JP2011020047A - Method and apparatus for detecting membrane defect, and membrane module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for efficiently detecting membrane defect quickly with a high sensitivity and high accuracy, even during operation of a filter apparatus, and a membrane module suitably used therefor. <P>SOLUTION: The method for detecting the defect of a membrane set in the membrane module, includes a process of continuously measuring the potential between a standard electrode set at a liquid feed port side of the membrane module and a reference electrode set at a liquid outflow port side from the standard electrode when running liquid into the membrane module, and detecting the defect of the membrane by measuring the variation of the potential. An amplifying means amplifying the potential is set near the standard electrode, being nearer the standard electrode side than the reference electrode, and the potential variation is measured in this state. The apparatus for detecting membrane defect applicable to the method for detecting the defect of the membrane and the membrane module are also provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a membrane defect detection method and a membrane defect detection device for detecting defects in a separation membrane in water treatment using a separation membrane such as an ultrafiltration membrane (UF membrane) or a microfiltration membrane (MF membrane), and these The present invention relates to a membrane module to be used in the process.

  In the production of purified water, ultrapure water, pyrogen-free water, etc., many UF membrane modules and MF membrane modules are used for the purpose of final particle removal, sterilization, and pyrogen removal. The occurrence of membrane defects in these membrane modules is monitored by measuring the quality of the produced water or aqueous solution (for example, the number of fine particles, turbidity, or the number of bacteria).

  In such a fresh water generator (fresh water system), several to ten or more membrane modules are used per unit, and a plurality of such units are also used depending on the amount of processing. In addition, the equipment for monitoring the water quality is not measured in each module but in terms of its cost and the like, and is collected and measured from the collected filtrate pipe. Therefore, for example, in a large number of hollow fiber membrane modules, when there are few defects in the membrane module such as cutting of one fiber, it is difficult to detect. Actually, a method of detecting air bubbles by pressurizing with air or the like while the apparatus is stopped is used. However, this method cannot detect when the apparatus is in operation, and cannot detect it immediately when a defect occurs.

  Under such circumstances, the present applicant has proposed a membrane defect detection method capable of quickly and efficiently detecting defects generated in the separation membrane even during operation of the apparatus (see, for example, Patent Document 1). However, in this method, since the potential may be weak, it is necessary to further improve the detection sensitivity.

JP 2007-263944 A

  In view of the above, an object of the present invention is to provide a film defect detection method and a film defect detection apparatus that can detect a film defect quickly, with high sensitivity, and with high precision and efficiency even during operation of the filtration apparatus. . Moreover, an object of this invention is to provide the membrane module which can be used conveniently for these.

As a result of intensive studies to solve the above problems, the present inventors have found that the potential of the potential can be reduced by providing an amplifying means for amplifying the potential in a predetermined position in addition to a method for detecting the presence or absence of a film defect based on a variation in the potential. It has been found that fluctuations can be detected more quickly and with high sensitivity and with high accuracy.
That is, the present invention is as follows.

[1] A membrane defect detection method for detecting a defect in a membrane provided in a membrane module, wherein a reference electrode provided on a liquid supply port side of the membrane module when liquid is caused to flow in the membrane module; A film defect detection step of continuously measuring a potential between a reference electrode provided on the liquid outlet side of the reference electrode and detecting a defect of the film by measuring a change in the potential. A film defect detection method for measuring fluctuations in the potential in a state where an amplifying means for amplifying the potential is provided on the reference electrode side and in the vicinity of the reference electrode with respect to the reference electrode.
[2] The film defect according to [1], wherein the amplification means is provided within a radius of 2 / 5D from the reference electrode, where D is the shortest distance between the reference electrode and the reference electrode along the membrane module. Detection method.
[3] The film defect detection method according to [2], wherein the reference electrode and the amplification unit are incorporated in the same member.
[4] The film defect detection method according to [1] or [2], wherein there are a plurality of the film modules.
[5] The film defect detection method according to any one of [1] to [4], wherein presence of a defect in the film is detected when the potential becomes 1 mV or more.
[6] The membrane defect detection method according to any one of [1] to [5], wherein the membrane is one of an ultrafiltration membrane and a microfiltration membrane.

