Hydrogen peroxide concentration measurement system and hydrogen peroxide concentration measurement method

Abstract

To provide a hydrogen peroxide concentration measurement system capable of reducing a time until stabilization of a measurement value after switching a measurement system, and having a reduced consumption of a water specimen.SOLUTION: A water specimen sampling tube 3 is branched into a first path 4 and a second path 5, and the first path 4 can be switched to a dissolved oxygen concentration measurement channel 7 and a first circulation channel 9. Also, the second path 5 can be switched to a hydrogen peroxide decomposition channel 11 and a second circulation channel 13. Further, the dissolved oxygen concentration measurement channel 7 can be switched to a discharge tube 14 and the second circulation channel 13. Further, the hydrogen peroxide decomposition channel 11 can be switched to the discharge tube 14 and the first circulation channel 9. Accordingly, the switching allows a water spacemen W to continuously circulate from a dissolved oxygen concentration meter 8 to a catalyst resin column 12 or to continuously circulate from the catalyst resin column 12 to the dissolved oxygen concentration meter 8.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a measurement system and a measurement method for measuring the concentration of trace amounts of hydrogen peroxide in sample water such as pure water or ultrapure water. [Background technology]

[0002] Conventionally, ultrapure water used in the semiconductor and other electronics industries is produced by treating raw water in an ultrapure water production system that is composed of a pretreatment system, a primary pure water production apparatus, and a subsystem that treats the primary pure water (secondary pure water production apparatus).

[0003] In the manufacturing process of ultrapure water for the electronics industry, hydrogen peroxide is a very important factor in the ultrapure water supply management. For example, copper, a typical wiring metal, corrodes with hydrogen peroxide at a concentration of several μg / L, affecting the surface flatness and dissolving, which affects the electrical characteristics of semiconductor products and reduces yields. On the other hand, it is known that hydrogen peroxide is generated in ultraviolet irradiation equipment installed in pure water and ultrapure water manufacturing facilities for the purpose of decomposing organic matter. For this reason, it is necessary to analyze (monitor) the hydrogen peroxide concentration.

[0004] Conventionally, methods using test paper or test reagents, colorimetry, redox titration, etc. are commonly known as methods for analyzing the concentration of hydrogen peroxide, but in order to analyze the concentration of hydrogen peroxide in pure water or ultrapure water manufacturing facilities, microanalysis with analysis values ​​at the μG / L level is required. Of the various analytical methods mentioned above, it is difficult to measure with analysis values ​​at the μG / L level using the methods using test paper or test reagents.

[0005] In addition, colorimetry and redox titration require complicated colorimetric and titration operations, and are difficult to perform in-line automated analysis, making them unsuitable for pure water or ultrapure water production facilities where human intervention is to be minimized. Furthermore, because they require reagents, costs are high due to the cost of chemicals, maintenance, and wastewater treatment after analysis.

[0006] As a hydrogen peroxide analysis system capable of easily and sensitively analyzing a trace amount of hydrogen peroxide in water, one that calculates the hydrogen peroxide concentration in sample water using a dissolved oxygen concentration meter, as shown in Figures 4 and 5, is known. In this system, a sample water sampling pipe 33 is connected to a predetermined position of a water passage 32 that is connected to a supply source 31 of treated water (sample water) W in a water treatment process. This sample water sampling pipe 33 branches into a first path 34 and a second path 35, and then merges again at a junction pipe 36, in which a dissolved oxygen concentration meter 37 is provided as a dissolved oxygen measurement means. A catalyst resin column 38 is provided in the second path 35 as a hydrogen peroxide decomposition means. Reference numeral 39 denotes a first opening / closing valve of the first path 34, and reference numeral 40 denotes a second opening / closing valve of the second path 35. In the figures, the flow of liquid is indicated by a thick line.

[0007] In the hydrogen peroxide analysis system as described above, first, as shown in Fig. 4, the first on-off valve 39 is opened and the second on-off valve 40 is closed to supply the sample water W to the first path 34, and the dissolved oxygen concentration of the sample water W is measured by the dissolved oxygen concentration meter 37 (sample water measurement step). Next, as shown in Fig. 5, the first on-off valve 39 is closed and the second on-off valve 40 is opened to supply the sample water W to the second path 35, and the dissolved oxygen concentration of the treated water W1 by the catalyst resin column 38 is measured (treated water measurement step).

[0008] The hydrogen peroxide concentration in the sample water W is determined from the measured dissolved oxygen concentrations in the sample water W and the treated water W1 as follows. First, hydrogen peroxide contained in the sample water W introduced into the catalyst resin column 38 is decomposed to generate oxygen as shown in the following formula (1). The generated oxygen then dissolves in the water and becomes dissolved oxygen. 2H2O2 → 2H2O + O2 (1)

[0009] Here, if the dissolved oxygen concentration value in the sample water W (sample water DO) is M1 and the dissolved oxygen concentration value in the treated water W1 obtained in the treated water measurement process (treated water DO) is M2, the difference between the dissolved oxygen concentration values ​​in the treated water W1 and the sample water W is (M2-M1), so the hydrogen peroxide concentration in the sample water W can be calculated using the following formula (2). (M2-M1) × (68 / 32) (2) (Here, 68 is the molecular weight of hydrogen peroxide on the left side of equation (1) (2 times as there are two molecules), and 32 is the molecular weight of oxygen on the right side of equation (1). The units on the left side are the same as the units of DO on the right side.)

