Supply-side flow passage material for separation membrane element, separation membrane element, separation membrane module, and fluid separating device

Abstract

The present invention addresses the problem of providing a supply-side flow passage material for use in a separation membrane element capable of reducing membrane surface concentration polarization and fouling of a supply-side flow passage. The present invention provides a net-shaped supply-side flow passage material for a separation membrane element, a separation membrane element employing the same, a separation membrane module, and a fluid separating device, the supply-side flow passage material being configured from fibrous rows X configured from a plurality of fibrous materials A arranged in one direction, and fibrous rows Y configured from a plurality of fibrous materials B arranged in a direction different from the fibrous row X, and the fibrous rows X and the fibrous rows Y intersecting three-dimensionally at points of intersection, wherein the following conditions are satisfied: a thickness D of the supply-side flow passage material is 0.50 mm to 1.00 mm inclusive; an intersection angle An at the points of intersection is 70 degrees to 110 degrees inclusive; an inter-intersection distance TD between adjacent points of intersection is 1.50 mm to 2.80 mm inclusive; and a ratio SD / D of a side diameter SD of the fibrous material to the thickness D is 0.55 to 0.70 inclusive.

Description

Supply channel material for separation membrane element, separation membrane element, separation membrane module, and fluid separation device

[0001] The present invention relates to a separation membrane element for separating impurities from various liquids containing impurities, particularly to a separation membrane element used in the desalination of seawater, desalination of brine, production of ultrapure water, or wastewater treatment, as well as a supply-side flow channel material for a separation membrane element, a separation membrane element, a separation membrane module, and a fluid separation device.

[0002] In recent years, the use of separation methods using separation membrane elements has expanded in technologies for removing ionic substances contained in seawater and brine, as a process that conserves 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 their pore size and separation function. These membranes are used, for example, in the production of drinking water from seawater, brine, and water containing harmful substances, the production of industrial ultrapure water, and wastewater treatment and recovery of valuable materials, and are selected according to the target separation components and separation performance.

[0003] While separation membrane elements come in various forms, they all share the common feature of supplying raw water to one side of the separation membrane and obtaining permeate fluid from the other side. Separation membrane elements are designed to have a large membrane area per element, and therefore a large amount of permeate fluid obtained per element, by comprising a bundle of multiple separation membranes. Various shapes of separation membrane elements have been proposed, such as spiral type, hollow fiber type, plate and frame type, rotating flat membrane type, and flat membrane stacking type, depending on the application and purpose.

[0004] For example, spiral-type separation membrane elements are widely used in reverse osmosis filtration. A spiral-type separation membrane element comprises a water collection pipe and a separation membrane unit wound around the water collection pipe. The separation membrane unit is formed by stacking a supply-side flow channel material that supplies raw water (i.e., water to be treated) as feedwater to the surface of the separation membrane, a separation membrane that separates components contained in the raw water, and a permeate-side flow channel material that guides the permeate fluid separated from the supply-side fluid through the separation membrane to the water collection pipe. Spiral-type separation membrane elements are preferred because they can apply pressure to the raw water, thus allowing for the extraction of a large amount of permeate fluid.

[0005] When treating feedwater using a separation membrane element, membrane surface concentration polarization can occur, where dissolved substances such as salts in the feedwater form a concentration gradient along the direction perpendicular to the separation membrane. When membrane surface concentration polarization occurs, the membrane surface osmotic pressure increases, degrading the performance of the separation membrane element. In a separation membrane element, the driving force for permeation is the intermembrane pressure difference; therefore, increasing the intermembrane pressure difference is effective in improving the water production rate. The intermembrane pressure difference is expressed as the supply pressure to the separation membrane element minus the osmotic pressure and flow resistance. Therefore, to increase the intermembrane pressure difference, it is necessary to increase the supply pressure, decrease the membrane surface osmotic pressure, or decrease the flow resistance. Considering the case where the supply pressure is the same, to improve the water production rate, either the membrane surface osmotic pressure or the flow resistance should be decreased. To decrease the membrane surface osmotic pressure, it is important to increase the degree of turbulence around the fibrous material. This is because turbulence supplies feedwater that has not yet contacted the membrane to the separation membrane surface.

[0006] Furthermore, reducing the membrane surface concentration polarization reduces the salt concentration difference between the permeate side and the supply water side, thereby reducing salt diffusion and improving the desalination rate. Therefore, improving the performance of the separation membrane element using a supply-side flow channel material has been proposed.

[0007] Specifically, Patent Document 1 proposes a net in which the concentration polarization of the membrane surface is reduced by the repeating structure of spiral fibrous material in the supply-side channel material. Patent Document 2 proposes a channel material in which elliptical fibrous material and fibrous material with irregularly shaped cross-sections intersect in three dimensions. Patent Document 3 proposes a spiral-type membrane element equipped with a raw liquid channel material that can suppress concentration polarization.

