JP2002066269A - Method for backness washing of hollow fiber membrane filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold a hollow fiber membrane under steady state when backward washing of a filter is performed. SOLUTION: When backward washing is performed after an inlet valve 5 and an outlet valve 7 are opened and an original water is fed into a trunk container 2 and filtration processing wherein suspended substances included in the original water are removed by means of the hollow fiber membrane 17 is performed, passing the original water through is stopped and an air feeding valve 9 is opened and, after air is introduced into the trunk container 2 to elevate the pressure in the trunk container 2, a drain valve 11 and a vent valve 13 are opened to drain the original water from the drain valve 11 and a backward washing flow (a downward flow) flowing from the inside to the outside of the hollow fiber membrane 17 is generated in the trunk container 2 to perform backward washing of the hollow fiber membrane 17 under the steady state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for backwashing a hollow fiber membrane filtration apparatus, and more particularly to a method for separating and removing a suspension mainly composed of iron rust or the like present in condensate or waste liquid in a plant. The present invention relates to a method for backwashing a hollow fiber membrane filtration device suitable for backwashing a hollow fiber membrane filtration device.

[0002]

2. Description of the Related Art Conventionally, a hollow fiber membrane module is installed as a filtration device used for separating and removing a suspension mainly composed of iron rust or the like present in condensate or waste liquid in a thermal or nuclear power plant. The hollow fiber membrane filtration device is adopted. Hollow fiber membrane filtration equipment, with the passage of filtration processing time,
The suspension to be removed from the raw water is captured on the outer surface of the hollow fiber membrane, and the filtration efficiency of the hollow fiber membrane decreases as the amount of the captured suspension increases. For this reason, in the hollow fiber membrane filtration device, backwashing is performed in order to remove the suspended matter trapped on the outer surface of the hollow fiber membrane.

[0003] When backwashing a hollow fiber membrane filtration device,
For example, as described in JP-A-3-65220, compressed air is fed from the inside to the outside with respect to the hollow fiber membrane arranged along the axial direction in a container for storing raw water, There has been proposed a method of removing a suspended matter trapped on the outer surface of a hollow fiber membrane by an upward flow of air bubbles.

[0004]

In the above prior art, compressed air is sent from the inside to the outside to the hollow fiber membrane fixed to the upper end of the container and the lower end of which is a free end. Because it forms an upward flow of air bubbles,
During backwashing, the upward flow of air bubbles may disturb, entangle, or twist the hollow fiber membrane. As a result, the hollow fiber membrane is entangled with the suspension, and a suspension remains at the portion, and the backwashing efficiency may be reduced or the thread of the hollow fiber membrane may be broken. This is because the holding state of the hollow fiber membrane module composed of a plurality of hollow fiber membranes is free at the lower end with respect to the fixed upper end, so that the upward flow of air bubbles flows into the cylinder containing the hollow fiber membrane module. Is formed, the lower end of the hollow fiber membrane is disturbed or twisted by the upward flow, and the hollow fiber membranes are entangled with each other.

It is an object of the present invention to provide a method for backwashing a hollow fiber membrane filtration device which can maintain a hollow fiber membrane in a steady state during backwashing.

[0006]

In order to achieve the above object, the present invention provides a container for forming a fluid flow path connecting an inlet for introducing raw water and an outlet for discharging raw water; A hollow fiber membrane arranged to capture a suspension in the raw water by the flow of the raw water, and a flow passage for discharging the raw water introduced from the inlet through the outlet in the fluid flow path of the container. A water passage through which the raw water flows from the inlet to the outlet at the time of water is formed, and the hollow fiber membrane is disposed along the water flowing direction of the raw water, and the axial end of the hollow fiber membrane is the downstream end of the water passage. When performing backwashing of the hollow fiber membrane filtration device in which the upstream end of the water passage is a free end, the flow of the raw water is stopped, gas is introduced into the container, and gas is introduced into the container. After increasing the pressure, the raw water in the container is transferred to a portion different from the outlet. The method employs a backflush method of a hollow fiber membrane filtration device, wherein the backflush is discharged from a washing discharge port and a backwash flow in a direction opposite to a flowing direction of raw water is generated around the hollow fiber membrane. is there.

In adopting the backwash method of the hollow fiber membrane filtration device, the flow of raw water is stopped, gas is introduced into the container to increase the pressure in the container, and then the raw water in the container is drained. Unlike the outlet, the water is discharged from the backwash discharge port below the inlet, and a downward flow reverse to the flow direction of the raw water can be generated around the hollow fiber membrane.

