JP3543389B2 - Separation and regeneration method of ion exchange resin - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method for separating and regenerating an ion-exchange resin, and more particularly to a method for regenerating a deionized water desalination apparatus (condemi) to improve the regenerated state of the ion-exchange resin that affects the quality of treated water.
[0002]
[Prior art]
Conventionally, in a condensate desalination apparatus (condemi), a desalination tower and a regeneration tower are completely separated in order to prevent an acid or an alkali which is a regenerant of an ion exchange resin from being mixed into the condensate water. Is provided. When the ion exchange capacity of the ion exchange resin in the desalination tower reaches saturation and regeneration becomes necessary, the desalination tower is disconnected from the main system, and the ion exchange resin in the tower is separated by pressurized water and pressurized air. Transfer to regeneration tower for regeneration.
[0003]
Incidentally, as the ion exchange desalination apparatus, a mixed bed type ion exchange desalination apparatus in which a cation exchange resin and an anion exchange resin are mixed and used for desalination is preferable in view of the quality of treated water to be obtained. A mixed-bed desalination tower is also used in.
[0004]
On the other hand, in the power plant, efforts are being made to maintain the water quality of the feedwater at a higher level in order to prevent corrosion of the material in the system due to impurities in the condensate and to prevent turbine scale, etc. It is desired that the water quality be even higher.
[0005]
The treatment water quality of the condemi is generally determined by the state of regeneration of the ion exchange resin packed in the desalination tower. The amount of anion exchange resin in the separated cation exchange resin, in order to more reliably separate the resin and the cation exchange resin, and to eliminate the problem of incomplete separation of the cation / anion exchange resin called "reverse regeneration", In addition, it is necessary to reduce the amount of the cation exchange resin in the separated anion exchange resin as much as possible.
[0006]
That is, the cation exchange resin is used in the H form, and the regeneration is performed by passing an acid solution. On the other hand, the anion exchange resin is used in the OH form, and its regeneration is performed by passing an alkaline solution.
[0007]
Therefore, the regeneration of the ion-exchange resin in the mixed-bed desalting tower is performed by separating the cation-exchange resin and the anion-exchange resin, but if this separation is not completely performed, impurities will be generated in the next desalination step. Leakage, causing various harms. For example, when a cation exchange resin is mixed in an anion exchange resin, the cation exchange resin becomes Na form by regeneration with alkali (mainly sodium hydroxide is used), and when desalination is performed using this resin, sodium ions are formed. Released, causing scale disturbance in boiler tubes and turbines. Further, when an anion exchange resin is mixed in the cation exchange resin, the anion exchange resin becomes SO ₄ or Cl by regeneration with an acid (mainly sulfuric acid or hydrochloric acid is used). Released, causing scale disturbance.
[0008]
However, conventionally, both ion-exchange resins are separated by a specific gravity difference by spreading the resin layer by flowing upward water to a mixed-bed type ion-exchange bed. It was not possible to avoid mixing of ion exchange resins.
[0009]
Conventionally, in order to improve the separability of this ion exchange resin, the mixed bed is treated with upward flowing water, the upper layer made of an anion exchange resin, the lower layer made of a cation exchange resin, and the cation exchange resin and cation between the upper and lower layers. The resin in the intermediate layer in which the anion exchange resin and the cation exchange resin are separated (the resin near the interface between the anion exchange resin and the cation exchange resin; hereinafter, “intermediate resin”) ) May not be involved in reproduction.
[0010]
For example, in Japanese Patent Application Laid-Open No. 54-41277, the intermediate resin is not immediately regenerated, but is mixed with the regenerated resin to be separated at the next separation and regeneration of the mixed bed. There has been proposed a method of arranging a resin to be separated and performing separation and regeneration.
[0011]
[Problems to be solved by the invention]
Thus, by removing the intermediate resin from the regeneration system, it has become possible to industrially regenerate the cation / anion exchange resin in two parts, but even if such a method is adopted, the cation exchange resin can be regenerated. The residual anion exchange resin could not be completely eliminated.
