KR100965135B1 - Method for detecting damage of filtration membrane with piezoelectric material - Google Patents

Abstract

PURPOSE: A filtration membrane damage sensing method using piezoelectrics is provided to prevent damage whether or not of a filtration membrane is grasped easily by using the piezoelectrics, and to correctly detect damages. CONSTITUTION: A filtration membrane damage sensing method comprises the following steps: preparing a membrane module(110) of a hollow state; measuring fundamental resonant frequency of the membrane module; performing a membrane filtration process by using the membrane module; discharging raw water and processing water after completing the membrane filtration; measuring the resonant frequency of the membrane module; and determining the damages of the membrane module.

Description

Method for detecting damage of filtration membrane with piezoelectric material

The present invention relates to a filter membrane damage detection method using a piezoelectric body, and more particularly, to a filter membrane damage detection method using a piezoelectric body that can easily identify whether a filter membrane is damaged by using a piezoelectric body and improve the accuracy of damage detection. It is about.

Due to the serious pollution of the water supply, there is an increasing interest in the quality of purified water and the demand for advanced water treatment is increasing. Accordingly, attempts have been made to supplement existing water treatment facilities or to introduce new filtration devices and filtration processes. However, in order to supplement existing water purification facilities or to introduce new advanced water purification treatment facilities, various difficulties such as site securing and cost are involved. Recently, a high water purification process using membrane filtration that is easy to operate and maintain as well as stable water quality has been proposed.

Membrane filtration water treatment method is a method for separating contaminants in raw water by using a membrane (membrane) having a selective permeation function, there is an advantage that can be reliably removed the suspended substances of a predetermined size or more contained in the raw water. On the other hand, the adhesion layer due to contaminants or solids may be formed on the surface of the filtration membrane, which may reduce membrane filtration performance. Membrane filtration performance can be restored by washing the filtration membranes.

In order to prevent such degradation of membrane filtration, it is important to immediately detect and cope with membrane filtration damage. Looking at the filter membrane damage detection technology in the membrane filtration process in the prior art as follows.

According to a paper published in the Journal of AWWA, Desalination, Membrane Science, a method of detecting air damage in a filtration membrane is disclosed. The method of injecting air into the primary side under the condition that the primary side and the secondary side are gas and liquid is disclosed. Japanese Patent Laid-Open No. 2001-7011098 and Japanese Patent Laid-Open Nos. 2000-342936, 2001-269551, and 2007-245060 disclose the primary side and secondary side of a membrane module made of hollow fibers with gas and liquid to maintain the primary side. Or the technique which detects the damage of a filtration membrane by applying the method of injecting air to a secondary side is disclosed.

However, the above papers and prior patents detect damage of the filtration membrane under the condition that the primary side and the secondary side of the membrane module are applied in a gas-liquid or liquid-gas state. Under these conditions, the pressurized air moves from the gas state to the liquid state due to the pressure difference, and resistance due to density and partial pressure of air is generated, so that the rate of change in air pressure is not large, and thus, even if the filter membrane is damaged, the air pressure changes. Because of their small size, it is difficult to accurately determine the filter membrane damage. In addition, as the membrane filtration proceeds, there is a problem that the measurement sensitivity decreases as the total filtration resistance value increases.

As a solution to the shortcomings of the prior art, a technique of maximizing the change rate of air pressure by maintaining both the primary side and the secondary side in a gas state has been proposed, but this technique is also based on the rate of change of air pressure as in the related arts. As a result of determining the membrane filtration damage, there is a disadvantage in that the reliability of the damage detection is somewhat unreliable.

The present invention has been made to solve the above problems, and provides a filter membrane damage detection method using a piezoelectric material that can easily determine whether the filter membrane is damaged using a piezoelectric body and can improve the accuracy of damage detection. There is a purpose.

In accordance with another aspect of the present invention, there is provided a method for detecting damage to a filter membrane using a piezoelectric body, the method comprising: preparing a membrane module in a steady state with an empty interior, measuring a reference resonance frequency of the membrane module in a steady state; Performing a membrane filtration process using the membrane module, discharging raw water and treated water in the membrane module after the membrane filtration process is completed, measuring a resonance frequency of the diagnosis of the membrane module, and the reference Comparing the resonance frequency and the check resonance frequency, and confirming whether or not to determine whether the damage to the membrane module that generated the check resonance frequency characterized in that it comprises a.

The measuring of the reference resonance frequency and the measuring of the diagnosis resonance frequency may include injecting a gas or a liquid of a predetermined pressure into the membrane module, and mechanical vibration of the membrane module according to the gas or liquid injection is performed by the membrane module. The method may include converting an electrical signal by a piezoelectric material attached to one side of the electrode, and measuring a reference resonance frequency or a diagnosis resonance frequency from the electrical signal of the piezoelectric body.

