JP2914812B2 - Slurry adjustment method for pre-coated filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precoat filter for filtering water to be treated, and more particularly to a method for preparing a slurry suitable for forming a precoat layer having a long filtration life on the precoat filter.

[0002]

2. Description of the Related Art Conventionally, a precoat filter provided in a condensate treatment system or the like for purifying water or wastewater at a nuclear power plant or a thermal power plant, for example, has a precoat filter formed on an element. It is used to remove suspended or ionic impurities by passing water through. In the removal of suspended substances in the water to be treated, the differential pressure of the precoat layer increases with time due to the trapping of impurities. When the differential pressure reaches a certain value or more, the precoat layer is removed by backwashing. Then, a new precoat material is precoated on the element.

One example of a method for pre-coating a filter element with a pre-coat material will be described in detail. In FIG. 5, reference numeral 1 denotes a pre-coat filter provided in a condensate system of a power plant. Is supplied from the outside to the inside of the element 2 having the precoat layer formed on the outer surface, and is sent downstream from the condensate outlet pipe 12.

[0004] A precoat pipe 5 is branched and connected to the condensate inlet pipe 11 so that the connection relationship between the condensate inlet pipe 11 and the precoat pipe 5 with respect to the filter 1 can be switched by a switching valve (not shown). I have. Reference numeral 6 denotes a precoat tank for adjusting the slurry, which is filled with a predetermined precoat material and is stirred by a stirrer 9.
Is provided so as to supply a pre-coating material slurry.

[0005] A precoat pipe 8 connected to the precoat tank 6 is branched and connected to the condensate outlet pipe 12. A connection valve (not shown) connects the condensate outlet pipe 12 and the precoat pipe 8 to the filter 1. The relationship can be switched.

Reference numeral 3 denotes a precoat material supply device, and 10 denotes a slurry bulk density (V / V _O × 100) for measuring the bulk density of the slurry sampled from the precoat tank 6.
%; Where V _O is the amount of the sampled liquid, and V is the amount of aggregates after standing for 15 minutes.

In such a configuration, after the used pre-coat layer is removed by back washing, first, a predetermined amount of pre-coat material and water are charged into the pre-coat tank 6 and a stirrer 9 is provided.
Is continuously performed, and after a certain period of time, the slurry in the precoat tank 6 is sampled to measure the slurry bulk density. During this time, stirring by the stirrer 9 is continued, and the slurry bulk density is maintained at a predetermined value. After confirming that it is present, supply to the element 2 of the filter 1 via the precoat pump 7. As a result, the precoat material is captured on the surface of the element 2 to form a precoat layer. Transporting water precoating material flows out from the filter outlet by passing through the element, some of which is returned at a constant flow rate again to the pre-coat tank 6 via a valve V _4, the other part is a valve V
The pre-coating is returned to the entrance of the pre-coat pump 7 at a constant flow rate via ₃ and the pre-coating process is terminated when the pre-coat material in the pre-coat tank 6 runs out. In the filter 1 after the completion of the precoating process, the valve is switched and condensed water is passed again for the condensed water treatment.

[0008] Conventionally, the above-mentioned pre-coat material generally includes:
A powdered ion exchange resin is used. The pre-coated material is adjusted so that the suspension can be removed sufficiently and necessary, and the pre-coated material has a proper bulk density adjusted so that the life is not too short due to the increase in the differential pressure of the pre-coated layer with use. It is required to pre-coat by adjusting the slurry state.

Conventional methods for adjusting the bulk density in a slurry state include a method of adding a bulk density adjusting agent, which is a solution of a polymer electrolyte, to the slurry of the powdery ion exchange resin, and a method of adjusting the particle size of the powdery ion exchange resin. There is known a method for adjusting the bulk density by using the method described above.

[0010]

In the conventional slurry preparation method as described above, it is necessary to use a pre-coating agent, for example, to use a bulk density modifier or to make the particle size of a powdery ion exchange resin within a predetermined range. There are restrictions on the composition and composition of the material slurry.

In recent years, in consideration of effective use of resources and improvement of performance, not only powdery ion-exchange resins but also ion-exchange fibers and particles and fibers having no ion-exchange ability (hereinafter, referred to as “pre-coat materials”) have been considered in consideration of effective use of resources and improvement of performance. These are collectively referred to as “pre-coat material”) or they may be used alone, and the bulk density of the pre-coat layer is more than the range adjusted using the conventional bulk density adjuster. The possibility of precoating in a large slurry bulk density state to further prolong the pressure difference over time of the filter has been studied.

In such a case, in a conventional method in which the composition of the slurry is restricted in terms of material and shape, for example, a method using a bulk density adjusting agent requires a new agent for increasing the bulk density. Must be used, but the choice is not easy. Further, in the method of adjusting the bulk density based on the particle diameter of the powdery ion-exchange resin, it is difficult to adjust the bulk density when various precoat materials are used in combination.

[0013] In the pre-coated filter used in the condensate system of a nuclear power plant, the used pre-coated material is radioactive waste, so that the pre-coated material can be used for as long as possible while maintaining the filtration performance in an appropriate range. Using it to reduce waste has a better effect.

[0014] From these facts, the present inventors have intensively studied a slurry preparation method different from the conventional one, and provided a slurry preparation method capable of prolonging the use of the precoat material as long as possible while maintaining appropriate filtration performance. The present invention has been developed for the purpose.

[0015]

The feature of the method for adjusting the slurry of the precoat type filter according to the present invention that achieves the above object is that when the element in the filter is precoated with a precoat material in a slurry state, the slurry bulk density is reduced. The precoat material composition having a composition that changes depending on the mixing time is mixed in a slurry preparation container, and after mixing is started, when the slurry bulk density reaches a predetermined value, mixing is temporarily stopped, and then necessary. According to the above, slurry sampling for measuring the slurry bulk density state is performed, and the slurry bulk density is measured and confirmed. Thereafter, in order to bring the precipitated material back into a dispersed state, mixing is resumed and pre-coating is being performed.

The reason why the above operation is employed in the present invention is that the slurry bulk density (V / V _O ) in the slurry adjustment in the case where the bulk density adjusting agent is not added in the process of repeating the above-mentioned examinations is as follows. It has the property of gradually decreasing depending on the length of stirring time. Therefore, if mixing is stopped at an appropriate point in the course of the bulk density gradually decreasing from the start of mixing, the desired bulk density state (usually, slurry bulk Density 50-7
(Preferably in the range of 5%).

In the above, the slurry to be precoated is preferably sampled and confirmed for measuring the bulk density of the slurry. However, when the composition of the precoat material to be used and the intensity of the stirring are the same, the slurry is repeatedly used. The slurry bulk density state is time-controlled based on the result of the slurry adjustment, and the pre-coating is performed without stopping the mixing when the slurry bulk density reaches a predetermined value and without performing sampling for measuring the slurry bulk density. You may.

In this case, the mixing may be temporarily stopped when the bulk density of the slurry reaches a predetermined value, and then pre-coated without performing sampling for measuring the bulk density of the slurry.

When the slurry is sampled, the service life of the filter can be estimated by measuring the bulk density of the slurry.

The precoat material used in the present invention comprises anion and cation powdery ion exchange resin, ion exchange fiber, particles and fiber having no ion exchange ability,
These can be used alone or in combination, and they can be adjusted to a slurry state by mixing them in water. However, the pre-coated material whose slurry bulk density (V / V _O ) does not depend on the length of stirring time. The composition is not subject to the present invention. Here, it is not particularly limited that the slurry bulk density depends on the length of stirring time,
In the present invention, it means that (V / V _O ) changes at least 0.05% / min or more with respect to the stirring time.

The mixing of the slurry may be stirring using a stirrer or stirring by water circulation using a pump.

According to the slurry preparation method of the present invention, the life cycle of the precoat material used in the filter can be extended while maintaining the desired appropriate filtration performance, and the resources can be effectively used. It is possible to reduce the amount of radioactive waste generated at nuclear power plants, etc.

[0023]

The present invention will be described below in more detail with reference to Examples and Comparative Examples.

Reference Example Cation exchange fiber (IONEX manufactured by Toray), powdered cation exchange resin (PCH manufactured by Graver), powdered anion exchange resin (Graver)
The slurry material composition of the present invention was prepared using PAO), and the change in bulk density (V / V _O ) during the preparation of the slurry was measured as follows.

That is, about 4 liters of water was added to a 5 liter open-top cylindrical container simulating the precoat tank 6 shown in FIG. 5, and a stirrer for maintaining a constant rotation speed (360 rpm) was started. Ion exchange fiber, powdered cation exchange resin and powdered anion exchange resin were respectively PCH: PA
O: IONEX = 55: 15: 30 (weight ratio), and the slurry was sequentially added so that the total slurry concentration became 5 wt%, and all the pre-coated materials were cylindrically operated by continuously operating the stirrer. From the time when charging into the container was completed, 500 ml of the slurry was poured from the cylindrical container every time the stirring time elapsed, as shown in FIG.
And the bulk density (V / V _O ) after standing for 15 minutes was measured. The result is shown in FIG.

Comparative Example 1 Cation exchange fiber (IONEX manufactured by Toray), powdered cation exchange resin (PCH manufactured by Graver), powdered anion exchange resin (Graver)
The slurry was adjusted using PAO (manufactured by Graver) and a slurry modifier (Sol. A manufactured by Graver), and the change in bulk density (V / V _O ) during the preparation of the slurry was measured as follows.

