JPH09239246A - Filtration device and cleaning method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively remove a contaminant sticking to the surface of a film, and also prevent the contaminant from re-sticking to the film and reduce the amount of a drained liquid by circulating a liquid in a circulatory path while maintaining a high pressure state on the permeation side of the film, with the help of a backward washing means during the backward washing process. SOLUTION: During the backward washing process, a flow path switching valve 7 is changed over to a backward washing side. Next, a high pressure air is allowed to flow into a backward washing 5 by changing over a switching valve 6 to cause a backward washing liquid accumulated in the backward washing tank 5 to flow back into a hollow fiber membrane module 1h from a drainage 4. In addition, the backward washing process is performed all at once, and a drain valve 14 is kept open until an inflow path 2 is emptied and the backward washing liquid is completely drained. After that, the drain valve 14 is closed, and the switching valve 6 is turned to the backward washing side, and further, the pressure on the permeation side of the film is kept at a high level by the high pressure air. Consequently, the circulating backward washing liquid cannot permeate through the film because the permeation side of the film is at a high pressure. Besides, no contaminant which is peeled off re-sticks to the film, and the contaminant sticking to the surface of the film is removed by the circulating liquid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane-utilizing type filtration means used for, for example, reusing a cleaning liquid or treating waste water, and a backwashing of the membrane-permeating liquid or compressed air to the membrane-utilizing type filtration means. The present invention relates to a filtration device equipped with a backwash means for washing a membrane by causing a fluid to flow backward to reverse the membrane permeation direction, and a washing method thereof.

[0002]

2. Description of the Related Art Membrane-based filtration means for separating oil / water using a membrane such as a microfiltration membrane or an ultrafiltration membrane has been conventionally used in a filtration device used for reusing a cleaning liquid or treating waste water. There are things that are doing.

In this method, oil / water is filtered by passing through a membrane having fine pores much smaller than the size of an oil droplet, and oil and water are separated to obtain an oil-free cleaning liquid.

FIG. 4 shows an example of a conventional filtration device utilizing a membrane-utilizing filtration means. This filtering device 100 removes dirt and oil adhering to the work W101 to be cleaned. A cleaning liquid L101 mainly composed of water and a detergent is put in the cleaning tank 101, and the work W101 is immersed therein. Then, the dirt and oil are removed by a physical action such as ultrasonic waves, stirring, and shaking. Here 102
Was exemplified as an ultrasonic oscillator.

When the workpieces W101 are continuously and successively put into the cleaning tank 101, the cleaning liquid L
Since the oil concentration of 101 increases and the cleaning ability for the work decreases, the filtration device 100 is equipped with the filtration means described below.

This is a two-stage filtering means provided downstream of the discharge path 103, the first stage is by the first circulation path 110, and the pump 111 and the floating oil recovery means 112.
It has.

The second stage is due to the second circulation path 120 downstream of the first circulation path 110, and the pump 121
And a membrane-utilizing filtration means 122. Cleaning liquid L1 in which relatively large oil droplets have been separated in the first circulation path 110
01 flows into the path of the second circulation path 120 to perform filtration. The cleaning liquid from which the filtered oil component has been removed is returned through the return path 1
It is returned to the washing tank 101 by 31.

As shown in FIG. 5, the principle of the floating oil recovery means 112 is that the cleaning liquid L110 is stored in the retention tank 112a so that the oil droplets L111a are easily contacted with each other, and the water component L1.
Small oil droplets (for example, several to several tens of μm) are gathered by the specific gravity difference between the oil droplets L12 and the oil droplets L111a and floated upward as large oil droplets (for example, several hundred μm). L111 is separated.
In the retention tank 112a, the oil component L111 is separated in the order of FIG. 5 (a), FIG. 5 (b), and FIG. 5 (c).

