Hydrogen peroxide concentration measurement system and hydrogen peroxide concentration measurement method

Abstract

In this hydrogen peroxide concentration measurement system, a sample water collection tube (3) is branched into a first passage (4) and a second passage (5), and the first passage (4) can be switched between a dissolved oxygen concentration measurement flow passage (7) and a first circulation flow passage (9). The second passage (5) can be switched between a hydrogen peroxide decomposition flow passage (11) and a second circulation flow passage (13). Further, the dissolved oxygen concentration measurement flow path (7) can be switched between the discharge pipe (14) and the second circulation flow path (13). In addition, the hydrogen peroxide decomposition flow path (11) can be switched between the discharge pipe (14) and the first circulation flow path (9). As a result, it is possible to switch between the continuous flow of the sample water (W) from the dissolved oxygen concentration meter (8) to the catalyst resin column (12) or the continuous flow of the sample water (W) from the catalyst resin column (12) to the dissolved oxygen concentration meter (8). As long as the hydrogen peroxide concentration measurement system is adopted, the time until the measured value after the measurement system is switched is stable can be shortened, and the consumption of sample water is low.

Description

Technical Field

[0001] This invention relates to a system and method for determining the concentration of trace amounts of hydrogen peroxide in water samples such as pure water / ultrapure water. Background Technology

[0002] Previously, ultrapure water used in the semiconductor and other electronics industries was produced by treating raw water using an ultrapure water production system consisting of a pretreatment system, a primary pure water production device, and an auxiliary system (secondary pure water production device) that treats the primary pure water.

[0003] In the manufacturing process of ultrapure water used in the electronics industry, hydrogen peroxide is a crucial factor in the management of ultrapure water supply. For example, copper, a representative wiring metal, can be corroded by hydrogen peroxide solutions of around a few mg / L, affecting surface flatness or causing dissolution, thereby impacting the electrical properties of semiconductor products and reducing yield. Furthermore, it is known that hydrogen peroxide is generated in pure or ultrapure water manufacturing equipment, such as in ultraviolet irradiation equipment designed to decompose organic matter. Therefore, it is necessary to analyze (monitor) the hydrogen peroxide concentration.

[0004] Previously, known methods for analyzing the concentration of hydrogen peroxide included test paper or reagents, colorimetry, and redox titration. However, for hydrogen peroxide concentration analysis using equipment capable of producing pure or ultrapure water, the analytical values ​​needed are typically at the micro-level (around 1 mg / L). Among the aforementioned analytical methods, the test paper or reagent method is difficult to use for determining analytical values ​​at the 1 mg / L level.

[0005] Furthermore, colorimetric and redox titration methods are complex to perform, and online automated analysis is difficult, making them particularly unsuitable for pure or ultrapure water preparation equipment where manual intervention is highly desired. Additionally, the cost is higher due to the need for reagents, the associated costs of pharmaceuticals, maintenance, and waste disposal.

[0006] Therefore, as a hydrogen peroxide analysis system that can easily and with high sensitivity analyze trace amounts of hydrogen peroxide in water, such as Figure 4 and Figure 5As shown, the hydrogen peroxide concentration in the sample water is calculated using the dissolved oxygen concentration. The system connects the sample water collection pipe 33 to a designated point on the water passage 32, which connects to the supply source 31 of the treated water (sample water) W in the water treatment process. The sample water collection pipe 33 branches into a first passage 34 and a second passage 35, and then merges again in a confluence pipe 36. A dissolved oxygen meter 37, serving as a dissolved oxygen measuring device, is installed in this confluence pipe 36. Furthermore, a catalyst resin column 38, serving as a hydrogen peroxide decomposition device, is installed in the second passage 35. It should be noted that 39 is the first on / off valve of the first passage 34, and 40 is the second on / off valve of the second passage 35. It should also be noted that the liquid flow path is represented by a thick line in the figure.

[0007] In the hydrogen peroxide analysis system described above, firstly, as... Figure 4 As shown, ensure that the first on / off valve 39 is open and the second on / off valve 40 is closed to supply sample water W to the first passage 34, thereby measuring the dissolved oxygen concentration of sample water W using dissolved oxygen meter 37 (sample water measurement procedure). Then, as... Figure 5 As shown, the first on / off valve 39 is closed and the second on / off valve 40 is ensured to be open to supply sample water W to the second passage 35, thereby determining the dissolved oxygen concentration contained in the treated water W1 using the catalyst resin column 38 (treated water determination procedure).

[0008] Furthermore, in order to determine the hydrogen peroxide concentration in sample water W based on the measured dissolved oxygen concentration of sample water W and treated water W1, the following procedure is performed. That is, firstly, the hydrogen peroxide contained in sample water W introduced into catalyst resin column 38 decomposes as shown in the following formula (1) to generate oxygen. Then, the generated oxygen dissolves in the water to become dissolved oxygen.

[0009] 2H₂O₂→2H₂O+O₂ (1)

[0010] Here, if the dissolved oxygen concentration value (sample water DO) in sample water W is set as M1, and the dissolved oxygen concentration value (treated water DO) in treated water W1 obtained in the treated water determination process is set as M2, then the difference between the dissolved oxygen concentration values ​​in treated water W1 and sample water W is (M2-M1). Therefore, the hydrogen peroxide concentration in sample water W can be calculated by the following formula (2).

