating valve 5 is not particularly limited as long as it can adjust the pressure in the transfer line L3 by opening and closing the pressure regulating valve 5, and a commercially available one can be applied. By adjusting the pressure in the transfer line L3 by opening and closing the pressure regulating valve 5, it is possible to dissolve the hydrogen gas generated as bubbles in the transfer line L3 into water. The setting range of the pressure in the transfer line L3, which is adjusted by the pressure regulating valve 5, is preferably 0.1 MPa-0.99 MPa. By adjusting the pressure applied to the hydrogen gas-containing water D in the transfer line L3 to a range of 0.1 MPa to 0.99 MPa by the pressure regulating valve 5, the hydrogen gas bubbles generated in the transfer line L3 are eliminated. It becomes possible to efficiently dissolve in water.

Moreover, the pressure regulating valve 5 is preferably provided in the immediate vicinity of the hydrogen treatment device 2 in the transfer line L3. Since there is no back pressure on the secondary side of the pressure regulating valve 5, there is a possibility that bubbles of hydrogen gas dissolved in water may be generated again by adjusting the pressure in the transfer line L3. Since the hydrogen gas generated as bubbles immediately before the hydrogen treatment device 2 can be dissolved in the water by being provided in the immediate vicinity of the device 2, the hydrogen gas-containing water can be transferred to the hydrogen treatment device 2 while maintaining safety. can be introduced into

[Pressure control means]
The pressure control means 6 controls the pressure regulating valve 5 based on the pressure in the transfer line L3 measured by the pressure gauge 4. As shown in FIG. The structure of the pressure control means 6 is not particularly limited as long as it can control the pressure regulating valve 5 based on the pressure in the transfer line L3 measured by the pressure gauge 4. The pressure regulating valve 5 may be directly controlled, or the pressure regulating valve 5 may be manually controlled by an operator.

[Water treatment method]
Next, a water treatment method using the water treatment system 1 described above will be described. First, when the raw water W is passed through the desalting chamber of the electrodeionization apparatus 1, impurity ions in the raw water W are adsorbed by the ion exchange resin in the desalting chamber to produce deionized water W1. The produced deionized water is discharged to the outside through the treated water discharge line L2. On the other hand, the impurity ions adsorbed by the ion exchange resin in the demineralization chamber move to the concentration chamber by applying a direct current through the ion exchange membrane, so the concentration chamber produces concentrated water in which ions are concentrated. leak. At this time, in the cathode chamber 12 of the electrodeionization apparatus 1, hydrogen is generated together with OH ^- by the reaction represented by the following formula (1). Hydrogen gas generated by the above reaction is mixed.
2H ₂ O + 2e ⁻ → 2OH ⁻ +H ₂ (1)
The hydrogen gas-containing water D flowing out of the cathode chamber 12 of the electrodeionization device 1 is introduced into the hydrogen treatment device 2 via the transfer line L3.

Until the hydrogen gas-containing water D is transferred to the hydrogen treatment device 2, in the transfer line L3, it is observed whether bubbles are mixed in the hydrogen gas-containing water D by the area flow meter 3 (bubble observation step), the pressure in the transfer line L3 is measured by the pressure gauge 4 (pressure measurement step). Then, when it is observed that hydrogen gas bubbles are mixed in the hydrogen gas-containing water D in the bubble observation step, based on the pressure in the transfer line L3 measured in the pressure measurement step, the pressure adjustment valve 5 adjusts the pressure in the transfer line L3 (pressure adjustment step). The adjustment of the pressure in the transfer line L3 by the pressure regulating valve 5 is controlled by the control means 6.

By adjusting the pressure in the transfer line L3 with the pressure regulating valve 5, the hydrogen gas generated as bubbles in the transfer line L3 can be dissolved in water. Even in this case, it is possible to prevent hydrogen gas from being generated as bubbles in the transfer line L3.

The set range of the pressure in the transfer line L3 adjusted in the pressure adjustment process is preferably 0.1 MPa-0.99 MPa. By keeping the pressure in the transfer line L3 within the above set range, the hydrogen gas generated as bubbles in the transfer line L3 can be more efficiently dissolved in water.

Moreover, the pressure adjustment step is preferably performed immediately before the hydrogen gas-containing water D is supplied to the hydrogen treatment device 2 by the pressure adjustment valve 5 provided in the immediate vicinity of the hydrogen treatment device 2 . Hydrogen gas bubbles dissolved in water by adjusting the pressure in the transfer line L3 may re-generate over time. By dissolving the hydrogen gas generated as bubbles just before the hydrogen gas-containing water D is supplied to the hydrogen treatment device 2 by the pressure regulating valve 5 provided in the immediate vicinity of the hydrogen treatment device 2, safety is ensured. The hydrogen gas-containing water can be supplied to the hydrogen treatment device 2 while maintaining the

As described above, the present invention has been described with reference to the drawings, but the present invention is not limited to the above-described embodiments, and various modifications can be made. For example, in the above embodiment, the pressure control valve 5 is controlled by the pressure control means 6, but the pressure control valve 5 itself may have pressure control means. In addition, in the above embodiment, for ease of explanation, the case where the water treatment system includes one electrodeionization device is taken as an example, but a plurality of electrodeionization devices are connected in parallel or in series. may have been

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[Example]
Using the water treatment system 10 shown in FIG. 1, hydrogen gas-containing water flowing out from the cathode chamber of an electrodeionization apparatus was treated. When the power of the electrodeionization apparatus was turned on, bubbles due to a large amount of hydrogen gas were visually observed in the area-type flow meter provided in the transfer line through which the hydrogen gas-containing water discharged from the cathode chamber was circulated. The amount of water at this time was about 1 m ³ /h per electrodeionization apparatus, and the piping pressure of the transfer line was about 0.03 MPa.