[0008] Further, when the backwash method of the hollow fiber membrane filtration device is adopted, the flow of raw water is stopped, and the raw water in the container is discharged from a discharge port for backwash at a portion different from the discharge port.
A backwash flow is generated around the hollow fiber membrane in a direction opposite to the flowing direction of the raw water, and the backwash water is continuously supplied into the container from the discharge port so that the backwash flow is formed around the hollow fiber membrane. It can also occur continuously.

Further, when adopting the backwash method of the hollow fiber membrane filtration device, the flow of raw water is stopped, and unlike the discharge port, the raw water in the container is different from the discharge port in the backwash discharge port on the lower side from the inlet. And a downward flow in the direction opposite to the flow direction of the raw water is generated around the hollow fiber membrane, and backwash water is continuously supplied into the container from the discharge port and descends around the hollow fiber membrane. The stream can also be generated continuously.

[0010] When the backwashing method of each hollow fiber membrane filtration device is adopted, after backwashing the hollow fiber membrane, the backwashing is once stopped, the container is filled with raw water, and the backflush is performed on the hollow fiber membrane. Washing can be performed again.

According to the above-mentioned means, at the time of backwashing, simultaneously with backwashing from the inside to the outside of the hollow fiber membrane, drainage for draining the raw water in the container is simultaneously performed, so that the raw water flows around the hollow fiber membrane. Since a backwash flow or a downward flow in the direction opposite to the water direction is generated, it is possible to prevent an upward flow due to air bubbles from being generated around the hollow fiber membrane and turbulence of the hollow fiber membrane. In addition, the hollow fiber membrane can be kept in a steady state by preventing twisting, and the backwashing efficiency can be improved.

[0012] Further, at the time of backwashing, backwash water is continuously supplied from the inside to the outside of the hollow fiber membrane, and the backwash flow in the direction opposite to the flowing direction of the raw water or descends around the hollow fiber membrane. Since the flow is generated, it is possible to prevent the upward flow due to air bubbles from being generated in the hollow fiber membrane, so that the turbulence, entanglement and twisting of the hollow fiber membrane are prevented, and the hollow fiber membrane is kept stationary. The state can be maintained, which can contribute to the improvement of the backwashing efficiency.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1A is a schematic configuration diagram of a hollow fiber membrane filtration device showing an embodiment of the present invention, and FIG. 1B is a flowchart for explaining a backwashing method of the filtration device shown in FIG.
(C) is a process drawing for explaining a method of backwashing the apparatus shown in (a). In FIG. 1, the hollow fiber membrane filtration device includes a body container 2 having a substantially cylindrical shape. The bottom side of the body container 2 is closed, and a lid container 1 is mounted on an upper side. A tube sheet 14 is mounted between the body and the body container 2.
The body container 2 is configured as a container that forms a fluid flow path connecting an inlet for introducing raw water and an outlet for discharging raw water, a drain pipe 10 is connected to a bottom side, and an inlet pipe is connected to a side bottom side. 4 is connected, and a vent pipe 12
Is connected. The drain pipe 10 is connected to the body container 2 as an outlet for backwashing, and a drain valve 11 is inserted in the drain pipe 10 in the middle of the pipe. The inlet pipe 4 is configured as an inlet for introducing raw water and a raw water introduction path. An inlet valve 5 is inserted in the pipe of the inlet pipe 4. The vent pipe 12 is configured as a vent port and a vent passage, and a vent valve 13 is inserted in the middle of the vent pipe 2.

An outlet pipe 6 forming a discharge port and a discharge passage is connected to a substantially central portion of the lid container 1, and an air pipe 8 is connected in the middle of the outlet pipe 6.
An outlet valve 7 is inserted in the middle of the outlet pipe 6,
An air supply valve 9 is inserted in the middle of the air pipe 8.

On the other hand, a plurality of hollow fiber membrane modules 3 are mounted on the tube sheet 14. Each hollow fiber membrane module 3
Hollow fiber membrane module protection cylinder 1 formed in a substantially cylindrical shape
8, a plurality of hollow fiber membranes 17 are provided. The plurality of hollow fiber membranes 17 are arranged along the flow direction of the raw water in a bundled state, and the upper end (the downstream end of the water passage) of both ends in the axial direction is fixed, and the lower end (upstream of the water passage). Side end) is a free end. That is, the plurality of hollow fiber membranes 17 are arranged in the protective cylinder 18 in a state of being hung down.

