JPS5939186B2 - Method for removing powdered ion exchange resin deposited on granular ion exchange resin layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for efficiently removing powdered ion exchange resin deposited on a granular ion exchange resin layer in a demineralization tower of a condensate desalination apparatus using a powdered ion exchange resin as a precoating agent. Regarding.

In order to operate a nuclear power plant smoothly, it is necessary to purify the reactor cooling water, and for this purpose, (1) condensate desalination equipment and (2) reactor cleanup equipment are used. From the viewpoint of reducing the amount of water to be treated, method (1) using a condensate desalination device is the main method.

The main part of the condensate desalination equipment is a mixed-bed type desalination tower made of anion and cation exchange resins, and by passing condensate through this, ionic components and crud components (mainly insoluble iron compounds) in the condensate are removed. The condensate is purified by ion exchange and filtration with an ion exchange resin layer.

The ion components and crud components that have been supplemented in the ion exchange resin layer are removed by chemical regeneration of the ion exchange resin with acid and alkali and physical regeneration of the ion exchange resin through backwashing in the regeneration tower of the condensate desalination equipment. , separated from the ion exchange resin and discharged from the system.

Therefore, if the regeneration operation, especially the backwashing operation, is incomplete, the crud content will accumulate in the system and the radioactivity level will increase, causing a serious problem in operation.

By the way, condensate water contains suspended substances such as ionic components and crud components as impurities, and if these particle sizes are relatively large, they can be removed to some extent by the ion exchange resin in the process of removing dissolved substances from condensate water. However, extremely fine suspended substances are not removed, which causes clogging of the ion exchange resin layer and poor contact between the ion exchange resin and the liquid, deteriorating the ion exchange ability of the ion exchange resin.

For example, taking iron as an example, it is known that 2 to 3 ppb of the total iron in condensate, about 30 ppb, is dissolved iron and the rest is suspended iron.

For this reason, a method is usually used to remove suspended substances by pretreatment such as precoat filtration before performing ion exchange treatment.

Pre-coat filtration is a method in which a thin layer of pre-coat agent is created in advance on the filter screen to achieve particularly high clarity in the furnace. A configuration is adopted in which a filter forming a thin layer is placed upstream, and a desalination tower using a granular ion exchange resin is placed downstream.

In addition, as the pre-coat agent, diatomaceous earth, fiber powder,
Carbon powder, asbestos, sand, annucite, powdered ion exchanger, etc. are used, but in the case of condensate treatment, a filtration desalter is used that uses powdered ion exchange resin as a pre-coating agent to perform filtration and desalination. Methods have been developed to remove ionic components, crud fractions, and suspended solids using

However, in this method, the powdered ion exchange resin that leaks from the upstream filtration demineralizer is supplemented with the granular ion exchange resin layer in the downstream demineralizer and accumulates in layers, reducing the efficiency of operation. cause trouble.

Conventionally, backwashing for removing impurities involves gas (air or nitrogen) scrubbing at a superficial velocity of approximately 1100N (7 m) before backwashing.
However, the present inventor found that when the above impurity is a powdered ion exchange resin, the removal efficiency is improved by performing nuclear lapping at a lower flow rate, that is, superficial velocity. This invention has been achieved.

That is, an object of the present invention is to provide a method for efficiently removing powdered ion exchange resin deposited on a granular ion exchange resin layer in a demineralization tower of a condensate desalination apparatus using a powdered ion exchange resin as a precoating agent. It is to be.

The present invention has the following configuration to achieve the above object.

That is, the method for removing the powdered ion exchange resin deposited on the granular ion exchange resin layer of the present invention involves placing a filtration demineralizer using the powdered ion exchange resin as a precoating agent upstream, and using the granular ion exchange resin as the desalting agent. When removing suspended solids, ionic components, and crud from the treated water using a device located downstream of the desalination tower, the granular ion exchange resin on which the powdered ion exchange resin leaked from the filtration demineralizer is deposited is removed from the tower. It is characterized in that, before internal backwashing, backwashing is carried out after scrubbing at a superficial velocity of 30 to 8ONm37m2 hours.