That is, in the same manner as in the reference example, about 4 liters of water was added to a 5-liter open-top cylindrical container simulating the precoat tank 6 in FIG.
Is started, the cation exchange fiber, the powdered cation exchange resin, and the powdered anion exchange resin are sequentially added so that the total slurry concentration becomes 5 wt%, and the stirrer is continuously operated to stir. Each time, 500 ml of the slurry was sampled from the cylindrical container into a measuring cylinder shown in FIG. 4, and the bulk density (V / V _O ) after standing for 15 minutes was measured. The result is shown in FIG.

As can be seen from the results of these reference examples and comparative example 1, in the case of the reference example using the slurry material composition which is the object of the present invention, the slurry bulk density (V / V _O ) is the value of the stirring time. Although gradually decreasing with the passage of time, in the slurry material composition using the slurry bulk density regulator of Comparative Example 1, the slurry bulk density hardly changes.

Examples Cation exchange fiber (IONEX manufactured by Toray), powdered cation exchange resin (PCH manufactured by Graver), and powdered anion exchange resin (Gr.
aver PAO) was prepared using the same stirrer as in the above reference example, and a precoat material slurry was prepared according to the composition shown in Table 2 below and the schedule shown in Table 1 below. Note that the stirring time in Table 2 indicates the stirring time from the completion of charging all the precoat materials to the start of the precoat. The bulk density of the slurry sampled after the operation of the stirrer was stopped was 70%.

This slurry was pre-coated on the element of a test condensate filter simulating a power plant, and the simulated condensate was passed through to change the filtration performance (iron concentration of outlet water) and the differential pressure (ΔP). The change was measured and the result is shown by a solid line in FIG.

[0031]

[Table 1]

[0032]

[Table 2]

Comparative Example 2 For comparison, a pre-coated material having the same composition as in the above example was continuously stirred during the measurement of the bulk density to prepare a pre-coated material slurry as shown in the schedule of Table 1. This slurry was precoated on the element of a test condensate filter simulating a power plant in the same manner as in the example, and the simulated condensate was passed through to change the filtration performance (iron concentration of outlet water) and the differential pressure (ΔP). Was measured and the result is shown by a broken line in FIG.

As can be seen from the results, the filter of the above embodiment can maintain the predetermined filtration performance and achieve a significantly longer operation due to the increase in the differential pressure (ΔP) of the filter as compared with Comparative Example 2. Was confirmed.

[0035]

According to the conventional method for adjusting the bulk density of a slurry, the use of ion-exchange fibers is restricted because the use of a bulk density modifier and the shape of the powder ion-exchange resin to be used are limited by the slurry composition itself. It is difficult to extend the life cycle of the pre-coated material while keeping the filtration performance in an appropriate state by using fibers or the like having no ion exchange capacity. According to the above, using a pre-coating material composition whose slurry bulk density depends on the stirring time length, and pre-coating the slurry in the desired slurry bulk density state by the mixing time length, the design of the filter and It is possible to obtain a slurry in accordance with a desired bulk density state determined for each device according to the type and the like, and it has a filtering performance in an appropriate range which has been considered difficult in the past. Long precoat layer lifecycle, there is an effect that can be formed on the filter.

Further, according to the present invention, the composition of the precoat material is not restricted in terms of its shape and properties in order to obtain the desired bulk density. There is an effect that it can be used.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a stirring time and a bulk density of a precoat material composition in which a slurry bulk density state changes depending on a mixing time,

FIG. 2 is a diagram showing a relationship between a stirring time and a bulk density of a precoat material composition to which a bulk density modifier is added,

FIG. 3 is a diagram showing a change in filtration performance and a rise in differential pressure of a filter precoated with a precoated material slurry of Example and Comparative Example 2,

FIG. 4 is a diagram showing a method for measuring a bulk density of a slurry.

FIG. 5 is a diagram showing an example of a configuration outline of a filter to which the present invention is applied;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Filter, 2 ... Element, 3 ... Precoat material supply apparatus, 6 ... Precoat tank, 9 ...
Stirrer, 10 ... bulk density measuring device.

Claims (4)

(57) [Claims] When pre-coating a pre-coat material in a slurry state on an element in a filter, a pre-coat material composition having a composition in which a slurry bulk density state changes depending on a mixing time is mixed in a slurry preparation container. And a method of preparing a slurry for a precoat-type filter, wherein the mixing is stopped when the bulk density of the slurry reaches a predetermined value after the start of mixing, and thereafter the mixing is restarted to perform precoating. 2. The method according to claim 1, wherein the slurry is sampled for measuring the bulk density of the slurry after the mixing is stopped. 3. A precoating material composition having a composition in which the bulk density of the slurry changes depending on the mixing time is mixed in a slurry preparation container when the element in the filter is precoated with the precoating material in a slurry state. And a method of preparing a slurry for a precoat type filter, wherein precoating is performed without stopping mixing when the slurry bulk density reaches a predetermined value after the start of mixing. 4. The method for preparing a slurry for a pre-coated filter according to claim 3, wherein a part of the slurry at the time of pre-coating is sampled for measuring a slurry bulk density.