[0010] 4 and 5 has high measurement accuracy, but uses a single dissolved oxygen concentration meter to alternately measure the dissolved oxygen concentrations in the sample water W and the treated water W1 to calculate the hydrogen peroxide concentration in the sample water W. However, after switching between the measurement systems for the sample water W and the treated water W1, it takes time for the measured dissolved oxygen concentration to stabilize, and during that time it is not possible to calculate the hydrogen peroxide concentration.

[0011] Therefore, Patent Document 1 proposes a hydrogen peroxide analysis system as shown in Figures 6 and 7. In this system, a sample water sampling pipe 53 is connected to a predetermined position of a water passage 52 that communicates with a supply source 51 of treated water (sample water) W in a water treatment process, and this sample water sampling pipe 53 branches into a first path 54 and a second path 58. The rear stage of the first path 54 serves as a dissolved oxygen concentration measurement section 55, in which a dissolved oxygen concentration meter 56 is disposed, and a first opening / closing valve 57 is disposed upstream of the dissolved oxygen concentration measurement section 55. In addition, the rear stage of the second path 58 serves as a discharge section 59, and a catalyst resin column 60 is disposed in the front stage, and a second opening / closing valve 61 is disposed downstream of the catalyst resin column 60. A first communication pipe 62 having a first communication valve 63 is connected, connecting the upstream side of the first opening / closing valve 57 of the first path 54 to the downstream side of the second opening / closing valve 61 of the second path 58, and a second communication pipe 64 having a second communication valve 65 is connected, connecting the upstream side of the second opening / closing valve 61 of the second path 58 to the upstream side of the first opening / closing valve 57 of the first path 54.

[0012] In the hydrogen peroxide analysis system as described above, first, as shown in Fig. 6, first on-off valve 57 and second on-off valve 61 are opened, and first communication valve 63 and second communication valve 65 are closed, and sample water W is supplied from sample water sampling tube 53 to first path 54 and second path 58, and the dissolved oxygen concentration of sample water W flowing through first path 54 is measured by dissolved oxygen concentration meter 56. At this time, sample water W continues to flow through catalyst resin column 60 from second path 58 and is discharged as it is from discharge portion 59. Next, as shown in Fig. 7, first on-off valve 57 and second on-off valve 61 are closed, and first communication pipe 62 and second communication pipe 64 are opened, and sample water W is supplied from sample water sampling tube 53 to first path 54 and second path 58. As a result, the sample water W flowing through the second path 58 is treated in the catalyst resin column 60, and the treated water W1 passes through the second communicating pipe 64 and is passed from the dissolved oxygen concentration measuring section 55 of the first path 53 to the dissolved oxygen concentration meter 56, where the dissolved oxygen concentration is measured. The hydrogen peroxide concentration in the sample water W is then calculated from the measured dissolved oxygen concentrations of the sample water W and the treated water W1. At this time, the sample water W in the first path 54 is discharged from the discharge section 59 via the first communicating pipe 62.

[0013] The hydrogen peroxide concentration in the sample water W is then calculated from the measured dissolved oxygen concentrations in the sample water W and the treated water W1. Since the sample water W is constantly passed through the catalyst resin column 60, the dissolved oxygen concentration in the treated water W1 can be measured with good initial rise.

[0014] Furthermore, Patent Document 2 proposes a hydrogen peroxide analysis system as shown in Fig. 8 to Fig. 10. In this system, a sample water sampling pipe 73 is connected to a predetermined position of a water passage 72 that is connected to a supply source 71 of treated water (sample water) W of a water treatment process. This sample water sampling pipe 73 branches into a first path 74 and a second path 77. A first dissolved oxygen concentration meter 75 is disposed in the rear part of the first path 74, and a first opening and closing valve 76 is provided upstream of the first dissolved oxygen concentration meter 75. A catalyst resin column 78 is provided in the front part of the second path 77, while a second dissolved oxygen concentration meter 79 is disposed in the rear part, and a second opening and closing valve 80 is provided between the catalyst resin column 78 and the second dissolved oxygen concentration meter 79. A communication pipe 81 having a communication valve 82 is connected to communicate between the downstream side of the first opening and closing valve 76 of the first path 74 and the downstream side of the second opening and closing valve 80 of the second path 77.

[0015] 8, first, first on-off valve 76 and second on-off valve 80 are opened and communication valve 82 is closed, and sample water W is supplied from sample water sampling pipe 73 to first path 74 and second path 77, and the dissolved oxygen concentration of sample water W in first path 74 is measured directly by first dissolved oxygen concentration meter 75. Meanwhile, for sample water W in second path 77, treated water W1 has been treated in catalyst resin column 78, and the dissolved oxygen concentration of this treated water W1 is measured by second dissolved oxygen concentration meter 79.