As a result of various studies regarding the removal of powdered ion exchange resin deposited on the granular ion exchange resin layer, the present inventor determined that the superficial velocity of the gas (air nitrogen, etc.) before backwashing should be approximately 30
~80 N 771"/771" hours, preferably 30
It was confirmed through experiments that by setting the scrubbing temperature as low as ~5ONrrl/m hours, the objective could be efficiently achieved by backwashing with short-time scrubbing.

In this scrubbing, the superficial velocity is 3ON tr
At less than i: / m hours, the powdered ion exchange resin deposited on the ion exchange resin layer is deposited in layers and is not sufficiently loosened, causing cracks in the deposited layer and forming large lumps and settling.

On the other hand, beyond 8ONrri''7m2 hours, considerably more scrubbing time is required to obtain the same powder ion exchange resin removal efficiency.

Optimal Nuclub superficial velocity is 30-5ONm3/rr
t time, scrubbing for at least 15 minutes, followed by water backwashing, and by performing a combination of scrubbing and water backwashing 2 to 3 times, it is possible to remove 90% by weight or more of the powdered ion exchange resin, In addition, since the gas flow rate is low, the amount of gas required is reduced, and the scrubbing time can also be shortened.

Note that water backwashing has almost no effect on the removal efficiency of powdered ion exchange resin, and the backwashing water is 8 to 15 Nm/lri'
No adverse effects will occur if the superficial velocity is within the range of 10 to 20 minutes (however, if it increases too much, particulate ion exchange resin will also come out) and the backwashing time is about 10 to 20 minutes.

The present inventor changes the superficial velocity of the scrubbing,
The effect of removing the powdered ion exchange resin deposited on the granular ion exchange resin layer was investigated.The experiment will be described below with reference to the drawings, and the obtained results will be shown.

Figure 1 is a schematic diagram of the desalination equipment used in this experiment, where 1 is the raw water tank, 2 is the backwash water pump main valve, 3 is the backwash water pump, 4 is the backwash water pump outlet valve, 5 is a backwash water inlet valve, and 6 is a cylindrical desalination tower filled with granular ion exchange resin (
(hereinafter referred to as a desalination tower), 1 is a vent valve, 8 is a backwash water outlet valve, 9 is a tank for backwash water receiver, 10 is a nitrogen gas flow meter, 11
is a nitrogen gas cylinder, 12 is a nitrogen gas population valve, 13 is a nitrogen gas flow rate adjustment valve, 14 is a pressure gauge, 15 is a blow valve, 16
is a filtration demineralizer, 1γ is a powder ion exchange resin supply source valve, 1
8 is a powder ion exchange resin supply metering pump, 19 is a powder ion exchange resin tank, 20 is a stirrer, 21 is a water supply valve, 2
2 indicates the water supply return valve.

In the test, powdered ion exchange resin leaked from the filtration demineralizer 16 is deposited on the granular ion exchange resin in the demineralizer 6.

Prior to this test, the powdered ion exchange resin tank 19 was charged with powdered ion exchange resin and sodium chloride, and on the other hand,
Pure water is circulated as follows: raw water tank 1 → filtration demineralizer 16 → desalination tower 6 → raw water tank 1.

The flow rate of water at this time is superficial velocity 12 in the demineralization tower 6.
2 m/m hour (The flow meter is not shown in the figure, but the filter demineralizer 1
6).

In this way, the powdered ion exchange resin and sodium chloride are transferred by the powdered ion exchange resin supply metering pump 18, but at this time, the powdered ion exchange resin 1 (dry basis) is charged in advance to the outlet type guide of the demineralization tower 6. degree is 0.1μ5
Adjust so that it is near Zcrn (the conductivity meter is not shown but is placed immediately downstream of the demineralization tower 6).

In this test, the filtration demineralizer 16 was placed halfway,
Using powdered ion exchange resins from now on will take a long time.