[0011] (M2-M1) × (68 / 32) (2)

[0012] (Here, 68 is the molecular weight of hydrogen peroxide on the left side of equation (1) (because it is 2 molecules, so it is 2 times), 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 dissolved oxygen (DO) on the right side.)

[0013] In Figure 4and Figure 5 In the existing technology shown, although the measurement accuracy is high, it calculates the hydrogen peroxide concentration in sample water W by alternately measuring the dissolved oxygen concentration in sample water W and treated water W1 using a single dissolved oxygen meter. However, after switching between the measurement systems for sample water W and treated water W1, time is required until the dissolved oxygen concentration measurement value stabilizes, during which time the hydrogen peroxide concentration cannot be calculated.

[0014] Therefore, as proposed in Patent Document 1 Figure 6 and Figure 7 The system describes a hydrogen peroxide analysis system as shown. The system connects a sample water collection pipe 53 to a predetermined location in a water passage 52 that connects to a supply source 51 for treated water (sample water) W in a water treatment process. This sample water collection pipe 53 branches into a first passage 54 and a second passage 58. The latter part of the first passage 54 becomes a dissolved oxygen concentration measuring section 55, where a dissolved oxygen meter 56 is installed. A first on / off valve 57 is located upstream of the dissolved oxygen concentration measuring section 55. The latter part of the second passage 58 becomes a discharge section 59, and a catalyst resin column 60 is installed at the front of the second passage. A second on / off valve 61 is located downstream of the catalyst resin column 60. In addition, a first connecting pipe 62 with a first connecting valve 63 is connected, and a second connecting pipe 64 with a second connecting valve 65 is connected. The first connecting pipe 62 connects the upstream side of the first on / off valve 57 of the first passage 54 to the downstream side of the second on / off valve 61 of the second passage 58, and the second connecting pipe 64 connects the upstream side of the second on / off valve 61 of the second passage 58 to the upstream side of the first on / off valve 57 of the first passage 54.

[0015] In the hydrogen peroxide analysis system described above, firstly, as... Figure 6 As shown, ensure that the first on / off valve 57 and the second on / off valve 61 are open, and with the first connecting valve 63 and the second connecting valve 65 closed, supply sample water W to the first passage 54 and the second passage 58 through the sample water collection tube 53, thereby measuring the dissolved oxygen concentration of the sample water W flowing in the first passage 54 using a dissolved oxygen concentration meter 56. At this time, sample water W is also continuously supplied to the catalyst resin column 60 from the second passage 58, and discharged directly from the discharge section 59. Then, as... Figure 7As shown, the first on / off valve 57 and the second on / off valve 61 are closed, and with the first connecting pipe 62 and the second connecting pipe 64 ensured to be open, sample water W is supplied to the first passage 54 and the second passage 58 through the sample water collection pipe 53. The sample water W flowing in the second passage 58 is then treated using the catalyst resin column 60, and the treated water W1 passes through the second connecting pipe 64. The dissolved oxygen concentration is then measured in the dissolved oxygen meter 56 by the dissolved oxygen concentration measuring unit 55 in the first passage 53. Then, the hydrogen peroxide concentration in the sample water W is calculated based on the measured dissolved oxygen concentration of the sample water W and the dissolved oxygen concentration of the treated water W1. At this time, the sample water W in the first passage 54 is discharged from the discharge unit 59 via the first connecting pipe 62.

[0016] Then, the hydrogen peroxide concentration in the sample water W is calculated based on the dissolved oxygen concentration of the sample water W and the dissolved oxygen concentration of the treated water W1. At this time, since the sample water W is continuously circulated into the catalyst resin column 60, the dissolved oxygen concentration of the treated water W1 can be measured quickly and responsively.

[0017] Furthermore, as proposed in Patent Document 2... Figures 8-10 The system describes a hydrogen peroxide analysis system as shown. The system connects a sample water collection tube 73 to a designated location on a water passage 72 that connects to a supply source 71 for treated water (sample water) W in a water treatment process. The sample water collection tube 73 branches into a first passage 74 and a second passage 77. A first dissolved oxygen meter 75 is located at the rear of the first passage 74, and a first on / off valve 76 is located upstream of the first dissolved oxygen meter 75. A catalyst resin column 78 is located at the front of the second passage 77, and a second dissolved oxygen meter 79 is located at the rear. A second on / off valve 80 is located between the catalyst resin column 78 and the second dissolved oxygen meter 79. A connecting pipe 81 with a connecting valve 82 connects the downstream side of the first on / off valve 76 in the first passage 74 to the downstream side of the second on / off valve 80 in the second passage 77.

[0018] In the hydrogen peroxide analysis system described above, firstly, as... Figure 8 As shown, ensure that the first on / off valve 76 and the second on / off valve 80 are open, and with the connecting valve 82 closed, supply sample water W from the sample water collection pipe 73 to the first passage 74 and the second passage 77, thereby directly measuring the dissolved oxygen concentration of the sample water W in the first passage 74 using the first dissolved oxygen meter 75. On the other hand, for the sample water W in the second passage 77, use the second dissolved oxygen meter 79 to measure the dissolved oxygen concentration of the treated water W1 after treatment with the catalyst resin column 78.

