JPH04256425A - Back washing device for filtration - Google Patents

Abstract

PURPOSE:To attain the execution of back washing within short time and at short interval and to enable maintenance for a long time with excellent back washing effect by connecting compressed gas supplying source to the reservoir provided in the way to passage of permeated liq and backwashing with filtrate in the reservoir by using the compressed gas as a power source of back washing. CONSTITUTION:At the time of backwashing, closing values 10, 14, a value 12 and a by-pass valve 8 are opened and the compressed gas for backwashing is applied to the backwashing reservoir 9, and a permeated liq, 16 in the reservoir 9 is made to flow to the separating membrane 3 and the suspended matter of solute stuck to the surface of the separation mambrane 3 and clad, etc., are washed away and discharged into an original liquid tank 1. Simultaneously, as the by-pass valve 8 is opened, original liquid 15 supplied by pump 2 is recovered into the original liquid tank 1 together with the liquid flowing by backwashing through the by-pass pipe 7. Also, original liquid side pressure of the separating membrane module 3 is reduced and pump 2 is continued operation in spite of backwashing.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backwashing device for regenerating a filtration membrane or a filtration filter. More specifically, the present invention is not particularly limited to liquids such as ultrafiltration (also referred to as UF) devices and microfiltration (also referred to as MF) devices. The present invention relates to a backwashing device suitable for use in a device that performs concentration or filtration.

0002

[Prior Art] As a means of removing clogging of a filtration membrane or filtration filter and regenerating the filtration membrane or filtration filter, the permeated liquid is reversed to remove solutes, suspended substances, etc. on the surface of the filtration membrane or filtration filter. (Liquid to be treated)
Backwash equipment is used that either collects the water as a concentrate or disposes it as blow water. This conventional backwashing device is
For example, as shown in FIG. 5, there is a stock solution tank 101, a supply pump 102, and a separation membrane module 10 as a filtration means.
3, a stock solution supply system 104 that sequentially connects these, a concentrate recovery system 105 that returns the concentrate discharged from the separation membrane module 103 to the stock solution tank 101, and a filtrate tank 108 that carries the permeate 113 from the separation membrane module 103. A permeate supply system 106 that leads to the permeate, a filtration valve 107 that opens and closes the permeate supply system 106, a permeate tank 108 that stores the permeate 113, and a part of the permeate 113 from the permeate tank 108 for backwashing. Separation membrane module 10
3, and a backwash gate valve 110 that opens and closes a backwash flow path 111 thereof. This backwashing device closes a filtration valve 107, opens a backwash valve 110, and rotates a backwash pump 109 to cause the permeate 113 in the permeate tank 108 to flow back to the separation membrane module 103. . This backwashing
It is usually performed in a relatively long cycle of several months to one day, or in a short cycle of several tens of minutes. For example, in microfiltration equipment used to recover radioactive waste from cooling water in nuclear power plants and the like, backwashing is performed once every four months.

0003

[Problems to be Solved by the Invention] However, according to the conventional backwashing device that performs backwashing in a relatively long cycle,
There is a problem that the recovery of the filtration rate during backwashing gradually becomes worse, and the backwashing effect decreases.

[0004] Furthermore, since conventional backwashing devices use a pump to backflow the permeate, frequently turning the motor on and off and driving it for several seconds is a problem for the motor and This is undesirable as it may lead to destruction of the magnetic relay. Moreover, the response when turning the pump ON and OFF is delayed by several seconds. For this reason, short-time backwashing is impossible with conventional backwashing equipment, and high-cycle backwashing is practically difficult. It is also possible to improve responsiveness to backwash operations by constantly operating the pump by circulating backwash liquid, but running costs (
In addition to being uneconomical due to excessive power consumption (power consumption, etc.), the permeate may be denatured.

An object of the present invention is to provide a backwashing device for filtration which has a high backwashing effect and can maintain it for a long period of time.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present inventors have repeatedly studied the correlation between the filtration speed and backwash time and backwash amount of UF devices and MF devices, and have found that the filtration time The shorter the backwashing time, that is, the shorter the backwashing cycle, the faster the permeation rate and the cumulative amount of work (
It has been found that the method is also efficient in terms of filtration amount/time. That is, as shown in FIG. 4, the shorter the backwash time is, the higher the average filtration rate is for 1 second than for 2 seconds, for example. Moreover, the backwashing effect is improved by shortening the backwashing time and making the backwashing interval much shorter than in the past.

The present invention is based on this knowledge, and includes a backwashing device that regenerates a filtration membrane or a filtration filter by causing a permeate to flow back through the filtration membrane or a filtration filter. A reservoir is provided in the reservoir, and a compressed gas supply source is connected to the reservoir, and the compressed gas is used as a drive source for backflow to backwash with the permeate in the reservoir.