When operating the hollow fiber membrane filtration device having the above configuration, first, in a stop step (step S1) which is an initial state, an inlet valve 5, an outlet valve 7, an air supply valve 9, a drain valve 11, and a vent valve 11 are provided. Are all closed.

Next, in treating the raw water in the water passing step (step S2), the inlet valve 5 and the outlet valve 7 are opened, the raw water is introduced into the body container 2 through the inlet pipe 4, and Raw water flows inward from the outer surface of each hollow fiber membrane 17 housed in 18, and around the hollow fiber membrane 17, an inlet pipe (inlet) 4 to an outlet pipe (discharge port) 6.
A water passage through which the raw water flows is formed, and a filtration process is performed to capture suspended matter mainly composed of iron rust and the like present in the raw water, and the raw water from which the suspended matter is separated and removed is treated water. Is collected in the lid container 1 and sent to the downstream system via the outlet pipe 6. The suspension filtered and separated by this treatment is captured and accumulated on the outer surface of the hollow fiber membrane 17. For this reason,
When this filtration process is continued, the pores formed in each hollow fiber membrane 17 are gradually closed, whereby the filtration resistance of the hollow fiber membrane 17 increases, and the internal pressure of the body container 2 and the pressure of the lid container 1 increase. The difference from the internal pressure, that is, the filtration pressure difference increases. When the filtration pressure difference reaches a specified value or when the amount of suspended matter trapped in the hollow fiber membrane 17 reaches a specified value, backwashing of the hollow fiber membrane module 3 is performed.

This backwashing is performed in three steps: backwashing step 1, backwashing step 2, and backwashing step 3. First, backwashing process 1
In (Step S3), the inlet valve 5 and the outlet valve 7
Is closed, the air supply valve 9 is opened, and air, for example, is introduced into the air pipe 8 as a gas, and air pressure is applied to the inside of the lid container 1 and the body container 2. Then, the pressure in the body container 2 and the lid container 1 is increased, and the backwashing step 2 (step S4)
The drain valve 11 and the vent valve 13 are opened with the air supply valve 9 opened. When this operation is performed, as shown in FIG. 2, a backwash flow is generated in the body container 2 from the inside to the outside of the hollow fiber membrane 17 due to expansion of air. This backwashing flow is formed as a downward flow flowing from the upper side to the bottom side of the body container 2, and the suspended matter trapped on the outer surface of the hollow fiber membrane 17 is removed by the backwashing flow and removed. The suspension is discharged from the drain valve 11 to the outside of the body container 2 together with the backwash water. As a result, the outer surface of the hollow fiber membrane 17 is washed by the back washing, and the filtration pressure difference is recovered to some extent. Thereby, the filtration efficiency of the hollow fiber membrane 17 can be improved.

As described above, at the time of the backwash, the water in the body container 2 is drained from the drain valve 11 at the same time as the backwash, so that the downward flow as the backwash flow is formed around the hollow fiber membrane 17. This can prevent the hollow fiber membrane 17 from being disturbed, entangled, or twisted, and can maintain the hollow fiber membrane 17 in a steady state even during backwashing.

Further, in the present embodiment, the backwashing efficiency is increased by adding a backwashing step 3 (step S5) after the backwashing steps 1 and 2. That is, after the backwashing step 2, the air supply valve 9 and the drain valve 1
1 is closed, the inlet valve 5 is opened to supply raw water into the body container 2, the body container 2 is filled with raw water, and then the process proceeds to the water passing step, the vent valve 13 is closed, and the outlet valve 7 is opened. The inside of the filtration device is completely filled. Thereafter, the above-described backwashing steps 1 and 2 are repeated again, whereby the backwashing efficiency can be improved. In addition, a vent hole 19 that forms a passage for air or raw water is formed on the upper side of the protection cylinder 18.

Next, a second embodiment of the present invention will be described with reference to FIGS.

In this embodiment, a make-up water inlet pipe 15 is connected to an outlet pipe 6 of the hollow fiber membrane filtration device shown in FIG. 1 and a make-up water supply valve 16 is inserted in the middle of the make-up water inlet pipe 15. The other configuration is the same as that of FIG.

