JP3147396B2 - Method for regenerating cation exchange resin in mixed bed type desalination equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for regenerating a cation exchange resin in a mixed-bed desalination apparatus comprising a strongly acidic cation exchange resin and a strongly basic anion exchange resin, and particularly to a cation exchange resin containing a small amount of anion exchange resin. To a reproduction method for reproducing a.

[0002]

2. Description of the Related Art Conventionally, when regenerating a cation and anion exchange resin in a mixed-bed type desalination apparatus, in order to avoid contact between the anion exchange resin and an acid solution such as hydrochloric acid or sulfuric acid which is a regenerant for the cation exchange resin. The cation exchange resin and the anion exchange resin are separated by using the specific gravity difference of the resins, the regenerating agent is passed through each resin, the regenerating agent is extruded, and the resin is regenerated by washing with pure water. . The method of performing such regeneration has also progressed from one-column regeneration to two-column separation regeneration, and further to an intermediate resin layer re-extraction system, thereby reducing the contact between the cation exchange resin regenerant and the anion exchange resin. However, even with such a method, it is unavoidable that about 0.3 to 1% of the anion exchange resin is mixed into the cation regeneration tower.

A condensate desalination apparatus comprising a strongly acidic cation exchange resin and a strongly basic anion exchange resin, especially PW
In the condensate desalination apparatus for R, when the anion exchange resin is used for a long time, a phenomenon occurs in which the concentration of anions such as chlorine ions and sulfate ions is hardly reduced at the time of washing with water after regeneration. The amount of anion leak due to this phenomenon is
The amount increases as the anion exchange resin is used, and the amount of leak cannot be reduced even if washing with water after regeneration is performed for a long time. The only countermeasure is to replace the anion exchange resin in the desalination unit, and the conventional method of regenerating the cation exchange resin has a problem that the life of the anion exchange resin is short.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems by effectively changing the ionic form of a small amount of anion exchange resin mixed into a separated cation exchange resin from a chloride ion form or a sulfuric acid form. In other words, a method for regenerating a cation exchange resin of a mixed-bed desalination apparatus that can reduce the amount of anions leaked during water washing during regeneration can be used for a long period of time. It is to propose.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a method for regenerating a cation exchange resin in a mixed-bed desalination apparatus comprising a strongly acidic cation exchange resin and a strongly basic anion exchange resin, wherein a specific gravity difference is utilized for the regeneration. Separating a cation exchange resin containing an anion exchange resin, regenerating by passing an acid solution through the cation exchange resin, extruding the acid solution, and washing by passing a carbon dioxide gas absorbing water. This is a method for regenerating a cation exchange resin of a mixed bed type desalination apparatus.

FIG. 3 is a graph showing a change in the chloride ion concentration at the time of washing with water flowing through the condensate desalination apparatus. In the figure, a curve a indicates that the use period of the anion exchange resin is 1-2 months, and a curve b indicates 3
４4 months, c indicates changes in 5 to 6 months, and d indicates changes in 7 to 8 months. Since the chlorine ion concentration decreases as shown in FIG. 3 due to the flow of water after the regeneration of the ion-exchange resin, the washing water is discarded as the water-washing part where the chlorine ion concentration is higher than a predetermined value, for example, 30 ppt, and the predetermined value or less. When it becomes, the valve is switched and the process proceeds to the water sampling process.The longer the anion exchange resin is used, the less the concentration of anions such as chloride ions decreases, the greater the amount of leak increases, and the longer the water washing takes. In other words, it is necessary to wastefully discard a large amount of water as washing water.

At the time of regenerating the condensate desalination apparatus, the cation exchange resin and the anion exchange resin are separated by a specific gravity difference.
It is inevitable that a small amount of anion exchange resin is mixed in the separated cation exchange resin. When such a cation exchange resin is regenerated, the anion exchange resin remaining in the cation exchange resin comes into contact with hydrochloric acid (or sulfuric acid), which is a regenerant of the cation exchange resin, to be completely chloride ion form (or sulfuric acid form), If water washing is performed in this state, chloride ions or sulfate ions leak from the resin. And it turned out that the leak amount of these anions increases, so that the use period of an anion exchange resin becomes long.