[0019] In addition, such as Figure 9As shown, by closing the second on / off valve 80 and ensuring the connecting valve 82 is open, the dissolved oxygen concentration of sample water W can be measured using the first dissolved oxygen meter 75, and it can also be measured using the second dissolved oxygen meter 79. Further, as... Figure 10 As shown, by closing the first on / off valve 76 and ensuring that the connecting valve 82 is open, the dissolved oxygen concentration of the treated water W1 after treatment with the catalyst resin column 78 can be measured using the first dissolved oxygen concentration meter 75, and the second dissolved oxygen concentration meter 79 can also be used for measurement.

[0020] Furthermore, the hydrogen peroxide concentration in sample water W is calculated based on the dissolved oxygen concentrations of the sample water W and the treated water W1 after measurement. At this time, the dissolved oxygen concentration of sample water W is measured using a first dissolved oxygen meter 75, and also using a second dissolved oxygen meter 79. Similarly, the dissolved oxygen concentration of treated water W1 is measured using the first dissolved oxygen meter 75, and also using the second dissolved oxygen meter 79. This corrects for errors caused by individual differences in the dissolved oxygen meters, allowing for high-precision measurement of the dissolved oxygen concentrations of sample water W and treated water W1, thereby enabling the high-precision calculation of the hydrogen peroxide concentration in sample water W.

[0021] Existing technical documents

[0022] Patent documents

[0023] Patent document 1: Japanese Patent Application Publication No. 2019-144143.

[0024] Patent Document 2: Japanese Patent Application Publication No. 2019-132677. Summary of the Invention

[0025] The problem that the invention aims to solve

[0026] However, in the hydrogen peroxide concentration determination system described in Patent Document 1, the detection response can be accelerated by supplying sample water W even without using catalyst resin. However, since the sample water W is always flowing in both the first passage 54 and the second passage 58 during measurement, the amount of sample water W collected from the sample water collection tube 53 needs to be twice the amount. Therefore, there is a risk of water leakage at the instrument inlet and outlet, and an increase in the consumption of sample water W.

[0027] In addition, in the hydrogen peroxide concentration measurement system described in Patent Document 2, by using dissolved oxygen concentration meters 75 and 79 on both the sample water W and the treated water W (catalyst resin column 78) sides, the hydrogen peroxide concentration of the sample water W and the treated water W1 can be measured continuously. However, there is a problem that not only do two dissolved oxygen concentration meters need to be used, but also an operation is required to correct the error between the dissolved oxygen concentration meters.

[0028] The present invention was made in view of the above-mentioned problems, and its object is to provide a hydrogen peroxide concentration determination system and a hydrogen peroxide concentration determination method that can shorten the time until the measured value stabilizes after the measurement system is switched and consume less sample water.

[0029] Methods for solving problems

[0030] To address the aforementioned issues, firstly, this invention provides a hydrogen peroxide concentration measuring system, which measures the hydrogen peroxide concentration in sample water collected at a predetermined location in the water flow path of a water treatment process. The system includes a sample water collection tube for collecting the sample water, which branches into a first passage and a second passage. The first passage is configured with a dissolved oxygen concentration measuring flow path and a first circulation flow path, both of which can be switched. The second passage is configured with a hydrogen peroxide decomposition flow path and a second circulation flow path, both of which can be switched. The hydrogen peroxide decomposition flow path branches into a discharge pipe and the first circulation flow path, and the dissolved oxygen concentration measuring flow path branches into a discharge pipe and the second circulation flow path, both of which can be switched. The hydrogen peroxide concentration measuring system is configured to allow the sample water to flow continuously from the dissolved oxygen concentration measuring mechanism to the hydrogen peroxide decomposition mechanism, or vice versa (Invention 1).

[0031] According to the invention described above (Invention 1), without supplying sample water separately, it flows into an oxygen concentration measuring device to measure the dissolved oxygen concentration of the sample water, and then flows into a hydrogen peroxide decomposition device and is discharged. Alternatively, it flows from the dissolved oxygen concentration measuring device to the hydrogen peroxide decomposition device to measure the dissolved oxygen concentration of the sample water (treated water) after treatment by the hydrogen peroxide decomposition device. Furthermore, the hydrogen peroxide concentration in the sample water can be calculated based on the dissolved oxygen concentrations of the sample water and the treated water. This results in a system that uses a small amount of sample water and has a stable response.

[0032] In the above invention (Invention 1), it is preferable to have a membrane degassing device (Invention 2) at a point further forward than the water collection position of the water passage in the water treatment process.

[0033] According to the invention (Invention 2), by pre-degassing the sample water using a membrane degassing device, the concentration of hydrogen peroxide in the sample water can be calculated with higher accuracy.