Further, although not shown in FIG. 5, a coalescer filter of an ultrafine fiber structure is provided in the retention tank,
In some cases, the washing liquid L101 is passed through this coalescer filter to further increase the oil droplet L111a to promote the separation of the specific gravity.

Next, as the membrane-utilizing type filtration means 122,
A hollow fiber membrane module 123 using a bundle of a large number of hollow fiber membranes 124 as an ultrafiltration membrane is used, and the cleaning liquid supplied by a pump 121 provided in the second circulation path 120 is hollow. It is a cross-flow type in which the thread film 124 flows parallel to the inner surface of the membrane wall and a part of oil water at that time is filtered by passing through the membrane wall. In the cross flow type, the hollow fiber membrane module 123 is provided in the circulation path (circulation path 120) of the cleaning liquid to be filtered in order to operate the membrane-utilizing type filtration means 122 for a long period of time.
It is a method to always create a flow parallel to the membrane to minimize contamination and clogging of the membrane surface.

The cleaning liquid that has not permeated the hollow fiber membranes 124 in the hollow fiber membrane module 123 is in the second circulation path 12.
0 will be circulated, and the oil component concentration will rise, so
The oil component passes through the secondary pressure control valve 113, returns to the first circulation path 110, and the oil component is separated by the floating oil recovery means 112.

[0012] In the filtration device 100, therefore, the oil component emulsified and dispersed in the cleaning liquid is also discharged as it circulates through the first and second circulation paths 110 and 120, so that the work is finally brought in. It is designed so that the amount of introduced oil and the amount of oil component discharged from the floating oil recovery means 112 become equal, and at the same time, the oil component concentration in the cleaning tank 101, the first and second circulation paths 110, 120. Also is stable within the range of each predetermined value.

The constituent elements included in FIG. 4 which are not explained are omitted, but 125 is a discharge valve, and 126 and 127 are hollow fiber membrane module 1 respectively.
23 primary and secondary pressure gauges.

[0014]

However, although the filtration device 100 described above employs the cross-flow type membrane-utilizing filtration means 122, if filtration is continued for a long time, oil components and The membranes of the multiple hollow fiber membranes 124 of the hollow fiber membrane module 123 are clogged due to floating contaminants and the like.

This is because in the cross-flow type filtration method, the cleaning effect on the membrane surface is determined by the balance between the flow velocity and the pressure of the cleaning liquid to be filtered flowing in parallel. With the one used, when trying to increase the flow rate of the cleaning liquid to be filtered in order to improve the cleaning effect at the time of filtration, the internal resistance of the pipe increases significantly, and the required filtration pressure also increases. This is because it may result in adhesion.

Therefore, at a predetermined interval (for example, 10 to 60)
Once every minute), the backwash valve 132 is switched to feed the high-pressure air or the membrane permeate to the hollow fiber membrane module 123 (referred to as backwash).

Here, 133 is a hollow fiber membrane module 123.
And a backwash valve 132 between the backwash valve and
The membrane permeate filtered by the hollow fiber membrane module 123 is temporarily accumulated for use as a backwash fluid, and by supplying high-pressure air to the backwash tank 133 during backwash, the inner membrane permeate (Backwash fluid) is hollow fiber membrane 1
It is intended to eliminate clogging by allowing the film of 24 to pass from the opposite direction.

During backwashing, the motor 121 and the motor 111 are also used.
Is stopped, the backwash fluid that has permeated through the membrane of the hollow fiber membrane 124 in the opposite direction, and in which the oil component and the contaminants are mixed, is discharged from the second circulation path 120 and the first circulation path 110 to the discharge path 10
3 is discharged to the outside of the circulation path from the discharge valve 125 so that it does not flow back to the cleaning tank 101.

However, the amount of backwash fluid accumulated in the backwash tank 133 is limited, and it may not be possible to completely remove contaminants from the membrane surface by one backwash. Further, contaminants peeled off from the membrane surface by backwashing and remaining in the device are likely to be reattached to the membrane surface of the hollow fiber membrane.