[0016] 9, by closing the second opening / closing valve 80 and opening the communication valve 82, the dissolved oxygen concentration of the sample water W can be measured by the first dissolved oxygen concentration meter 75 and also by the second dissolved oxygen concentration meter 79. Furthermore, by closing the first opening / closing valve 76 and opening the communication valve 82 as shown in FIG. 10, the dissolved oxygen concentration of the treated water W1 treated in the catalyst resin column 78 can be measured by the first dissolved oxygen concentration meter 75 and also by the second dissolved oxygen concentration meter 79.

[0017] The hydrogen peroxide concentration in the sample water W is then calculated from the measured dissolved oxygen concentrations of the sample water W and the treated water W1. At this time, the dissolved oxygen concentration of the sample water W is measured by the first dissolved oxygen concentration meter 75 and also by the second dissolved oxygen concentration meter 79, and the dissolved oxygen concentration of the treated water W1 is measured by the first dissolved oxygen concentration meter 75 and also by the second dissolved oxygen concentration meter 79, thereby correcting errors due to individual differences in the dissolved oxygen concentration meters, thereby enabling the dissolved oxygen concentrations of the sample water W and the treated water W1 to be measured accurately, and ultimately making it possible to accurately calculate the hydrogen peroxide concentration in the sample water W. [Prior art documents] [Patent documents]

[0018] [Patent Document 1] JP 2019-144143 A [Patent Document 2] JP 2019-132677 A Summary of the Invention [Problem to be solved by the invention]

[0019] However, in the hydrogen peroxide concentration measurement system described in Patent Document 1, although the start-up of detection can be accelerated by supplying sample water W even when catalyst resin is not used, during measurement, sample water W is constantly circulating through both first path 54 and second path 58, so that twice the amount of sample water W needs to be collected from sample water collection tube 53, which creates problems such as the risk of water leakage entering and exiting the instrument and increased consumption of sample water W.

[0020] In addition, the hydrogen peroxide concentration measurement system described in Patent Document 2 uses dissolved oxygen concentration meters 75, 79 on both the sample water W and the treated water W (catalyst resin column 78) side, making it possible to constantly measure the hydrogen peroxide concentrations in the sample water W and the treated water W1. However, there are problems in that not only do two dissolved oxygen concentration meters need to be used, but also transmission is required to correct errors between the dissolved oxygen concentration meters.

[0021] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a hydrogen peroxide concentration measurement system and a hydrogen peroxide concentration measurement method that can shorten the time until the measurement value stabilizes after switching the measurement system and consumes little sample water. [Means for solving the problem]

[0022] In order to solve the above problems, firstly, the present invention provides a hydrogen peroxide concentration measurement system for measuring the concentration of hydrogen peroxide in sample water sampled at a predetermined position in a water passage in a water treatment process, the hydrogen peroxide concentration measurement system comprising: a sample water sampling tube for sampling the sample water; the sample water sampling tube branching into a first path and a second path; the first path being switchably provided with a dissolved oxygen concentration measurement flow path having a dissolved oxygen concentration measurement means and a first circulation flow path; the second path being switchably provided with a hydrogen peroxide decomposition flow path having a hydrogen peroxide decomposition means and a second circulation flow path; the hydrogen peroxide decomposition flow path being switchably branched into a discharge pipe and the first circulation flow path, while the dissolved oxygen concentration measurement flow path being switchably branched into a discharge pipe and the second circulation flow path; and the sample water is changeable between flowing continuously from the dissolved oxygen concentration measurement means to the hydrogen peroxide decomposition means, or flowing continuously from the hydrogen peroxide decomposition means to the dissolved oxygen concentration measurement means (Invention 1).

[0023] According to this invention (Invention 1), the sample water is not diverted and supplied, but is circulated to the oxygen concentration measuring means, where the dissolved oxygen concentration of the sample water is measured, and then circulated to the hydrogen peroxide decomposition means and discharged. The sample water is also circulated from the dissolved oxygen concentration measuring means to the hydrogen peroxide decomposition means, where the dissolved oxygen concentration of the sample water (treated water) treated by the hydrogen peroxide decomposition means is measured. The hydrogen peroxide concentration in the sample water can then be calculated from the dissolved oxygen concentrations of the sample water and the treated water. This results in a system that uses less sample water and has a stable start-up.

[0024] In the above invention (Invention 1), it is preferable that a membrane degassing device is provided upstream of the sample water sampling position in the water passage of the water treatment process (Invention 2).

[0025] According to this invention (Invention 2), the concentration of hydrogen peroxide in the sample water can be calculated with higher accuracy by degassing the sample water in advance using a membrane degassing device.

