JPS5815177B2 - How to regenerate mixed ion exchange resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a mixed ion exchange resin consisting of a cation exchange resin and an anion exchange resin used for desalination treatment of condensate, wherein the loaded content of the cation exchange resin is 0.1. 30%, and the loaded content of anion exchange resin is 5 to 40%.

BACKGROUND ART Conventionally, a so-called mixed bed desalination method in which an anion exchange resin and a cation exchange resin are used in combination has been used as a method for producing desalinated water.

In this method, the resin is regenerated through a backwash separation step in which the anionic and anionic ion exchange resins are separated using a water flow from below the resin, and a regeneration step in which the separated anionic and anionic ion exchange resins are regenerated with alkali and acid, respectively. , a washing step of washing the regenerated resin with water, and a mixing step of mixing both resins.

In the above backwash separation step, the resins are separated using the difference in resin specific gravity and the difference in resin particle size so that the anion exchange resin is located in the upper layer and the cation exchange resin is located in the lower layer. However, a small amount of resin always mixes with each other near the separation boundary of the resin layers, making it impossible to completely separate them.

Conventionally, a water collector for collecting and distributing a regenerating agent was usually installed near the separation interface between the two resins in such an incompletely separated state, and the regenerating agent for the anionic and anionic ion exchange resin was injected from this collector. Both resins were recycled by extracting them.

However, in this method, due to incomplete separation, the cation exchange resin located above the collector is contacted with a regenerant for the anion exchange resin, such as an aqueous sodium hydroxide solution, and N
On the other hand, the anion exchange resin located below the collector becomes a C-loaded type when it comes into contact with a regenerating agent for the cation exchange resin, such as an aqueous hydrochloric acid solution, and becomes a C-loaded type, which is the original purpose of the regeneration operation. In many cases, the purpose of converting the resin into the H form and the anion exchange resin into the OH form was significantly deviated from.

In addition, in recent years, in condensate treatment for supercritical pressure boilers and nuclear power generation, extremely high purity treated water has been required to prevent material corrosion accidents in boilers and steam generators. In the condensate treatment of pressurized water nuclear power plants, the management target for treated water quality is
7 ppb or less and chlorine ions to 0.15 ppb or less, but in order to achieve such treated water quality, the recycled content of the ion exchange resin used for mixed bed desalination treatment (strong acid positive It is necessary to increase the H engraving rate of the ion exchange resin and the OHH type rate of the strongly basic anion exchange resin. The C1 content of the anion exchange resin needs to be about 30% or less, and it is difficult to reach the above-mentioned recycled content using a regeneration method using a single water collector. .

In addition, in condensate treatment in supercritical pressure boilers and nuclear power generation equipment, it is necessary to reduce the ion concentration of the treated water to an extremely low level, so in the desalination treatment of general groundwater and tap water,
While resin is regenerated after raw water is treated to the fullest ion exchange capacity, in condensate desalination treatment, pressure loss in the resin bed due to compaction of the resin bed or accumulation of suspended solids is Generally, the flow of water is stopped when the amount of water increases or when a certain amount of water has been passed, and the resin is regenerated with a considerable amount of ion exchange capacity remaining.

Therefore, the loaded content of the anion-side ion exchange resin after condensate desalination treatment is quite low, usually 0.1 to 30% for cation exchange resins and 5 to 40% for anion exchange resins. That's about it.

If both of these resins are regenerated using a single water collector, for example, if 5% of the cation exchange resin is present above the collector, the cation exchange resin in this area will be anion exchange resin. When it comes into contact with sodium hydroxide, a resin regenerating agent, it becomes Na-loaded, and even if the cation exchange resin below the collector is 100% regenerated, the regeneration rate of the cation exchange resin as a whole is 9.
5%, that is, the loaded type content after regeneration is 5%, and depending on the case, a contradiction may occur in that the loaded type content increases due to the regeneration operation.

Such a phenomenon can similarly occur when an anion exchange resin is present in the lower part of the collector.

In the conventional method using a single collector, in order to minimize the above-mentioned disadvantageous phenomena, it is necessary to precisely align the collector position with the separation interface between the two resins, but in the condensate desalination equipment, Normally, regeneration is carried out by transferring the resin to a regeneration tower separate from the resin tower used during desalination, and due to incomplete transfer of resin, some of the resin volume transferred to the regeneration tower during each regeneration is In addition, ion exchange resins exhibit some volume changes depending on their counterion type and the ionic strength of the external liquid, so the separation interface position, which is essentially determined by the resin volume, also changes, causing collector It is very difficult to always match the separation interface with the separation interface.