Therefore, it is difficult to completely remove the contaminants attached to the membrane simply by flowing the backwash fluid accumulated in the backwash tank 133 in the direction opposite to the permeation direction of the membrane.

Then, when the filtration device is restarted in this state, the remaining pollutants start to recirculate in the circulation path and accelerate the clogging of the membrane surface.

Therefore, in order to more completely remove contaminants by the conventional backwashing method, it is necessary to increase the number of times of backwashing and increase the amount of backwashing fluid to be flown during backwashing.

This increases the operation cost of backwashing, lowers the operating rate of the apparatus, and increases the amount of waste liquid generated during backwashing, which is an improvement from the viewpoint of resource saving and environmental protection. Was a problem that needed.

The present invention has been made to solve the above-mentioned problems of the prior art, and its purpose is to improve the efficiency of backwashing, and to effectively remove the contaminants adhering to the film surface. (EN) Provided are a filter device and a method for cleaning a filter device, which are capable of removing the contaminants, preventing the adhered contaminants from reattaching to the membrane, and further reducing the amount of discharged liquid.

[0025]

In order to achieve the above object, in the present invention, a circulation path, a membrane-utilizing type filtration means provided in the circulation route, and a membrane-utilizing type filtration means are provided. In a filtration device equipped with a backwash means for reversing the permeation direction of the membrane, during backwashing, circulating the fluid in the circulation path while maintaining a high pressure state on the permeate side of the membrane by the backwash means. Is characterized by.

Therefore, when the backwashing means is activated, the contaminants adhering to the surface of the membrane are removed from the surface of the membrane by the high pressure state on the permeate side of the membrane and the backwashing fluid circulating during the backwashing. The removed contaminants are mixed in the backwash fluid and circulate in the circulation path, but since the permeate side is kept in a high pressure state and filtration is not possible, the amount of contaminants redeposited on the surface of the membrane is reduced.

An independent bypass path connecting the inflow path and the outflow path of the fluid to be filtered of the membrane-utilizing filtration means as the circulation path, a pump for circulating the fluid in the bypass path, and the bypass path in the bypass path. A drain valve for discharging the fluid is provided, and during backwashing, the high pressure state on the permeate side of the membrane is maintained by the backwashing means, the fluid is circulated through the bypass path, and then the fluid can be discharged from the drain valve. It is also preferable that:

According to this, the removed pollutants are mixed in the backwash fluid and circulate through the independent bypass path,
It does not flow to other routes. The backwash fluid containing contaminants is discharged from the discharge valve.

It is also preferable that the bypass path is provided with a filter means for removing contaminants in the circulating fluid.

According to this, since the contaminants mixed therein can be removed while the backwash fluid is circulating, the contaminants can be removed without discharging the backwash fluid.

Further, in the method for cleaning the filtration device, the circulation path, the membrane-utilizing type filtration means provided in the circulation path,
Backwashing means for reversing the permeation direction of the membrane of the membrane-utilizing filtration means, and during backwashing, the fluid in the circulation path is kept in a state of maintaining a high pressure state on the permeate side of the membrane by the backwashing means. Circulate.

Further, an independent bypass path connecting the inflow path and the outflow path of the fluid to be filtered of the membrane-utilizing type filtration means as the circulation path, a pump for circulating the fluid in the bypass path, and the bypass path A discharge valve for discharging the fluid in the inside, and at the time of backwashing, the high pressure state on the permeate side of the membrane is maintained by the backwashing means and the fluid is circulated through the bypass path, and then the fluid is discharged from the discharge valve. It is also suitable to discharge.

Further, in the bypass path of the filtering device,
It is also preferable to provide a filter means for removing contaminants in the circulating fluid so as to remove contaminants in the fluid circulating in the bypass passage during backwashing.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiment.

