JPS62269756A - Method for regenerating mixed-bed type ion-exchange tower - Google Patents

Abstract

PURPOSE:To control the Na/Cl molar ratio in the treated water to a fixed value by bringing a soln. of sodium carbonate into contact with the mixed resin after the passage of a liq., and then regenerating the resin by a conventional method. CONSTITUTION:The supply of water to be treated is stopped, when the ion exchange capacity of the resin is deteriorated in the regeneration of the mixed resin bed of the mixed bed-type ion exchange tower such as a condensate desalting plant. An aq. soln. of sodium carbonate in a storage tank 8 is introduced through a chemicals injection pipe 7 and a liq. chemicals distribution pipe 4, and brought into contact with the mixed resin bed. The waste liq. is discharged from an outlet pipe 13. Backwashing water is then introduced through the outlet pipe 13 and a water collecting pipe 6, and discharged from an water inlet pipe 2 through a water sprinkling pipe 3. Consequently, each layer of the mixed resin bed is separated and swelled, the supply of backwashing water is stopped, and the bed is separated into each layer. Caustic soda is brought into contact with an anion layer 10, hydrochloric acid is brought into contact with a cation layer 11, and then compressed air is introduced to mix both exchange resins 10 and 11 to form a mixed resin bed.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for regenerating a mixed resin bed of a hot bed type ion exchange tower. For more details.

The present invention relates to a regeneration method for maintaining a constant ratio of sodium ions to chloride ions in treated water of a mixed bed ion exchange tower in a condensate desalination equipment, etc.

[Prior art]

In recent years, secondary water quality management at thermal power plants and nuclear power plants has become increasingly strict, and as a result, the quality of treated water from mixed-bed ion exchange towers in condensate desalination equipment has been improved to minimize impurities in the treated water. In addition, it is required to control the abundance ratio of sodium ions and chlorine ions, which are the main cause of corrosion of equipment metal materials, and to ensure that free sodium ions and excessive chlorine ions are not present.

As for the control range of the abundance ratio, it is required that the molar ratio of sodium ions to chloride ions, that is, the Na/01 molar ratio, be around 0.5.

The amount of sodium ions and chloride ions present in the treated water of the mixed bed ion exchange tower is determined by the amount of sodium cation exchange resin and chloride ion anion exchange resin remaining in the mixed resin bed packed in the mixed bed ion exchange tower. is proportional to the amount of

The conventional method for regenerating the mixed resin bed of a hotbed type ion exchange tower is to introduce backwash water into the ion exchange tower after the water to be treated has passed through the tower, and to regenerate the mixed resin bed with anion exchange resin and cation. After the exchange resin is separated into two layers, the anion exchange resin is brought into contact with caustic soda and the cation exchange resin is brought into contact with hydrochloric acid to regenerate, and then both resins are washed as necessary and both resins are mixed and water is passed through. I'm offering it.

However, in the above-mentioned regeneration method, it is extremely difficult to completely separate the anion exchange resin and cation exchange resin for regeneration, and as a result, some anion exchange resins are contaminated with hydrochloric acid and converted into chloride ion form. On the other hand, the ion exchange resin is converted to sodium form by caustic soda. Furthermore, complete regeneration is not achieved with the usual industrial amount of regenerant, and a portion of the resin remains in a state in which sodium ions and chloride ions in the water to be treated are adsorbed without being regenerated. When such ion exchange resins are mixed in the mixed resin bed, sodium ions and chloride ions leak into the treated water.

However, no measures have been taken to control the Na/c'1 molar ratio of sodium ions and chloride ions in the treated water.

In other words, the amount of cations such as IJium ions and the amount of anions such as chloride ions in the water to be treated constantly fluctuate.
After passing through the water to be treated.

When regeneration is performed with a regenerant liquid that always has a constant sound.

After regeneration, the remaining amounts and ratios of the IJ type cation exchange resin and the chloride ion type anion exchange resin are not maintained at constant values.

In order to control the Na/Cl molar ratio in the treated water to a constant value, it is necessary to control the remaining ratio of the sodium-type cation exchange resin and the chloride-type anion exchange resin after regeneration.