[0034] Furthermore, secondly, the present invention provides a method for determining hydrogen peroxide concentration, which is a method for determining the hydrogen peroxide concentration in sample water collected at a predetermined location in the water flow path of a water treatment process. The method includes: a sample water collection step, in which sample water is collected at a predetermined location in the water flow path of the water treatment process; and a path selection step, in which the collected sample water is supplied to either a first path or a second path. The first path is configured to be switchable, comprising a hydrogen peroxide decomposition flow path with a hydrogen peroxide decomposition mechanism and a first circulation flow path. The second path is configured to be switchable, comprising a dissolved oxygen concentration measuring flow path with a dissolved oxygen concentration measuring mechanism. The process includes: a path and a first circulating flow path; a sample water determination process, in which sample water is introduced into the first path side in the path selection process and the dissolved oxygen concentration in the sample water is determined by a dissolved oxygen concentration measuring device, and then the sample water is passed through a hydrogen peroxide decomposition device and directly drained; a treated water determination process, in which sample water is introduced into the second path side in the path selection process and treated by a hydrogen peroxide decomposition device to obtain treated water, and then the treated water is introduced into the dissolved oxygen concentration measuring device and the dissolved oxygen concentration in the treated water is determined; and a calculation process, which calculates the hydrogen peroxide concentration in the sample water based on the dissolved oxygen concentration in the sample water and the dissolved oxygen concentration in the treated water (Invention 3).

[0035] According to the invention described above (Invention 3), in the sample water measurement process, after measuring the dissolved oxygen concentration in the sample water using a dissolved oxygen concentration measuring device, the sample water is passed through a hydrogen peroxide decomposition device and then discharged. Alternatively, the flow path is switched, and the sample water (treated water) treated by the hydrogen peroxide decomposition device is introduced into the dissolved oxygen concentration measuring device to measure the dissolved oxygen concentration in the treated water. Then, the hydrogen peroxide concentration in the sample water can be calculated based on these measured dissolved oxygen concentrations in the sample water and the treated water. Therefore, a stable response can be achieved in measuring the hydrogen peroxide concentration in the sample water using a small amount of sample water.

[0036] In the above invention (Invention 3), it is preferable to have a degassing process for the sample water before the sample water collection process (Invention 4).

[0037] According to the invention (invention 4), by pre-degassing the sample water in the degassing process, the concentration of hydrogen peroxide in the sample water can be calculated with higher accuracy.

[0038] The effects of the invention

[0039] According to the present invention, a dissolved oxygen concentration measurement system can be used to measure the dissolved oxygen concentration of sample water and the dissolved oxygen concentration of sample water (treated water) after treatment by a hydrogen peroxide decomposition mechanism without supplying sample water in a continuous manner. The hydrogen peroxide concentration in the sample water can be calculated based on the dissolved oxygen concentrations of the sample water and the treated water. This system provides a hydrogen peroxide concentration measurement system that requires a small amount of sample water and has a stable response. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the hydrogen peroxide concentration measuring system according to one embodiment of the present invention.

[0041] Figure 2 This is a schematic diagram illustrating the procedure for determining the dissolved oxygen concentration of the sample water in the described embodiment.

[0042] Figure 3 This is a schematic diagram illustrating the procedure for measuring the dissolved oxygen concentration of the treated water in the described embodiment.

[0043] Figure 4 This is a schematic diagram illustrating the measurement procedure for determining the dissolved oxygen concentration of sample water using a conventional hydrogen peroxide concentration measurement system.

[0044] Figure 5 This is a schematic diagram illustrating the measurement process for determining the dissolved oxygen concentration in treated water using a conventional hydrogen peroxide concentration measurement system.

[0045] Figure 6 This is a schematic diagram illustrating the measurement procedure for determining the dissolved oxygen concentration of sample water using the hydrogen peroxide concentration determination system of Patent Document 1.

[0046] Figure 7 This is a schematic diagram illustrating the measurement process for determining the dissolved oxygen concentration of treated water using the hydrogen peroxide concentration measurement system described in Patent Document 1.

[0047] Figure 8 This is a schematic diagram illustrating the measurement process for determining the dissolved oxygen concentration of sample water and treated water using the hydrogen peroxide concentration determination system described in Patent Document 2.

[0048] Figure 9 This is a schematic diagram illustrating the measurement procedure for correcting the dissolved oxygen concentration of sample water using the hydrogen peroxide concentration measurement system of Patent Document 2.

[0049] Figure 10 This is a schematic diagram showing the measurement procedure for correcting the dissolved oxygen concentration of treated water using the hydrogen peroxide concentration measurement system of Patent Document 2. Detailed Implementation

[0050] The following is for reference Figures 1-3 This invention will be described in one embodiment. However, the invention is not limited to this embodiment.

[0051] [Hydrogen peroxide concentration measurement system]

[0052] Figure 1 This is a schematic diagram showing the configuration of a hydrogen peroxide concentration measuring system according to one embodiment of the present invention. Figure 1 In this system, the hydrogen peroxide concentration measurement system is connected to a sample water collection pipe 3 at a designated point in the water passage 2, which is connected to the supply source 1 of the treated water (sample water) W in the water treatment process. The sample water collection pipe 3 branches into a first passage 4 and a second passage 5. A first three-way valve 6, serving as a switching mechanism, is installed in the first passage 4, allowing switching between a dissolved oxygen concentration measurement flow path 7 (equipped with a dissolved oxygen meter 8 as a dissolved oxygen concentration measurement mechanism) and a first circulation flow path 9. Furthermore, a second three-way valve 10, also serving as a switching mechanism, is installed in the second passage 5, allowing switching between a hydrogen peroxide decomposition flow path 11 (equipped with a catalyst resin column 12 as a hydrogen peroxide decomposition mechanism) and a second circulation flow path 13.