When the strongly basic anion exchange resin mixed in the cation exchange resin comes into contact with hydrochloric acid which is a regenerant of the cation exchange resin, the following ion exchange reaction is performed. When this is washed with pure water, in the case of a new anion exchange resin, chlorine ions are partially hydrolyzed and eluted as shown in the following chemical formula 1, but the amount is small.

Embedded image RN (CH ₃ ) ₃ Cl + H ₂ O → RN (CH ₃ ) ₃ OH + HCl

However, in the case of a strongly basic anion exchange resin in which some of the exchange groups have been lowered over a long period of use, ion-exchanged chloride ions are eluted as shown in the following chemical formula 2, and the amount thereof is large. Become.

Embedded image RN (CH ₃ ) ₂ HCl + H ₂ O → RN (CH ₃ ) ₂ + HCl + H ₂ O

[0010] Therefore, it is presumed that the longer the period of use of the anion exchange resin is, the less the anion concentration in water washing after the regeneration of the ion exchange resin is reduced, and the greater the leakage amount.

In the present invention, in the regeneration of a mixed bed type desalination apparatus comprising a strongly basic anion exchange resin and a strongly acidic cation exchange resin, when regenerating a cation exchange resin containing a trace amount of anion exchange resin, carbon dioxide absorbing water is used. In the case of using an anion exchange resin that has been partially degraded by long-term use, the amount of anion leaked during washing with water after regeneration can be reduced by performing the washing.

In the regeneration method of the present invention, first, a strongly acidic cation exchange resin and a strongly basic anion exchange resin constituting a mixed bed are separated by utilizing a specific gravity difference. In this case, a small amount, for example, 0.3 to 1% of the anion exchange resin remains in the cation exchange resin. A chemical injection step in which an acid solution such as hydrochloric acid or sulfuric acid is passed through the cation exchange resin containing the anion exchange resin in the same manner as in the past, and an acid solution is extruded by passing almost the same amount of pure water as the acid solution. After performing the step, the cation exchange resin is regenerated by performing a washing step of washing by passing carbon dioxide gas-absorbed water. In this case, it is more effective to wash with pure water or heated pure water after passing the carbon dioxide gas-absorbed water.

In the present invention, the separation of the cation exchange resin and the anion exchange resin in the mixed bed type desalination apparatus is usually carried out by utilizing the difference in specific gravity by backwashing. Although good, it is preferable to minimize the amount of anion exchange resin mixed in the cation exchange resin.

In the present invention, the acid solution used as a regenerating agent for the cation exchange resin is an acid which is generally used as a regenerating agent for a strongly acidic cation exchange resin.
Sulfuric acid and the like are preferred. The concentration of the acid solution is usually 1 to 10% by weight.
It is about.

The carbon dioxide-absorbed water used for cleaning in the present invention is preferably pure water in which carbon dioxide has been absorbed, and preferably has a carbonic acid or bicarbonate ion concentration of 100 to 2000 ppm. The carbon dioxide gas-absorbed water can be used at room temperature, but it can also be used after being heated to, for example, 30 to 80 ° C, preferably 40 to 50 ° C.

Washing with carbon dioxide-absorbed water is performed by passing carbon dioxide-absorbed water through a cation exchange resin layer regenerated with an acid solution. At this time, the acid solution adhering to the resin is dissolved in the washing water and discharged.

Simultaneously, anion such as chloride ion and carbonic acid or bicarbonate ion exchange-adsorbed to a very small amount of anion exchange resin mixed in the cation exchange resin are ion-exchanged, and anion such as chloride ion is eluted with washing water. Is discharged. The amount of anion eluted by the carbon dioxide gas-absorbed water is larger for an anion exchange resin having a longer use period and a lower exchange group.

In the washing with carbon dioxide gas-absorbed water, the concentration of anions such as eluted chloride ions is set to a predetermined value, for example, 30 ppt.
It ends when: After that, washing with pure water, condensed water or heated water, the carbon dioxide-absorbed water attached to the resin is discharged, and the carbonic acid or bicarbonate ion exchanged and adsorbed on the anion exchange resin is partially eluted, Is discharged.

On the other hand, the separated anion exchange resin is regenerated by separately passing an alkaline solution. Then, the regenerated cation exchange resin and anion exchange resin are mixed to form a mixed bed.

The desalination apparatus having the mixed bed thus formed is supplied with raw water such as condensed water, and is washed with water. When a predetermined water quality is obtained, the valve is switched to the water sampling step. In the water washing step, pure water may be used, or heated pure water or raw water may be used.