[0012]
The present invention solves the above-mentioned conventional problems, and in regenerating an ion exchange resin of a mixed-bed ion exchange device such as a desalination tower of condemi, improves the separability between an anion exchange resin and a cation exchange resin. Another object of the present invention is to provide a method for performing an effective reproduction process.
[0013]
[Means for Solving the Problems]
The method for separating and regenerating an ion-exchange resin according to the present invention is a method for separating and regenerating a regenerated resin to be separated, comprising a mixed bed of an anion exchange resin and a cation exchange resin. Only the upper layer, an intermediate layer in which an anion exchange resin and a cation exchange resin are mixed, and a separation step of separating only the cation exchange resin into a lower layer, separating each layer from other layers, and separating the upper layer and the lower layer from each other. A regenerating step of regenerating with a regenerating agent, wherein the separation step and the regenerating step are performed after the intermediate layer is disposed on the resin to be separated and regenerated at the next separation and regenerating.
[0014]
[Action]
In the method disclosed in JP-A-54-41277, when the intermediate resin generated in the previous separation / regeneration step is mixed with the resin to be separated / regenerated in the desalting tower for the next separation / regeneration, the following process is performed. The procedure is as follows.
[0015]
{Circle around (1)} After the intermediate resin generated in the previous separation and regeneration step is transferred to a cation regeneration tower (cation exchange resin regeneration tower), the separated and regenerated resin in the desalting tower is transferred to the cation regeneration tower.
[0016]
{Circle around (2)} The inside of the cation regeneration tower is backwashed to separate into an upper layer of the anion exchange resin, an intermediate layer of the intermediate resin and a lower layer of the cation exchange resin.
[0017]
{Circle around (3)} The upper layer anion exchange resin is transferred to an anion regeneration tower (anion exchange resin regeneration tower) for regeneration.
[0018]
{Circle around (4)} The inside of the cation regeneration tower is backwashed again to separate again, and the upper intermediate resin is transferred to the intermediate resin tank.
[0019]
(5) Regenerate the cation exchange resin in the cation regeneration tower.
[0020]
That is, conventionally, as described above, in order to reduce the time required for regeneration, and from the viewpoint that the ion exchange resin can be effectively separated by backwashing in the cation regeneration tower, as described above, the intermediate resin during the previous separation and regeneration was used. Is transferred to the cation regeneration tower, and then the next regenerated resin to be separated is transferred to the cation regeneration tower.
[0021]
Therefore, conventionally, the regenerated resin to be separated in the desalting tower is transferred to the cation regenerating tower and placed on the previous intermediate resin.
[0022]
By the way, the intermediate resin is a state in which the cation exchange resin and the anion exchange resin are mixed, and therefore, in a state where the regenerated resin to be separated and the intermediate resin are transferred to the cation regeneration tower, the lower part in the cation regeneration tower is Means that a considerable amount of anion exchange resin is present in the intermediate resin.
[0023]
On the other hand, in general, since the water collecting strainers of the cation regeneration tower are provided at a pitch of about 20 cm, in the backwashing separation step after receiving the resin, a sufficient backwashing water flow particularly between the lower water collecting strainers. As a result, the resin present here cannot be sufficiently fluidized.
[0024]
As a result, when the regenerated resin to be separated is disposed on the intermediate resin as in the related art, the anion exchange resin transferred as the intermediate resin does not flow to the upper part of the cation regeneration tower due to the backwash water flow, and the cation is regenerated even after the backwash. A phenomenon that remains at the bottom of the tower occurs. In the usual case, conventionally, an anion exchange resin of about 0.8 to 2% of the total amount of the anion exchange resin is mixed into the cation exchange resin in the cation regeneration tower for reverse regeneration.