[0008]

[Operation] Therefore, at the same time that the compressed gas for backwashing is supplied into the reservoir, the permeated liquid in the reservoir instantly flows back to the filter, flushing solutes and suspended substances on the filter surface to the feed liquid side, and cleaning the filter. Reproduce. After backwashing is completed, the compressed gas is removed from the reservoir, and the reservoir is again filled with permeate, which then flows out toward the filtration outlet.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the structure of the present invention will be explained in detail based on embodiments shown in the drawings.

FIG. 1 shows an embodiment in which the backwashing device of the present invention is applied to a cross-flow type ultrafiltration device. This ultrafiltration device connects a tank 1 that stores a stock solution, a pump 2 that extracts a liquid to be treated, that is, a stock solution 15 from the tank 1 and supplies it to a filtration means, and a separation membrane module 3 as a filtration means. a concentrated solution supply system 4 that supplies the concentrated solution 15 in the concentrated solution tank 1 to the separation membrane module 3; and a concentrated solution recovery system 5 that returns concentrated water discharged from the separation membrane module 3 to the concentrated solution tank 1.
and a permeate supply system 6 that supplies the permeate (filtrate) that has passed through the separation membrane module 3 to a place or device that requires it (hereinafter referred to as a use point). The raw solution supply system 4 and the concentrated solution recovery system 5 are connected by a bypass pipe 7, and are provided so as to be opened and closed by a valve 8. A backwash reservoir 9 is connected to the permeate supply system 6, and a valve 10 for opening and closing the permeate supply system 6 is provided downstream thereof. Further, a compressed gas supply source 11 that supplies pressurized gas for backwashing is connected to the top of the backwash reservoir 9, and a compressed gas inlet valve is provided between the compressed gas supply source 11 and the backwash reservoir 9. 12 so that the supply of pressure gas is interrupted. Furthermore, the compressed gas inlet valve 12 and the backwash reservoir 9 are communicated with the atmosphere via a branch pipe 13 and an exhaust valve 14.

[0011] In this example, the filtration means is cross flow filtration (tangential flow filtration).
For example, a ceramic filter (trade name: Ceraflow, manufactured by Nippon Millipore Limited) is used, but the application is not particularly limited to this, and can be carried out regardless of the filtration method and filter material. In addition, any compressed gas can be used as long as it does not adversely affect the components of the permeated liquid.
It is preferable to use a relatively inexpensive material such as air because it is economical. Further, as the exhaust valve 14, it is preferable to use a valve that exhausts the high pressure gas in the reservoir 9 into the atmosphere in about 0.1 to 5 seconds. Furthermore, although backwashing is generally performed using a timer, a liquid level switch 17 may be provided in the backwashing reservoir 9 to perform backwashing with a constant amount of liquid. Note that the valve 8 is for lowering the pressure on the stock solution side during backwashing, and becomes unnecessary if the backwash pressure is made higher than the filtration pressure.

According to the backwashing device configured as described above, when the valve 10 is opened, the stock solution drawn from the stock solution tank 1 by the pump 2 is supplied to the separation membrane module 3 and filtered, and the permeate liquid 16 is passed through the membrane. After being sent to the reservoir 9 from the outlet, it is pumped to the filtrate outlet. On the other hand, concentrate 17
is recovered to the stock solution tank 1 via the recovery system 5. Also, during backwashing, valves 10 and 14 are closed, valve 12 and bypass valve 8 are opened, and the compressed gas for backwashing is transferred to the backwash reservoir 9.
The permeated liquid 16 in the reservoir 9 is caused to flow back to the separation membrane 3, and the solute suspended matter, crud, etc. adhering to the surface of the separation membrane 3 are washed away and discharged to the stock solution tank 1 side. At the same time, since the bypass valve 8 is opened, the stock solution 15 supplied from the pump 2 is collected into the stock solution tank 1 together with the liquid flowing through the bypass pipe 7 by backwashing. The pressure on the raw solution side of the separation membrane module 3 is lowered. Pump 2 continues to operate regardless of backwashing.

This movement is shown in the time chart of FIG. After the filtration pump 2 starts operating, the valve 10 is opened and filtration is started. When a predetermined filtration time has elapsed, the valve 10 is closed and the valves 8 and 12 are opened to perform backwashing. When a predetermined backwashing time has elapsed, the valves 8 and 12 are closed, and then the valve 14 is opened, and the compressed gas supplied to the reservoir 9 is exhausted to the atmosphere. This is considered as one cycle and is repeated sequentially. Here, as a result of research by the present inventors, the filtration time, backwash cycle, and backwash time are shorter, the faster the permeation rate is, and the more efficient the total amount of work is. For example, when targeting an ultrafiltration membrane with a molecular weight cutoff of 500 to 500,000 or a microfiltration membrane with a pore size of 0.01 μm to 10 μm, the filtration time is 10 to 10 μm.
00 seconds, backwashing for 0.1 to 100 seconds, more preferably filtration for 60 to 180 seconds, and backwashing for 0.2 to 3 seconds. In addition, the backwash pressure is approximately 0.1 kgf/cm2
~50kgf/cm2, more preferably about 1kgf/
cm2 to 6kgf/cm2, most preferably about 3k
gf/cm2.

