JPH10337485A - Method for regenerating anion exchange resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regenerate anion exchange resin in a short time and at a low cost and to recover ion exchange performance by allowing a regenerant of specific concentration to flow through the anion exchange resin at a specific space velocity in the state heated at a specific temp., and bringing the regenerant, into contact with the anion exchange resin. SOLUTION: In the state that an anion exchange resin layer is heated at 40-60 deg.C, preferably at 40 - about 50 deg.C, the regenerant of low concentration is allowed to flow at high speed to regenerate it. As a heating method of the anion exchange layer, any optional method such as heating with electric heating or heating with infrared radiation, can be used, and heating with hot water is preferred. A water flow quantity of hot water is desired to be >= about one time in a volume ratio of the anion exchange resin, preferably about 1-3 times. The water flow speed is desired to be 15-40 hr<-1> at the space velocity(SV), preferably about 20-35 hr<-1> . An alkali aqueous liquid such as an ammonia aqueous liquid and a sodium hydroxide aqueous liquid can be used as the regenerant. The concentration is 1-3.5 wt.%, preferably about 2-3 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for regenerating an anion exchange resin, and more particularly to a method for regenerating an anion exchange resin used in a pure water production apparatus.

[0002]

2. Description of the Related Art In the production of pure water by a pure water production apparatus using an ion exchange resin, a step of passing water through the ion exchange resin to desalinate and a step of regenerating by passing a regenerant are used. Yes, the ion exchange resin is regenerated and used repeatedly. In the pure water production apparatus, an operation system in which the desalination step and the regeneration step are generally performed once or twice a day is adopted for the convenience of the operation.

Conventionally, ion-exchange resins are regenerated by using an acid such as hydrochloric acid or sulfuric acid for a cation exchange resin and an alkali such as sodium hydroxide for an anion exchange resin as a regenerant. . In this case, the flow rate of the regenerant is 2 to 10 hr ^-1 in terms of SV so that the contact time between the regenerant and the ion exchange resin is sufficient to complete the chemical reaction.
Reproduced by the degree. Here, as the regenerating agent, those having an acid or alkali content of about 4 to 6% by weight are used, and the height of the packed bed of the ion exchange resin is 100 to 300 cm.

In the above-mentioned conventional regeneration method, the regeneration level of the regenerant with respect to the anion exchange resin is supposed to be 80 g NaOH /
Assuming 1R, to achieve this value, 4% by weight N
It is necessary to use aOH twice the volume of the resin, and SV =
At 2 hr ^-1 , it takes about 1 hour, and at SV = 10 hr ^-1 , it takes 12 minutes.

In order to regenerate the resin, in addition to the above-mentioned injection of the regenerating agent, a step of extruding the regenerating agent, a step of washing the resin, and the like are required, and the entire regenerating process requires about 2 to 4 hours. The operation which performs regeneration and water supply twice is the limit. Further, the conventional reproducing method has a problem that the time required for the reproduction is long, so that the efficiency is low and the cost is high.

It is conceivable to lengthen the regeneration interval in order to reduce the time ratio of the resin regeneration step in the total pure water production, but in this case, it is necessary to increase the amount of ion exchange resin used for pure water production. Yes, this increases costs. On the other hand, if the regeneration interval is shortened, it is necessary to pass water at a high flow rate to desalinate in order to obtain a fixed amount of treated water from a fixed amount of ion exchange resin. In this case, surplus treated water is stored. It requires a large capacity tank, requires a large installation area, and cannot be generally adopted.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to regenerate an anion exchange resin in a short time and at low cost to recover the ion exchange capacity, and to reduce the silica adsorbed on the anion exchange resin in a short time. An object of the present invention is to propose a method for regenerating an anion exchange resin which can be efficiently desorbed, thereby reducing the size of the apparatus and in which the amount of silica leaked from the regenerated resin is small.

[0008]

According to the present invention, there is provided a method for regenerating an anion exchange resin.
An anion exchange characterized in that a regenerant having a concentration of 1 to 3.5% by weight is passed at a flow rate of 15 to 40 hr ^-1 in space velocity (SV) while being heated to 0 ° C, and is brought into contact with an anion exchange resin. This is a method for regenerating resin.

The anion exchange resin that can be regenerated by the method of the present invention is not particularly limited, and may be either a strongly basic or weakly basic anion exchange resin. Such an anion exchange resin may be a resin packed in an anion exchange resin tower, a double bed type or a mixed bed type. The anion exchange resin forming the mixed bed can be separated and regenerated. A specific example is an anion exchange resin for producing pure water.

The regeneration method of the present invention is a method in which a low-concentration regenerant is passed at a high flow rate while the anion exchange resin layer is heated to 40 to 60 ° C., preferably 40 to 50 ° C., to regenerate. is there. As a method of heating the anion exchange resin layer,
Any method such as heating by electric heating or heating by infrared rays can be used, but heating with warm water is preferred. In this case, the anion exchange resin is heated by passing pure water (warm water) at 40 to 60 ° C., preferably 40 to 50 ° C., and then a regenerating agent described below is passed at a high flow rate and brought into contact to regenerate. The method is preferred.

