JPH09220452A - Membrane leakage detector and detecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the inexpensive and convenient device and method for rapidly detecting the damage of a membrane when the separation membrane damages and leaks. SOLUTION: A membrane leakage detector provided with a detecting membrane 1 having a larger average pore diameter and a much smaller membrane area than a membrane to be tested for leakage, a branch pipeline 2 for sampling a part of the permeated liq. of the membrane to be tested, a vessel 3 for accumulating the supplied permeated liq. and a sensor 4 for detecting the liq. surface of the vessel is attached. A part of the permeated liq. of the membrane to be tested is introduced into the vessel and then filtered by the detecting membrane, and the liq. leakage is detected by the sensor as the clogging of the detecting membrane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to detection of a membrane leak in a separation membrane module, and more particularly, to an auxiliary device and a detection method for detecting a membrane leak of a stock solution caused by a membrane damage of a separation membrane module during a membrane filtration operation. It is about.

[0002]

2. Description of the Related Art In recent years, surface water and groundwater filtration, seawater desalination, dialysis water purification, hemofiltration, artificial dialysis, pharmaceutical water and semiconductor water purification, fruit juice concentration and clarification, enzyme and cell purification In various fields such as concentration and filtration, human urine and waste liquid filtration, gas separation concentration, liquid degassing, liquid-liquid extraction, and organic solvent recovery, membrane separation utilizing the selective permeability of the membrane is performed. A membrane separation device including a membrane module of a hollow fiber membrane type, a spiral type, a tube type, a plate-and-frame type or the like is usually used for these separations. on the other hand,
In membrane separation, if an accident such as membrane damage occurs, the undiluted solution leaks from the membrane supply side and flows into the permeate side without treatment. In such a case, if a phenomenon such as turbidity of the permeated liquid can be confirmed with the naked eye, swift action can be taken, so that the contamination with the untreated undiluted liquid can be minimized.
However, if the amount of leakage is small, the discovery is likely to be delayed, and the contamination on the permeate side proceeds, affecting the treated water.

Therefore, it has been proposed to promptly detect troubles due to leakage and control the operation of the device as the entire membrane separation device or the membrane module. For example, JP-A-6-15271, JP-A-6-182164, JP-A-7-47236 and JP-A-6-34.
In Japanese Patent No. 730, the permeate of a membrane module that controls separation is further filtered by a membrane module having a membrane with a larger pore size that is provided in a subsequent stage, and if a membrane module that controls separation causes leakage, Since clogging and a differential pressure of the membrane occur, a method of detecting the leak of the membrane by detecting the differential pressure has been proposed. Also, the actual Kaihei 6-21
In Japanese Patent No. 728, it is proposed to detect the membrane leakage by detecting the permeation flux of the latter membrane. Further, in Japanese Patent Laid-Open No. 6-170365, a method of detecting turbidity and fine particles of a permeated liquid by a sensor is also used. Further, Japanese Patent Application Laid-Open No. 7-248290 proposes a leak detector in which a part of permeated water is diverted by a sampling pump and passed through a leak detection filter to detect a pressure rise at a filter inlet with a pressure gauge.

However, all of these have the drawbacks that the equipment cost is high because they require large-scale equipment and are detected by an expensive sensor.

[0005]

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to propose an apparatus and method for promptly detecting the damage of a membrane even if the separation membrane is damaged and leaks. Another object of the present invention is to provide a low-cost, general-purpose detecting device and a simple detecting method.

[0006]

As a result of various studies, the inventor of the present invention detects a container for accumulating a part of permeate through a branch pipe from the permeate side of a membrane module that controls separation, and a liquid level state of the container. It has been found that the above object can be achieved by providing a sensor and a membrane for filtering permeated liquid introduced from this container, and completed the present invention.

That is, the membrane leakage detection device of the present invention collects a part of the permeated liquid of the detection membrane and the target separation membrane having a pore size larger than the target separation membrane whose membrane leak is to be detected and a far smaller membrane area. It has a branch pipe, a container for accumulating the collected permeated liquid, and a sensor for detecting the liquid surface state of this container. Further, the average pore diameter of the detection membrane is 2 to 10000 times the average pore diameter of the target separation membrane, and one membrane leak detection device is attached per unit of the target separation membrane module.

In the membrane leak detection method of the present invention, a part of the permeate of the separation membrane to be subjected to membrane leak detection is collected by a branch pipe and introduced into a container having a sensor for detecting the liquid level state, In this method, a sensor membrane having an average pore size larger than the target separation membrane and a membrane area much smaller than the target membrane is used for filtration, and membrane leakage is detected by the sensor as a clogging phenomenon of the membrane. Further, the average pore size of the detection membrane is 2 to 10000 times the average pore size of the target separation membrane, and the flux of the permeated liquid received by the container in the state where the target separation membrane does not leak is the filtration of the detection membrane. This is a membrane leak detection method in which the flux is smaller than the flux.

