JP5342463B2 - Dissolved hydrogen concentration measuring device and dissolved hydrogen concentration measuring method - Google Patents

Description

  The present invention relates to a dissolved hydrogen concentration measuring apparatus and dissolved hydrogen concentration measuring method in water.

  Conventionally, ultrapure water has been used in various fields such as washing water used in semiconductor device manufacturing processes, cell culture, DNA replication, purified water for medical use, cooling water for nuclear power generation, and solvent for trace analysis. ing. In particular, a lot of ultrapure water is used in the cleaning process for manufacturing electronic components such as electronic devices. In the manufacturing process of the electronic device, the substrate surface is washed with ultrapure water. In this cleaning, not only ultrapure water but also so-called functional water in which nitrogen gas, hydrogen gas, ozone gas or the like is dissolved in ultrapure water to enhance the cleaning effect may be used.

  A general functional water production line may be configured to supply a plurality of functional water according to specifications at each use point. In particular, when supplying hydrogen water produced in such a production line to some use points, a facility for returning surplus hydrogen water that could not be consumed at that use point to the ultra pure water production line may be provided. is there.

  In ultrapure water, the amount of impurities contained is required to be very low. For this reason, it is necessary to control the amount of dissolved gas in water to a small amount. In the case of functional water, it is necessary to control the concentration of the dissolved gas to an appropriate concentration.

  In order to perform such control, it is required to measure an accurate dissolved gas concentration in water. Currently, there are a thermal conductivity type (TCD type) dissolved hydrogen meter and a diaphragm type polaro type hydrogen concentration meter as devices for measuring the dissolved hydrogen concentration in water. The measurement principle of the thermal conductivity type dissolved hydrogen meter is disclosed in Non-Patent Document 1. Non-Patent Document 2 discloses the measurement principle of a diaphragm type polaro oximeter, and the diaphragm type polaro hydrogen concentration meter measures the hydrogen concentration based on the same measurement principle as this oximeter.

  Although the diaphragm-type polaro-type hydrogen concentration meter has the advantage of being able to measure hydrogen to a low concentration, voltage application is required regardless of whether or not the measurement is in progress in order to prevent the deterioration of reactivity and start-up failure at the electrode. ing. In addition, when an oxide is present in water, the electrode deteriorates and may cause a measurement error. For this reason, it has been difficult to stably and continuously measure the hydrogen concentration in water with the diaphragm type polaro hydrogen concentration meter.

  On the other hand, the thermal conductivity type dissolved hydrogen meter does not have the problems of the diaphragm type polaro type hydrogen concentration meter as described above, and has a feature that the dissolved hydrogen concentration can be measured continuously and stably.

"TECHNICAL NEWS", [Catalog] (Orbis Fair (currently Hack), November 1997 “Measurement Principle of Dissolved Oxygen Meter”, [online], [Search July 28, 2009], Internet (URL: http://www.hachultra.jp/index.html)

  The thermal conductivity type dissolved hydrogen meter has a constant relationship between the rate of change in thermal conductivity and the hydrogen concentration due to the change in the thermal conductivity of the probe due to the hydrogen diffused into the measurement probe from the water to be measured. The dissolved hydrogen concentration is calculated by using a certain thing. For this reason, when gas other than hydrogen is dissolved in water, gas other than hydrogen diffuses into the probe together with hydrogen, and changes the thermal conductivity in the probe. Therefore, when a plurality of gases are dissolved in water, measurement errors are caused by the presence of gases other than hydrogen.

  Moreover, in the conventional thermal conductivity type dissolved hydrogen meter, there is a limit to the range of hydrogen concentration that can be measured, and it has been difficult to measure low concentration dissolved hydrogen of several tens of ppb or less.

  The present invention has been made in view of the above problems. That is, the present invention makes it possible to measure an accurate value of the hydrogen concentration using a conventional thermal conductivity detector even when a plurality of gases are dissolved in water, and whether or not measurement is in progress. It is an object of the present invention to provide an apparatus and a method for measuring dissolved hydrogen concentration in water, which can solve the management problems of a diaphragm type polaro hydrogen concentration meter that requires voltage application.

  When measuring the dissolved hydrogen concentration in the measured water using the thermal conductivity detector, if there is a dissolved gas other than hydrogen in the measured water, the thermal conductivity detector The rate of change in thermal conductivity due to gas is measured, and the dissolved hydrogen concentration is calculated in relation to the rate of change.

  For example, with respect to water to be measured in which hydrogen and nitrogen are dissolved, a case where the dissolved hydrogen concentration is measured using a thermal conductivity type dissolved hydrogen meter will be described as an example. In this case, the thermal conductivity of nitrogen is 0.0243 (W / (m · K)) at 0 ° C. and 0.0312 (W / (m · K)) at 100 ° C., whereas the heat of hydrogen The conductivity is 0.1684 (W / (m · K)) at 0 ° C. and 0.216 (W / (m · K)) at 100 ° C. Thus, the thermal conductivity of hydrogen shows a value different from the thermal conductivity of nitrogen (Science Chronology 1982 edition). In other words, when measuring the dissolved hydrogen concentration in the measured water, if the measured water contains dissolved nitrogen, the measured value by the thermal conductivity type dissolved hydrogen meter will be higher than the actual dissolved hydrogen concentration. Increase by the minute.

