JPS6233550A - Separation of ion exchange resin for mixed bed type desalting device - Google Patents

Abstract

PURPOSE:To thoroughly separate three layers by adding a special operation in the stage of separating the layers of a mixed bed type desalting device where inert resins exist mixedly to the three layers by upward water flow. CONSTITUTION:This invention relates to the sepn. of the mixed ion exchange resin layers of the mixed bed type desalting device, in which backwashing water is first introduced into the device from a pipe 5 in the lower part of the mixed resin layers so as to fluidize the layers. The layers are settled after the water is filled up to the level between a chemical feed pipe 3 and a diffusion pipe 2. Compressed air is introduced from the pipe 3 into the device to oscillate the floating inert resins together with the backwashing water and to get rid of the foam sticking thereto. The inert resins are settled and in succession of, the backwashing water is introduced through the pipe 5 to thoroughly develop the mixed resin layers while the waste backwashing water is discharged from the pipe 2. The respective layers are then settled to be stratified and separated to an anion exchange resin layer 6, inert resin layer 7 and cation exchange resin layer 8 from above. The layer sepn. is thoroughly executed in the above-mentioned manner.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for separating a mixed ion exchange resin layer in a hotbed type desalination device, and particularly relates to a method for separating a mixed ion exchange resin layer of an anion exchange resin, a cation exchange resin, and both exchange resins. The present invention relates to a method for separating ion-exchange resins in a mixed bed desalination apparatus comprising a mixed resin layer of inert resins having an intermediate specific gravity.

[Conventional technology]

A method of producing desalinated water using a hot bed type desalination device comprising a mixed resin layer of an anion exchange resin and a cation exchange resin is widely used. When regenerating a hotbed type desalination equipment that produces desalinated water and whose functionality has deteriorated, the mixed resin layer is separated into negative and positive ion exchange resin layers by an upward water flow introduced from the bottom of the mixed resin layer. The exchange resin layer is developed and separated so that the lower part becomes a cation exchange resin layer, and then, after stratification separation, each of the stratified and separated ion exchange resin layers is regenerated with a regenerating agent. Mixed-bed desalination equipment, which is used in condensate treatment in thermal nuclear power plants and in ultrapure water production processes, requires particularly high-purity desalinated water.
During regeneration, the anion exchange resin layer is completely separated into an anion exchange resin layer at the top and a cation exchange resin layer at the bottom, and the separated anion exchange resin layer is exposed to an alkaline aqueous solution, while the cation exchange resin layer is exposed to only an acid aqueous solution. It is necessary to bring it into contact and regenerate it.

In other words, if the separation of the mixed resin layer is incomplete, the cation exchange resin that came into contact with the caustic soda solution becomes a sodium-loaded type, and the anion exchange resin that came into contact with a hydrochloric acid solution becomes a chlorine-loaded type. If the water is brought into the equipment), IJium and chloride ions will leak, making it impossible to obtain highly pure desalinated water.

Therefore, a method of regenerating the anion exchange resin layer and the cation exchange resin layer in a completely separated state was proposed in Tokkosho, 30-
No. 96'1 discloses that a mixed bed of anion exchange resin and cation exchange resin is further mixed with an inert substance which has a specific gravity between that of anion exchange resin and cation exchange resin and is chemically and physically stable. Desalting is performed by forming a mixed resin layer, and during regeneration, this mixed resin layer is divided into three layers, an anion exchange resin layer, an inert material layer, and a cation exchange resin layer, in order from the top using an upward water flow. A method has been proposed in which each ion exchange resin layer is regenerated by a conventional method after stratified separation. This method is
Since the positive ion exchange resin layer is completely isolated by an inert material layer, it can be regenerated without being contaminated by other regenerants, and highly pure demineralized water can be obtained with relatively simple operations, making it easier than conventional methods. It was attracting attention. In recent years, it has been adapted as an inert substance. With the development of inert resins such as polystyrene and acrylic, mixed-bed desalination equipment that uses this method is attracting attention in fields that require highly purified desalinated water, such as condensate treatment and ultrapure water production processes. has been done.

However, the mixed bed desalination equipment using this inert resin has the disadvantage that when used for a long period of time, the quality of desalinated water sometimes deteriorates and the water quality is unstable.

[Problem that the invention seeks to solve]

According to the results of studies conducted by the present inventors, this is due to the fact that the inert resin is somewhat lacking in hydrophilicity. The air bubbles may adhere to a part of the inert resin, and the inert resin with air bubbles may be mixed in the anion exchange resin layer, or may migrate through the anion exchange resin layer and be transferred to the upper part of the anion exchange resin layer. This was due to the destabilization of the layer height of the inert resin layer due to floating.