[0053] A third three-way valve 15 is provided at the end of the dissolved oxygen concentration measuring flow path 7, which can be switched to the discharge pipe 14 side and the second circulation flow path 13. Furthermore, a fourth three-way valve 16 is provided at the end of the hydrogen peroxide decomposition flow path 11, which can be switched to the discharge pipe 14 side and the first circulation flow path 9.

[0054] Furthermore, 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 the flow of sample water W 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.

[0055] The dissolved oxygen meter 8, which serves as the dissolved oxygen concentration measuring device, is adjusted to minimize error within a specified flow rate range; therefore, it is preferable to adjust the flow rate to this range. Thus, a flow meter can be installed downstream of the dissolved oxygen meter. Furthermore, it is preferable to pre-calibrate the dissolved oxygen meter 8 before use.

[0056] For the catalyst resin column 12, it is preferable to use a catalyst resin column filled with a catalyst metal support (platinum group metal catalyst) loaded with platinum group metals. This allows hydrogen peroxide in the water to be treated (sample water) W to come into contact with the platinum group metal catalyst, and the hydrogen peroxide is decomposed through catalyst decomposition. The platinum group metal catalyst is, for example, supported on an anion exchanger. The anion exchanger can also be a granular anion exchange resin.

[0057] [Method for determining hydrogen peroxide concentration]

[0058] Next, the hydrogen peroxide concentration measurement method of this embodiment using the hydrogen peroxide concentration measurement system described above will be explained.

[0059] (Sample water collection process and pathway selection process)

[0060] First, the treated water (sample water) W from the water treatment process is collected by the sample water collection pipe 3 connected to the water passage 2. For the collected sample water W, the water is selected and switched to be supplied to either the first passage 4 or the second passage 5 by closing either the first passage 4 side of the first three-way valve 6 or the second passage 5 side of the second three-way valve 10.

[0061] (Sample water testing procedure)

[0062] In the sample water testing process, such as Figure 2 As shown, the first three-way valve 6 ensures that the first passage 4 and the dissolved oxygen concentration measuring flow path 7 are open, while the first circulation flow path 9 is closed. The second three-way valve 10 closes the second passage 5, while ensuring that the hydrogen peroxide decomposition flow path 11 and the second circulation flow path 13 are open. Furthermore, the third three-way valve 15 ensures that the dissolved oxygen concentration measuring flow path 7 and the second circulation flow path 13 are open, while the discharge pipe 14 is closed. The fourth three-way valve 16 ensures that the hydrogen peroxide decomposition flow path 11 and the discharge pipe 14 are open, while the first circulation flow path 9 is closed.

[0063] In this state, when sample water W collected in sample water collection tube 3 is supplied, the second three-way valve 10 closes the second passage 5 side. Therefore, sample water W flows through the first passage 4 side and flows into the dissolved oxygen concentration measuring flow path 7 via the first three-way valve 6, where the dissolved oxygen concentration (M1) of sample water W is measured in the dissolved oxygen concentration meter 8. Then, the sample water W reaches the third three-way valve 15 located at the end of the dissolved oxygen concentration measuring flow path 7. At this time, the third three-way valve 15 ensures that the dissolved oxygen concentration measuring flow path 7 side and the second circulation flow path 13 side are open, while the discharge pipe 14 side is closed. Therefore, sample water W flows through the second circulation flow path 13 and reaches the second three-way valve 10. Then, it flows from the second three-way valve 10 into the hydrogen peroxide decomposition flow path 11. After the hydrogen peroxide is decomposed by the catalyst resin column 12, the treated water W1 reaches the fourth three-way valve 16 located at the end of the hydrogen peroxide decomposition flow path 11. At this point, the fourth three-way valve 16 ensures that the discharge pipe 14 side is open and the first circulation path 9 side is closed. Therefore, the treated water W1 is discharged from the discharge pipe 14 into the system. The dissolved oxygen concentration (M1) of the sample water W is thus determined.

[0064] (Water treatment testing procedure)

[0065] In the sample water testing process, such as Figure 3As shown, the first three-way valve 6 ensures that the dissolved oxygen concentration measurement flow path 7 and the first circulation flow path 9 are open, while the first passage 4 is closed. The second three-way valve 10 ensures that the second passage 5 and the hydrogen peroxide decomposition flow path 11 are open, while the second circulation flow path 13 is closed. Furthermore, the third three-way valve 15 ensures that the dissolved oxygen concentration measurement flow path 7 and the discharge pipe 14 are open, while the second circulation flow path 13 is closed. The fourth three-way valve 16 ensures that the hydrogen peroxide decomposition flow path 11 and the first circulation flow path 9 are open, while the discharge pipe 14 is closed.