  From this, the present inventors removed the dissolved hydrogen in the water to be measured, thereby changing the thermal conductivity due to the dissolved gas in the water before removing the dissolved hydrogen and the thermal conductivity due to the dissolved gas in the water after removing the dissolved hydrogen. When hydrogen and other gases coexist in the water to be measured by a simple method by outputting the result of measuring the change in temperature with a thermal conductivity detector and calculating the dissolved hydrogen concentration from the difference between the measured values. Even so, the inventors have found a method that can accurately measure the dissolved hydrogen concentration and have reached the following invention.

That is, the flow path,
A hydrogen removal unit for removing dissolved hydrogen in water in the flow path;
One or more thermal conductivity detectors that detect changes in thermal conductivity due to dissolved gas in the water and convert them into electrical signals;
An electrical signal obtained by converting a change in thermal conductivity due to dissolved gas in water before passing through the hydrogen removal unit and a change in thermal conductivity due to dissolved gas in water after passing through the hydrogen removal unit are converted into heat. A dissolved hydrogen concentration calculating means for calculating a dissolved hydrogen concentration in the water based on an electrical signal converted by a conductivity detector;
The present invention relates to a device for measuring dissolved hydrogen concentration.

In addition, a hydrogen removal process for removing dissolved hydrogen in water,
A first measurement step of measuring a change in thermal conductivity due to dissolved gas in the water before the hydrogen removal step;
A second measurement step of measuring a change in thermal conductivity due to dissolved gas in the water after the hydrogen removal step;
A dissolved hydrogen concentration calculating step of calculating a dissolved hydrogen concentration in the water based on a measurement result of a change in thermal conductivity in the first measuring step and the second measuring step;
The present invention relates to a method for measuring dissolved hydrogen concentration.

  Even when hydrogen and other gases coexist in the water to be measured, the accurate value of the concentration of hydrogen dissolved in the water can be measured using the thermal conductivity detector. Moreover, while solving the management problem of the diaphragm-type polaro hydrogen concentration meter, it is possible to measure the dissolved hydrogen concentration as low as the diaphragm-type polaro hydrogen concentration meter.

It is a figure explaining the measurement principle of dissolved hydrogen concentration. It is a figure explaining the measuring method of the conventional dissolved gas concentration. It is a figure explaining the measuring method of dissolved hydrogen concentration. It is a figure which shows an example of a dissolved hydrogen concentration measuring apparatus. It is a figure which shows an example of a dissolved hydrogen concentration measuring apparatus. It is a figure which shows an example of a dissolved hydrogen concentration measuring apparatus. It is a figure which shows an example of a dissolved hydrogen concentration measuring apparatus. It is a figure which shows an example of a dissolved hydrogen concentration measuring apparatus. It is a figure which shows an example of a dissolved hydrogen concentration measuring apparatus. It is a figure explaining the experimental process of the reference example 1, Example 1, and Example 2. FIG. 10 is a graph showing the results of Reference Example 1. 3 is a graph showing the results of Example 1. 10 is a graph showing the results of Example 2. 10 is a graph showing the results of Example 2.

(Measurement method of dissolved hydrogen concentration)
FIG. 1 is a diagram showing the measurement principle of the dissolved hydrogen concentration according to the present invention. As shown in FIG. 1, the gas concentration in the water to be measured before passing through the hydrogen removal unit (before the hydrogen removal step) is measured as the dissolved gas concentration (first measurement), and then passed through the hydrogen removal unit. The gas concentration in the water to be measured (after the hydrogen removal step) is measured as the dissolved gas concentration (second measurement). Then, ΔDG = (dissolved gas concentration DG ₁ by the first measurement) − (dissolved gas concentration DG ₂ by the second measurement) is calculated, and the dissolved hydrogen concentration is calculated from the value of ΔDG. I do.

  In the measurement of the dissolved gas concentration in the water to be measured, first, using a device having a thermal conductivity detector that combines an element (thermal conductivity detection element = TCD) that converts to an electrical signal and a semipermeable membrane, Changes in thermal conductivity due to dissolved gases are measured.

  FIG. 2 is a diagram showing a general measurement principle of dissolved gas concentration. First, the valve 124 is opened, purge gas (carbon dioxide gas, argon gas, etc.) of the purge gas supply source 120 is supplied from the purge gas supply line 122 to the measurement chamber 110, and the measurement chamber 110 is filled with the purge gas. In this state, the TCD 112 measures the thermal conductivity of the purge gas and outputs the measured value to the amplifier 130 as a signal. At this time, since the inside of the measurement chamber 110 is filled with a specific purge gas, the signal output from the TCD 112 to the amplifier 130 is stable with the thermal conductivity of the purge gas. The signal output from the TCD 112 is sent to the controller 132 via the amplifier 130. When the signal output from the TCD 112 is stable, that is, when the purge in the measurement chamber 110 is completed, the controller 132 closes the valve 124 and stops the supply of the purge gas to the measurement chamber 110.

