Separation tower for mixture of ion-exchange resins and method for separating mixture of ion-exchange resins using same

Abstract

A separation tower 1 for a mixture of ion-exchange resins includes a water supply pipe 2 and a plurality of ejection nozzles 2A, serving as a water supply part provided in the bottom of a cylindrical separation tower main body 1A, and further includes a water discharge pipeline 3, serving as a discharge part, connected to the top of the main body. A water collection plate 4 is provided in the separation tower main body 1A on the upper side of the ejection nozzles 2A. An interface sensor 11 is inserted from the top of the separation tower main body 1A, as a detection means for detecting the location of the interface between an ion-exchange resin and a liquid, and a flow rate controller 12 is provided in the water supply pipe 2 as a means for flow rate regulation. Also provided is a control means (not shown), e.g., a personal computer, for controlling the flow rate controller 12 on the basis of detection values from the interface sensor 11. This separation tower enables a mixture of ion-exchange resins used in an ion-exchange device, for example, to be separated with a high degree of accuracy.

Description

Mixed ion exchange resin separation column and mixed ion exchange resin separation method using the same

[0001] The present invention relates to a separation column for separating mixed ion exchange resins used in an ion exchange device for use in a pure water production system, and a method for separating mixed ion exchange resins using the same.

[0002] Typically, pure water production systems remove impurities from raw water to improve its purity. To remove ionic impurities, i.e., anionic and cationic impurities, an ion exchange device packed with a mixture of anion exchange resin and cation exchange resin is commonly used. In this ion exchange device, once the ion exchange resin removes ions equivalent to its ion exchange capacity, any further ionic impurities cannot be removed and break through. Therefore, after treating a certain amount of water, the ion exchange resins are recovered from the ion exchange device and separated. They are then regenerated in a cation exchange resin regeneration tower and an anion exchange resin regeneration tower using sulfuric acid or caustic soda, respectively, and then re-filled into the ion exchange device for reuse.

[0003] The quality of treated water using this mixed ion exchange resin is determined by the regeneration state of the ion exchange resin. In order to maintain a high level of regeneration state of the resin, it is necessary to prevent reverse regeneration as much as possible. Reverse regeneration is a process in which the anion exchange resin becomes Cl-type or SO-type when a cation exchange resin containing an anion exchange resin is regenerated with an acid solution such as hydrochloric acid or sulfuric acid. ４ When an anion exchange resin contaminated with cation exchange resin is regenerated with an alkaline solution such as sodium hydroxide, the cation exchange resin is regenerated into the Na form.

[0004] To prevent this reverse regeneration from occurring, when regenerating a mixed ion exchange resin of two or more types of ion exchange resins, it is necessary to separate the cation exchange resin and the anion exchange resin as completely as possible and to minimize the mixing of the anion exchange resin into the cation exchange resin and vice versa.

[0005] Therefore, a mixed ion exchange resin separation tower as shown in Figure 5 is used to separate the cation exchange resin and the anion exchange resin. In Figure 5, the mixed ion exchange resin separation tower 1 has a cylindrical separation tower body 1A. A water supply pipe 2 and a plurality of discharge nozzles 2A are provided at the bottom of the tower body 1A as a liquid inlet, and a drainage pipe 3 is connected to the top as a discharge port. A water collecting plate 4 is disposed above the discharge nozzles 2A of the separation tower body 1A. An anion exchange resin outlet (not shown) is provided near the middle of the separation tower 1 in the vertical direction, and a cation exchange resin outlet (not shown) is provided below that. Separation tower 1 also has inlet and outlet ports at the bottom, and a fill port for used mixed resin and a sight glass on the upper side, but these are omitted for ease of explanation.

[0006] A method for accurately separating anion exchange resins and cation exchange resins using such a mixed ion exchange resin separation column 1 has been proposed, in which ion exchange resin R (a mixed resin of anion exchange resin and cation exchange resin) used in a condensate demineralization tower for condensate demineralization is introduced into the cation exchange resin separation column 1, water W is injected, and backwash water is passed upward from below to separate the mixed ion exchange resin into two layers, anion exchange resin and cation exchange resin, due to the difference in specific gravity. The anion exchange resin constituting the upper layer is then selectively extracted and transferred to an anion exchange resin regeneration column for regeneration with alkali. The cation exchange resin remaining in the cation exchange resin regeneration column is then regenerated with acid in the cation exchange resin regeneration column (Patent Documents 1 and 2).