[0008] Japanese Patent Publication No. 6693027, Japanese Unexamined Patent Publication No. 2015-205269, Japanese Unexamined Patent Publication No. 2000-153270

[0009] However, the supply channel material for the separation membrane element described above did not sufficiently reduce membrane surface concentration polarization or suppress fouling, and in some cases the separation membrane element was not able to fully demonstrate its performance.

[0010] Therefore, the present invention aims to provide a supply-side channel material for use in a separation membrane element that can reduce membrane surface concentration polarization and fouling in the supply-side channel.

[0011] To achieve the above object, the present invention is characterized by the following configurations (1) to (16). (1) A feed-side channel material for a separation membrane element having a net shape, comprising: fibrous rows X composed of a plurality of fibrous materials A arranged in one direction; and fibrous rows Y composed of a plurality of fibrous materials B arranged in a direction different from that of the fibrous rows X, wherein the fibrous rows X and the fibrous rows Y are three-dimensionally crossed at intersection portions, a thickness D of the feed-side channel material is 0.50 mm or more and 1.00 mm or less, an intersection angle An at the intersection portions is 70 degrees or more and 110 degrees or less, an inter-intersection distance TD between adjacent intersection portions is 1.50 mm or more and 2.80 mm or less, and a ratio SD / D of a side diameter SD of the fibrous material to the thickness D is 0.55 or more and 0.70 or less. (2) The feed-side channel material for a separation membrane element according to (1), wherein the ratio SD / D of the side diameter SD to the thickness D is 0.60 or more and 0.70 or less. (3) The feed-side channel material for a separation membrane element according to (1) or (2), wherein the inter-intersection distance TD is 1.50 mm or more and 2.40 mm or less. (4) The feed-side channel material for a separation membrane element according to (1) or (2), wherein the intersection angle An is 80 degrees or more and 110 degrees or less. (5) At least one cross section Z in a direction perpendicular to the longitudinal direction of the fibrous material A or the fibrous material B, wherein a straight line parallel to the plane of the feed-side channel material that bisects a circumscribed circle in contact with the cross section Z into upper and lower halves is drawn, and the cross section of the upper half of the cross section Z １ has an area S １ , the cross section of the lower half of the cross section Z ２ has an area S ２ , and when １ / S ２ is 0.20 or more and 0.90 or less, the ratio of the area S ２ to the area S ２ of a convex hull figure Z ３ surrounding the cross section Z ３ is S ２ / S ３ is 0.75 or more and 1.00 or less, and the ratio of the maximum vertical diameter D １ to the maximum horizontal diameter D ２ is D １ / D ２(1) or (2) The supply-side flow channel material for a separation membrane element, wherein the ratio S is 1.05 or more and 2.00 or less. (6) The ratio S ２ / S ３ (5) The supply-side flow channel material for a separation membrane element, wherein the ratio S is 0.90 or more and 1.00 or less. (7) The supply-side flow channel material for a separation membrane element, wherein the cross-sectional shape of the cross-section Z is teardrop-shaped. (8) The ratio S １ / S ２ (5) A supply-side flow channel material for a separation membrane element as described in (5), wherein the ratio S is 0.30 or more and 0.60 or less. (9) In the fibrous material A and the fibrous material B, in 50% or more of the cross-sectional surface Z other than the intersection portion, １ / S ２ The ratio S is 0.20 or more and 0.90 or less. ２ / S ３ The ratio D is 0.75 or more and 1.00 or less. １ / D ２ (5) A supply-side flow channel material for a separation membrane element according to (5), wherein the ratio is 1.05 or more and 2.00 or less. (10) A separation membrane element comprising at least a water collection pipe, a separation membrane, a supply-side flow channel material, and a permeate-side flow channel material, wherein the supply-side flow channel material is a supply-side flow channel material for a separation membrane element according to (1) or (2). (11) A separation membrane element according to (10), wherein the ratio H / D of the height H of the supply-side flow channel to the thickness D is 0.950 or more and 0.995 or less. (12) A separation membrane element according to (10), characterized in that it is used for treating feedwater with a salt concentration of 30,000 mg / L or more. (13) A separation membrane element according to (10), characterized in that it is used for producing ultrapure water. (14) A separation membrane element according to (10), characterized in that the length of the element is 20 inches or more. (15) A separation membrane module comprising a plurality of separation membrane elements according to (10) in a pressure vessel. (16) A fluid separation apparatus comprising the separation membrane element described in (10).

[0012] According to the present invention, by suppressing the generation of membrane surface concentration polarization and the accumulation of fouling, a separation membrane element with excellent operating performance, such as water permeability and desalination rate, can be obtained.