  When the water to be measured is supplied to the flow channel 1 in a state where the measurement chamber 110 is filled with the purge gas, the dissolved gas in the water to be measured passes through the semipermeable membrane 104 and moves to the measurement chamber 110. When the dissolved gas moves from the flow path 1 to the measurement chamber 110, the purge gas in the measurement chamber 110 is discharged to the gas discharge line 114 by the transferred dissolved gas. The TCD 112 measures the thermal conductivity according to the dissolved gas concentration in the measurement chamber 110 and outputs the measured value as a signal to the controller 132 via the amplifier 130. The speed at which the purge gas in the measurement chamber 110 is replaced with the dissolved gas is proportional to the partial pressure of the dissolved gas in the flow path 1. Therefore, the controller 132 obtains the partial pressure of the dissolved gas in the flow path 1 from the change rate of the thermal conductivity detected by the TCD 112, and the dissolved gas concentration in the measured water is based on the obtained partial pressure of the dissolved gas. Calculated.

Therefore, in measuring the dissolved hydrogen concentration in the water to be measured in the present invention, the one having a thermal conductivity detector combining TCD and a semipermeable membrane is used to measure the thermal conductivity of the dissolved gas in the water to be measured. It suffices if the change can be measured. For example, when measuring the dissolved hydrogen concentration using a nitrogen concentration calculator, the electrical signal converted by the thermal conductivity detector is output as the nitrogen concentration in water. In other words, the thermal conductivity detector and the nitrogen concentration calculation unit (hereinafter, the thermal conductivity detector and the nitrogen concentration calculation unit may be referred to as “thermal conductivity type dissolved nitrogen meter”) in the first measurement. The dissolved nitrogen concentration in the water before passing through the removal unit is measured, and the dissolved nitrogen concentration in the water after passing through the hydrogen removal unit is measured in the second measurement. Then, the calculation unit calculates ΔDN represented by ΔDN = (dissolved nitrogen concentration DN ₁ in the first measurement) − (dissolved nitrogen concentration DN ₂ in the second measurement), and the dissolved hydrogen concentration from the value of ΔDN. The process which calculates is performed. In addition, even if dissolved hydrogen and gas other than dissolved hydrogen are dissolved in the water to be measured, in order to selectively remove hydrogen in the dissolved hydrogen removal unit, other than hydrogen removed in the dissolved hydrogen removal unit Since there is almost no change in the amount of dissolved gas, it does not affect the calculation of ΔDN.

  Thus, when measuring using the existing thermal conductivity type dissolved nitrogen meter etc., the signal from a thermal conductivity detector is converted into dissolved nitrogen concentration, and is output. For this reason, a calibration curve representing the relationship between dissolved hydrogen concentration and dissolved nitrogen concentration created based on the dissolved nitrogen concentration obtained by measuring with a thermal conductivity type dissolved nitrogen meter using sample water with a known dissolved hydrogen concentration Can be used to convert the dissolved nitrogen concentration to the dissolved hydrogen concentration.

  Further, a series of calculations for calculating the dissolved hydrogen concentration by converting the electrical signal from the thermal conductivity detector into ΔDN can be performed by a program.

  In addition to the nitrogen concentration calculation unit, an oxygen concentration calculation unit that converts the electrical signal converted by the thermal conductivity detector into dissolved oxygen concentration in water and a hydrogen concentration calculation unit that converts into dissolved hydrogen concentration in water. May be used.

For example, in the measurement of the dissolved hydrogen concentration using the oxygen concentration calculation unit, the dissolved oxygen concentrations DO ₁ and DO ₂ in the first and second measurements are measured by the thermal conductivity detector and the oxygen concentration calculation unit. Thereafter, the calculation unit calculates ΔDO = DO ₁ −DO ₂ and performs a process of calculating the dissolved hydrogen concentration from the value of ΔDO.

In the measurement of the dissolved hydrogen concentration using the hydrogen concentration calculation unit, the dissolved hydrogen concentration is calculated from the dissolved hydrogen concentrations DH ₁ and DH ₂ in the first and second measurements obtained by the thermal conductivity detector and the hydrogen concentration calculation unit. A concentration ΔDH = DH ₁ −DH ₂ is calculated, and a process of calculating the dissolved hydrogen concentration from the value of ΔDH is performed.

  By providing the hydrogen removal unit, it is possible to eliminate the influence of the coexisting gas that has caused the error in the measurement using the conventional thermal conductivity detector, so that an accurate value of the dissolved hydrogen concentration can be obtained. In addition, since the dissolved hydrogen concentration is calculated from the difference between the measured values before and after passing through the hydrogen removal section, it is possible to measure a low concentration of hydrogen that is equivalent to the lower limit of quantification of the diaphragm type polaro hydrogen concentration meter.

