JP2021127996A - Pretreatment method, pretreatment device, urea concentration measurement method, urea concentration measurement device, ultrapure water production method and ultrapure water production system - Google Patents

Abstract

To measure easily and with high accuracy the urea concentration of the liquid to be measured.SOLUTION: Before measuring the total organic carbon content of a liquid to be measured with a total organic carbon meter, ultraviolet rays are irradiated to the liquid to be measured with irradiation energy that does not decompose urea but decomposes organic substances other than urea.SELECTED DRAWING: Figure 1

Description

The present application relates to a pretreatment method, a pretreatment apparatus, a urea concentration measuring method, a urea concentration measuring apparatus, an ultrapure water production method, and an ultrapure water production system.

In recent years, in pure water used in a semiconductor manufacturing process, it has been required to reduce the concentration of total organic carbon (TOC) to the order of ppb. There are various organic components (hereinafter referred to as "TOC components") that serve as carbon sources for TOC, but it is known that urea is a compound that is difficult to remove among these TOC components.

For example, in the production of pure water, as means for reducing TOC in raw water by means such as separation, adsorption, and decomposition, there are a reverse osmosis membrane device, an ion exchange device, an ultraviolet oxidizing device, and the like. The removal rate of urea was not always sufficient even when the above devices were used alone or in combination. Therefore, in the production of pure water, for example, oxidative decomposition by adding an oxidizing agent is being studied as a method for decomposing and removing urea in water to be treated such as raw water.

In such a method for producing pure water, it has been required to measure the urea concentration in raw water or the obtained pure water easily and accurately in order to efficiently decompose and remove urea. That is, it is economical if the concentration of urea contained in the raw water or the obtained pure water can be obtained in a short time and at low cost, and the decomposition method can be adjusted accordingly, for example, the amount of the oxidizing agent to be added can be adjusted. And productivity can be expected to improve significantly. Therefore, there is a demand for a method of continuously and accurately measuring and monitoring the urea concentration of raw water and pure water flowing through a pure water production line.

Here, the urea concentration in the raw water used for pure water production is approximately 0.3 ppm or less. In order to measure the urea concentration of such a low concentration sample water, it has been necessary to use a means having low accuracy and / or having difficulty in convenience and economy.

Patent Document 1 includes a urea monitoring device including an ion removing means for removing ions in the test water and a TOC concentration measuring means for specifying the TOC concentration of the test water from which ions have been removed by the ion removing means. Is described.

Patent Document 2 describes a urea analyzer including a high performance liquid chromatograph including a cation exchange column, which has an ion removing means in front of the high performance liquid chromatograph.

According to Patent Document 3, in analyzing the urea concentration in the sample water, the sample water is brought into contact with a mixed resin in which a cation exchange resin and an anion exchange resin are mixed, and then distilled and concentrated to obtain urea in the obtained concentrated water. A method for analyzing urea is described.

Patent Document 4 describes the conductivity after a lapse of time when the gas in the sample solution in the reactor is absorbed by the absorbing solution and the conductivity becomes in an equilibrium state, and the organic compound in the sample solution is oxidized. A method for determining the total amount of organic carbon in the sample liquid from the difference between the conducted carbon dioxide absorbed by the absorbing liquid and the time after which the conductivity reaches an equilibrium state is described.

Japanese Unexamined Patent Publication No. 2019-191099 JP-A-2019-191100 Japanese Unexamined Patent Publication No. 8-192154 Japanese Unexamined Patent Publication No. 2006-90732

For example, as described in Patent Document 4, in the method using a total organic carbon meter, the concentration of organic carbon other than urea is also measured, so that it is difficult to accurately measure the concentration of urea. Further, the method described in Patent Document 1 also measures the concentration of organic carbon other than urea excluding ions, and it is also difficult to accurately measure the urea concentration.

When a chromatograph is used for measurement as described in Patent Document 2, the analysis is not simple, takes time, and costs money. Further, the use of distillation concentration as described in Patent Document 3 also requires a large-scale device and is costly. Therefore, there is still room for improvement in the simpler and more accurate measurement of urea concentration.

The purpose of the present application is to measure the urea concentration of the liquid to be measured easily and with high accuracy.

As a result of sincere studies, the inventors have found that urea and other organic substances have significantly different decomposition rates due to ultraviolet (UV) irradiation, and that this can be used for urea analysis, and completed the invention.

In the pretreatment method of the liquid to be measured in the first aspect, urea is not decomposed with respect to the liquid to be measured and organic substances other than urea are decomposed in the stage before measuring the total organic carbon amount of the liquid to be measured by the total organic carbon meter. Irradiate ultraviolet rays with the irradiation energy.

In this pretreatment method, the liquid to be measured is irradiated with ultraviolet rays before the total amount of organic carbon in the liquid to be measured is measured by a total organic carbon meter. The irradiation energy of this ultraviolet ray is the irradiation energy that decomposes organic substances other than urea without decomposing urea contained in the liquid to be measured. Therefore, when the total organic carbon amount of the liquid to be measured is measured by the total organic carbon meter after irradiation with ultraviolet rays, the amount of organic substances other than urea can be measured, and the amount of urea alone can be measured. As a result, the urea concentration of the liquid to be measured can be measured with high accuracy. Moreover, since it is only necessary to irradiate the measurement target liquid with ultraviolet rays before measuring the total organic carbon amount of the measurement target liquid with the total organic carbon meter, it is easy to measure the urea concentration of the measurement target liquid.

In the present application, the term "does not decompose" or "does not decompose" urea is not limited to the case where it does not decompose at all. That is, in principle, it is impossible to prevent the urine level from being decomposed at all despite the irradiation with ultraviolet rays, and even if the irradiation energy of ultraviolet rays is weak, a very small amount of urea is decomposed. be. However, urea is not substantially decomposed, and organic substances other than urea are relatively decomposed. Therefore, when the total organic carbon amount of the solution to be measured is measured by a total organic carbon meter after this pretreatment method, urea is used. If ultraviolet rays are irradiated with irradiation energy that can contribute to simple and highly accurate measurement of concentration, it is included in the case of "not decomposing" urea.