The membrane leak detection device of the present invention is attached and used separately from the original main series of membrane separation equipment. The detection mechanism will be described below.

First, a part of the permeated liquid of the target separation membrane is collected by a branch pipe and continuously or periodically received in a container, from which the permeated liquid is flowed to the detection membrane and filtered by the detection membrane. Usually, a valve or the like is provided in the middle of the branch pipe for shutting off the liquid or adjusting the flux. When the target separation membrane does not leak, the average pore size of the detection membrane is larger than that of the target separation membrane, so that the detection membrane is not clogged and the permeation flux is constant.
However, when the target separation membrane is damaged and the stock solution leaks to the permeate side of the membrane, the sensing membrane is clogged, and the permeation flux of the sensing membrane is reduced. When the liquid flux passing through the detection membrane becomes smaller than the liquid flux received in the container, the liquid level of the container rises, so the film leaks due to the sensor that detects the liquid level condition.
Therefore, the breakage of the membrane can be detected.

The liquid flux received by the container may be any,
The present invention is characterized in that even a small amount can be sufficiently applied to the present invention. For example, an extremely small amount of about several ml / minute may be used. In this case, the detection film and container used can be made small. For example, the sensing film to be used may be several cm ² . This is a very small membrane separation device, for example, a membrane area of 0.2 m ^{2 of a} hollow fiber membrane water purifier used by being attached to a tap water tap.
The value is much smaller than that of the sample of 2,000 cm ² . Further, it is sufficient for the container to have several ml to several tens of ml.

The liquid flux received by the container must be equal to or slower than the filtration flux of the detection membrane in the state where the target separation membrane is not leaking, and the slower is more preferable. The degree of slowness needs to be appropriately determined in consideration of variations in the liquid flux received by the container due to pressure fluctuations and reduction in the filtration flux of the detection membrane due to contamination of dissolved organic substances.

In the present invention, the average pore size means the average size corresponding to the size of the permeation component. For example, in the case of a microfiltration membrane, the size of the permeation component can be represented by the average pore size. On the other hand, for example, in an ultrafiltration membrane or a reverse osmosis membrane, it is difficult to measure the pore size. Therefore, specifically, in the case of an ultrafiltration membrane, the size of the permeation component is usually represented by a molecular weight cutoff, and In the case of a reverse osmosis membrane, it is usually represented by the salt elimination rate (salt removal rate). Therefore, in the present invention, for example, the term "average pore size" is used for convenience, including expressions representing the size of the permeation component, such as the molecular weight cutoff in the ultrafiltration membrane and the salt exclusion rate in the reverse osmosis membrane. Incidentally, the pore size of the microfiltration membrane is 0.08 to 2.5 μm (molecular weight cutoff of 15
50,000 to 5,000,000), and the pore size of the ultrafiltration membrane is 0.002 to 0.4 μm (molecular weight cutoff of 500 to 80).
10,000), and the pore size of the loose reverse osmosis membrane is 0.0007-
0.007 μm (molecular weight cutoff 140 to 15,000) and pore size (theoretical) of the reverse osmosis membrane are 0 to 0.0015 μm.
It is said to be in the range of m (molecular weight cutoff of 0 to 300).

The average pore diameter of the detection membrane used in the present invention needs to be larger than the average pore diameter of the target separation membrane, and may be 2 to 10,000 times the average pore diameter of the target separation membrane. Furthermore, it is more preferable and practical if it is about 10 to 1000 times the average pore size of the target separation membrane. Further, the material of the detection film may be any material. For example, cellulose acetate, polyamide, polycarbonate, polysulfone,
Examples thereof include polyether sulfone, polyolefin, acrylic resin, fluorine group-containing resin, ceramic and metal. Further, the detection membrane may have any shape, and examples thereof include a flat membrane, a hollow fiber membrane, a tube membrane, and a spiral membrane. When the membrane area may be small, a flat membrane may be simple.

Further, the sensor for detecting the liquid surface state used in the present invention may be any of those commonly used as long as it can detect the liquid, for example, a sensor for measuring resistance with an electrode. , Which measures the refractive index, optical detection or capacitance method may be used. As a detection method, a sensor may be projected from the wall of the container to detect the liquid level, or a hole may be opened in the wall of the container to attach a pipe, etc., and the overflowed liquid may be taken out inside the pipe or separately. Then, it may be detected by the sensor.