(Embodiment 1) FIG. 1 shows a first embodiment of a filtration device to which the present invention is applied. This filtering device S1
The present invention is characterized by solving the problem at the time of backwashing the membrane-utilizing type filtration means 1 according to the present invention, and is related to backwashing from the filtering device 100 of FIG. 4 described as an example in the section of the prior art. The constituent parts are excerpted and the structure peculiar to the present invention is added thereto.

Therefore, the structure (not shown) on the left side of the drawing may be the same as that described in the prior art, and is not limited to this structure, and the present invention has various structures. It is applicable to the device.

In FIG. 1, reference numeral 1 denotes a membrane-utilizing type filtration means, which uses a hollow fiber membrane module 1b in which a plurality of hollow fiber membranes 1a are bundled as a filtration membrane.

The membrane-utilizing filtration means 1 is of a cross-flow type having an inflow path 2 and an outflow path 3 for the fluid to be filtered, and the fluid to be filtered always flows through the hollow fiber membrane module 1b during the filtering operation. It flows in parallel with the direction of the hollow fiber membrane 1a. The membrane-permeated liquid that has permeated the hollow fiber membrane 1a flows through the discharge path 4 and is discharged in the direction of arrow A1 for subsequent use.

Reference numeral 5 denotes a backwash tank provided in the middle of the discharge path 4 for temporarily storing a membrane permeate used as a backwash fluid for backwashing the membrane during backwash.

Reference numeral 6 denotes a switching valve that switches between normal filtration and backwashing. Only during backwashing, high pressure air as a compressed gas is made to flow into the backwashing tank 5 in the direction of arrow A4. 5 Reverse flow of the membrane permeation liquid (backwashing fluid) stored inside, and if necessary, high pressure air itself also flows into the permeate side of the hollow fiber membrane module 1b to bring the permeate side into a high pressure state. Is something that can be done.

The discharge path 4, the backwash tank 5, the switching valve 6 and the like constitute a backwash means.

Reference numeral 7 denotes a path switching valve provided in the outflow path 3, which is opened so that the fluid flows to the path 8 during normal filtration and to the path 9 used as a circulation path during backwashing. Replace

Reference numeral 10 is a circulation path for allowing the fluid to be filtered to cross-flow through the membrane-utilizing filtration means 1 at a normal time
The fluid passes through the path 11, the pump 12, and the inflow path 2, and the fluid to be filtered circulates again into the membrane-utilizing type filtration means 1.

Reference numeral 13 is a pressure regulating valve for branching a part of the fluid flowing through the path 8 to a circulation path (not shown) in the direction of arrow A3.

On the other hand, the fluid that has flowed into the path 9 during the backwash also passes through the downstream side of the path 11, the pump 12 and the inflow path 2 and is circulated again into the membrane-utilizing filtration means 1. Also, 1
Reference numeral 4 is a discharge valve for discharging a fluid containing contaminants during backwashing. Further, the circulation path during the backwash is called an independent bypass path K1.

The operation of the filtration device S1 having the above-described structure will be described below from the case of normal filtration. During normal filtration, the fluid to be filtered is from the arrow A2 to the path 11
The membrane permeated liquid, which was transported by the pump 12 and passed through the inflow route 2 into the membrane-utilizing type filtration means 1 in a cross-flow manner, was permeated through the membrane and discharged through the discharge route 4, and did not permeate through the membrane. The fluid flows through the outflow path 3, the path switching valve 7, the path 8
And the circulation route 10 to return to the route 11 again, and the membrane-utilizing filtration means 1 is circulated through this route many times.
And filtered. At this time, a part of the fluid branches in the direction of the arrow A3 and flows, as described above.

Next, a backwashing method using the backwashing means having the above construction will be described as a method for washing the filtering device according to the construction of the present invention. First, during backwashing, the path switching valve 7 is switched to the backwashing side. The pump 12 is preferably stopped once in this state, but it may be continued without being stopped.

