JPH0741147B2 - Hollow fiber membrane filtration device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a filter device using a hollow fiber membrane module as a filter material, and more particularly to a hollow filter capable of effectively backwashing the hollow fiber membrane module. A membrane filter device.

(Prior Art) Generally, in a nuclear power plant, as a radiation reduction measure, the generation of corrosion products is suppressed and the corrosion products are removed. For example, a filtering device is used for separating and removing radioactive waste liquid generated in a nuclear power plant or a suspension present in the condensate of a reactor condensate feedwater system. As the filtering device, a conventional method using a precoat filter such as a powder ion exchange resin, or a method using a flat membrane type filter such as a filter paper or a filter cloth membrane filter, or a sintered metal or a ceramic is used. There is a method of using a hollow tube type filter such as.

However, in the filtration method using the powder ion exchange resin, a large amount of resin waste is generated, and in the case of using the flat membrane type filter or the hollow tube type filter, the circulation flow rate becomes large and the configuration of the filtering device becomes complicated. In addition, there was a problem that the equipment cost became huge. Further, there is a drawback that secondary waste is generated along with the filtration process and the filtration efficiency is low.

Hollow fiber membranes have become widespread as a solution to the drawbacks of conventional filter media. Generally, a hollow fiber membrane is a hollow fiber membrane having an outer diameter of 0.3 to 3 mm and a large number of fine permeation holes,
Since it has a large filtration area per unit volume and excellent pressure resistance, it is widely used in the fields of electronic industry, medicine, and wastewater treatment as a filtration material for ultrafiltration and reverse osmosis filtration.

Therefore, a conventional filtration device using a hollow fiber membrane will be described with reference to FIG.

The closed container 1 is divided into a filter chamber 3 and a processing liquid chamber 4 by a tube plate 2. A plurality of hollow fiber membrane modules 5 are vertically installed in the filtration chamber 3 in multiple stages. Each hollow fiber membrane 6 is fixed to the tube plate 2 via a module fixing portion 7, and the tube plate 2 is sandwiched by outer peripheral flanges 8 and 9 attached to the edges of the body 1A and lid plate 1B of the closed container 1. It is fixed to the closed container 1. Generally, the hollow fiber membrane module 5 has a module structure in which a large number of fibrous hollow fiber membranes are bundled in a straight line or U-shape, and an end portion is fixed with resin or the like, and a portion fixed with resin or the like is fixed to the module. It is a department. The third
In the conventional hollow fiber membrane filtration device shown in the figure, hollow fiber membrane modules 5 in which the hollow fiber membranes 6 are linearly bundled and whose ends are fixed are provided in series in three stages, and the module fixing portions 7 are connected by a connecting tool. An example is shown in which the modules are connected and attached as an integral hollow fiber membrane module structure.

The stock solution is introduced into the filtration chamber 3 through the stock solution inlet nozzle 10, and when passing through each hollow fiber membrane 6, foreign matter such as clad is separated and removed, and filtered. The filtered treatment liquid passes through the hollow portion of the hollow fiber membrane 6 and flows into the water collecting pipe 11 provided at the center of the bundle of each hollow fiber membrane module 5, and then flows into the treatment liquid chamber 4 via the tube plate 2. To do. Then, it is transferred to the outside of the system through the processing liquid outlet nozzle 12.

The filtration device increases the permeation pressure loss after filtering a predetermined amount of the stock solution or due to clogging of the hollow fiber membrane 6 that is the filtering material, so that the pressure difference between the stock solution inlet side and the process solution outlet side of the filter device becomes a predetermined value. When the value is reached, a backwash operation is required to remove the clad and the like adhering to the surface of the hollow fiber membrane 6.

In the conventional backwashing operation, the stock solution is first filled in the filtration chamber 3 as backwashing water, and pressurized air is blown from the treatment solution outlet side nozzle 12 in this state to make the pressures before and after the hollow fiber membrane 6 uniform. At the same time when the clad is peeled off, pressurized air is also sent to the air blow-out pipe 13 provided at the bottom of the filtration chamber 3 to generate air bubbles from the small holes formed in the lower portion of the air blow-out pipe 13 to make the air bubbles hollow. By impinging on the surface of the fiber membrane 6 and vibrating it (hereinafter referred to as bubbling), foreign substances such as clogging components and clad adhering to the hollow fiber membrane 6 are removed. The backwash water remaining in the filtration chamber 3 after bubbling for a certain period of time is
It is discharged from the backwash water outlet nozzle 14.

(Problems to be Solved by the Invention) In the conventional filtration device having the above-described configuration, even if a normal backwashing operation is performed, a considerable amount of foreign matter such as a clogging component or a clad on the surface of a part of the hollow fiber membrane 6 However, there was a problem that it was difficult to perform a perfect backwash operation.

