JPH046423B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in backwashing and separating a mixed resin of a cation exchange resin and an anion exchange resin.

Mixed-bed ion exchange equipment that uses a mixed resin of cation exchange resin and anion exchange resin has traditionally been used in pure water production equipment that uses industrial water as raw water or condensate desalination equipment in thermal power plants, nuclear power plants, etc. It is being The mixed bed type ion exchange equipment treats the water to be treated using a mixed resin of a cation exchange resin and an anion exchange resin, so when regenerating both ion exchange resins after treatment, the mixed resin is used as a cation exchange resin. It is necessary to separate the anion exchange resin. In the conventional separation method, a method of separation using a specific gravity liquid such as a caustic soda solution is sometimes adopted, but the following backwash separation using water flow is usually performed. That is, first, backwash water is introduced from the lower part of the ion exchange tower filled with the mixed resin at a flow rate that causes the mixed resin to expand by about 100%, usually LV (linear velocity, the same applies hereinafter) 7 to 12 m/h. The mixed resin is expanded and fluidized. When the mixed resin is allowed to expand and flow in this way, a difference occurs in the settling speed of both ion exchange resins in the rising water, and the cation exchange resin with a higher specific gravity gathers at the bottom and the anion exchange resin with a lower specific gravity gathers at the top, resulting in an expanded state. Two layers of cation exchange resin and anion exchange resin are formed. After such two layers are formed, when the flow of backwash water is stopped, the expanded cation exchange resin and anion exchange resin settle in the water, and the lower layer is the cation exchange resin layer and the upper layer is the anion exchange resin layer. A separated layer can be formed.

After such backwash separation, the anion exchange resin in the upper layer may be taken out into a separate column while the two layers are still formed, and the cation exchange resin is regenerated with acid and the anion exchange resin with alkali, and then washed with water. After this, the regenerated both ion exchange resins are mixed and water is passed through again.

By the way, when separating mixed resins in mixed bed ion exchange equipment such as pure water production equipment for the electronics industry that requires high purity treated water or condensate desalination equipment for thermal power plants and nuclear power plants, the above-mentioned method is necessary. However, in the mixed bed type ion exchange equipment, the problem of insufficient increase in purity frequently occurred.As a result of various investigations into the causes of this problem, we found that the conventional backwash separation method described below It was found that incomplete separation was a major factor.

In other words, in the conventional backwash separation method, as shown in FIG.
Backwash water 3 flows in at a rate of 12 m/h, causing the mixed resin to expand and flow to level L, which is about 100% of the height of the filled resin layer, but as shown in Figure 2, most of the mixed resin is The mixed resin 1' expands and flows and separates into the expanded cation exchange resin 6' and anion exchange resin 7', but the mixed resin 1' present at the peripheral edge 5 of the support plate 4 does not expand and flow and remains as it is.
The anion exchange resin in this mixed resin 1' may amount to 3 to 5% of the total amount of anion exchange resin.

The reason why the mixed resin 1' existing on the peripheral edge 5 of the support plate 4 remains as it is is because it is difficult for water to flow into this area.

In this way, the mixed resin 1' is applied to the peripheral edge 5 of the support plate 4.
If it remains as it is, it will cause trouble in the subsequent regeneration, which will make it difficult to increase the purity of the treated water.

That is, in FIG. 3, caustic soda 9 is added to regenerate the precipitated anion exchange resin 7, and hydrochloric acid 8 is passed through the mixed resin 1' to regenerate the precipitated cation exchange resin 6. The anion exchange resin is C1 type. Note that even if both ion exchange resins are not regenerated in one tower as shown in FIG. 3, and the separated cation exchange resin 6 and anion exchange resin 7 are separated into separate towers and regenerated separately, the cation exchange resin 6 is Similarly, the mixed resin 1' is mixed into the mixed resin 1'.

In this way, the presence of C1 type anion exchange resin after regeneration will cause a poor increase in the purity of the treated water, and in particular, in the condensate desalination equipment of PWR type nuclear power plants, it is important to limit the leakage of C1 ions in the treated water. is severe, therefore C1 after regeneration
The amount of mixed anion exchange resin must be reduced as much as possible.

The present invention aims to solve the drawbacks of the conventional backwash separation method as described above, and to provide a backwash separation method that does not leave mixed resin on the peripheral edge of the support plate. Backwash water flows in from the bottom of the ion exchange tower filled with a mixed resin of anion exchange resin to form an expanded layer of cation exchange resin and anion exchange resin, and then settles to form an expanded layer of cation exchange resin and anion. In separating the exchange resin, the mixed resin present at the periphery of the support plate of the ion exchange tower is separated by creating a swirling flow along the column wall at the periphery of the support plate of the ion exchange tower when forming the expanded layer. The present invention relates to a method for backwashing and separating a mixed resin, which is characterized by separating the mixed resin from the peripheral portion.

The present invention will be explained in detail below.

The disadvantage of the conventional backwash separation method is that the mixed resin remains on the periphery of the support plate, and this is caused by the slow flow of water around the periphery of the support plate, which prevents the mixed resin in that area from expanding and flowing. It depends.

The present invention performs backwash separation by generating a swirling flow along the tower wall at the peripheral edge of the support plate, thereby fluidizing the mixed resin in that area and separating it from the peripheral edge. .

Below, the backwash separation method of the present invention will be explained step by step with reference to the drawings.