When the hollow fiber membrane filtration device of the present embodiment is operated, the same processes as those in FIG. 1 are performed in the stopping step and the water passing step. Then, the stop process (step S
1) After the water passing step (step S2), when the filtration pressure difference reaches the specified value, the drain valve 11 and the vent valve 13 are first opened as the backwashing step 1, and the raw water in the body container 2 is discharged. Drain for water.

Next, as a backwashing step 2 (step S4), the make-up water supply valve 16 is opened to continuously supply make-up water as backwashing water into the lid container 1 from the inside of the hollow fiber membrane 17 to the outside thereof. Backwash is performed by continuously generating a backwash flow toward.
This backwash flow is generated in a direction opposite to the flow direction of the raw water,
By flowing the backwash flow continuously from the inside to the outside of the hollow fiber membrane 17, the suspended matter on the outer surface of the hollow fiber membrane 17 was removed and removed. The suspension is discharged from the drain valve 11 into the body container 2 together with the backwash water. This state is shown in FIG. The backwash flow due to the backwash water is generated as a downward flow, and the backwash flow continuously flows from the inside of the hollow fiber membrane 17 to the outside, so that the hollow fiber membrane 1
7 The suspension on the inner and outer surfaces is removed. At this time, protection cylinder 1
Since no upward flow due to air is generated in the inside 8, the occurrence of turbulence, entanglement and twisting of the hollow fiber membrane 17 can be prevented, and the hollow fiber membrane 17 can always be kept in a steady state, contributing to the improvement of the backwashing efficiency. can do. Next, after backwashing step 2,
In the backwashing step 3, the drain valve 11 is closed, the inlet valve 5 is opened, raw water is supplied into the body container 2, the body container 2 side is filled with water, the process directly proceeds to the water passing step, and the vent valve 13 is closed.
Open the outlet valve 7 to completely fill the inside of the filtration device,
Thereafter, by repeating the above-described backwashing again, the backwashing efficiency can be improved.

When performing the backwashing, the methods shown in FIGS. 1 and 3 can be combined. That is,
After the backwashing steps 1 and 2 shown in FIG.
Inside is empty. Then, after that, the make-up water supply valve 16 is opened, water is continuously supplied from the lid container 1, and the backwashing water is flown from the inside to the outside of the hollow fiber membrane 17, thereby improving the backwashing efficiency. be able to.

According to the present embodiment, the water in the body container 2 is adjusted to generate a downward flow in the body container 2, thereby preventing the hollow fiber membrane 17 from being disturbed, entangled and twisted, and Since 17 is always kept in a steady state, efficient backwashing can be performed, the backwashing efficiency can be improved, and the specification period can be extended.

[0028]

As described above, according to the present invention,
At the time of backwash, simultaneously with backwash from the inside of the hollow fiber membrane to the outside,
Draining of the raw water in the container is performed simultaneously to create a backwash or downflow around the hollow fiber membrane in the direction opposite to the flow direction of the raw water. It is possible to prevent the upward flow due to the air bubbles from occurring and to prevent the hollow fiber membrane from being entangled and twisted, to keep the hollow fiber membrane in a steady state, and to improve the backwashing efficiency. .

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention, in which (a)
Is a schematic configuration diagram of a hollow fiber membrane filtration device, (b) is a flowchart for explaining a backwash method of the device shown in (a),
(C) is a figure for demonstrating the backwash process of the apparatus shown to (a).

FIG. 2 is a view for explaining a method of backwashing the hollow filtration device shown in FIG.

FIG. 3 is a diagram showing another embodiment of the present invention,
(A) is a schematic configuration diagram of a hollow fiber membrane filtration device, (b) is a flowchart for explaining a method of cleaning the device shown in (a), and (c) describes a cleaning process of the device shown in (a). FIG.

