JP7758068B2 - Mixed ion exchange resin separation column and mixed ion exchange resin separation method using the same - Google Patents

Description

The present invention relates to a separation tower for separating mixed ion exchange resins used in ion exchange devices for pure water production systems, etc., and a method for separating mixed ion exchange resins using the same.

Typically, pure water production systems remove impurities from raw water to increase its purity. To remove ionic impurities, i.e., anionic and cationic impurities, an ion exchange unit filled with a mixture of anion and cation exchange resins is commonly used. In this ion exchange unit, once the ion exchange resin removes an amount of ions equivalent to its ion exchange capacity, any further ionic impurities cannot be removed and break through. Therefore, after a certain amount of water has been treated, the ion exchange resins are recovered from the ion exchange unit 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 unit for reuse.

The quality of treated water using this mixed ion exchange resin is determined by the regeneration state of the ion exchange resin, but to maintain a high level of regeneration state of the resin, it is necessary to minimize reverse regeneration. Reverse regeneration occurs when cation exchange resin contaminated with anion exchange resin is regenerated with an acid solution such as hydrochloric acid or sulfuric acid, resulting in the anion exchange resin being regenerated into Cl form or _SO4 form, or when anion exchange resin contaminated with cation exchange resin is regenerated with an alkaline solution such as sodium hydroxide, resulting in the cation exchange resin being regenerated into Na form.

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

Therefore, a mixed ion exchange resin separation tower, such as the one 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. The bottom of the tower body 1A is equipped 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. A water collection plate 4 is located above the discharge nozzles 2A of the separation tower body 1A. An anion exchange resin withdrawal section (not shown) is located near the middle of the separation tower 1 in the vertical direction, and a cation exchange resin withdrawal section (not shown) is located below that. Separation tower 1 also has inlet and outlet ports at its bottom, and a fill port for used mixed resin and a sight glass on its upper side, but these are omitted for ease of explanation.

A method for accurately separating anion exchange resin and cation exchange resin using such a mixed ion exchange resin separation tower 1 involves introducing the ion exchange resin (a mixed resin of anion exchange resin and cation exchange resin) R used in the condensate demineralization tower to separate the anion exchange resin and cation exchange resin. After water W is injected, 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 in the upper layer is then selectively extracted and transferred to an anion exchange resin regeneration tower, where it is regenerated with alkali. The cation exchange resin remaining in the cation exchange resin regeneration tower is then regenerated with acid in the cation exchange resin regeneration tower (Patent Documents 1 and 2).

Japanese Patent Application Laid-Open No. 2019-181363 Japanese Patent Application Laid-Open No. 2020-75226

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

The present invention was made in consideration of the above-mentioned problems, and aims to provide a separation tower that can separate mixed ion exchange resins used in ion exchange devices, etc. with high precision. The present invention also aims to provide a method for separating mixed ion exchange resins that can separate mixed ion exchange resins used in ion exchange devices, etc. with high precision.

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

In the above invention (Invention 1), it is preferable to have a flow rate adjustment means that can adjust the amount of liquid passing through the liquid injection section, and a control means that controls the flow rate adjustment means based on data on the interface position between the ion exchange resin and the liquid detected by the detection means (Invention 2).

According to these inventions (Inventions 1 and 2), the inventors investigated the factors behind the limited separation accuracy of mixed ion exchange resins even when separating each ion exchange resin by specific gravity. As a result, they found that, in order to reuse mixed ion exchange resins, it is common to pass the liquid through them in an upward flow and separate them by taking advantage of the difference in sedimentation velocity due to differences in specific gravity. However, when a large amount of crushed resin is contained, the crushed resin changes its sedimentation velocity, making it impossible to separate by specific gravity. Therefore, by monitoring the interface position between the ion exchange resin and the liquid in the separation tower 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 tower but does not reach the discharge port when passing the liquid in an upward flow, and only the crushed resin, which is likely 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 cation exchange resin.

In the above invention (Invention 2), it is preferable that 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 (Invention 3).

