JP3136715B2 - Membrane separation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane separation apparatus, and more particularly to a membrane separation apparatus capable of continuing operation with low operation power without lowering a filtration speed.

[0002]

2. Description of the Related Art In recent years, with the development of membrane separation technology, a membrane filtration method using a membrane separation apparatus has been adopted in various fields.

[0003] Among the membrane filtration methods, membrane filtration in the fields of turbidity removal, sterilization and the like has been widely used in the past.
With the development of flow type membrane modules, the applicable concentration range has been widened. When this cross-flow type membrane module is used, membrane filtration can be continued without reducing the filtration rate to a filtration rate that cannot be practically used, even if the raw water has turbidity fluctuations. . For this reason, UF (ultrafiltration) and MF (microfiltration) membranes are used instead of flocculation, sedimentation and filtration in pretreatment for RO (reverse osmosis) membrane separation of river water, industrial water and clean water. Filtration has made it possible to simplify the pretreatment process.

However, in such a field, when performing membrane filtration using a cross-flow type membrane module, how to reduce the fresh water production cost (operating power) per filtered water is an issue for practical use. I have.

[0005]

SUMMARY OF THE INVENTION As described above,
If a flow-type membrane module is used, membrane filtration can be continued without lowering the filtration speed, but it is necessary to circulate a larger amount of raw water than the amount to be filtered to give a constant flow rate to the membrane surface. . For this reason, the fresh water cost (operating power) per filtered water must be high.

In order to reduce the driving power without lowering the filtration speed, the raw water flow path may be narrowed and the circulation flow rate of the raw water may be reduced. However, if the raw water flow path is narrowed, the raw water flow path due to SS in the raw water may be reduced. It cannot be put to practical use because blockage occurs.

On the other hand, according to dead end filtration, only the raw water to be filtered needs to be supplied by a pump, and the operating power can be reduced. However, cake-like products accumulate on the membrane surface over time. Therefore, the filtration speed is reduced, and a large membrane area is required to obtain a fixed amount of filtered water. In addition, in the whole volume filtration, a backwash operation is periodically performed to remove a cake-like product accumulated on the membrane surface and to recover a filtration speed. However, a device for the backwash operation (a backwash pump, an automatic valve, etc.). Etc.) are complicated, and there is a problem that equipment cost is increased.

[0008] In order to continue membrane filtration without increasing the fresh water production cost (operating power) per filtered water and without decreasing the filtration speed, a raw water supply method intermediate between cross flow filtration and total filtration is as follows. It is effective to intermittently apply a large flow rate to the membrane surface. However, in this case, a large-capacity pump for intermittently applying a large flow rate to the membrane surface is required, and there is a problem that equipment cost is increased.

For these reasons, conventionally, in the membrane separation device, a device for reducing the driving power without reducing the filtration rate has been required.

The present invention has been made in view of the above-mentioned conventional circumstances, and provides a low power and low filtration rate by intermittently applying a high flow rate to a membrane surface without using a pump. An object of the present invention is to provide a membrane separation device capable of continuing operation.

[0011]

The membrane separation device of the present invention comprises:
A cross-flow type membrane module having an inlet for raw water and an outlet for concentrated water, a concentrated water discharge pipe connected to the outlet of the membrane module, and an inlet connected to the inlet of the membrane module; A raw water introduction path having an open portion, wherein the concentrated water discharge pipe comprises:
It is a siphon tube having a highest part at a height between the highest part of the raw water introduction path and the membrane module.

[0012]

When the concentrated water discharged from the membrane module fills the concentrated water discharge pipe, a siphon action occurs in the concentrated water discharge pipe, and rapid drainage is performed. This allows
A large flow of water moves from the raw water introduction path side to the concentrated water discharge pipe side, and a predetermined large flow velocity water flow is generated in the raw water flow path inside the membrane module. The high-speed water flow removes the cake-like product accumulated on the membrane surface of the membrane module, and recovers the filtration rate.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the membrane separation apparatus according to the present invention. FIG. 2 (a) is an enlarged view of the portion of FIG. 1, and FIG. It is sectional drawing which follows the -B line.

In the membrane separation apparatus of the present embodiment, a raw water introduction passage 2 is connected to a raw water inlet 1A at one end of a cross flow type membrane module 1, and a concentrated water discharge pipe 3 is connected to a concentrated water outlet 1B at the other end. ing.

The raw water introduction passage 2 comprises a raw water storage section 2A and a pipe 2B extending downward at the bottom of the raw water storage section 2A. The raw water storage part 2A has an upper part 2a open, and a pipe 4 for pumping up and introducing a certain amount of raw water using a pump (not shown).

On the other hand, the concentrated water discharge pipe 3 is connected to the start-up section 3A.
The concentrated water discharge pipe 3
It is configured so that the action of the siphon can be generated.

