JP6864291B2 - Deterioration evaluation method for separation membrane equipment - Google Patents

Description

The present invention relates to a method for evaluating the degree of contamination of a separation membrane device.

As an example of the separation membrane, a separation membrane device having a reverse osmosis membrane is known (see, for example, Patent Document 1). In this separation membrane device, the supplied raw water passes through the reverse osmosis membrane to be separated into permeated water and concentrated water.

The separation membrane itself may be contaminated depending on changes in the properties of raw water and the pretreatment status upstream of the separation membrane. In such a case, determine the fouling status from the measurement results of the pressure loss between the inlet and outlet of the separation membrane and the amount of permeated water at the outlet of the separation membrane, and if fouling is confirmed, perform backwashing or chemical cleaning. We are trying to recover the performance of the separation membrane.

Japanese Unexamined Patent Publication No. 2014-159015

However, a plurality of separation membranes are installed in one separation membrane device, and the number of separation membranes in the entire plant is large. Therefore, it is difficult to attach a pressure gauge or a current meter to each separation membrane. Moreover, even if it can be installed, it will lead to a significant increase in cost. Furthermore, it is not possible to measure the partial pressure loss or flow velocity inside the separation membrane, and it is not possible to evaluate the fouling of each part of the separation membrane.

Therefore, it has not been possible to identify the state and cause of contamination such as physical blockage of the separation membrane and obstruction of the flow path due to adhesion of inorganic substances and organic substances, and it has been difficult to take appropriate measures according to the mode of contamination.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for evaluating the degree of contamination of a separation membrane device capable of evaluating the degree of partial contamination of the separation membrane.

The present invention employs the following means in order to solve the above problems.
That is, the method for evaluating the degree of fouling of the separation membrane device according to the first aspect of the present invention is the method for evaluating the degree of fouling of the separation membrane device having a separation membrane through which water passes, and the portion where water exists in the separation membrane. A static magnetic field application step of applying a static magnetic field to a specific measurement region, a high frequency magnetic field pulse application step of applying a high frequency magnetic field pulse orthogonal to the static magnetic field to the measurement region while the static magnetic field is applied, and the high frequency. A data acquisition step including a signal intensity detection step of detecting the signal intensity of transverse magnetization by a magnetic field pulse, and an evaluation step of evaluating the degree of partial contamination of the separation membrane based on a value based on the signal intensity are included. ..

According to the above configuration, by acquiring the signal intensity of the transverse magnetization of a specific measurement region of the separation membrane and evaluating the degree of fouling based on the signal intensity, the degree of local fouling of the separation membrane can be determined from the outside of the separation membrane device. Can be evaluated.

The method for evaluating the degree of contamination of the separation membrane device further includes a relaxation time acquisition step of acquiring a relaxation time from the time change of the signal strength, and the evaluation step further includes a relaxation time acquisition step using the relaxation time as an index to stain the separation membrane. It may be a step of evaluating the degree.

Here, the entire water molecule is magnetized by the hydrogen nucleus having a magnetic moment. The magnetization of the water molecule is easily relaxed as the water molecule is surrounded by the solid.
That is, water located inside the solid (bound water) has a small degree of freedom of hydrogen because the movement of water molecules is restricted. Therefore, the energy given by the high-frequency magnetic field pulse is likely to be lost.
Therefore, the length of the relaxation time is a material for determining whether or not the water molecule is surrounded by the solid as a fouling substance. For example, in the case of a porous membrane, the size of the voids becomes smaller because the voids are fixedly filled as the fouling progresses. Therefore, the water molecules in the voids are surrounded by solids, and the movement of the water molecules is reduced. As a result, the lateral relaxation time of hydrogen nuclei of water molecules is shortened. That is, the longer the relaxation time, the lower the degree of fouling, and the shorter the lateral relaxation time, the higher the degree of fouling. Therefore, the degree of fouling can be evaluated by using the relaxation time as an index.
As the relaxation time, a lateral relaxation time, which is a time constant of the relaxation curve obtained from the time series of signal strength, or a time until the relaxation curve settles in a steady state can be adopted.

In the above-mentioned method for evaluating the degree of fouling of the separation membrane device, the data acquisition step is executed in the same measurement region in the stationary state where there is no flow velocity of water and in the flow state where water is flowing in the separation membrane. The evaluation step further includes a signal strength ratio acquisition step of acquiring a signal strength ratio which is a ratio of the signal strength in the flow state to the signal strength in the stationary state from the signal strength in the stationary state and the flow state. May be a step of evaluating the degree of contamination of the separation membrane using the signal intensity ratio as an index.

