JPH0615020B2 - Hollow fiber membrane filtration device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a hollow fiber membrane used for treating radioactive waste liquid in a nuclear power plant or reprocessing plant or for condensate purification in a nuclear power plant or a thermal power plant. Regarding filtration equipment.

(Prior Art) Generally, in a nuclear power plant, suppression and removal of generation of corrosion products are performed as a radiation reduction measure. The corrosion products are removed, for example, by separating and removing the radioactive waste liquid generated in the nuclear power plant or the suspension present in the condensate of the reactor condensate system by using the hollow fiber membrane filtration device.

FIG. 6 is a sectional view showing a first conventional example of a hollow fiber membrane filtration device.

In order to filter the waste liquid (processing liquid) by the hollow fiber membrane filtering device 1, the waste liquid is supplied from the waste liquid supply pipe 3 to the filtration chamber 7 of the container body 5. The supplied waste liquid is filtered by the hollow fiber membrane of each hollow fiber membrane module 9, and is guided to the processing chamber 11 through each hollow fiber element. The treated liquid (treatment liquid) guided to the treatment chamber 11 is sent to the outside from the treatment liquid discharge pipe 13.

Since the filtration function gradually decreases as the filtration action of the hollow fiber membrane progresses, it is necessary to perform backwashing treatment regularly. During the backwashing process, a pressurized gas is supplied from the processing liquid discharge pipe 13 to the processing chamber 11 to pressurize the inside of the processing chamber 11. The pressurization causes the treatment liquid to flow back, ejects the treatment liquid from the inside to the outside of the hollow fiber, and removes the suspension adhered to the outer periphery of the hollow fiber. The removed suspension precipitates at the bottom of the filtration chamber 7. At the time of supplying the pressurized air, bubbles are ejected from the bubbling pipe 15 at the same time, and the bubbles vibrate the hollow fibers to smoothly remove suspended matter such as clad. By this backwashing action, each hollow fiber membrane module 9
The filter function of the hollow fiber membrane is restored.

During the backwash, the treatment liquid in the treatment chamber 11 flows back to the filtration chamber 7 through the hollow fiber, so that the excess treatment liquid and waste liquid in the filtration chamber 7 are discharged from the overflow pipe 17. At the same time, the air supplied from the bubbling pipe 15 into the filtration chamber 7 is also discharged to the outside via the overflow pipe 17.
After the backwashing is completed, the waste liquid in the filtration chamber 7 concentrated by the precipitation of the suspension is discharged from the concentrated waste liquid discharge pipe 19.

After that, the waste liquid is introduced again from the waste liquid supply pipe 3, the waste liquid is filled in the filtration chamber 7, and the process proceeds to the filtration process. At this time, since the hollow fibers of the hollow fiber membrane module 9 do not easily pass air, the air in the filtration chamber 7 is discharged from the overflow pipe 17 as the liquid level of the waste liquid rises. However, since the overflow pipe 17 is installed at a certain distance h from the partition plate 21 that divides the filtration chamber 7 and the processing chamber 11,
Before the waste liquid supply to the inside of the filtration chamber 7 is completed and the filtration process is started, the air remains in the upper portion of the filtration chamber 7. Therefore, in the hollow fiber membrane module 9, the residual air 23
Since there is a portion in contact with, and this contact portion does not contribute to the filtration process at all, there is a drawback that the effective membrane area of the hollow fiber membrane module 9 is reduced and the filtration efficiency is reduced. Further, since the hollow fiber membrane module 9 comes into contact with the residual air 23, there is a possibility that the hollow fiber that comes into contact with the residual air 23 may deteriorate.

Therefore, conventionally, as shown in FIG. 7, a second conventional example has been proposed in which a flow path 25 is formed in the partition plate 21 and an overflow pipe 26 is connected to the flow path 25. Further, as shown in FIG. 8, the overflow pipe 27 is bent upward in the filtration chamber 7 and the overflow pipe 2 located in the filtration chamber 7 is
There is a third conventional example in which the tip of the opening 24 of No. 7 is located above the lower end of the binding portion 28 of the hollow fiber membrane module 9. Further, as shown in FIG. 9, a weir plate 29 is installed so as to surround the opening in the filtration chamber 7 of the overflow pipe 17 in the first conventional example, and the upper end 30 of the weir plate 29 is attached to the hollow fiber membrane module 9. There is a fourth conventional example which is located at the lower end of the binding portion 28.