The membrane module 1 is formed by filling a container with a membrane element in which both ends of a bundle of a plurality of hollow fiber membranes 5 are fixed with potting materials 6 (6A, 6B). By providing the end face of the hollow fiber membrane 5 at the end face, the raw water flows into the raw water flow path 5A inside the hollow fiber membrane 5, and the permeated water of the hollow fiber membrane 5 is provided on the side wall of the membrane module 1. The concentrated water is extracted from the permeated water extraction pipe 7, while the concentrated water flows through the hollow fiber membrane 5 and flows out from the potting material 6 </ b> B side.

Reference numeral 8 denotes a drain tank for storing the concentrated water discharged from the concentrated water discharge pipe 3.

In the membrane separation apparatus of the present embodiment, the raw water storage section 2A of the raw water introduction path 2 is provided with a starting section 3 of a concentrated water discharge pipe.
It is provided at a sufficiently high level so that a water level higher than the water level of A can be maintained.

In such a membrane separation device, membrane filtration is promoted by the head difference between the water level W ₁ of the raw water introduction passage 2 and the water level of the permeate extraction pipe side.

With the progress of the membrane filtration, the water level W ₂ of the rising portion 3A of the concentrated water discharge pipe 3 rises, and finally the inside of the concentrated water discharge pipe 3 becomes full and the siphon works, and the concentrated water is instantaneously discharged. The raw water in the raw water introduction passage 2 flows through the membrane module 1 at a high flow rate. Due to the high-speed flow of the raw water, the deposits on the membrane surface of the membrane module 1 are separated.

As described above, the cake-like product accumulated on the membrane surface by the action of the siphon is intermittently (periodically) removed, and the filtration rate is restored.

In the membrane separation apparatus of the present invention, the form of the membrane module is not particularly limited as long as it is a membrane element such as a hollow fiber or a flat membrane which is processed and filled inside the membrane module. In addition, various types of membrane module containers such as a plastic cylindrical one and a concrete one can be used. The number of membrane modules is not limited to one, and a plurality of membrane modules may be provided. In this case, even if each membrane module is provided with a raw water introduction path and a concentrated water discharge pipe, the raw water introduction path and the concentrated water A discharge pipe may be provided.

The number of membrane elements provided in the membrane module is not limited to one, but may be plural. For example, as shown in FIG. 3, a plurality of membrane elements 11 may be fixedly provided in the membrane module 1 with the fixing plate 12. In the membrane separation device shown in FIG. 3, a top plate 13 having an air vent pipe 13A is provided above the raw water introduction passage.
Is attached. Other configurations are the same as those of the membrane separation device shown in FIG. 1, and members having the same functions are denoted by the same reference numerals.

Further, as shown in FIG. 4, the membrane separation device of the present invention may be one in which the membrane module 1 and the raw water introduction path 2 are formed as an integral container. Even in the membrane separation device shown in FIG. 4, the raw water comes into contact with the hollow fiber membrane 5 and the permeated water flows through the hollow fiber membrane 5 to pass through the open end of the potting material 6A and the permeated water extraction section 7A and the extraction pipe 7 The concentrated water is discharged from the concentrated water discharge pipe 3. Then, a siphon action is exerted on the concentrated water discharge pipe due to a decrease in the filtration speed, and the concentrated water is discharged at a stroke. The product is removed and the filtration rate is restored.

When the concentrated water discharged from the concentrated water discharge pipe 3 is sufficiently concentrated, as shown in FIG.
The concentrated water from the concentrated water discharge pipe 3 is returned to the raw water introduction path 2 through a circulating water tank (not shown) when the liquid is guided to the drainage tank 8 and needs to be circulated and filtered.

In the membrane separation device of the present invention, the control of the discharge amount and discharge frequency of the concentrated water can be appropriately determined by setting the size of the air pool in the concentrated water discharge pipe rising section. Alternatively, as shown in FIG. 5, the automatic valve 14 is connected to the air reservoir 3B of the raised portion 3A of the concentrated water discharge pipe 3, the automatic valve 14 when the water level W ₁ of the raw water introduction passage 2 becomes constant or Control may be performed by operating the siphon by opening and closing. In this case, as illustrated, it is also possible to so as to open and close the automatic valve 14 the water level W ₁ of the raw water introduction passage 2 to sense the use of electrical sensing instrument 15.

As shown in FIG. 6, a vacuum pump 17 sucks the air from an automatic valve 14 provided in an air reservoir 3B of a rising portion 3A of a concentrated water discharge pipe via a vacuum tank 16.
By forcibly filling the concentrated water discharge pipe 3 with water, a siphon function can be achieved.

Further, when the release water level on the filtered water side is higher than the membrane surface, the effective water level difference of filtration can be secured by increasing the water level of the raw water introduction channel by the water level. it can.

The other parts of the membrane separation apparatus shown in FIGS. 4, 5 and 6 are the same as those of the membrane separation apparatus shown in FIG.
The same members are denoted by the same reference numerals.