[0013] Figure 1 is a partially unfolded perspective view showing an example of a separation membrane element of the present invention. Figure 2(a) is a plan view showing an example of a supply-side flow channel material of the present invention. Figure 2(b) is a perspective view (top) and a cross-sectional view (bottom) showing an example of a supply-side flow channel material. Figure 3 is a plan view showing the configuration and definition of the supply-side flow channel material of the present invention. Figure 4 is a cross-sectional view showing the configuration and definition of the supply-side flow channel material of the present invention. Figure 5 is a diagram showing an overview of a method for measuring the flow channel height of a separation membrane element of the present invention. Figure 6 is a cross-sectional view showing an example of a supply-side flow channel material of the present invention. Figure 7 is a cross-sectional view showing an example of a cross-section Z of a fibrous material of the present invention and its convex hull. Figure 8 is a cross-sectional view showing an example of a supply-side flow channel material of the present invention. Figure 9 is a cross-sectional view showing an example of a cross-section of a supply-side flow channel material of the present invention. Figures 10(a) to (g) are cross-sectional views showing examples of supply-side flow channel materials of the present invention. Figures 11(a) to (d) are cross-sectional views showing other examples of supply-side flow channel materials of the present invention.

[0014] The embodiments of the present invention will be described in detail below.

[0015] In this specification, "mass" is synonymous with "weight." Furthermore, in this specification, "~" indicates that the values ​​before and after it are included as the lower and upper limits, respectively.

[0016] <Outline Description> In embodiments of the present invention, it is preferable that the separation membrane element comprises at least a water collection pipe, a separation membrane, a supply-side flow channel material, and a permeate-side flow channel material.

[0017] In the spiral-type separation membrane element 1 shown in Figure 1, a polymer net is used as the supply-side channel material 2 that forms the supply-side channel. Furthermore, tricot with a finer spacing than the supply-side channel material 2 is used as the permeate-side channel material 4 to prevent the separation membrane 3 from falling and to form the permeate-side channel. An envelope-shaped membrane 5 is formed by the permeate-side channel material 4 and the separation membrane 3, which is bonded to both sides of the permeate-side channel material 4 in an envelope shape. The inside of the envelope-shaped membrane 5 constitutes the permeate-side channel. The envelope-shaped membrane 5, which is alternately layered with the supply-side channel material 2, is bonded to the outer surface of the water collection pipe 6 at a predetermined portion on the opening side and spirally wrapped around it. The x-axis direction in Figure 1 is the longitudinal direction of the water collection pipe 6. The y-axis direction is perpendicular to the longitudinal direction of the water collection pipe 6.

[0018] In the spiral-type separation membrane element 1, the supply water 7 is typically supplied from one end face, and as the supply water 7 flows parallel to the water collection pipe 6, it is gradually separated into permeate water 8 and concentrated water 9. The permeate water 8 exits the spiral-type separation membrane element 1 from the opposite end face from which the supply water 7 is supplied.

[0019] In this system, the supply water 7 flows from one end face to the other end face of the spiral-type separation membrane element 1, so there is inevitably a sufficient distance in contact with the separation membrane 3, and as a result the supply water 7 is sufficiently separated into permeate water 8 and concentrated water 9.

[0020] <Supply-side flow channel material> (Configuration) As shown in Figures 2(a) and (b), the supply-side flow channel material of this embodiment is composed of a fibrous row X made up of a plurality of fibrous materials A (21) arranged in one direction, and a fibrous row Y made up of a plurality of fibrous materials B (22) arranged in a direction different from the fibrous row X, and the fibrous row X and the fibrous row Y intersect each other in three dimensions, forming intersections at multiple points, creating a net shape. The supply water supplied to the supply-side flow channel material, which is sandwiched between a pair of opposing separation membranes 3, passes through the gap between the fibrous materials B (22) and the separation membrane 3 where the fibrous materials A (21) and the separation membrane 3 are in contact, and passes through the gap between the fibrous materials A (21) and the separation membrane 3 where the fibrous materials B (22) and the separation membrane 3 are in contact, and generally proceeds through the supply-side flow channel material in a complex meandering manner, as shown in Figure 2(b).

[0021] In a separation membrane element, the driving force for filtration is the intermembrane pressure difference; therefore, increasing the intermembrane pressure difference is effective in improving water production. The intermembrane pressure difference is expressed as the supply pressure to the separation membrane element minus the flow resistance and osmotic pressure. Therefore, to increase the intermembrane pressure difference, it is necessary to either increase the supply pressure, decrease the flow resistance, or decrease the membrane surface osmotic pressure. Note that membrane surface osmotic pressure increases due to the occurrence of membrane surface concentration polarization.