In addition, the powdered ion exchange resin used in this test had a particle size of more than 60 μm and was not subject to leakage.

After the powdered ion exchange resin is deposited on the granular ion exchange resin layer in the demineralization tower 6, the vent valve γ and the vent valve 15 are opened to bring the liquid level to 5crI′L above the granular ion exchange resin layer. After that, close the blow valve 15.

The vent valve 1 is left open, the backwash water Yamaguchi valve 8, the nitrogen gas flow rate adjustment valve 13, and the nitrogen gas population valve 12 are opened, the nitrogen gas flow rate is adjusted by the nitrogen gas flow rate adjustment valve 73, and scrubbing is performed for a predetermined period of time. conduct.

And at this time, the flow rate is N rr? / Record the reading of the pressure gauge 14 and the temperature in order to convert it to 771" hours.

After that, the nitrogen gas flow rate adjustment valve 13 and the nitrogen gas population valve 12
Close.

Next, the vent valve γ and the backwash water outlet valve 8 are kept open, and the backwash water pump main valve 2, the backwash water pump outlet valve 4, and the backwash water inlet valve 5 are opened to start the backwash water pump 3. and backwash for a specified period of time.

This flow rate is adjusted by the backwash water inlet valve 5.

Thereafter, the backwash water receiver measures the weight of the powdered ion exchange resin accumulated in the tank 9.

Using the above experimental apparatus, the removal rate of the powdered ion exchange resin was measured by setting the scrubbing time to 15 minutes and varying the superficial velocity of gas scrubbing.

Note that the flow rate of water backwashing was measured using a stopwatch and a backwash water receiver as the water level in tank 9 rose.

The results obtained are shown in FIG.

That is, FIG. 2 is a graph showing the relationship between the powder ion exchange resin cumulative removal rate (weight %) (vertical axis) and the number of backwashes (horizontal axis) with respect to the total accumulated powder ion exchange resin weight,
A is the same when the superficial velocity is 30 to 5 ONm'/m, B is the same (when the superficial velocity is 6ONm/m, C is the same <8ONm3/m
In the case of ', D is the same (120Nm'/rr shows the case of 1).

Furthermore, using the same experimental apparatus as described above, the nubbing time was set to 15 minutes, and the superficial velocity of gas nubbing was varied to examine the weight percent of the powdered ion exchange resin removed.

The results obtained are shown in FIG. That is, FIG. 3 shows the weight percent (vertical axis) of the powdered ion exchange resin removed by backwashing with respect to the powdered ion exchange resin deposited on the granular ion exchange resin layer immediately before each backwash cycle and the number of backwashes ( Horizontal axis)
2. A, B, C, and D have the same meanings as in FIG. 2.

In general, the cumulative percentage removed by backwashing up to the nth time is αn (vertical axis in Figure 2), and the percentage of the amount removed relative to the total weight of the trapped powder ion exchange resin removed by the n + 1st backwashing is Let βn+ be the removal rate γn+1 at the time of the n11th backwashing.In other words, as the backwashing is repeated, the absolute amount of powdered ion exchange resin in the granular ion exchange resin layer naturally becomes Decrease.

17 Therefore, as a guideline for measuring the backwashing effect, in addition to αn, it is useful to indicate the removal rate relative to the total amount of powdered ion exchange resin at the time immediately before backwashing, in order to understand the backwashing effect at each number of times. is valid.

Incidentally, the denominator in the above equation is the percentage of the amount of powdered ion exchange resin remaining after zero backwashing to the total weight of the powdered ion exchange resin trapped.

As is clear from the graphs in Figures 2 and 3, when the superficial scrubbing velocity is 30 to 5 ONm/lri', even if the scrubbing time is reduced to a minimum of 15 minutes, the combination of scrubbing and backwashing is performed less than 3 times. The removal effect of 90% by weight or more of the powdered ion exchange resin can be obtained, and since the flow rate is low, the amount of gas required can be reduced, and the scrubbing time can also be shortened.

Note that when the superficial velocity is less than 3ON77+''/1 hour, the powdered ion exchange resin becomes lumpy and settles, reducing its effectiveness.

Also, if the backwashing time is set to 25 minutes, the superficial velocity will be 5ON m.
A similar effect was seen even when the time exceeded 100 Nrr/m'/m' and 8ONm/m', but no effect was observed even after 25 minutes of backwashing at 120 N m'/m' or more, especially at 120 Nm'/m' or more. First, the effects of the superficial velocity and time of water backwashing on the removal efficiency of the powdered ion exchange resin were not significant and were negligible.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited thereto in any way.

Example 4 units each of a granular anion exchange resin (manufactured by Mitsubishi Kasei Corporation, 5AIOB) and a granular cation exchange resin (manufactured by Mitsubishi Kasei Corporation, 5KIB) were placed in a 108 m1O column (cylindrical demineralization tower) with an inner diameter of 108 m, and powdered ions were placed on the layer. Exchange resin [anion exchange resin manufactured by Epicor Co., Ltd., Epicol powder resin PD-1]
: Cation exchange resin (manufactured by Epicor, Epicol powder resin PD-3) = 1:3 (dry weight ratio)] 5 g was deposited.

Next, by setting the scrubbing time before backwashing to 15 minutes, introducing nitrogen gas, and selecting the scrubbing time value of 45Nm'/1 o'clock, a powder ion exchange resin removal efficiency of 97% can be achieved with three backwashings. It was done.

As explained above, according to the present invention, the gas nubbing before backwashing is carried out at 30 to 8 ON m37 m2, especially at 30 to 5 O
By setting the amount of Nm to 1 m hours, the powdered ion exchange resin deposited on the granular ion exchange resin layer in the demineralization tower can be efficiently removed in a short time and with a small number of backwashing operations.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the desalination equipment used in the experiments of the present invention, Figure 2 is a graph showing the relationship between the cumulative removal rate of powder ion exchange resin and the number of backwashing with respect to the total weight of powder ion exchange resin deposited. Figure 3 is a graph showing the relationship between the weight percent of the powdered ion exchange resin deposited on the granular ion exchange resin layer removed by backwashing and the number of backwashings immediately before each backwashing cycle. . 1... Raw water tank, 2... Backwash water pump main valve, 3... Backwash water pump, 4...
Backwash water pump outlet valve, 5...Backwash water inlet valve, 6
... Desalination tower, γ ... Vent valve, 8 ...
... Backwash water outlet valve, 9 ... Backwash water receiver is tank, 10 ... Nitrogen gas flow meter, 11 ...
・Nitrogen gas cylinder, 12...Nitrogen gas inlet valve,
13... Nitrogen gas flow rate adjustment valve, 14...
・Pressure gauge, 15...Blow valve, 16...
・Furnace desalter, 11... Powder ion exchange resin supply source valve, 18... Powder ion exchange resin supply metering pump, 19... Powder ion exchange resin tank, 2
0... Stirrer, 21... Water supply valve, 22.
...Water supply return valve.

Claims (1)

[Scope of Claims] 1. Suspension in treated water is carried out by a device in which a filtration demineralizer using a powdered ion exchange resin as a precoating agent is placed upstream and a demineralization tower using a granular ion exchange resin as a desalting agent is placed downstream. material,
When removing ionic components and crud components, the granular ion exchange resin layer on which the powdered ion exchange resin leaked from the filtration demineralizer was deposited was washed at a superficial velocity of 30 to 30 before backwashing the column.
A method for removing powdered ion exchange resin deposited on a granular ion exchange resin layer, which comprises backwashing after scrubbing at 8ONm1m" hour. 2. A superficial velocity of 30 to 50 N before backwashing the column. 77
1"/m: A method for removing powdered ion exchange resin deposited on a granular ion exchange resin layer according to claim 1, wherein scrubbing is performed at a time of 1"/m.