When the present inventors backwashed and separated the anion-side ion exchange resin, the anion-side ion-exchange resin gradually existed in a pure state as the distance from the separation interface between both resins increased, and the anion and anion side ion-exchange resins were in a substantially pure state. It can be separated into three layers: a cation exchange resin layer and an ion exchange resin layer in a mixed state that includes the separation interface between both resins, and can be used to treat raw water that usually has an extremely low concentration of impurities, such as boiler condensate treatment. Therefore, in a mixed bed desalination equipment whose purpose is to obtain treated water of very high purity, it is better to not let the regeneration agent come into contact with the resin in the ion exchange resin layer in a mixed state, that is, it is better to not regenerate it. Focusing on improving the regeneration rate of the resin as a whole in the salt equipment, the present invention was arrived at as a result of intensive study.

That is, the gist of the present invention is to provide an ion exchange resin regeneration tower for regenerating a mixed ion exchange resin consisting of a cation exchange resin and an anion exchange resin used for desalination treatment of condensate.
Water collection and distribution pipes are provided at the upper and lower parts of the tower, and two water collection and distribution collectors are provided in the tower, upper and lower, and the upper collector backwashes the mixed ion exchange resin in the tower with an upward flow.
The height of the anion exchange resin layer is 10 to 10% higher than the separation interface formed when the anion exchange resin layer is separated into the anion exchange resin layer by natural sedimentation.
An ion exchange resin regeneration tower is installed at a position 30% above the separation interface, while the lower collector is installed at a position 10 to 30% below the height of the cation exchange resin layer from the separation interface. The treatment is performed on a layer substantially consisting of anion exchange resin existing above the lower collector and a layer substantially consisting of cation exchange resin existing below the lower collector, and ions in a mixed state between the upper collector and the lower collector. A method for regenerating a mixed ion exchange resin characterized in that the resin in the exchange resin layer is not substantially regenerated.

To explain the present invention in detail, the ion exchange resin regeneration tower used in the method of the present invention is an ion exchange resin regeneration tower for regenerating the mixed ion exchange resin used in the desalination treatment of condensate. In addition to condensate from general boilers, condensate that can be used for this purpose includes condensate from supercritical pressure boilers and light water reactor nuclear power generation equipment.

Further, examples of the cation exchange resin used in the present invention include strongly acidic cation exchange resins, and examples of the anion exchange resin include strong basic anion exchange resins, and a specific example of these products is Diaion 5KIB.

5KIBN, 5KN1, 5KN2, 5AIOB, 5AI
OBN.

5ANI etc. ("Diaion" is a registered trademark of Mitsubishi Chemical Industries, Ltd.).

) Next, the ion exchange resin regeneration tower used in the method of the present invention and the operating method for regenerating the mixed ion exchange resin using the regeneration tower will be explained clearly.

FIG. 1 is a schematic vertical cross-sectional view of one example of a regeneration tower used in the method of the present invention during resin regeneration.
In the figure, 1 is the upper main water collection and distribution pipe, 2 is the upper water collection and distribution pipe, 3 is the lower water collection and distribution pipe, 4 and 5 are the upper collector and lower collector provided in the resin layer, 6 is the resin support plate, and 7 is the shaded area 8 indicates an anion exchange resin layer, and the shaded area 8 indicates a cation exchange resin layer 9 which indicates a separation interface between both resins.

In Figure 1, the layer heights of the anion exchange resin layer and the cation exchange resin layer are 11 and 12, respectively, and the distances between the upper collector 4 and the lower collector and the resin separation interface are dl and d2, respectively. time, dl, and d2 are in the range shown by the following equation.

0.111<dl<0.311 0.1A2≦d2<0.372 Preferably 0.15AI'1≦d1<0.2! M1 0.15112<d2≦0.2572 The method for regenerating the mixed ion exchange resin packed in the regeneration tower shown in FIG. 1 is as follows.

When regenerating the anion exchange resin, an alkaline aqueous solution such as a caustic soda aqueous solution is introduced as a regenerating agent through the upper water collection and distribution pipe 2 and collected from the upper collector 4, and then desalinated water is introduced into the upper collector 4 from the upper water collection and distribution pipe 2. The resin is washed with water.

In addition, during resin regeneration and water washing, the regenerant flows from the upper coketer 4 to the lower part and comes into contact with the cation exchange resin present below the upper collector, in order to prevent the cation exchange resin from becoming loaded. Desalinated water is made to flow from the lower water collection and distribution pipe 3 to the upper collector 4.