In a stationary state with no flow velocity, the water in the measurement area stays in place over time, while in a flow state with a flow velocity, the water laterally magnetized by the high-frequency magnetic field pulse gradually exits the measurement area. become. Therefore, the signal strength becomes smaller as the transversely magnetized water goes out.
Here, when the degree of contamination of the separation membrane is low in the distribution state, water smoothly permeates through the separation membrane, so that the transversely magnetized water easily goes out from the measurement region. Therefore, the signal strength ratio shows a relatively small value. On the other hand, when the degree of contamination of the separation membrane is high, it is difficult for water to permeate through the separation membrane, so that the transversely magnetized water is difficult to leave. Therefore, the signal strength ratio shows a relatively large value. Therefore, the degree of fouling can be evaluated by using the signal strength ratio as an index.

In the method for evaluating the degree of fouling of the separation membrane device, the data acquisition step is provided outside the static magnetic field application portion to which the static magnetic field can be applied and the static magnetic field application portion, and the high frequency magnetic field pulse can be applied. It may be performed by using a nuclear magnetic resonance scanner provided with a high-frequency coil and in which the measurement region is set further outward than the high-frequency coil when viewed from the static magnetic field application unit.

Since the measurement area is set outside the high-frequency coil when viewed from the static magnetic field application part, for example, when the nuclear magnetic resonance scanner is installed outside the membrane separation device, the measurement area is set inside the membrane separation device. it can. Thereby, the data inside the membrane separation device can be easily acquired.

According to the present invention, the degree of partial fouling of the separation membrane can be evaluated.

It is a vertical sectional view of the reverse osmosis membrane apparatus (separation membrane apparatus) which concerns on 1st Embodiment. FIG. 2 is a sectional view taken along line II-II of FIG. It is a vertical sectional view of the nuclear magnetic resonance scanner which concerns on 1st Embodiment. It is a top view of the nuclear magnetic resonance scanner which concerns on 1st Embodiment. It is a flowchart which shows the procedure of the pollution degree evaluation method of the reverse osmosis membrane apparatus (separation membrane apparatus) which concerns on 1st Embodiment. It is a graph which shows the free induction decay (FID) of the signal intensity of the transverse magnetization and the relaxation curve of the transverse magnetization acquired in the data acquisition process of 1st Embodiment. It is a graph which shows the relaxation curve of transverse magnetization. It is a graph which shows the frequency distribution of relaxation time in different measurement regions of a reverse osmosis membrane. It is a flowchart which shows the procedure of the pollution degree evaluation method of the reverse osmosis membrane apparatus (separation membrane apparatus) apparatus which concerns on 2nd Embodiment. It is a graph which shows the relationship between the flow velocity and the signal intensity ratio at different degree of fouling. It is a graph which shows the relationship between the signal strength ratio and the degree of fouling. It is a perspective view of the nuclear magnetic resonance scanner which concerns on the modification.

Hereinafter, the method for evaluating the degree of fouling of the reverse osmosis membrane device 1 (separation membrane device) according to the first embodiment of the present invention will be described in detail with reference to FIGS. 1 to 8.
The reverse osmosis membrane device 1 that is the target of the pollution degree evaluation method of the present embodiment is a kind of separation membrane device, and is a device that separates the supplied raw water W1 into permeated water W2 and concentrated water W3 and discharges them. is there. As shown in FIGS. 1 and 2, the reverse osmosis membrane device 1 includes a housing 2, an inner tube 6, and a membrane module 7.

The housing 2 has an outer cylinder 3, a first lid portion 4, and a second lid portion 5.
The outer cylinder 3 is a cylindrical member extending around an axis O along the horizontal direction.
The first lid portion 4 has a disk shape that closes one side (left side in FIG. 1) of the outer cylinder 3 in the axis O direction. A raw water introduction hole 4a is formed in the center of the first lid portion 4 so as to center the axis O and penetrate the first lid portion 4 in the axis O direction. Permeated water discharge that penetrates the first lid portion 4 in the axial direction O direction to the portion radially outside the raw water introduction hole 4a of the first lid portion 4 (the portion below the raw water introduction hole 4a in the present embodiment). The hole 4b is formed.

The second lid portion 5 has a disk shape that closes the other side (right side in FIG. 1) of the outer cylinder 3 in the axis O direction. At the center of the second lid portion 5, a concentrated water discharge hole 5a is formed centering on the axis O and penetrating the second lid portion 5 in the direction of the axis O. The second lid portion 5 penetrates the second lid portion 5 in the axial direction O direction through the portion radially outside the concentrated water discharge hole 5a (the portion below the concentrated water discharge hole 5a in the present embodiment). The permeated water discharge hole 5b is formed.

The middle tube 6 is a tubular member extending around the axis O. The inner pipe 6 is provided inside the outer cylinder 3 so as to reach the concentrated water discharge hole 5a of the second lid portion 5 from the raw water introduction hole 4a of the first lid portion 4. The middle pipe 6 is provided with a plurality of holes 6a penetrating the inside and outside in the radial direction at intervals in the axis O direction.