[0007] JP 2019-181363 A JP 2020-75226 A

[0008] However, in recent years, when a mixed ion exchange resin is used to produce high-purity pure water, there has been a demand for a more precise separation of anion exchange resin and cation exchange resin, but there are limitations to the conventional separation methods described in Patent Documents 1 and 2. In particular, when the mixed ion exchange resin contains a large amount of crushed resin, there is a problem in that separation accuracy is low.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a separation column capable of separating with high precision mixed ion exchange resins used in ion exchange devices, etc. Another object of the present invention is to provide a separation method for mixed ion exchange resins capable of separating with high precision mixed ion exchange resins used in ion exchange devices, etc.

[0010] In view of the above object, the present invention first provides a mixed ion exchange resin separation column for separating a mixed ion exchange resin of two or more types, which has a liquid inlet at the bottom and a liquid outlet at the top, and which has a detection means for detecting the position of an interface between the mixed ion exchange resin and a liquid in the separation column when the liquid is passed through the separation column in an upward direction from the liquid inlet (Invention 1).

[0011] In the above invention (Invention 1), it is preferable to have a flow rate adjusting means capable of adjusting the amount of liquid passing through the liquid injection section, and a control means for controlling the flow rate adjusting means based on the interface position data between the ion exchange resin and the liquid detected by the detection means (Invention 2).

[0012] According to the inventions (Inventions 1 and 2), the inventors have investigated the factors that limit the accuracy of gravity separation of each ion exchange resin in a mixed ion exchange resin. As a result, they have found that, while the usual method of recycling mixed ion exchange resins is to pass them through an upward flow column to separate them by taking advantage of the difference in sedimentation velocity due to the difference in specific gravity, if a large amount of crushed resin is contained, gravity separation is not always possible because the crushed resin changes its sedimentation velocity. Therefore, by monitoring the interface between the ion exchange resin and the liquid in the separation column and controlling the amount of liquid passing through the liquid injection port so that the mixed ion exchange resin reaches the top of the separation column but does not reach the discharge port, and only the crushed resin, which tends to float, is discharged from the discharge port, it is possible to remove the crushed ion exchange resin and clearly separate the anion exchange resin and the cation exchange resin.

[0013] In the above invention (Invention 2), the mixed ion exchange resin of two or more types of ion exchange resins preferably contains at least one type of anion exchange resin and one or more types of cation exchange resin (Invention 3).

[0014] According to this invention (Invention 3), a mixed resin of an anion exchange resin and a cation exchange resin is widely used, and the two are easily separated by taking advantage of the difference in specific gravity, making it suitable for application to the separation column of Invention 2.

[0015] In the above inventions (Inventions 1 to 3), it is preferable that the detection means for detecting the interface position between the ion exchange resin and the liquid in the separation column is an ultrasonic or optical interface sensor (Invention 4).

[0016] According to this invention (Invention 4), the position of the interface between the ion exchange resin and the liquid in the separation column can be monitored simply and accurately.

[0017] In the above inventions (Inventions 1 to 3), it is preferable that the separation tower has a window through which the inside of the separation tower can be observed from the outside, and that the detection means for detecting the position of the interface between the ion exchange resin and the liquid in the separation tower is an image analysis means capable of observing the resin interface through the window (Invention 5).

[0018] According to this invention (Invention 5), the position of the interface between the ion exchange resin and the liquid in the separation column can be monitored simply and accurately.

[0019] In a second aspect, the present invention provides a method for separating mixed ion exchange resins, comprising filling a mixed ion exchange resin of two or more types into a mixed ion exchange resin separation column having an inlet at the bottom and an outlet at the top, passing a liquid through the inlet in an upward direction into the separation column, detecting the position of the interface between the mixed ion exchange resin and a liquid in the separation column, and controlling the amount of liquid passing through the inlet based on the detected position of the interface (Invention 6).