[0066] In this state, when sample water W collected in sample water collection tube 3 is supplied, the first three-way valve 6 closes the first passage 4 side. Therefore, the sample water W collected in sample water collection tube 3 flows through the second passage 5 side, flows into the hydrogen peroxide decomposition flow path 11 via the second three-way valve 10, and after being treated by the catalyst resin column 12, the treated water W1 reaches the fourth three-way valve 14 located at the end of the hydrogen peroxide decomposition flow path 11. At this time, the fourth three-way valve 14 closes the discharge pipe 14 side, ensuring that the first circulation flow path 9 side is open. Therefore, the treated water W1 flows in the first circulation flow path 9 and reaches the first three-way valve 6. Then, it flows from the first three-way valve 6 into the dissolved oxygen concentration measuring flow path 7, and the dissolved oxygen concentration of the treated water W1 is measured in the dissolved oxygen concentration meter 8. Then, the treated water W1 reaches the third three-way valve 15 located at the end of the dissolved oxygen concentration measuring flow path 7. At this time, the third three-way valve 15 ensures that the discharge pipe 14 side is open and the second circulation path 13 side is closed, so the treated water W1 is discharged from the discharge pipe 14 to the outside of the system. The dissolved oxygen concentration (M2) of the treated water W1 is thus measured.

[0067] (Calculation process)

[0068] Then, in order to determine the hydrogen peroxide concentration in the sample water W based on the measured dissolved oxygen concentration M1 of the sample water W and the dissolved oxygen concentration M2 of the treated water W1, the following procedure is performed. That is, firstly, 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). Then, the generated oxygen dissolves in the water and becomes dissolved oxygen.

[0069] 2H₂O₂→2H₂O+O₂ (1)

[0070] Here, the difference between the dissolved oxygen concentration in the treated water W1 and the sample water W is (M2-M1). Therefore, the hydrogen peroxide concentration in the sample water W can be calculated by the following formula (2).

[0071] (M2-M1) × (68 / 32) (2)

[0072] (Here, 68 is the molecular weight of hydrogen peroxide on the left side of equation (1) (because it is 2 molecules, so it is 2 times), 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.)

[0073] It should be noted that in this embodiment, a membrane degassing device is set up earlier than the sampling position of sample water W and a degassing process is performed before the sample water sampling process. By reducing the dissolved oxygen concentration and other dissolved gases in sample water W, the detection accuracy of hydrogen peroxide concentration in sample water W can be further improved.

[0074] As described above, in this embodiment, a single dissolved oxygen meter 8 can be 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 after treatment with the catalyst resin column 12 without splitting the sample water W supply. Then, the hydrogen peroxide concentration in the sample water W can be calculated based on these dissolved oxygen concentrations M1 and M2. Therefore, the amount of sample water W used is small, and since water is continuously supplied to the catalyst resin column 12, it becomes a system for measuring hydrogen peroxide concentration with a stable response.

[0075] The present invention has been described above based on the embodiments described above, but the present invention is not limited to the embodiments described above, and various modifications can be implemented. For example, in the embodiments described above, the treated water measurement step is performed after the sample water measurement step, but these steps can also be reversed in order. In addition, the apparatus for the water treatment process is not particularly limited, and is particularly suitable for apparatuses such as pure water production apparatuses and ultrapure water production apparatuses that require quantitative determination of trace amounts of hydrogen peroxide concentration.

[0076] Example

[0077] The invention will be described in more detail with reference to the following specific embodiments.

[0078] (Example 1)

[0079] Ultrapure water with a hydrogen peroxide concentration adjusted to approximately 15 mg / L was introduced as sample water W into the solution. Figure 1 The hydrogen peroxide concentration measuring system shown measures the hydrogen peroxide concentration.

[0080] It should be noted that the ultrapure water used before adjustment has the following characteristics: resistivity: ≥18.1 MΩ·CM, particles: ≥1000 particles / L with a particle size of ≥50 nm, viable bacteria: ≤1 CFU / L, TOC (TOTAL ORGANIC CARBON): ≤1 MG / L, total silicon: ≤0.1 MG / L, metals: ≤1 NG / L, ions: ≤10 NG / L, and water temperature: 25±2℃.

[0081] First, such as Figure 2 As shown, the first three-way valve 6 ensures that the first passage 4 and the dissolved oxygen concentration measurement flow path 7 are open, while the first circulation flow path 9 is closed. The second three-way valve 10 closes the second passage 5 and ensures that the hydrogen peroxide decomposition flow path 11 and the second circulation flow path 13 are open. Additionally, the third three-way valve 15 ensures that the dissolved oxygen concentration measurement flow path 7 and the second circulation flow path 13 are open, while the discharge pipe 14 is closed. The fourth three-way valve 16 ensures that the hydrogen peroxide decomposition flow path 11 and the discharge pipe 14 are open, while the first circulation flow path 9 is closed. In this state, sample water W is introduced from the first passage 4 into the dissolved oxygen meter 8 and the dissolved oxygen concentration (M1) is measured. Then, the sample water W is introduced into the catalyst resin column 12 for treatment, and the treated water W1 is discharged from the discharge pipe 14 out of the system.