[7] A membrane module including a membrane, a reference electrode provided on the liquid supply port (liquid outlet) side of the membrane module, a reference electrode provided on the liquid outlet side of the membrane module, Amplifying means for amplifying the potentials of the reference electrode and the reference electrode; and measuring means for continuously measuring a potential difference between the amplified potentials, the amplifying means being closer to the reference electrode than the reference electrode A filtering device provided in the vicinity of the reference electrode.
[8] The filtration device according to [7], wherein the membrane is one of an ultrafiltration membrane and a microfiltration membrane.

[9] A membrane, a reference electrode provided on the liquid supply port side, a reference electrode provided on the liquid outlet side, and an amplifying means for amplifying the potential of the reference electrode and the reference electrode, A membrane module in which the amplifying means and the reference electrode are integrated or close together.

  According to the present invention, it is possible to provide a film defect detection method and a film defect detection apparatus that can detect a film defect quickly, with high sensitivity, and with high precision and efficiency even during operation of the filtration device. Moreover, according to this invention, the membrane module which can be used conveniently for these can be provided.

It is explanatory drawing which shows one form of the filtration apparatus of this invention. It is explanatory drawing which shows one form of the membrane module of this invention, (A) shows the membrane module of an internal pressure filtration system (cross flow system), and (B) shows the membrane module of an external pressure type dead end filtration system. It is a perspective view which shows one form of the piping adapter applicable to the membrane module of this invention. It is a fragmentary sectional view explaining one form of a piping adapter. The upper diagram shows the relationship between time and potential, and the lower diagram shows the relationship between time and pressure.

[Membrane defect detection method and filtration device]
According to the membrane defect detection method of the present invention, when a liquid is caused to flow into the membrane module, the reference electrode provided on the liquid supply port (supply port to which the liquid is supplied) side of the membrane module, Measures the potential difference with the reference electrode provided on the outlet (liquid outlet) side continuously, and detects defects (cracks, pinholes, etc.) of the film by measuring the fluctuation of the potential difference (film Defect detection step).

  Here, the potential of the electrode before the defect is generated is, for example, a streaming potential generated when water permeates through the pores of the UF membrane, and is represented by the following formula (1).

V / P = (ε ₀ ε _r ζ) / (ηκ) (1)
In the above formula (1), V is the flow potential (flow potential generated by the water that permeates through the hollow fiber membrane), P is the transmembrane pressure difference, ε ₀ and ε _r are the dielectric constants of vacuum and water, ζ Is the zeta potential, η is the viscosity of water, and κ is the electrical conductivity of water.

  Since the streaming potential changes depending on the pressure, water temperature, and electrical conductivity applied to the membrane, it is necessary to measure the pressure, flow rate, temperature, and electrical conductivity at the same time as measuring the potential, and correct the influence. However, even if corrections are made in consideration of these influences, if a change in potential is recognized, it can be determined that a defect has occurred in the film.

  The membrane potential generates potential on both sides of the membrane by the interaction with the electric double layer on the surface of the membrane when water flows through the pores of the membrane. If there is a defect in the membrane, such as a pinhole or hollow fiber cut, this potential will fluctuate. If this is detected by an electrode installed in the membrane module, it can be detected instantaneously when a defect occurs.

  In the film defect detection method of the present invention, it is preferable to detect the presence of a film defect when the absolute value of the potential difference between the reference electrode potential and the reference electrode potential is 1 mV or more. Even in a normal state, the potential difference may slightly fluctuate due to some external influence. However, even if it fluctuates greatly, the absolute value of the fluctuation value does not exceed 1 mV. On the other hand, when a defect occurs in the membrane, the supply liquid side and the permeate side are directly connected, and the flow velocity fluctuates greatly. Therefore, the absolute value of the fluctuation value is 1 mV or more. Therefore, it is practical and very efficient to detect a film defect based on this value.

  In addition, the potential difference may not be stable in the initial stage of the membrane treatment operation. In that case, it is preferable to wait until the absolute value of the potential difference becomes less than 1 mV, and then continuously perform potential difference measurement for detecting a film defect. The term “continuous” as used herein means that the potential difference measurement is continuously performed during the membrane processing operation.