According to this invention (Invention 3), mixed resins of anion exchange resin and cation exchange resin are widely used, and since the two are easily separated by taking advantage of the difference in specific gravity, they are suitable for application to the separation column of Invention 2.

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).

This invention (Invention 4) makes it possible to easily and accurately monitor the interface position between the ion exchange resin and the liquid in the separation column.

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

This invention (Invention 5) makes it possible to easily and accurately monitor the interface position between the ion exchange resin and the liquid in the separation column.

Secondly, the present invention provides a method for separating mixed ion exchange resins, in which a mixed ion exchange resin of two or more types is filled into a mixed ion exchange resin separation tower having a liquid inlet at the bottom and a discharge port at the top, and when liquid is passed through the separation tower in an upward flow from the liquid inlet, the position of the interface between the mixed ion exchange resin and the liquid in the separation tower is detected, and the amount of liquid passing through the liquid inlet is controlled based on this detected interface position (Invention 6).

According to this invention (Invention 6), the position of the interface between the ion exchange resin and the liquid inside the separation tower is monitored, and the amount of liquid passing through the liquid injection section is controlled so that the mixed ion exchange resin reaches the top of the separation tower but does not reach the discharge section when the liquid is passed through in an upward flow, and only the crushed resin that is prone to floating is discharged from the discharge section. This makes it possible to remove the crushed ion exchange resin and clearly separate the anion exchange resin and cation exchange resin.

In the above invention (Invention 6), it is preferable that 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 (Invention 7).

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

In the above inventions (Inventions 6 and 7), it is preferable to detect the interface position between the ion exchange resin and the liquid in the separation column using an ultrasonic or optical interface sensor (Invention 8).

This invention (Invention 8) makes it possible to easily and accurately monitor the interface position between the ion exchange resin and the liquid in the separation column.

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

The above invention (Invention 9) makes it possible to easily and accurately monitor the interface position between the ion exchange resin and the liquid in the separation column.

The mixed ion exchange resin separation tower of the present invention has a detection means for detecting the interface position between the ion exchange resin and liquid in the separation tower when liquid is passed through the tower in an upward flow from the liquid inlet. By monitoring the interface position between the ion exchange resin and liquid in the separation tower and controlling the amount of liquid passing through the liquid inlet 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 crushed resin that is prone to floating is discharged from the discharge port, the crushed ion exchange resin can be removed, and the anion exchange resin and cation exchange resin can be clearly separated.

1 is a schematic diagram showing a separation column for mixed ion exchange resins according to a first embodiment of the present invention. FIG. FIG. 2 is a schematic diagram showing a backwashing step of the mixed ion exchange resin using a separation column according to the embodiment. FIG. 3 is an enlarged view showing a backwashing step of the mixed ion exchange resin using a separation column according to the embodiment. FIG. 2 is a schematic diagram showing a separation column for mixed ion exchange resins according to a second embodiment of the present invention. FIG. 1 is a schematic diagram showing a conventional mixed ion exchange resin separation column.

Below, one embodiment of the mixed ion exchange resin separation column of the present invention will be described in detail with reference to the attached drawings.

[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. A control means (not shown), such as a personal computer, is also provided to control the flow controller 12 based on the detection value of the interface sensor 11. An ultrasonic or optical sensor can be used as the interface sensor 11. 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.

In this type of mixed ion exchange resin separation tower 1, the space above the water collection plate 4 of the separation tower body 1A is filled with used mixed ion exchange resin R to a degree that occupies approximately 40 to 70 volume percent. In this embodiment, the mixed ion exchange resin R is a mixed resin containing at least one type of anion exchange resin and one type of 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 positions described above are set based on the amount (volume) of the mixed ion exchange resin, the ratio of anion exchange resin to cation exchange resin, and a safety factor.

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

First, the used mixed ion exchange resin R packed inside the ion exchange device 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 inlet/outlet at the bottom of the separation column 1 to fill the column 1 with water.