[0022] The fibrous material A (21) and fibrous material B (22) in the supply-side flow channel material have the role of disturbing the supply water. Specifically, on the surface of the separation membrane 3 behind the fibrous material A (21) and fibrous material B (22) in the direction of supply water flow (membrane surface), vortices (flows) are generated in the supply water as the supply water meanders, which reduces areas where the supply water stagnates, suppresses the rise in salt concentration, and suppresses membrane surface concentration polarization. The size and flow velocity of the vortices generated around these fibrous materials change depending on the shape of the fibrous material A (21) and fibrous material B (22). When the vortices are large and the flow velocity is high, the supply water is disturbed on the membrane surface, reducing areas where the supply water stagnates and suppressing the rise in salt concentration.

[0023] In water treatment plants, lowering the operating pressure is crucial. Achieving the target water production volume at lower operating pressure reduces pump power costs, leading to cost savings. Lowering the operating pressure requires either reducing the flow resistance in the supply-side flow path or reducing the membrane surface concentration polarization. The magnitude of the differential pressure between the inlet and outlet of the separation membrane element is determined by the magnitude of the flow resistance. The inter-membrane differential pressure refers to the difference between the pressure on the supply water side and the pressure on the permeate side, while the differential pressure refers to the difference between the pressure on the supply water side and the concentrated water side of the separation membrane element.

[0024] Furthermore, disturbing the supply water at the membrane surface is also important from the perspective of preventing fouling. When concentration polarization increases around fibrous material A (21) and fibrous material B (22), the concentration of substrate, which is a nutrient source for microorganisms, tends to increase, making it easier for biofilms to form around the fibers. Therefore, by suppressing concentration polarization, the substrate concentration can be reduced, and the growth of biofilms can be suppressed. As a result, a reduction in water production and an increase in flow resistance can be prevented. In addition, when the vortices around fibrous material A (21) and fibrous material B (22) become larger, particles contained in the raw water (supply water) are less likely to accumulate, thereby suppressing fouling.

[0025] As shown in Figures 2(a)(b), 3, and 4, the supply-side flow channel material in this embodiment has a net shape in which a fibrous row X composed of a plurality of fibrous materials A arranged in one direction and a fibrous row Y composed of a plurality of fibrous materials B arranged in a direction different from the fibrous row X intersect each other in three dimensions at their intersections. The supply-side flow channel material in this embodiment is characterized in that the thickness D of the supply-side flow channel material is 0.50 mm or more and 1.00 mm or less, the intersection angle An at the intersections is 70 degrees or more and 110 degrees or less, the distance TD between adjacent intersections is 1.50 mm or more and 2.80 mm or less, and the ratio SD / D of the side diameter SD of the fibrous materials to the thickness D is 0.55 or more and 0.70 or less. By setting each parameter of the supply-side flow channel material to a value within the above range, the effect of suppressing concentration polarization outweighs the effect of flow resistance, and the operating pressure can be reduced. As a result, it becomes possible to operate the separation membrane element stably over a long period of time.

[0026] (Thickness) In this embodiment, the thickness D is 0.50 mm or more and 1.00 mm or less, preferably 0.60 mm or more and 0.90 mm or less. By setting the thickness D to 0.50 mm or more, preferably 0.60 mm or more, a sufficient supply-side flow path can be secured, blocking of the supply-side flow path by foulant can be suppressed, and pressure loss can be reduced. On the other hand, by setting the thickness D to 1.00 mm or less, preferably 0.90 mm or less, a separation membrane element with excellent volumetric efficiency can be provided.

[0027] The thickness D is determined by observing a longitudinal cross-section parallel to the fibrous rows using a commercially available microscope and measuring the distance. Specifically, ten arbitrary points on the thickness of the supply-side flow channel material at the intersection are extracted and measured using the measurement mode, and the average value is taken as the thickness D.

[0028] The variation in thickness D is preferably 0.85 times or more and 1.15 times or less of the average value obtained by the method described above. When the variation in thickness D is within this range, the supply water can be supplied uniformly to the separation membrane element, and the performance of the separation membrane can be uniformly exhibited. The "variation in thickness D" refers to the upper and lower limits of the variation of the 10 thickness measurements relative to the thickness D obtained from the average value as described above.

[0029] (Distance between intersections and intersection angle) The definitions of the distance between intersections TD and the intersection angle An are shown based on Figure 3. First, when observing the plane of the supply-side flow channel material, there are locations where fibrous material A (21) and fibrous material B (22) overlap and intersect in three dimensions (for example, C in Figure 3). １ and C ２ Let the points at the intersections be defined as follows. Next, let L be the line formed by connecting the diagonals of the quadrilateral (rhombus) composed of the four intersection points. In Figure 3, L is drawn so as to penetrate all the diagonals of the quadrilaterals (rhombuses) that are connected horizontally or vertically. Furthermore, the points where L intersects are defined as intersections. Then, two adjacent intersections (for example, P in Figure 3) are defined as intersections. １ and P ２The distance between the points ) is defined as the distance between intersections TD. On the other hand, the angle formed at an intersection adjacent to one intersection point, in a direction perpendicular to the flow direction of the supply water (for example, P in Figure 3) １ and P ２ The straight line connecting and P ２ and P ３ Let An be the intersection angle (the angle formed by the straight line connecting the two points).