[0020] According to this invention (Invention 6), the position of the interface between the ion exchange resin and the liquid in the separation tower is monitored, and the amount of liquid passing through the liquid injection port is controlled so that the mixed ion exchange resin reaches the top of the separation tower but does not reach the discharge port when the liquid is passed through in an upward flow, and only the crushed resin that is likely to float is discharged from the discharge port. This allows the crushed ion exchange resin to be removed, and the anion exchange resin and the cation exchange resin to be clearly separated.

[0021] In the above invention (Invention 6), the mixed ion exchange resin of two or more types of ion exchange resins preferably contains at least one type of anion exchange resin and one or more types of cation exchange resin (Invention 7).

[0022] According to this invention (Invention 7), mixed resins of anion exchange resin and cation exchange resin are widely used, and the two are easily separated by taking advantage of the difference in specific gravity, making them suitable for applying the separation method of Invention 6.

[0023] In the above inventions (Inventions 6 and 7), it is preferable that the position of the interface between the ion exchange resin and the liquid in the separation column is detected by an ultrasonic or optical interface sensor (Invention 8).

[0024] According to this invention (Invention 8), the position of the interface between the ion exchange resin and the liquid in the separation column can be monitored simply and accurately.

[0025] In the above inventions (Inventions 6 and 7), it is preferable that the separation tower has a window through which the inside of the separation tower can be observed from the outside, and the position of the interface between the ion exchange resin and the liquid in the separation tower is detected by image analysis means that can be observed through the window (Invention 9).

[0026] According to the above invention (Invention 9), the position of the interface between the ion exchange resin and the liquid in the separation column can be monitored simply and accurately.

[0027] The mixed ion exchange resin separation column of the present invention has a detection means for detecting the position of the interface between the ion exchange resin and the liquid in the separation column when the liquid is passed through the column in an upward flow from the liquid injection section. Therefore, by monitoring the position of the interface between the ion exchange resin and the liquid in the separation column and controlling the amount of liquid passing through the liquid injection section so that the mixed ion exchange resin reaches the top of the separation column but does not reach the discharge section when the liquid is passed through in an upward flow, and only the crushed resin that is likely to float is discharged from the discharge section, the crushed ion exchange resin can be removed and the anion exchange resin and the cation exchange resin can be clearly separated.

[0028] Fig. 1 is a schematic diagram showing a mixed ion exchange resin separation tower according to a first embodiment of the present invention; Fig. 2 is a schematic diagram showing a backwashing process using the mixed ion exchange resin separation tower according to the embodiment; Fig. 3 is an enlarged view showing a backwashing process using the mixed ion exchange resin separation tower according to the embodiment; Fig. 4 is a schematic diagram showing a mixed ion exchange resin separation tower according to a second embodiment of the present invention; Fig. 5 is a schematic diagram showing a conventional mixed ion exchange resin separation tower;

[0029] Hereinafter, one embodiment of a separation column for mixed ion exchange resins according to the present invention will be described in detail with reference to the accompanying drawings.

[0030] [Mixed Ion Exchange Resin Separation Column] FIG. 1 shows a mixed ion exchange resin separation column according to a first embodiment of the present invention. In FIG. 1, the mixed ion exchange resin separation column 1 comprises a cylindrical separation column body 1A. The bottom of the column body 1A is provided with a water supply pipe 2 and multiple discharge nozzles 2A as a liquid inlet, and the top is connected to a drainage pipe 3 as a discharge port. A water collecting plate 4 is disposed above the discharge nozzles 2A of the separation column body 1A. In this embodiment, an interface sensor 11 is inserted from the top of the separation column body 1A as a detection means for detecting the interface position between the ion exchange resin and the liquid, and a flow controller 12 is provided in the water supply pipe 2 as a flow rate adjustment means. Furthermore, a control means (not shown), such as a personal computer, is provided to control the flow controller 12 based on the detection value of the interface sensor 11. The interface sensor 11 may be an ultrasonic or optical sensor. An anion exchange resin outlet (not shown) is provided near the vertical center of the separation column 1, and a cation exchange resin outlet (not shown) is provided below that. Further, the separation tower 1 is provided at its bottom with inlet and outlet ports, but these will not be described here for the sake of convenience.