FIG. 7 is a sectional view showing a further different membrane separator of the membrane separator of the present invention.
The members having the same functions as those of the membrane separation device shown in FIG.

In the membrane separation apparatus of the present embodiment, the permeated water extraction pipe 7 is connected to the lower part of the permeated water storage tank 9, and the permeated water in the permeated water storage tank 9 is discharged from the overflow pipe 9A. by, its water level W ₃ is always configured to be constant.

A connecting pipe 10 is provided for connecting the pipe 2B of the raw water introduction pipe 2 and the same level section below the rising section 3A of the concentrated water discharge pipe 3.

A head difference ΔH ₁ is secured between the water level W ₃ of the permeated water storage tank 9 and the water level W ₁ of the raw water introduction passage 2, and this head difference ΔH ₁ serves as a driving force for filtration. A fixed amount of filtered water is obtained.

On the other hand, the communication pipe 10 sets the minimum water level of the raw water introduction passage 2 and acts as a siphon breaker, and is lower than the water level W ₃ of the permeated water storage tank 9.
A head difference ΔH ₂ is formed. In such a membrane separation device, when the rising portion 3A of the concentrated water discharge pipe 3 becomes full due to a decrease in the filtration speed, the discharge of the concentrated water and the movement of the retained water in the raw water introduction passage 2 are performed by the action of the siphon. The water level W ₁ in the raw water introduction channel 2 gradually decreases, and finally reaches the connection portion of the communication pipe 10. At this time, air enters the communication pipe 10, the siphon is interrupted, and the movement (discharge) of the retained water in the raw water introduction path 2 stops.

[0037] Moreover, the negative this time, the water level of the raw water flow path, i.e. the position of the communication pipe 10, since there is water head difference [Delta] H ₂ between the water level W ₃ of permeate, which corresponds to the water head difference [Delta] H ₂ Pressure is generated on the membrane surface in the membrane module 1 and backwashing occurs in which water moves in the direction opposite to the filtration direction from the permeated water side to the raw water flow path side.

Therefore, the synergistic effect of the backwashing effect and the high-speed water flow generated in the membrane module 1 by the discharge of the concentrated water by the siphon effectively removes the cake-like product on the membrane surface.

However, at this time, air does not enter the permeated water side due to the presence of the retained water in the permeated water storage tank 9.
Hydrophobicity and drying of the membrane surface of the membrane module 1, and furthermore, destruction accidents of the membrane module due to the impact of the mixed flow of water and air are prevented.

Further, as described above, since the siphon is cut off by the connecting pipe 10 and the discharge of the concentrated water is stopped, the water retained in the raw water flow path in the membrane module 1 is not discharged. For this reason, air does not enter from the raw water flow path side to hydrophobize and dry the membrane surface, and the destruction of the membrane module is also prevented.

[0041]

As described above in detail, according to the membrane separation apparatus of the present invention, membrane filtration can be promoted by utilizing the head difference between the raw water flow path and the permeated water flow path. When the filtration rate is reduced due to the cake-like product adhering to the membrane surface as the process proceeds, a high-flow water stream is automatically generated intermittently using the siphon action of the concentrated water discharge pipe. In this way, the cake-like product adhering to the membrane surface of the membrane module can be removed to recover the filtration rate.

According to the membrane separation device of the present invention, it is possible to automatically and intermittently generate a water flow having a large flow rate for recovering the filtration speed with a simple configuration without providing a large-capacity pump. Therefore, it is possible to perform an efficient membrane filtration process with a low operation power and a practical filtration speed secured.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a membrane separation device of the present invention.

2 (a) is an enlarged view of FIG. 1, and FIG. 2 (b) is a cross-sectional view taken along line BB of FIG. 2 (a).

FIG. 3 is a sectional view showing another embodiment of the membrane separation device of the present invention.

FIG. 4 is a cross-sectional view showing another embodiment of the membrane separation device of the present invention.

FIG. 5 is a cross-sectional view showing another embodiment of the membrane separation device of the present invention.

FIG. 6 is a sectional view showing another embodiment of the membrane separation device of the present invention.

FIG. 7 is a sectional view showing another embodiment of the membrane separation device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Membrane module 2 Raw water introduction path 3 Concentrated water discharge pipe 3A Start-up part 5 Hollow fiber membrane 6 Potting material 7 Permeated water extraction pipe 8 Drain tank 9 Permeated water storage tank 10 Communication pipe 11 Membrane element 14 Automatic valve 16 Vacuum tank 17 Vacuum pump

Claims (1)

(57) [Claims] 1. A cross-flow type membrane module having an inlet for raw water and an outlet for concentrated water, a concentrated water discharge pipe connected to the outlet of the membrane module, and connected to the inlet of the membrane module. A concentrated water discharge pipe, wherein the concentrated water discharge pipe has a height between the highest part of the raw water introduction path and the membrane module. A membrane separation device characterized by being a siphon tube having the highest part.