[0025]
On the other hand, in the method of the present invention, since the previous intermediate resin is disposed on the resin to be separated and separated, the anion exchange resin in the intermediate resin does not remain at the lower part of the regeneration tower as in the related art. At the time of washing, the anion exchange resin flows only at the upper part of the regeneration tower. For this reason, the backwashing can effectively separate the anion exchange resin into an upper layer, an intermediate layer between the anion exchange resin and the cation exchange resin, and a lower layer of the cation exchange resin. Contamination and reverse regeneration of the contaminated anion exchange resin are prevented.
[0026]
According to such a method of the present invention, the amount of reverse-regenerated resin can be significantly reduced from 0.8 to 2% of the related art to about 0.3 to 0.6%.
[0027]
【Example】
Hereinafter, the present invention will be described in detail with reference to the drawings.
[0028]
FIG. 1 is a system diagram of a condemi illustrating an embodiment of a method for separating and regenerating an ion exchange resin according to the present invention. In the figure, 1 is a desalination tower, and 2 is a cation regeneration tower (cation exchange resin regeneration tower). 3, an anion regeneration tower (anion exchange resin regeneration tower); 4, an intermediate resin storage tank;
[0029]
In the apparatus of FIG. 1, in regenerating the ion exchange resin in the desalination tower 1, first, the ion exchange resin in the desalination tower 1 is transferred to the cation regeneration tower 2 via the pipes 11 and 12. Water is flowed upward to the cation regeneration tower 2 to backwash. That is, water is introduced from the pipe 13 through the pipes 14 and 15 into the cation regeneration tower 2 and backwashed. The backwash drainage is discharged from the pipe 17. Reference numeral 19 denotes an intermediate discharge pipe.
[0030]
By the backwashing, the anion exchange resin and the cation exchange resin are developed, and the ion exchange resin in the cation regeneration tower 2 is separated into an upper layer of the anion exchange resin, an intermediate layer of the intermediate resin and a lower layer of the cation exchange resin due to a difference in specific gravity. Is done.
[0031]
Of the three separated layers, the upper anion exchange resin is transferred to the anion regeneration tower 3 via the pipes 20 and 21. That is, water is sent to the cation regeneration tower 2 via the pipes 13, 14 and 15, and the anion exchange resin flows out of the pipes 20 and 21. This regenerated water is discharged from the pipe 22.
[0032]
Next, the same backwashing operation as described above is repeated again to separate again into an upper layer of the intermediate resin (an intermediate layer at the time of the first backwashing) and a lower layer of the cation exchange resin. Then, the upper intermediate resin is transferred from the pipes 20 and 23 to the intermediate resin storage tank 4.
[0033]
After the anion exchange resin and the intermediate resin have been transferred, the inside of the cation regeneration tower 2 is substantially composed of only the cation exchange resin. The regenerated cation exchange resin is transferred from the pipe 18 to a cation exchange resin storage tank or the desalination tower 1 (not shown).
[0034]
On the other hand, the anion exchange resin in the anion regeneration tower 3 is regenerated by supplying an alkaline solution from the pipe 24 according to a conventional method. The regenerated anion exchange resin is transferred to an anion exchange resin storage tank (not shown) or the desalination tower 1 via a pipe 22.
[0035]
In the next desalination treatment, the anion exchange resin and the cation exchange resin obtained in the previous regeneration and, if necessary, a new anion exchange resin and a cation exchange resin are filled in the desalination tower 1, and the demineralization tower 1 is filled in a usual manner. Desalination is performed. When the ion exchange capacity reaches saturation due to the desalting treatment and the regeneration treatment is required, the ion exchange resin in the desalting tower 1 is regenerated.
[0036]
First, the ion exchange resin in the desalting tower 1 is transferred to the cation regeneration tower 2, and then the intermediate resin obtained by the previous separation and regeneration in the intermediate resin storage tank 4 is passed through the pipes 25 and 12 to the cation regeneration tower 2. Transfer into 2. As a result, the intermediate resin is disposed in the cation regeneration tower 2 on the separation regeneration resin transferred from the desalting tower 1.