  As the water to be measured, any water that is the target for measuring the dissolved hydrogen concentration can be measured, but it is required to manage the dissolved hydrogen concentration with a more accurate value, and a conventional thermal conductivity dissolved hydrogen meter is required. The present invention can be suitably used for pure water such as ultrapure water, which is difficult to obtain by a normal measurement method using water, or hydrogen water in which hydrogen gas is dissolved in pure water. For example, in the production process of ultrapure water as shown in FIG. 3 or hydrogen water which is a kind of functional water, when measuring the dissolved hydrogen concentration, when measuring the dissolved hydrogen in the produced ultrapure water, The flow path is branched from the part (a) of FIG. 3 and connected to a dissolved hydrogen concentration measuring device as shown in FIGS. Moreover, what is necessary is just to connect a dissolved hydrogen concentration measuring apparatus similarly to the (b) part of FIG. 3, when measuring the dissolved hydrogen concentration in hydrogen water.

(Dissolved hydrogen concentration measuring device)
4a to 4e are diagrams illustrating an example of a dissolved hydrogen concentration measurement apparatus in a case where a dissolved hydrogen concentration is calculated by measuring a dissolved nitrogen concentration in water to be measured using a thermal conductivity detector. In FIG. 4a which is one embodiment, the dissolved hydrogen concentration measurement apparatus includes a flow path 1, a hydrogen removal unit 17, a first thermal conductivity detector 15a, a second thermal conductivity detector 15b, and a first nitrogen concentration. A calculation unit 13, a second nitrogen concentration calculation unit 14, and a calculation unit 18 are included. This flow path 1 is connected to the main pipe 61 of the manufacturing process of ultrapure water or functional water. The flow path 1 includes a first thermal conductivity detector 15a, a hydrogen removal unit 17, and a second thermal conductivity detector 15b from the upstream side toward the downstream side, that is, in the direction of the arrow. Is provided. The first thermal conductivity detector 15a converts a change in thermal conductivity due to dissolved gas in the water before passing through the hydrogen removing unit 17 into an electrical signal. Then, the first nitrogen concentration calculation unit 13 connected to the first thermal conductivity detector 15a calculates the dissolved nitrogen concentration based on the electrical signal from the first thermal conductivity detector 15a. The second thermal conductivity detector 15b converts a change in thermal conductivity caused by dissolved gas in the water after passing through the hydrogen removing unit 17 into an electrical signal. Then, the second nitrogen concentration calculation unit 14 connected to the second thermal conductivity detector 15b calculates the dissolved nitrogen concentration based on the electric signal from the second thermal conductivity detector 15b. Then, the calculation unit 18 calculates the dissolved hydrogen concentration from the difference between the dissolved nitrogen concentrations calculated by the first and second nitrogen concentration calculation units 13 and 14.

  Moreover, in FIG. 4b which is an example of other embodiment, the change of each thermal conductivity detected with the 1st thermal conductivity detector and the 2nd thermal conductivity detector is converted into an electric signal, It is connected so that the dissolved nitrogen concentration can be calculated by one nitrogen concentration calculation unit 13. In this case, for example, first, the change in thermal conductivity detected by the first thermal conductivity detector 15a is converted into an electric signal, and the dissolved nitrogen concentration in the water before passing through the hydrogen removing unit 17 is converted into the nitrogen concentration calculating unit 13. And the value is stored in the nitrogen concentration calculator 13 or the calculator 18. Next, the change in thermal conductivity detected by the second thermal conductivity detector 15b is converted into an electrical signal, and the dissolved nitrogen concentration in the water after passing through the hydrogen removing unit 17 is calculated by the nitrogen concentration calculating unit 13, The value is stored in the nitrogen concentration calculator 13 or the calculator 18. And in the calculating part 18, a dissolved hydrogen concentration is calculated from the difference of each memorize | stored dissolved nitrogen concentration.

  In the embodiment of FIGS. 4a and 4b, the first thermal conductivity detector 15a and the second thermal conductivity detector 15b are directly connected to the flow path 1, but an example of another embodiment is shown. As shown in FIGS. 4c and 4d, each branch pipe may be branched, and each thermal conductivity detector may be provided in the branch pipe.

  FIG. 4 e, which is an example of another embodiment, calculates the dissolved nitrogen concentration of the water to be measured before passing through the hydrogen removing unit 17 and the water to be measured after passing through one thermal conductivity detector and one nitrogen concentration calculation. It is the form in the case of measuring by a part. As shown in FIG. 4e, the branch pipe 41 is branched to the upstream side of the hydrogen removing unit 17 in the flow path 1 via the valve 54, and similarly, the downstream side of the hydrogen removing unit 17 in the flow path 1 is connected to the downstream side via the valve 55 The branch pipe 42 is branched. The branch pipes 41 and 42 are joined, and the thermal conductivity detector 15c is connected to the downstream side of the joining point. When the valves 51 and 54 are opened and the valve 55 is closed, the thermal conductivity detector 15c can detect a change in thermal conductivity before passing through the hydrogen removing unit 17. Further, when the valves 51 and 55 are opened and the valve 54 is closed, a change in thermal conductivity after passing through the hydrogen removing unit 17 can be detected.

  Although the example of the embodiment has been described above, when the nitrogen concentration calculation unit is used, the dissolved nitrogen concentration before and after passing through the dissolved hydrogen removal unit 17 can be calculated using the nitrogen concentration calculation unit. As long as a calculation unit that converts the calculated difference in dissolved nitrogen concentration into a dissolved hydrogen concentration is provided, the configuration of the branch pipe and valve, the configuration of the thermal conductivity detector, and the nitrogen concentration calculation unit are not particularly limited. For example, the water after passing through the hydrogen removing unit or the water of the branch pipe branched from the flow path can be returned to the main pipe. In FIGS. 4c and 4d, the first and second thermal conductivity detectors pass. Each branch pipe can be joined later. In addition, when the branch pipes are joined, a check valve can be provided upstream from the junction of the respective branch pipes to prevent backflow of the water to be measured.