In addition, when regenerating the cation exchange resin, an acid such as a hydrochloric acid aqueous solution is introduced as a regenerating agent from the lower water collection and distribution pipe 3,
Collected from the lower collector 5, and then transferred to the lower water collection and distribution pipe 3.
Demineralized water is distributed to the lower collector to wash the resin.

In addition, during resin regeneration, demineralized water is distributed from the upper water collection and distribution pipe 2 to the lower collector in order to prevent the regenerant from coming into contact with the anion exchange resin located above the lower collector and causing the anion exchange resin to become loaded. let

In the regeneration tower used in the method of the present invention, it is necessary to install the water collection and distribution collectors at positions within the above-mentioned specific range, but the desired effect cannot be achieved outside this range.

For example, dl<0.111, 0.172<d2<0.3A
In case 2, since the cation exchange resin exists above the upper collector, the cation exchange resin mixed in the anion exchange resin layer becomes a loaded type when the anion exchange resin layer is regenerated, so that the desired effect can be achieved. It cannot be achieved.

Also, 0.1 l < d < 0.3 l, , d2 < 0
．． 1121-1- and d<0.111. In the case of d2<0.112, the desired effect cannot be achieved for the same reason.

Also, dl>0.311. If d2>0.312, the desired effect cannot be achieved because the resin cannot be regenerated sufficiently.

As mentioned above, if the method of the present invention is used, the mixed ion exchange resin used for the desalination treatment of condensate can be regenerated at an extremely high regeneration rate. When desalination treatment is performed, treated water of extremely high purity can be obtained.

It goes without saying that the regeneration tower used in the present invention is used as a packed tower for desalination treatment.

In this case, after performing the desalting treatment, the resin may be backwashed, separated, and regenerated in the same column.

Next, the present invention will be examined in more detail using test examples, but the present invention is not limited to the following examples unless the gist thereof is exceeded.

Test Example 1 A strongly acidic cation exchange resin Diaion 5KIBN6.01 and a strong basic anion exchange resin Diaion 5A10BN 3.01, both in free form, were placed in a tube with an inner diameter of 10 cm and a height of 2.
m column and thoroughly mixed.

The particle size distribution of these resins is shown in Table 1.

This column was backwashed by flowing brine at 20 ± 1°C from below the perforated plate at a linear velocity (LV) of 10 m/hr in an upward flow for 30 minutes, then the flow was stopped and the resin was allowed to settle naturally. I let it happen.

The resin layer separated in this way was divided into 1 to 5 cm intervals in the longitudinal direction of the column, and the volume content of the cation exchange resin and anion exchange resin in each divided resin layer was measured. 99.5% or more of the anion exchange resin is 4 cm or more above (horizontal cross section of the column where the anion and yang resins have the same capacity), and 99.5% or more of the cation exchange resin is 8 CrIL or more below the separation interface. Ta.

Test Example 2 Two water collectors each having an inner diameter of 8 mm and having water collection and distribution ports in the horizontal direction were attached to a column having an inner diameter of 10 Crr and a height of 2 m at positions 65 crrL and 85 CwL from the bottom of the column.

The same 5KIBN used in Test Example 1 was used for this column, with a Na negative load type ratio of 3.0%, a regenerated type (H type) content of 97,
3. One in which the same 5AIOBN used in 6.1 and Test Example I was adjusted to have a C1 loaded type content of 28.5% and a recycled type (OH type) content of 71.5%. 01 and mixed thoroughly.

After backwashing the column for 30 minutes by flowing demineralized water at 20±1° C. upward at a linear velocity (LV) of 10 m/hr from the bottom of the column, the resin was allowed to settle naturally.

The separation interface of the anion-side resin separated in this way is located at a position 78 crn from the bottom of the column, and the layer heights of the cation exchange resin and anion exchange resin are each 78 C1? L141
cm, the distance from the separation interface to the upper collector was 7 cm, and the distance from the separation interface to the lower collector was 13 cm.

A 1N aqueous sodium hydroxide solution 121, which is a regenerant, is then introduced into the resin bed in such a state at a flow rate of 121/hr, and demineralized water 61, which is an extrusion liquid of the regenerant, is introduced from the top of the column and extracted from the collector at the top. The ion exchange resin was regenerated.

Next, demineralized water 401 was passed from the top of the column to the upper collector at a flow rate of 801/hr to wash the resin.