In the above regeneration step, since the anions exchanged and adsorbed by the anion exchange resin mixed in the cation exchange resin are eluted and discharged by the carbon dioxide gas-absorbed water, the amount of anions leaking in the water sampling step is small.

[0022]

Embodiments of the present invention will be described below. FIG. 1 is a system diagram showing a method for regenerating a cation exchange resin of an example. In the figure, A is a mixed-bed desalination tower, B is a cation regeneration tower, C is an anion regeneration tower, and D is a resin storage tank. Reference numeral 1 denotes a cation exchange resin, which is obtained by backwashing and separating the mixed bed resin transferred from the mixed bed type desalting tower A to the cation regeneration tower B, and transferring the anion exchange resin 2 to the anion regeneration tower C. Yes, and contains a trace amount of anion exchange resin.

In this method for regenerating a cation exchange resin, first, a mixed bed resin comprising a strongly acidic cation exchange resin and a strongly basic anion exchange resin constituting a mixed bed is transferred from a mixed bed type desalting tower A to a cation regeneration tower B. The two resins are separated by utilizing the difference in specific gravity, and the upper layer of the anion exchange resin 2 is separated into an anion regeneration tower C
And the cation exchange resin 1 containing a small amount of anion exchange resin is left in the cation regeneration tower B.

Next, in the chemical pouring step, an acid solution, for example, hydrochloric acid is passed as a regenerant from the chemical pouring tube 3, and the washing waste liquid is discharged from the drain pipe 4. As a result, the cation exchange resin 1 is regenerated, and the exchange group of the anion exchange resin mixed in a trace amount is ion-exchanged to a complete chlorine ion type by chloride ions.

After regenerating the cation exchange resin 1 by passing a predetermined amount of the acid solution, the process proceeds to the extrusion step, and pure water of substantially the same amount as the acid solution is passed through the chemical injection tube 3 and The acid solution remaining in 1 is pushed out to drain pipe 4.

Next, the process proceeds to the cleaning step, in which carbon dioxide gas-absorbed water is passed through the cleaning water pipe 5 and discharged from the drain pipe 4 for cleaning. The carbon dioxide absorption water is mixed with pure water from the water supply pipe 6 to the mixing tanks 7 and 8.
The carbon dioxide gas is supplied from the carbon dioxide gas cylinder 9 through the gas pipe 10 to the mixing tank 7 while controlling the supply amount with the regulator 11, mixed in the mixing tanks 7 and 8, and absorbed by pure water to absorb the carbon dioxide gas. Is done. The prepared carbon dioxide gas-absorbed water is measured for conductivity by the conductivity meter 12, the flow rate is adjusted by the flow meter 13, and introduced into the cation regeneration tower B from the washing water pipe 5. The opening of the regulator 11 is adjusted by the signal of the conductivity meter 12 to control the amount of carbon dioxide gas to be supplied.

By passing the carbon dioxide-absorbed water through the cation regeneration tower B, the chloride ions exchanged and adsorbed by the anion exchange resin contained in the cation exchange resin 1 are eluted and discharged. After chlorine ions are eluted by passing carbon dioxide-absorbed water in this way, the supply of carbon dioxide from the carbon dioxide gas cylinder 9 is stopped, and pure water is supplied from the cleaning water pipe 5 to perform cleaning. Along with discharging the gas-absorbed water, a part of the exchange-adsorbed carbonate or bicarbonate ions is eluted and discharged.

The cation exchange resin 1 thus regenerated
Is transferred to a resin storage tank D and mixed with the anion exchange resin after regeneration to form a mixed bed. After being washed in the resin storage tank D, it is transferred to the mixed-bed type desalination tower A, and the raw water or pure water such as condensate is passed therethrough to perform water washing. At this time, the elution of anions such as chloride ions is small, water can be washed in a short time, and even when an anion exchange resin used for a long time is used, the concentration of anions such as chloride ions decreases. When the anion concentration becomes equal to or less than the predetermined value, the valve is switched and the process proceeds to the water sampling step.