First, as shown in FIG.
Flow velocity that causes 100% expansion, usually LV7~12m/h
When the backwash water 3 is flowed in, the mixed resin 1 is expanded and fluidized, and the cation exchange resin 6' with a large specific gravity is collected at the bottom of the tower, the water is poured into the tower wall as shown in FIGS. 5 and 6. The swirling water 11 is flowed out from the provided nozzle 10, and backwash separation is performed while creating a swirling flow along the peripheral edge of the support plate 4 as shown by the arrow. Due to such a swirling flow, the mixed resin 1' present on the upper part of the support plate 4, especially at the peripheral edge of the support plate 4,
can be completely removed. In this case, the point at which the swirling water 11 flows out from the nozzle 10 is, for example, about 5 minutes after the start of the inflow of the backwash water 3, in other words, the cation exchange resin 6' and the anion exchange resin 7' are formed in an expanded state. The swirling water 11 starts flowing from the nozzle 10 after the
A flow rate equivalent to 2 to 3 m/h is sufficient. Further, it is sufficient for the inflow time of the swirling water 11 to be 3 to 5 minutes, but a longer inflow time is also acceptable.

Note that at the same time as the backwash water 3 starts flowing in, the nozzle 10
Even if more swirling water 11 flows in, the mixed resin present at the peripheral edge of the support plate 4 can be completely removed. 1
1 is more effective.

In this way, the inflow of the swirling water 11 causes the support plate 4 to
The mixed resin is separated by intervening an operation to separate the mixed resin 1' present at the peripheral edge from the peripheral edge, and the cation exchange resin 6' and anion exchange resin 7' are formed in an expanded state, and then backwashing is performed. Stop the inflow of water 3 and settle the expanded layer. The inflow time of the backwash water 3 is a sufficient time necessary to separate the cation exchange resin and anion exchange resin, and is usually around 30 minutes.

As shown in FIG. 7, the above-described process of the present invention prevents the mixed resin from remaining on the peripheral edge of the support plate 4, and can solve the drawbacks that occurred in conventional backwash separation. . Therefore, when regenerating both ion exchange resins, it is possible to significantly reduce the amount of C1 anion exchange resin produced, which effectively overcomes the disadvantage of poor purity increases that occur with conventional mixed bed ion exchange equipment. can be solved.

Examples will be described below to clarify the effects of the present invention.

Example 1 In an ion exchange tower with an inner diameter of 2000 mm and a straight section height of 6000 mm.
Filled with a mixed resin of 6280 liters of strongly acidic cation exchange resin Amberlite (registered trademark) 200C and 3140 liters of strong basic anion exchange resin Amberlite IRA-900, the following backwash separation method of the present invention and conventional backwash separation were performed. method to separate cation exchange resin and anion exchange resin.

(1) Method of the present invention Inject backwash water at a LV of 12 m/h from the bottom of the ion exchange tower, and 5 minutes after the inflow of the backwash water, a total of LV of 3 m/h is flowed through four nozzles provided on the peripheral edge of the support plate.
A swirling stream of water was injected for 3 minutes. Note that even if the inflow of swirling water is stopped, the inflow of backwash water continues, and the total inflow time of backwash water is set to 30 minutes to backwash and separate the cation exchange resin and anion exchange resin, and the inflow of backwash water is continued. I stopped it and calmed down.

(2) Conventional method Backwash water was flowed in from the lower part of the ion exchange tower at a rate of LV12 m/h for 30 minutes to backwash and separate the cation exchange resin and anion exchange resin, and then the backwash water was stopped flowing and allowed to settle.

Backwash separation was performed using the method of the present invention and the conventional method as described above, and the state of separation of the cation exchange resin and anion exchange resin was observed, and the following results were obtained.

First, in the method of the present invention, only the separated upper anion exchange resin is carefully taken out of the column, and even if only the cation exchange resin layer is subjected to the backwashing method of the present invention once again, the upper part of the cation exchange resin layer is No anion exchange resin layer was formed. In the conventional method, only the upper anion exchange resin was taken out of the column, and then the cation exchange resin layer was subjected to the backwashing method of the present invention. As a result, approximately 50 mm of the upper part of the cation exchange resin
of anion exchange resin was formed. This amount of anion exchange resin corresponds to about 5% of the total anion exchange resin. That is, it was confirmed that in the conventional backwashing method, about 5% of the total anion exchange resin remained on the peripheral edge of the support plate.

[Brief explanation of drawings]

Figures 1, 2, and 3 are explanatory diagrams showing the state of separation in the conventional backwash separation method.
The figure is an explanatory diagram of the state before backwash separation, FIG. 2 is an explanatory diagram of the state during backwash separation, and FIG. 3 is an explanatory diagram of the state after backwash separation. Moreover, FIGS. 4, 5, 6, and 7 are all explanatory diagrams showing the state of separation in the backwash separation method of the present invention, and FIGS. A state explanatory diagram during backwash separation, and FIG. 7 is a state explanatory diagram after backwash separation. 1...Mixed resin, 2...Ion exchange tower, 3...
Backwash water, 4... Support plate, 5... Periphery, 6... Cation exchange resin, 7... Anion exchange resin, 8...
...Hydrochloric acid, 9...Caustic soda, 10...Nozzle, 1
1...Swirling flowing water.

Claims (1)

[Claims] 1 By flowing backwash water from the bottom of the ion exchange tower filled with a mixed resin of cation exchange resin and anion exchange resin to form an expanded layer of cation exchange resin and anion exchange resin, and then settling it. In separating the cation exchange resin and the anion exchange resin, when the expanded layer is formed, a swirling flow is generated along the column wall at the periphery of the support plate of the ion exchange column. A method for backwashing and separating a mixed resin, characterized by separating the existing mixed resin from the peripheral portion.