At this time, in order to prevent the regenerant from diffusing below the upper collector, 12A of demineralized water was poured from the bottom of the resin layer to the upper collector.
The liquid was passed at a flow rate of /hr.

Next, 2N hydrochloric acid aqueous solution 121. Next, demineralized water 121
was introduced from the bottom of the column at a flow rate of 121/hr and extracted from the collector at the bottom to regenerate the cation exchange resin.

At this time, in order to prevent the regenerant from diffusing above the lower collector, 12A of demineralized water was poured from the top of the column to the lower collector.
The liquid was passed at a flow rate of /hr.

Next, desalinated water 6 flows from the upper main water collection and distribution pipe 1 to the lower water collection and distribution pipe 3.
The resin was washed by passing water through 01 at a flow rate of 801/hr.

The ion-exchange resins on the yin and yang sides that were subjected to the regeneration treatment in this way were mixed uniformly, and 50ml of the mixture was sampled to measure the load engraving rate and the recycled form content of the ion exchange resins on each of the yin and yang sides.Table 2 shows the results. The following results were obtained.

Test Example 3 A water collector with an inner diameter of 8 mm and a water collection/distribution port in the horizontal direction was attached to a column with an inner diameter of 10 crrL and a height of 2 m at a position 78 cm from the bottom of the column.

The same loaded content as used in Test Example 2 for this column,
5KIBN 61 and 5AIOBN adjusted to recycled content
No. 31 was filled, thoroughly mixed, and backwashed and separated under the same conditions as Test Example 2.

The separation interface at this time was located at a position 78 cfrL from the bottom of the column, which was the same position as the collector.

In Test Example 2, whether the upper collector or the lower collector is used for the resin bed in such a state, this test example is completely different from Test Example 2 except that the same one collector is used. When the same treatment was applied, the results shown in Table 3 were obtained.

In other words, in the results of Test Example 3 conducted according to the conventional method, the loaded content of 5AIOBN was 2.7% higher than before regeneration.
increased by 8.5% compared to Test Example 2, and 1B in 5
The loaded N content was twice as high as in Test Example 2.

Test Example 4 Remaining resin layer 91 after sampling used in Test Example 2
Filled in a mixed state into a column with an inner diameter of 1OcrrL and a height of 1.5m, NH3510ppb and NaCl30pI)
An aqueous solution containing b was passed through the tube at a rate of LV 100 m/hr.

The quality of the treated water 48 hours after the start of water flow was as shown in Table 4, and the target of condensate treatment for pressurized water nuclear power generation was fully achieved.

Test Example 5 Remaining resin layer 91 after sampling used in Test Example 3
The mixture was packed into a column similar to that in Test Example 4, and the solution was passed under the same conditions as in Test Example 4.

The treated water quality after 48 hours is as shown in Table 5.
Compared to Test Example 4, the concentrations of both chloride ions and sodium ions were about twice as high.

[Brief explanation of drawings]

Figure 1 is a schematic vertical cross-sectional view of an example of an ion exchange resin regeneration tower during resin regeneration.
is the upper main water collection and distribution pipe, 2 is the upper water collection and distribution pipe, 3 is the lower water collection and distribution pipe, 4 is the upper collector, 5 is the lower collector, 6 is the resin support plate, the shaded part 7 is the anion exchange resin layer, the shaded part 8 9 indicates a cation exchange resin layer, and 9 indicates a separation interface between both resins.

Claims (1)

[Scope of Claims] 1. A mixed ion exchange resin consisting of a cation exchange resin and an anion exchange resin used for desalination treatment of condensate, wherein the loaded content of the cation exchange resin is 0.1 to 30%. In a method for regenerating anion exchange resin with a loaded content of 5 to 40%, water collection and distribution pipes are provided at the upper and lower parts of the tower, and two water collection and distribution collectors are installed in the tower, one above the other. The upper collector backwashes the mixed ion exchange resin in the column in an upward flow, and then allows it to settle naturally and separate into the anion and anion side ion exchange resin layers. It is installed at a position 10-30% above the height, while
The lower collector uses an ion exchange resin regeneration tower installed at a position 10 to 30% below the height of the cation exchange resin layer than the separation interface, and the regeneration is carried out using substantially anions existing above the upper collector. This is performed on the layer made of exchange resin and the layer substantially made of cation exchange resin existing below the lower collector, and substantially regenerates the resin in the ion exchange resin layer in the mixed state between the upper collector and the lower collector. A method for regenerating a mixed ion exchange resin, characterized in that: