JP2019191099A - Urea monitoring device and pure water production device - Google Patents

Abstract

To provide a urea monitoring device which can be used maintenance-free for an extended period of time and is capable of simply detecting urea in water under inspection, and to provide a pure water production device equipped with the same.SOLUTION: A urea monitoring device is provided, comprising ion removal means for removing ions from water under inspection, and TOC means for measuring total organic carbon concentration (TOC) in the water under inspection after having ions removed by the ion removal means, the ion removal means comprising a reverse osmosis membrane separator and electrodeionization device. Also provided herein is a pure water production device equipped with such urea monitoring device.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a urea monitoring apparatus that can easily detect urea in test water, and a pure water production apparatus including the urea monitoring apparatus.

  Conventionally, ultrapure water used as semiconductor cleaning water is an ultrapure water production system consisting of a pretreatment system, a primary pure water system, and a subsystem (secondary pure water system). Manufactured by processing water, well water, used ultrapure water (hereinafter referred to as “recovered water”) discharged from semiconductor factories.

  In a pretreatment system comprising agglomeration, pressurized flotation (precipitation), filtration (membrane filtration) apparatus, etc., suspended substances and colloidal substances in raw water are removed. In this process, it is also possible to remove high molecular organic substances, hydrophobic organic substances, and the like.

  In a primary pure water system including a reverse osmosis membrane separation device, a deaeration device, and an ion exchange device (such as a mixed bed type or a 4-bed 5-to-column type), ions and organic components in raw water are removed. The reverse osmosis membrane separation apparatus removes salts and ionic and colloidal TOC. The ion exchange apparatus removes salts and removes the TOC component adsorbed or ion exchanged by the ion exchange resin. In the deaerator, inorganic carbon (IC) and dissolved oxygen (DO) are removed.

In a subsystem including a low-pressure ultraviolet oxidation device, an ion-exchange pure water device, and an ultrafiltration membrane separation device, the purity of pure water obtained by the primary pure water system is further increased to ultrapure water. In the low-pressure ultraviolet oxidizer, TOC is decomposed to an organic acid and further to CO ₂ by ultraviolet rays having a wavelength of 185 nm emitted from a low-pressure ultraviolet lamp. Organic substances and CO ₂ produced by the decomposition are removed by an ion exchange pure water apparatus at the subsequent stage. In the ultrafiltration membrane separation device, the fine particles are removed, and the outflow particles from the ion-exchange pure water device are also removed.

However, total organic carbon (TOC) is present in an amount of about 2 to 5 μg / L in the ultrapure water produced by the conventional general ultrapure water production apparatus. This TOC in ultrapure water is present in raw water (city water, industrial water, etc.) in the order of several tens to several hundreds μg / L, and urea (NH ₂ CONH ₂₎ that cannot be removed by existing ultrapure water production equipment. ).
For this reason, it is important to reduce the urea in the raw water and monitor the urea concentration of the raw water and the water in the system in order to obtain ultrapure water with a further reduced TOC.

Patent Document 1 proposes an ultrapure water production apparatus provided with a urea decomposition treatment means and a urea monitoring device that continuously detects the urea concentration in the water to be treated at a position upstream of the urea decomposition treatment means. Yes. The urea monitoring apparatus described in Patent Document 1 includes an ion removing unit that removes ions contained in the water to be treated, and a TOC measuring unit that measures total organic carbon (TOC) contained in the water to be treated after the ion removal. Is provided. That is, since the ultraviolet TOC measuring means used in Patent Document 1 detects urea from the change in the electrical conductivity of water due to CO ₂ or NO ₃ generated by the decomposition of urea, it has a high concentration of ions. Since it cannot be applied to test water containing a component, it is necessary to perform measurement with the TOC measuring means after removing ions in the water to be treated with the ion removing means. Patent Document 1 describes the use of a mixed bed type ion exchange resin tower as the ion removing means because urea is hardly removed.

Japanese Patent Laid-Open No. 9-94585

  In the urea monitoring apparatus of Patent Document 1 using a mixed bed type ion exchange resin tower as an ion removing means, the ion exchange resin in the mixed bed type ion exchange resin tower or the mixed bed type ion exchange resin tower itself is periodically exchanged. Treatment for regeneration of the ion exchange resin is necessary, and urea cannot be detected for a long time without maintenance.

  The present invention solves this problem of the urea monitoring device described in Patent Document 1, can be used for maintenance for a long period of time, and can easily detect urea in the test water. An object of the present invention is to provide a pure water production apparatus including a urea monitoring device.

The present inventors have found that the above-described problems can be solved by using a reverse osmosis membrane separation device and an electrodeionization device in combination as an ion removing means.
That is, the gist of the present invention is as follows.