It was confirmed that when the back pressure was increased by throttling the pressure control valve on the downstream side of the area flow meter, the bubbles caused by the hydrogen gas in the hydrogen gas-containing water disappeared. The pressure in the transfer line at this time was approximately 0.3 MPa. It was confirmed that the bubbles caused by the hydrogen gas disappeared even when the pressure in the transfer line was about 0.1 MPa.

<Results/Discussion>
It was found that the hydrogen gas generated in the hydrogen gas-containing water was dissolved in the water by applying pressure to the transfer line using the pressure regulating valve, and the gas-liquid mixed state was lost. Since there is no back pressure on the secondary side of the pressure regulating valve, there is a possibility that bubbles of hydrogen gas dissolved in water due to adjustment of the pressure in the transfer line may be generated again. Therefore, the pressure regulating valve must be installed in the immediate vicinity of the hydrogen treatment device.

[Comparative example]
Using the water treatment system 10 shown in FIG. 1, hydrogen gas-containing water flowing out from the cathode chamber of an electrodeionization apparatus was treated. When the power of the electrodeionization apparatus was turned on, bubbles due to a large amount of hydrogen gas were visually observed in the area-type flow meter provided in the transfer line through which the hydrogen gas-containing water discharged from the cathode chamber was circulated. The amount of water at this time was about 1 m ³ /h per electrodeionization apparatus, and the piping pressure of the transfer line was about 0.03 MPa.

<Results/Discussion>
When the transfer line is not pressurized by the pressure regulating valve, the hydrogen gas-containing water mixed with bubbles due to the hydrogen gas is passed through the hydrogen treatment device in a gas-liquid mixed state. When the flow rate of the hydrogen gas-containing water is slow, there is a concern that the hydrogen gas will generate bubbles one after another, move to the upper part of the transfer line, and accumulate there.

The present invention is a water treatment that can safely treat hydrogen gas generated in an electrodeionization apparatus used in an ultrapure water production apparatus or the like for producing ultrapure water used in a semiconductor manufacturing process or the like. It is useful as a method and water treatment system.

10 water treatment system 1 electrodeionization device 11 anode chamber 12 cathode chamber 121 discharge port 2 hydrogen treatment device 3 area flow meter 4 pressure gauge 5 pressure control valve 6 pressure control means L1 raw water supply line L2 treated water discharge line L3 transfer line W Raw water W1 Treated water (deionized water)
W2 Concentrated water D Hydrogen gas-containing water

Claims (6)

A water treatment method for treating hydrogen gas-containing water in a transfer line that communicates between an electrodeionization device and a hydrogen treatment device that treats hydrogen gas generated by the electrodeionization device,
a bubble observation step of observing whether hydrogen gas bubbles are mixed in the hydrogen gas-containing water;
a pressure measuring step of measuring the pressure in the transfer line;
A pressure adjustment step of adjusting the pressure in the transfer line ,
In the pressure adjustment step, when it is observed that the hydrogen gas bubbles are mixed in the hydrogen gas-containing water in the bubble observation step, the pressure in the transfer line measured in the pressure measurement step adjust the pressure in said transfer line based on
water treatment method. 2. The water treatment method according to claim 1, wherein the setting range of the pressure in said transfer line adjusted in said pressure adjusting step is 0.1 MPa-0.99 MPa. The water treatment method according to claim 1 or 2, wherein the pressure adjustment step is performed immediately before the hydrogen gas-containing water is supplied to the hydrogen treatment device. an electrodeionization device;
a hydrogen treatment device for separating and removing hydrogen gas from hydrogen gas-containing water flowing out from the cathode chamber of the electrodeionization device;
a transfer line communicating with the outlet of the cathode chamber and capable of supplying the hydrogen gas-containing water to the hydrogen treatment device ;
and pressure control means ,
The transfer line is provided with an area flow meter, a pressure gauge and a pressure regulating valve ,
The pressure control means controls the pressure in the transfer line measured by the pressure gauge when it is observed that the hydrogen gas-containing water is mixed with the hydrogen gas bubbles by the area flow meter. to control the pressure regulating valve based on
water treatment system. 5. The water treatment system according to claim 4, wherein the set range of pressure in said transfer line regulated by said pressure regulating valve is 0.1 MPa-0.99 MPa. 6. The water treatment system according to claim 4 or 5, wherein said pressure regulating valve is provided in the immediate vicinity of said hydrogen treatment device.

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