The membrane module is composed of a housing and a plurality of filtration membranes provided in the housing, the space in the membrane module is divided into a primary side outside the filtration membrane and a secondary side inside the filtration membrane based on the surface of the filtration membrane, the gas or liquid May be injected into the primary side or secondary side of the membrane module.

The filter membrane damage detection method using the piezoelectric body according to the present invention has the following effects.

With the piezoelectric body attached to the membrane module, the resonance frequency is measured from the electrical signal generated by the piezoelectric body and compared with the reference resonance frequency in the normal state to easily identify whether the filter membrane is damaged and to improve the accuracy of damage detection. You can do it.

1 is a block diagram of a filter membrane damage detection apparatus using a piezoelectric body according to an embodiment of the present invention.
2 is a detailed block diagram of a membrane filtration apparatus according to an embodiment of the present invention.
Figure 3 is a flow chart for explaining a filter membrane damage detection method according to an embodiment of the present invention.
4A and 4B are reference diagrams illustrating a case where gas or liquid is injected into a membrane module and a damaged membrane module in a normal state, respectively.
Figure 5a is a comparison of the reference resonance frequency and the detection resonance frequency of the undamaged membrane module.
Figure 5b is a comparison of the reference resonance frequency and the detection resonance frequency of the damaged membrane module.
6 is a reference diagram illustrating a case where a plurality of membrane modules are configured.

Hereinafter, a method of detecting damage to a filter membrane using a piezoelectric body according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 1 is a configuration diagram of a filter membrane damage detection apparatus using a piezoelectric body according to an embodiment of the present invention, Figure 2 is a detailed configuration diagram of a membrane filter device according to an embodiment of the present invention.

As shown in FIG. 1, an apparatus for detecting damage to a filtration membrane using a piezoelectric body according to an embodiment of the present invention includes a membrane filtration apparatus including a membrane module 110, a resonance frequency measuring unit 130, and a control unit 140. It is made to include.

As shown in FIG. 2, the membrane filtration apparatus includes a membrane module 110, and the membrane module 110 includes a housing 111 and a plurality of filtration membranes 112 provided in the housing 111. It is composed. At this time, the filtration membrane 112 includes a microfiltration and ultrafiltration membranes used for general water treatment such as water treatment and seawater desalination treatment, and may be configured in the form of hollow fiber in one embodiment.

The membrane module 110 is divided into a primary side 113 outside the filtration membrane 112 and a secondary side 114 inside the filtration membrane 112 based on the surface of the filtration membrane 112. In addition, one end of the membrane module 110 is connected to the raw water tank 101, the other end is connected to the treatment tank (103). Under such a configuration, the raw water of the raw water tank 101 is supplied to the primary side 113 of the membrane module 110 through the raw water supply pipe 102, and the raw water supplied to the primary side 113 is the filtration membrane. The contaminants in the raw water filtered by the filter 112 are filtered by the filter membrane 112, and the treated water passes through the filter membrane 112 and is supplied to the secondary side 114, which is an internal space of the filter membrane 112, and the secondary side 114. ) Treated water is finally discharged to the treated water tank 103 through the treated water discharge pipe (104).

On the other hand, the primary side 113 or the secondary side 114 is a gas (in one embodiment, air) or a liquid (in one embodiment, water) at a predetermined pressure to detect damage to the filtration membrane 112, which is an object of the present invention. It may be supplied, it may be provided with a pneumatic, hydraulic pressure gauge for measuring the pressure of the gas or liquid to be supplied. In this case, the gas and the liquid are respectively supplied from the gas injection means 150 and the liquid injection means 160, and when the gas is supplied, separate first and second gas supply pipes 151 and 152 may be provided. When the liquid is supplied, the primary side 113 may be the raw water tank 101 may be the liquid injection means 160 and the secondary side 114 may be the treatment water tank 103 may be the liquid injection means 160. In addition, in addition to the raw water tank 101 and the treatment water tank 103, a separate liquid injection means 160 may be provided to inject liquid into the primary side 113 and the secondary side 114, respectively.

In addition, the piezoelectric body 120 is further provided on the surface of the housing 111 to accurately detect the surface of the membrane module 110 in order to detect damage to the filtration membrane 112. The piezoelectric body 120 is integrally attached to the membrane module 110 and converts the mechanical vibration of the membrane module 110 into an electrical signal. The resonance frequency measuring unit 130 to be described later provides the electrical signal. Analyze and measure the resonant frequency. At this time, the mechanical vibration of the membrane module 110 is generated by the supply of a gas or a liquid of a predetermined pressure to the primary side 113 or the secondary side 114.