[1] Urea monitoring apparatus having ion removing means for removing ions in the test water and TOC measuring means for measuring the total organic carbon (TOC) concentration of the test water from which ions have been removed by the ion removing means The urea monitoring device, wherein the ion removing means includes a reverse osmosis membrane separation device and an electrodeionization device.

[2] The ion removing means has means for introducing the permeated water of the reverse osmosis membrane separation device into the electrodeionization device, and the TOC concentration of the treated water of the electrodeionization device is measured by the TOC measuring means. The urea monitoring device according to [1], wherein

[3] The urea monitoring apparatus according to [1] or [2], further including a calculation unit that corrects a measurement value of the TOC measurement unit based on a urea removal rate measured in advance by the ion removal unit.

[4] A pure water production apparatus including the urea monitoring device according to any one of [1] to [3].

In the urea monitoring apparatus of the present invention, the reverse osmosis membrane separation apparatus and the electrodeionization apparatus used as ion removing means do not require regeneration or replacement like ion exchange resins, and can be used without maintenance for a long time. it can. For this reason, according to the urea monitoring device of the present invention, it is possible to easily detect urea in the test water without maintenance for a long period of time.
Further, according to the pure water production apparatus of the present invention provided with such a urea monitoring apparatus of the present invention, by quickly detecting the urea concentration of raw water or water in the system and reflecting this in the processing operation, High-quality pure water or ultrapure water with a further reduced TOC concentration can be produced.

3 is a graph showing a change with time in the urea analysis value in Example 1.

  Hereinafter, embodiments of the present invention will be described in detail.

[Urea monitoring device]
The urea monitoring apparatus of the present invention includes an ion removing unit that removes ions in the test water, and a TOC measuring unit that measures the total organic carbon (TOC) concentration of the test water from which ions have been removed by the ion removing unit. The urea monitoring apparatus having the above-mentioned feature is characterized in that the ion removing means includes a reverse osmosis membrane separation device and an electrodeionization device.

<Ion removal means>
The ion removal means of the urea monitoring device of the present invention includes an RO membrane separation device and an electrodeionization device, and the permeated water of the RO membrane separation device is processed by the electrodeionization device, and the treated water of the electrodeionization device is TOC measured. It is sent to the means.

  There is no restriction | limiting in particular as RO membrane separator, Any RO membrane separator used for general pure water manufacture can be used conveniently.

  Also in the electrodeionization apparatus, a plurality of cation exchange membranes and anion exchange membranes are alternately arranged between the cathode and the anode, so that a concentration chamber and a desalination chamber are alternately formed. A general electrodeionization apparatus in which the salt chamber and the concentration chamber are filled with an ion exchanger such as an ion exchange resin can be used.

  When only the RO membrane separation device is used as the ion removing means, ions in the test water cannot be removed to a high degree. On the other hand, when only the electrodeionization device is used, the load is large and calcium or Silica scale is generated and operation becomes impossible. In contrast, the RO membrane separation device and the electrodeionization device are used, and the permeated water of the RO membrane separation device is further processed by the electrodeionization device, so that ions in the test water are removed at a high level. The water quality is suitable for the water supply of the TOC meter.

  As shown in the examples below, urea is not removed by the electrodeionization device, but is removed by 30 to 40% by the RO membrane separation device. Therefore, as will be described later, it is preferable to perform arithmetic processing for correcting urea removed by the RO membrane separation device.

<TOC measuring means>
The TOC measuring means used in the present invention includes a UV irradiation apparatus that irradiates ultraviolet rays (UV) to water to be detected from which ions have been removed by the ion removing means, a carbon dioxide permeable membrane, and an electric conductivity meter. In the UV irradiation apparatus, a UV lamp is usually provided around the water passage of the test water, and the test water flowing through the water passage is irradiated with UV. When the test water is irradiated with UV, urea in the test water is decomposed to generate CO ₂ . The CO ₂ produced by the decomposition of urea is separated from the test water into a pure water line in the electric conductivity meter by the carbon dioxide permeable membrane, and the separated CO ₂ (carbonate radical) is measured by electric conductivity. .
That is, CO ₂ produced by the decomposition of urea is selectively separated by the permeable membrane, and the amount of the separated CO ₂ is measured as electric conductivity. Therefore, it is possible to accurately measure the TOC of urea by excluding other ions. Therefore, this measurement result can be applied to a calibration curve indicating the relationship between the urea concentration and the electrical conductivity prepared in advance using sample water with a known urea concentration, and the urea concentration of the test water can be obtained.