FIG. 2 is a system diagram showing a method for regenerating a cation exchange resin according to another embodiment. In this embodiment, a water supply pipe 1 is placed in a dry ice melting tank 15 filled with dry ice 14.
Pure water is injected into the high-concentration carbonated water 17 from the pump 6, and the high-concentration carbonated water 17 is supplied by a liquid supply pump 18, the supply amount is adjusted by a regulator 11 and supplied to the mixing tank 7. Water is mixed into carbon dioxide-absorbed water, and supplied to the cation regeneration tower B from the washing water pipe 5 to wash the cation exchange resin 1. Others are the same as FIG.

Hereinafter, test examples of the present invention will be described. (1) Effect of promoting chloride ion elution Anion exchange resin (D
iaion PA312L A cation exchange resin containing 3 ml (trade name, manufactured by Mitsubishi Kasei Kogyo Co., Ltd.)
PK228G, manufactured by Mitsubishi Kasei Kogyo Co., Ltd., trade name) 100
0 ml, 5% hydrochloric acid 3000m
l, 4500 ml of pure water was 900
The solution was passed at a flow rate of 0 ml / hr. Thereafter, as a washing step, pure water, warm pure water (50 ° C.), carbon dioxide-absorbed water (concentration of about 80
(0 ppm) at a flow rate of 1400 ml / hr for 30 minutes, and the chloride ion concentration at each column outlet was compared. Table 1 shows the results.

[0031]

[Table 1]

As is clear from Table 1, more chlorine ions could be eluted by washing with carbon dioxide-absorbed water as compared with washing with pure water and warm pure water. Thereafter, as a washing step, pure water was passed for 30 minutes at a flow rate of 1400 ml / hr, and subjected to the next test.

(2) Influence on chlorine ion concentration at the time of washing with flowing water Each of the cation exchange resin regenerated under the above conditions and 500 ml of separately regenerated anion exchange resin are mixed and filled in a column, and the water washing step is performed. 105 liters of pure water as
Water was passed at a flow rate of er / hr. Table 2 shows the chloride ion concentration at the time of washing with passing water through each column.

[0034]

[Table 2]

Compared to those washed with pure water or warm pure water,
Those washed with carbon dioxide gas-absorbed water had a small amount of chloride ion leak, and the concentration decreased quickly.

[0036]

According to the present invention, a cation exchange resin containing a trace amount of an anion exchange resin is regenerated by passing an acid solution, and after extruding the acid solution, it is washed by passing a carbon dioxide gas-absorbed water. Therefore, even when an anion exchange resin degraded by long-term use is used, the chloride ions exchanged and adsorbed on the anion exchange resin can be eluted, whereby the leakage of anions in the washing with water after regeneration can be achieved. The amount can be reduced, so that the water washing can be completed in a short time, and the anion exchange resin can be used for a long period of time.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a method for regenerating a cation exchange resin of an example.

FIG. 2 is a system diagram showing a method for regenerating a cation exchange resin according to another example.

FIG. 3 is a graph showing a change in chlorine ion concentration at the time of flowing water washing of a condensate desalination apparatus.

[Explanation of symbols]

 Reference Signs List A Mixed-bed desalination tower B Cation regeneration tower C Anion regeneration tower D Resin tank 1 Cation exchange resin 2 Anion exchange resin 3 Chemical injection pipe 4 Drainage pipe 5 Washing water pipe 6, 16 Water supply pipe 7, 8 Mixing tank 9 Carbon dioxide gas cylinder 11 Regulator 12 Conductivity Meter 13 Flow Meter 14 Dry Ice 15 Dry Ice Melting Tank

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuhiro Oda 3-4-7 Nishi-Shinjuku, Shinjuku-ku, Tokyo Inside Kurita Kogyo Co., Ltd. (72) Inventor Takeshi Tsurumi 3-4-2 Nishishinjuku, Shinjuku-ku, Tokyo No. Kurita Kogyo Co., Ltd. (56) References JP-A-61-97039 (JP, A) JP-A-51-73749 (JP, A) JP-A-56-62546 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B01J 49/00-49/02 C02F 1/42

Claims (1)

(57) [Claims] 1. A method for regenerating a cation exchange resin in a mixed-bed desalination apparatus comprising a strongly acidic cation exchange resin and a strongly basic anion exchange resin, wherein the cation exchange resin contains a small amount of anion exchange resin by utilizing a specific gravity difference. Separating the resin, regenerating by passing an acid solution through the cation exchange resin, extruding the acid solution, and washing by passing a carbon dioxide-absorbed water through the mixed bed type desalination apparatus. A method for regenerating a cation exchange resin.