[0037]
Thereafter, in the same manner as in the previous separation and regeneration operation, separation by backwashing, transfer of anion exchange resin, reseparation by backwashing, and transfer of intermediate resin were performed, and the anion exchange resin and cations transferred to the anion regeneration tower were transferred. Regeneration of the cation exchange resin remaining in the regeneration tower is performed, and the separation regeneration is completed.
[0038]
In the present invention, there is no particular limitation on the column in which the ion exchange resin is separated and regenerated, and the separation may be performed in a desalination column, or a separate separation and regeneration column may be provided. Further, the separation may be performed in an anion regeneration tower.
[0039]
When separation is performed in a desalination tower, the upper layer is transferred to an anion regeneration tower, the intermediate layer is transferred to an intermediate resin storage tank, and the lower layer is left as it is in a desalination tower or transferred to a cation regeneration tower. When a separation and regeneration tower is separately provided for separation, the upper layer is transferred to an anion regeneration tower, the intermediate layer is transferred to an intermediate resin storage tank, and the lower layer is left as it is. In either case, the intermediate resin layer obtained by the previous separation and regeneration may be made to wait until the next separation and regeneration, and the resin may be transferred so as to be arranged on the next resin to be separated and reproduced. To take out each separated layer from the tower, the upper layer and the intermediate layer can be taken out from the top of the tower in an upward flow, and the lower layer can be taken out from the lower part of the tower by a downflow. The resin layer is developed in countercurrent, the upward flow rate is adjusted so that the interface of each layer is at the position of the resin take-out tube, and in this state, when the valve provided on the resin take-out tube is opened, only the resin on the interface is removed. Can be taken out.
[0040]
In the present invention, regeneration of the cation exchange resin and the anion exchange resin can be carried out according to a conventional method, wherein the anion exchange resin is an alkali solution such as a 2 to 20% by weight sodium hydroxide solution, and the cation exchange resin is The solution is passed through a 2 to 10% by weight acid solution such as sulfuric acid or hydrochloric acid, and then extruded and washed with water.
[0041]
Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples.
[0042]
Example 1
According to the method shown in FIG. 1, the mixed-bed ion exchange resin in the desalination tower was separated and regenerated.
[0043]
Each of the regeneration towers 2 and 3 is a columnar tower having a tower diameter of 2.3 mφ and a height of 5.7 m. The desalination tower 1 is a columnar tower having a tower diameter of 3.2 mφ and a height of 2.9 m. The intermediate resin storage tank 4 is a columnar tower having a tower diameter of 1.0 mφ and a height of 2.0 m.
[0044]
The demineralizer was charged with a cation exchange resin (Mitsubishi Chemical Co. Diaion PK228G) 6.8m ³ and an anion exchange resin (Mitsubishi Chemical Co. Diaion PA312L) 3.7m ^3.
[0045]
First, the entire amount of the ion exchange resin in the desalting tower 1 is introduced into the cation regeneration tower 2, and upward flowing water is supplied to the intermediate layer where the anion exchange resin and the cation exchange resin are mixed. The layer was separated into a lower layer composed of a cation exchange resin. Then, the upper layer of the anion was transferred to the anion regeneration tower 3, the intermediate layer was transferred to the intermediate resin storage tank 4, the anion exchange resin was regenerated in the anion regeneration tower 3, and the cation exchange resin was regenerated in the cation regeneration tower 2. . Ion exchange resins were transferred to the intermediate resin reservoir 4, the anion exchange resin 0.6 m ^3, was cation-exchange resin 0.2 m ^3. The method and conditions for this separation / regeneration are the same as the second separation / reproduction conditions described later.