It is desirable that the flow rate of the hot water be at least 1 times, preferably 1 to 3 times the volume ratio of the anion exchange resin.
The water flow speed is 15 to 40 hr ^-1 in SV, preferably 20 to 40 hr ^-1 .
It is desirably 35 hr ^-1 . The water flow direction may be an upward flow or a downward flow, but an upward flow is preferable. In particular, it is preferable that the anion exchange resin, which has been ion-exchanged by passing water in a downward flow, is passed in an upward flow.

By heating the anion exchange resin before passing the regenerating agent, regeneration by the regenerating agent, in particular, desorption of silica can be performed efficiently in a short time. In this case, warming can be performed uniformly without causing thermal shock to the anion exchange resin by passing warm water through and heating.

As a regenerating agent, a conventionally used agent such as an aqueous ammonia solution or an aqueous alkali solution such as an aqueous sodium hydroxide solution can be used. Its concentration is from 1 to 3.5
%, Preferably 2 to 3% by weight, and used at a concentration lower than that of the conventional regenerant. The level of the regenerant is the same as before.

The SV of the regenerant is 15 to 40 hr ^-1 , preferably 20 to 35 hr ^-1 . The flowing direction may be an upward flow or a downward flow, but an upward flow is preferable. In particular, countercurrent regeneration in which anion exchange resin which has been ion-exchanged by passing water in a downward flow is regenerated in an upward flow is preferable. It is desirable that the temperature of the regenerant is 40 to 60 ° C, preferably 40 to 50 ° C. By regenerating at such a temperature, silica can be more completely desorbed in a short time.

Conventionally, in order to effectively utilize the regenerant, it was necessary to contact the regenerant at a low flow rate, and it was thought that regeneration was not sufficiently completed at the high flow rate as described above. By heating the resin before passing the agent and using a low-concentration regenerating agent, regeneration can be performed sufficiently and the anion exchange capacity can be restored even if the resin is passed at such a high flow rate. At the same time, it was found that silica was sufficiently desorbed.

Generally, in an ion exchange reaction for desalting in an ion exchange resin packed in a column, it is known that when a liquid is passed at a high flow rate, the length of an exchange zone becomes longer, and the amount of resin used effectively decreases. Have been. Change the length of the exchange zone to Z
(M), assuming that the filling height of the ion exchange resin is L (m), the maximum utilization rate (%) of the resin is represented by the following equation (1).

[0017] The length Z of the exchange zone is represented by the following equation (2). Z = a × LV ^b (2) [where LV is a liquid flow velocity (m / h), a is a coefficient determined by ions to be exchanged, and b is a coefficient determined by resins and ions. ]

This utilization rate indicates an effective utilization rate of the resin in the ion exchange step. For example, the filling height of the resin is 150 m.
m is about 93% in the ion exchange apparatus, and the height of the resin layer is 100 to 3 in order to obtain a practical utilization rate.
00 cm.

In the case of regeneration, unlike the utilization rate of such a resin, the utilization efficiency of the regenerating agent is a problem, and the utilization efficiency of the regenerating agent also depends on the length of the exchange zone (length in the liquid passing direction). It will be decided. In the case of regeneration at a low flow rate as in the conventional regeneration method, the length of the exchange zone is short and hardly need be taken into consideration. However, when the flow rate is high as in the present invention, the length of the exchange zone increases.

Regarding the removal of the loaded ions in the case of regeneration,
The same tendency as the ion exchange reaction for desalination was observed,
There is an exchange zone. The length of the exchange zone at the time of this regeneration becomes longer as the flow rate increases, as in the above formula (2). However, the length of the exchange zone is greatly affected by the diffusion of the regenerant into the ion exchange resin particles. When the flow rate is high, the diffusion becomes faster if the concentration of the regenerant is reduced, and the length of the exchange zone can be shortened.

In the method of the present invention, even if regeneration is performed at a high flow rate using a low-concentration regenerant, the effect of the exchange zone is reduced as much as possible and the resin utilization rate is set to 80% or more. 0.8 m or more, preferably 0.8 m
To 3 m, more preferably 0.8 to 1.5 m.

After injecting the regenerant under the above conditions,
Extrusion of the regenerant is performed by injecting pure water. The amount of pure water in the extrusion step is made the same as that of the regenerant, and the same flow rate as the regenerant, that is, SV 15 to 40 hr ⁻¹ , preferably 20 to
Water is passed at 35 hr ^-1 .

The washing step following the extrusion step is performed in the same manner as the conventional regeneration, and is performed at the same flow rate as the water sampling step for 5 to 10 minutes. The regeneration is completed as described above, and the process proceeds to the ion exchange step.