In the second aspect, in the first aspect, the irradiation energy of the ultraviolet rays is 0.1 Wh / L or more and 20 Wh / L or less per unit volume of the liquid to be measured.

By setting the irradiation energy of ultraviolet rays in this way, it is possible to surely realize a configuration in which urea is not decomposed with respect to the liquid to be measured but organic substances other than urea are decomposed.

In the pretreatment apparatus for the liquid to be measured in the third aspect, urea is provided on the upstream side of the flow of the liquid to be measured with respect to the total organic carbon meter for measuring the total organic carbon amount of the liquid to be measured. Irradiates ultraviolet rays with irradiation energy that decomposes organic substances other than urea without decomposing.

This pretreatment device is provided on the upstream side of the flow of the liquid to be measured with respect to the total organic carbon meter for measuring the total organic carbon amount of the liquid to be measured. Then, this pretreatment device irradiates the measurement target liquid with ultraviolet rays with irradiation energy that does not decompose urea but decomposes organic substances other than urea. Therefore, when the total organic carbon amount of the liquid to be measured is measured by the total organic carbon meter on the downstream side of the pretreatment apparatus, the amount of organic substances other than urea can be measured, and the amount of urea alone can be measured. As a result, the urea concentration of the liquid to be measured can be measured with high accuracy. Moreover, since it is only necessary to irradiate the measurement target liquid with ultraviolet rays by a pretreatment device on the upstream side of the total organic carbon meter, it is easy to measure the urea concentration of the measurement target liquid.

In the urea concentration measuring method of the fourth aspect, the measurement target liquid is irradiated with ultraviolet rays with irradiation energy that does not decompose urea but decomposes organic substances other than urea, and the measurement target liquid in which the organic substances other than urea are decomposed is irradiated with ultraviolet rays. On the other hand, the total amount of organic carbon is measured by a total organic carbon meter.

In this urea concentration measuring method, the liquid to be measured is irradiated with ultraviolet rays. The irradiation energy of this ultraviolet ray is the irradiation energy that decomposes organic substances other than urea without decomposing urea contained in the liquid to be measured. After that, the total amount of organic carbon is measured with a total organic carbon meter for the liquid to be measured in which organic substances other than urea are decomposed. Therefore, when measuring, the amount of organic substances other than urea is not measured, only the amount of urea. Can be measured. As a result, the urea concentration of the liquid to be measured can be measured with high accuracy. Moreover, since it is only necessary to irradiate the measurement target liquid with ultraviolet rays before measuring the total organic carbon amount of the measurement target liquid with the total organic carbon meter, it is easy to measure the urea concentration of the measurement target liquid.

In the urea concentration measuring device of the fifth aspect, the pretreatment device that irradiates the liquid to be measured with ultraviolet rays with irradiation energy that does not decompose urea but decomposes organic substances other than urea, and the pretreatment device that irradiates the ultraviolet rays to the above. It has a total organic carbon meter that measures the total amount of organic carbon with respect to the liquid to be measured in which the organic matter other than urea is decomposed.

In this urea concentration measuring device, the pretreatment device irradiates the liquid to be measured with ultraviolet rays. The irradiation energy of this ultraviolet ray is the irradiation energy that decomposes organic substances other than urea without decomposing urea contained in the liquid to be measured. After that, the total organic carbon amount is measured by the total organic carbon meter with respect to the liquid to be measured in which organic substances other than urea are decomposed. Therefore, when measuring, the amount of organic substances other than urea is not measured, only the amount of urea. Can be measured. As a result, the urea concentration of the liquid to be measured can be measured with high accuracy. Moreover, it is only necessary to provide a pretreatment device on the upstream side of the flow of the liquid to be measured and irradiate the liquid to be measured with ultraviolet rays before measuring the total organic carbon amount of the liquid to be measured by the total organic carbon meter. , It is easy to measure the urea concentration of the liquid to be measured.

In the method for producing ultrapure water according to the sixth aspect, ultrapure water is generated by treating raw water, the ultrapure water is sent to a point of use where the ultrapure water is used, and any of the raw water to the ultrapure water is used. The liquid to be measured is the liquid to be measured, and the liquid to be measured is irradiated with ultraviolet rays with irradiation energy that does not decompose urea but decomposes organic substances other than urea, and the organic matter other than urea is decomposed. On the other hand, the total amount of organic carbon is measured by a total organic carbon meter.

In this ultrapure water production method, in the ultrapure water production process, ultrapure water is produced by treating raw water. In addition, the ultrapure water production process sends the produced ultrapure water to the point of use in which it is used.

Further, in this ultrapure water production method, a liquid at any stage from raw water to ultrapure water in the ultrapure water production process is used as the liquid to be measured. Then, the liquid to be measured is irradiated with ultraviolet rays. The irradiation energy of this ultraviolet ray is the irradiation energy that decomposes organic substances other than urea without decomposing urea contained in the liquid to be measured. After that, the total amount of organic carbon is measured with a total organic carbon meter for the liquid to be measured in which organic substances other than urea are decomposed. Therefore, when measuring, the amount of organic substances other than urea is not measured, only the amount of urea. Can be measured. As a result, the urea concentration of the liquid to be measured can be measured with high accuracy. Moreover, since it is only necessary to irradiate the measurement target liquid with ultraviolet rays before measuring the total organic carbon amount of the measurement target liquid with the total organic carbon meter, it is easy to measure the urea concentration of the measurement target liquid.

In the ultrapure water production system of the seventh aspect, an ultrapure water production apparatus that generates ultrapure water by treating raw water and sends the ultrapure water to a point of use where the ultrapure water is used, and the ultrapure water production. A pretreatment device that uses the liquid at any stage from the raw water to the ultrapure water in the device as the liquid to be measured, and irradiates the measurement target liquid with ultraviolet rays with irradiation energy that does not decompose urea but decomposes organic substances other than urea. And a total organic carbon meter that measures the total organic carbon amount of the measurement target liquid in which the organic substances other than the urea are decomposed by the irradiation of the ultraviolet rays by the pretreatment apparatus.

In this ultrapure water production system, the ultrapure water production apparatus produces ultrapure water by treating raw water. In addition, the ultrapure water production equipment sends the generated ultrapure water to the point of use in which it is used.