That is, when the hollow fiber membrane module structure is taken out of the filtration chamber 3 after the backwashing and the distribution of the clad and the like remaining on the surface of the hollow fiber membrane 6 is verified, the module is fixed as illustrated by the broken line in FIG. The clad 15 tended to remain in the certain regions above and below the portion 7 without being removed. The cause is considered as follows. That is, the hollow fiber membrane module structure is housed in the protective tube 16 that is hung vertically from the tube sheet 2, the gap between the module fixing portion 7 and the protective tube 16 is narrow, and the hollow fiber membrane is provided in the module fixing portion 7. Since the membranes 6 are densely packed, the flow of bubbles for backwashing is restricted in the upper and lower regions of the module fixing portion 7, so that the clad and the like remain without being removed.

When the clad remains on the surface of the hollow fiber membrane 6 in this way, the effective filtration area is reduced and the filtration function of the entire apparatus is deteriorated. Further, there is a problem that the clad 15 having a high concentration of radioactivity is accumulated in the device and deteriorates the operating environment.

On the other hand, when the backwashing efficiency is lowered, the backwashing operation needs to be repeated at a considerable time and frequency, and the impact of the backwashing operation causes the hollow fiber membrane module 5 to be significantly worn out, which shortens the life of the filter medium. To do. Therefore, there is a problem that the hollow fiber membrane module 5 needs to be frequently replaced, the operating cost is increased, and a long-term continuous operation cannot be performed.

The present invention has been devised to solve the above problems and adds a backwashing mechanism capable of effectively backwashing a hollow fiber membrane module used as a filter medium to prolong the life of the hollow fiber membrane module. In addition, an object of the invention is to provide a hollow fiber membrane filtration device capable of continuous operation for a long period of time.

[Structure of Invention]

(Means for Solving the Problems) In the hollow fiber membrane filtration device of the present invention, the inside of the closed container is divided into a filtration chamber and a treatment liquid chamber by a tube plate, and the hollow fiber membrane module structure is formed from the tube plate into the filtration chamber. With the body suspended,
A liquid level detection equipment for detecting the water level of the backwash water set in the range from the upper end to the lower end of the hollow fiber membrane module structure was provided, and the predetermined water level was set based on the reading of the liquid level detection equipment. An air blow-out pipe for supplying backwash air bubbles into the backwash water is arranged at the bottom of the filtration chamber.

(Operation) The operation of the hollow fiber membrane filtering device having the above-mentioned configuration is transferred to the backwashing step after the filtration step is continued for a predetermined period. In the backwashing process, in addition to the conventional backwashing operation, the water level of backwashing water is set in the region where the cladding of the hollow fiber membrane is significantly attached, and bubbles for backwashing work from the bottom of the filtration chamber. repeat. The backwash water level is set according to the indication of the attached liquid level detection equipment. For example, the backwash water levels are set above and below the module fixing part according to the readings of the liquid level gauge that also shows the position of the module fixing part 7 on the scale, which is the region where the clad adhesion remains significantly. Backwash.

According to this apparatus, in addition to the conventional operation of uniformly backwashing the entire filtration chamber, the area where the clad or the like remains can be backwashed intensively, so that the backwashing effect is excellent. In addition, the backwash water level setting work can be easily realized by the liquid level detection equipment additionally provided.

(Example) Hereinafter, one example of the hollow fiber membrane filtering apparatus according to the present invention will be described with reference to the accompanying drawings. The same elements and parts as those of the conventional example are designated by the same reference numerals, and the description thereof will be omitted.

In FIGS. 1 and 2, reference numeral 20 is a liquid surface for detecting the water level of the backwash water set in the range from the upper end to the lower end of the hollow fiber membrane module structure vertically installed in the filtration chamber 3. It is a liquid level gauge as a detection facility. This liquid level meter 20 is used in the filtration chamber 3
The main valve 23 is connected so that the upper liquid level gauge seat 21 led from the end face of the tube sheet 2 and the lower liquid level gauge seat 22 led from the filtration chamber 3 below the lower end of the hollow fiber membrane module 5 are connected to each other. Mounted through. Therefore, the liquid level gauge 20 accurately displays the position of the backwash water level at any position along the entire length of the hollow fiber membrane module structure. An air blow-out pipe 13 for supplying bubbles into the backwash water is arranged at the bottom of the filtration chamber 3.

In the filtration process of the hollow fiber membrane filtration device configured as described above, the same operation as that of the conventional device is performed. That is, the stock solution press-fitted from the stock solution inlet nozzle 10 into the filtration chamber 3 becomes a processing solution after being filtered by the hollow fiber membrane 6 and flows into the processing solution chamber 4, and the processing solution passes through the processing solution outlet nozzle 12. Transferred to the outside.

After continuing this filtration step for a predetermined period, or when the pressure difference between the raw solution inlet side and the treatment solution outlet side reaches a constant value, the backwash step is started. As shown in FIG. 1, the backwash operation is as follows.
Pressurized air is supplied from the treatment liquid outlet nozzle 12 in a state where the stock solution is filled in the filtration chamber 3 as backwash water, the pressures before and after each hollow fiber membrane 6 are made uniform, and the clads adhered are separated and the air inlet is provided. The pressurized air is also supplied to the nozzle 17, and the filtration chamber 3
Bubbles for backwashing are generated by generating bubbles for backwashing from the small holes formed in the lower surface of the air blowing pipe 13 arranged at the bottom,
The deposits on the surface of the hollow fiber membrane 6 are removed. The above-mentioned preliminary backwashing operation is the same as in the conventional apparatus.