  In addition, the thermal conductivity detector and the nitrogen concentration calculator can use existing thermal conductivity dissolved nitrogen meters. Examples thereof include model-3621 manufactured by Orbis Fair.

  The hydrogen removing unit 17 is not particularly limited as long as it can selectively remove dissolved hydrogen in the water to be measured. The hydrogen removing unit 17 is preferably a column filled with a filler containing at least one of a hydrogen storage metal and a hydrogen storage alloy. As the filler, for example, a metal, alloy grain, hydrogen storage metal or hydrogen storage alloy supported on a carrier is preferable. Examples of the carrier include resin, alumina, activated carbon, metal, and zeolite. Further, the shape of the filler is not particularly limited, and examples thereof include a pellet shape, a spherical shape, and a granular shape. The hydrogen storage metal or hydrogen storage alloy preferably contains a platinum group element selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, and platinum.

  The calculation unit realizes a function of calculating a dissolved hydrogen concentration from a difference in dissolved nitrogen concentration in the measured water before and after passing through the hydrogen removing unit, which is measured by a gas concentration calculating unit such as a nitrogen concentration calculating unit. Any hardware may be used as long as it is configured, for example, hardware that can read a computer program and execute a corresponding processing operation. Specifically, hardware including a CPU (Central Processing Unit) as a main body and various devices such as a ROM, a RAM (Random Access Memory), and an I / F (Interface) unit may be connected thereto. In addition, the processor of the calculation unit and the gas concentration calculation unit do not have to be independent of each other, and is formed as one dissolved hydrogen concentration calculation unit, and a part of each other may overlap. Is possible. For example, the electrical signal of the change rate of the thermal conductivity detected by the thermal conductivity detector is directly input to the dissolved hydrogen concentration calculating means, and the ΔDN value calculated by the dissolved hydrogen concentration calculating means is converted to the dissolved hydrogen concentration. Processing can also be performed. In addition, even if ΔDN is not calculated, the rate of change in the thermal conductivity of the dissolved gas and the dissolved gas concentration are in a proportional relationship, so that the electrical signal from each thermal conductivity detector before and after passing through the hydrogen removal unit The dissolved hydrogen concentration may be obtained directly from the difference.

(Hydrogen removal function recovery means)
The dissolved hydrogen concentration measuring device preferably has a hydrogen removal function recovery means that recovers the hydrogen removal function of the hydrogen removal unit. The hydrogen removal function recovery means may be any method as long as the hydrogen removal function of the hydrogen removal section can be recovered, but it has oxygen addition means for adding oxygen to the water to be measured and passing the oxygen through the hydrogen removal section. preferable. As the dissolved hydrogen concentration measuring device is used, the hydrogen removal unit gradually becomes saturated with the incorporated hydrogen. Then, after the hydrogen occlusion capacity of the hydrogen removal unit becomes saturated, the hydrogen removal unit cannot remove dissolved hydrogen in the water to be measured. Therefore, by allowing oxygen to pass through, as represented by the following formula (A), the hydrogen taken into the hydrogen removal unit reacts with oxygen in water to be removed as water.
2H ₂ + O ₂ → 2H ₂ O (A)
As a result, the hydrogen removing unit can remove hydrogen in water stably and almost completely for a long time.

  FIG. 5 shows an example of a dissolved hydrogen concentration measuring apparatus provided with oxygen adding means. In FIG. 5, the oxygen addition means 28 includes a gas dissolving film 19, a valve 56 and a valve 57. A water supply unit 21 that supplies water for dissolving oxygen gas is connected to the valve 56, and an oxygen supply unit 20 that supplies oxygen gas is connected to the valve 57. And it is connected to the upstream side of the hydrogen removal part 17 of the flow path 1. Since the gas-dissolving film 19 allows gas to permeate but does not allow liquid to permeate, oxygen gas is supplied into the measured water through the gas-dissolving film. As a result, oxygen is taken into the hydrogen removal unit using the water to be measured as a medium.

  The oxygen addition means may be provided at a position where oxygen reaches the hydrogen removal unit 17, but when measuring the dissolved hydrogen concentration while adding oxygen, the thermal conductivity detector before passing through the hydrogen removal unit Or it is preferable to provide between a branch pipe and a hydrogen removal part. This makes it possible to measure the dissolved hydrogen concentration more accurately. If the oxygen addition means is provided on the upstream side of the thermal conductivity detector or branch pipe before passing through the hydrogen removal unit, the first measurement before passing through the hydrogen removal unit shows the thermal conductivity containing oxygen. Detect changes. However, since the added oxygen is consumed in the hydrogen removal unit, the second measurement after passing through the hydrogen removal unit detects a change in thermal conductivity not containing oxygen. Since the dissolved hydrogen concentration is calculated from the difference in change in thermal conductivity detected in the first measurement and the second measurement, an error occurs in the measurement result of the dissolved hydrogen concentration by the amount of added oxygen. Moreover, an oxygen addition means can also be provided directly in the hydrogen removal unit. Furthermore, when oxygen measuring means is provided on the downstream side of the hydrogen removing unit and water to be measured is not flowing, water containing oxygen is passed through the hydrogen removing unit from the direction opposite to the flow of the water to be measured. There is also a method of watering.