  Such a TOC measuring means can be continuously measured by continuously passing water under test, and is simple in structure and space-saving, so it can be easily applied as a TOC measuring means for a urea monitoring device. .

<Measurement value correction>
As described above, in the RO membrane separation apparatus used as the ion removing means in the present invention, not only ions but also urea in the test water is partially removed. Therefore, it is preferable to obtain the urea removal rate by the RO membrane separation device in advance and correct the measured value of the TOC measuring means with this urea removal rate.
Further, as shown in the examples described later, when the activated carbon tower is provided in the previous stage of the RO membrane separation apparatus, urea in the test water is removed even in the activated carbon tower. It is preferable to obtain the urea removal rate by, and correct the measured value of the TOC measuring means with the urea removal rate by the activated carbon tower and the urea removal rate by the RO membrane separation device.

  The correction of the measured value can be automatically performed by an arithmetic unit that inputs the urea removal rate of the RO membrane separation device or the activated carbon tower.

[Pure water production equipment]
The pure water production apparatus of the present invention comprises the urea monitoring apparatus of the present invention as described above, and there are no particular restrictions on the components other than the urea monitoring apparatus of the pure water production apparatus of the present invention. Water, city water, well water, recovered water, etc.) having fine means, ions, organic substances, bacteria, gas, etc. contained in these raw waters in a stepwise manner.

  For example, as described above, a pretreatment system comprising agglomeration, pressurized flotation (precipitation), filtration (membrane filtration) device, etc., reverse osmosis membrane separation device, deaeration device, and ion exchange device (mixed bed type or 4 beds 5) A pure water system having a tower type) and a sub-system having a low-pressure ultraviolet oxidizer, an ion exchange pure water device, and an ultrafiltration membrane separator, and these devices may be used. Some of them may be omitted.

  In the urea monitoring apparatus of the present invention, in such a pure water production apparatus, urea in raw water or treated water (which may be produced pure water or water in the system) may be continuously or intermittently used. Provided for monitoring. For example, a part of raw water or treated water is collected, and the urea concentration in the raw water or treated water is measured continuously or intermittently by the urea monitoring apparatus of the present invention.

  In the pure water production apparatus of the present invention, it is preferable that a urea removing device is further provided as necessary, and the following control is performed based on the urea concentration of raw water or treated water measured by the urea monitoring device.

  The urea concentration of raw water or treated water is measured continuously or intermittently with a urea monitoring device, and when the urea concentration of the raw water or treated water exceeds the reference value, the urea removal device is activated, and the urea concentration of raw water or treated water When the value falls below the reference value, the operation of the urea removal device is stopped. Or, the urea removal device is branched from the pure water production device, and when the urea concentration of the raw water or the treated water exceeds the reference value, a part or all of the raw water is treated with the pure water production device and then the pure water production The water is supplied to the apparatus, and when the urea concentration of the raw water or the treated water falls below the reference value, the raw water is directly supplied to the pure water producing apparatus or the raw water amount to be processed by the urea removing apparatus is reduced.

The operation and stop of the urea removal device can be automatically performed by providing a control means for controlling the operation of the urea removal device based on the input result of the measurement result of the urea monitoring device. .
In addition, for the control of the raw water inflow rate to the urea removal device, the measurement result of the urea monitoring device is input, and based on this input value, the flow rate adjustment valve that controls the inflow amount of the raw water to the urea removal device is opened. This can be done automatically by adjusting the degree or by providing a control means for operating a switching valve for changing the feed destination of the raw water.

When the urea removal device is not provided in the pure water production device, the urea concentration of the raw water or the treated water is measured continuously or intermittently by the urea monitoring device, and when the urea concentration of the raw water or the treated water exceeds the reference value, The supply of raw water to the pure water production apparatus is stopped, and spare pure water stored separately is supplied to the pure water production apparatus, or the pure water production apparatus is temporarily stopped. Moreover, when the urea concentration of raw | natural water or treated water falls below a reference value, water supply of raw | natural water is restarted.
The control of the raw water supply is also automatically performed by providing a control means for controlling the stop and restart of the supply of raw water or treated water based on this input value, based on the measurement result of the urea monitoring device. be able to.

  The above-mentioned “reference value of urea concentration of raw water or treated water” is appropriately determined according to the use of treated water (allowable value of urea concentration) obtained with a pure water production apparatus.

When a urea removal device is provided in a pure water production device, the urea removal device is not particularly limited. For example, any of the following urea decomposition agents (1) to (3) is added under the conditions of pH 4 to 8 Thus, the one that decomposes urea in water can be used.
(1) Hypobromite (2) Alkali bromide and sodium hypochlorite (3) Alkali bromide and ozone In addition, an enzyme decomposing apparatus in which urease, which is a urea decomposing enzyme, is supported on an appropriate carrier is used. You can also.

