JP2014188456A - Method for operating ion exchange resin device, and ion exchange resin device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for operating an ion exchange resin device, in which breakthrough of the ion exchange resin device is detected surely and at an early stage so that the amount of water to be collected can be made larger and the amounts (the total amount) of the silica and boron to be leaked from the ion exchange resin device can be made smaller.SOLUTION: The method for operating the ion exchange resin device comprises the steps of: making the water to be treated pass through an anion exchange resin layer to perform an anion exchange; measuring the specific resistance or electrical conductivity of the treated water; and regenerating or replacing an existing anion exchange resin on the basis of the measured result. An ascent of the specific resistance or a descent of the electrical conductivity is detected in a very early stage of the breakthrough of the boron and silica. When the specific resistance rises to a predetermined value or the electrical conductivity falls to another predetermined value, the existing anion exchange resin is regenerated or replaced.

Description

  The present invention relates to an ion exchange resin apparatus operation method and an ion exchange resin apparatus, and more particularly to an ion exchange resin apparatus operation method and an ion exchange capable of reducing the amount of weak acid components such as boron and silica flowing out from an anion exchange resin. The present invention relates to a resin device.

In a pure water production process using industrial water or tap water as raw water, a so-called two-bed / three-column type ion exchange resin apparatus that passes water in the order of cation exchange resin tower → (decarbonation tower) → anion exchange resin tower is used. Widely used. In such an ion exchange resin apparatus that passes water in the order of the cation resin tower and the anion exchange resin tower, one of the following operation methods is often employed.
1) An operation method in which the amount of water sampled is set in advance, and when it reaches it, the water flow operation is stopped and the ion exchange resin is regenerated.
2) An operation method for measuring the electrical conductivity of treated water and stopping the water flow operation to regenerate the ion exchange resin when the electrical conductivity rises to a preset allowable value of electrical conductivity.
3) An operating method in which an on-line analyzer (silica calculation, boron meter) is installed in the treated water, and when the measured concentration of silica, boron, etc. exceeds the allowable value, the water flow operation is stopped and the ion exchange resin is regenerated. . (For example, Patent Document 1 describes that a silica meter is provided in the subsequent stage of the ion exchange resin device, and the replacement time of the ion exchange resin is determined from the measured value.)

  The conventional driving methods 1) to 3) have the following problems.

  In the method of 1), if the set water sampling amount is large, the quality of the treated water is abruptly deteriorated (silica or boron concentration is increased) when breakthrough occurs, and a load is imposed on the subsequent process. For this reason, it is normal to set the sampling volume to be small, but if the sampling volume is too small, regeneration will be performed without fully using the ion exchange capacity of the ion exchange resin, and the cost of regenerative chemicals will increase. .

  In the method 2), even if silica or boron breaks through, the electrical conductivity of the treated water hardly increases. Therefore, when the electrical conductivity starts to rise, the silica and boron already flow out into the treated water to a high concentration. I'm stuck.

  In the method of 3), the online silica meter and the online boron meter are very expensive, and the online boron meter has a restriction condition that the specific resistance value is 15 MΩcm or more, and as an operation method as a pretreatment of the ultrapure water production process. Is difficult to adopt.

  As a break detection method of an ion exchange resin using a boron analyzer, there is a method described in Patent Document 2. FIG. 3 of FIG. In Patent Document 2, when a test for measuring the boron concentration and the silica concentration in the treated water of the ion exchange resin was performed, as shown in FIG. 3, boron breaks earlier than silica; It is described that an anionic break point is detected before a silica break by measuring a boron concentration in the treated water and detecting a boron break.

  As shown in FIG. 3, Patent Document 2 states that when water is passed through an anion exchange resin, boron breaks first, and then silica breaks; even if boron breaks, the specific resistance does not decrease until silica breaks. It is shown that the specific resistance gradually decreases when the silica break begins.