[0024]

According to the method for regenerating an anion exchange resin of the present invention, a regenerant having a concentration of 1 to 3.5% by weight and an SV of 15 to 40 hours can be obtained by heating the anion exchange resin to 40 to 60 ° C.
^{Since the} liquid is regenerated by passing through at a flow rate of ^-1 , the anion exchange resin can be regenerated in a short time and at low cost to recover the ion exchange capacity. The desorption can be performed efficiently in a short period of time, whereby the size of the apparatus can be reduced, and the amount of silica leaked from the recycled resin is small.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

Example 1 An anion exchange resin (Diaion SA12A, manufactured by Mitsubishi Kasei Kogyo Co., Ltd., trade name) was used with an inner diameter of 25 mm and a height of 1500 m.
m acrylic column was packed in 400 ml. After passing hot water through the resin, the resin was regenerated at a regeneration level of 60 g NaOH / l-R, and a test of passing Atsugi-shi water was performed. Table 1 shows the regeneration steps and the regeneration conditions. Fig. 1 shows the treated water quality of the water flow test.

[0026]

[Table 1]

Comparative Example 1 The procedure of Example 1 was repeated, except that the heating water was not passed. Table 2 shows the regeneration process and regeneration conditions, and Fig. 1 shows the treated water quality.
Shown in

[0028]

[Table 2]

From the results shown in Table 1 and FIG. 1, after passing hot water at 45 ° C., a low-concentration regenerant at 45 ° C. was passed through at a high flow rate to regenerate the anion exchange resin in a short time. It can be seen that the resin can be regenerated and the amount of silica leaked from the regenerated anion exchange resin is small.

Example 2 Two cylindrical acrylic columns having an inner diameter of 40 mm and a height of 1200 mm were prepared, and one liter of a cation exchange resin was used for one of them.
er (80 cm high) and the other anion exchange resin at 1.4
Filled liter (111 cm high). The resin in this column was treated with 80 g HCl /
A test was conducted in which regeneration was carried out at a regeneration level of 1-R, the anion exchange resin was passed through warm water, then regenerated at a regeneration level of 60 g NaOH / l-R, and water was passed through Atsugi city water.

Regeneration of the cation exchange resin was carried out by passing a regenerant through the column in an upward flow. Regeneration of the anion exchange resin was performed by passing warm water and a regenerant through the column in an upward flow.
In the water flow test, columns were connected in series so that water could flow in the order of the cation exchange resin and the anion exchange resin, and water was flown downward in both columns. Table 3 shows the regeneration conditions and water flow test conditions.

[0032]

[Table 3]

At this time, the entire reproduction time is about 36 minutes,
It was 9 hours in total with the water flow time. The amount of water produced in 24 hours a day was 2033 liter. When the test was repeated three times under the conditions of regeneration and water flow shown in Table 3, the water quality shown in FIG. 2 was obtained.

Example 3 Example 3 was carried out in the same manner as in Example 2, except that the conditions were changed as shown in Table 4.

[0035]

[Table 4]

At this time, the entire reproduction time was about 29 minutes. It is 6 hours with water passing and regeneration once each,
The daily water production was 2,400 liters. The treated water quality at this time was as shown in FIG.

COMPARATIVE EXAMPLE 2 Two cylindrical acrylic columns having an inner diameter of 65 mm and a height of 2000 mm were prepared, and one of them was provided with a cation exchange resin of 3.6.
liter (108 cm high) and the other was filled with an anion exchange resin 4.7 liter (142 cm high). The resin in this column was regenerated at a regeneration level of 80 g HCl / l-R for the cation exchange resin and 60 g NaOH / l-R for the anion exchange resin. Table 5 shows the regeneration conditions and water flow conditions.

[0038]

[Table 5]

The regeneration time was 100 minutes, which was about 31 hours including the water flow time. The amount of water produced in 24 hours a day was 2250 liter. When the test was repeated three times under the conditions of regeneration and passing water shown in Table 5, the water quality shown in FIG. 4 was obtained.

As can be seen from the above Examples 2 and 3 and Comparative Example 2, according to the method of the present invention, it is possible to obtain substantially the same volume of treated water with the same volume by using a small apparatus.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of Example 1 and Comparative Example 1.

FIG. 2 is a graph showing the results of Example 2.

FIG. 3 is a graph showing the results of Example 3.

FIG. 4 is a graph showing the results of Comparative Example 2.

Claims (1)

[Claims] 1. A method for regenerating an anion exchange resin, comprising:
While heating the anion exchange resin to 40-60 ° C,
A regenerant having a concentration of 3.5% by weight has a space velocity (SV) of 15 to 4
A method for regenerating an anion exchange resin, comprising passing a liquid at a flow rate of ⁰ hr ^-1 and bringing the liquid into contact with the anion exchange resin.