The present invention aims to eliminate the drawbacks of the above-mentioned known techniques and to obtain highly purified demineralized water by more completely separating the mixed resin layer in a mixed bed desalting device.

[Failure to solve the problem]

The present invention can be used to separate a mixed resin layer containing inert resin in a mixed bed desalting equipment into three layers, an anion exchange resin layer, an inert resin layer, and a cation exchange resin layer, using an upward water flow. By adding special operations to the method, it is attempted to completely separate the three layers.

That is, the gist of the present invention is to combine a mixed resin layer consisting of an anion exchange resin, a cation exchange resin, and an inert resin having a specific gravity between the two exchange resins into an anion exchange resin layer, an inert resin layer, and a cation exchange resin layer. When separating the resin layer into three layers, water is passed in an upward flow from the bottom of the mixed resin layer, and while the mixed resin layer is being fluidized and developed, the position of the drug injection pipe provided above the mixed resin layer is adjusted. The first step is to fill water up to the top of the tube, the second step is to stop the water flow and settle the mixed resin layer, and the second step is to shake and settle the inert resin floating near the top of the drug injection pipe. 3rd step, the fourth step is to pass water through the mixed resin layer in an upward flow from the bottom to develop and separate it into three layers in the order of an anion exchange resin layer, an inert resin layer and a cation exchange resin layer from above.
A hotbed characterized by sequentially carrying out each step of step S, in which the upward flow of water is stopped, the anion exchange resin layer, the inert resin layer, and the cation exchange resin layer are settled and stratified into three layers. It is in the ion exchange resin separation method of the type desalination equipment.

Hereinafter, the present invention will be explained in comparison with the conventional method based on FIG. FIG. 1 shows a schematic vertical cross-sectional view of an example of a mixed-bed desalination ion exchange apparatus for carrying out the method of the present invention. An anion exchange resin layer 6, an inert resin layer 7, and a cation exchange resin layer g are formed in the ion exchange column 1, and the upper surface of the filled resin layer is located approximately at the center of the ion exchange column 1, K. . Here, the inert resin is one that is chemically and physically processable. In the liquid passing step, the water to be treated is passed through the mixed resin layer in which these layers are mixed to perform desalination.

Therefore, in the flow process for producing desalted water, the water to be treated is introduced from the pipe through the valve 10/ and the dispersion pipe into the ion exchange tower/. The water to be treated is ion-exchanged by the mixed resin layer, and is taken out of the ion exchange tower/outside as demineralized water from the liquid collecting pipe 3 at the bottom via the valve 106 and the pipe 4'.

The flow process ends when the purity of the desalinated water decreases and water cannot be sampled at a predetermined value, or when a predetermined amount of desalinated water has been sampled, the flow of the water to be treated is stopped and completed.

Next, a step of separating the mixed resin layer is carried out to regenerate the negative and positive ion exchange resins whose ion exchange function has deteriorated, but a scrubbing step is usually carried out as a pre-step to this separation step.

This step is carried out to peel off and remove suspended matter that is carried into the ion exchange tower/inside the water to be treated and adheres to the surface layer of the mixed resin layer. It is the valve 103 from the drug injection pipe 3.
After draining the water remaining in the ion exchange tower/ from the pipe //, the pipe 13 and the valve 10! This is carried out by injecting pressurized air through the liquid collecting pipe S to radically fluidize the mixed resin layer.

When this scrubbing step is completed, in the conventional method, backwash water is immediately introduced from pipe 3, valve ios, and collection pipe S, and the separated suspended water is introduced into the backwash water from dispersion pipe 7, valve 102, and pipe IO. The mixed resin layer, which is fluidized and expanded at the same time as it is discharged outside the tower, is layered from above with an anion exchange resin layer 6 and an inert resin layer 7.
, a separation step is performed in which the cation exchange resin layer g is developed and separated. However, at that time, the air used in the scrubbing process forms fine bubbles and adheres to the surface of the inert resin.
Therefore, the buoyancy of the inert resin increases, and some of the inert resin migrates into the anion exchange resin layer that is being fluidized and even into the upper space of the anion exchange resin layer.

As a result, when the introduction of backwash water in the next step was stopped and the flowing resin layer was allowed to settle down, and when stratified and separated into three resin layers, part of the inert resin was transferred to the anion exchange resin layer. This results in the inert resin layer being mixed in the anion exchange resin layer or being stacked on top of the anion exchange resin layer, resulting in unstable layer height of the inert resin layer, which has the disadvantage that complete separation cannot be performed.