Next, in the backwashing process, liquid water (pure water) W is discharged from multiple discharge nozzles 2A and passed through in an upward flow to backwash the used ion exchange resin R. As a result, as shown in Figure 2, the mixed ion exchange resin R occupies approximately 40 to 70 volume percent of the space above the water collecting plate 4, and so is dispersed throughout the entire 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 to prevent the mixed ion exchange resin R from flowing out of the drainage pipe 3 due to the upward flow.

As the crushed ion exchange resin rises to the top over time, the interface position between the ion exchange resin R and the pure water W in the separation tower 1 is continuously monitored using the interface sensor 11. The flow rate controller 12 controls the amount of pure water W discharged from the discharge nozzle 2A 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 discharge water 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 discharge water W1.

The longer the time for this upward backwashing process, the more crushed ion exchange resin can be removed, which is preferable, but if it is too long, work efficiency will decrease, so a time of approximately 30 to 120 minutes is preferable. In particular, in the backwashing process for the duration described above, the upward backwashing is performed at a water flow rate of, for example, approximately LV3m/h to 15m/h, while the discharge rate of pure water W is controlled by the flow rate controller 12 so that the crushed ion exchange resin rises to the top due to the stirring effect. This allows the crushed fine resin to be reliably and efficiently discharged from the drainage pipe 3 of the separation tower 1.

After backwashing, the crushed ion exchange resin is discharged and allowed to settle, allowing the remaining intact ion exchange resin R to settle. Because anion exchange resin A and cation exchange resin 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 resin settles at the bottom and the anion exchange resin settles at the top. After backwashing, pure water can be discharged and injected through the bottom inlet and outlet, allowing a separate ion exchange resin separation process to be performed using a known method. The separated anion exchange resin and cation exchange resin can then be 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 accuracy of anion and cation exchange resin separation, it is preferable to leave a certain amount of resin from the anion and cation exchange resin separation boundary 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.

While the present invention has been described above based on the above-described embodiment with reference to the accompanying drawings, the present invention is not limited to the above-described embodiment and various modifications are possible. For example, while the above-described embodiment uses 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 tower 1 can be viewed may be provided at the top of the separation tower 1. A camera 14 for image analysis may be installed as a detection means through which the interior of the separation tower 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 embodiment describes the use of two types of resin, an anion exchange resin and a cation exchange resin, the present invention is also applicable to the use of multiple types of anion exchange resins and cation exchange resins of different grades or properties. Furthermore, in the present invention, ion exchange resins are not limited to anion exchange resins and cation exchange resins, but also include 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 by the fact that when separating a mixture of multiple types of ion exchange resins, pre-crushed ion exchange resins are removed; there are no particular restrictions on the subsequent separation process, and it goes without saying that various known separation methods can be applied.

The present invention will be further illustrated by the following specific examples.
[Example 1]
The ion exchange resin separation tower 1 shown in Figure 1 was filled with 2 ^m3 of a mixed resin of anion exchange resin and cation exchange resin (anion exchange resin:cation exchange resin = 50:50 (volume ratio)). A mechanism was used to control the discharge rate of pure water W from the discharge nozzle 2A based on the interface position detected by the interface sensor 11. The pure water W flowed for 1 hour while controlling the flow rate so that the resin interface was constant at the top of the tower, based on a flow rate of LV 10 m/h in an upward flow. 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. As a result, 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.

[Example 2]
The ion exchange resin separation tower 1 shown in Figure 4 was filled with 2 ^m3 of a mixed resin of anion exchange resin and cation exchange resin (anion exchange resin:cation exchange resin = 50:50 (volume ratio)). A mechanism was used to control the discharge rate of pure water W from the discharge nozzle 2A based on the interface position detected by the image analysis camera 14 through the window (sight glass) 13 of the separation tower 1. Water was passed through the tower for 1 hour while controlling the flow rate of pure water W so that the resin interface was constant at the top of the tower, based on a flow rate of LV 10 m/h in an upward flow. 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 rates of other ion exchange resins were measured. As a result, 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 during the 1-hour water flow was confirmed, and the loss of intact resin from the separation tower 1 was 0%. These results are shown in Table 1 together with the backwashing conditions. These results are shown in Table 1 together with the backwashing conditions.