[0031] In this mixed ion exchange resin separation column 1, the space above the water collecting plate 4 of the separation column body 1A is filled with used mixed ion exchange resin R to occupy approximately 40 to 70 volume percent. In this embodiment, the mixed ion exchange resin R is a mixed resin containing at least one anion exchange resin and one cation exchange resin. The ratio (volume ratio) of anion exchange resin to cation exchange resin in this mixed ion exchange resin is not particularly limited, but is approximately anion exchange resin:cation exchange resin = 30:70 to 70:30. Furthermore, the average particle size of the smaller ion exchange resin is preferably 50 to 2000 μm (as swollen). Furthermore, the anion exchange resin and cation exchange resin are preferably porous ion exchange resins. The anion exchange resin and cation exchange resin withdrawal sections are each set at their respective resin withdrawal positions depending on the packed amount (volume) of the mixed ion exchange resin, the ratio of anion exchange resin to cation exchange resin, and a safety factor.

[0032] [Method for Separating Mixed Ion Exchange Resins] Next, a method for separating mixed ion exchange resins using the separation column 1 for mixed ion exchange resins of this embodiment having the above-described configuration will be described.

[0033] First, the used mixed ion exchange resin R packed in the ion exchange apparatus is removed and packed into the mixed ion exchange resin separation column 1 through the packing port. Then, water (pure water) W is poured into the separation column 1 through the inlet / outlet at the bottom of the separation column 1 to fill the separation column 1 with water.

[0034] Next, in the backwashing process, liquid water (pure water) W is discharged from the multiple discharge nozzles 2A and passed through in an upward flow to backwash the used ion exchange resin R. As a result, the mixed ion exchange resin R occupies approximately 40 to 70 volume % of the space above the water collecting plate 4, as shown in Figure 2, and is therefore dispersed throughout the space above the water collecting plate 4. At this time, the interface position between the ion exchange resin R and the pure water W in the separation tower 1 is monitored by an interface sensor 11, and the amount of pure water W discharged from the discharge nozzles 2A is controlled by a flow rate controller 12 so that the mixed ion exchange resin R does not flow out of the drainage pipe 3 due to the upward flow.

[0035] As time passes, the crushed ion exchange resin rises to the top, so the interface position between the ion exchange resin R and the pure water W in the separation tower 1 is continuously monitored by the interface sensor 11, and the amount of pure water W discharged from the discharge nozzle 2A is controlled by the flow rate controller 12 so that the mixed ion exchange resin R does not flow out of the drainage pipe 3 due to the upward flow of water, but only the crushed resin is discharged from the drainage pipe 3 together with the wastewater W1. As a result, as shown in Figure 3, normal anion exchange resin A and cation exchange resin C do not flow out, and only the crushed ion exchange resin can be removed from the drainage pipe 3 together with the wastewater W1.

[0036] The time for this upward backwashing step is preferably longer so that the crushed ion exchange resin can be removed, but if it is too long, the work efficiency will decrease, so it is preferably about 30 to 120 minutes. In particular, in the backwashing step for the time described above, the upward backwashing is performed at a water flow rate in the range of, for example, LV 3 m / h to 15 m / h, while controlling the discharge rate of pure water W with the flow rate controller 12 so that the crushed ion exchange resin rises to the top due to the stirring effect, thereby enabling the crushed fine resin to be reliably and efficiently discharged from the drainage pipe 3 of the separation tower 1.

[0037] After backwashing, the crushed ion exchange resins are discharged and allowed to stand, allowing the remaining intact ion exchange resins R to settle. Because anion exchange resins A and cation exchange resins C have different specific gravities, they can be separated by specific gravity. Generally, cation exchange resins have a higher specific gravity than anion exchange resins, so the cation exchange resins settle at the bottom and the anion exchange resins settle at the top. After backwashing, pure water may be discharged and injected through the bottom inlet and outlet, and a separate ion exchange resin separation process may be performed using a known method. The separated anion exchange resins and cation exchange resins are then extracted from the anion exchange resin extraction section and the cation exchange resin extraction section, respectively, and regenerated in their respective regeneration towers. To improve the separation accuracy of the anion exchange resins and cation exchange resins, it is preferable to leave a certain range of resins from the separation boundary between the anion exchange resins and the cation exchange resins unseparated, taking into account a safety factor. This remaining ion exchange resin can be removed and used for the next separation of a mixed anion and cation exchange resin.