[0082] Then, as Figure 3 The three-way valves are switched as shown. Specifically, the first three-way valve 6 ensures that the dissolved oxygen concentration measurement flow path 7 and the first circulation flow path 9 are open, while the first passage 4 is closed. The second three-way valve 10 ensures that the second passage 5 and the hydrogen peroxide decomposition flow path 11 are open, while the second circulation flow path 13 is closed. Additionally, the third three-way valve 15 ensures that the dissolved oxygen concentration measurement flow path 7 and the discharge pipe 14 are open, while the second circulation flow path 13 is closed. The fourth three-way valve 16 ensures that the hydrogen peroxide decomposition flow path 11 and the first circulation flow path 9 are open, while the discharge pipe 14 is closed. In this state, after the sample water W is treated by the catalyst resin column 12 in the second passage 5, the treated water W1 flows into the dissolved oxygen concentration measurement flow path 7 via the first circulation flow path 9, is introduced into the dissolved oxygen meter 8, and the dissolved oxygen concentration (M2) is measured. Then, the treated water W1 is discharged from the system through the discharge pipe 14.

[0083] The dissolved oxygen concentrations (M1) of the sample water W and the dissolved oxygen concentrations (M2) of the treated water W1 were thus measured and remained stable. Based on these values, the hydrogen peroxide concentration of the sample water W was calculated to be close to 15 mg / L. Furthermore, during the operation of the hydrogen peroxide concentration measurement system in Example 1, the flow rate of the sample water W was 1 L / min, and the measurement time was 2 minutes / cycle.

[0084] (Comparative Example 1)

[0085] use Figure 4 and Figure 5 The hydrogen peroxide concentration determination system shown was used to determine the hydrogen peroxide concentration using the same sample water W as in Example 1.

[0086] First, such as Figure 4 As shown, ensure that the first on / off valve 39 is open and the second on / off valve 40 is closed to supply sample water W to the first passage 34, thereby measuring the dissolved oxygen concentration (M1) of sample water W using dissolved oxygen meter 37. Then, as... Figure 5 As shown, the first on / off valve 39 was closed and the second on / off valve 40 was ensured to be open. The sample water W was introduced into the catalyst resin column 38 for treatment. The dissolved oxygen concentration (M2) in the treated water W1 was measured using a dissolved oxygen meter 37.

[0087] For the dissolved oxygen concentrations (M1) of sample water W and (M2) of treated water W1 measured in this way, at least 2 minutes are required before the dissolved oxygen concentration (M2) of treated water W1 stabilizes, and time is also required before the hydrogen peroxide concentration of sample water W can be calculated with high accuracy. This can be attributed to the fact that, since the water supply to the catalyst resin column 38 is initially stopped, time is required until the response stabilizes. Furthermore, during the operation of the hydrogen peroxide concentration measurement system in Comparative Example 1, the flow rate of sample water W was 1 L / min, and the measurement time was 10 minutes / cycle.

[0088] (Comparative Example 2)

[0089] use Figure 6 and Figure 7 The hydrogen peroxide concentration determination system shown was used to determine the hydrogen peroxide concentration using the same sample water W as in Example 1.

[0090] First, such as Figure 6 As shown, with the first on / off valve 57 and the second on / off valve 61 open and the first connecting valve 63 and the second connecting valve 65 closed, sample water W is supplied from the sample water collection tube 53 to the first passage 54 and the second passage 58, thereby measuring the dissolved oxygen concentration (M1) of the sample water W in the first passage 54 using a dissolved oxygen concentration meter 56. During this period, sample water W is also supplied to the second passage 58 and then discharged after being passed through the catalyst resin column 60.

[0091] Then, as Figure 7 As shown, with the first on / off valve 57 and the second on / off valve 61 closed and the first connecting pipe 62 and the second connecting pipe 64 ensured to be open, sample water W is supplied from the sample water collection pipe 53 to the first passage 54 and the second passage 58. Thus, the sample water W in the second passage 58, after being treated with the catalyst resin column 60, is introduced through the second connecting pipe 64 from the dissolved oxygen concentration measuring unit 55 of the first passage 53 to the dissolved oxygen concentration meter 56, where the dissolved oxygen concentration (M2) is measured. During this period, sample water W is also supplied to the first passage 54 and discharged from the discharge unit 59 via the first connecting pipe 62.

[0092] The dissolved oxygen concentrations (M1) of the sample water W and the dissolved oxygen concentrations (M2) of the treated water W1 measured in this way were stable. The hydrogen peroxide concentration of the sample water W calculated from these values ​​was to the same extent as in Example 1, close to 15 mg / L. In addition, during the operation of the hydrogen peroxide concentration measurement system in Comparative Example 2, the flow rate of the sample water W was 2 L / min, and the measurement time was 2 minutes / cycle.

[0093] (Comparative Example 3)

[0094] use Figure 8 The hydrogen peroxide concentration determination system shown was used to determine the hydrogen peroxide concentration using the same sample water W as in Example 1.

[0095] First, such as Figure 8 As shown, with the first on / off valve 76 and the second on / off valve 80 open and the connecting valve 82 closed, sample water W is supplied from the sample water collection pipe 73 to the first passage 74 and the second passage 77. The dissolved oxygen concentration M1 of the sample water W in the first passage 74 is measured using a first dissolved oxygen meter 75. Additionally, the sample water W in the second passage 77 is treated using a catalyst resin column 78, and the dissolved oxygen concentration M2 of this treated water W1 is measured using a second dissolved oxygen meter 79.