Next, the switching valve 6 is switched to the backwash side and the arrow A
The high-pressure air shown in FIG. 4 is caused to flow into the backwash tank 5 and the backwash fluid accumulated in the backwash tank 5 is backflowed from the discharge path 4 to the hollow fiber membrane module 1b.

When the backwashing fluid stored in the backwashing tank 5 is backflowed, the fluid existing in the paths 3, 9 and 2 temporarily becomes excessive. Drain excess fluid. Further, at this time, a check valve may be provided in the path 11 in order to completely prevent the backwashing fluid containing the contaminants from flowing through the path 11 and backflowing to the path 10 or the like.

Here, the switching valve 6 and the discharge valve 14 at the time of backwashing
As the operation method of, several methods can be adopted.

(A) Backwashing is performed all at once until the backwashing fluid in the backwashing tank 5 is completely exhausted, and the discharge valve 14 also has a fluid (backwashing fluid) in the inflow path 2 and the membrane-utilizing type filtration means 1. Keep it open until it is completely discharged. Here, the discharge valve 14 is closed, but the switching valve 6 is left on the backwash side, and the pressure on the permeate side of the membrane is kept high by the high pressure air.

(B) Backwashing is performed while leaving a part of the backwashing fluid in the backwashing tank 5, and the discharge valve 14 is closed there. Route 1
If there is a check valve (not shown) in 1, the switching valve 6 is set to the backwash side to maintain the pressure on the permeate side of the membrane in a high pressure state.

As described above, the operating methods (a), (b) and the like can be adopted, but in the present invention, the pump 12 is further operated from this state, and the backwash fluid is circulated through the circulation path K1.
It is circulated in the membrane-utilizing type filtration means 1 to flow. However, when the valve operation of (a) above is performed, there is no fluid in the path, so the fluid to be filtered is supplied from the arrow A2 and circulated as the backwash fluid.

Then, since the permeate side of the membrane is in a high pressure state, the circulating backwash fluid cannot pass through the membrane and is not filtered, but is discharged by the pollutants separated by the previous backwash. The residual substances and the contaminants newly separated by the circulation are mixedly present in the circulating backwash fluid. Further, since the pressure on the permeate side of the membrane (outer diameter side in the hollow fiber membrane) is high, reattachment of contaminants to the membrane surface does not occur, and the contaminants on the surface are removed by the circulating fluid flow.

When the circulation of the backwashing fluid in the circulation route K1 is completed, the backwashing fluid containing contaminants may be completely discharged from the discharge valve 14.

(Second Embodiment) FIG. 2 shows a second embodiment to which the present invention is applied. The filtering device S2 of the second embodiment is the same as the filtering device S1 described in the first embodiment.
The basic structure is the same, but the path 9 is provided with a filter means 20 for removing contaminants suspended in the fluid.

In FIG. 2, the same components as those in the first embodiment are designated by the same reference numerals and treated as the same as those in the first embodiment, and detailed description thereof will be omitted.

In this embodiment, since the contaminants contained in the backwash fluid are removed by the filter means 20 when the backwash fluid circulates in the circulation path K2 during the backwash, the discharge valve 14 should be opened. Without this, it is possible to carry out backwashing and remove contaminants.

Therefore, the contaminants mixed in the backwashing fluid can be removed while the backwashing fluid is circulating.
Contaminants can be removed without discharging the backwashing fluid, and the amount of waste liquid due to backwashing can be reduced.

(Third Embodiment) FIG. 3 shows a third embodiment to which the present invention is applied. The filtering device S3 of the third embodiment is the filtering device S2 described in the second embodiment.
Although the basic configuration is the same, a path shutoff valve 7b is provided in the path 8 instead of the path switching valve 7 provided in the outflow path 3.

In the filtering device S3, the path shutoff valve 7b is opened during normal filtration, but shuts off the path 8 during backwashing. Other configurations are the same as those in the second embodiment.