For this purpose, when regenerating the mixed resin bed after passing the water to be treated, we measure the amount of ion exchange of each of the anion exchange resin and cation exchange resin whose ion exchange capacity has decreased, and based on the results, we A method of regenerating by determining the amount of regenerant necessary for regeneration of the regenerant, and a method of regenerating using a large excess of regenerant liquid at all times have been proposed.

The former method requires very complicated work such as analyzing the ion exchange amount of each ion exchange resin and adjusting the required amount of regenerant liquid each time, and the latter method is not economical. Neither method can be called an industrial method.

[Purpose of the invention]

The present inventor has discovered that the Na/C1
As a result of intensive study on a regeneration method that maintains the molar ratio at a constant value, when backwash water was introduced to separate the mixed resin bed,
The cation exchange resin mixed in the anion exchange resin layer and the anion exchange resin mixed in the cation exchange resin layer show almost constant values, so the Na/C of the treated water
The fluctuation in the molar ratio is not due to the influence of the mixed anion exchange resin and cation exchange resin (it is mainly due to the anion exchange resin that is difficult to regenerate, and is due to fluctuations in the amount of anions such as chlorine ions in the water to be treated and the amount of water flow). It was discovered that the ion exchange capacity of the anion exchange resin fluctuates due to fluctuations in the ion exchange capacity of the anion exchange resin, that is, the regeneration rate of the anion exchange resin fluctuates from time to time. It was also found that the rate was improved.

The present invention was made based on these findings, and when regenerating the hot bed type ion exchange tower after one liquid passage, the mixed resin was brought into contact with the IJium solution and then regenerated using the conventional regeneration method. From K to do, N in treated water
The object of the present invention is to provide an extremely simple method by which the a/C1 molar ratio can be controlled to a constant value.

[Structure of the invention]

The present invention provides a first step of bringing an aqueous sodium carbonate solution into contact with the mixed resin bed when regenerating a hot bed type ion exchange tower formed of a mixed resin bed of an anion exchange resin and a cation exchange resin; Backwash water is introduced from the bottom to form a separated expanded layer of anion exchange resin and cation exchange resin, then the introduction of backwash water is stopped and the upper layer is separated into an anion exchange resin and the lower layer is a cation exchange resin. In the third step, the stratified and separated upper layer anion exchange resin is brought into contact with caustic soda and the lower layer cation exchange resin is brought into contact with hydrochloric acid and regenerated. Pressure air is introduced from the bottom of the ion exchange tower to regenerate each layer. The gist of this invention is a method for regenerating a mixed bed type ion exchange tower, which is characterized by sequentially performing a second step of mixing ion exchange resins to form a mixed resin bed.

The present invention will be explained in detail below.

FIG. 1 is a schematic diagram of a mixed bed ion exchange column for explaining the present invention.

In Fig. 1, l is the ion exchange tower body, 2 is the raw water introduction pipe, 3 is the water sprinkler pipe, and DA is the chemical liquid dispersion pipe.

6 is an intermediate collector, 6 is a water collection pipe, 10 is an anion exchange resin layer, // is a cation exchange resin layer, and 13 is a treated water outflow pipe.

The intermediate collector S is internally provided so as to be located in the anion exchange resin layer 10 near the separation interface between the anion exchange resin layer IO and the cation exchange resin layer/l when the mixed resin bed is stratified and separated.

The recycled anion exchange resin layer 10 and cation exchange resin layer // are mixed by raw pressure air etc. introduced into the main body / through the treated water outflow pipe /J, and after forming a mixed resin bed, the treated water is passed through. served.

Well, in 1st liquid flow, the water to be treated is introduced into the main body l through the raw water introduction pipe 3 and the sprinkler pipe 3, and brought into contact with the mixed resin bed.The water to be treated that has come into contact with the mixed resin bed is ion-exchanged and becomes treated water. Water collection pipe6. The treated water flows out through the outflow pipe 13.

When the ion exchange capacity of the mixed resin bed is reduced due to the passage of the water to be treated, the passage of the water to be treated is stopped and the mixed resin bed is regenerated.

In the present invention, first, the carbonic acid solution stored in the IJum aqueous solution storage tank T is poured into a chemical injection pipe.

Introduced through chemical dispersion v4t and brought into contact with the mixed resin bed,
A first step is performed in which the waste liquid is discharged from the system through the treated water outflow pipe iJ.