In the present invention, the amplifying means for amplifying the potential is provided on the side closer to the reference electrode than the reference electrode and in the vicinity of the reference electrode. By providing it on the reference electrode side and in the vicinity of the reference electrode, the potential of each electrode can be detected with high sensitivity. On the other hand, if it is on the reference electrode side and not in the vicinity of the reference electrode, it may be difficult to detect a highly sensitive potential.
Here, “on the reference electrode side and in the vicinity of the reference electrode” means that the shortest distance between the reference electrode and the reference electrode along the membrane module is D within a range of radius 2 / 5D from the reference electrode. , Preferably within a radius of 1 / 3D, more preferably within a radius of 1 / 8D. As a most preferable aspect, a state in which the reference electrode and the amplifying means are incorporated in the same member (the same pipe as described later) can be cited.

  As described above, the effect of providing the amplification means “on the reference electrode side and in the vicinity of the reference electrode” is also apparent from the following experimental example. That is, as shown in Table 1 below, when the amplifying means (amplifier) is provided at a position far away from the reference electrode (comparative experimental example), the fluctuation range of noise increases, but in the vicinity of the reference electrode (experimental example). ), The fluctuation range of noise can be made extremely small. As a result, the potential of each electrode can be detected with high sensitivity.

  In addition, a conventionally well-known thing can be used about a reference | standard electrode, a reference electrode, and an amplification means (amplifier). Examples of the reference electrode include stainless steel and titanium bars and plates, and examples of the reference electrode include stainless steel and titanium bars and plates. As the amplifying means, one having a high input impedance is preferable in order to efficiently measure a low potential.

  In the present invention, since the occurrence of a membrane defect is detected by measuring the change in membrane potential caused by the permeable membrane, it is possible to continuously monitor the performance of the separation membrane. In addition, the detector can use electrodes that are inexpensive and have a simple structure, and a plurality of electrodes can be installed in each module. Accordingly, it is most suitable for a membrane separation unit using a plurality of membrane modules and a large capacity apparatus using a plurality of membrane separation units.

  The potential of the electrodes installed in each module is measured or collected and stored in a short period of time by measuring or collecting the potential or potential difference by scanning a plurality of electrodes simultaneously with a microprocessor-controlled potential detector. Removal or correction of pressure, temperature, flow rate, etc. is performed to determine whether there is an abnormality. If an automatic valve for shutting off the flow path is installed in each membrane module, when an abnormality is detected in one membrane module among many modules of the membrane filtration device, the operation of the entire device is not stopped. Only the module can be separated from the main piping or filtered water piping by an automatic valve or the like to maintain the filtered water quality. In addition, if a defective membrane module can be identified without installing an automatic valve, the module can be manually detached in a short time.

  In order to carry out the film defect detection method of the present invention as described above, the filtration device of the present invention can be applied. The filtration device includes a membrane module including a membrane, a reference electrode provided on the liquid supply port side of the membrane module, a reference electrode provided on the liquid outlet side of the membrane module, and potentials of the reference electrode and the reference electrode And a measuring means for continuously measuring each amplified potential (or a potential difference obtained from the potential). The amplification means is provided on the side of the reference electrode with respect to the reference electrode and in the vicinity of the reference electrode.

FIG. 1 shows an example of the filtration device.
In the said filtration apparatus, first, the water (or aqueous solution) supplied from the raw | natural water line 10 is filtered through membrane module 12A, 12B, 12C which is a filtration means. The filtered water gathers and flows out in the filtered water line 16 via the automatic valves 14A, 14B, and 14C installed in each membrane module, and the unfiltered water flows out to the circulating water line 18.

  The reference electrodes 20A, 20B, and 20C provided in the membrane modules 12A, 12B, and 12C are installed on the liquid supply port side (raw water line 10 side) of each membrane module, and the reference electrodes 22A, 22B, and 22C are on the liquid outlet side (filtering) It is installed on the water line 16 side). The potential between the two electrodes of the reference electrode and the reference electrode is amplified by amplifiers (AMP) 24A, 24B, and 24C, and input to the microprocessor 28 sequentially or in parallel via the A / D converter 26. The input data is recorded, calculated and compared by the microprocessor 28. As a result, when an abnormality is detected (for example, when the potential difference becomes 1 mV or more), an alarm is issued by the alarm device 30, and the automatic valve of the filtrate attached to the corresponding membrane module is closed to contaminate water ( Mixing of (untreated water) is prevented.

[Membrane module]
The membrane module of the present invention comprises a membrane, a reference electrode provided on the liquid supply port side, a reference electrode provided on the liquid outlet side, and an amplifying means for amplifying the potential of the reference electrode and the reference electrode. The amplifying means and the reference electrode are integrated or close to each other.

  Specifically, as shown in FIG. 2A, the membrane module 12 includes a large number of hollow fiber membranes (not shown) inside the housing case 30. The ends of the hollow fiber membrane are sealed at both ends of the housing case 30 by a sealing member with the ends opened.

This membrane module 12 can employ, for example, an internal pressure filtration system that filters from the inside to the outside of the hollow fiber membrane, and hollows out water for treatment in the direction of arrow X from one open end (liquid supply port) 32A. It flows into the inner diameter flow path of the thread membrane. Water that has permeated through the hollow fiber membrane flows out of the membrane module 12 from the inside of the housing case 30 through the outlets 34A and 34B. Excess water flows out from the open end 32B.
In the case of FIG. 2 (A), although two outlets are provided, this may be one or three or more and is not particularly limited.

In the membrane module 12, a reference electrode 20D is provided in a pipe having an open end 32A, and detection electrodes 22D and 22E are provided in pipes of outlets 34A and 34B on the permeate side.
Note that a plurality of reference electrodes may be provided as illustrated in FIG. 2A, but at least one reference electrode may be provided, and the number is set as appropriate.

  The membrane module 12 is provided with amplification means for amplifying the potentials of the reference electrode and the reference electrode (not shown in FIG. 2A). The amplification means is integrated with or close to the reference electrode. It is necessary to be provided. By adopting such an aspect, it becomes easy to amplify the potential from the reference electrode, and the potential can be measured efficiently.

  As another configuration of the membrane module of the present invention, an external pressure type dead-end filtration system such as the membrane module 13 can be cited as shown in FIG. The external pressure type dead end filtration method is suitable for a large-sized filtration device (filtration system). In the case of the membrane module 13, processing water or the like is caused to flow from one open end (liquid supply port) 34 </ b> B in the direction of arrow X into the inner diameter flow path of the hollow fiber membrane. Water that has permeated through the hollow fiber membrane flows out of the membrane module 13 from the inside of the housing case 30 through the outlet 32B.

The reference electrode 22F is provided in the pipe having the open end 34A, and the detection electrode 22G is provided in the pipe of the outflow port 32B on the permeate side. The membrane module 13 is also provided with amplification means for amplifying the potentials of the reference electrode and the reference electrode so as to be integrated with or close to the reference electrode. Even in such an embodiment, it is easy to amplify the potential from the reference electrode, and the potential can be measured efficiently.
In FIG. 2B, other configurations are the same as those of the membrane module 12.

  In order to be integrated with or close to the reference electrode, these may be provided in the same region. For example, as shown in FIG. 3, it is preferable that an accommodation box 42 that accommodates a reference electrode and an amplifier that is an amplifying unit is provided on a side surface of a pipe adapter 40 provided at a liquid supply port. As shown in FIG. 4, the reference electrode 20 </ b> D is provided so as to be exposed on the inner surface side of the pipe adapter 40, and is connected to an amplifier 24 </ b> D provided on the outer surface side of the pipe adapter 40 through wiring. The wiring L extending from the amplifier 24D is connected to the microprocessor through A / D conversion or the like.

  When the pipe adapter 40 is made of plastic, as shown in FIG. 4, the reference electrode 20D can be embedded in the side surface of the pipe adapter 40. However, when the pipe adapter 40 is made of stainless steel, the reference electrode 20D is piped. The adapter itself can be an electrode.