The pretreatment equipment uses the liquid at any stage from raw water to ultrapure water in the ultrapure water production equipment as the liquid to be measured. Then, the liquid to be measured is irradiated with ultraviolet rays. The irradiation energy of this ultraviolet ray is the irradiation energy that decomposes organic substances other than urea without decomposing urea contained in the liquid to be measured. After that, the total organic carbon amount is measured by the total organic carbon meter with respect to the liquid to be measured in which organic substances other than urea are decomposed. Therefore, when measuring, the amount of organic substances other than urea is not measured, only the amount of urea. Can be measured. As a result, the urea concentration of the liquid to be measured can be measured with high accuracy. Moreover, since it is only necessary to irradiate the measurement target liquid with ultraviolet rays before measuring the total organic carbon amount of the measurement target liquid with the total organic carbon meter, it is easy to measure the urea concentration of the measurement target liquid.

In the eighth aspect, in the seventh aspect, the ultrapure water production apparatus produces the primary pure water by the primary treatment of the raw water, and the ultrapure water by the secondary treatment of the primary pure water. It has a secondary pure water device to be generated, and the pretreatment device and the total organic carbon meter are provided between the secondary pure water device and the use point.

The ultrapure water production device generates primary pure water from raw water by a primary pure water device, and produces ultrapure water from primary pure water by a secondary pure water device.

A pretreatment device and a total organic carbon meter will be installed between the secondary pure water device and the point of use. That is, the urea concentration can be measured by using the ultrapure water generated through the secondary pure water device as the measurement target liquid.

In the present application, the urea concentration of the liquid to be measured can be measured easily and with high accuracy.

FIG. 1 is a configuration diagram showing an ultrapure water production system including a urea concentration measuring device including the pretreatment device of the first embodiment. FIG. 2 is a graph showing the relationship between the irradiation energy of ultraviolet rays on organic matter and the decomposition rate. FIG. 3 is a configuration diagram showing an ultrapure water production system including a urea concentration measuring device including the pretreatment device of the second embodiment.

Hereinafter, the urea concentration measuring device 12 of the first embodiment and the ultrapure water production system 16 provided with the urea concentration measuring device 12 will be described with reference to the drawings.

The ultrapure water production system 16 includes an ultrapure water production apparatus 14 for producing ultrapure water and a liquid to be treated (from raw water to ultrapure water) in the process of producing ultrapure water in the ultrapure water production apparatus 14. The urea concentration measuring device 12 for measuring the urea concentration of the liquid) is included.

The ultrapure water production device 14 includes a pretreatment device 18, a primary pure water device 20, a pure water tank 28, a secondary pure water device 30, and a use point 40. In the first embodiment, in particular, the urea concentration measuring device 12 is installed on the upstream side of the pretreatment device 18, and the urea concentration of the raw water can be measured.

The urea concentration measuring device 12 includes a filtration device 50, an ultraviolet irradiation device 52, a weak acid removing device 55, and a total TOC 54. Further, the TOC meter 54 has a decarboxylation device 56, an oxidation device 58, a CO ₂ detection device 60, and a CO ₂ detection device 62. In the present embodiment, the urea concentration measuring device 12 is a device that uses raw water as a measurement target liquid and measures the concentration of urea contained in the measurement target liquid. Urea exists as a part of organic matter. Further, the liquid to be measured is not limited to raw water, and as in the second embodiment described later, the ultrapure water obtained by the secondary pure water apparatus 30 and other intermediates of the ultrapure water production apparatus 14 The liquid obtained in the step can be used as the liquid to be measured.

The filtration device 50 reduces the concentration of an organic substance other than urea when the solution to be measured contains an organic substance other than urea in a high concentration by, for example, a reverse osmosis membrane (RO) or the like. Examples of the filtration device 50 include an ultrafiltration membrane (UF), a nanofiltration membrane (NF), a microfiltration membrane (MF), an ion exchange device, and the like, in addition to the reverse osmosis membrane (RO).

As a result, by setting the concentration of organic substances other than urea in the liquid to be measured to, for example, 10 ppb or less, the burden on the device in the subsequent steps can be reduced, and the urea concentration measuring device 12 can be used stably.

If it can be considered that the concentration of organic substances other than urea contained in the liquid to be measured is sufficiently low, the filtration device 50 may be omitted.

Here, depending on the components contained in the liquid to be measured, for example, a filtration device 50 that is resistant to deterioration due to the components is selected, an operation for removing the components is added, and then the filtration device 50 is supplied. Is preferable.

For example, when the measurement target liquid contains chlorine, select a filtration device 50 that is resistant to deterioration due to chlorine, and remove chlorine by passing activated carbon, for example, before supplying the measurement target liquid to the filtration device 50. It is preferable to take measures such as.

The ultraviolet irradiation device 52 decomposes organic substances by irradiating the liquid to be measured with ultraviolet rays. Here, FIG. 2 schematically shows the relationship between the irradiation energy of ultraviolet rays for organic substances and the decomposition rate. In FIG. 2, the alternate long and short dash line indicates an organic substance other than urea, and the alternate long and short dash line indicates urea. There is a range E1 of irradiation energy in which the decomposition rate of organic substances other than urea and the decomposition rate of urea are significantly different. This range E1 is a range of irradiation energies in which urea is not substantially decomposed and organic substances other than urea are decomposed. Further, in the range E2 of the irradiation energy higher than this range E1, the decomposition rate of organic substances other than urea and the decomposition rate of urea are both close to 100%.

The decomposition rate is a value obtained by the following equation, and is obtained on a carbon basis.
Decomposition rate = target substance concentration in the measurement target liquid after irradiation by the ultraviolet irradiation device 52 / target substance concentration in the measurement target liquid before irradiation by the ultraviolet irradiation device 52 However, the target substance is urea or other than urea. Amount of organic substances in the liquid to be measured

The irradiation energy of the ultraviolet rays irradiated by the ultraviolet irradiation device 52 is the irradiation energy (for example, the range E1 in FIG. 2) that decomposes organic substances other than urea among the organic substances contained in the liquid to be measured. As an example, the irradiation energy of ultraviolet rays is 0.1 Wh / L or more and 20 Wh / L or less per unit volume of the liquid to be measured.