  Further, the oxygen addition means only needs to be configured to allow oxygen to pass through the hydrogen removal unit 17. For example, water may be supplied from the main pipe 61 instead of the water supply unit 21. In addition to this, there is a method in which oxygen gas is directly added to the hydrogen removing portion through a gas dissolution film.

  It is preferable to add oxygen so that the dissolved oxygen (DO) in the measured water is 8.5 or more in terms of mass ratio (DO / DH) with respect to the dissolved hydrogen (DH) in the measured water. When DO / DH is 8.5 or more, the hydrogen removal rate is very high, and the hydrogen removal unit can be used efficiently. Therefore, for example, when measuring the dissolved hydrogen concentration using the present dissolved hydrogen concentration measuring apparatus, the hydrogen removal capability of the hydrogen removal unit is maximized by adding oxygen of DO / DH 8.5 or more to the hydrogen removal unit in advance. And the measurement range can be widened.

(Reference Example 1)
The thermal conductivity detector cannot distinguish the type of gas dissolved in water, and measures the change in thermal conductivity with all gases dissolved in water as one dissolved gas. Therefore, in this Reference Example 1, when measuring the dissolved nitrogen concentration in water using a thermal conductivity type dissolved nitrogen meter, when dissolved hydrogen is contained in water, the measurement result is affected by dissolved hydrogen. confirmed.

  A predetermined amount of hydrogen is added to the water to be measured whose dissolved nitrogen concentration is stabilized at 0.9 to 1.3 ppm, and the dissolved nitrogen concentration at that time is measured by a thermal conductivity type dissolved nitrogen meter (model-3621 manufactured by Orbis Fair). Nitrogen measurement unit). The measurement was performed with an apparatus as shown in the experimental flow of FIG. Ultrapure water having a known dissolved nitrogen concentration (dissolved nitrogen concentration: 0.9 to 1.3 ppm) was flowed in the flow path 1 in the direction of the arrow. The ultrapure water in the flow channel 1 has a hydrogen concentration of 2.7 ppb, 5.4 ppb, 8.0 ppb, 10.7 ppb, 21.4 ppb, or 35.7 ppb in the flow channel through the gas dissolution membrane. Hydrogen was added from the hydrogen addition section 27.

  Although not used in the present reference example 1, the flow path 1 has an oxygen addition means 28 that can add a predetermined amount of oxygen through a gas dissolving film. The hydrogen removing unit 17 is a column filled with Pd-supporting resin. By providing this column in the middle of the flow path 1, the water to be measured flows through the column.

The specifications of the hydrogen removal unit 17 were as follows.
○ Pd-supported resin: OH form 960 [mg / LR]
O Production method of Pd-supported resin: Chloride Pd acid was adsorbed on a gel-type strongly basic anion exchange resin. Thereafter, this was reduced with a reducing agent to deposit metal Pd. Next, the resin was purified to OH form, and then treated to prevent TOC elution.
○ Filling amount of Pd-supported resin: 150 mL
○ Type of column: S-300 (manufactured by Shodate Plastic Co., Ltd.)
○ Standard value of outer diameter and inner diameter of S-300 column: 34φ × 26φ × 337mm
○ Column height: 30cm
○ Water flow rate to the column: SV = 400 [/ h]
(SV represents the amount [L] that allows water to flow for 1 hour with respect to the unit volume [L] of the resin).

  Further, a branch pipe 29 is provided on the upstream side of the hydrogen removing unit 17 of the flow path 1, and a branch pipe 30 is provided on the downstream side, and these are connected to the three-way valve 28. The three-way valve 28 was further connected to a diaphragm-type polaro-type hydrogen concentration meter (manufactured by Toa DKK; DHDI-1) 31 and an oxygen / nitrogen concentration meter (manufactured by Orbis Fair; model-3621) 32 via a pipe. The oxygen / nitrogen concentration meter 32 is composed of a diaphragm type polaro oxygen concentration meter and a thermal conductivity type dissolved nitrogen meter, and when nitrogen and oxygen coexist in water, The dissolved oxygen content is automatically corrected.

  The relationship between the measured value DN of the thermal conductivity type dissolved nitrogen meter with respect to each dissolved hydrogen concentration DH is shown in FIG.

  As described above, since the nitrogen concentration in the water to be measured is substantially constant at 0.9 to 1.3 ppm, the display value of the thermal conductivity type dissolved nitrogen meter is originally 0.9 to 1.3 ppm. Should be. However, according to FIG. 7, it can be seen that the displayed value of the dissolved nitrogen meter increases as the dissolved hydrogen concentration in the measured water increases. Therefore, it can be seen that there is a certain relationship between the dissolved hydrogen concentration in the water to be measured and the displayed value of the dissolved nitrogen meter. Further, when the dissolved hydrogen concentration increases by 1 ppb, the displayed value of the dissolved nitrogen meter rises by 0.5 ppm, so that it can be understood that the presence of dissolved hydrogen greatly affects the measurement of the dissolved nitrogen concentration.