[Comparative Example 1]
The mixed ion exchange resin separation tower 1 shown in Figure 5 was filled with 2 ^m3 of a mixed resin of anion exchange resin and cation exchange resin (anion exchange resin:cation exchange resin = 50:50 (volume ratio)), and water was passed through it in an upward flow at LV5 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 extracted and the contamination rate of other ion exchange resins was measured. As a result, the contamination rates of cation exchange resin in anion exchange resin and anion exchange resin in cation exchange resin were each 0.1%. In addition, the amount of intact resin flowing from separation tower 1 into the wastewater tank after 1 hour of water flow was confirmed, and the loss of intact resin from the separation tower was 0%. These results, along with the backwash conditions, are shown in Table 1.

[Comparative Example 2]
The mixed ion exchange resin separation tower 1 shown in Figure 5 was filled with 2 ^m3 of a mixed resin of anion exchange resin and cation exchange resin (anion exchange resin:cation exchange resin = 50:50 (volume ratio)), and water was passed through it in an upward flow at LV 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 extracted and the contamination rate of other ion exchange resins was measured. As a result, the contamination rates of cation exchange resin in anion exchange resin and anion exchange resin in cation exchange resin were each 0.05%. In addition, the amount of intact resin flowing from separation tower 1 into the wastewater tank after 1 hour of water flow was confirmed, and the loss rate of intact resin from the separation tower was 30%. These results, along with the backwash conditions, are shown in Table 1.

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 adjusting 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 Effluent water

Claims (8)

A mixed ion exchange resin separation column for separating a mixed ion exchange resin of two or more kinds of ion exchange resins, the column having a liquid inlet at a bottom and a discharge port at a top,
the mixed ion exchange resin comprises crushed resin;
a detection means for detecting an interface position between the mixed ion exchange resin and a liquid in the separation column when the liquid is passed through the liquid injection port into the separation column in an upward flow manner;
a flow rate adjusting means capable of adjusting the amount of liquid passing through the liquid injecting portion;
a control means for controlling the flow rate adjusting means based on data on the interface position between the mixed ion exchange resin and the liquid detected by the detection means;
The control means controls the flow rate adjusting means so that the crushed resin is discharged from the discharge section by an upward flow from the injection section during backwashing of the mixed ion exchange resin. 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. A mixed ion exchange resin separation tower according to claim 1 or 2, wherein the detection means for detecting the interface position between the mixed ion exchange resin and the liquid in the separation tower is an ultrasonic or optical interface sensor. A mixed ion exchange resin separation tower according to claim 1 or 2, wherein the separation tower has a window through which the interior of the separation tower can be viewed from the outside, and the detection means for detecting the position of the interface between the mixed ion exchange resin and the liquid within the separation tower is an image analysis means capable of viewing the resin interface through the window. A method for separating a mixture of two or more ion exchange resins, comprising:
the mixed ion exchange resin comprises crushed resin;
Filling a mixed ion exchange resin separation column having a liquid inlet at the bottom and a discharge port at the top with the mixed ion exchange resin;
detecting an interface position between the mixed ion exchange resin and the liquid in the separation tower after the liquid is passed through the liquid injection port in an upward direction into the separation tower;
and controlling the amount of liquid passing through the liquid injection unit based on the detected interface position,
The controlling step includes controlling the amount of liquid passing through the liquid injection section so that the crushed resin is discharged from the discharge section by an upward flow from the liquid injection section during backwashing of the mixed ion exchange resin. The mixed ion exchange resin separation method according to claim 5, 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. The mixed ion exchange resin separation method according to claim 5 or 6, wherein the interface position between the mixed ion exchange resin and the liquid in the separation column is detected using an ultrasonic or optical interface sensor. The method for separating mixed ion exchange resins according to claim 5 or 6, wherein the separation tower has a window through which the interior of the separation tower can be viewed from the outside, and the position of the interface between the mixed ion exchange resin and the liquid in the separation tower is detected using image analysis means that can be viewed through the window.