However, in the filtering device S3, a part of the circulating fluid also passes through the filter means 20 even during normal filtration, and therefore the clogging of the membrane-utilizing type filtering means 1 is further reduced as compared with the filtering device S2 of the second embodiment. A suppression effect can be expected.

[0063]

As described above, according to the present invention, when backwashing the filtration device, the contaminants adhering to the surface of the membrane are circulated in the backwash fluid even when the backwash fluid is used in a small amount. The backwashing efficiency is improved because it is removed by. Also,
The removed contaminants are mixed in the backwash fluid and circulate in the circulation path, so that the amount of contaminants redeposited on the surface of the film is reduced.

By providing an independent bypass path, backwashing can be performed without the removed contaminants flowing out to other paths. In addition, the backwash fluid containing contaminants is discharged from the discharge valve.

In the case where the bypass means is provided with the filter means, the contaminants mixed therein can be removed while the backwash fluid is circulating, so that the contaminants can be removed without discharging the backwash fluid. It can be removed and the amount of waste liquid due to backwashing can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram of a filtration device according to a first embodiment of the present invention.

FIG. 2 is a diagram of a filtration device according to a second embodiment of the present invention.

FIG. 3 is a diagram of a filtration device according to a third embodiment of the present invention.

FIG. 4 is a diagram of a conventional filtration device.

FIG. 5 is an explanatory diagram of floating oil recovery means.

[Explanation of symbols]

 1 Membrane Utilizing Filtration Means 1a Hollow Fiber Membrane 1b Hollow Fiber Membrane Module 2 Inflow Path 3 Outflow Path 4 Discharge Path 5 Backwash Tank 6 Switching Valve 7 Path Switching Valve 8, 9, 11 Path 10 Circulation Path 12 Pump 13 Pressure Control Valve 14 Discharge valve 20 Filter means A1 Arrow K1 Bypass path S1 Filtration device

Claims (6)

[Claims] 1. A filtration apparatus comprising: a circulation path; a membrane-utilizing filtration means provided in the circulation passage; and a backwashing means for reversing the permeation direction of the membrane of the membrane-utilizing filtration means. A filtration device, wherein the fluid in the circulation path is circulated while maintaining a high pressure state on the permeate side of the membrane by the backwashing means at the time of washing. 2. An independent bypass path connecting an inflow path and an outflow path of a fluid to be filtered of a membrane-utilizing filtration means as the circulation path, a pump for circulating the fluid in the bypass path, and the bypass path. And a discharge valve for discharging the fluid in the inside, and at the time of backwashing, the high pressure state on the permeate side of the membrane is maintained by the backwashing means, and the fluid is circulated through the bypass path,
The filter device according to claim 1, wherein the fluid can be discharged from the discharge valve thereafter. 3. The filter device according to claim 2, wherein the bypass path is provided with a filter means for removing contaminants in the circulating fluid. 4. A method of cleaning a filtration device comprising: a circulation path; a membrane-utilizing filtration means provided in the circulation passage; and a backwashing means for reversing the permeation direction of the membrane of the membrane-utilizing filtration means. A method for cleaning a filtration device, characterized in that the fluid in the circulation path is circulated while maintaining a high pressure state on the permeate side of the membrane by the backwashing means during the backwashing. 5. An independent bypass path that connects an inflow path and an outflow path of a fluid to be filtered of a membrane-utilizing type filtration means as the circulation path, a pump that circulates the fluid in the bypass path, and the bypass path. A method of cleaning a filtration device comprising a discharge valve for discharging the fluid inside, wherein the fluid is circulated through the bypass route while maintaining a high pressure state on the permeate side of the membrane during the backwashing. ,
Thereafter, the fluid is discharged from the discharge valve, and a method for cleaning a filtering device. 6. A bypass means of the filtering device is provided with a filter means for removing contaminants in the circulating fluid, and contaminants in the fluid circulating in the bypass passage are removed during backwashing. The method for cleaning a filtration device according to item 5.