[0030] In this embodiment, the intersection distance TD is 1.50 mm or more and 2.80 mm or less, preferably 1.50 mm or more and 2.40 mm or less, and more preferably 1.50 mm or more and 2.20 mm or less. By setting the intersection distance TD to 1.50 mm or more, it is possible to secure the membrane area necessary for separation and suppress the increase in flow resistance. On the other hand, by setting the intersection distance TD to 2.80 mm or less, preferably 2.40 mm or less, and more preferably 2.20 mm or less, it is possible to suppress the phenomenon of the separation membrane falling into the void portion of the supply-side flow channel material when the separation membrane element is manufactured, and in particular, it is possible to stably form the flow channel at the end face portion on the side into which the supply water flows.

[0031] In this embodiment, the intersection angle An is 70 degrees or more and 110 degrees or less, preferably 80 degrees or more and 110 degrees or less. Based on the plan view of the supply-side flow channel material shown in Figure 3, as the angle between the flow direction of the supply water (the longitudinal direction of the water collection pipe in Figure 1) and the fibrous material A (21) and the fibrous material B (22) (intersection angle An) increases, the turbulence intensity increases, but the flow resistance tends to increase as well. By setting the intersection angle An to 70 degrees or more, preferably 80 degrees or more, the turbulence intensity can be increased. On the other hand, by setting the intersection angle An to 110 degrees or less, the flow resistance can be suppressed. In other words, by setting the intersection angle An within the above range, the supply water is moderately disturbed at the membrane surface of the separation membrane, the areas of stagnation are reduced, and the increase in salt concentration can be suppressed.

[0032] The intersection distance TD and intersection angle An can be measured and calculated using a commercially available microscope. For example, the intersection distance TD can be calculated by measuring the distance between 10 arbitrarily selected "two intersection points" based on images obtained from a commercially available microscope, and then calculating the average value. On the other hand, the intersection angle An can be calculated by pasting images taken with a commercially available microscope into Microsoft PowerPoint, then arbitrarily selecting 10 points from the angles of the quadrilateral (rhombus) that can be drawn at the four intersection points in Figure 3, measuring the angles formed at intersections adjacent to one of the intersection points and facing each other in a direction perpendicular to the direction of the water supply flow, and then calculating the average value.

[0033] (Ratio of side diameter SD to thickness D) In ​​the embodiment of the present invention, the ratio SD / D of the side diameter SD to the thickness D is 0.55 or more and 0.70 or less, preferably 0.60 or more and 0.70 or less. By setting the ratio SD / D to 0.55 or more, preferably 0.60 or more, the fibrous material A (21) and fibrous material B (22) sufficiently disturb the flow of the supply water, thereby suppressing membrane surface concentration polarization. On the other hand, by setting the ratio SD / D to 0.70 or less, the supply flow path can be secured, and the increase in flow resistance in the supply side flow path can be suppressed. The ratio SD / D can be adjusted to the above range by increasing the side diameter SD and causing the fibrous material A (21) and fibrous material B (22) to interlock with each other, while maintaining the thickness D, and adjusting the ratio of the side diameter SD to the thickness D.

[0034] The side diameter SD is determined by observing a longitudinal cross-section parallel to either the fibrous material A (21) or the fibrous material B (22) using a commercially available microscope, and measuring the diameter of the fibrous material A (21) or fibrous material B (22) in a direction perpendicular to the plane of the supply-side flow channel material, excluding the intersection. For example, when measuring the side diameter SD of the fibrous material A (21) as shown in Figure 4, a location excluding the fibrous material B (22) at two adjacent intersections is specified, and 11 lines are drawn to divide this location into 10 sections. The diameter of the fibrous material along these 11 lines is then measured using the measurement mode. This operation is performed similarly for 9 other arbitrary locations (10 locations in total) that are divided into 10 sections, and the average value of the total 110 measured values ​​is taken as the side diameter SD. Then, the ratio SD / D is calculated using the measured thickness D and the side diameter SD.

