JP2023033785A - Separation membrane element - Google Patents

Abstract

To provide a separation membrane element capable of suppressing fouling in long term operation while reducing the flow resistance of a supply side flow passage when operating the separation membrane element.SOLUTION: A separation membrane element in the present invention comprises a water collecting pipe, a separation membrane, a supply side flow passage material and a permeation side flow passage material. The supply side flow passage material forms a supply side flow passage by being disposed between two surfaces of the separation membrane and is constituted with a fibrous raw X composed of a plurality of fibrous materials A arranged in one direction and a fibrous raw Y composed of a plurality of fibrous materials B arranged in a direction different from the fibrous raw X. In at least any one of the fibrous material A or the fibrous material B, a large diameter part and a small diameter part exist, and any one of the fibrous material A or the fibrous material B at an intersection part P has a gap part V with the separation membrane by forming the intersection part P where the small diameter part of the fibrous material A or the fibrous material B crosses the other fibrous material.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a separation membrane element for separating impurities from various liquids containing impurities, particularly for desalination of seawater, desalination of brackish water, production of ultrapure water, or wastewater treatment.

In the technology for removing ionic substances contained in seawater, brackish water, etc., the use of a separation method using a separation membrane element has been expanding in recent years as a process for saving energy and resources. Separation membranes used in separation methods using separation membrane elements are classified into microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes and forward osmosis membranes in terms of pore size and separation function. These membranes are used, for example, for the production of drinking water from seawater, brackish water, and water containing hazardous substances, the production of industrial ultrapure water, wastewater treatment, and the recovery of valuables. It is used properly depending on the separation component and separation performance.

Although there are various forms of separation membrane elements, they all have in common that raw water is supplied to one surface of the separation membrane and permeated fluid is obtained from the other surface. The separation membrane element is provided with a large number of bundled separation membranes so that the membrane area per separation membrane element is large, that is, the amount of permeated fluid obtained per separation membrane element is large. It is formed to be As the separation membrane element, various shapes such as a spiral type, a hollow fiber type, a plate and frame type, a rotating flat membrane type, and a flat membrane integrated type have been proposed according to uses and purposes.

For example, spiral separation membrane elements are widely used for reverse osmosis filtration. A spiral separation membrane element includes a water collection tube and a separation membrane unit wound around the water collection tube. The separation membrane unit consists of a feed-side channel material that supplies raw water (that is, water to be treated) as feed water to the separation membrane surface, a separation membrane that separates components contained in the raw water, and a separation membrane that permeates the feed-side fluid. It is formed by laminating a permeate-side channel material for guiding the separated permeate fluid to the water collecting pipe. A spiral separation membrane element is preferably used because it can apply pressure to raw water and can extract a large amount of permeated fluid.

When the separation membrane element is used to treat feed water, if the separation membrane element is operated for a long period of time, foulants such as organic substances and dust in the feed water clog the separation membrane and the channel material on the feed side. (fouling). The occurrence of fouling causes an increase in pressure loss and a corresponding decrease in water production. In order to suppress the deterioration of the element performance due to such fouling, for example, the thickness of the supply-side channel material may be increased to widen the supply-side channel, thereby reducing locations clogged with foulant. However, if the thickness of the channel material on the supply side is increased, the constituent fibers of the channel material on the supply side are in contact with the membrane surface, so dirt accumulates around the fibers, and fouling progresses. I will. In addition, in order to improve the element performance, it is preferable that the pressure loss is as low as possible, and there is a tendency that the wider the supply-side passage, the lower the pressure loss and the higher the element performance. Therefore, it has been proposed to improve the performance of the separation membrane element by means of a channel material on the supply side.

Specifically, Patent Literatures 1 and 2 propose nets in which the flow resistance is reduced by thinning the thickness of the crossing points of the fibrous materials in the channel material on the supply side. Further, in Patent Document 3, by providing a sliding portion at the intersection of the channel material on the supply side, the sliding portion moves with the flow of the supply water, thereby devising a channel material to which dirt is less likely to adhere.

Japanese Patent Publication No. 2006-507919 Japanese Patent No. 4587937 Japanese Patent Application Laid-Open No. 2006-305556

However, in the separation membrane element described above, dirt tends to accumulate most easily at the intersection of the supply-side channel, and the balance between the reduction of flow resistance and the suppression of fouling cannot be said to be sufficient. In some cases, the supply side channel was partially clogged. Accordingly, an object of the present invention is to provide a separation membrane element capable of suppressing fouling even during long-term operation while reducing the flow resistance in the feed-side channel.