JP-A-8-24852 JP-A-8-117744

  In Patent Document 2, an expensive inductively coupled plasma mass spectrometer (ICP-MS) is used for measuring the boron concentration (paragraphs 0010 and 0018). Therefore, it is not preferable.

  The present invention, without actually measuring the boron concentration using a boron analyzer, reliably and quickly detects a break in the ion exchange resin device, increases the amount of water collected, and silica from the ion exchange resin device, It aims at providing the operating method of the ion exchange resin apparatus which can make the leak amount (total amount) of boron small.

  The operation method of the ion exchange resin apparatus of the present invention is that the water to be treated is passed through the anion exchange resin layer and subjected to anion exchange treatment, the specific resistance or electrical conductivity of the obtained treated water is measured, and the measurement result is In the operation method of the ion exchange resin apparatus that regenerates or replaces the anion exchange resin based on this, an increase in specific resistance or a decrease in electrical conductivity in the initial break of boron and silica in the treated water is detected, and the detection result On the basis of this, regeneration, exchange of the anion exchange resin, stop of water flow to the anion exchange resin, or change of water flow conditions is performed.

  In the present invention, at the initial stage of the break, when the specific resistance or its increase rate is increased to a predetermined value, or when the electrical conductivity or its decrease rate is decreased to a predetermined value, regeneration and exchange of the anion exchange resin, It is preferable to stop water flow to the anion exchange resin or change the water flow conditions.

In this case, the next R2 or R1 is calculated based on the following variables A, B, and C, and when R2 or R1 becomes a predetermined value or more, regeneration and exchange of the anion exchange resin, water flow to the anion exchange resin It is preferable to stop or change the water flow conditions.
A: Time average of resistivity values from T minutes before to the present time B: Time average of resistivity values from 2T minutes to T minutes ago C: Time average of resistivity values from 3T minutes to 2T minutes before R2 = (A + C-2B) / T ²
R1 = (A−B) / T

The ion exchange resin apparatus of the present invention is an ion exchange resin apparatus comprising an anion exchange resin layer through which water to be treated is passed, and means for measuring the specific resistance of treated water of the anion exchange resin layer, The means for calculating the next R2 or R1 based on the following variables A, B, and C, and stopping the flow of the treated water to the anion exchange resin layer when R2 or R1 exceeds a predetermined value It is characterized by providing.
A: Time average of resistivity values from T minutes before to the present time B: Time average of resistivity values from 2T minutes to T minutes ago C: Time average of resistivity values from 3T minutes to 2T minutes before R2 = (A + C-2B) / T ²
R1 = (A−B) / T

  When the inventor conducted various studies on the break and specific resistance (or electrical conductivity) of boron and silica of the anion exchange resin, when the anion exchange resin breaks, the specific resistance of the anion exchange resin-treated water decreases ( Or the electrical conductivity increases), the resistivity increases temporarily at the beginning of the boron and silica break, and then the resistivity decreases rapidly (or the electrical conductivity decreases temporarily, Thereafter, the electrical conductivity was found to increase rapidly). This finding is a novel finding which is not shown at all in Patent Document 2 (Attached FIG. 3).

  In the present invention, when a temporary increase in specific resistance (or a temporary decrease in electrical conductivity) in the initial stage of boron and silica break is detected, water sampling from the anion exchange resin is stopped. . According to the present invention, water is collected until immediately before the full break of boron and silica, the exchange capacity of the anion exchange resin is utilized to the maximum, and before the full break of boron and silica from the anion exchange resin occurs. It is possible to reliably stop water collection and regenerate or replace the anion exchange resin. Therefore, according to the present invention, it is possible to reduce the regeneration or exchange cost of an anion exchange resin (in the case of a non-regenerative ion exchange apparatus) and the cost of producing pure water.

It is a graph explaining the present invention. It is a flowchart of the ultrapure water manufacturing system which employ | adopted the operating method of the ion exchange resin apparatus which concerns on embodiment. It is a graph explaining a prior art example.