The piezoelectric material 120 may be a piezoelectric material having a piezoelectric effect, and in one embodiment, the first electrode (+) and the second electrode (-) are provided on both surfaces of the piezoelectric polymer film. The piezoelectric body 120 may be configured in the form. As the piezoelectric polymer film, polyvinylidene fluoride (PVDF), polyvinylidene cyanide (PVDCN), or the like may be used, and the first and second electrodes may be chromium (Cr), gold (Au), platinum (Pt), or the like. Can be.

The membrane filtration apparatus has been described above. In addition to the membrane filtration apparatus, the filtration membrane damage detecting apparatus using the piezoelectric body according to an embodiment of the present invention further includes a resonance frequency measuring unit 130 and a control unit 140 as described above.

The resonance frequency measuring unit 130 measures the resonance frequency by analyzing the electrical signal transmitted from the piezoelectric body 120. As described above, the piezoelectric body 120 is attached to the surface of the membrane module 110, the gas or liquid is supplied to the inside of the membrane module 110 to generate a mechanical vibration to the membrane module 110 When the piezoelectric body 120 converts an electrical signal to mechanical vibration, the resonance frequency measuring unit 130 measures the resonance frequency from the corresponding electrical signal, and ultimately, through the electrical signal of the piezoelectric body 120 through the membrane module ( 110 is to measure the resonant frequency.

The reason for measuring the resonance frequency of the membrane module 110 is by comparing the resonance frequency (reference resonance frequency) of the membrane module 110 in the normal state with the resonance frequency (check resonance frequency) of the membrane module 110 in the damaged state. This is to determine whether the specific membrane module 110 is damaged.

Therefore, if it is determined whether the filtration membrane 112 is damaged for the plurality of membrane modules 110, the reference resonance frequency of each of the plurality of membrane modules 110 should be measured in advance, and thus each membrane module ( In the state in which the reference resonance frequency of 110 is measured, the resonance frequency of each membrane module 110 is measured later and compared with the reference resonance frequency to detect whether the respective membrane module 110 is damaged. .

The control means 140 performs such a role as securing the reference resonance frequency, comparing the diagnosis resonance frequency with the reference resonance frequency, and determining whether there is any damage. That is, the control means 140 is a specific membrane module 110 measured through the resonance frequency measuring means 130 in a state in which the resonance frequency of the normal state, that is, the reference frequency of the plurality of membrane modules 110 is stored. Receives a check resonance frequency of the membrane module 110 by comparing the check resonance frequency and the pre-stored reference resonance frequency serves to determine whether the membrane module 110 is damaged.

Next, a filter membrane damage detection method using a piezoelectric body according to an embodiment of the present invention will be described. 3 is a flowchart illustrating a method of detecting damage to a filter membrane using a piezoelectric body according to an exemplary embodiment of the present invention.

First, as shown in FIG. 3, a membrane filtration apparatus in which the membrane filtration process is completed is prepared. In this case, the membrane filtration process refers to treating raw water with treated water using the membrane module 110. The membrane filtration device in a state where the membrane filtration process is completed is the primary side 113 and 2 of the membrane module 110. The state in which the raw water and the treated water do not exist on the vehicle side 114, that is, the state in which the membrane module 110 maintains an empty space.

In this state, the reference resonance frequency for the membrane module 110 in the normal state is measured (S301). Specifically, the gas or liquid at a predetermined pressure is supplied into the membrane module 110 (see FIG. 4A). The gas or liquid having a predetermined pressure may be supplied to the primary side 113 or the secondary side 114 of the membrane module 110. In addition, the pressure of the gas or liquid supplied into the membrane module 110 is preferably maintained at a constant state, specifically, the gas or liquid supplied to the primary side 113 is diffused to the secondary side 114. Preferably, the threshold pressure at the time point or the gas or liquid supplied to the secondary side 114 is maintained at the critical pressure at the time point at which the primary side 113 diffuses. The reason for applying the critical pressure as described above is to check whether the filtration membrane 112 of the membrane module 110 is damaged. If the filtration membrane 112 is damaged, the gas or liquid supplied at the critical pressure may be damaged by the filtration membrane 112. This is because the pressure drops sharply below the critical pressure, thereby generating a corresponding mechanical vibration. Of course, pressures outside the critical pressure may be applied to meet the device configuration and other conditions.