[0035] (Ratio of supply-side channel height H to thickness D) In ​​the embodiment of the present invention, the ratio H / D of the supply-side channel height H to the thickness D is preferably 0.950 or more and 0.995 or less. As shown in Figure 5, in this embodiment, when the supply-side channel material 2 is placed between the two surfaces of the separation membrane 3, it forms a supply-side channel F as a gap. Therefore, if the separation membrane 3 deforms and excessive membrane recession (deformation that narrows the channel) occurs relative to the supply-side channel material 2, there is a concern that the supply-side channel F, which is the channel for the supply water, will become narrower than initially designed. By setting the ratio H / D to 0.950 or more, deformation of the supply-side channel F can be reduced, and the accumulation of fouling that occurs in the deformed area can be suppressed. On the other hand, by setting the ratio H / D to 0.995 or less, the separation membrane 3 is in a state where it is moderately recessed relative to the supply-side channel material 2, and a force acts on the supply-side channel material 2 to grip both separation membranes 3, reducing the risk that the supply-side channel material 2 will pop out from between the two surfaces of the separation membrane 3 during operation. In addition to adjusting the distance between intersections, the HD / D ratio can also be controlled by adjusting the winding pressure when winding the spiral-type separation membrane element.

[0036] The supply-side channel height H can be measured using an X-ray CT scanner. For example, in the case of a spiral-type separation membrane element 1, first, as shown in Figure 5(a), the water collection pipe 6 is cut perpendicular to its longitudinal direction. Then, a straight line CL is set connecting the center of the water collection pipe 6 to an arbitrary outer circumference, and a rectangular cross-section consisting of the supply-side channel material 2 and the supply-side channel F sandwiched between two layers of separation membrane 3 is set with this straight line CL as the central axis, and this is designated as the object of analysis. When the object of analysis is analyzed with an X-ray CT scanner, the supply-side channel F shown in the cross-sectional perspective view in Figure 5(b) and the cross-sectional transmission perspective view in Figure 5(c) is displayed in black. After that, areas that are highly likely to have been damaged during cutting are excluded, and the analysis range is set. Specifically, as shown in Figure 5(d), regarding the depth, the area up to 2 inches from the cut surface in the longitudinal direction of the water collection pipe 6 is excluded from the analysis range, and the area from 2 inches to 4 inches from the cut surface in the longitudinal direction of the water collection pipe 6 is set as the analysis range. For example, in the case of an 8-inch spiral-type separation membrane element 1, the analysis range is defined as a rectangular parallelepiped with a cross-section of 4.2 inches vertically and 1 inch horizontally, centered on the straight line CL and tangent to the center point of the water collection pipe 6, multiplied by the depth of 2 inches within the aforementioned range. Within this range, the volume of the supply-side flow channel F (the area shown in black when analyzed by an X-ray CT scanner) is measured for each layer consisting of the supply-side flow channel material 2 and the supply-side flow channel F, and defined as the spatial volume. Here, in the case of a spiral-type separation membrane element 1 with a diameter smaller than 8 inches, the analysis range is fixed at a depth of 2 inches within the aforementioned range, and the vertical and horizontal ranges are reduced by multiplying by a ratio corresponding to the diameter. For example, in the case of a 4-inch spiral-type separation membrane element 1, multiplying by 4 / 8 (= 1 / 2) results in a vertical of 2.1 inches and a horizontal of 0.5 inches. The spiral-type separation membrane element 1 can be cut in any way that does not disrupt the flow channel structure within the aforementioned range in terms of depth, such as a disc grinder, water jet cutter, or band saw.

[0037] Using the spatial volume of each layer of the supply channel F obtained by the method described above, and the occupancy rate of the supply channel F in the space consisting of the supply channel material 2 and the supply channel F (hereinafter abbreviated as "supply channel occupancy rate," the calculation formula is described later), the supply channel height H of each layer is calculated using the following formula: Supply channel height H = Spatial volume / (Arc length × Depth × Supply channel occupancy rate) The occupancy rate of the supply channel F can be determined by the following method. First, the supply channel material 2 is cut to a size of 50 cm × 50 cm, its weight is measured, and the weight per unit area (kg / m) is calculated. ２ Next, calculate the weight per unit volume (kg / m³). Then, divide this calculated value by the thickness of the supply-side flow channel material 2 to obtain the weight per unit volume (kg / m³). ３ ) is calculated. Finally, the density (kg / m³) of fibrous material A (21) and fibrous material B (22) is calculated from the following formula (1). ３ The occupancy rate of the supply channel F is calculated using the material density. Occupancy rate of the supply channel = 1 - (weight per unit volume / material density) ... (1) In this way, by sampling (cutting) the supply channel material 2 from the separation membrane element, the occupancy rate of the supply channel F is determined by freeing it from the appropriate membrane depression of the separation membrane 3, and by calculating the supply channel height H from the volume of the supply channel F in the state where the aforementioned membrane depression exists, the degree of deformation of the supply channel F, which has been deformed by the appropriate membrane depression of the separation membrane 3, is reflected in the supply channel height H.

