JP2019141803A - Method for regenerating ion exchange device - Google Patents

Abstract

To provide a method for regenerating an ion exchange device capable of accurately regenerating an ion exchange resin.SOLUTION: A method for regenerating an ion exchange device including a step of passing a regeneration chemical liquid to an ion exchange device having an ion exchange resin layer, which detects a water quality, for example, an organic matter concentration, of a regeneration discharge liquid from the ion exchange device, and determines an end point of regeneration of the ion exchange device on the basis of the water quality. The ion exchange resin is preferably a weak basic anion exchange resin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for regenerating an ion exchange device, and more particularly to a method for regenerating an ion exchange device that is suitable when the water to be treated contains organic substances such as industrial water, river water, and well water.

  When deionizing using an ion exchange resin, the TOC component in the water to be treated is also removed by the ion exchange resin. Since the TOC component is weakly acidic, the TOC component is dissociated and adsorbed on the anion exchange resin when the pH of the water to be treated is neutral or alkaline.

  Anion exchange resins include weakly basic anion exchange resins and strong basic anion exchange resins. Weakly basic anion exchange resins are easy to regenerate and inexpensive, but their functional groups are weakly basic, so if the water to be treated is alkaline, the ion exchange capacity is poor, and neutral or acidic Only treated water is treated. Strongly basic anion exchange resins perform anion exchange in the entire pH range, but a strongly basic regeneration solution is required for regeneration. Therefore, when raw water containing a large amount of organic matter (TOC component) is treated to produce pure water, a weakly basic anion exchange resin and a strongly basic anion exchange resin are used in combination, and the anion derived from the TOC component is as weak as possible. May be removed with a basic anion exchange resin to reduce the load on the strongly basic anion exchange resin.

  When pure water is produced by an ion exchange device, ground water such as well water, river water, lake water, or a mixture thereof may be used as raw water. Since such raw water contains various impurities, pure water is produced by ion-exchange treatment of treated water from which these impurities have been removed by various treatment methods.

  Thus, for example, a method of adding polyaluminum chloride to the raw water and neutralizing the pH of the water to be treated to precipitate aluminum hydroxide and simultaneously coagulating and removing main impurities in the raw water may be employed. If the raw water for producing pure water by ion exchange treatment contains a large amount of organic substances, especially humic acid and fulvic acid, organic substances and other impurities cannot be sufficiently removed by the coagulation precipitation method. Therefore, the organic substance load to the pure water apparatus in the latter stage of the coagulation sedimentation tank increases.

  When the ion exchange resin in the ion exchange device adsorbs organic substances, the performance deterioration phenomenon of the device is rarely manifested immediately, and is often manifested over time. This is because the performance degradation of the ion exchange resin is affected by the accumulation of organic substances.

  It is known that the organic matter adsorbed on the anion exchange resin can be removed from the resin to some extent if it is regenerated with an alkaline chemical such as caustic soda. However, the organic composition of the water supply varies depending on the water source species, the area where the pure water system is installed, the season, temperature, and weather during sampling, and cannot be expressed in a clear molecular formula. In many cases, it cannot be performed accurately. That is, the organic matter attached to the anion exchange resin has no clear physical property parameters such as a selectivity coefficient. Therefore, it is not sufficiently clear how much the organic matter is sufficiently removed by flowing a chemical solution.

  In regeneration of an ion exchange device, the regeneration level (gram of regenerant per volume of ion exchanger) determined at the time of designing the ion exchange device is usually applied as it is (paragraph 0002 of Patent Document 1). This Patent Document 1 calculates the adsorption amount distribution of ions in the ion exchanger packed bed before the regeneration after the stoppage of water flow from the quality of the treated water, the water flow rate, and the water flow time. A regeneration method for an ion exchange apparatus is described, wherein the regeneration condition is calculated by calculating the adsorption amount distribution after regeneration under a plurality of regeneration conditions with respect to the adsorption amount distribution before post-regeneration. ing.

JP 2013-208565 A

  When the organic matter is contained in the water to be treated, the organic matter is adsorbed by the ion exchange resin, but the organic matter adsorption characteristic is not clear, and thus the method of Patent Document 1 cannot be accurately regenerated.

  An object of this invention is to provide the reproduction | regeneration method of the ion exchange apparatus which can reproduce | regenerate an ion exchange resin exactly.

  The method for regenerating an ion exchange apparatus according to the present invention is a method for regenerating an ion exchange apparatus having a step of passing a regenerated chemical solution through an ion exchange apparatus having an ion exchange resin layer, and detecting water quality of the regenerated effluent from the ion exchange apparatus. The end point of regeneration of the ion exchange device is determined based on the water quality.

  In one embodiment of the present invention, any of organic substance concentration, absorbance, chromaticity, and hue is detected as the water quality of the regenerated drainage.

  In one aspect of the invention, the ion exchange resin is an anion exchange resin.

  In one aspect of the present invention, the end point is the time when the water quality index value of the regenerated drainage becomes a predetermined ratio or less with respect to the initial value.

  In one embodiment of the present invention, the water quality index value of the regenerated drainage liquid is an organic substance concentration measured by UV absorbance in a wavelength region of 220 to 280 nm.

  In the regeneration method of the ion exchange apparatus of the present invention, since the end point of regeneration is determined based on the water quality of the regenerated drainage, it is possible to regenerate the ion exchange resin sufficiently and without passing the regenerative chemical liquid excessively. it can.

It is a graph which shows the result of an Example. It is a block diagram of an ion exchange system.