Example 1
According to the experimental flow shown in FIG. 6, a predetermined amount of hydrogen is added from the hydrogen addition section, the dissolved hydrogen concentration before passing through the hydrogen removal section (DH; measured by a diaphragm type polaro type hydrogen concentration meter), and before and after passing through the hydrogen removal section. The difference (ΔDN) in the later dissolved nitrogen concentration was measured. The experimental conditions are the same as in Reference Example 1 except for the added hydrogen concentration. The measurement results are shown in Table 1 and FIG. “■” in FIG. 8 represents ΔDN with respect to a predetermined DH concentration.

  From the results of Table 1 and FIG. 8, DH and ΔDN show an excellent linear relationship. Therefore, for example, by creating a calibration curve based on ΔDN when two sample waters having a known dissolved hydrogen concentration are measured by the dissolved hydrogen concentration measuring apparatus of the present embodiment, the dissolved hydrogen concentration is calculated from the ΔDN of the water to be measured. It can be seen that it can be obtained. In addition, this linear relationship is recognized when DH is in the range of 5.3 to 52 ppb. With the dissolved hydrogen concentration measuring apparatus and the dissolved hydrogen concentration measuring method of this example, the dissolved hydrogen concentration is measured to a low concentration of at least 5.3 ppb. I understand that I can do it.

  From the above, it was confirmed that the dissolved hydrogen concentration measuring apparatus and the dissolved hydrogen concentration measuring method of this example can measure the hydrogen concentration to a low concentration using a thermal conductivity type dissolved nitrogen meter.

(Example 2)
In this example, ΔDN with respect to DH was measured according to the experimental flow shown in FIG. 6 under the same conditions as in Example 1 except that a predetermined amount of oxygen was added from the oxygen addition means.

  The measurement results are shown in Table 2 and FIG. “□” in FIG. 9 represents a case where oxygen was added from the oxygen addition means, and “♦” represents a case where oxygen was not added from the oxygen addition means.

  From the results of Table 2 and FIG. 9, when oxygen is added (□), ΔDN and DH show an excellent linear relationship in the range of DH = 54 to 94 ppb, and the dissolved hydrogen concentration measuring apparatus of this example and It can be seen that the dissolved hydrogen concentration in water can be measured by the method for measuring the dissolved hydrogen concentration.

  In addition, when oxygen is not added (♦), a linear relationship between ΔDN and DH is recognized up to DH = 52 ppb, but when DH = 102 ppb, there is no linear relationship with data below DH = 52 ppb. . The reason for this is considered that a large amount of hydrogen is occluded in the hydrogen removal part, and the hydrogen removal part cannot completely remove dissolved hydrogen in water.

  As described above, in the dissolved hydrogen concentration measuring apparatus and the dissolved hydrogen concentration measuring method of the present embodiment, the dissolved hydrogen concentration in the ultrapure water using the thermal conductivity type dissolved nitrogen meter is obtained by adding oxygen by the oxygen addition means. We were able to confirm that the range in which measurement was possible could be expanded.

Further, in the experiment of Example 2, the mass ratio (DO / DH) of dissolved oxygen and dissolved hydrogen in the water to be measured when oxygen is added and not added, and the dissolved hydrogen removal rate of the hydrogen removal unit are measured. did. The measurement results are shown in Table 3 and FIG.
The dissolved hydrogen removal rate was calculated from the following equation as the dissolved hydrogen concentration DH _{1 in the} measured water sampled from the branch pipe 29 in FIG. 6 and the dissolved hydrogen concentration DH _{2 in the} measured water sampled from the branch pipe 30.
Dissolved hydrogen removal rate = (DH ₁ −DH ₂ ) / DH ₁ × 100

From the results of Table 3 and FIG. 10, it can be seen that DO / DH is 8.5 or more and the dissolved hydrogen removal rate is very high.

  Therefore, by adding oxygen of DO / DH 8.5 or more to the hydrogen removal unit in advance, the hydrogen removal capability of the hydrogen removal unit can be maximized and the measurement range can be widened.

DESCRIPTION OF SYMBOLS 1 Flow path 13 1st nitrogen concentration calculation part 14 2nd nitrogen concentration calculation part 15a 1st thermal conductivity detector 15b 2nd thermal conductivity detector 15c Thermal conductivity detector 17 Hydrogen removal part 18 Calculation part 19 Gas dissolving film 20 Oxygen supply part 27 Hydrogen addition part 28 Three-way valve 29, 30 Branch pipe 31 Diaphragm type polaro type hydrogen concentration meter 32 Oxygen / nitrogen concentration meter 41, 42 Branch pipe 51, 54, 55 Valve 61 Main pipe 104 Half Permeable membrane 110 Measurement chamber 112 Thermal conductivity detection element 114 Gas discharge line 120 Purge gas supply source 122 Purge gas supply line 130 Amplifier 132 Controller