[0038] When measuring the supply-side channel height H, if one end of the channel touches the central pipe or the outer filament winding within the range cut off by the rectangular parallelepiped, the channel volume will be underestimated. Therefore, channels that touch the central pipe or the outer filament winding at one end are excluded from the measurement of the supply-side channel height H, and only channels that are cut off at both ends by the long side of the rectangular parallelepiped are considered valid. The number of channels varies depending on the number of leaves of the spiral-type separation membrane element. As an example, in the case of Figure 5, which consists of 61 layers, the supply-side channel height H as defined by this invention will be the average value of the supply-side channel height H of all channels that are valid for measurement within the analysis range (i.e., 59 layers excluding channels that touch the central pipe or the outer filament winding at one end).

[0039] Furthermore, as shown in the embodiment described later, when two cross-sections are set, two analysis ranges are also set based on both cross-sections, and the average value of the supply-side flow path height obtained from each analysis range can be taken as the supply-side flow path height H.

[0040] (Angle between the flow direction of the supply water and the fibrous material) In Figure 2(a), which shows the supply side flow channel material observed from a plane, the turbulence intensity increases as the angle between the flow direction of the supply water (i.e., the longitudinal direction of the water collection pipe) and the fibrous material A (21) and fibrous material B (22) increases, but the flow resistance tends to increase. Therefore, the angle is preferably between 35 degrees and 55 degrees. Since this angle corresponds to half of the intersection angle An, the preferred range of this angle also corresponds to half of the lower limit (70 degrees) to half of the upper limit (110 degrees) of the intersection angle An.

[0041] (Cross-sectional shape of fibrous material) As shown in Figure 6, a circumscribed circle C is drawn on the cross-section Z perpendicular to the longitudinal direction of the fibrous material A or B, and a straight line L bisects the circumscribed circle C in a direction parallel to the plane of the supply-side flow channel material. Ｃ By drawing the cross-section Z, the upper half of the cross-section Z is divided into two parts. １ , and the lower half Z ２ The cross-sectional areas are S １ S ２ In this case, the ratio S of at least one of the cross-sectional planes Z １ / S ２ However, it is preferable that the ratio is between 0.20 and 0.90, and more preferably between 0.30 and 0.60. １ / S ２ By setting the ratio S to preferably 0.90 or less, and more preferably 0.60 or less, the fluid flow upon contact with the fibrous material becomes smoother, and the vortex velocity can be improved. On the other hand, ratio S １ / S ２ By preferably setting this to 0.20 or higher, and more preferably to 0.30 or higher, a large vortex can be generated. When the vortex is large and the flow velocity is high, the supply water is moderately disturbed on the membrane surface of the separation membrane 3, the area of ​​stagnation is reduced, and the increase in salt concentration can be suppressed. Note that in this invention, the upper half of the cross-section Z １This refers to the side of the fibrous material that faces the center of the flow path in the supply channel, and the lower half Z ２ This refers to the side where the fibrous material is closer to the supply side surface of the separation membrane 3.

[0042] In the present invention, "convex hull" refers to a figure that covers adjacent convex polygons without any indentations, and as shown in Figure 7(a), it refers to the convex figure with the smallest area (convex hull figure 12) that is circumscribed around the cross-section of the fibrous material 11, which is a convex polygon.

[0043] In an embodiment of the present invention, the lower half of the cross-section Z is defined as the cross-section Z in the procedure shown in Figure 7(b) ２ (See Figure 7(c)) The convex hull shape Z is made without a concave shape as shown in Figure 7(d). ３ (Cross-sectional area is S) ３ When covered with ), at least one ratio S of the cross-section Z ２ / S ３ However, it is preferable that it be 0.75 or more and 1.00 or less, and more preferably 0.90 or more and 1.00 or less. This preferred shape means that the indentation in the cross-section on the side adjacent to the separation membrane surface is small, and ratio S ２ / S ３ When it is 1.00, it means the cross-section Z ２ This means it has an ideal shape with no indentations. ２ / S ３ By setting this value to preferably 0.75 or higher, and more preferably 0.90 or higher, the amount of stagnation around the fibers is reduced, which suppresses concentration polarization and fouling.

[0044] In this embodiment, as shown in Figure 8, the maximum vertical diameter in the cross-section Z is D １ , the maximum horizontal diameter is D ２ In this case, the ratio D of at least one of the cross-sectional planes Z １ / D ２ It is preferable that it is between 1.05 and 2.00. １ / D ２By preferably setting this to 1.05 or higher, the flow is stirred up, allowing the supply water to be sufficiently agitated, thereby suppressing concentration polarization and improving the water production rate and desalination rate. In addition, the amount of resin used can be reduced compared to supply-side flow channel materials of the same vertical diameter, reducing pressure loss and lowering costs. On the other hand, D １ / D ２ By preferably setting this to 2.00 or less, the fiber shape is stabilized and rigidity is ensured, thereby improving productivity and durability during long-term use.