The concentration of IJum aqueous solution in this process is 3 to 10%.
(weight) at a liquid passing rate of ~1r77L/hr.

In addition, the amount of IJum carbonate is the minimum amount necessary to convert the anion exchange resin and cation exchange resin, whose ion exchange ability has decreased due to the passage of the water to be treated, into the carbonate ion form and sodium ion form, respectively. do.

Normally, anion exchange resins have 200' dicarbonate (17') A, regardless of the degree of reduction in ion exchange capacity.
Approximately 0% of sodium carbonate is converted to the carbonate ion form by using an anion exchange resin of about 7, while in the case of a ion exchange resin, ioog-char f h') ') A
/, g-cation exchange resin converts about 100 liters of polygonum to the sodium form.

Therefore, in order to control the Na/Cl molar ratio in the treated water to around O, S, the mixing ratio of the mixed resin in the hot bed type ion exchange tower is often anion exchange resin: cation exchange resin = /: /. In this process, the amount of sodium carbonate is 11'-/l-mixed resin as a guide, and the amount used can be increased or decreased as appropriate, especially depending on the anion exchange resin whose properties differ greatly depending on the brand. .

Next, backwash water is introduced through the treated water outflow pipe 1J and the water collection pipe 6, and is discharged from the water sprinkler pipe 3 and the raw water introduction pipe 6, thereby separating the mixed resin bed from the anion exchange resin layer and the cation exchange resin layer into an expansion layer. After forming, a second step is performed in which the introduction of backwash water is stopped and the upper layer is separated into an anion exchange resin ff1io and the lower layer is separated into a cation exchange resin layer.

For this step, a conventional method for separating mixed resins may be adopted.

Near the separation interface between the separated anion exchange resin layer IO and the cation exchange resin layer/l, a small amount of anion exchange resin and cation exchange resin are mixed.

Next, the anion exchange resin layer 10 is stratified and separated in the second step.
In this step, the caustic soda aqueous solution stored in the caustic soda storage tank 9 is introduced into the collection pipe and the chemical liquid dispersion pipe, and the waste liquid is discharged from the intermediate collector and the recycled waste liquid discharge pipe 12 to make contact with the cation exchange resin. In the layer /l, the hydrochloric acid solution stored in the hydrochloric acid storage tank /j is connected to the drug injection pipe /lI and the water collection pipe 6.
The waste liquid is introduced through an intermediate collector.

The third step is carried out by discharging the recycled waste liquid from the discharge pipe 12 and bringing it into contact.

The amount, concentration, injection flow rate, etc. of the caustic soda and hydrochloric acid used in this step may be the same as the regeneration conditions of the conventional mixed bed ion exchange tower.

The aniocarbonate converted to carbonate ion form in the first step All of the ion-substituted resins are converted to the water-dispersed ionic form.

Since a part of the anion exchange resin in the chloride ion form is also converted into the hydroxide ion form, the remaining amount of the chloride ion form anion exchange resin can be made extremely small, and the fluctuation range of the remaining amount is also reduced.

On the other hand, all cation exchange resins in the sodium form are converted to the hydrogen ion form. Therefore, at the end of the third step, the ratio of the remaining amounts of the sodium-type cation exchange resin and the chloride-type anion exchange resin is extremely stable.

After the completion of the third step, a third step is performed, but each resin layer in the main body 1 may be cleaned as necessary prior to the third step. For example, cleaning can be done at raw water inlet pipe/3 and treated water outlet pipe/3.
This can be carried out by introducing water to be treated or desalinated water and discharging it from a recycled waste liquid discharge pipe saw. Next, separately pressurized air is introduced from the treated water outflow pipe /3 to perform a second ticking step in which the regenerated anion exchange resin layer 10 and cation exchange resin layer l/ are mixed to form a mixed resin bed.

Once the mixed resin bed is formed, it is again subjected to passage of water to be treated.

Although FIG. 1 shows an internal regeneration type mixed bed type ion exchange column for convenience of explanation, it goes without saying that the present invention can also be applied to an external regeneration type hot bed type ion exchange column.