The membrane module 7 is fixed to the outer peripheral surface of the inner tube 6 inside the housing 2. The membrane module 7 is composed of a reverse osmosis membrane 7a (separation membrane). In the present embodiment, the membrane module 7 is a so-called spiral type module in which the reverse osmosis membrane 7a is wound while being sequentially laminated on the outer peripheral surface of the inner tube 6.

In the reverse osmosis membrane device 1 having the above configuration, the raw water W1 introduced into the raw water introduction hole 4a on one side of the inner pipe 6 in the axis O direction by being pumped by a pump (not shown) moves the inside of the inner pipe 6 in the axis O direction. It is distributed to. Impurities are removed from the raw water W1 that comes into contact with the membrane module 7 through the hole 6a of the middle pipe 6 in the process of permeating the membrane module 7. The water that has permeated the membrane module 7 in this way is discharged as permeated water W2 from the permeated water discharge holes 4b and 5b to the outside of the reverse osmosis membrane device 1. On the other hand, the concentrated water W3 whose impurity concentration has increased due to the removal of the permeated water W2 from the raw water W1 is discharged to the outside of the reverse osmosis membrane device 1 from the concentrated water discharge hole 5a on the other side of the inner pipe 6 in the axis O direction. To.

In such a reverse osmosis membrane device 1, impurities adhere to the reverse osmosis membrane 7a of the membrane module 7 with the operating time. In particular, depending on changes in the properties of the raw water W1 and the pretreatment status of the raw water W1 on the upstream side, the adhesion of such impurities and the fouling of the reverse osmosis membrane 7a may inadvertently proceed. The fouling evaluation method of the present embodiment is performed to evaluate such fouling of the reverse osmosis membrane 7a.

As shown in FIG. 3, the stain evaluation method of the present embodiment includes a data acquisition step S1, a relaxation time acquisition step S2, and an evaluation step S3.
The data acquisition step S1 is a step of acquiring data necessary for evaluation from the outside of the reverse osmosis membrane apparatus 1 using the nuclear magnetic resonance scanner 10 shown in FIGS. 1 and 2. Here, the configuration of the nuclear magnetic resonance scanner 10 will be described in detail with reference to FIGS. 4 and 5.

As shown in FIGS. 4 and 5, the nuclear magnetic resonance scanner 10 is a so-called unilateral open NMR scanner, and includes a static magnetic field application unit 20 and a high-frequency magnetic field pulse application unit 30.
The static magnetic field application unit 20 has a cylindrical permanent magnet 21 and a cylindrical permanent magnet 22.
The cylindrical permanent magnet 21 is a permanent magnet having a cylindrical shape, and the first end surface 21a of the cylinder, which is one end surface of the cylinder, is the north pole, and the second end surface 21b of the cylinder, which is the other end face, is the south pole. It is magnetized like this. In the following, the axis parallel to the central axis of the cylindrical permanent magnet 21 with the north pole side of the cylindrical permanent magnet 21 as + and the south pole side as − is the Z axis direction. Further, the pair of axes orthogonal to the Z-axis direction and orthogonal to each other are defined as the X-axis direction and the Y-axis direction, respectively.

The cylindrical permanent magnet 22 has a columnar shape extending in the Z-axis direction. The cylindrical permanent magnet 22 is arranged coaxially with the cylindrical permanent magnet 21 inside the cylindrical permanent magnet 21. The cylindrical permanent magnets 22 are arranged at intervals inside the cylindrical permanent magnets 21 in the radial direction. That is, the diameter of the cylindrical permanent magnet 22 is smaller than the inner diameter of the cylindrical permanent magnet 21, and the outer peripheral surfaces of the cylindrical permanent magnets 22 are arranged at intervals in the radial direction from the outer peripheral surfaces of the cylindrical permanent magnets 21. ing.

The cylindrical first end surface 22a, which is the end surface of the cylindrical permanent magnet 22 on the + side of the Z axis, is arranged so as to recede in the − direction of the Z axis from the cylindrical first end surface 21a. The cylindrical second end surface 22b, which is the end surface on the negative side of the Z axis of the cylindrical permanent magnet 22, is arranged so as to recede in the negative direction of the Z axis from the cylindrical second end surface 21b. That is, the first end surface of the cylinder 22a is arranged offset from the first end surface of the cylinder 21a on the − side of the Z axis. The second end surface of the cylinder 22b is arranged offset from the second end surface of the cylinder 21b on the − side of the Z axis.

According to such a static magnetic field application unit 20, a combined magnetic field of a magnetic field from the north pole to the south pole of the cylindrical permanent magnet 21 and a magnetic field from the north pole to the south pole of the cylindrical permanent magnet 22 is formed. In this synthetic magnetic field, a region where the X-axis direction component and the Y-axis direction component of the magnetic field are small and the Z-axis direction component is large is formed at a portion separated from the cylindrical permanent magnet 21 on the + side of the Z axis. .. Such a region is designated as a measurement region S by the nuclear magnetic resonance scanner 10. In other words, a region in which the Z-axis direction component in the static magnetic field generated from the static magnetic field application unit 20 is large and the X-axis direction component and the Y-axis direction component are small is selected as the measurement region S. Since the cylindrical permanent magnet 22 is offset with respect to the cylindrical permanent magnet 21 as described above, a relatively large magnetic field in the Z-axis direction is applied to a position separated from these magnets by a predetermined width (Z-axis direction). It can be made uniform within the range of (dimensions in the direction orthogonal to).

The high-frequency magnetic field pulse application unit 30 has a role of giving a high-frequency magnetic field pulse in the Y-axis direction to the measurement region S and detecting a nuclear magnetic resonance signal generated from the measurement region S. The high-frequency magnetic field pulse application unit 30 has a first high-frequency coil 31 and a second high-frequency coil 32.
The first high-frequency coil 31 and the second high-frequency coil 32 are arranged so as to be adjacent to each other at a position separated from the cylindrical permanent magnet 21 of the static magnetic field application unit 20 on the + side of the Z axis. The first high-frequency coil 31 and the second high-frequency coil 32 are coils wound so as to form a similar rectangular shape with the X-axis direction as the longitudinal direction and the Y-axis direction as the lateral direction when viewed from the Z-axis direction. Is. The first high frequency coil 31 is wound around the first coil axis O1 deviated from the Z axis to the − side of the Y axis. The second high frequency coil 32 is wound around the second coil axis O2 deviated from the Z axis to the + side of the Y axis. The first high-frequency coil 31 and the second high-frequency coil 32 are arranged so as to be adjacent to each other in the Y-axis direction when viewed from the Z-axis direction, and portions along the longitudinal direction face each other in the Y-axis direction.

A pulsed AC power source is passed through the first high-frequency coil 31 and the second high-frequency coil 32 by a power supply device (not shown). As a result, an alternating current flowing in the same direction (X-axis direction) is generated in the first high-frequency coil 31 and the second high-frequency coil 32 at portions adjacent to each other in the Y-axis direction, and a high-frequency magnetic field pulse is generated by the alternating current. To. In the measurement region S, the high-frequency magnetic field pulse is dominated by the magnetic field pulse component in the Y-axis direction. That is, the high-frequency magnetic field pulse application unit 30 applies a high-frequency magnetic field pulse orthogonal to the static magnetic field by the static magnetic field application unit 20 to the measurement region S.
Further, when the AC current by the power supply device is not supplied to the first high frequency coil 31 and the second high frequency coil 32, the AC voltage is caused by the change of the external magnetic field (rotational motion of the hydrogen nuclear magnetization vector that is being relaxed). Is induced and the alternating current generated by it is output.

As described above, the nuclear magnetic resonance scanner 10 is provided with a static magnetic field application unit 20 capable of applying a static magnetic field and an outer side (Z-axis direction) of the static magnetic field application unit 20 so that a high-frequency magnetic field pulse can be applied. It includes a first high frequency coil 31 and a second high frequency coil 32. Further, the measurement region S is set further outward than the first high frequency coil 31 and the second high frequency coil 32 when viewed from the static magnetic field application portion.
As shown in FIGS. 1 and 2, the static magnetic field application unit 20 and the high frequency magnetic field pulse application unit 30 are housed in a case 40 made of, for example, a non-magnetic material. In the nuclear magnetic resonance scanner 10, the surface of the case 40 facing the + side of the Z axis is defined as the measurement surface.

Next, the details of the data acquisition step S1 performed by using the nuclear magnetic resonance scanner 10 will be described. The data acquisition step S1 includes three steps of a static magnetic field application step S11, a high frequency magnetic field pulse application step S12, and a signal intensity detection step S13.

First, the static magnetic field application step S11 is executed. In the static magnetic field application step S11, the measurement surface of the nuclear magnetic resonance scanner 10 is pressed against the outer peripheral surface of the outer cylinder 3 of the reverse osmosis membrane device 1 as shown in FIG. As a result, as shown in FIG. 2, the measurement region S is set in a part of the membrane module 7 inside the reverse osmosis membrane device 1.

Next, the high-frequency magnetic field pulse application step S12 is executed. In the high-frequency magnetic field pulse application step S12, a high-frequency magnetic field pulse orthogonal to the static magnetic field is applied to the measurement region S in a state where the static magnetic field according to the static magnetic field application step S11 is applied to the measurement region S.
Specifically, a pulsed alternating current is supplied to the first high-frequency coil 31 and the second high-frequency coil 32 of the high-frequency magnetic field pulse application unit 30 in the nuclear magnetic resonance scanner 10. As a result, a high-frequency magnetic field pulse in the Y-axis direction is applied to the measurement region S from the first high-frequency coil 31 and the second high-frequency coil 32. A radio frequency magnetic field pulse (RF pulse) is applied as the high frequency magnetic field pulse. Further, the frequency of the high-frequency magnetic field pulse, that is, the frequency of the alternating current is set to a value that matches the precession frequency (Larmor frequency) of the hydrogen atom (proton).
As the method of applying the high-frequency magnetic field pulse, for example, known methods such as the Solid Echo method, the CPMG (Curr Purcel Meiboom Gil) method, and the Han Echo method can be used.

Subsequently, the signal strength detection step S13 is executed. In the signal intensity detection step S13, the signal intensity of the transverse magnetization of the measurement region S due to the high-frequency magnetic field pulse is detected.
That is, when a high-frequency magnetic field pulse is applied to the measurement region S, the magnetization of the water-based protons in the measurement region S in the Z-axis direction collapses in the Y-axis direction with, for example, a 90 ° flip angle. Then, when the application of the high-frequency magnetic field pulse is stopped, the magnetization of the proton returns to the original state, that is, the state magnetized only by the static magnetic field in the Z-axis direction. In the signal strength detection step S13, the energy released at this time is detected. Specifically, a signal of transverse magnetization (magnetization in the Y-axis direction orthogonal to the Z-axis direction) is applied to an AC current based on the AC voltage induced in the first high-frequency coil 31 and the second high-frequency coil 32 by the rotating magnetic field of protons. Detect as intensity. That is, the first high-frequency coil 31 and the second high-frequency coil 32 have two functions of excitation and detection, such as the role of applying a high-frequency magnetic field pulse and the role of detecting the signal intensity of the nuclear magnetic resonance signal generated by the high-frequency magnetic field pulse. It has two roles.

As described above, in the data acquisition step S1, the signal intensity of the transverse magnetization in the measurement region S can be obtained by going through the static magnetic field application step S11, the high frequency magnetic field pulse application step S12, and the signal intensity detection step S13. In the present embodiment, the relaxation time acquisition step S2 is executed after the data acquisition step S1.

In the relaxation time acquisition step S2 of the present embodiment, the lateral relaxation time T2 is acquired from the time change of the signal strength. That is, when the signal strength detected by the first high frequency coil 31 and the second high frequency coil 32 is recorded with time in the signal strength detection step S13, as shown in FIG. 6, a waveform that attenuates with time (free induction decay: FID). ) Can be obtained. Based on such a waveform, for example, a curve passing through the peak of the waveform can be acquired as a relaxation curve of transverse magnetization. Then, the time constant of this relaxation curve is acquired as the lateral relaxation time (spin-spin relaxation time) T2.

When the high-frequency magnetic field pulse application step S12, the signal strength detection step S13, and the relaxation time acquisition step S2 are performed based on the Solid Echo method, the procedure is as follows. First, as a high-frequency magnetic field pulse, a 90 ° pulse having a proton flip angle of 90 ° is applied twice at regular intervals to the measurement region S, and then the signal strength is acquired. Then, the waveform of free induction decay is acquired from the signal strength, and the relaxation curve and the lateral relaxation time T2 are acquired.
On the other hand, in the case of the CPMG method, after giving a 90 ° pulse, a 180 ° pulse at which the flip angle of the proton becomes 180 ° is given. After that, 180 ° pulses are repeatedly applied, and the maximum value of the signal intensity of the transverse magnetization is recorded each time. A relaxation curve is obtained from the attenuation of the signal strength thus obtained, and then the lateral relaxation time T2 is obtained.

Subsequently, the evaluation step S3 is performed. In the evaluation step S3, in the present embodiment, the degree of contamination of the reverse osmosis membrane 7a is evaluated by using the lateral relaxation time T2 as the relaxation time which is an index for evaluating the degree of contamination.
Here, the more the water in the reverse osmosis membrane 7a is polluted, the smaller the lateral relaxation time T2 in the measurement region S tends to be. The entire water molecule is magnetized because the hydrogen atom (proton) has a magnetic moment. The magnetization of the water molecule is easily relaxed as the water molecule is surrounded by the solid.
Therefore, the water (bonded water) located inside the solid has a small degree of freedom of hydrogen because the movement of water molecules is restricted. Therefore, the energy given by the high-frequency magnetic field pulse is likely to be lost. On the other hand, free water located outside the solid has a large degree of freedom of hydrogen because the movement of water molecules is not restricted, and energy is hard to be lost.

Therefore, the length of the lateral relaxation time T2 is an index for determining whether or not the water molecule is surrounded by the solid as a fouling substance. That is, the longer the lateral relaxation time T2, the lower the degree of fouling, and the shorter the lateral relaxation time T2, the higher the degree of fouling. Therefore, the degree of fouling can be evaluated by using the lateral relaxation time T2 as an index. For example, as shown in FIG. 7, the relaxation curve of the measurement region S having a low degree of fouling has a relatively large initial signal strength and gradually relaxes (the time constant is large) as shown by the solid line. On the other hand, in the relaxation curve of the measurement region S having a high degree of pollution, the initial signal strength is relatively small as shown by the broken line, and the relaxation curve is rapidly relaxed (the time constant is small).
That is, if the degree of fouling is high, dust accumulates in the measurement area S, and the volume moisture content decreases. Therefore, the signal strength also decreases. Then, since the void size becomes smaller, the lateral relaxation time T2 also becomes shorter.

As a specific evaluation method, for example, the degree of fouling in the measurement area S is evaluated by comparing the degree of fouling acquired in advance with the lateral relaxation time T2 with the lateral relaxation time T2 acquired in the above step. can do. Therefore, the degree of partial contamination of the membrane module 7 of the reverse osmosis membrane device 1 can be evaluated.

Further, for example, the lateral relaxation time T2 is acquired at the upstream portion (inlet portion) and the downstream side portion (exit portion) of the middle tube 6 in the membrane module 7, and the lateral axis is laterally relaxed as shown in FIG. By expressing the time T2 and the frequency distribution with the vertical axis as the frequency, the degree of fouling at different points of the film module 7 may be relatively evaluated.

Here, a modified example of the first embodiment will be described. In the modification, the width of the measurement area S of the nuclear magnetic resonance scanner 10 (dimensions in the direction orthogonal to the water flow direction, in the present embodiment, directions orthogonal to the Z axis) is set to an arbitrary value. On the other hand, the vertical width X (dimension in the water flow direction, Z-axis direction in the present embodiment) of the measurement area S is set as shown in the following equation (1).
Vertical width X of measurement area S ≈ flow velocity V of permeated water W2 × time until the signal intensity from the measurement area becomes steady after applying a high-frequency magnetic field pulse T ... (1)

The “flow velocity V of the permeated water W2” is a design value when the raw water W1 is introduced under predetermined operating conditions on the assumption that the reverse osmosis membrane device 1 of the membrane module 7 is not contaminated. Further, "time T until the signal intensity from the measurement region becomes a steady state after applying the high-frequency magnetic field pulse" means that the reverse osmosis membrane device 1 of the membrane module 7 is not contaminated, and the permeated water W2 flows at a flow velocity V. This is the time (relaxation time) from when the high-frequency magnetic field gradation is applied to the measurement region S until the signal strength, which will be described later, becomes a steady state. Here, the signal strength decreases with the passage of time, but does not become 0 due to the influence of noise, and finally settles at a certain steady value. That is, when the signal intensity becomes a steady state, it means that all the water laterally magnetized in the measurement region comes out of the measurement region.

In the embodiment, an example in which the lateral relaxation time T2, which is a time constant, is used as the relaxation time as an index of the degree of fouling has been described. On the other hand, in the modified example, the degree of fouling is evaluated by using the time until the signal strength of the relaxation curve becomes a steady state as the relaxation time.
In this modification, the vertical width of the measurement area S is set in relation to the above equation (1). When the degree of fouling is 0, all the transversely magnetized water in the measurement region S is discharged after a lapse of a specific time. On the other hand, when the post-staining is high, it becomes difficult for water to permeate the reverse osmosis membrane 7a, and as a result, there is laterally magnetized water even after a lapse of a specific time. Therefore, in this case, the time until the signal strength becomes a steady state becomes large. By utilizing this relationship, the degree of fouling can be evaluated in the same manner as described above, with the time until the signal strength becomes a steady state as the lateral relaxation time T2. That is, by using the relaxation time as an index, it is possible to perform an evaluation in consideration of both relaxation of transverse magnetization and outflow from the measurement region S.

The data acquisition step S1 by the nuclear magnetic resonance scanner 10 is performed by continuously sliding the outer surface of the outer cylinder 3 of the reverse osmosis membrane device 1 with the nuclear magnetic resonance scanner 10 as shown in FIG. Thereby, the measurement area S can be arbitrarily set in the membrane module 7, and the degree of partial contamination in the membrane module 7 can be evaluated.

That is, in the present embodiment, by using the nuclear magnetic resonance scanner 10, it is possible to acquire data regardless of the site or installation location of the reverse osmosis membrane 7a. This makes it possible to identify the soiled reverse osmosis membrane 7a and identify the soiled portion, and it is possible to easily select the membrane replacement work at the time of total soiling or physical blockage or the cleaning work at the time of partial soiling. ..

Furthermore, by grasping the behavior of water, it is possible to identify the pollution status (physical blockage and flow path obstruction due to adhesion of inorganic substances and organic substances) in the reverse osmosis membrane 7a and the cause thereof, and it becomes possible to enter the pollution and deterioration mode. Appropriate measures can be taken accordingly. Further, by re-measuring the reverse osmosis membrane 7a after the countermeasure, the degree of performance recovery can be quantitatively evaluated.

Next, the second embodiment of the present invention will be described with reference to FIGS. 9 to 11. In the second embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.
As shown in FIG. 9, the evaluation method of the reverse osmosis membrane device 1 of the second embodiment includes data acquisition steps S1A and S1B in different states, a signal intensity ratio acquisition step S20, and an evaluation step S30.

The data acquisition steps S1A and S1B of the present embodiment are performed in the same measurement area S in two states, a stationary state in which water is not flowing and a distribution state in which water is flowing. The stationary state is a state in which the stop of the raw water W1 on the reverse osmosis membrane device 1 by the pump is stopped, and since no pressure is applied to the reverse osmosis membrane 7a, water does not permeate. Therefore, the amount of water distributed becomes zero. On the other hand, the distribution state is a state in which the raw water W1 is supplied to the reverse osmosis membrane device 1 by a pump. The raw water W1 is supplied by the pump so that the water flows in the membrane module 7 at the initially set average flow velocity in a state where the reverse osmosis membrane 7a is not contaminated.
Then, in the data acquisition steps S1A and S1B, the signal strength of the transverse magnetization in each state is acquired by performing the static magnetic field application step S11, the high frequency magnetic field pulse application step S12, and the signal strength detection step S13 as in the first embodiment. ..

Next, the signal intensity ratio acquisition step S20 is executed. Acquires the signal strength ratio (= signal strength in the distribution state / signal strength in the stationary state) for acquiring the signal strength ratio, which is the ratio of the signal strength in the distribution state to the signal strength in the stationary state.
The signal strength in the stationary state and the signal strength in the distribution state are attenuated in the same manner as the waveform shown in FIG. Therefore, the relaxation curve becomes a curve that gradually decays with time. As the signal strength in the stationary state and the flow state used when acquiring the signal strength ratio, it is preferable to adopt the signal strength at the time when the same time elapses after applying the high-frequency magnetic field pulse.

Subsequently, the evaluation step S30 is performed. In this evaluation step S30, the degree of contamination of the separation membrane is evaluated using the signal intensity ratio as an index.
Here, FIG. 10 shows a graph of the relationship between the flow velocity and the signal intensity ratio at different pollution degrees. As can be seen from the graph, when the degree of fouling is small, the signal intensity ratio decreases significantly as the flow velocity increases, whereas when the degree of fouling is large, the signal intensity ratio decreases due to the increase in the flow velocity. Is small.

That is, when the degree of fouling is small, water permeates smoothly after applying a high-frequency magnetic field pulse, so that the amount of laterally magnetized water in the measurement region S is greatly reduced. Therefore, the signal strength ratio becomes small. On the other hand, when the degree of fouling is large, the water permeability is lowered due to fouling caused by the raw water W1. Therefore, even after a lapse of a specific time, the water content laterally magnetized by the high-frequency magnetic field pulse exists in the measurement region S. Therefore, the decrease in the signal strength ratio is small.
Therefore, the signal intensity ratio and the degree of fouling have a correlation with each other as shown in FIG. Therefore, the degree of contamination of the film module 7 can be evaluated using the signal intensity ratio as an index.
From the above, the evaluation method of the second embodiment can also evaluate the degree of partial contamination of the film module 7 as in the first embodiment.

Although the embodiments of the present invention have been described above, the present invention is not limited to this, and can be appropriately modified without departing from the technical idea of the invention.
For example, as shown in FIG. 12, as a modified nuclear magnetic resonance scanner 10A, a static magnetic field application unit 20 and a high-frequency magnetic field pulse application unit 30 similar to those in the embodiment are provided at the tip 11 of a long fiber. May be adopted. In this case, by inserting the tip 11 of the fiber into a narrow space, more partial data of the reverse osmosis membrane 7a can be obtained.

Further, a dome-shaped or arch-shaped nuclear magnetic resonance scanner 10 may be adopted, for example, as in a medical NMR apparatus. In the case of a dome shape, it is possible to measure a circular flat membrane, and in the case of an arch shape, it is possible to measure a cylindrical reverse osmosis membrane 7a. Further, by optimizing the magnitude of the magnetic field, the procedure of the coil, and the size according to the size of the object to be measured, detailed water behavior data inside the object can be acquired. Further, it is possible to measure the round cross section of the membrane module 7, and it is also possible to create a three-dimensional mapping of the fouling state.

In the embodiment, the reverse osmosis membrane 7a has been described as an example of the separation membrane, but the present invention is not limited to this, and other separation membranes may be used as the evaluation target of the evaluation method according to the present invention. For example, a filtration membrane, an ion exchange membrane, or the like may be adopted as the separation membrane.

In the embodiment, the measurement area S is set to have a rectangular shape with a cross section orthogonal to the axis O, but for example, the measurement region S may have a rectangular shape with a cross section including the axis. In this case, it is preferable that the water flow direction is the vertical width X of the measurement area S.
Further, in the embodiment, the measurement region S is set in the membrane module 7, but for example, the region where water passing through the membrane module 7 flows, that is, the inner peripheral surface of the outer cylinder 3 and the outer peripheral surface of the membrane module 7. It may be set in the area between. In this case, the measurement area S is located relatively close to the outside of the reverse osmosis membrane device 1. Therefore, the magnetic force of the static magnetic field application unit 20 forming the measurement region S can be reduced. Therefore, for example, there is an advantage that the permanent magnet constituting the static magnetic field application unit 20 can be miniaturized.

Further, in the embodiment, an example in which a permanent magnet is used as the static magnetic field application unit 20 has been described, but an electromagnet that generates a static magnetic field may be used. In the embodiment, an example using two coils, the first high frequency coil 31 and the second high frequency coil 32, has been described, but if a magnetic field can be applied from the Y-axis direction, only a single high frequency coil may be used. Good.
Further, the film module 7 is not limited to the so-called spiral shape, and may have other forms.

1 Reverse osmosis membrane device (separation membrane device)
2 Housing 3 Outer cylinder 4 First lid 4a Raw water introduction hole 4b Permeated water discharge hole 5 Second lid 5a Concentrated water discharge hole 5b Permeated water discharge hole 6 Middle pipe 6a Hole 7 Membrane module 7a Reverse osmosis membrane (separation membrane) )
10 Nuclear magnetic resonance scanner 10A Nuclear magnetic resonance scanner 11 Fiber tip 20 Static magnetic field application part 21 Cylindrical permanent magnet 21a Cylindrical first end surface 21b Cylindrical second end surface 22 Cylindrical permanent magnet 22a Cylindrical first end surface 22b Cylindrical second end surface 30 High-frequency magnetic field pulse application unit 31 First high-frequency coil 32 Second high-frequency coil 40 Case S1 Data acquisition process S1A Data acquisition process S1B Data acquisition process S11 Static magnetic field application process S12 High-frequency magnetic field pulse application process S13 Signal strength detection process S2 Relaxation time acquisition process S20 Signal intensity ratio acquisition process S3 Evaluation process S30 Evaluation process W1 Raw water W2 Permeated water W3 Concentrated water S Measurement area O Axis line O1 First coil axis O2 Second coil axis T2 Lateral relaxation time

Claims (4)

It is a method for evaluating the degree of fouling of a separation membrane device having a separation membrane through which water passes.
A step of applying a static magnetic field in which a static magnetic field is applied to a partial measurement region where water exists in the separation membrane device, and a high-frequency magnetic field pulse orthogonal to the static magnetic field is applied to the measurement region while the static magnetic field is applied. A data acquisition step including a high-frequency magnetic field pulse application step and a signal strength detection step of detecting the signal strength of transverse magnetization by the high-frequency magnetic field pulse.
An evaluation step for evaluating the degree of partial contamination of the separation membrane device based on the value based on the signal strength, and an evaluation step.
A method for evaluating the degree of contamination of a separation membrane device including. The relaxation time acquisition step of acquiring the relaxation time from the time change of the signal strength is further included.
The evaluation step is the method for evaluating the degree of contamination of the separation membrane device according to claim 1, wherein the degree of contamination of the separation membrane is evaluated using the relaxation time as an index. The data acquisition step is executed in the same measurement region in the stationary state where there is no flow velocity of water in the separation membrane and in the distribution state where water is flowing in the separation membrane.
Further including a signal strength ratio acquisition step of acquiring a signal strength ratio which is a ratio of the signal strength in the flow state to the signal strength in the stationary state.
The evaluation step is the method for evaluating the degree of contamination of the separation membrane device according to claim 1, wherein the degree of contamination of the separation membrane is evaluated using the signal intensity ratio as an index. The data acquisition process is
A static magnetic field application unit to which the static magnetic field can be applied and a high-frequency coil provided outside the static magnetic field application unit to which the high-frequency magnetic field pulse can be applied are provided, and the measurement region is viewed from the static magnetic field application unit. The method for evaluating the degree of fouling of a separation film device according to any one of claims 1 to 3, which is performed using a nuclear magnetic resonance scanner set further outside than a high-frequency coil.

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