  The present invention will be described more specifically with reference to the following examples.

[Example 1]
Using Nogicho water as test water, after passing through the activated carbon tower, intermediate tank, RO membrane separation device, and electrodeionization device in order, the TOC concentration was measured with a TOC meter. The change over time in the urea concentration was analyzed using a calibration curve showing the relationship between the prepared TOC concentration and the urea concentration.
The activated carbon tower was used for the purpose of removing chlorine contained in Nogicho water.
The following were used as the activated carbon tower, RO membrane separation device, electrodeionization device, and TOC meter.
Activated carbon tower: Kurita Industrial Co., Ltd. carboner “C-07”
RO membrane: “DOW FILMTECTM TW30-1812-75” manufactured by Dow Chemical
Electrodeionizer: “IONPURE (registered trademark) MX30” manufactured by Evoqua Water Technologies
Ultraviolet TOC meter: Sievers (registered trademark) online TOC meter 500RLe manufactured by SUEZ

  About test water, activated carbon tower outlet water, RO membrane separator outlet water (permeated water), and electrodeionizer outlet water (treated water), Shimadzu Corporation liquid chromatograph mass spectrometer “LC (NexeraX2) − The results of analyzing the urea concentration by “MS (LCMS8040)” are shown in Table 2 below. Table 2 also shows the results of calculating the urea removal rate from the urea concentration of each outlet water with respect to the urea concentration of the test water.

<LC-MS specifications>
Column: Merck Millipore SeQuant ZIC-HILIC 2.1 × 100 mm 3.5 μm
Mobile phase: 5 mM ammonium acetate (pH 6.8) / acetonitrile flow rate: 0.2 mL / min
Injection volume: 40 μL
Gradient conditions: Table 1 below

オーブン温度：４０℃
測定ｍ／ｚ：６１．００＞−４４．０５
測定モード：ＭＲＭ
ＤＬ温度：１８０℃
ヒートブロック温度：４８０℃
ＣＩＤガス：アルゴン
ネブライザーガス：３Ｌ／分
ドライングガス：１５Ｌ／分
イオン化：ＥＳＩ Ｐｏｓｉｔｉｖｅ

Oven temperature: 40 ° C
Measurement m / z: 61.00> −44.05
Measurement mode: MRM
DL temperature: 180 ° C
Heat block temperature: 480 ° C
CID gas: Argon nebulizer gas: 3 L / min Drying gas: 15 L / min Ionization: ESI Positive

  From Table 2, some amount of urea in the test water is removed by the activated carbon tower, but many are removed by the RO membrane separator, and urea is not removed by the electrodeionization apparatus. The activated carbon tower, the RO membrane separator and 45% of the urea in the test water is removed by the process of the electrodeionization apparatus, 32.5% is removed by the process of the RO membrane separator alone, and the urea concentration in the outlet of the electrodeionization apparatus is It can be seen that this corresponds to 55% of the urea concentration of the test water.

Based on the above results, urea analysis with the above TOC meter was performed over time, and the urea concentration measurement result based on the TOC meter was corrected with the urea removal rate by the activated carbon tower, RO membrane separator and electrodeionization device Is the urea analysis value of the test water (specifically, the urea concentration measurement result based on the TOC meter was divided by 0.55 to obtain the urea concentration of the test water), and the results are shown in FIG. .
In FIG. 1, urea analysis values obtained by intermittently analyzing the test water using the aforementioned LC (NexeraX2) -MS (LCMS8040) manufactured by Shimadzu Corporation are also shown.
FIG. 1 shows that the urea analysis value according to the present invention and the analysis value according to LC-MS coincide with each other, and the urea concentration of the test water can be accurately measured by the urea monitoring apparatus according to the present invention.

Claims (4)

  A urea monitoring apparatus comprising ion removing means for removing ions in test water, and TOC measuring means for measuring the total organic carbon (TOC) concentration of test water from which ions have been removed by the ion removing means. The urea monitoring device characterized in that the ion removing means includes a reverse osmosis membrane separation device and an electrodeionization device.   The ion removing means has means for introducing the permeated water of the reverse osmosis membrane separation apparatus into the electrodeionization apparatus, and the TOC concentration is measured by the TOC measuring means for the treated water of the electrodeionization apparatus. The urea monitoring device according to claim 1.   The urea monitoring apparatus according to claim 1, further comprising a calculation unit that corrects a measurement value of the TOC measurement unit based on a urea removal rate measured in advance by the ion removal unit.   The pure water manufacturing apparatus provided with the urea monitoring apparatus in any one of Claim 1 thru | or 3.

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