According to the second conventional example shown in FIG. 7, it is possible to raise the liquid level of the waste liquid in the filtration chamber 7 immediately before the start of backwashing until it comes into contact with the partition plate 21 to clean the air in the filtration chamber 7. Therefore, the hollow fibers of the hollow fiber membrane module 9 can be completely immersed in the waste liquid. Further, also in the case of the third and fourth conventional examples shown in FIGS. 8 and 9, the liquid level of the waste liquid in the filtration chamber 7 immediately before the start of the backwash is changed to the overflow pipe 27 (the eighth pipe).
Since it can be lifted up to the upper end of the opening 24 in FIG. 8 or the weir plate 29 (FIG. 9), the hollow fiber of the hollow fiber membrane module 9 can be completely immersed in the waste liquid. Therefore, in the cases of the second to fourth conventional examples, it is possible to improve the filtration efficiency of the hollow fiber membrane module 9 and prevent the deterioration of the hollow fibers. The second to fourth conventional examples are disclosed in Japanese Patent Application No. 60
-137302.

However, in the second to fourth conventional examples, there is no problem when the number of the hollow fiber membrane modules 9 is small, but when the number of the hollow fiber membrane modules 9 is large, the waste liquid and the treatment liquid at the time of the backwash are treated. In addition, in consideration of the amount of discharged air, it is necessary to increase the diameters of the overflow pipes 26, 27, 17 and increase the number thereof. However, in the case of the second conventional example shown in FIG. 7, there is a limit to the expansion of the diameters of the overflow pipe 26 and the flow path 25 due to the restriction of the thickness of the partition plate 21. Therefore, there is a drawback that a sufficiently large flow path cannot be secured, a backwash flow rate required to obtain an appropriate backwash performance cannot be obtained, and the backwash performance is deteriorated.

Further, in the case of the third and fourth conventional examples shown in FIGS. 8 and 9, the distance between the end of the opening 24 of the overflow pipe 27 or the upper end 30 of the weir plate 29 and the partition plate 21 is δ _1.
And then, when the distance between the bundling unit 28 the lower end and the partition plate 21 lower surface of the hollow fiber membrane module 9, δ _2, δ ₁ <δ ₂ of relationship. When the number of hollow fiber membrane modules 9 is large,
In response to this, for example, the overflow pipe 2 of the third conventional example
Even if the diameter of 7 is increased in an appropriate range, the peripheral length of the opening 24 does not become so long. Here, the flow passage area A ₁ of water and air at the time of backwashing is determined by the overflow pipe 27
If the inner diameter of is d, then A ₁ = πdδ ₁ . Further, the flow velocity of water and air flowing through the opening 24 of the overflow pipe 27 is V ₁ =, where Q is the required flow rate during backwashing.
It is shown by Q / A ₁ . Further, the fluid resistance is proportional to the square of the flow velocity.

Therefore, from these facts, when the distance δ ₁ is small, the flow passage area A ₁ of water and air at the time of backwash becomes insufficient, which increases the flow velocity V _{1 and} increases the fluid resistance. As a result of the increase in the fluid resistance during the backwashing, the backwashing of the hollow fiber membrane becomes insufficient, and the backwashing process does not sufficiently recover the filtration pressure. Such inconvenience is the same as in the case of the fourth conventional example.

FIG. 11 shows a quantitative determination of an aqueous solution (flow rate 40 m ³ / h, temperature 30 ° C.) in which ferric oxide and amorphous iron are mixed with the surface area of the hollow fiber membrane being 500 m ² in the third conventional example (FIG. 8). It is a test result when filtered. The horizontal axis of the figure represents the total amount of undissolved solids captured by the hollow fiber membrane in unit membrane area (g /
m ² ), and the vertical axis represents the filtration differential pressure (the pressure difference between the waste liquid supply pipe 3 and the treatment liquid discharge pipe 13). From this graph,
The filtration differential pressure cannot be sufficiently recovered even by the backwashing treatment. Particularly, the filtration differential pressure rapidly increases as the number of backwashing increases, and the backwashing performance cannot be recovered as the number of backwashing increases.

In order to prevent such a reduction in recovery of the backwash performance of the third and fourth conventional examples, it is conceivable to increase the diameters of the overflow pipes 27 and 17 of these conventional examples or increase the number thereof. However, the overflow pipes 27, 17
If the diameter of the closed container 5 is made larger than the appropriate range, the hole diameter of the penetrating portion of the closed container 5 becomes large and the strength of the closed container 5 decreases. Further, an increase in the number of overflow pipes 27 and 17 is not preferable because it leads to a complicated layout of piping connected to the closed container 5.

In addition to the above-mentioned drawbacks, in the case of the fourth conventional example, insoluble solids are deposited in the weir plate 29, and in particular, this hollow fiber membrane filtration device of the fourth conventional example was applied to a nuclear power plant. In this case, this insoluble solid content causes an increase in radiation dose,
There is also a drawback that the radiation dose of the worker during maintenance increases.

(Problems to be Solved by the Invention) As described above, in the second conventional example, the hollow fiber membrane module 9 is used.
Overflow pipe 2 even if the number of
6 and the diameter of the flow path 25 cannot be enlarged, and therefore, a sufficient flow path cannot be ensured and the cleaning performance may deteriorate. Further, in the cases of the third and fourth conventional examples, since δ ₁ <δ ₂ , there is a possibility that the flow area of water or air will be insufficient, the fluid resistance will increase, and the backwash performance will deteriorate.

Further, in the case of the fourth conventional example, the overflow pipe 17
The weir plate 29 installed so as to surround the opening of the above is actually attached to the inner wall of the closed container 5 by welding. The closed container 5 is a pressure container, and is required to undergo a welding inspection as required by law. Therefore, the management burden such as the welding inspection cost is increased, resulting in an economic loss.

The present invention has been made in view of the above conventional problems, and can secure a sufficient flow passage of a fluid at the time of backwashing, and can secure a sufficient flow passage area to improve the cleaning performance. An object of the present invention is to provide a hollow fiber membrane filtration device with improved economic value and safety.

[Structure of Invention]

(Means for Solving Problems) The present invention provides a hollow fiber membrane module vertically installed on a partition plate that divides the inside of a closed container into a filtration chamber and a processing chamber, and a hollow fiber membrane that constitutes the hollow fiber membrane module is used. In a hollow fiber membrane filtration device for filtering a liquid to be treated, an overflow pipe is attached to the closed container, the overflow pipe is formed from the filtration chamber toward the partition plate, and has a funnel shape in the filtration chamber. The peripheral length of the end portion of the formed opening is larger than the peripheral length of the sealed container penetrating portion.

(Operation) Therefore, according to the hollow fiber membrane filtration device of the present invention, the overflow pipe can be enlarged in a funnel shape so as to obtain a necessary backwashing flow rate, and a sufficient flow path can be secured, and the overflow pipe It is possible to increase the flow passage area of the fluid in the filtration chamber side opening portion and reduce the fluid resistance.
From these things, the backwash performance can be improved.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

The hollow fiber membrane filtration device 31 includes a closed container 33, and the closed container 33 is configured by covering an upper opening of a container body 35 with a lid plate 39 via a partition plate 37.

The partition plate 37 includes a filtration chamber 41 and a processing chamber 43 in the closed container 33.
Partition into and. In addition, a plurality of hollow fiber membrane modules 45 are detachably mounted on the partition plate 37, and the vertically suspended hollow fiber membrane modules 45 are pressed and fixed by a fixing plate 47. The hollow fiber membrane module 45 includes a partition plate 37.
Is protected by being surrounded by a cylindrical protection tube 49 attached to the.

The hollow fiber membrane module 45, as shown in FIG.
A large number of hollow fibers 51 are bundled to form a bundle of hollow fibers 51, the hollow child bundle is bent in a U shape, and the ends are bound by a resin binding portion 53. Fine particles in the waste liquid (liquid to be treated) are captured on the surface of the membrane of the hollow fiber 51, and
It is provided so that the filtered clear treatment liquid flows in the hollow fiber 51.

On the other hand, the waste liquid supply pipe 5 for supplying the waste liquid to the container body 35.
5 is connected, and a concentrated waste liquid discharge pipe 57 is connected to the lower end of the container body 35. Further, an overflow pipe 59 is connected to the upper portion of the container body 35 in the figure. Further, a processing liquid discharge pipe 61 for discharging the filtered processing liquid is connected to the upper end portion of the lid plate 39 of the closed container 33.

A bubbling pipe 63 is provided at the bottom of the container body 35, and a plurality of bubble holes 65 are formed in the bubbling pipe 63.
The bubbling pipe 63 is connected to the air supply pipe 67, and the air supplied from the air supply pipe 67 is ejected from the bubble holes 65 to be used for bubbling.

The overflow pipe 59 has a main function of discharging excess waste liquid and treatment liquid stored in the container body 35 during backwashing. The overflow pipe 59 is formed to be curved from the filtration chamber 41 toward the partition plate 37. Further, as shown in FIG. 3, the opening 69 of the overflow pipe 59 located inside the filtration chamber 41 is formed in a conical shape that expands upward in the figure as an example of a funnel shape. As a result, the circumferential length of the tip of the opening 69 is formed to be longer than the circumferential length of the penetrating portion of the overflow pipe 59 that penetrates the container body 35. Further, the tip of the opening 69 of the overflow pipe 59 is provided at the same horizontal position as or above the lower end of the binding portion 53 of the hollow fiber membrane module 45. That is, if the distance between the opening 69 and the lower surface of the partition plate 37 is δ _A and the distance between the lower end of the binding portion 53 and the lower surface of the partition plate 37 is δ _B , then δ _A ≦ δ _B is set.

Next, the operation of the hollow fiber membrane filtration device 31 will be described.

In this hollow fiber membrane filtering device, the filtering process is performed by supplying the waste liquid into the filtration chamber 41 from the waste liquid supply pipe 55. When the supplied waste liquid permeates the hollow fiber 51 of the hollow membrane module 45 arranged in the filtration chamber 41,
The fine particles in the waste liquid are captured by the membrane surface of the hollow fiber 51 and separated and removed.

The clear treatment liquid from which the fine particles have been removed and which has been filtered passes through the hollow fibers 51 of the hollow fiber membrane module 45 and flows into the upper treatment chamber 43. Then, the processing liquid is stored in the processing chamber 43.
Through the treatment liquid discharge pipe 61 to the outside of the reactor water supply system or the like.

With the progress of the filtration process of the waste liquid, fine particles adhere to the membrane surface of the hollow fiber 51 and block the fine permeation holes of the hollow fiber membrane, so that the filtration differential pressure gradually increases. When the filtration pressure difference rises above a certain pressure, backwashing treatment is carried out to restore the filtration function of the hollow fiber membrane.

This backwashing process is performed by supplying a pressurized gas from the processing liquid discharge pipe 61 side to pressurize the inside of the processing chamber 43. The pressurization of the processing chamber 43 causes the processing liquid to flow into the hollow fiber membrane module 4
The hollow fibers 51 of 5 flow back to wash away the fine particles adhering to the membrane surface of the hollow fibers 51. Air is supplied from the air supply pipe 67 to the bubbling pipe 63 during the backwashing process so that this backwashing action is performed more efficiently. The supplied air is ejected as bubbles from the bubble holes 65 of the bubbling pipe 63. The blown air causes the hollow fiber membrane module 33 to pulsate, and the peeling function of the fine particles adhering to the hollow fibers 51 is enhanced.

The processing liquid that has flowed back into the filtration chamber 41 from the processing chamber 43 during this backwash is discharged to the outside of the closed container 33 through the overflow pipe 59 together with the waste liquid. Further, at this time, the bubbles ejected from the bubbling pipe 63 are similarly discharged to the outside from the overflow pipe 59.

The fine particles removed from the hollow fiber membrane module 45 are
The concentrated waste liquid containing the fine particles, which is stored in the bottom of the container body 35, is discharged from the concentrated waste liquid discharge pipe 57 after the backwashing process.
Is discharged to the outside through.

According to the above-mentioned embodiment, the following effects can be obtained.

(1) Since the fluid flow rate at the time of backwashing can be sufficiently secured and the flow passage area of water and air can be increased, the backwashing performance can be improved. As an example, the hollow fiber membrane module 45
Consider the hollow fiber membrane filtration device 31 using 50 fibers. In this case, the backwashing flow rate Q required to obtain proper backwashing performance is 0.03 m ³ / S by experiment. In general, the economic flow velocity U in the pipe should be about 3-4 m / S. Therefore, the diameter of the overflow pipe 59 is Becomes That is, an overflow pipe having an inner diameter of 98 mm or more may be used. For example, in the case of the overflow pipe 59 having an inner diameter of 102.3 mm, the pipe cross-sectional area S is 8219 mm ² . In this way, the overflow pipe 59 is connected to the partition plate 37.
Rather, since it is attached to the container body 35, the diameter d of the overflow pipe 59 can be increased in a range that does not reduce the strength of the container body 35. As a result, it is possible to sufficiently secure the flow paths of the waste liquid and the processing liquid in the filtration chamber 41 which are discharged through the overflow pipe 59 during the backwash.

Further, in order to prevent the deterioration of the hollow fibers 51 of the hollow fiber membrane module 45, consider the case where δ _A = 15 mm, for example. In this case, the opening 6 of the overflow pipe 59 during backwashing
The flow path area A ₂ of 9 is represented by A ₂ = πDδ _A, where D is the inner diameter of the tip of the opening 69. At this time, the flow velocity V ₂ of water such as waste liquid flowing on the tip of the opening 69 is Indicated by. From these things, if D = 280mm, On the other hand, in the above-mentioned third conventional example (FIG. 8), δ ₁ = 15
mm and d = 102.3 mm, Becomes In the present embodiment and the third conventional example, in general,
Since the resistance of the fluid is proportional to the square of the flow velocity, That is, in this embodiment, since the flow passage area A ₂ is significantly larger than the flow passage area A ₁ of the third conventional example, the fluid resistance can be reduced to about 10 to 20% of the third conventional example. As a result, it is possible to sufficiently backwash the hollow fibers 51.

As described above, in this embodiment, it is possible to secure a sufficient flow passage at the time of backwashing and to secure a sufficiently large flow passage area.
The backwash performance can be improved. As a result, the life of the hollow fiber membrane module 45 can be extended.

FIG. 10 is a graph showing the test results of the quantitative filtration test in the hollow fiber membrane filtration device 31 of this example. In this test, as in the case of the test of the third conventional example, the hollow fiber membrane surface area of the hollow fiber membrane module 45 was set to 500 m ² , and the oxidation second
Aqueous solution of iron and amorphous iron (flow rate 40 m ³ / h, temperature 3
(0 ° C.) is quantitatively filtered. The vertical axis in the figure is the amount (G / m ² ) of the total amount of insoluble solids captured by the hollow fiber membrane per unit membrane area, and the vertical axis is the filtration differential pressure. According to this graph, the filtration differential pressure surely decreases and recovers with each backwash, and the recovery of the filtration differential pressure is remarkable even when the number of backwashing increases. Therefore, it can be seen that the backwashing performance is dramatically improved as compared with the case of the third conventional example (FIG. 11).

(2) It is possible to improve the filtration efficiency and prevent the deterioration of the hollow fiber.

That is, the liquid surface of the waste liquid in the filtration chamber 41 is located above the lower end of the binding portion 53 of the hollow fiber membrane module 45 or on the same horizontal plane. Therefore, the entire hollow fiber 51 is immersed in the liquid, and the entire hollow fiber membrane module 45 can be contributed to the filtration, so that the effective membrane area can be expanded and the filtration efficiency can be improved. . At the same time, since the upper end of the hollow fiber 51 does not come into contact with air, deterioration of the hollow fiber 51 can be prevented.

(3) As described above, the opening 6 of the overflow pipe 59
Since the circumferential length of the tip 9 is increased to increase the flow passage area during backwashing, the backwashing performance can be improved even if the diameter of the overflow pipe 59 is reduced. Therefore, the diameter of the through hole for the overflow pipe 59 of the container body 35 can be reduced, and the strength of the container body 35 can be maintained. In addition, it is not necessary to reinforce the container body 35 accordingly. further,
For the same reason, since the number of overflow pipes 59 can be reduced, the layout of the pipes connected to the container body 35 can be simplified.

(4) In this embodiment, since the weir plate 29 as in the fourth conventional example (FIG. 9) is not used, the situation where insoluble solids are deposited in the weir plate 29 does not occur. Therefore, when this embodiment is applied to a nuclear power plant, the radiation dose of the hollow fiber membrane filtration device 31 is low, and the radiation dose of the worker during maintenance can be significantly reduced.

(5) In addition, in this embodiment, since the opening 69 of the overflow pipe 59 is only conical, the center of gravity of the hollow fiber membrane filtration device 31 is low, and sufficient earthquake resistance can be secured.

FIG. 4 and FIG. 5 are perspective views showing first and second modified examples, respectively, when the opening of the overflow pipe in the hollow fiber membrane filtration device 31 is formed in a funnel shape.

In the first modification shown in FIG. 4, the opening 73 is formed in a polygonal pyramid shape which is expanded upward in the drawing.
Further, in the case of the second modification shown in FIG. 5, the opening 73 of the overflow pipe 75 is formed in a polygonal pyramid shape having an unevenness that is expanded upward in the drawing. Generally, the flow passage area at the time of backwashing in the opening of the overflow pipe increases as the end circumference of the opening increases. Therefore, in the case of these modified examples, the flow passage area of the overflow pipe opening at the time of backwashing can be further increased and the backwashing performance can be improved as compared with the case of the above-described embodiment.

〔The invention's effect〕

As described above, according to the hollow fiber membrane filtration device according to the present invention, the overflow pipe is attached to the closed container, is formed from the filtration chamber toward the partition plate, and the end portion of the opening located in the filtration chamber is further formed. Since the perimeter is formed to be larger than the perimeter of the sealed container penetrating portion, it is possible to secure a sufficient flow passage during backwashing and increase the flow passage area, and as a result, improve backwashing performance. There is an effect that can be.

Further, according to the present invention, since the opening of the overflow pipe is formed in a funnel shape and cannot be directly attached to the inner wall of the closed container, the pressure boundary does not occur, and as a result of being excluded from the welding inspection object, the welding inspection cost etc. become unnecessary, which is economical. The property is improved.

Furthermore, since the present invention does not use a weir, the situation that undissolved solids are deposited in the weir does not occur. Therefore, when the present invention is applied to a nuclear power plant, the radiation dose of the hollow fiber membrane filtration device is low, and the exposure dose of the worker during maintenance can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the hollow fiber membrane filtering device according to the present invention, FIG. 2 is a perspective view showing the hollow fiber membrane module of FIG. 1, and FIG. 3 is an overflow pipe of FIG. Partial perspective views, FIGS. 4 and 5 are perspective views showing first and second modified examples of the overflow pipe, and FIG. 6 is a sectional view showing a first conventional example of a hollow fiber membrane filtration device. Fig. 7 ~
FIG. 9 is a cross-sectional view of the main parts showing the second to fourth conventional examples of the hollow fiber membrane filtering device, FIG. 10 is a graph showing the results of the quantitative filtration test of the embodiment shown in FIG. 1, and FIG. It is a graph which shows the result of the quantitative filtration test in a 3rd prior art example. 31 ... Hollow fiber membrane filtration device, 33 ... Airtight container, 35 ...
... Container body, 37 ... Partition plate, 41 ... Filtration chamber, 43 ...
... processing chamber, 45 ... hollow fiber membrane module, 51 ... hollow fiber, 53 ... binding part, 59 ... overflow tube, 69
……Aperture.

Claims (2)

[Claims] 1. A hollow fiber in which a hollow fiber membrane module is hung vertically on a partition plate that divides the inside of a closed container into a filtration chamber and a treatment chamber, and a liquid to be treated is filtered by a hollow fiber membrane constituting the hollow fiber membrane module. In the membrane filtration device, an overflow pipe is attached to the closed container, the overflow pipe is formed from the filtration chamber toward the partition plate, and the end of the opening formed in a funnel shape in the filtration chamber. A hollow fiber membrane filtration device, characterized in that the peripheral length is formed to be larger than the peripheral length of the through portion of the closed container. 2. The hollow fiber membrane filtering device according to claim 1, wherein the tip of the opening portion of the overflow pipe located in the filtration chamber is located above the lower end of the binding portion of the hollow fiber membrane module.