[0026] Secondly, the present invention provides a method for measuring a hydrogen peroxide concentration in sample water sampled at a predetermined position in a water passage in a water treatment process, comprising: a sample water sampling step of sampling sample water at a predetermined position in the water passage in the water treatment process; a route selection step of supplying the sample water to one of a first route in which a hydrogen peroxide decomposition flow path having a hydrogen peroxide decomposition means and a first circulation flow path are switchably provided, and a second route in which a dissolved oxygen concentration measurement flow path having a dissolved oxygen concentration measurement means and the first circulation flow path are switchably provided; The present invention provides a method for measuring a hydrogen peroxide concentration, comprising: a sample water measuring step of introducing sample water, measuring the dissolved oxygen concentration in the sample water with a dissolved oxygen concentration measuring means, passing the sample water through a hydrogen peroxide decomposition means and discharging the sample water as is; a treated water measuring step of introducing sample water to the second path side in the path selection step, treating the sample water with the hydrogen peroxide decomposition means to obtain treated water, and then introducing the treated water into the dissolved oxygen concentration measuring means to measure the dissolved oxygen concentration in the treated water; and a calculation step of calculating the hydrogen peroxide concentration in the sample water from the dissolved oxygen concentrations in the sample water and the treated water (Invention 3).

[0027] According to this invention (Invention 3), in the sample water measurement step, the dissolved oxygen concentration in the sample water is measured by the dissolved oxygen concentration measuring means, and then the sample water is passed through the hydrogen peroxide decomposition means and discharged. The flow path is then switched to introduce the sample water treated by the hydrogen peroxide decomposition means (treated water) into the dissolved oxygen concentration measuring means, and the dissolved oxygen concentration in the treated water is measured. The hydrogen peroxide concentration in the sample water can then be calculated from the measured dissolved oxygen concentrations in the sample water and the treated water. This makes it possible to measure the hydrogen peroxide concentration in the sample water with a stable start-up using a small amount of sample water.

[0028] In the above invention (Invention 3), it is preferable to have a step of degassing the sample water prior to the sample water collection step (Invention 4).

[0029] According to this invention (Invention 4), the concentration of hydrogen peroxide in the sample water can be calculated with higher accuracy by previously degassing the sample water in the degassing step. Effect of the Invention

[0030] According to the present invention, a single dissolved oxygen concentration meter can be used to measure the dissolved oxygen concentration of sample water and that of sample water treated by a hydrogen peroxide decomposition means (treated water) without dividing the sample water and supplying it separately.The hydrogen peroxide concentration in the sample water can be calculated from the dissolved oxygen concentrations of the sample water and the treated water, providing a hydrogen peroxide concentration measurement system that uses a small amount of sample water and has a stable start-up. [Brief description of the drawings]

[0031] [Figure 1] 1 is a configuration diagram of a hydrogen peroxide concentration measurement system according to one embodiment of the present invention. [Diagram 2] 5 is a schematic diagram showing a process of measuring the dissolved oxygen concentration of a water sample in the embodiment. FIG. [Diagram 3] FIG. 4 is a schematic diagram showing a process for measuring the dissolved oxygen concentration of treated water in the embodiment. [Figure 4] FIG. 1 is a schematic diagram showing a process for measuring the dissolved oxygen concentration of sample water using a conventional hydrogen peroxide concentration measurement system. [Diagram 5] FIG. 1 is a schematic diagram showing a process for measuring the dissolved oxygen concentration of treated water using a conventional hydrogen peroxide concentration measurement system. [Figure 6] 1 is a schematic diagram showing a process for measuring the dissolved oxygen concentration of sample water using the hydrogen peroxide concentration measurement system of Patent Document 1. FIG. [Figure 7] FIG. 1 is a schematic diagram showing a process for measuring the dissolved oxygen concentration in treated water using the hydrogen peroxide concentration measuring system of Patent Document 1. [Figure 8] FIG. 1 is a schematic diagram showing the steps of measuring the dissolved oxygen concentrations of sample water and treated water using the hydrogen peroxide concentration measurement system of Patent Document 2. [Figure 9] FIG. 1 is a schematic diagram showing a measurement process for correcting the dissolved oxygen concentration in sample water using the hydrogen peroxide concentration measurement system of Patent Document 1. [Figure 10] FIG. 1 is a schematic diagram showing a measurement process for correcting the dissolved oxygen concentration of treated water using the hydrogen peroxide concentration measurement system of Patent Document 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Hereinafter, one embodiment of the present invention will be described with reference to Figures 1 to 3. However, the present invention is not limited to this embodiment.

[0033] [Hydrogen peroxide concentration measurement system] Fig. 1 is a schematic diagram showing the configuration of a hydrogen peroxide concentration measurement system according to one embodiment of the present invention. In Fig. 1, the hydrogen peroxide concentration measurement system has a sample water sampling pipe 3 connected to a predetermined position of a water passage 2 that is connected to a supply source 1 of treated water (sample water) W in a water treatment process. The sample water sampling pipe 3 branches into a first path 4 and a second path 5. A first three-way valve 6 is provided in the first path 4 as a switching means, and the first three-way valve 6 can switch between a dissolved oxygen concentration measurement flow path 7 having a dissolved oxygen concentration meter 8 as a dissolved oxygen concentration measurement means and a first circulation flow path 9. A second three-way valve 10 is provided in the second path 5 as a switching means, and the second three-way valve 10 can switch between a hydrogen peroxide decomposition flow path 11 having a catalyst resin column 12 as a hydrogen peroxide decomposition means and a second circulation flow path 13.

[0034] A third three-way valve 15 is provided at the end of dissolved oxygen concentration measurement flow path 7, and can be switched between exhaust pipe 14 and second circulation flow path 13. Furthermore, a fourth three-way valve 16 is provided at the end of hydrogen peroxide decomposition flow path 11, and can be switched between exhaust pipe 14 and first circulation flow path 9.

[0035] By switching the first three-way valve 6, the second three-way valve 10, the third three-way valve 15, and the fourth three-way valve 16, it is possible to switch whether the sample water W flows continuously from the dissolved oxygen concentration meter 8 to the catalyst resin column 12, or from the catalyst resin column 12 to the dissolved oxygen concentration meter 8.

[0036] The dissolved oxygen concentration meter 8 as a dissolved oxygen concentration measuring means is adjusted to have the least error within a predetermined flow rate range, so it is preferable to adjust the flow rate within that range. Therefore, a flow meter may be provided downstream of the dissolved oxygen concentration meter. It is also preferable to calibrate the dissolved oxygen concentration meter 8 before use.

[0037] The catalytic resin column 12 is preferably filled with a catalytic metal carrier (platinum group metal catalyst) carrying a platinum group metal. Hydrogen peroxide in the water to be treated (sample water) W is brought into contact with the platinum group metal catalyst, and the hydrogen peroxide can be decomposed by catalytic decomposition. The platinum group metal catalyst is supported on, for example, an anion exchanger. The anion exchanger may be a granular anion exchange resin.

[0038] [Method for measuring hydrogen peroxide concentration] Next, a hydrogen peroxide concentration measuring method according to this embodiment using the hydrogen peroxide concentration measuring system described above will be described.

[0039] (Sample water collection process and route selection process) First, treated water (sample water) W from a water treatment process is sampled from a sample water sampling pipe 3 connected to a water passage 2. The sampled sample water W is selectively supplied to either the first path 4 or the second path 5 by closing either the first three-way valve 6 on the first path 4 side or the second three-way valve 10 on the second path 5 side.

[0040] (Sample water measurement process) 2, in the sample water measurement process, the first three-way valve 6 opens the first path 4 and the dissolved oxygen concentration measurement flow path 7 while closing the first circulation flow path 9, the second three-way valve 10 closes the second path 5 while opening the hydrogen peroxide decomposition flow path 11 and the second circulation flow path 13. The third three-way valve 15 opens the dissolved oxygen concentration measurement flow path 7 and the second circulation flow path 13 while closing the exhaust pipe 14, and the fourth three-way valve 16 opens the hydrogen peroxide decomposition flow path 11 and the exhaust pipe 14 while closing the first circulation flow path 9.

[0041] In this state, when the sample water W collected by the sample water sampling tube 3 is supplied, the second three-way valve 10 closes the second path 5 side, so that the sample water W flows through the first path 4 side and passes through the first three-way valve 6 into the dissolved oxygen concentration measurement flow path 7, and the dissolved oxygen concentration (M1) of the sample water W is measured by the dissolved oxygen concentration meter 8. The sample water W then reaches the third three-way valve 15 provided at the end of the dissolved oxygen concentration measurement flow path 7. At this time, the third three-way valve 15 opens the dissolved oxygen concentration measurement flow path 7 side and the second circulation flow path 13 side, but closes the discharge pipe 14 side, so that the sample water W flows through the second circulation flow path 13 and reaches the second three-way valve 10. The treated water W1 then flows from second three-way valve 10 into hydrogen peroxide decomposition flow path 11, where hydrogen peroxide is decomposed in catalytic resin column 12. After that, the treated water W1 reaches fourth three-way valve 16 provided at the end of hydrogen peroxide decomposition flow path 11. At this time, the fourth three-way valve 16 is open on the side facing discharge pipe 14 and closed on the side facing first circulation flow path 9, so that the treated water W1 is discharged from the system through discharge pipe 14. In this manner, the dissolved oxygen concentration (M1) of the sample water W is measured.

[0042] (Treated water measurement process) 3, in the sample water measurement process, the first three-way valve 6 opens the dissolved oxygen concentration measurement flow path 7 and the first circulation flow path 9 while closing the first path 4, the second three-way valve 10 opens the second path 5 and the hydrogen peroxide decomposition flow path 11 while closing the second circulation flow path 13. The third three-way valve 15 opens the dissolved oxygen concentration measurement flow path 7 and the exhaust pipe 14 while closing the second circulation flow path 13, and the fourth three-way valve 16 opens the hydrogen peroxide decomposition flow path 11 and the first circulation flow path 9 while closing the exhaust pipe 14.

[0043] In this state, when the sample water W collected by the sample water collection tube 3 is supplied, the first three-way valve 6 closes the first path 4 side, so the sample water W collected by the sample water collection tube 3 flows through the second path 5 side, passes through the second three-way valve 10, and flows into the hydrogen peroxide decomposition flow path 11. After being treated by the catalyst resin column 12, the treated water W1 reaches the fourth three-way valve 14 provided at the end of the hydrogen peroxide decomposition flow path 11. At this time, the fourth three-way valve 14 is closed on the discharge pipe 14 side and open on the first circulation flow path 9 side, so the treated water W1 flows through the first circulation flow path 9 and reaches the first three-way valve 6. Then, the treated water W1 flows from the first three-way valve 6 into the dissolved oxygen concentration measurement flow path 7, and the dissolved oxygen concentration of the treated water W1 is measured by the dissolved oxygen concentration meter 8. The treated water W1 then reaches the third three-way valve 15 provided at the end of the dissolved oxygen concentration measurement flow path 7. At this time, the third three-way valve 15 is open on the discharge pipe 14 side and closed on the second circulation flow path 13 side, so that the treated water W1 is discharged to the outside of the system through the discharge pipe 14. In this manner, the dissolved oxygen concentration (M2) of the treated water W1 is measured.

[0044] (calculation process) The hydrogen peroxide concentration in the sample water W is calculated from the measured dissolved oxygen concentration M1 in the sample water W and the dissolved oxygen concentration M2 in the treated water W1 as follows. First, the hydrogen peroxide contained in the sample water W introduced into the catalyst resin column 12 is decomposed as shown in the following formula (1). The generated oxygen then dissolves in the water and becomes dissolved oxygen. 2H2O2 → 2H2O + O2 (1)

[0045] Here, since the difference in the dissolved oxygen concentration value between the treated water W1 and the sample water W is (M2-M1), the hydrogen peroxide concentration in the sample water W can be calculated by the following formula (2). (M2-M1) × (68 / 32) (2) (Here, 68 is the molecular weight of hydrogen peroxide on the left side of equation (1) (2 times as there are two molecules), and 32 is the molecular weight of oxygen on the right side of equation (1). The units on the left side are the same as the units of DO on the right side.)

[0046] In this embodiment, a membrane degassing device is provided upstream of the sampling position of the sample water W to perform a degassing process before the sample water sampling process, thereby reducing the dissolved oxygen concentration and other dissolved gases in the sample water W, thereby further improving the detection accuracy of the hydrogen peroxide concentration in the sample water W.

[0047] As described above, in this embodiment, a single dissolved oxygen concentration meter 8 is used to measure the dissolved oxygen concentration M1 of the sample water W and the dissolved oxygen concentration M2 of the sample water (treated water) W1 treated in the catalyst resin column 12, without dividing and supplying the sample water W. The hydrogen peroxide concentration in the sample water W can then be calculated from the dissolved oxygen concentration M1 of the sample water W and the dissolved oxygen concentration M2 of the treated water W1. As a result, the amount of sample water W used is small, and the water is constantly passed through the catalyst resin column 12, resulting in a hydrogen peroxide concentration measurement system with a stable start-up.

[0048] Although the present invention has been described above based on the above embodiment, the present invention is not limited to the above embodiment and can be modified in various ways. For example, in the above embodiment, the sample water measurement step is followed by the treated water measurement step, but these steps may be performed in the reverse order. In addition, there are no particular limitations on the water treatment process equipment, but the present invention is particularly suitable for equipment that requires the quantification of trace amounts of hydrogen peroxide concentration, such as pure water production equipment and ultrapure water production equipment. EXAMPLES

[0049] The present invention will be described in more detail with reference to the following specific examples.

[0050] Example 1 Ultrapure water adjusted to a hydrogen peroxide concentration of approximately 15 μg / L was introduced as sample water W into the hydrogen peroxide concentration measurement system shown in FIG. 1, and the hydrogen peroxide concentration was measured.

[0051] The ultrapure water before adjustment had a resistivity of 18.1 MΩ·CM or more, fine particles of 50 nm or more and 1000 particles / L or less, live bacteria of 1 particle / L or less, TOC (TOTAL ORGANIC CARBON): 1 μg / L or less, total silicon: 0.1 μg / L or less, metals: 1 ng / L or less, ions: 10 ng / L or less, and a water temperature of 25±2°C.

[0052] First, as shown in FIG. 2, the first three-way valve 6 opened the first path 4 and the dissolved oxygen concentration measurement path 7, and closed the first circulation path 9. The second three-way valve 10 closed the second path 5, and opened the hydrogen peroxide decomposition path 11 and the second circulation path 13. The third three-way valve 15 opened the dissolved oxygen concentration measurement path 7 and the second circulation path 13, and closed the discharge pipe 14. The fourth three-way valve 16 opened the hydrogen peroxide decomposition path 11 and the discharge pipe 14, and closed the first circulation path 9. In this state, the sample water W was introduced from the first path 4 into the dissolved oxygen concentration meter 8 to measure the dissolved oxygen concentration (M1), and then the sample water W was introduced into the catalyst resin column 12 for treatment, and the treated water W1 was discharged from the discharge pipe 14 to the outside of the system.

[0053] Next, each three-way valve was switched as shown in Fig. 3. That is, the first three-way valve 6 opened the dissolved oxygen concentration measurement flow path 7 side and the first circulation flow path 9 side, and closed the first path 4 side. The second three-way valve 10 opened the second path 5 side and the hydrogen peroxide decomposition flow path 11 side, and closed the second circulation flow path 13 side. The third three-way valve 15 opened the dissolved oxygen concentration measurement flow path 7 side and the exhaust pipe 14 side, and closed the second circulation flow path 13 side. The fourth three-way valve 16 opened the hydrogen peroxide decomposition flow path 11 side and the first circulation flow path 9 side, and closed the exhaust pipe 14 side. In this state, the sample water W was treated in the catalyst resin column 12 from the second path 5, and then the treated water W1 was made to flow into the dissolved oxygen concentration measurement path 7 via the first circulation path 9, introduced into the dissolved oxygen concentration meter 8 to measure the dissolved oxygen concentration (M2), and then the treated water W1 was discharged outside the system through the discharge pipe 14.

[0054] The values ​​of the dissolved oxygen concentration (M1) of the sample water W and the dissolved oxygen concentration (M2) of the treated water W1 measured in this manner were stable, and the hydrogen peroxide concentration of the sample water W calculated from these values ​​was close to 15 μg / L. In addition, the flow rate of the sample water W during operation of the hydrogen peroxide concentration measurement system of Example 1 was 1 L / min, and the measurement time was 2 min / cycle.

[0055] Comparative Example 1 The hydrogen peroxide concentration was measured using the same sample water W as in Example 1 using the hydrogen peroxide concentration measurement system shown in FIGS.

[0056] First, as shown in Fig. 4, the first on-off valve 39 was opened and the second on-off valve 40 was closed to supply the sample water W to the first path 34, and the dissolved oxygen concentration (M1) of the sample water W was measured by the dissolved oxygen concentration meter 37. Next, as shown in Fig. 5, the first on-off valve 39 was closed and the second on-off valve 40 was opened to introduce the sample water W into the catalyst resin column 38 for treatment, and the dissolved oxygen concentration (M2) contained in this treated water W1 was measured by the dissolved oxygen concentration meter 37.

[0057] The values ​​of the dissolved oxygen concentration (M1) of the sample water W and the dissolved oxygen concentration (M2) of the treated water W1 measured in this manner took at least 2 minutes for the dissolved oxygen concentration (M2) of the treated water W1 to stabilize, and this was a time required to accurately calculate the hydrogen peroxide concentration of the sample water W. This is thought to be because the water supply to the catalyst resin column 38 was stopped initially, and it took time for it to stabilize at start-up. In addition, the flow rate of the sample water W during operation of the hydrogen peroxide concentration measurement system of Comparative Example 1 was 1 L / min, and the measurement time was 10 min / cycle.

[0058] Comparative Example 2 The hydrogen peroxide concentration was measured using the same sample water W as in Example 1 using the hydrogen peroxide concentration measurement system shown in FIGS.

[0059] 6, first opening / closing valve 57 and second opening / closing valve 61 were opened, and first communication valve 63 and second communication valve 65 were closed, and sample water W was supplied from sample water sampling tube 53 to first path 54 and second path 58, and the dissolved oxygen concentration (M1) of sample water W in first path 54 was measured by dissolved oxygen concentration meter 56. During this period, sample water W was also supplied to second path 58, passed through catalyst resin column 60, and then discharged.

[0060] 7, first opening / closing valve 57 and second opening / closing valve 61 were closed, and first communicating pipe 62 and second communicating pipe 64 were opened, and sample water W was supplied from sample water sampling pipe 53 to first path 54 and second path 58. As a result, sample water W in second path 58 was treated in catalyst resin column 60, and then passed through second communicating pipe 64 and introduced from dissolved oxygen concentration measuring section 55 of first path 53 to dissolved oxygen concentration meter 56, where the dissolved oxygen concentration (M2) was measured. During this time, sample water W was also supplied to first path 54, and discharged from discharge section 59 via first communicating pipe 62.

[0061] The values ​​of the dissolved oxygen concentration (M1) of the sample water W and the dissolved oxygen concentration (M2) of the treated water W1 measured in this manner were stable, and the hydrogen peroxide concentration of the sample water W calculated from these values ​​was close to 15 μg / L, similar to that of Example 1. Furthermore, the flow rate of the sample water W during operation of the hydrogen peroxide concentration measurement system of Comparative Example 2 was 2 L / min, and the measurement time was 2 minutes / cycle.

[0062] Comparative Example 3 The hydrogen peroxide concentration was measured using the same sample water W as in Example 1 using the hydrogen peroxide concentration measurement system shown in FIG.

[0063] 8 , first opening / closing valve 76 and second opening / closing valve 80 were opened, and communication valve 82 was closed. In this state, sample water W was supplied from sample water sampling tube 73 to first path 74 and second path 77, and the dissolved oxygen concentration M1 of sample water W in first path 74 was measured by first dissolved oxygen concentration meter 75. In addition, sample water W in second path 77 was treated in catalyst resin column 78, and the dissolved oxygen concentration M2 of this treated water W1 was measured by second dissolved oxygen concentration meter 79.