  In the present invention, the regenerative chemical solution is passed through the ion exchange device to regenerate the ion exchange resin. The flow direction of the regenerative chemical solution is preferably opposite to the flow direction of the water to be treated (raw water) to the ion exchange device. The raw water is preferably at least one of well water, river water, lake water, and factory effluent having the same water quality.

  As the ion exchange resin of the ion exchange apparatus, an anion exchange resin having a property of adsorbing organic substances is preferable, and a weakly basic anion exchange resin is particularly preferable. An alkaline aqueous solution such as NaOH (caustic soda) is suitable as the regenerative chemical solution. In the case of regenerating a descending circulating water type ion exchange apparatus having a weakly basic anion exchange resin layer, the regeneration condition is that an aqueous NaOH solution having a concentration of 1 to 10 wt%, particularly 2 to 4 wt% is LV = 5 to 20 m / hr, In particular, it is preferable to pass the liquid at an upward flow of 10 to 12 m / hr.

  In the present invention, the quality of the regenerated effluent flowing out from the ion exchange device is detected, and the end point of the regeneration is determined. As the water quality, it is preferable to use one or more of organic substance concentration, absorbance, chromaticity, and hue as an index value. The organic substance concentration can be measured by, for example, UV absorbance in the region of 220 to 280 nm. The absorbance at a wavelength of 260 to 270 nm may be measured using an absorptiometer and used as a water quality index value.

  The chromaticity can be measured by a chromaticity sensor. The hue may be measured visually, or may be measured by a colorimeter or a spectrocolorimeter.

  In the present invention, preferably, the regeneration level determined at the time of design is set as a minimum necessary regeneration level, and after the regeneration level is exceeded, the end point of regeneration is determined based on the organic substance concentration or the like. The end point is determined when the organic substance concentration is not detected, or when the water quality index value falls below a predetermined ratio with respect to the initial value such as the initial concentration, for example, the end point is 1/10. Moreover, it is good also as a time when coloring of drainage almost disappeared visually.

  The means for measuring the water quality of the regenerated waste liquid is preferably installed near the drain line of the regenerated chemical liquid, particularly near the chemical liquid outlet of the ion exchange device to be monitored.

  FIG. 2 shows an example of an ion exchange system including a cation exchange tower (H tower) 1 and an anion exchange tower (OH tower) 2. In this example, raw water is passed in the order of cation exchange tower 1 → anion exchange tower 2, and water treated in the anion exchange tower is introduced into the pure water tank 3. When performing regeneration, the water in the pure water tank 3 is supplied to the anion exchange tower 2 or the cation exchange tower 1 by the pump 4 and the pipe 5 or 6, and in the HCl tank 7 or the NaOH tank 8 in the middle of the pipe 5 or 6. Hydrochloric acid or NaOH aqueous solution is added and mixed by an ejector or the like. The regenerated chemical solution is passed through the anion exchange tower 2 or the cation exchange tower 1 in an upward flow. An instrument 10 for water quality measurement is installed in the immediate vicinity of the anion exchange tower 2 in the regeneration drainage outflow pipe 9 of the anion exchange tower 2.

  According to this system, it is possible to quantitatively evaluate how much contaminating organic substances have been removed from the anion exchange resin. In addition, it can be estimated in real time how much load is applied to the anion exchange resin from the start of water flow.

[Example 1]
Well water having a TOC concentration of 2 ppm was used as raw water.

  After passing raw water through an anion exchange resin tower containing 0.6 L (packed bed height: 0.5 m) of weak anion exchange resin WA-30C manufactured by Mitsubishi Chemical Corporation for 5 hours in a downward flow of SV = 120 / hr. Then, a regenerative chemical solution (NaOH 5 wt% aqueous solution) was flowed upward at 12 m / Hr. The regeneration effluent was sampled every 30-60 seconds, diluted 20-fold and analyzed for 260 nm absorbance.

  The results are shown in FIG. As shown in FIG. 1, it was quantitatively confirmed that the organic substances that were desorbed from the anion exchange resin and flowed out decreased with the regeneration time.

  The amount of organic matter discharged roughly from these absorbances can be calculated, and the amount of organic matter in the tower can be calculated from the TOC concentration of the raw water and the amount of water collected, so the amount of organic matter allowed to remain in the tower is determined from here, Regeneration should be stopped when an appropriate amount is discharged. In the first embodiment, the reproduction level determined at the time of design is about 3.5 minutes. In FIG. 1, it is preferable that the end point is a time point of 4.5 to 6.6 minutes.

1 Cation Exchange Tower 2 Anion Exchange Tower 3 Pure Water Tank

Claims (5)

  In a method for regenerating an ion exchange device having a step of passing a regenerated chemical solution through an ion exchange device having an ion exchange resin layer, the water quality of the regenerated drainage from the ion exchange device is detected, and based on this water quality, the ion exchange device A regeneration method for an ion exchange apparatus, characterized by determining an end point of regeneration.   2. The method for regenerating an ion exchange apparatus according to claim 1, wherein any one of organic substance concentration, absorbance, chromaticity, and hue is detected as the water quality of the regenerated drainage.   3. The method for regenerating an ion exchange apparatus according to claim 1, wherein the ion exchange resin is an anion exchange resin.   4. The regeneration method for an ion exchange apparatus according to claim 1, wherein the end point is a point in time at which the water quality index value of the regenerated effluent falls below a predetermined ratio with respect to the initial value.   5. The regeneration method for an ion exchange apparatus according to claim 1, wherein the water quality index value of the regenerated drainage liquid is an organic substance concentration measured by UV absorbance in a wavelength range of 220 to 280 nm.

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