[0038] The present invention has been described above based on the above-described embodiments with reference to the accompanying drawings. However, the present invention is not limited to these embodiments and various modifications are possible. For example, while the above-described embodiments use an interface sensor 11 as a detection means, as shown in FIG. 4, a window (sight glass) 13 through which the interior of the separation column 1 can be viewed may be provided at the top of the separation column 1. A camera 14 for image analysis may be installed as a detection means through which the interior of the separation column 1 can be viewed from the outside through the sight glass 13, thereby detecting the interface between the pure water W and the resin R and controlling the flow rate of the pure water flowing upward. Furthermore, while the above-described embodiments have been described using two types of resins, an anion exchange resin and a cation exchange resin, the present invention is also applicable to cases where multiple types of anion exchange resins and cation exchange resins of different grades or properties are used. Furthermore, in the present invention, the ion exchange resin is not limited to anion exchange resins and cation exchange resins, but also includes catalyst resins in which catalytic metals are supported on these ion exchange resins, boron-selective adsorption resins, and the like. Furthermore, the present invention is characterized in that when separating a mixture of multiple types of ion exchange resins, the ion exchange resins that have been crushed in advance are excluded. There are no particular restrictions on the subsequent separation steps, and it goes without saying that various known separation methods can be applied.

[0039] The present invention will be described in more detail with reference to the following specific examples. [Example 1] In an ion exchange resin separation column 1 shown in Figure 1, 2 m of a mixed resin of anion exchange resin and cation exchange resin (anion exchange resin:cation exchange resin = 50:50 (volume ratio)) was placed. ３The separation tower was filled with pure water W, and a mechanism for controlling the discharge rate of pure water W from the discharge nozzle 2A based on the interface position detected by the interface sensor 11 was used. The flow rate of pure water W was controlled to maintain a constant resin interface at the top of the tower for one hour, based on an upward flow rate of LV10 m / h. After water flow was stopped, the settled anion exchange resin and cation exchange resin were separated, and the separated anion exchange resin and cation exchange resin were each extracted and the contamination rate of other ion exchange resins was measured. The contamination rates of cation exchange resin in anion exchange resin and anion exchange resin in cation exchange resin were each 0.01%. Furthermore, the amount of intact resin flowing from the separation tower into the wastewater tank after one hour of water flow was confirmed, and the loss rate of intact resin from separation tower 1 was 0%. These results, along with the backwash conditions, are shown in Table 1.

[0040] Example 2 In the ion exchange resin separation column 1 shown in FIG. 4, 2 m of a mixed resin of anion exchange resin and cation exchange resin (anion exchange resin:cation exchange resin=50:50 (volume ratio)) was placed. ３ The separation tower 1 was filled with pure water W, and a mechanism for controlling the discharge rate of pure water W from the discharge nozzle 2A was used based on the interface position detected by the image analysis camera 14 through the window (sight glass) 13 of the separation tower 1. The flow rate of pure water W was controlled to maintain a constant resin interface at the top of the tower with an upward flow rate of LV 10 m / h as the reference flow rate. After water flow was stopped, the settled anion exchange resin and cation exchange resin were separated, and the separated anion exchange resin and cation exchange resin were each extracted and the contamination rate of other ion exchange resins was measured. The contamination rates of cation exchange resin in the anion exchange resin and anion exchange resin in the cation exchange resin were each 0.01%. Furthermore, the amount of intact resin flowing from the separation tower into the wastewater tank after 1 hour of water flow was confirmed, and the loss rate of intact resin from separation tower 1 was 0%. These results, along with the backwash conditions, are shown in Table 1. These results are also shown in Table 1.

[0041] Comparative Example 1 In a mixed ion exchange resin separation column 1 shown in FIG. 5, 2 m of a mixed resin of anion exchange resin and cation exchange resin (anion exchange resin:cation exchange resin=50:50 (volume ratio)) was placed. ３The column was filled with water and passed through it in an upward direction at a flow rate of 5 m / h for 1 hour. After the water flow was stopped, the settled anion exchange resin and cation exchange resin were separated, and the separated anion exchange resin and cation exchange resin were each removed to measure the contamination rate of other ion exchange resins. The contamination rates of cation exchange resin in the anion exchange resin and anion exchange resin in the cation exchange resin were each 0.1%. Furthermore, the amount of intact resin flowing into the wastewater tank from separation column 1 after 1 hour of water flow was confirmed, and the loss rate of intact resin from the separation column was 0%. These results, along with the backwash conditions, are shown in Table 1.