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

  An example of the ultrapure water production system that employs the operation method of the ion exchange resin apparatus of the present invention is shown in FIG.

  Raw water such as industrial water and tap water is processed through the cation exchange resin tower 1, the decarbonation tower 2, the anion exchange resin tower 3, the pure water tank 4, and the ultrapure water production process 5 to become ultrapure water, which is sent to the use point. Is done. The specific resistance of the effluent water of the anion exchange resin tower 3 is measured by a specific resistance meter 6, and this specific resistance is calculated by a calculation device 7. When the specific resistance increases by a predetermined value or more, it is determined that the anion exchange resin is broken, and the anion exchange resin in the anion exchange resin tower 3 is regenerated. FIG. 1 is a graph showing changes over time in measured values of boron concentration, silica concentration, and specific resistance of effluent water from the anion exchange resin tower 3 of FIG. As shown in FIG. 1, a boron break starts about 25 hours after the start of water flow, and a silica break starts several hours later.

  The specific resistance is constant at about 2.5 MΩ · cm while the silica concentration in the treated water is about 0.1 μg / L or less. The specific resistance increases first when boron and silica breaks start, and then decreases rapidly. Note that the specific resistance temporarily increases in the initial break of boron and silica because silica forms a complex with dissolved sodium ions in the treated water and reduces the contribution of sodium to electrical conductivity, or It is presumed that hydroxide ions having a high electrical conductivity per molar concentration are replaced by relatively very small silica.

  As the break progresses further, the amount of break ions increases and the specific resistance rapidly decreases.

  Accordingly, in the present invention, when the temporary specific resistance increase (or electrical conductivity decrease) at the beginning of the break of boron and silica is detected, water sampling from the anion exchange resin tower 3 is stopped, and the anion exchange resin is stopped. The tower 3 is regenerated, exchanged, stopped to flow through the anion exchange resin, or changed in water flow conditions (preferably, regeneration or exchange (in the case of a non-regenerative ion exchange apparatus)). Thereby, the water sampling is reliably stopped before the quality of the pure water fed from the anion exchange resin tower 3 to the pure water tank 4 is significantly lowered (that is, the specific resistance is remarkably lowered or the electrical conductivity is remarkably raised). An anion exchange resin is regenerated or exchanged. In addition, since water is collected until immediately before the full-scale break of the anion exchange resin, the exchange capacity of the anion exchange resin can be utilized up to almost the saturation capacity, and the regeneration or exchange frequency of the anion exchange resin and the regeneration or exchange cost can be reduced. It can be greatly reduced.

  In order to accurately detect a temporary increase in the specific resistance at the initial break of the anion exchange resin, it is desirable that sodium ion is contained in an amount of 5 μg / L or more in the water to be treated in the anion exchange resin tower. In this case, sodium ions are not removed by the anion exchange resin tower, but flow out into the treated water as it is, and the specific resistance of the treated water is approximately 10 MΩ · cm or less, and the accuracy of detecting a temporary increase in specific resistance is increased.

The method for determining the temporary increase in the specific resistance at the initial break of the anion exchange resin is not particularly limited, but can be conveniently performed by the following method.
Define the variables as follows:
A: Time average of resistivity values from T minutes before to the present time B: Time average of resistivity values from 2T minutes to T minutes ago C: Time average of resistivity values from 3T minutes to 2T minutes before R2 = (A + C-2B) / T ²
R1 = (A−B) / T

  Note that R2 is a simple representation of the second order differentiation of the specific resistance value over time, and R1 is a simple representation of the first order differentiation of the specific resistance value over time.

  If either the specific resistance value itself or any of R1 and R2 is larger than the respective set value, it is determined that the specific resistance has temporarily increased, and that the specific resistance increase has occurred at the initial stage of the anion break.