Claims (12)

A flow path;
A hydrogen removal unit for removing dissolved hydrogen in water in the flow path;
One or more thermal conductivity detectors that detect changes in thermal conductivity due to dissolved gas in the water and convert them into electrical signals;
An electrical signal obtained by converting a change in thermal conductivity due to dissolved gas in water before passing through the hydrogen removal unit and a change in thermal conductivity due to dissolved gas in water after passing through the hydrogen removal unit are converted into heat. A dissolved hydrogen concentration calculating means for calculating a dissolved hydrogen concentration in the water based on an electrical signal converted by a conductivity detector;
A device for measuring dissolved hydrogen concentration. The dissolved hydrogen concentration calculating means includes:
The change in thermal conductivity due to dissolved gas in the water before passing through the hydrogen removal unit is converted from the electrical signal converted by the thermal conductivity detector to the dissolved gas concentration in water before passing through the hydrogen removal unit,
The change in thermal conductivity due to dissolved gas in the water after passing through the hydrogen removal unit is converted from the electrical signal converted by the thermal conductivity detector to the dissolved gas concentration in water after passing through the hydrogen removal unit,
It is configured to convert the difference between the dissolved gas concentration in water before passing through the hydrogen removal unit and the dissolved gas concentration in water after passing through the hydrogen removal unit into a dissolved hydrogen concentration,
The dissolved hydrogen concentration measuring apparatus according to claim 1. The dissolved hydrogen concentration calculating means includes:
One or more gas concentration calculators for converting the electrical signal converted by the thermal conductivity detector into dissolved gas concentration in water;
A calculation unit that converts the difference between the dissolved gas concentration in the water before passing through the hydrogen removal unit and the dissolved gas concentration in the water after passing through the hydrogen removal unit converted by the gas concentration calculation unit into a dissolved hydrogen concentration,
The dissolved hydrogen concentration measuring device according to claim 1 or 2, comprising: The dissolved hydrogen concentration calculating means includes:
One or more nitrogen concentration calculators for converting the electrical signal converted by the thermal conductivity detector into dissolved nitrogen concentration in water;
A calculation unit that converts the difference between the dissolved nitrogen concentration in the water before passing through the hydrogen removal unit converted by the nitrogen concentration calculation unit and the dissolved nitrogen concentration in the water after passing through the hydrogen removal unit into a dissolved hydrogen concentration;
The dissolved hydrogen concentration measuring apparatus according to claim 1, comprising:   The said hydrogen removal part is a dissolved hydrogen concentration measuring apparatus in any one of Claims 1-4 containing the filler containing at least one of the hydrogen storage metal and the hydrogen storage alloy.   The dissolved hydrogen concentration measuring apparatus according to claim 1, further comprising a hydrogen removal function recovery unit that recovers a hydrogen removal function of the hydrogen removal unit.   The dissolved hydrogen concentration measuring apparatus according to claim 6, wherein the hydrogen removal function recovery means is configured to add oxygen to the water and pass the oxygen through the hydrogen removal unit. A hydrogen removal step to remove dissolved hydrogen in the water;
A first measurement step of measuring a change in thermal conductivity due to dissolved gas in the water before the hydrogen removal step;
A second measurement step of measuring a change in thermal conductivity due to dissolved gas in the water after the hydrogen removal step;
A dissolved hydrogen concentration calculating step of calculating a dissolved hydrogen concentration in the water based on a measurement result of a change in thermal conductivity in the first measuring step and the second measuring step;
A method for measuring dissolved hydrogen concentration. The dissolved hydrogen concentration calculating step includes:
A change in thermal conductivity due to dissolved gas in the water before the hydrogen removal step measured in the first measurement step is converted into a dissolved gas concentration in water;
Converting the change in thermal conductivity due to the dissolved gas in the water after the hydrogen removal step measured in the second measurement step into a dissolved gas concentration in the water;
Calculating the dissolved hydrogen concentration from the difference in dissolved gas concentration between the first measurement step and the second measurement step;
It is a process, The measuring method of the dissolved hydrogen concentration of Claim 8. The dissolved hydrogen concentration calculating step includes:
A change in thermal conductivity due to dissolved gas in the water before the hydrogen removal step measured in the first measurement step is converted into a dissolved nitrogen concentration in water;
Converting the change in thermal conductivity due to the dissolved gas in the water after the hydrogen removal step measured in the second measurement step into a dissolved nitrogen concentration in the water;
Calculate the dissolved hydrogen concentration from the difference between the dissolved nitrogen concentration in the first measurement step and the second measurement step,
The method for measuring a dissolved hydrogen concentration according to claim 8 or 9, which is a step. The hydrogen removal step includes
Allowing the water to pass through a hydrogen removal portion including a filler containing at least one of a hydrogen storage metal and a hydrogen storage alloy;
It is a process, The measuring method of the dissolved hydrogen concentration in any one of Claims 8-10.   The dissolved hydrogen according to claim 11, further comprising an oxygen addition step for adding oxygen to water and passing the oxygen through the hydrogen removal unit to remove hydrogen taken into the hydrogen removal unit from the hydrogen removal unit. Concentration measurement method.

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