[0064] The values ​​of the dissolved oxygen concentration (M1) of the sample water W and the dissolved oxygen concentration (M2) of the treated water W1 measured in this manner were stable, but the hydrogen peroxide concentration of the sample water W calculated from these values ​​had a larger error than in Example 1, Comparative Example 1, and Comparative Example 2. This is thought to be due to an error between the first dissolved oxygen concentration meter 75 and the second dissolved oxygen concentration meter 79. Furthermore, the flow rate of the sample water W during operation of the hydrogen peroxide concentration measurement system in Comparative Example 3 was 2 L / min, and the measurement time was 1 min / cycle.

[0065] In Comparative Example 3, as shown in Figures 9 and 10, sample water W was supplied to both first dissolved oxygen concentration meter 75 and second dissolved oxygen concentration meter 79 simultaneously, and treated water W1 was also supplied simultaneously. The calculation accuracy of the hydrogen peroxide concentration could be improved by correcting the errors between the first dissolved oxygen concentration meter 75 and the second dissolved oxygen concentration meter 79 from the difference in the measured values ​​between them. However, in this case, the measurement time for the sample water W required to operate the hydrogen peroxide concentration measurement system in Comparative Example 3 was approximately three times longer.

[0066] Table 1 shows the flow rate of the sample water W, the measurement time, and the number of constituent devices (the number of catalyst resin columns+the number of dissolved oxygen concentration meters) in Example 1 and Comparative Examples 1 to 3.

[0067] [Table 1]

[0068] As is apparent from Table 1, the hydrogen peroxide concentration measurement system of Example 1 has a flow rate of the sample water W. Not only is the measurement time short, but the number of components is also small, making it the most comprehensively superior method. [Explanation of symbols]

[0069] 1. Source of treated water (sample water) W from the treatment process 2 Waterway 3. Sample water collection tube 4. First Path 5. The second route 6. First three-way valve 7 Dissolved oxygen concentration measurement flow path 8. Dissolved oxygen concentration meter (Means for measuring dissolved oxygen concentration) 9 First Circulation Channel 10. Second three-way valve 11 Hydrogen peroxide decomposition channel 12 Catalyst resin column (means for decomposing hydrogen peroxide) 13 First circulation channel 14 Discharge pipe 15 Third three-way valve 16 Fourth three-way valve

Claims

1. A hydrogen peroxide concentration measurement system for measuring the concentration of hydrogen peroxide in sample water collected at a predetermined position in a water passage of a water treatment process, a sample water collection tube for collecting the sample water; The sample water collection tube is branched into a first path and a second path, The first path is provided with a dissolved oxygen concentration measurement flow path having a dissolved oxygen concentration measurement means and a first circulation flow path that can be switched between the dissolved oxygen concentration measurement flow path and the first circulation flow path, the second path is provided with a hydrogen peroxide decomposition flow path having a hydrogen peroxide decomposition means and a second circulation flow path that can be switched between the hydrogen peroxide decomposition flow path and the second circulation flow path, the hydrogen peroxide decomposition flow path is switchably branched into an exhaust pipe and the first circulation flow path, while the dissolved oxygen concentration measurement flow path is switchably branched into an exhaust pipe and a second circulation flow path, A hydrogen peroxide concentration measurement system in which it is possible to change whether the sample water flows continuously from the dissolved oxygen concentration measurement means to the hydrogen peroxide decomposition means, or from the hydrogen peroxide decomposition means to the dissolved oxygen concentration measurement means.

2. 2. The hydrogen peroxide concentration measurement system according to claim 1, further comprising a membrane degassing device disposed upstream of a sample water sampling position in a water passage for the water treatment process.

3. A method for measuring a hydrogen peroxide concentration in a sample of water collected at a predetermined position in a water passage of a water treatment process, comprising the steps of: a sample water collection step of collecting sample water at a predetermined position in a water passage of the water treatment process; a route selection step of supplying the collected sample water to either a first route provided in a switchable manner between a hydrogen peroxide decomposition flow path having a hydrogen peroxide decomposition means and a first circulation flow path, or a second route provided in a switchable manner between a dissolved oxygen concentration measurement flow path having a dissolved oxygen concentration measurement means and the first circulation flow path; a sample water measuring step of introducing sample water into a first path side in the path selection step, measuring the dissolved oxygen concentration in the sample water by a dissolved oxygen concentration measuring means, and then passing the sample water through a hydrogen peroxide decomposition means and discharging the sample water; a treated water measurement step of introducing sample water into the second path side in the path selection step, treating the sample water with a hydrogen peroxide decomposition means to obtain treated water, and then introducing the treated water into the dissolved oxygen concentration measurement means to measure the dissolved oxygen concentration in the treated water; a calculation step of calculating a hydrogen peroxide concentration in the sample water from the dissolved oxygen concentration in the sample water and the dissolved oxygen concentration in the treated water; A method for measuring a hydrogen peroxide concentration, comprising:

4. 4. The method for measuring a concentration of hydrogen peroxide according to claim 3, further comprising a step of degassing the sample water prior to the step of collecting the sample water.

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