Therefore, in the method of the present invention, after the scrubbing process, as a first step, backwash water is introduced from the collection pipe S through pipe /3 and valve ios at a flow rate such that the mixed resin layer flows, and the water level of the backwash water is The upper part of the filled resin layer (for example, 30-1,0 from the filled resin layer)
Perform an operation to fill the tube with water until it is between the drug injection tube 3 and the dispersion tube installed at a position above 1.5 cm. The water level of the backwash water is usually approximately S~/! above the position of the drug injection pipe J. ;Make it look like a nail. This first step is performed in order to discharge the air remaining in the mixed resin layer to the outside of the ion exchange tower.

Subsequently, a second step is performed for about 3 to 10 minutes in which the valve ios is closed to stop the introduction of backwash water and the fluidized mixed resin layer is calmed down. During this process, the inert resin with air bubbles attached to it is brought to the surface near the water level of the backwash water held in the ion exchange tower l. The third step of removing attached air bubbles and settling the inert resin is carried out for about 70 minutes. This third
In the process, if there is a small amount of floating inert resin due to its nature, water may be introduced from a dispersion tube to cause the resin to oscillate and settle due to its impact.

Next, backwash water is introduced from the collection pipe S through pipe 3 and valve 10S, and the mixed resin layer is sufficiently fluidized while discharging the backwash wastewater from the dispersion pipe 1 through valve 102 and pipe 10. A fourth step is performed in which the anion exchange resin layer 6, the inert resin layer 7, and the cation exchange resin layer g are developed and separated in this order from the top. In carrying out this ninth step, all the inert resin is removed between the anion exchange resin layer 6 and the cation exchange resin layer g, since the air bubbles attached to the inert resin in the third step have been completely expelled. is held in a suspended position. The flow rate of backwash water introduction in this process is / 0 ~ / ! ; 771/hr, / 0-
．． Each resin layer is completely developed and separated by carrying out the process for about 20 minutes.

Next, the introduction of backwash water from the liquid collecting pipe S is stopped, and each developed and separated resin layer is allowed to settle down, and the anion exchange resin layer 6, the inert resin layer 7, and the cation exchange resin layer g are formed in order from the top. An S-th step of stratified separation is performed. By carrying out this Sth step for 5 to 70 minutes, the stratification separation into each resin layer is completed.

By sequentially performing the above operations from the first step to the fifth step, each resin layer is completely stratified and separated, and an alkaline aqueous solution is injected into the separated anion exchange resin layer B through the dispersion pipe, and the cation exchange An aqueous mineral acid solution is injected into the resin layer g from the liquid collecting pipe S, and the recycled waste liquid is discharged through the recycled waste liquid discharge pipe 7, the valve 1olI,
After being discharged through pipe 2 and regenerated, it is washed with water and a mixed resin layer is again formed, after which it is subjected to a liquid passage step.

In this way, according to the method of the present invention, by separating the mixed resin layer of the mixed bed desalination equipment, a constant layer height is always maintained between the inert resin layer and the cation exchange resin layer.
Therefore, both the negative and positive ion exchange resin layers are regenerated without being contaminated by other regenerants during the regeneration process, so that highly purified demineralized water can be stably supplied.

The method of the present invention is applied to the case of separating the mixed resin layer of a mixed bed type desalination equipment that desalinates with a mixed resin layer of both anion and cation exchange resins and an inert resin. In a mixed bed desalination equipment that desalinates with a mixed resin layer of exchange resin, it can also be used to separate the mixed resin layer formed by adding an inert resin that was kept outside the ion exchange tower during the separation process. can.

〔Example〕

Example/ In a mixed bed desalination equipment as shown in Fig. 1, the inner diameter is 5θ.
9001 strong acidic cation exchange resin Diaion (registered trademark of Mitsubishi Chemical Industries, Ltd.) PK2 KoffL, Hiro, 3i011 strong basic anion exchange resin Diamond FA, ? / 2
and 2001 inert resin Diaion PE320, and injected desalinated water from the water collection pipe at the bottom of the ion exchange tower until the water level reached the vicinity of the drug injection pipe, then pressurized air was introduced and mixed. After forming the resin layer, the mixed resin layer was separated by the method of the present invention. At this time, a considerable amount of inert resin was floating above the mixed resin layer.