  In the present invention (film defect detection method and filtration apparatus) as described above, noise is removed after A / D conversion by the A / D converter 26, or correction processing for correcting a potential variation factor is performed. May be.

  In particular, the potential of the electrode to be measured may vary depending on the operation status of the apparatus (for example, filtration pressure, temperature, flow rate at the inlet of the module, electrical conductivity of water, etc.). In this case, it may be difficult to determine whether the potential fluctuation observed during the measurement is due to the above-described operating condition or due to the occurrence of a defect. Therefore, for the purpose of further improving the measurement accuracy, it is preferable to perform a correction process for correcting the pressure before measuring the potential fluctuation. As an outline of the processing, as shown in the above-described equation (1), the flow potential V is proportional to the transmembrane pressure difference P, but the measured potential is added with the potential generated by the flow inside the hollow fiber. Therefore, the change in potential due to the transmembrane pressure difference is measured in advance, and the change in pressure may be corrected.

  For example, when the membrane module as shown in FIG. 2A is used as the correction processing, it is preferable to perform the correction processing based on the following voltage correction formula.

Here, TMP in the above formula is represented by the following formula.
Where P _in is the pressure (bar) at the liquid supply port of the membrane module, P _out is the pressure (bar) at the liquid outlet of the membrane module, and P _perm is the permeation side of the membrane module. Pressure (bar).

  Further, when a plurality of membrane modules are used in parallel, as shown in FIG. 5, for example, when one fiber of the module 1 is broken, the electrode potential of the module 1 changes, but the electrode potential of the module 2 hardly changes. Although the absolute value of the potential of each module is not the same, abnormalities in the membrane can be detected by continuously monitoring and comparing the potential. Since fluctuations in potential due to external factors (for example, pressure, flow rate, temperature, etc.) are almost the same and about the same for each module, the detection accuracy can be improved together with the correction process using pressure as described above.

10 ... Raw water lines 12A, 12B, 12C ... Membrane module 16 ... Filtrated water lines 20A, 20B, 20C ... Reference electrodes 22A, 22B, 22C ... Reference electrodes 24A, 24B, 24C ...・ Amplifier 26... A / D converter 28... Microprocessor 30.

Claims (9)

A membrane defect detection method for detecting defects in a membrane provided in a membrane module,
When a liquid is flowed into the membrane module, the potential difference between the reference electrode provided on the liquid supply port side of the membrane module and the reference electrode provided on the liquid outlet side of the reference electrode is continuously generated. Including a film defect detection step of detecting defects in the film by measuring fluctuations in the potential difference.
A film defect detection method for measuring fluctuations in the potential difference in a state where an amplifying means for amplifying the potential is provided on the side of the reference electrode from the reference electrode and in the vicinity of the reference electrode.   2. The film defect detection method according to claim 1, wherein the amplifying means is provided within a radius of 2 / 5D from the reference electrode, where D is the shortest distance between the reference electrode and the reference electrode along the film module.   The film defect detection method according to claim 2, wherein the reference electrode and the amplification unit are incorporated in the same member.   The film defect detection method according to claim 1, wherein there are a plurality of the film modules.   The film defect detection method according to claim 1, wherein the presence of a defect in the film is detected when the potential difference is 1 mV or more.   The membrane defect detection method according to claim 1, wherein the membrane is one of an ultrafiltration membrane and a microfiltration membrane. A membrane module with a membrane;
A reference electrode provided on the liquid supply port side of the membrane module;
A reference electrode provided on the liquid outlet side of the membrane module;
Amplifying means for amplifying the potential of the reference electrode and the reference electrode;
Measuring means for continuously measuring the potential difference between the amplified potentials,
A filtering device in which the amplification means is provided on the side of the reference electrode with respect to the reference electrode and in the vicinity of the reference electrode.   The filtration device according to claim 7, wherein the membrane is one of an ultrafiltration membrane and a microfiltration membrane. A membrane, a reference electrode provided on the liquid supply port side, a reference electrode provided on the liquid outlet side, and amplification means for amplifying the potential of the reference electrode and the reference electrode,
A membrane module in which the amplification means and the reference electrode are integrated or close together.

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