Experimental Example 1 In the cross-flow type ultrafiltration apparatus shown in Fig. 1, a ceramic filter (trade name: Ceraflow, manufactured by Nippon Millipore Limited) with a pore size of 0.2 μm and a membrane area of 0.14 m2 was adopted as the separation membrane. Filtration was performed using apple juice as a stock solution. Volume of stock solution is 20 liters, filtration pressure approximately 3 kgf/cm2, backwash pressure approximately 6.5 kgf/c
m2, filtration was performed for 240 seconds, backwash interval was 244 seconds, and backwash time was 3 seconds. As a result, as shown in FIG. 3, the filtration rate was approximately twice that of the case without backwashing. Furthermore, when backwashing was stopped, the filtration rate suddenly decreased, indicating that backwashing was effective.

Experimental Example 2 Filtration was carried out in the conventional backwashing apparatus shown in FIG. 5 using the same separation membrane and stock solution as in Experimental Example 1. The backwash time at this time is 30 seconds, and the backwash interval is 30 minutes (filtration time is 30 seconds).
minutes). Further, the filtration pressure was approximately 3 kgf/cm2, and the backwashing pressure was approximately 3 kgf/cm2. The results of this experiment are shown in phantom lines in FIG. As is clear from this result, the effect of backwashing performed in a relatively long cycle using a conventional backwashing device is that a faster filtration rate can be obtained than when no backwashing is performed, but it is half that of Experimental Example 1. It can be seen that only a moderate filtration speed was reached, and the recovery of the filtration speed during backwashing gradually worsened.

[0016]

Effects of the Invention As is clear from the above explanation, the filtration backwashing device of the present invention provides a reservoir in the middle of a channel through which permeated liquid flows, connects a compressed gas supply source to the reservoir, and supplies compressed gas to the reservoir. Since the permeated liquid in the reservoir is used to perform backwashing with the permeated liquid in the reservoir, the permeated liquid in the reservoir instantly flows back to the filtration membrane or filtration filter at the same time as compressed gas is supplied. Backwashing can be performed at short intervals. As shown in FIG. 3, by increasing the cycle of backwashing, the backwashing effect is higher than that of conventional backwashing equipment, and there is less tendency for the permeation rate to drop due to repeated backwashing.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a backwashing device of the present invention.

FIG. 2 is a time chart showing the operation of the backwashing device in FIG. 1;

FIG. 3 is a graph showing the relationship between backwashing and changes in filtration rate.

FIG. 4 is a graph showing the influence of backwash interval on average filtration rate in relation to backwash time.

FIG. 5 is a schematic diagram showing a conventional backwashing device.

[Explanation of symbols]

3 Filtration means (filtration membrane or filtration filter) 6 Channel for flowing permeate (permeate supply system) 9 Reservoir 11 Compressed gas supply source 12 Compressed gas inlet valve 14 Exhaust valve 15 Stock solution 16 Permeate in reservoir

Claims (6)

[Claims] 1. A backwashing device that regenerates the filtration membrane or filtration by causing permeate to flow back through the filtration membrane or filtration filter, wherein a reservoir is provided in the middle of a channel through which the permeate flows, and a compressed gas is supplied to the reservoir. A backwashing device for filtration, characterized in that the device is connected to a supply source and backwashes the permeate in the reservoir using compressed gas as a drive source for backflow. 2. The compressed gas has a pressure of about 0.1 kgf/cm.
2. The backwashing device for filtration according to claim 1, wherein the pressure is 2 to 50 kgf/cm2. 3. The compressed gas has a pressure of about 1 kgf/cm2.
Claim 1 characterized in that it is ~6 kgf/cm2.
Backwash device for filtration as described. 4. The compressed gas is approximately 3 kgf/cm2.
The filtration backwash device according to claim 1, characterized in that: 5. Filtration is carried out for 10 to 1000 seconds at a rate of 0.
The backwashing device for filtration according to any one of claims 1 to 4, wherein the backwashing is performed alternately for 1 to 100 seconds. Claim 6: Filtration for 60 to 180 seconds at 0.2 to 180 seconds.
The backwashing device for filtration according to any one of claims 1 to 4, wherein the backwashing is performed alternately for 3 seconds.