9. Pour desalinated water from the water collection pipe at the bottom of the ion exchange tower. /71ph
While introducing at r for S minutes and fluidizing the mixed resin layer,
After filling with water to about 1 ocrrrt above the position of the drug injection tube, the introduction of demineralized water was stopped, and the fluidized mixed resin layer was
Let it settle for a minute. When the amount of floating inert resin started to increase slightly, pressurized air was added from the drug injection tube to 1INr.
The demineralized water in the tower was injected for 7 minutes at rj/miR, and the floating inert resin was sedimented.

Next, pour desalinated water into the water collecting pipe at the bottom of the ion exchange column in step 9. /
After the introduction of demineralized water for 1S minutes with an upward flow of m/hr to develop and separate three layers: a strong basic anion exchange resin layer, an inert resin layer, and a strong salt anion exchange resin layer, demineralized water is introduced. After stopping, the mixture was allowed to settle for S minutes and stratified and separated.

After regenerating the stratified and separated strong basic anion exchange resin layer and strong acid cation exchange resin layer by a conventional method, washing with water and forming a mixed resin layer, demineralized water with an electrical conductivity of SμS/Bon was passed through. The leakage of Na ions and Cl ions was measured. In addition, the amount of regenerant used is 2009-NaOH/l-2009-NaOH/l-
resin, 5% HCII solution is for strongly acidic cation exchange resins.

1-HQI/l-resin. The results are shown in FIG. The curve shown by the solid line in the figure is the result in the example.

Comparative Example / After filling the same amount of ion exchange resin and inert resin of the same brand as Example / into the hotbed desalination equipment used in Example /, and forming a mixed resin layer by the same operation as Example /. This mixed resin layer was separated by conventional methods. In other words, desalinated water is collected from the water collecting pipe at the bottom of the ion exchange tower at a rate of 9,/711/h.
After introducing it for 1S minutes with an upward flow of r and developing and separating it into three layers,
The introduction of demineralized water was stopped and the resin layer was allowed to settle for S minutes. The inert resin layer at that time was thinner than that of Example. After settling, the mixture was regenerated and washed under the same conditions as in Example, and a mixed resin layer was formed again. Demineralized water with an electrical conductivity of SμS/an was passed through it, and the leakage of Na ions and Cl ions was measured.

The results are shown in Figure Ω. The curve shown by the broken line in the figure is the result in the comparative example.

As seen in FIG. 1, if regeneration is performed after separation by the method of the present invention, highly purified demineralized water can be obtained with a smaller leakage amount of both Cl ions and Na ions than in the conventional method.

〔Effect of the invention〕

According to the method of the present invention, the mixed resin layer in the mixed bed desalination apparatus can be more completely separated, and highly purified desalinated water can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view of an example of a mixed bed desalination apparatus for carrying out the method of the present invention, showing a state in which the mixed resin layer is separated. In the figure / is an ion exchange tower, λ is a dispersion tube, 3 is a drug injection tube,
9 is a recycled waste liquid discharge pipe, S is a liquid collection pipe, 6 is an anion exchange resin layer, 7 is an inert resin layer, g is a cation exchange resin layer, 9
, io, ii, /2.13 and /q are tubes, 10ISlO
Yu, 10.3, /θII, 10! and lθ6 indicates a valve. Figure Ω is a diagram showing the water flow results in Examples/Comparative Examples/, in which the vertical axis shows the amount of CI ions and the amount of Na ions, and the horizontal axis shows the water flow time. In addition, in the figure, the solid line shows the method of the present invention, and the broken line shows the conventional method.

Claims (1)

[Claims] (1) A mixed resin layer consisting of an anion exchange resin, a cation exchange resin, and an inert resin having a specific gravity between the two exchange resins is formed into three layers: an anion exchange resin layer, an inert resin layer, and a cation exchange resin layer. In order to separate the mixed resin layer, water is passed in an upward flow from the bottom of the mixed resin layer, and while the mixed resin layer is being fluidized and expanded, water is filled to a level above the position of the drug injection pipe provided above the mixed resin layer. The first step is to stop the flow of water to settle the mixed resin layer, the third step is to shake and settle the inert resin floating above the position of the drug injection tube, and the mixing step is performed. The fourth step is to pass water in an upward flow from the bottom of the resin layer and develop and separate it into three layers in the order of anion exchange resin layer, inert resin layer, and cation exchange resin layer from above, and stop the upward flow of water. The fifth step is to settle the anion exchange resin layer, the inert resin layer and the cation exchange resin layer and separate them into three layers.
An ion exchange resin separation method for a mixed bed desalination apparatus, characterized in that each step of the process is carried out sequentially.