When ultraviolet rays are irradiated by the ultraviolet irradiation device 52, organic substances other than urea are decomposed, carbon dioxide is generated in the measurement target liquid via, for example, carboxylic acid as an intermediate product, and carbon dioxide is generated in the measurement target liquid as carbonic acid. It becomes the state that exists in.

The ultraviolet irradiation by the ultraviolet irradiation device 52 is a process performed before the measurement of the concentration of total organic matter in the TOC meter 54, and is an example of a pretreatment method. The ultraviolet irradiation device 52 is an example of a pretreatment device.

Here, when the irradiation energy of ultraviolet rays by the ultraviolet irradiation device 52 is sufficiently high, for example, in the vicinity of the upper limit of the range E1 in FIG. 2 (for example, 2 to 20 Wh / L), substantially all organic substances other than urea are up to carbon dioxide. Can be disassembled. On the other hand, when the irradiation energy is sufficiently low (for example, 0.1 to 0.5 Wh / L near the lower limit of the range E1 in FIG. 2), substantially all organic substances other than urea are in the state of intermediate products. Will remain in. In this case, the irradiation energy is preferable from the viewpoint of suppressing urea decomposition in the ultraviolet irradiation device 52 as much as possible. Further, when the irradiation energy of ultraviolet rays is between the two (for example, 0.5 to 2 Wh / L near the center of the range E1 in FIG. 2), both carbon dioxide and the intermediate product are mixed.

It is also possible to add an oxidizing agent to the measurement target liquid before supplying the measurement target liquid to the ultraviolet irradiation device 52. Examples of the oxidizing agent include hypobromous acid and / or a salt thereof, hypochlorous acid and / or a salt thereof, persulfate and / or a salt thereof, hydrogen peroxide and the like. When any of the oxidizing agents is used, the concentration and the amount of the oxidizing agent added, and the irradiation energy of the ultraviolet irradiation device 52 may be appropriately adjusted to obtain a preferable decomposition rate. In this case, it is possible to suppress the irradiation energy required by the ultraviolet irradiation device 52.

The weak acid removing device 55 is a device that removes the weak acid from the liquid to be measured in which the weak acid remains. A membrane filtration device using RO) can be mentioned. As shown in FIG. 1, by providing the weak acid removing device 55 between, for example, the ultraviolet irradiation device 52 and the TOC total 54, the weak acid can be removed before the measurement target liquid reaches the TOC total 54.

The weak acid removing device 55 can remove the above-mentioned intermediate products and carbonic acid. While carbonic acid can be removed by the decarboxylation device 56 described later, the weak acid removing device 55 is often suitable for removing the intermediate product, and therefore, from the viewpoint of effectively removing the intermediate product. Is preferably configured to have a weak acid removing device 55. On the other hand, from the viewpoint of efficiently removing carbonic acid, further improving the accuracy of urea concentration measurement, and stable operation over a long period of time, it is preferable to have a configuration having a decarboxylation device 56.

The weak acid removing device 55 and the decarboxylation device 56 may be appropriately selected according to the amount and ratio of carbon dioxide and intermediate products generated by the ultraviolet irradiation device 52. The weak acid removing device 55 and the decarboxylation device 56 may be installed in combination.

Further, when the irradiation energy of ultraviolet rays by the ultraviolet irradiation device 52 is sufficiently high and substantially all the organic substances other than urea are decomposed to carbon dioxide, it can be operated only by the decarboxylation device 56, and the configuration can be improved. It can be done easily.

The pH may be adjusted if necessary before supplying the liquid to be measured to the weak acid removing device 55. For example, when a membrane filtration device using a reverse osmosis membrane (RO) is used, it is preferable that the liquid to be measured is medium to alkaline (for example, the pH is 7 or more) because the removal rate of intermediate products and carbon dioxide increases. The pH can be adjusted, for example, by adding a known base. Further, when a reverse osmosis membrane (RO) or an ion exchange device is used for the above-mentioned filtration device 50, if hydrogen ions are present in the liquid to be measured, they can be removed, so that at least a part of the pH adjustment is performed. Can also be carried.

In the case of the configuration having the decarboxylation device 56, the configuration of the urea concentration measuring device 12 can be simplified by using the one built in the TOC meter 54.

The decarboxylation device 56 of the TOC meter 54 removes carbonic acid from the liquid to be measured by using, for example, a hollow fiber (vacuum degassing) module. Specifically, after adding phosphoric acid to the liquid to be measured, it is permeated through a gas permeable membrane in a state where one side is evacuated. In particular, in the present embodiment, when the ultraviolet irradiation device 52 arranged on the upstream side of the decarboxylation device 56 causes an increase in carbonation in the liquid to be measured, the amount of the increased carbonation is decarboxylated. It can be reduced by device 56. By removing carbonic acid from the liquid to be measured, the ratio of urea as an organic substance in the liquid to be measured is increased.

If the concentration of carbon dioxide in the liquid to be measured sent to the TOC meter 54 is low and the _{effect on the detection of CO 2} is small, the removal of carbon dioxide by the decarboxylation device 56 may be omitted.

Further, as the TOC total 54, one having a configuration that does not have the decarboxylation device 56 may be used. In this case, if it is necessary to remove carbonic acid from the liquid to be measured, for example, a decarboxylation device 56 may be provided between the ultraviolet irradiation device 52 and the TOC total 54. An example of such a decarboxylation device 56 is a degassing device, and a vacuum degassing membrane, a degassing tower, a vacuum degassing tower, and the like can be considered, but a vacuum degassing membrane is preferable.

The pH may be adjusted if necessary before supplying the liquid to be measured to the decarboxylation device 56. When the decarboxylator is applied to the decarboxylation device 56, it is preferable to make the liquid to be measured acidic (for example, the pH is 5 or less) because the carbonation removal rate increases. The pH can be adjusted, for example, by adding a known acid. Further, when a reverse osmosis membrane (RO) or an ion exchange device is used for the above-mentioned filtration device 50, if there is a hydroxide ion in the liquid to be measured, it can be removed, so at least the pH adjustment can be performed. You can also take part in it.

Inside the TOC meter 54, the flow path of the liquid to be measured is branched downstream of the decarboxylation device 56, and the oxidation device 58 and the CO ₂ detection device 60 are provided in one flow path and the other flow. A CO ₂ detection device 62 is provided on the road.

The oxidizing device 58 of the TOC meter 54, for example, irradiates the measurement target liquid with ultraviolet rays to oxidize the organic substances contained in the measurement target liquid, including urea. Substantially, most of the components other than urea have been removed from the organic substances contained in the liquid to be measured, so that the organic substances oxidized by the oxidizing apparatus 58 are urea. That is, in the oxidizing apparatus 58, urea in the liquid to be measured is oxidatively decomposed, and carbon dioxide is generated again at this stage.

_{The CO 2} detectors 60 and 62 of the TOC meter 54 measure the amount of carbon dioxide in the liquid to be treated. The amount of carbon dioxide is proportional to the amount of carbon contained in the organic matter in the oxidatively decomposed liquid to be measured.

Here, on the upstream side of the CO ₂ detection device 60, the organic matter in the measurement target liquid is oxidized by the oxidation device 58, and the CO ₂ detection device 60 detects the total carbon concentration of the measurement target liquid. On the other hand, _{on the upstream side of the CO 2} detection device 62, the organic matter in the measurement target liquid is not oxidized by the oxidizing device 58, and the CO ₂ detection device 62 detects the inorganic carbon concentration of the measurement target liquid. In the TOC total 54, as shown in the following formula (1), _{the total carbon concentration detected by the CO 2} detection device 60 is subtracted from the total carbon concentration detected by the CO ₂ detection device 62 to reduce the total amount of the solution to be measured. Obtain the organic carbon concentration.
Total organic carbon concentration = Total carbon concentration-Inorganic carbon concentration (1)

For example, when the organic matter removal rate of the filtration device 50 and the carbonation removal rate of the decarboxylation device 56 are large, a part of urea may be removed by the time it reaches the oxidizing device 58 of the TOC total 54. In such a case, if these urea removal rates are investigated in advance and the urea concentration measurement result by the TOC meter 54 is corrected accordingly, the urea concentration can be obtained more accurately.

Further, the specific configuration of the TOC meter 54 is not limited to the above, and various TOC meters can be used in the present embodiment.

The liquid to be treated after measuring the total organic carbon concentration with the TOC meter 54 may be discarded as a drainage liquid, or may be returned to the pure water tank 28, for example.

As described above, in the present embodiment, when the urea concentration in the liquid to be measured is detected by using the TOC meter 54, a preliminary treatment for removing organic substances other than urea is performed in the previous step. As a result, the accuracy of measuring the urea concentration using the TOC meter 54 is improved. Moreover, since it is only necessary to irradiate the measurement target liquid with ultraviolet rays by the ultraviolet irradiation device 52 before measuring the total organic carbon concentration by the TOC meter 54, it is easy to measure the urea concentration of the measurement target liquid.

The urea concentration measurement process in the TOC meter 54 may be a continuous method performed while continuously flowing the measurement target liquid, or may be a batch type performed by temporarily storing the measurement target liquid.

Even when the urea concentration measuring process in the TOC meter 54 is a batch type, the urea concentration measuring device 12 may be supplied with the liquid to be measured more frequently or continuously than the measurement. Further, a larger flow rate of the liquid to be measured may be supplied, which is required for the urea concentration measuring process in the TOC meter 54. In that case, the liquid to be measured that is not supplied to the TOC total 54 may be discharged from, for example, a drainage pipe provided immediately before the TOC total 54.

By supplying the liquid to be measured to the pipe with a large flow rate and / and frequently or continuously, it is possible to suppress the generation of bacteria and the adhesion of organic substances on the side wall of the pipe. The generated bacteria and attached organic substances may be separated from the side wall at an unexpected timing and flow out into the liquid to be measured, which may reduce the accuracy of urea concentration measurement.

The irradiation energy of ultraviolet rays in the ultraviolet irradiation device 52 included in the urea concentration measuring device 12 on the upstream side of the TOC meter 54 is the irradiation energy in which urea is not decomposed and components other than urea are decomposed among the organic substances in the liquid to be measured. It should be. For example, if the irradiation energy per unit volume of the liquid to be measured is 0.1 Wh / L or more, the organic substances in the liquid to be measured can be reliably decomposed. Further, if the irradiation energy per unit volume of the liquid to be measured is 20 Wh / L or less, the state in which urea in the liquid to be measured is not decomposed can be maintained.

The irradiation energy at which urea is not decomposed and components other than urea are decomposed is the irradiation energy at which the decomposition rate does not affect the analytical value of urea. For example, the irradiation energy has a urea decomposition rate of 10% or less, preferably 5% or less, more preferably 1% or less, and the decomposition rate of organic substances other than urea is 90% or more, preferably 95% or more, further. The irradiation energy is preferably 99% or more. By using these decomposition rates, it is possible to analyze the urea concentration with high accuracy.

As shown in FIG. 1, raw water is supplied to the pretreatment device 18 of the ultrapure water production system 16. The pretreatment device 18 includes a urea decomposition device 17 and a turbidity device 19. The urea decomposition device 17 is a device that decomposes urea in the liquid to be treated by performing a predetermined treatment on the supplied liquid to be treated. For example, examples of the treatment performed on the liquid to be treated inside the urea decomposition apparatus 17 include oxidative decomposition, biological treatment method, adsorption removal, and treatment of the water treatment apparatus under operating conditions suitable for the purpose of removing urea.

Examples of the oxidative decomposition method include addition of an oxidizing agent and / or irradiation with ultraviolet rays. Examples of the oxidizing agent include hypobromous acid and / or a salt thereof, hypochlorous acid and / or a salt thereof, persulfate and / or a salt thereof, hydrogen peroxide and the like.

Examples of the biological treatment method include bioactivated carbon treatment with a nitrifying bacterium group, an enzymatic decomposition method using urease, and the like.

As an example of adsorption removal, for example, a method using an oxidized cellulose or a phenol resin as an adsorbent can be mentioned.

Examples of the treatment of the water treatment device under the operating conditions suitable for the purpose of removing urea include treatment by a membrane filtration device using a reverse osmosis membrane (RO) membrane having a high pressure and a low recovery rate.

The urea decomposition device 17 is provided not only in the pretreatment device 18, but also in any one or more of the pretreatment device 18, the primary pure water device 20, and the secondary pure water device 30 as necessary. You can. Further, the operating conditions of the existing water treatment apparatus constituting the ultrapure water production system 16 may be changed to serve as a urea decomposition apparatus, for example, a reverse osmosis membrane (RO) membrane of a primary pure water apparatus may be used. The operation of the membrane filtration device used may be increased in pressure and recovery rate may be reduced.

Depending on the method of urea decomposition, residues such as the added oxidizing agent may remain in the treated water. The urea decomposition method and its implementation location, for example, the installation location of the urea decomposition apparatus, may be appropriately selected in consideration of the required water quality and the like.

As described above, in the configuration in which the urea decomposition apparatus 17 is provided in the pretreatment apparatus 18, as an example, hypobromous acid and / or a salt thereof is added to the liquid to be treated in the urea decomposition apparatus 17, and the subject is subjected to treatment. Urea in the treatment liquid is oxidatively decomposed to _{N 2.} At this time, the excessively added hypobromous acid and / or a salt thereof may be neutralized by adding sodium sulfite immediately after the decomposition of urea, for example.

Further, the measurement result of the urea concentration measuring device 12 can be reflected in the operating conditions of the urea decomposition device 17 and the like.

For example, adjusting the addition amount of hypobromous acid and / or a salt thereof from the measurement result of the urea concentration measuring device 12 is preferable from the viewpoint of cost and water quality because the addition of an excessive amount can be suppressed.

In addition, for example, a plurality of membrane filtration devices using reverse osmosis membranes of the primary pure water device are installed in parallel, one is operated under the conventional conditions, and the other is operated under the conditions of high pressure and low recovery rate. In addition to the urea decomposition device to be performed, it is also possible to control which membrane filtration device the liquid to be treated is sent according to the measurement result of the urea concentration measuring device 12. In this case, the liquid to be treated is not unnecessarily sent to the device having a low recovery rate, which is preferable in terms of cost and productivity.

The pretreatment device 18 further includes a decontamination device 19. The decontamination device deturbates the raw water using a coagulation sedimentation means, a sand filtration means, a membrane filtration means, or the like.

In the pretreatment device 18, the positions of the urea decomposition device 17 and the decontamination device 19 may be reversed.

The pretreatment device 18 performs the above treatment on the supplied raw water to obtain pretreated water from which suspended solids and a part of organic substances have been removed. Examples of raw water include industrial water, tap water, groundwater, river water and the like. However, the pretreatment device 18 may be omitted depending on the quality of the raw water.

The pretreated water pretreated by the pretreatment device 18 is sent to the primary pure water device 20. In the present embodiment, the primary pure water device 20 includes an adsorption device 22, a membrane filtration device 24, and an ion exchange device 26.

In the adsorption device 22 of the primary pure water device 20, particles remaining in the pretreated water are adsorbed using an adsorbent such as activated carbon. The membrane filtration device 24 of the primary pure water device 20 uses a filtration membrane such as a reverse osmosis membrane to remove inorganic ions, organic substances, fine particles and the like that could not be removed by the adsorption device 22. In the ion exchange device 26 of the primary pure water device 20, an ion exchange resin or the like is used to remove ions or the like remaining in the pretreated water. In addition to these, the primary pure water device 20 includes, for example, a vacuum degassing device or a membrane degassing device for removing dissolved gas such as dissolved oxygen, a desalting device for removing impurity ions, and the like. It may be configured, or some devices may be omitted. In the flow direction of the pretreated water, the order of these various devices in the primary pure water device 20 is an appropriate order for each treatment, and is not limited to the order shown in FIG.

In the primary pure water device 20, impurities are removed from the pretreated water by further purifying the pretreated water obtained by treating with the pretreatment device 18 in this way, and the primary pure water is removed. To get.

The primary pure water obtained by the primary pure water device 20 is sent to the pure water tank 28. The pure water tank 28 is a container for temporarily storing the primary pure water obtained by the primary pure water device 20. The material and shape of the pure water tank 28 are not particularly limited as long as it does not elute components from the container or generate rust and can stably store the primary pure water. For example, materials such as fiber reinforced plastics (FRP: Fiber Reinforced Plastics), polyethylene, SUS304, and Teflon (registered trademark) linings thereof are preferably used. Further, the upper part of the pure water tank 28 is preferably purged with pure nitrogen in order to prevent absorption of impurity gases such as carbon dioxide gas and dissolved oxygen. As will be described later, the pure water tank 28 can be mixed with the above-mentioned primary pure water and stored when unused ultrapure water is circulated among the produced ultrapure water.

The primary pure water stored in the pure water tank 28 is sent to the secondary pure water device 30. In the present embodiment, the secondary pure water device 30 includes an ultraviolet irradiation device 32, a membrane degassing device 34, an ion exchange device 36, and a membrane filtration device 38.

The ultraviolet irradiation device 32 of the secondary pure water device 30 irradiates the primary pure water with ultraviolet rays to decompose organic substances in the primary pure water and kill (sterilize) viable bacteria. As the ultraviolet irradiation device 32, for example, if it is equipped with an ultraviolet lamp capable of irradiating a wavelength of about 185 nm or a wavelength of about 254 nm, it is possible to reliably decompose and sterilize organic substances in the primary pure water. be. The ultraviolet lamp to be used is not particularly limited, but a low-pressure mercury lamp is preferable in terms of ease of handling. Further, examples of the ultraviolet irradiation device include a distribution type and an immersion type, and the distribution type is preferable from the viewpoint of processing efficiency.

The membrane degassing device 34 is a device that removes gas, particularly dissolved oxygen, in primary pure water by using a gas separation membrane that does not allow water to permeate but allows gas to permeate. The primary pure water treated by the membrane degassing device 34 is in a state where the concentration of dissolved oxygen is low.

The primary pure water whose dissolved oxygen concentration has been reduced by the membrane degassing device 34 is sent to the ion exchange device 36.

The ion exchange device 36 is a device that removes impurity ions such as organic acids generated in the ultraviolet irradiation device 32. For example, it has a structure in which a cylindrical airtight container is filled with an ion exchange resin.

The primary pure water from which impurity ions have been removed by the ion exchange device 36 is sent to the membrane filtration device (UF) 38.

The membrane filtration device (UF) 38 is a device for producing ultrapure water by removing fine particles, and is arranged at the end of the secondary pure water device 30.

In the secondary pure water device 30, for example, a heat exchanger may be provided on the upstream side of the ultraviolet irradiation device 32 to adjust the temperature by heat exchange (heating or cooling) with respect to the primary pure water. Examples of the heat exchanger include a plate-type heat exchanger, but the specific structure is not particularly limited. Further, in the secondary pure water device 30, other processing devices may be provided as necessary, such as taking measures against contamination of microorganisms by sterilizing means or the like, so that ultrapure water having a desired purity can be obtained. ..

The ultrapure water obtained by the secondary pure water device 30 is sent to the use point 40, which is the place of use. Of the sent out ultrapure water, the unused ultrapure water is circulated to the pure water tank 28 as it is, and is stored in the pure water tank 28 together with the primary pure water.

A part of the raw water is sent to the urea concentration measuring device 12 by a branch pipe branching from a pipe for flowing the raw water to the pretreatment device 18.

The position where the urea concentration of the liquid to be measured is measured by the urea concentration measuring device 12 is not limited to the above position. In the present application, by applying a pretreatment method before measuring the total organic carbon amount by the TOC meter 54, it is possible to measure the urea concentration with good accuracy even for the liquid to be measured in which an organic substance other than urea is present. can. This effect becomes greater as the liquid to be measured contains a large amount of organic substances other than urea.

From this point of view, when the urea concentration measuring device 12 of the present invention is provided in the ultrapure water producing device 14, it is preferable to provide the urea concentration measuring device 12 at a position close to the raw water. That is, in the case of the ultrapure water production apparatus 14 having the pretreatment apparatus 18, it is preferable to provide the ultrapure water production apparatus 14 upstream of the pretreatment apparatus 18 or the pretreatment apparatus 18, and as in the first embodiment, upstream of the pretreatment apparatus 18. It is more preferable to provide in.

The purpose of measuring the urea concentration of the liquid to be treated supplied to the urea decomposition device 17 in order to determine the operating conditions of the urea decomposition device 17 when the ultrapure water production device 14 has the urea decomposition device 17. From the above, it is preferable that it is upstream of the urea decomposition device 17, for example, immediately before the urea decomposition device 17.

On the other hand, for the purpose of confirming the urea concentration after the treatment by the urea decomposition apparatus 17, it is preferable that the concentration is downstream of the urea decomposition apparatus 17, for example, immediately after the urea decomposition apparatus 17.

Further, for the purpose of confirming the urea concentration of the ultrapure water actually used, it is preferable to install the urea concentration measuring device 12 at an arbitrary position of the secondary pure water device 30 or immediately before the use point 40, and the use It is particularly preferable to install it immediately before the point 40.

From this point of view, for example, the ultrapure water production system 66 of the second embodiment shown in FIG. 3 can be configured. In FIG. 3, the same elements, members, and the like as in the first embodiment are designated by the same reference numerals as those in the first embodiment, and detailed description thereof will be omitted.

In the ultrapure water production system 66 of the second embodiment, the urea concentration measuring device 12 is installed between the secondary pure water device 30 and the use point 40, that is, immediately before the use point 40 in the overall configuration of the ultrapure water production system 66. It is installed.

In the ultrapure water production system 66 of the second embodiment, the urea concentration measuring device 12 uses the ultrapure water obtained by the secondary pure water device 30 as the measurement target liquid. Therefore, it is considered that the concentration of organic substances in the liquid to be measured is lower than that of the first embodiment. Even when the organic matter concentration is low as described above, the residual organic matter can be removed by using the filtration device 50, but when the organic matter concentration is sufficiently low, the filtration device 50 is omitted. You may.

Further, for example, at positions B to E shown in FIG. 1, the urea concentration of the liquid to be measured may be measured by the urea concentration measuring device 12. At position B, since the urea concentration measuring device 12 is incorporated between the pretreatment device 18 and the primary pure water device 20, the urea concentration of the pretreatment water can be directly observed. Similarly, at position D, since the urea concentration measuring device 12 is incorporated between the primary pure water device 20 and the secondary pure water device 30, the urea concentration of the treated water of the primary pure water device 20 can be directly observed, for example, urea. When the concentration becomes abnormally high, it is possible to control such that the treated water obtained by the primary pure water device 20 is not supplied to the secondary pure water device 30. Similarly, when measuring the treated water at position E or the membrane filtration device 38, the urea concentration in the circle pipe of the secondary pure water device 30 or the ultrapure water supplied to the use point, which is not described, is directly measured. Therefore, it is possible to monitor the transition of the urea concentration of ultrapure water. The urea concentration measuring device 12 may be installed at a plurality of the above-mentioned positions (positions of the first embodiment, positions of the second embodiment, and positions B to E shown in FIG. 1).

In the above, the configuration in which the urea concentration measuring device 12 is included as a part of the ultrapure water production system 16 is illustrated, but the target including the urea concentration measuring device 12 is not limited to the ultrapure water production system 16. For example, in various water production systems to be treated such as a water production system for pharmaceuticals and a water production system for injection, it is possible to incorporate the urea concentration measuring device 12 as a part thereof. In other words, the measurement target in the urea concentration measuring device 12 is not limited to ultrapure water, and various types of water to be treated such as pharmaceutical water and water for injection (WFI) are the measurement targets of the urea concentration in the urea concentration measuring device 12. be.

In the ultrapure water production system 16 in which the urea concentration measuring device 12 is incorporated, the measurement result may be used for the purpose of guaranteeing the quality of the produced ultrapure water based on the measured urea concentration, or the measurement result may be used. It may be used for adjustment, monitoring and inspection of the process of producing ultrapure water.

Hereinafter, the present application will be described in more detail by way of examples. However, the present application is not limited to the contents of the following examples.

Table 1 below shows the results of measuring the urea concentration in tap water (Atsugi City water) after passing activated carbon, in an example in which the above embodiment was applied and in a comparative example in which the above embodiment was not applied. ing. Specifically, in the example, in the urea concentration measuring device 12, the liquid to be measured was irradiated with ultraviolet rays by the ultraviolet irradiation device 52 before the measurement by the TOC meter 54, whereas in the comparative example, the ultraviolet irradiation was performed. Ultraviolet irradiation by the device 52 is not performed.

The liquids to be measured were the liquid 1 to be measured using tap water after passing through the activated charcoal as it was, the liquid 2 to be measured in which urea was added to the liquid 1 to be measured, and the urea concentration was adjusted to 50 ppb, and the liquid to be measured was adjusted to 100 ppb. The liquid to be measured 3 was prepared.

As the filtration device 50, RE2521-BLF manufactured by Toray Industries, Inc. was used as the filtration device having a reverse osmosis membrane, and the flow rate of the liquid to be measured was 0.4 L / min and the recovery rate was 50%.

As the ultraviolet irradiation device 52, NPU-1 / 2N manufactured by Nippon Photoscience was used, and AY-11 was used as the ultraviolet lamp. Using this ultraviolet lamp, the irradiation energy per unit volume of the liquid to be measured was configured to be 2.66 Wh / L. In this embodiment, since substantially all organic substances other than urea can be decomposed into carbon dioxide by this irradiation energy, the weak acid removing device 55 is not installed.

For the TOC total 54, a Sievers M9e online type manufactured by SUEZ was used. Since the ultraviolet lamp used in the oxidizing device 58 inside the TOC total 54 is 4.8 W and the flow rate is 0.25 mL / min, the power consumption with respect to the flow rate is 320 Wh / L.

The analytical values in Table 1 are urea concentration values obtained by analysis by liquid chromatography, and are close to the actual urea concentration.

The value (measured value) obtained by the TOC total 54 was converted into a urea concentration by the following formula.
Urea concentration = measured value of TOC meter x 60/12

From Table 1, it can be seen that in the case of the example, the measured value closer to the analytical value was obtained in any of the measurement target liquids 1 to 3 than in the case of the comparative example. In particular, in the liquid to be measured 1, although the analytical value of the urea concentration is as low as less than 5 ppb, the measured value is as high as 25 to 40 ppb in the comparative example, but in the example, it is less than 5 ppb as in the analytical value. It is the measured value of.

Further, also in the cases of the liquids 2 and 3 to be measured, the measured values are larger than the analytical values in the comparative example, but the measured values close to the analytical values are obtained in the examples.

12 Urea concentration measuring device 14 Ultrapure water production device 16 Ultrapure water production system 18 Pretreatment device 20 Primary pure water device 22 Adsorption device 24 Film filtration device 26 Ion exchange device 28 Pure water tank 30 Secondary pure water device 32 Ultraviolet irradiation Device 34 Membrane degassing device 36 Ion exchange device 38 Membrane filtration device 40 Use point 50 Filtration device 52 _{Ultrapure water irradiation device 54 TOC total 56 Decarbonizer 58 Oxidation device 60, 62 CO 2} detection device 66 Ultrapure water production system

Claims (8)

Before measuring the total organic carbon amount of the measurement target liquid with a total organic carbon meter, the measurement target liquid is prepared by irradiating ultraviolet rays with irradiation energy that does not decompose urea but decomposes organic substances other than urea. Processing method. The pretreatment method according to claim 1, wherein the irradiation energy of the ultraviolet rays is 0.1 Wh / L or more and 20 Wh / L or less per unit volume of the liquid to be measured. Irradiation energy that is provided on the upstream side of the flow of the liquid to be measured and decomposes organic substances other than urea without decomposing urea with respect to the liquid to be measured. Pretreatment device for the liquid to be measured that irradiates with ultraviolet rays. The liquid to be measured is irradiated with ultraviolet rays with irradiation energy that does not decompose urea but decomposes organic substances other than urea.
A method for measuring a urea concentration in which the total amount of organic carbon is measured by a total organic carbon meter with respect to the liquid to be measured in which the organic substances other than urea are decomposed. A pretreatment device that irradiates ultraviolet rays with irradiation energy that does not decompose urea but decomposes organic substances other than urea with respect to the liquid to be measured.
An all-organic carbon meter that measures the total amount of organic carbon in the measurement target liquid in which the organic substances other than urea are decomposed by irradiation with the ultraviolet rays by the pretreatment apparatus.
Urea concentration measuring device having. Ultrapure water is generated by treating raw water, and the ultrapure water is sent to the point of use where the ultrapure water is used.
A liquid at any stage from the raw water to the ultrapure water is used as the liquid to be measured, and the liquid to be measured is irradiated with ultraviolet rays with irradiation energy that does not decompose urea but decomposes organic substances other than urea.
An ultrapure water production method in which the total amount of organic carbon is measured by a total organic carbon meter with respect to the liquid to be measured in which the organic substances other than urea are decomposed. An ultrapure water production device that generates ultrapure water by treating raw water and sends the ultrapure water to the point of use where the ultrapure water is used.
A liquid at any stage from the raw water to the ultrapure water in the ultrapure water production apparatus is used as the liquid to be measured, and ultraviolet rays are emitted from the liquid to be measured with irradiation energy that does not decompose urea but decomposes organic substances other than urea. Pretreatment equipment to irradiate and
An all-organic carbon meter that measures the total amount of organic carbon in the measurement target liquid in which the organic substances other than urea are decomposed by irradiation with the ultraviolet rays by the pretreatment apparatus.
Ultrapure water production system with. The ultrapure water production device
A primary pure water device that generates primary pure water by the primary treatment of the raw water, and
A secondary pure water device that produces the ultrapure water by secondary treatment of the primary pure water,
Have,
The ultrapure water production system according to claim 7, wherein the pretreatment apparatus and the total organic carbon meter are provided between the secondary pure water apparatus and the use point.

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