The present invention can be carried out by simply attaching a sodium carbonate solution injection device to a conventional hotbed type ion exchange tower, and the presence of sodium type cation exchange resin and chloride type anion exchange resin, which was difficult with conventional regeneration methods. Since the quantity ratio can be kept extremely stable, the amount of N in the treated water can be kept very stable.
The a/Cl molar ratio can be kept constant.

Example Rtr the intermediate collector from the bottom.

Into the column installed at the dragon position, add 1 l each of anion exchange resin Diamond Ion (registered trademark of Mitsubishi Chemical Industries, Ltd.) BAIOA and cation exchange resin Diamond Ion (same as above) SK/B.
After filling each l.

Both resins were mixed to form a hot bed ion exchange column. In this mixed bed ion exchange column / OpI) m a8caeo
, sodium chloride io, ooot at flow rate s o m/
A regeneration test was conducted using the method of the present invention by draining the liquid for 30 minutes.

(Test 1) A 5% (weight) sodium carbonate solution was brought into contact with the above mixed bed ion exchange tower at a flow rate of 5 rrL/hr with 1 oofi-1j sodium carbonate/4/l-mixed resin.

Next, backwash water was introduced from the bottom of the column at a flow rate of 10 yl/hr for 73 minutes to form an expanded separation layer of 8A10A and SK/H, and then the introduction of backwash water was stopped and the upper layer was transferred to Bk1.
0k, the lower layer was stratified into 8/B.

The stratified and separated 8A10A was injected from the top of the column at a flow rate of arrL/hr to contact and regenerate 17% (weight 1R solution).

At the same time, 8/B has a 70% (X firefly) hydrochloric acid bath 9/!
; 09-H01/1-IK/B to flow rate II @ /
It was injected from the bottom of the column for 1 hour and brought into contact for regeneration.

All recycled waste liquids were discharged from intermediate collectors.

Next, both ion exchange resins were washed with demineralized water, and then prepressure air was injected from the bottom of the column to mix both ion exchange resins to form a mixed resin bed.

A sodium chloride solution of /Oppm a8 (3aOO3) was added to this mixed resin bed at a flow rate of jOrrL/hr.
The Na/Cl molar ratio of the treated water was measured.

(Test 2) After the mixed resin bed after test l was regenerated under the same conditions as test /, / Oppm ali CaO03 sodium chloride solution @170001 was passed through at a flow rate of y□@/hr. The Na/Cl molar ratio of the treated water was measured.

(Test 3) Testco regenerated the mixed resin bed after completion under the same conditions as in the test/, and then passed through a sodium chloride solution of lQppma day Ca C03, t,,oool at a flow rate of j Q 7Fl/hr, and the treated water at that time. The Na/01 molar ratio of was measured.

The results of Test 1, Testco, and Test 3 were as shown in Table 1.

Ratio 4+5! example A comparative test was conducted between the method of the present invention and the conventional method.

In the regeneration conditions of the mixed resin bed in the example, the step of contacting the sodium carbonate solution was deleted.

Other conditions were the same as in Example gA+, and the Na/C1 molar ratio was measured. The results were as shown in Table 1.

Table 1 Note that the leakage amount of sodium ions is 0.0 in both Examples and Comparative Examples. / ppba8 Ha.

From the results of 8g/table, it can be seen that in the examples, the leakage amount of chlorine ions is extremely stable, and treated water with a stable Na/C1 molar ratio can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a mixed bed ion exchange column for explaining one embodiment of the present invention.

Claims (1)

[Claims] (1) When regenerating a mixed bed type ion exchange tower formed by forming a mixed resin bed of an anion exchange resin and a cation exchange resin,
A first step of contacting the mixed resin bed with an aqueous sodium carbonate solution.
In the process, backwash water is introduced from the bottom of the ion exchange tower to form a separated expanded layer of anion exchange resin and cation exchange resin, and then the introduction of backwash water is stopped and the upper layer is replaced with an anion exchange resin and the lower layer is The second step is stratified separation of the cation exchange resin into cation exchange resins, the third step is to regenerate the stratified upper layer anion exchange resin by contacting it with caustic soda and the lower layer cation exchange resin with hydrochloric acid, pressurized air is added to the bottom of the ion exchange tower. A method for regenerating a mixed bed type ion exchange column, comprising sequentially performing a fourth step of introducing a mixture of ion exchange resins and mixing each ion exchange resin to form a mixed resin bed.