[0096] Although the dissolved oxygen concentrations (M1) of the sample water W and the dissolved oxygen concentrations (M2) of the treated water W1 measured in this way were stable, the hydrogen peroxide concentration of the sample water W calculated from these values ​​had a larger error compared with that of Example 1, Comparative Example 1, and Comparative Example 2. This can be attributed to the error between the first dissolved oxygen meter 75 and the second dissolved oxygen meter 79. Furthermore, during the operation of the hydrogen peroxide concentration measurement system in Comparative Example 3, the flow rate of the sample water W was 2 L / min, and the measurement time was 1 minute / cycle.

[0097] It should be noted that in Comparative Example 3, such as Figure 9 and Figure 10 As shown, sample water W is supplied simultaneously to both the first dissolved oxygen concentration meter 75 and the second dissolved oxygen concentration meter 79, and then treated water W1 is supplied simultaneously. The error between the two is corrected based on the difference between the measured values ​​of the first dissolved oxygen concentration meter 75 and the second dissolved oxygen concentration meter 79, thereby improving the accuracy of hydrogen peroxide concentration calculation. In this case, the measurement time of sample water W is about three times longer than that of the hydrogen peroxide concentration measurement system in Comparative Example 3.

[0098] The flow rate, measurement time, and number of constituent devices (number of catalyst resin columns + number of dissolved oxygen concentration meters) of the sample water W in Examples 1 and Comparative Examples 1 to 3 are shown in Table 1.

[0099] Table 1

[0100] As shown in Table 1, the hydrogen peroxide concentration determination system of Example 1 has the best overall performance, with a small flow rate of sample water W and a short measurement time, as well as a small number of components.

[0101] Explanation of reference numerals in the attached figures

[0102] 1: The supply source of the treated water (sample water) W in the treatment process.

[0103] 2: Waterway.

[0104] 3: Sample water collection tube.

[0105] 4: First pathway.

[0106] 5: Second pathway.

[0107] 6: First three-way valve.

[0108] 7: Dissolved oxygen concentration measurement flow path.

[0109] 8: Dissolved oxygen concentration meter (dissolved oxygen concentration measuring device).

[0110] 9: First circulation path.

[0111] 10: Second three-way valve.

[0112] 11: Hydrogen peroxide decomposition flow path.

[0113] 12: Catalyst resin column (hydrogen peroxide decomposition mechanism).

[0114] 13: First circulation path.

[0115] 14: Discharge pipe.

[0116] 15: Third three-way valve.

[0117] 16: Fourth three-way valve.

Claims

1. A hydrogen peroxide concentration measuring system, which is used to measure the hydrogen peroxide concentration in sample water collected at a specified location in the water passage of a water treatment process, wherein, The hydrogen peroxide concentration determination system includes a sample water collection tube for collecting the sample water. The sample water collection tube branches into a first passage and a second passage. The first pathway is configured in a switchable manner, including a dissolved oxygen concentration measuring flow path and a first circulation flow path. The second pathway is configured in a switchable manner with a hydrogen peroxide decomposition flow path and a second circulation flow path. The hydrogen peroxide decomposition flow path branches into a discharge pipe and a first circulation flow path in a switchable manner. On the other hand, the dissolved oxygen concentration measurement flow path branches into a discharge pipe and a second circulation flow path in a switchable manner. The hydrogen peroxide concentration measurement system is configured to allow the sample water to flow continuously from the dissolved oxygen concentration measurement unit to the hydrogen peroxide decomposition unit, or from the hydrogen peroxide decomposition unit to the dissolved oxygen concentration measurement unit.

2. The hydrogen peroxide concentration measuring system as described in claim 1, wherein, A membrane degassing device is located further forward of the water sampling point in the water passage of the water treatment process.

3. A method for determining hydrogen peroxide concentration, comprising determining the concentration of hydrogen peroxide in sample water collected at a specified location in the water flow path of a water treatment process, wherein, The method for determining hydrogen peroxide concentration includes: The sample water collection process involves collecting sample water at a designated location along the water flow path of the water treatment process. The process of selecting a pathway involves supplying the collected sample water to either a first pathway or a second pathway. The first pathway is configured to be switchable, consisting of a hydrogen peroxide decomposition flow path with a hydrogen peroxide decomposition mechanism and a first circulation flow path. The second pathway is configured to be switchable, consisting of a dissolved oxygen concentration measuring flow path with a dissolved oxygen concentration measuring mechanism and a first circulation flow path. The sample water determination process involves introducing sample water into the first channel side during the channel selection process, determining the dissolved oxygen concentration in the sample water using a dissolved oxygen concentration measuring device, and then passing the sample water through a hydrogen peroxide decomposition device and discharging it. The treated water measurement step involves introducing sample water into the second channel side during the channel selection step and treating it using a hydrogen peroxide decomposition mechanism to obtain treated water. The treated water is then introduced into the dissolved oxygen concentration measurement mechanism to measure the dissolved oxygen concentration in the treated water. The calculation process involves determining the hydrogen peroxide concentration in the sample water based on the dissolved oxygen concentration in the sample water and the dissolved oxygen concentration in the treated water.

4. The method for determining hydrogen peroxide concentration as described in claim 3, wherein, A degassing process for the sample water is performed before the sample water collection process.

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