[0046]
The cation exchange resin and the anion exchange resin regenerated in each of the regeneration towers 2 and 3 are returned to the desalination tower 1, respectively, and a new cation exchange resin and an anion exchange resin are replenished to perform desalination treatment. The second separation and regeneration was performed by the operation described above.
[0047]
First, the entire amount of the ion exchange resin in the desalting tower 1 is transferred to the cation regeneration tower 2, and then the entire amount of the ion exchange resin in the intermediate layer separated during the previous separation and regeneration from the intermediate resin storage tank 4 is transferred to the cation regeneration tower 2. Was transferred onto the resin to be separated and regenerated.
[0048]
Thereafter, first, backwash water is passed through the cation regeneration tower 2 at LV = 12 m / h for 30 minutes, and an intermediate layer in which an anion exchange resin and a cation exchange resin are mixed, and an anion exchange resin and a cation exchange resin are mixed. Separated into layers. Subsequently, an upward flow of LV = 12 m / h was passed through for 30 minutes, and the anion exchange resin in the upper layer was transferred to the anion regeneration tower 3. The backwash water is again passed through the cation regeneration tower 2 at LV = 20 m / h for 30 minutes to perform re-separation, and the upper layer (intermediate layer) in which the anion exchange resin and the cation exchange resin are mixed, and the lower layer of the cation exchange resin And the upper layer (intermediate layer) in which an anion exchange resin and a cation exchange resin are mixed is transferred to the intermediate resin storage tank 4 by passing an upward flow of LV = 20 m / h for 20 minutes. did.
[0049]
After this transfer, the amount of the anion exchange resin remaining in the cation exchange resin after being mixed with the cation exchange resin in the cation regeneration tower 2 was about 22.3 liters, which was significantly 0.60% of the total anion exchange resin amount. Thus, it was confirmed that the cation exchange resin and the anion exchange resin could be effectively separated.
[0050]
Comparative Example 1
In Example 1, in the second separation / regeneration, first, the intermediate resin in the intermediate resin storage tank 4 separated in the first separation / regeneration is transferred to the cation regeneration tower 2 and then removed on the intermediate resin. The same operation is performed except that the regenerated resin to be separated in the salt tower 1 is disposed, separation by backwashing, transfer of the upper anion exchange resin, reseparation by backwash, and transfer of the intermediate resin of the upper layer (intermediate layer) are performed. And separated and regenerated.
[0051]
As a result, the amount of anion exchange resin remaining in the cation regeneration tower 2 after being mixed with the cation exchange resin was about 32.4 liters, which was 0.87% of the total anion exchange resin amount, as compared with Example 1. And the residual ratio was high.
[0052]
【The invention's effect】
As described in detail above, according to the method for separating and regenerating an ion-exchange resin of the present invention, in regenerating the ion-exchange resin of a mixed-bed ion-exchange apparatus such as a desalination tower of Condemi, an anion-exchange resin and a cation-exchange resin are used. And the effective reproduction process can be performed.
[Brief description of the drawings]
FIG. 1 is a system diagram of a condemi illustrating an embodiment of a method for separating and regenerating an ion exchange resin according to the present invention.
[Explanation of symbols]
1 desalination tower 2 cation regeneration tower 3 anion regeneration tower 4 intermediate resin storage tank

Claims (1)

A method for separating and regenerating a regenerated resin to be separated, comprising a mixed bed of an anion exchange resin and a cation exchange resin,
A separation step of separating the mixed bed into an upper layer of only anion exchange resin by upward flowing water, an intermediate layer in which anion exchange resin and cation exchange resin are mixed, and a lower layer of only cation exchange resin;
A regeneration step of isolating each layer from other layers and regenerating the upper layer and the lower layer with a regenerating agent, respectively.
A method for separating and regenerating an ion-exchange resin, wherein the separation step and the regenerating step are performed after disposing the intermediate layer above the resin to be separated and regenerated at the time of the next separation and regeneration.

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