Next, in the filtration device of the present invention, as shown in FIG.
Bubbling is performed again with a part of the backwash water that has been stretched out, and the water level being lowered to a predetermined position. that time,
The water level in the filtration chamber 3 is set in a region where a large amount of deposits remain without being removed by the preliminary backwashing operation. The water level is detected and set according to the reading of a liquid level gauge 20 as an attached liquid level detection facility. At the time of this backwashing operation, bubbling from the air blowing pipe 13 causes a strong rippled impact on the water surface of the backwash water and an impact caused by the rupture of bubbles to cause a large swing of the hollow fiber membrane 6 near the water surface. The adhered matter remaining on that portion is positively peeled off and separated and removed.

The above operation over the entire length of the hollow fiber membrane module structure,
Especially the module fixing part 7 where the degree of clad adhesion is remarkable
By sequentially setting the backwash water levels in the upper and lower regions and repeating bubbling in the same manner, the whole hollow fiber membrane module structure is uniformly and efficiently backwashed and regenerated.

In addition, when the number of backwashing increases and the hollow fiber membrane module 5 may be exposed on the surface of the backwashing water for a long time, the hollow fiber membrane 6 is dried by appropriately filling the stock solution in the filtration chamber 3. Prevent deterioration.

In this embodiment, in the backwashing step, the water level in the filtration chamber can be arbitrarily set to carry out backwashing. Therefore, by appropriately setting the backwash water surface in the region where the hollow fiber membrane is clogged and the clad is significantly attached, the ripples on this water surface and the shock due to bubbling are synergistically caused to vibrate the hollow fiber membrane greatly, Intensive and effective backwashing is possible. For example, the module fixing part 7
Even in the upper and lower regions of the hollow fiber membranes 6 where the hollow fiber membranes 6 are densely packed, ripples and impacts caused by bubbles are spread, and effective backwashing can be performed.

Further, since the liquid level gauge 20 as the liquid level detecting equipment has a detection range of at least the entire length of the hollow fiber membrane module structure, the backwash water can be easily set at any position.

In addition, as the liquid level detecting equipment, a gauge type level gauge is exemplified in the embodiment, but other types can be adopted. That is, although not shown, a transparent glass tubular liquid column meter may be attached to the nozzle led out from the bottom of the filtration chamber 3 via the main valve. As another type, the body 1A of the filtration container body 1
Alternatively, a required number of transparent reinforced plastic viewing windows may be fitted to detect the backwash water level. In this case, the layout, diameter, etc. of the viewing window are designed within a range that does not impair the pressure resistance of the pressure vessel of the filtration vessel body.

〔The invention's effect〕

As described above, according to the hollow fiber membrane filtration device of the present invention,
In the backwash process, the backwash water level can be set arbitrarily within the entire range from the upper end to the lower end of the hollow fiber membrane module structure, and a partial backwash operation is also possible, so that the entire hollow fiber membrane module can be made uniform. Can be backwashed efficiently. Therefore, the service life of the hollow fiber membrane itself is extended, running costs are reduced, and continuous operation for a long period of time becomes possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a hollow fiber membrane filtration apparatus which is an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a state in which the backwash water level is lowered from the state of FIG. 1, and FIG. FIG. 4 is a sectional view showing a conventional hollow fiber membrane filtering device, and FIG. 4 is a sectional view showing unit elements of a hollow fiber membrane module structure after backwashing. 1 ... Airtight container, 1A ... Body, 1B ... Lid plate, 2 ... Tube plate, 3 ... Filtration chamber, 4 ... Treatment liquid chamber, 5 ... Hollow fiber membrane module, 6 ... Hollow fiber membrane , 7 ... Module fixing part,
8,9 ...... Outer peripheral flange, 10 ...... Undiluted solution inlet nozzle, 11 ......
Water collecting pipe, 12 …… Processing liquid outlet nozzle, 13 …… Air blowing pipe,
14 …… Backwash water outlet nozzle, 15 …… Cladding, 16 …… Protective cylinder, 17 …… Air inlet nozzle, 18 …… Vent.

Claims (2)

[Claims] 1. A hollow fiber membrane filtration apparatus in which a closed vessel is divided into a filtration chamber and a treatment liquid chamber by a tube plate, and a hollow fiber membrane module structure is vertically provided from the tube sheet into the filtration chamber. Backwash water with liquid level detection equipment that detects the water level of backwash water set in the range from the upper end to the lower end of the membrane module structure and set to a predetermined water level based on the reading of the above liquid level detection equipment A hollow fiber membrane filtration device, characterized in that an air blow-out tube for supplying air bubbles for backwashing is arranged at the bottom of the filtration chamber. 2. The liquid level detection equipment comprises an upper liquid level gauge seat communicating with the filtration chamber and led out from the end face of the tube plate, and a lower liquid level gauge seat led from the filtration chamber below the lower end of the hollow fiber membrane module. The hollow fiber membrane filtration device according to claim 1, further comprising a liquid level gauge connected thereto.