[0042] Comparative Example 2 In the mixed ion exchange resin separation column 1 shown in FIG. 5, 2 m of a mixed resin of anion exchange resin and cation exchange resin (anion exchange resin:cation exchange resin=50:50 (volume ratio)) was placed. ３ The column was packed and water was passed through it in an upward direction at a flow rate of 20 m / h for 1 hour. After water flow was stopped, the settled anion exchange resin and cation exchange resin were separated, and the separated anion exchange resin and cation exchange resin were each removed to measure the contamination rate of other ion exchange resins. The contamination rates of cation exchange resin in the anion exchange resin and anion exchange resin in the cation exchange resin were each 0.05%. Furthermore, the amount of intact resin flowing into the wastewater tank from separation column 1 after 1 hour of water flow was confirmed, and the loss rate of intact resin from the separation column was 30%. These results, along with the backwash conditions, are shown in Table 1.

[0043]

[0044] DESCRIPTION OF SYMBOLS 1 Mixed ion exchange resin separation tower 1A Separation tower body 2 Water supply pipe 2A Discharge nozzle 3 Drainage pipe 4 Water collecting plate 11 Interface sensor (detection means) 12 Flow rate controller (flow rate adjustment means) 13 Window (sight glass) 14 Image analysis camera (detection means) R Mixed ion exchange resin A Anion exchange resin C Cation exchange resin W Pure water (liquid) W1 Discharge water

Claims

1. A mixed ion exchange resin separation column for separating a mixed ion exchange resin of two or more types of ion exchange resins, having a liquid inlet at the bottom and a liquid outlet at the top, and having a detection means for detecting the position of the interface between the mixed ion exchange resin and a liquid in the separation column when the liquid is passed through the separation column in an upward direction from the liquid inlet.

2. A mixed ion exchange resin separation tower as described in claim 1, having a flow rate adjusting means capable of adjusting the amount of liquid passing through the liquid injection section, and a control means for controlling the flow rate adjusting means based on interface position data between the ion exchange resin and the liquid detected by the detection means.

3. The mixed ion exchange resin separation column according to claim 1, wherein the mixed ion exchange resin of two or more types of ion exchange resins contains at least one type each of anion exchange resin and cation exchange resin.

4. A mixed ion exchange resin separation tower according to any one of claims 1 to 3, wherein the detection means for detecting the interface position between the ion exchange resin and the liquid in the separation tower is an ultrasonic or optical interface sensor.

5. A mixed ion exchange resin separation tower according to any one of claims 1 to 3, wherein the separation tower has a window through which the interior of the separation tower can be seen from the outside, and the detection means for detecting the position of the interface between the ion exchange resin and the liquid in the separation tower is an image analysis means capable of confirming the resin interface through the window.

6. A method for separating mixed ion exchange resins, comprising filling a mixed ion exchange resin of two or more types into a mixed ion exchange resin separation tower having an inlet at the bottom and an outlet at the top, passing liquid upward from the inlet into the separation tower, detecting the position of the interface between the mixed ion exchange resin and the liquid in the separation tower, and controlling the amount of liquid passing from the inlet based on the detected position of the interface.

7. The method for separating mixed ion exchange resins according to claim 6, wherein the mixed ion exchange resin of two or more types of ion exchange resins contains at least one type each of anion exchange resin and cation exchange resin.

8. A method for separating mixed ion exchange resins according to claim 6 or 7, wherein the interface position between the ion exchange resin and the liquid in the separation column is detected by an ultrasonic or optical interface sensor.

9. A method for separating mixed ion exchange resins as described in claim 6 or 7, wherein the separation tower has a window through which the inside of the separation tower can be seen from the outside, and the position of the interface between the ion exchange resin and the liquid in the separation tower is detected by an image analysis means that can be seen through the window.

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