Any container may be used in the present invention. It can be said that the container for the detection film is also a container,
Further, for example, the pipe may be used as it is, or a cylindrical plastic container may be used.

In the present invention, the permeated liquid may be introduced from the container to the detection membrane by any method, but in consideration of practicality and cost, a microfiltration membrane is used as the detection membrane,
It is recommended to introduce it only by piping. In this case, the pressure for filtering the detection film is only the head pressure of the liquid accumulated inside the pipe, but it can be sufficiently filtered.

The liquid filtered by the detection membrane may be put into the permeated liquid tank of the target separation membrane or returned to the stock solution tank. It may also be drained as a drain. Considering the advantages of the device of the present invention, since the filtration flux at the sensing membrane is small, any of the above methods may be used, but draining is cost effective.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing an example of the structure of the membrane leak detection device of the present invention, in which a flat membrane detection membrane is installed at the bottom of a container having a liquid level detection sensor inside. Here is an example. The apparatus shown in the figure has a branch pipe (2) for collecting the permeated liquid from the target separation membrane, a container (3) for receiving the permeated liquid, an air vent (5) of the container, and a liquid level detection sensor (4) attached to the container. And a flat sensing film (1).
The permeated liquid collected from the target separation membrane by the branch pipe (2) first enters the container (3) and is filtered by the detection membrane (1) by the head pressure. The liquid level of the permeate is in equilibrium inside the container (3). When the target separation membrane is damaged and a membrane leak occurs, the surface of the sensing membrane is covered with suspended matter due to the leak, and the flux is reduced. Since the velocity (fluid flux) of the permeate flowing into the container does not change, the liquid level of the permeate in the container rises and is detected by the liquid level detection sensor (4).

FIG. 2 is a cross-sectional view showing another example of the structure of the membrane leak detection device of the present invention, in which the liquid level detection sensor is
It is installed to detect the overflow liquid from the upper part of the container. In this figure, a container (3) that receives the permeated liquid from the target separation membrane, an overflow pipe (6) from the side of the container, a leak detection sensor (4), a flat membrane detection membrane (1) and a container and detection. It consists of piping (7) connecting the membranes. Similar to FIG. 1, the liquid level of the permeated liquid from the target separation membrane is in equilibrium inside the container (3). When the target separation membrane leaks, the liquid level of the permeated liquid in the container rises, passes through the overflow pipe (6), and is detected by the leak detection sensor (4).

FIG. 3 is a conceptual diagram showing an example in which the membrane leak detection device (8) according to the present invention of FIG. 1 or 2 is attached to the permeate pipe (10) of the target separation membrane module. The flux of the permeated liquid collected is regulated by a flow regulating valve (11). Further, the automatic valve (12) shuts off the liquid when the target separation membrane module is in an unsteady operation (for example, during backwashing). When a membrane leak is detected, it is detected by the liquid level detection sensor (4), and a signal can be transmitted to the original membrane separation equipment to control the operation.

FIG. 4 is a conceptual diagram showing an example in which the membrane leak detection device (8) according to the present invention is directly attached to the target separation membrane module similarly to FIG. The flow rate of the permeate can be adjusted by the constant flow valve (13).

In FIGS. 3 and 4, the combination of the flow rate adjusting valve (11) and the automatic valve (12) and the constant flow rate valve (13) have the same operation, so either one may be used.

[0025]

EXAMPLES The present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples.

Example 1 (Production Example of Membrane Leak Detection Device) The membrane leakage detection device shown in FIG. 1 was produced. A sensor of a water leakage detector (61F-WLA type manufactured by OMRON) is attached to the upper part of a container that receives a permeated liquid having an inner diameter of 20 mm and a height of 300 mm, and an average pore diameter of 1 μm is used as a detection film on the lower part of the container.
A cellulose-based membrane filter having a membrane diameter of 12 mm (membrane area 1.1 cm ² ) (a micro filter manufactured by Fuji Photo Film Co., FR-100) was attached. The height from the detection film to the leak detection sensor was 250 mm. Also, an air vent hole was provided at a position higher than the sensor on the side of the container.