In order to accurately detect an increase in specific resistance, it is preferable to set the T between 5 and 60 minutes. The set values of R2 and R1 vary depending on the quality of raw water and the required water quality of the ion exchange resin device, but R2 is between 0.1 and 0.5 MΩ · cm / h ² , and R1 Is preferably set between 0.2 and 1.0 MΩ · cm / h.

  The above description relates to break detection of the anion exchange resin tower 3 in the ultrapure water production system, but break detection of other anion exchange resin towers can be performed in the same manner.

  Moreover, although the said description is based on the specific resistance of the anion exchange resin tower effluent which is a treated water of an anion exchange resin tower, it is clear that it may be based on electrical conductivity instead of a specific resistance.

  The ion exchange resin apparatus of the present invention measures the specific resistance of the treated water of the anion exchange resin layer, and based on the results, as described above, when an increase in the specific resistance at the initial stage of anion break is detected, The water flow is stopped, and for example, the water to be treated can be automatically stopped by operating an on-off valve linked to the arithmetic unit 7 in FIG. In addition, when an increase in specific resistance at the initial stage of anion break is detected, the water to be treated can be stopped and an alarm can be issued.

[Example 1]
Raw water was treated using the system shown in FIG. The main conditions are as follows.
Cation exchange resin: Diaion SKIB manufactured by Mitsubishi Chemical Corporation. 2900L
Anion exchange resin: Diaion SA12A manufactured by Mitsubishi Chemical Corporation. 2900L
Decarbonation tower: Gas-liquid contact method (filler: net ring)
Specific resistance meter: CM-31RW (for pure water) manufactured by TOA DK Corporation
Raw water: Industrial water. Electrical conductivity 20mS / m
Silica 30mg / L, Boron 5μg / L
Sodium concentration at the inlet of the anion exchange resin tower: 0.02 mg / L

  The measurement results of the specific resistance, the boron concentration and the silica concentration of the treated water from the start of water flow are shown in FIG. Boron concentration and silica concentration were measured by ICP-MS.

  As shown in FIG. 1, at the initial break of boron and silica, the specific resistance temporarily increases from 2.5 MΩ · cm to about 3.7 MΩ · cm, and then decreases to 0.5 MΩ · cm or less. Therefore, when the specific resistance increases to 3.0 MΩ · cm or more, or when the specific resistance increases by 0.5 MΩ · cm or more than the specific resistance, water sampling of the anion exchange resin tower is stopped and the anion exchange resin It was recognized that pure water can be efficiently produced by controlling the regeneration.

In order to determine a temporary increase in specific resistance, the conditional expression R2 = (A + C−2B) / T ²
R1 = (A−B) / T
In this case, T = 10 min = 0.167 h. Further, the determination reference value for specific resistance was set to 3.0 MΩ · cm, the determination reference value for R1 was set to 0.3 MΩ · cm / h, and the determination reference value for R2 was set to 0.3 MΩ · cm / h ² . As a result, R1 reaches the judgment reference value earliest, and the increasing tendency of the specific resistance can be caught at an early stage where the boron concentration is as low as 1 μg / L, and water sampling is stopped and anion exchange resin regeneration is reliably executed. We were able to. Further, the adoption water (Conventionally, sets the adopted water to 900 meters ³ / cycle, had to perform the reproduction when it reaches the setting adopted water.) Per cycle could be extended from 900 meters ³ to 1100 m ³ .

[Comparative Example 1]
In Example 1, when the resistivity was experimentally reduced to 1 MΩ · cm or less, the water sampling was stopped. As a result, the silica and boron concentrations in the treated water became extremely high, and the production of ultrapure water on the latter stage side. It was estimated that process stability was compromised.