When a gas or a liquid having a predetermined pressure is supplied into the membrane module 110 in the normal state, a mechanical vibration corresponding thereto is generated, and the mechanical vibration is an electrical signal by the piezoelectric body 120 attached to the membrane module 110. Is converted into and transmitted to the resonance frequency measuring unit 130. The resonant frequency measuring unit 130 measures the resonant frequency from the transmitted electrical signal, and the measured resonant frequency is the resonant frequency for the membrane module 110 in the normal state, that is, the reference resonant frequency to the control means 140. Stored. When a plurality of membrane modules 110 are provided (see FIG. 6), a reference resonance frequency measurement process for each membrane module 110 is applied. The reference resonance frequency measurement process may be performed before the membrane filtration process.

As described above, in the state in which the reference resonance frequency is measured, the diagnosis resonance frequency of each membrane module 110 is measured by applying the same condition as the condition in which the reference resonance frequency is measured (S302). That is, a membrane filtration device of the membrane filtration process is completed, a gas or a liquid of a predetermined pressure is supplied to each membrane module 110, and mechanical vibration at this time is converted into an electrical signal through the piezoelectric body 120. The resonance frequency is measured by using the resonance frequency measuring unit 130. At this time, the pressure of the gas or liquid pressurized inside the membrane module 110 is the same as the reference resonance frequency measurement, it may correspond to a threshold pressure in one embodiment.

The measured resonant frequency of each of the membrane modules 110 is transmitted to the control means 140, and the control means 140 compares the pre-stored reference resonant frequency with the check resonant frequency (S303), and whether or not the same is true. Determine the damage to the membrane module 110 corresponding to the resonance frequency of the check (S304). When the filtration membrane 112 of the membrane module 110 is damaged, as the pressure of the gas or liquid injected at a predetermined pressure inside the membrane module 110 is reduced (see FIG. 4B), the mechanical vibration of the membrane module 110 may also be reduced. It shows a different form from the steady state mechanical vibration, and the corresponding resonance frequency is also different from the reference resonance frequency.

FIG. 5A is a comparison of the reference resonance frequency and the diagnosis resonance frequency of the undamaged membrane module. FIG. 5B is a comparison of the reference resonance frequency and the diagnosis resonance frequency of the damaged membrane module. ) And the resonance frequency graph (green) are almost identical, and through this, it can be determined that the membrane module generating the relevant resonance frequency is not damaged. On the contrary, in the case of FIG. 5B, it can be seen that the aspect of the diagnosis resonance frequency graph is significantly different from the reference resonance frequency graph, which indicates that there is damage to the membrane module corresponding to the diagnosis resonance frequency.

101: raw water tank 102: raw water supply piping
103: treatment tank 104: treatment water discharge pipe
110: membrane module 111: housing
112: filtration membrane 113: primary side
114: secondary side 120: piezoelectric body
130: resonant frequency measuring means 140: control means
150: gas injection means 151: first gas supply piping
152: second gas supply pipe 160: liquid injection means

Claims (6)

Preparing a membrane module in a normal state with an empty inside;
Measuring a reference resonance frequency of the membrane module in the steady state;
Performing a membrane filtration process using the membrane module;
After the membrane filtration process is completed, discharging raw water and treated water in the membrane module;
Measuring a diagnosis resonance frequency of the membrane module; And
And comparing the reference resonance frequency with a diagnosis resonance frequency, and checking whether there is a match, thereby determining whether the membrane module causing the diagnosis resonance frequency is damaged or not.
The method of claim 1, wherein the measuring of the reference resonance frequency and the measuring resonance frequency comprise:
Injecting a gas or liquid at a predetermined pressure into the membrane module;
Mechanical vibration of the membrane module due to the gas or liquid injection is converted into an electrical signal by a piezoelectric body attached to one side of the membrane module;
And detecting a reference resonance frequency or a diagnosis resonance frequency from the electrical signal of the piezoelectric body.
The membrane module of claim 2, wherein the membrane module includes a housing and a plurality of filtration membranes provided in the housing, and the space in the membrane module is divided into a primary side outside the filtration membrane and a secondary side inside the filtration membrane based on the surface of the filtration membrane. ,
The gas or liquid is a filter membrane damage detection method using a piezoelectric, characterized in that injected into the primary side or secondary side of the membrane module.
According to claim 3, wherein the gas or liquid injected to the primary side or the secondary side maintains a critical pressure, the threshold pressure is at the time or when the gas or liquid injected into the primary side diffuses to the secondary side A filter membrane damage detection method using a piezoelectric body, characterized in that the pressure at the time when the injected gas or liquid is diffused to the primary side.
The method of claim 2, wherein the piezoelectric material comprises a piezoelectric polymer material.
The method of claim 5, wherein the piezoelectric polymer material is any one of polyvinylidene fluoride (PVDF) and polyvinylidene cyanide (PVDCN).

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