Example 2 Hollow fiber membrane module A (manufactured by Daisen Membrane Systems, FF03-FL-FUS1) as a target separation membrane
041, membrane area 2.3 m ² , cut-off molecular weight 100,000, average pore size 0.01 μm) were used. Using industrial water as raw water,
A total volume filtration operation was performed at a permeation rate of 0.2 m ³ / hour.
From the permeate pipe of the hollow fiber membrane module A, 600 ml /
At a speed of time, a part of the permeated liquid was collected through a branch pipe and introduced into a membrane leak detection device. I ran for 12 hours, but there was nothing abnormal. During this time, the liquid level of the permeated liquid inside the container of the membrane leak detection device was in equilibrium at a height of about 15 cm of the detection membrane.
After that, several hollow fibers of the hollow fiber membrane module A were cut,
A membrane leak was created. When this hollow fiber membrane module A was attached and operated in the same manner, about 20 minutes from the start of operation,
Membrane leakage could be detected.

Example 3 Hollow fiber membrane module B (manufactured by Daisen Membrane Systems, FE10-FC-FUC1) as a target separation membrane
581, membrane area 5 m ² , fraction molecular weight 150,000).
Industrial water was used as raw water, and operation was performed at a permeation rate of 0.3 m ³ / hour. A part of the permeated liquid was sampled from the permeated liquid pipe of the hollow fiber membrane module A at a rate of 480 ml / hour through a branch pipe, introduced into a membrane leak detection device, and operated for 12 hours, but there was no abnormality. After that, several hollow fibers of the hollow fiber membrane module B were cut to cause membrane leakage. When this hollow fiber membrane module B was attached and operated in the same manner, it was possible to detect a membrane leak in about 30 minutes from the start of operation.

[0029]

Since the membrane leak detection device and the detection method of the present invention are simple and simple methods, the membrane equipment incorporating this device is advantageous in terms of cost. Further, since it is a compact and inexpensive device, it can be attached to each membrane module, and the reliability of membrane leak detection is high. Further, by interlocking the signal detected by the membrane leak detection device and the detection method of the present invention with the original membrane separation equipment, it is possible to control the operation of the membrane separation equipment at the time of membrane leak detection. is there.

Further, the membrane leak detection device and the detection method of the present invention can be applied to a module for any application.
Examples include hollow fiber membrane modules, tubular membrane modules, plate and frame modules, spiral modules, flat membrane modules, and the like. Further, the applicable application may be any field. For example, the application to a water purification system as a new technology replacing the conventional method of passing through a coagulation-precipitation-sand filtration-chlorine sterilization step, and in the food field, coffee, tea, juice concentration or clarification of juice. In the field of biotechnology, enzymes, and pharmaceuticals, production of aseptic pyrogen-free purified water and the like, and in the field of electronics industry, reuse of wafer polishing wastewater and the like can be mentioned.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a membrane leakage detection device of the present invention.

FIG. 2 is a schematic cross-sectional view showing another example of the membrane leakage detection device of the present invention.

FIG. 3 is a conceptual diagram showing an example in which the membrane leak detection device of the present invention is attached to a permeate pipe of a target separation membrane module.

FIG. 4 is a conceptual diagram showing an example in which the membrane leak detection device of the present invention is directly attached to a target separation membrane module.

[Explanation of symbols]

 1 Detection Membrane 2 Branch Piping 3 Container 4 Sensor 5 Air Venting 6 Overflow Piping 7 Piping 8 Membrane Leak Detection Device 9 Target Separation Membrane Module 10 Permeate Liquid Piping 11 Flow Control Valve 12 Automatic Valve 13 Constant Flow Valve

Claims (6)

[Claims] 1. A detection membrane having a larger average pore size and a much smaller membrane area than the target separation membrane for which membrane leakage is to be detected, a branch pipe for collecting a part of the permeate of the separation membrane, and collecting the collected permeate. A film leakage detection device, comprising: a container that operates and a sensor that detects a liquid surface state of the container. 2. The membrane leak detection device according to claim 1, wherein the average pore diameter of the detection membrane is 2 to 10000 times the average pore diameter of the target separation membrane. 3. The membrane leakage detection device according to claim 1, wherein one membrane leakage detection device is attached per target separation membrane module unit. 4. A part of the permeated liquid of a target separation membrane for which membrane leakage is to be detected is collected by a branch pipe and introduced into a container having a sensor for detecting a liquid level condition, and then the average pore diameter is far larger than that of the separation membrane. A method for detecting a membrane leak, which comprises filtering the membrane with a membrane having a small membrane area and detecting membrane leakage by the liquid sensor as a clogging phenomenon of the membrane. 5. The method for detecting a membrane leak according to claim 4, wherein the average pore diameter of the detection membrane is 2 to 10000 times the average pore diameter of the target separation membrane. 6. The membrane leak detection according to claim 4 or 5, wherein the flux of the permeated liquid received by the container when the target separation membrane is not leaking is smaller than the filtration flux of the detection membrane. Method.