FIG. 4 is a view for explaining a method of cleaning the apparatus shown in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lid container 2 Body container 3 Hollow fiber membrane module 4 Inlet piping 5 Inlet valve 6 Outlet piping 7 Outlet valve 8 Air piping 9 Air supply valve 10 Drain piping 11 Drain valve 12 Vent piping 13 Vent valve 14 Tube plate 15 Supply water inlet piping 16 Supply water supply valve 17 Hollow fiber membrane 18 Hollow fiber membrane module protection cylinder 19 Vent hole

Continued on the front page (72) Inventor Yoshihiro Shiozawa 3-2-1 Sachimachi, Hitachi City, Ibaraki Prefecture Inside Hitachi Engineering Co., Ltd. (72) Inventor Tohru Ikeda 3-1-1 Sachimachi, Hitachi City, Ibaraki Stock F-term in Hitachi Nuclear Power Division (reference) 4D006 GA02 HA02 KC03 KC14 KC20 MA01 PB07 PB08

Claims (5)

[Claims] 1. A container forming a fluid flow path connecting an inlet for introducing raw water and an outlet for discharging raw water, and a suspension in the raw water is captured in the container by flowing the raw water. A hollow fiber membrane that flows from the inlet to the outlet when the raw water introduced from the inlet is discharged from the outlet in the fluid flow path of the container. A water channel is formed, and the hollow fiber membrane is arranged along the water flow direction of the raw water, the downstream end of the water channel among the axial ends thereof is fixed, and the upstream end of the water channel is a free end. When performing backwashing of the hollow fiber membrane filtration device, the flow of the raw water is stopped, gas is introduced into the container to increase the pressure in the container, and then the raw water in the container is discharged to the outlet. From the backwash outlet at a location different from that of the A method for backwashing a hollow fiber membrane filtration device, wherein a backwash flow in a direction opposite to a water direction is generated. 2. A container forming a fluid flow path connecting an inlet for introducing raw water and an outlet for discharging raw water from above the inlet, and a container disposed in the container and adapted to flow through the raw water. A hollow fiber membrane that captures a suspension in water, and in the fluid flow path of the container, the raw water introduced from the introduction port is discharged from the discharge port through the discharge port. A water passage through which the raw water flows is formed, and the hollow fiber membrane is disposed along the water flowing direction, and the downstream end of the water passage among the axial ends thereof is fixed, and the upstream side of the water passage is fixed. When performing backwashing of the hollow fiber membrane filtration device whose end is a free end, the flow of the raw water is stopped, gas is introduced into the container, and the pressure in the container is increased. The outlet for backwashing the raw water in the lower side from the inlet unlike the outlet Backflow of a hollow fiber membrane filtration device, characterized by causing a downward flow in the direction opposite to the flow direction of raw water around the hollow fiber membrane. 3. A container that forms a fluid flow path connecting an inlet for introducing raw water and an outlet for discharging raw water, and a suspension disposed in the container and trapped in the raw water by flowing the raw water. A hollow fiber membrane that flows from the inlet to the outlet when the raw water introduced from the inlet is discharged from the outlet in the fluid flow path of the container. A water channel is formed, and the hollow fiber membrane is arranged along the water flow direction of the raw water, the downstream end of the water channel among the axial ends thereof is fixed, and the upstream end of the water channel is a free end. When performing backwashing of the hollow fiber membrane filtration device, the flow of the raw water is stopped, and the raw water in the container is discharged from a backwashing outlet at a site different from the outlet, and the hollow fiber membrane is filtered. In addition, a backwash in the direction opposite to the flow direction of the raw water A backwashing method for a hollow fiber membrane filtration device, comprising continuously supplying backwash water into the container from an opening to continuously generate the backwash flow around the hollow fiber membrane. 4. A container forming a fluid flow path connecting an inlet for introducing raw water and an outlet for discharging raw water from above the inlet, and a container disposed in the container and adapted to flow through the raw water. A hollow fiber membrane that captures a suspension in water, and in the fluid flow path of the container, the raw water introduced from the introduction port is discharged from the discharge port through the discharge port. A water passage through which the raw water flows is formed, and the hollow fiber membrane is disposed along the water flowing direction, and the downstream end of the water passage among the axial ends thereof is fixed, and the upstream side of the water passage is fixed. When performing backwashing of the hollow fiber membrane filtration device whose end is a free end, the flow of the raw water is stopped, and the raw water in the container is backwashed on the lower side from the inlet unlike the outlet. From the outlet for water flow around the hollow fiber membrane in the direction opposite to the flow direction of the raw water. A downward flow of
Continuously supplying backwash water into the container from the outlet,
A backwash method for a hollow fiber membrane filtration device, wherein the downward flow is continuously generated around the hollow fiber membrane. 5. After the hollow fiber membrane is backwashed,
The hollow according to any one of claims 1, 2, 3 and 4, wherein the backwashing is temporarily stopped, the container is filled with raw water, and the hollow fiber membrane is backwashed again. Backwashing method of the thread membrane filtration device.