In order to achieve the above object, according to the present invention, there is provided a separation membrane element comprising at least a collection tube, a separation membrane, a feed side channel material, and a permeate side channel material, wherein the feed side channel material is disposed between the two surfaces of the separation membrane to form a feed-side channel, and the feed-side channel material is a fibrous array composed of a plurality of fibrous materials A arranged in one direction. X and a fibrous row Y composed of a plurality of fibrous substances B arranged in a direction different from that of the fibrous row X, and at least one of the fibrous substances A and the fibrous substances B is thick. A diameter portion and a small diameter portion are present, and the small diameter portion of the fibrous material A or the fibrous material B and the other fibrous material are crossed to form an intersection point P, so that at least one of the above At least one of the fibrous material A and the fibrous material B at the intersection point P has a void V between itself and the separation membrane, and the ratio of the void V is the number of intersection points in the channel material on the supply side. There is provided a separation membrane element characterized by having a content of 25% or more with respect to the

Further, according to a preferred embodiment of the present invention, both the fibrous material A and the fibrous material B of the supply side channel material have a large-diameter portion and a small-diameter portion, and the fibrous material A and the fibrous material A By crossing the fibrous material B at the small diameter portion to form the intersection point P, the fibrous material A and the fibrous material B at the intersection part P have the gap V between the separation membrane and the separation. A membrane element is provided.

Moreover, according to a preferred embodiment of the present invention, there is provided a separation membrane element in which the thickness D1 of the small diameter portion is 0.1 mm or more.

Further, according to a preferred embodiment of the present invention, there is provided a separation membrane element in which 75% or more of the voids V of the feed-side channel material are present in the feed-side channel material.
Further, according to a preferred embodiment of the present invention, when the length of the small diameter portion is L ₁ and the length of the large diameter portion is L ₂ , the length ratio L ₁ /L ₂ is 0.1 to 15. A separation membrane element is provided that ranges from

According to the present invention, a separation membrane element having excellent operational stability can be obtained because it has gaps at intersections where fouling is likely to occur, and can suppress an increase in differential pressure and a decrease in water production due to clogging of the supply-side channel. can be done.

FIG. 1 is a partially exploded perspective view showing an example of a separation membrane element. FIG. 2 is a plan view showing an example of the supply side channel material of the present invention. FIG. 3 is a cross-sectional view showing an example of the supply-side channel material of the present invention. FIG. 4 is a perspective view showing an example of the supply side channel material of the present invention. 5(a) to 5(f) are cross-sectional views showing examples of the supply-side channel material of the present invention. FIG. 6 is a cross-sectional view showing an example of the supply-side channel material of the present invention. FIG. 7 is a cross-sectional view showing an example of the supply side channel material of the present invention. FIG. 8 is a cross-sectional view showing an example of the supply side channel material of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.

In this specification, "mass" is synonymous with "weight". Also, in this specification, "-" means that the numerical values before and after it are included as lower and upper limits.

<Separation membrane element>
The separation membrane element of the present invention includes at least a collection tube, a separation membrane, a feed-side channel material, and a permeate-side channel material.

In the spiral separation membrane element 1 shown in FIG. 1, a polymer net is used as the feed-side channel material 2 that forms the feed-side channel. As the channel material 4 on the permeate side, tricot with finer spacing than the channel material 2 on the supply side is used for the purpose of preventing the separation membrane 3 from sagging and forming the channel on the permeate side. An envelope-like membrane 5 is formed by the permeate-side channel material 4 and the separation membranes 3 laminated on both sides of the permeate-side channel material 4 and adhered in an envelope shape. The inner side of the envelope-like membrane 5 constitutes a permeate-side channel. The envelope-like membranes 5 alternately laminated with the supply-side channel material 2 are spirally wound by adhering a predetermined portion on the opening side to the outer peripheral surface of the water collecting pipe 6 . The direction of the x-axis shown in FIG. 1 is the longitudinal direction of the water collecting pipe 6 . Also, the direction of the y-axis is the direction perpendicular to the longitudinal direction of the water collecting pipe 6 .

The spiral separation membrane element 1 is normally supplied with feed water 7 from one side, and the feed water 7 is gradually separated into a permeate 8 and a concentrate 9 while flowing parallel to the water collecting pipe 6 . The permeated water 8 exits the spiral separation membrane element 1 from the opposite side to which the feed water 7 is supplied.

In this method, since the feed water 7 flows from one side of the spiral separation membrane element 1 to the other side, there is inevitably a sufficient distance in contact with the membrane. and the concentrated water 9 are sufficiently separated. There are various forms of separation membrane elements, but they all have in common that feed water is supplied to one side of the separation membrane and permeated water is obtained from the other side. As the separation membrane element of the present invention, in addition to the spiral type, various shapes of separation membrane elements using flat membranes such as the plate and frame type and the flat membrane integrated type may be adopted according to the application and purpose. can be done.

<Supply side channel>
(Supply side channel material)
As shown in FIG. 2, the supply-side channel material of this embodiment is different from the plurality of fibrous rows X composed of the fibrous materials A (21) arranged in one direction and the fibrous rows X The net is composed of a plurality of fibrous rows Y composed of fibrous materials B (22) arranged in a direction, and the fibrous rows X and the fibrous rows Y intersect each other to form intersections at a plurality of points. have a shape. The crossing may be a three-dimensional crossing between the fibrous material A and the fibrous material B, or a plane crossing.