[Example 2]
Except that the amount of ion exchange resin is as follows, and the inlet conductivity is 12 mS / m, the inlet boron is 7 μg / L, the inlet silica is 2.6 mg / L, and the anion exchange resin tower inlet sodium is 0.09 mg / L. The same test as in Example 1 was performed.
Cation exchange resin: Diaion SKIB manufactured by Mitsubishi Chemical Corporation. 200L
Anion exchange resin: Diaion SA10A manufactured by Mitsubishi Chemical Corporation. 200L
As a result, the specific resistance of the treated water was as follows.
Initial: 1.8 MΩ · cm
Temporary increase maximum value (20 h after the start of water flow): 4.8 MΩ · cm
The water passage time until the specific resistance reached 1 MΩ · cm was 24 h.
In this example, R1 detected the specific resistance increase earliest, the value of R1 at that time was 0.3 MΩ · cm / h, and the detected time was 17.5 h after the start of water flow.

[Example 3]
Anion exchange resin was packed 500 mm using an acrylic column. The resin is PA418 (strongly basic anion exchange resin (type II) manufactured by Mitsubishi Chemical Corporation). Using raw water having an electrical conductivity of 68 mS / m, silica of 20 mg / L, and boron of 10 μg / L, an anion exchange resin tower inlet sodium of 0.17 mg / L, and a water passage test to the anion exchange resin were conducted. The specific resistance of water was as follows.
Initial: 0.2 MΩ · cm
Temporary increase maximum value (7.3 hours after the start of water flow): 0.52 MΩ · cm
Moreover, the water passing time when the specific resistance was 0.1 MΩ · cm was 8.1 h.
In this example, R2 detected the specific resistance increase earliest, the value of R2 at that time was 0.1 MΩ · cm / h ² , and the detected time was 6.1 h after the start of water flow.

  From the results of Examples 2 and 3 above, it can be seen that efficient pure water can be produced by detecting a temporary increase in specific resistance, stopping water flow, and regenerating the anion exchange resin.

DESCRIPTION OF SYMBOLS 1 Cation exchange resin tower 2 Decarbonation tower 3 Anion exchange resin tower 4 Pure water tank 5 Ultrapure water production process 6 Specific resistance meter 7 Arithmetic unit

Claims (4)

The water to be treated is passed through the anion exchange resin layer for anion exchange treatment, the specific resistance or electrical conductivity of the obtained treated water is measured, and the anion exchange resin is regenerated or exchanged based on the measurement result. In the operation method of the ion exchange resin device,
Detection of an increase in specific resistance or a decrease in electrical conductivity in the initial break of boron and silica in the treated water, and based on the detection result, regeneration of the anion exchange resin, exchange, suspension of water flow to the anion exchange resin, or A method for operating an ion exchange resin apparatus, wherein the water flow condition is changed.   In claim 1, when the specific resistance or its increase rate is increased to a predetermined value, or when the electrical conductivity or its decrease rate is decreased to a predetermined value, the anion exchange resin is regenerated or replaced. To operate the ion exchange resin apparatus. In claim 2, the next R2 or R1 is calculated based on the following variables A, B, C, and when R2 or R1 becomes a predetermined value or more, the anion exchange resin is regenerated or exchanged. To operate the ion exchange resin apparatus.
A: Time average of resistivity values from T minutes before to the present time B: Time average of resistivity values from 2T minutes to T minutes ago C: Time average of resistivity values from 3T minutes to 2T minutes before R2 = (A + C-2B) / T ²
R1 = (A−B) / T In an ion exchange resin apparatus including an anion exchange resin layer through which water to be treated is passed,
A means for measuring the specific resistance of the treated water of the anion exchange resin layer, and from the measured value, the next R2 or R1 is calculated based on the following variables A, B, C, and R2 or R1 An ion exchange resin apparatus, comprising: means for stopping water flow of the treated water to the anion exchange resin layer.
A: Time average of resistivity values from T minutes before to the present time B: Time average of resistivity values from 2T minutes to T minutes ago C: Time average of resistivity values from 3T minutes to 2T minutes before R2 = (A + C-2B) / T ²
R1 = (A−B) / T

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