In the separation membrane element, in order to suppress the deposition of dirt (fouling) that accumulates on the separation membrane surface and the supply side channel material, it is necessary to reduce the stagnant points of the supply water, that is, the clogging points of the supply side channel, It is important to create a water flow behind the This is because dirt tends to accumulate in places where the supply water stagnates, and the dirt can be easily discharged by reducing the stagnant places. Moreover, even if dirt adheres, the dirt is pushed out by the flow of water, and the progress of fouling can be suppressed. In the conventional supply-side channel material, the large-diameter part and the large-diameter part of the fibrous material intersect to form an intersection point, which is the thickest in the supply-side channel material. The intersection of the parts ensured the space between the membranes. However, the intersection formed by the large-diameter portion and the large-diameter portion has a structure in which many stagnation points occur around the intersection, and dirt tends to accumulate.

In the separation membrane element, since the driving force for permeation is the transmembrane pressure difference, it is effective to increase the transmembrane pressure difference in order to improve the amount of fresh water produced. The transmembrane pressure difference is expressed by subtracting the flow resistance and the osmotic pressure from the pressure applied to the separation membrane element. Therefore, in order to increase the transmembrane pressure, it is necessary to increase the applied pressure, decrease the flow resistance, or decrease the transmembrane osmotic pressure. Considering the case where the applied pressure and the membrane surface osmotic pressure are the same, the flow resistance should be lowered in order to improve the amount of fresh water produced.

Since the supply water flows while spreading along the fibrous material of the channel material on the supply side, the fibrous material that is not parallel to the flow direction of the supply water blocks the flow channel and hinders the flow of the supply water. resistance tends to be higher. Therefore, either fibrous material A or fibrous material B has a large-diameter portion and a small-diameter portion along the longitudinal direction of the fibrous row, including an arbitrary fibrous row. This increases porosity and improves flow resistance.

In this embodiment, at least one of the fibrous material A and the fibrous material B has a large diameter portion and a small diameter portion, and the small diameter portion of the fibrous material A or the fibrous material B and the other fibrous material By forming the intersection point P by intersecting with the material, at least one of the fibrous material A or the fibrous material B at at least one of the intersection points P has a gap V between the separation membrane and the gap The proportion of part V is 25% or more of the number of intersections in the channel material on the supply side.

At least one of the fibrous materials A and B has a large-diameter portion and a small-diameter portion, so that the porosity can be increased and the flow resistance can be reduced. By having the above, it is possible to reduce the stagnant part, suppress the progress of fouling, suppress the increase in flow resistance, and reduce the decrease in the amount of fresh water produced.
(fiber shape)
Regarding the shape of fibers in this embodiment, the fibrous material A and the fibrous material B may have the same shape or different shapes. FIG. 4 is a perspective view showing an example of the channel material on the supply side, and when observed from the direction of the arrow, the side view shown in FIG. 5 can be mentioned. For example, the large-diameter portion and the small-diameter portion may be clearly separated as shown in FIG. 5(a), or the thread diameter may change gently as shown in FIG. 5(b). The fibrous material A and the fibrous material B may intersect each other as shown in FIG. 5(c), or may intersect the small-diameter portion and the length yarn as shown in FIG. 5(d). The large diameter portion and the small diameter portion may intersect as shown in FIG. good. Although not shown in these drawings, there is a large diameter in the depth direction of the drawing, and that portion can come into contact with the film surface.
(Intersection)
The intersection point P in the present embodiment refers to a location where the fibrous material A and the fibrous material B intersect. When it is desired to observe the intersection point P, as shown in FIG. 6, an arbitrary fibrous material A or B is extracted and selected. Then, the fibrous material B of the other (if the fibrous material A is selected, the fibrous material B) is cut parallel to the fibrous material A and close to the fibrous material A, and the fibrous material A is cut. Observe from a direction perpendicular to the object. At this time, in the cross section of the fibrous material B, a perpendicular line _LP is drawn at both ends of the cross section in a direction perpendicular to the planar direction of the supply side channel material, and a perpendicular line is drawn in a direction parallel to the planar direction of the supply side channel material A tangent line _LT is drawn at the top and bottom of the figure formed by filament A and filament B between _LP . A quadrangle formed by a perpendicular line _LP and a tangent line _LT is defined as an intersection point P.
(Gap)
As shown in FIG. 6, the gap V in this embodiment is defined as a gap when there is a space above or below the intersection point P. As shown in FIG. Although it is not necessary to have gaps on both the top and bottom sides of the intersection P, it is preferable to have gaps on both sides rather than on one side above or below the intersection, because the stagnant part is reduced. Cut the channel material on the supply side into 10 x 10 cm pieces, prepare aluminum plates with a thickness of 3 mm and a uniform thickness of the same cut area, place them on the top and bottom of the channel material on the supply side, and spread them evenly on the channel material on the supply side. When an aluminum block with a weight of 1 kg is placed on the aluminum plate placed on the channel material on the supply side so that a load is applied, and observed with a microscope or the like, there should be a space between the plate and the plate. The distance _LV between the intersection point P and the flat plate is preferably 0.01 mm or more, more preferably 0.05 mm or more. If the _LV is this distance or more, the turbidity can be improved and the adhesion of dirt can be suppressed. When there are spaces above and below the intersection point P, there are two distances _LV between the flat plates. At this time, the upper and lower distances _LV are defined as _LV1 and _LV2 , respectively. At this time, the longer distance is L _V1 , and the shorter distance is L _V2 . Voids V occupy 25% or more of the entire channel material on the supply side. It is more preferably present in an amount of 50% or more, and even more preferably in an amount of 75% or more. If the voids are within this range, the turbidity can be improved and the adhesion of dirt can be suppressed.

The ratio of voids in the channel material on the supply side can be determined by observing whether there are voids above and below the intersection point P using a commercially available microscope or X-ray CT measurement device. . If it exists above and below the intersection point P, it can be counted as two. It can be calculated by observing at least 50 locations (100 locations in total) and calculating the ratio of the number of voids present and the number of observations.

The ratio of the voids and the distance Lv between the intersection point P and the flat plate may vary depending on the observation method. If the rigidity of the channel material on the supply side is low, the threads at the crossing point bend and the distance from the flat plate becomes closer. If the weight sandwiched between the aluminum plates is too heavy, the channel material on the supply side will be deformed, the distance between the intersection and the flat plate will be reduced, and in some cases the gap will disappear. Therefore, it is important to sandwich the channel material on the supply side between aluminum plates and place a predetermined weight (1 kg) on it for observation.
(Thickness of intersection and supply side channel material)
The thickness D _C of the intersection is represented by the length L _P′ of the perpendicular line L _P cut by the tangent line L _T . The thickness D _C of the intersection is preferably 0.1 mm or more. If the thickness of the intersection portion is within this range, the rigidity of the channel material on the supply side can be ensured. The thickness D of the channel material on the supply side is represented by the sum of L _P' , L _V1 and L _V2 . In this embodiment, the average thickness of the channel material on the supply side is preferably 0.50 mm or more and 4.0 mm or less, more preferably 0.7 mm or more and 2.0 mm or less. If the average thickness of the channel material on the supply side is within this range, the pressure loss does not become too large, and a sufficient amount of material such as foulant that can accumulate on the membrane surface and the channel material on the supply side does not clog easily. It is possible to ensure stable operation of the separation membrane element for a long period of time without increasing the power required for the pump by suppressing clogging of the supply side channel by impurities in the supply water and foulants such as microorganisms. Become. If the feed-side channel material is thinner than this range, pressure loss increases and fouling tends to progress. If the channel material on the supply side is thicker than this range, it is not preferable from the standpoint of handling, but it is possible to adjust the rigidity to an appropriate value by selecting an appropriate intersection pitch and material.
In addition, the thickness of the crossing point and the channel material on the supply side is measured using a commercially available microscope or X-ray CT measurement device, observing a longitudinal section parallel to the fibrous row, and measuring the distance. The measurement mode can be used to extract and measure diameters at arbitrary 30 locations in the thickness of the channel material on the supply side or at intersections, and the average value can be obtained.

Further, the variation in the thickness of the channel material on the supply side is preferably 0.85 to 1.15 times the average thickness of the channel material on the supply side. If the variation in the thickness of the channel material on the feed side is within this range, the feed water can be uniformly supplied to the separation membrane element, so that the performance of the separation membrane can be exhibited uniformly.
(large diameter part/small diameter part)
In this embodiment, when the fibrous material A or the fibrous material B is observed from the side surface of the supply side channel material, as shown in FIG. Draw a vertical line in the middle of them and divide the distance between the vertical lines into 20 equal parts. The fiber diameter is measured at 10 points in each of the 20 equally divided sections, and the average value is calculated. The maximum and minimum average values are obtained in the 20 equally divided sections, and the average value Av is calculated. Here, another fibrous material (for example, fibrous material B when observing fibrous material A) at the intersection is ignored, and _LP and fibrous material A are shown in FIG. Connect the two intersecting points and draw an imaginary line. Using this virtual line, the fiber diameter can be measured.
For example, if the maximum value of 20 equally divided sections is 0.1 mm and the minimum value is 0.05 mm, the average value Av is 0.075. This Av becomes a critical value, and the section where the average value of each of the 20 equal divisions is larger than Av is defined as the large-diameter portion. On the other hand, the small-diameter portion includes either one of the two intersection points P used to calculate the large-diameter portion, exists in the same fibrous form as the selected intersection point P, and the adjacent intersection point P is similarly thick. A diameter portion is defined, and a section existing between two defined large diameter portions is defined as a small diameter portion.
The thickness of the small diameter portion is preferably 0.1 mm or more. If the thickness of the small-diameter portion is within this range, the rigidity of the channel material on the supply side can be ensured, and the device transportability and the constant-length cutting property during element production can be improved.
The small-diameter portion length _L1 and the large-diameter portion length _L2 can be calculated by measuring the lengths of the large-diameter portion and the small-diameter portion. The ratio L ₁ /L ₂ between the small diameter portion L ₁ and the large diameter portion L ₂ is preferably in the range of 0.1 to 15, more preferably in the range of 0.5 to 10, and more preferably 1 to 7. is more preferably in the range of If L ₁ /L ₂ is within this range, the porosity can be increased, the pressure loss can be reduced, and the turbidity can be improved while ensuring the rigidity of the channel material on the supply side. As a method for measuring the length _L1 of the small diameter portion and the length _L2 of the large diameter portion, the supply side channel material is observed from above in the thickness direction (that is, the plane of the supply side channel material), and measured using, for example, a microscope. be able to.
(ratio of thickness of large diameter part and small diameter part)
As the thickness _D1 of the small diameter portion and the thickness _D2 of the large diameter portion, a value obtained by averaging the diameters of the defined small diameter portion and large diameter portion is used. The thickness ratio D ₁ /D ₂ of the large-diameter portion and the small-diameter portion is preferably in the range of 0.1 to 0.8, more preferably in the range of 0.2 to 0.7. If D ₁ /D ₂ is within this range, it is possible to increase the porosity, reduce the pressure loss, and improve the turbidity discharge while ensuring the rigidity of the channel material on the supply side.
(intersection interval)
In this embodiment, the intersecting point interval (intersecting point period) c in the direction perpendicular to the supply water flow direction (raw water flow direction) of the supply side channel material 2 shown in FIG. 2 is in the range of 3 to 5 mm. is preferred, and more preferably in the range of 3.5 to 4.5 mm. If the intersecting point interval c of the channel material on the supply side in the direction perpendicular to the flow direction of the feed water is within this range, it is possible to suppress the phenomenon that the separation membrane falls into the gaps of the channel material on the supply side during the production of the separation membrane element. In particular, it is possible to stably form the flow path of the supply water inflow end face portion.

Further, the intersecting point interval d in the direction parallel to the flow direction of the supply water of the channel material on the supply side is preferably in the range of 4 to 9 mm, more preferably in the range of 4.5 to 7.0 mm. If the intersecting point interval d in the direction parallel to the flow direction of the feed water of the channel material on the feed side is within this range, the balance between the turbulent intensity of the feed water and the flow resistance can be achieved at the same time. And it becomes possible to improve the water-forming property.

As a method for measuring the intersecting point interval, the channel material on the supply side is observed from above in the thickness direction (that is, the plane of the channel material on the supply side), and the distance can be measured, for example, with a microscope.
(Angle between supply water flow direction and fibrous material)
When observing the channel material on the supply side from a plane, as the angle between the direction of flow of the supply water (that is, the longitudinal direction of the water collecting pipe) and the fibrous material increases, the turbulence strength increases, but the flow resistance tends to increase. Therefore, the angle is preferably 10° or more and 50° or less, more preferably 20° or more and 45° or less.
(Cross-sectional shape of fiber)
The cross-sectional shape of the fibers of the channel material on the supply side is not particularly limited, and various shapes such as circular, elliptical, and streamlined are conceivable. Moreover, it may be a shape in which a part of these forms is lacking.
(material)
The material of the channel material on the supply side is not particularly limited, but thermoplastic resins are preferable from the viewpoint of moldability, and polyethylene and polypropylene are particularly preferable because they are less likely to damage the surface of the separation membrane and are inexpensive. In addition, the fibrous material A and the fibrous material B of the supply-side channel material may be made of the same material, or may be made of different materials.
(Production method)
In forming the net-like supply side channel material, generally, the inner and outer 2 nozzles, which have many holes arranged on the inner and outer circumferences, are rotated in opposite directions, and the material is melted from the extruder. When or immediately after the resin comes out of the spinnerets, the threads coming out of the inner and outer spinnerets are crossed in a molten state and melted to form a network structure. At this stage, the net assumes a cylindrical shape. After that, the cylindrical net is cooled and solidified to determine the thickness, thread diameter, and intersecting point intervals, and then cut to obtain a sheet-like net.

As in this embodiment, the fibrous material A or the fibrous material B has a large diameter portion and a small diameter part, and the small diameter portion of the fibrous material A or the fibrous material B and the other fibrous material intersect. In order to manufacture the supply-side channel material that forms It is possible to employ a method in which a cylindrical net is molded, cooled and solidified, and then longitudinally stretched and then transversely stretched successively in a heating furnace.

The method of manufacturing the net of the present embodiment is not limited to these, and includes a method of compressing and deforming the fibrous material between the intersections by embossing, imprinting, pressing, etc., and casting a molten resin in a mold. It may be manufactured using a method of taking out and a 3D printer.
<Permeate side channel>
(permeation side channel material)
In the envelope-shaped membrane 5 , the separation membranes 3 are superimposed with their permeate-side surfaces facing each other. A flow path is formed. The material of the channel material on the permeate side is not limited, and tricot, nonwoven fabric, porous sheet with protrusions fixed thereto, film formed with unevenness and perforation, and uneven nonwoven fabric can be used. Also, projections functioning as permeate-side channel materials may be fixed to the permeate side of the separation membrane.
<Formation of Separation Membrane Leaf>
The separation membrane leaf may be formed by folding the separation membrane so that the supply-side surface faces inward, or by stacking two separate separation membranes so that the supply-side surfaces face each other. It may be formed by sealing the perimeter of the membrane.

Methods of "sealing" include bonding with an adhesive or hot melt, fusion bonding with heat or laser, and sandwiching a rubber sheet. Sealing by adhesion is particularly preferred because it is the simplest and most effective.
<Use of separation membrane element>
Separation membrane elements may be used as a separation membrane module by being connected in series or in parallel and housed in a pressure vessel.

Further, the separation membrane element and the separation membrane module described above can be combined with a pump that supplies fluid to them, a device that pre-processes the fluid, and the like to constitute a fluid separation device. By using this separator, for example, feed water can be separated into permeated water such as drinking water and concentrated water that has not permeated the membrane, so that desired water can be obtained.

The higher the operating pressure of the fluid separation device, the higher the removal rate, but the energy required for operation also increases. The operating pressure at which the feed water permeates is preferably 0.2 MPa or more and 6 MPa or less.

The higher the feed water temperature, the lower the salt removal rate, but the lower the feed water temperature, the lower the membrane permeation flux.

Further, when the pH of the raw water is in the neutral region, even if the raw water is a high salt concentration liquid such as seawater, the generation of scale such as magnesium is suppressed, and deterioration of the membrane is also suppressed.
(supply water)
The water supplied to the separation membrane element of the present embodiment is not particularly limited, and may be tap water that has been treated in advance, or water containing a large amount of impurities such as seawater, brackish water, or sewage water. For example, when used for water treatment, the raw water (supply water) is a liquid mixture containing 500 mg / L or more and 100 g / L or less of TDS (Total Dissolved Solids) such as seawater, brackish water, and waste water. mentioned. In general, TDS refers to the total amount of dissolved solids and is expressed as "mass/volume", but may also be expressed as "weight ratio" assuming that 1 L is 1 kg. According to the definition, it can be calculated from the weight of the residue after evaporating the solution filtered through a 0.45 μm filter at a temperature of 39.5 to 40.5 ° C., but more easily converted from the practical salinity (S) .

EXAMPLES The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these Examples.
(Thickness measurement of crossing point and supply side channel material)
A net-shaped sample was cut into 10×10 cm, and 3 mm-thick aluminum plates having the same cut-out area and uniform thickness were prepared and placed above and below the channel material on the supply side. An aluminum block having a weight of 1 kg was placed on an aluminum plate placed on the supply-side channel material so that a load was uniformly applied to the supply-side channel material. Using a high-precision shape measuring system KS-1100 manufactured by Keyence Corporation, a longitudinal section parallel to the fibrous rows was observed at a magnification of 20 times to confirm the thickness of the intersection point P and the channel material on the supply side. Specifically, 30 arbitrary intersection points P were extracted for the intersection point P, the _LV above and below the arbitrary intersection point P was measured for the thickness of the channel material on the supply side, and the average value was calculated. .
(intersection interval)
Using a high-precision shape measurement system KS-1100 manufactured by Keyence Corporation, the net-shaped sample is observed from the top in the thickness direction at a magnification of 20 times, and the intersecting point interval in the direction perpendicular to the flow direction of the supply water of the channel material on the supply side and the supply With respect to the intersecting point intervals in the direction parallel to the supply water flow direction of the side channel material, 30 arbitrary intersecting point intervals were extracted and measured, and the average value was calculated.
(Measurement of voids)
The ratio of voids in the channel material on the supply side is such that _LV exists at least above or below the intersection P when observing the intersection P, that is, when _LV is greater than 0, the void V is counted as present. If there are _LVs above and below the intersection point P, two gaps V are counted.
Using a high-precision shape measurement system KS-1100 manufactured by Keyence Corporation, a longitudinal section parallel to the fibrous row is observed at a magnification of 20 times, and 100 arbitrary intersection points P are extracted and observed, 200 voids V We counted the number of The ratio of the number of voids V and the number of intersections observed was calculated and used as the ratio of voids V. FIG.

(Measurement of large diameter part/small diameter part)
A fibrous material A or a fibrous material B is selected. Cut item B. Using a high-precision shape measurement system KS-1100 manufactured by Keyence Corporation, parallel to the plane of the net-like sample and perpendicular to any fibrous material A or fibrous material B Observation at a magnification of 20 times, any Three adjacent intersections P were extracted, and two adjacent intersections P were selected. A perpendicular line was drawn in the center of the two selected points of intersection P, and the interval between the perpendicular lines was divided into 20 equal parts. The fiber diameter was measured at 10 points for each of the 20 equally divided sections, and the average value was calculated. The maximum and minimum of the average values in the 20 equal sections were calculated, and the average value Av was calculated. A section having an average value Av or more was defined as a large-diameter portion. As the thickness D2 of the large-diameter portion, the average value of the fiber diameters in the section defined as the large-diameter portion was used. On the other hand, for the small-diameter portion, the large-diameter portion is similarly calculated for the middle of the three intersection points P selected when calculating the large-diameter portion and the intersection portion that was not used for calculating the large-diameter portion, and two large-diameter portions are calculated. A section existing between the portions was defined as a small-diameter portion. The thickness D1 of the small-diameter portion was obtained by extracting and measuring the fiber diameters of at least 30 arbitrary points in the section defined as the small-diameter portion, and using the average value thereof. These operations are performed at least 10 places on the supply side channel material, and the average value is used as the thickness of the large diameter portion and the thickness of the small diameter portion, and the length of the large diameter portion and the length of the small diameter portion are also defined. The length of the small diameter portion and the small diameter portion were calculated, and the average value was used as the length of the small diameter portion and the large diameter portion.
<Example>
(Preparation of supply side channel material Q)
Polypropylene is used as the material, and while the inner and outer mouthpieces with many small holes are rotated in opposite directions, molten resin is supplied from the extruder at a predetermined discharge pressure to produce a cylindrical shape with a network structure. molded the net. After cooling and solidifying, the feed side channel materials shown in Tables 1 and 2 were produced by a method in which longitudinal stretching and then transverse stretching were successively performed in a heating furnace. In addition, the molten resin discharge pressure from the extruder, the take-up speed, the longitudinal and transverse stretching ratios, and the temperature in the heating furnace were changed, and the structure was controlled so that the shape of the channel material on the supply side was finally obtained as shown in Tables 1 and 2. gone.
(Preparation of Spiral Separation Membrane Element)
A 16.0% by mass DMF solution of polysulfone was applied to a thickness of 180 μm on a non-woven fabric made of polyethylene terephthalate fiber (fineness: 1 decitex, thickness: about 90 μm, air permeability: 1 cc/cm ² /sec, density: 0.80 g/cm ³ ). A porous support layer (thickness (thickness 130 μm) rolls were produced.

After that, the surface of the polysulfone layer of the porous support membrane was immersed in an aqueous solution containing 1.5% by weight of m-PDA and 1.0% by weight of ε-caprolactam for 2 minutes, and then slowly pulled up vertically. rice field. Furthermore, excess aqueous solution was removed from the support film surface by blowing nitrogen from an air nozzle.

After that, an n-decane solution containing 0.08% by mass of trimesic acid chloride was applied so that the surface of the film was completely wetted, and then left to stand for 1 minute. Thereafter, excess solution was removed from the membrane by blowing air, and the membrane was washed with hot water at 80° C. for 1 minute to obtain a composite separation membrane roll.

The separation membrane thus obtained was folded and cut so that the effective area of the separation membrane element was 6.42 m ² . Separation membrane leaves were prepared by sandwiching them as road materials.

A tricot (thickness: 0.26 mm) shown in Table 1 was laminated on the permeation side of the obtained separation membrane leaf as a channel material on the permeation side, a leaf adhesive was applied, and a PVC (polyvinyl chloride) water collection tube ( Width: 1016 mm, diameter: 19 mm, 23 holes x 1 linear row), and after fixing the outer peripheral surface of the winding body with tape, cut the edges on both ends and attach the end plate, and one side A 4-inch diameter separation membrane element was prepared to which the feed water was supplied and the concentrated water was discharged from.
(Amount of fresh water produced)
The separation membrane element was placed in a pressure vessel, and a saline solution with a concentration of 500 ppm and an aqueous NaCl solution with a pH of 6.5 were used as feed water. Sampling was performed, and the water permeation rate (gallon) per day was expressed as the water production rate (GPD (gallon/day)). Note that the recovery rate was set to 8%.
(Removal rate (TDS removal rate))
The TDS concentration of the feed water used in the 1-minute operation and the sampled permeate water used in the measurement of the amount of fresh water produced was determined by conductivity measurement, and the TDS removal rate was calculated from the following equation.

TDS removal rate (%) = 100 × {1-(TDS concentration in permeate water/TDS concentration in feed water)}
(element differential pressure)
The upstream side (feed water side) and the downstream side (concentrated water side) of the cylindrical pressure vessel loaded with the separation membrane element are connected by piping via a Nagano Keiki differential pressure gauge (model DG16), and the element differential pressure during operation is measured. was measured. As for the operating conditions, the feed water flow rate was 9 L/min, the operating pressure was 1.0 MPa, and reverse osmosis membrane treated water was used as the feed water. In addition, after the air bubbles inside the element are removed, the cock of the permeated water piping is closed, and the operation is performed in a state in which membrane filtration cannot be performed substantially, that is, in a state in which all the feed water is discharged as concentrated water, and the element differential pressure (kPa ) was measured.
(Proportion of foulant adhesion on separation membrane surface and supply side channel material)
The separation membrane, the channel material on the feed side, and the channel material on the permeate side were placed in a transparent acrylic cell. After 12 hours of operation under these conditions, flushing was performed with an aqueous solution of 100 ppm of bovine serum albumin, which is not labeled with a fluorescent substance.

Thereafter, fluorescence observation was performed using a digital microscope Dino-Lite manufactured by Optoscience, and the adhesion area ratio (%) of the fluorescent substance deposited on the film surface and the channel material on the supply side was calculated using ImageJ.
(Fouling test)
The separation membrane element was placed in a pressure vessel, and using Lake Biwa water with a hardness of 46 ppm, an alkalinity of 42 ppm, a TDS of 95.89 ppm, a TOC of 2 ppm, and a pH of 7.0 as the feed water, the operating pressure was 0.5 MPa, and the temperature was 25°C. After running for 1 minute, sampling was performed for 1 minute, and the water permeation rate (gallon) per day at that time was obtained as the initial water production rate (GPD (gallon/day)). After that, continuous operation was performed for 4 weeks, and the amount of water produced after passing water (GPD) was obtained. From the initial amount of fresh water produced and the amount of fresh water produced after passing water,

and Note that the recovery rate was set to 50%.
(Example 1)
An evaluation cell was used for the prepared channel material on the supply side, and the separation membrane element was placed in a pressure vessel and evaluated under the conditions described above.
(Examples 2-8)
A separation membrane element was produced in the same manner as in Example 1, except that the channel materials on the supply side were as shown in Tables 1 and 2.

When the separation membrane element was placed in a pressure vessel and each performance was evaluated under the same conditions as in Example 1, the results are shown in Tables 1 and 2.
<Comparative example>
(Preparation of supply side channel material R)
Polypropylene is used as a material, and molten resin is supplied from an extruder while rotating two spinnerets on which a large number of holes are arranged, one on the inside and the other on the outside. A net having a rectangular shape was manufactured. By changing the molten resin discharge pressure from the extruder and the take-up speed, the structure was controlled so that the shape of the channel material on the supply side shown in Table 2 was finally obtained.
(Comparative example 1)
A separation membrane element was produced in the same manner as in Example 1, except that the channel material on the supply side was as shown in Table 2.

The separation membrane element was placed in a pressure vessel and each performance was evaluated under the conditions described above. Table 2 shows the results.
(Comparative Examples 2 and 3)
A separation membrane element was produced in the same manner as in Example 1, except that the channel material on the supply side was as shown in Table 2.
The separation membrane element was placed in a pressure vessel and each performance was evaluated under the conditions described above. Table 2 shows the results.

As is clear from the results shown in Tables 1 and 2, it can be said that the separation membrane elements of Examples 1 to 8 stably have excellent separation performance without impeding the flow of feed water.

On the other hand, in Comparative Example 1, although the intersecting point intervals in the direction perpendicular to and parallel to the flow direction of the supply water of the channel material on the supply side are the same as in Examples 1 and 2, the thread diameter at the central portion is large, so the supply side The flow area ratio was low, the element differential pressure was high, and the element water production and removal rate decreased. In addition, since there were many stagnation points, the amount of foulant adhered increased, and the rate of decrease in fresh water production increased.

The membrane element of the present invention is particularly suitable for use as an RO water purifier and for desalting brackish water and seawater.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the invention.

1 spiral separation membrane element 2 supply side channel material 2a to 2e supply side channel material 21 fibrous material A
22 fibrous material B
3 Separation membrane 4 Permeate-side channel material 5 Envelope-shaped membrane 6 Water collection pipe 7 Feed water 8 Permeate water 9 Concentrated water 10 10 cm × 10 cm × 3 mm aluminum plate c Vertical direction to the feed water flow direction of the feed-side channel material Intersection interval d Intersection interval P in the direction parallel to the supply water flow direction of the supply side channel material Intersection V Gap D Thickness of supply side channel material D _C Intersection thickness L _P perpendicular line L _T tangent line L _V Distance between the intersection point and the flat plate L _{V1 -} Larger distance between the intersection point and the flat plate L _V2 Smaller distance between the intersection point and the flat plate D ₁ Small diameter part thickness D ₂ Large diameter part thickness L ₁ Small diameter part Length L ₂ Large diameter part length

Claims (5)

A separation membrane element comprising at least a collection tube, a separation membrane, a feed-side channel material, and a permeate-side channel material,
The feed-side channel material is arranged between two surfaces of the separation membrane to form a feed-side channel, and the feed-side channel material is composed of a plurality of fibrous materials A arranged in one direction. Composed of a fibrous row X and a fibrous row Y composed of a plurality of fibrous materials B arranged in a direction different from the fibrous row X,
At least one of the fibrous material A and the fibrous material B has a large diameter part and a small diameter part, and the small diameter part of the fibrous material A or the fibrous material B and the other fibrous material At least one of the fibrous material A or the fibrous material B at at least one of the intersection points P has a gap V between the separation membrane and the separation membrane. 2. A separation membrane element, wherein the proportion of the voids V is 25% or more with respect to the number of intersections in the channel material on the supply side. Both the fibrous material A and the fibrous material B of the supply side channel material have a large diameter part and a small diameter part, and the fibrous material A and the fibrous material B intersect at the small diameter part. 2. The separation according to claim 1, wherein the fibrous material A and the fibrous material B at the intersecting point P have a void V between them and the separation membrane. membrane element. 3. The separation membrane element according to claim 1, wherein the thickness _D1 of the small diameter portion is 0.1 mm or more. 4. The separation membrane element according to any one of claims 1 to 3, wherein the voids V of the feed-side channel material are present at 75% or more of the number of intersections in the feed-side channel material. . A length ratio L ₁ /L ₂ is in the range of 0.1 to 15, where L ₁ is the length of the small diameter portion and L ₂ is the length of the large diameter portion. The separation membrane element according to any one of 1 to 4.

Images