[0045] Thus, in this embodiment, when the cross-section Z of the fibrous material A (21) or fibrous material B (22) of the supply-side flow channel material is divided into two equal parts vertically based on its circumscribed circle, at least one of the cross-sections Z is the one that is closer to the supply-side surface of the separation membrane 3 (Z ２ (corresponding to) and the side facing the center of the flow path of the supply side (Z １ It was discovered that there is a suitable cross-sectional shape for each (corresponding to the specific characteristics).

[0046] In the embodiment of the present invention, in 50% or more, preferably 70% or more, of the cross-sectional surface Z of the supply-side flow channel material other than the intersection portion, ratio S １ / S ２ The ratio S is 0.20 or more and 0.90 or less. ２ / S ３ The ratio D is 0.75 or more and 1.00 or less. １ / D ２ It is preferable that the ratio is between 1.05 and 2.00. One method for controlling this ratio is to control it by balancing the rotational speed of the nozzle and the withdrawal speed. In this invention, for example, "in 50% or more of the cross-sectional surface Z, the ratio S １ / S ２ "It is 0.20 or higher" means that the ratio S was measured at 30 locations. １ / S ２ Not only is the average value of 0.20 or higher, but there are also 15 or more ratio S values ​​to eliminate the influence of the presence of singularities. １ / S ２ This means that the ratio S is also 0.20 or higher. ２ / S ３and ratio D １ / D ２ , the same shall apply in accordance with the description of the ratio S １ / S ２ described above.

[0047] In this embodiment, the positional vertical relationship in the cross section Z is defined such that, in FIG. 2(b), the side where fibrous material A (21) and fibrous material B (22) each abut against separation membrane 3 is defined as the lower side, and the side where the fibrous material does not abut against separation membrane 3 is defined as the upper side.

[0048] In this embodiment, the area S1 of the upper half cross-section Z １ and the area S2 of the lower half cross-section Z ２ can be obtained as follows. As shown in FIG. 7, a circumscribed circle in contact with the cross section Z of fibrous material 11 is drawn, and a straight line L that is parallel to the supply-side surface of the adjacent separation membrane 3 and overlaps the diameter that bisects the circumscribed circle vertically is drawn Ｃ , thereby dividing the cross section Z into the cross section Z １ of the upper half (the side not in contact with separation membrane 3) and the cross section Z ２ of the lower half (the side in contact with separation membrane 3). Thereafter, the area S １ of the cross-section Z １ and the area S ２ of the cross-section Z ２ are calculated by using existing image processing such as binarization.

[0049] In this embodiment, the maximum vertical diameter D １ is, as shown in FIG. 8 and FIG. 9, the maximum fiber diameter in the direction perpendicular to the plane of the supply-side channel material in the cross section Z for both fibrous material A (21) and fibrous material B (22), and the maximum horizontal diameter D ２ is the maximum fiber diameter in the direction parallel to the plane of the supply-side channel material in the cross section Z.

[0050] In this invention, the cross-sectional shape of fibrous material can be varied by, for example, changing the shape of the nozzle hole as needed. To create a vertically elongated cross-sectional shape, the rectangular discharge hole can be made vertically elongated. In particular, since resin tends to shrink due to surface tension after discharge, the nozzle hole shape can be made larger to account for this, or a water tank can be used for cooling and solidification. However, by reducing the distance between the nozzle and the water tank and speeding up the cooling and solidification process, the shape of the cross-section after discharge can be maintained. To create a cross-section with a depression in the lower half, a portion of the rectangular discharge hole can be cut off, preventing resin from being discharged from the cut-off portion and allowing the formation of a cross-section with a depression. In addition, the cross-sectional shape can be controlled by molding conditions such as the nozzle hole shape and discharge pressure.

[0051] Examples of cross-sectional shapes in this embodiment are shown in Figures 10(a) to (g). For example, an undeformed teardrop shape as shown in Figures 10(a) and 10(b), a shape like Figure 10(c) which is a partial defect of the shapes in Figures 10(a) and 10(b), or a shape like Figures 10(d) and 10(e) which have protrusions in addition to the shapes in Figures 10(a) and 10(b). However, if the only difference is the presence or absence of protrusions, it is preferable to have no protrusions because solid dirt is less likely to accumulate and fouling is suppressed. Also, the upper protrusions may be curved, as shown in Figures 10(f) and 10(g). The reason why a teardrop shape is preferable for the cross-sectional shape is that when fibers and fluid collide, the fluid is swirled upwards, but if the shape is tapered like a teardrop, vortices are more easily formed around the fibers, and the concentration polarization suppression effect is greater.

[0052] In this embodiment, the term "teardrop shape" refers to all the shapes shown in Figures 10(a) to (g). Specifically, it refers to a shape in which the lower part is arc-shaped, the central angle of the arc is 180 degrees or less, the upper part has a projection, the projection is connected to a straight line connecting the two ends of the arc, and the tip of the projection is curved. The lower part is the base of the teardrop shape and refers to the arc-shaped portion. The central angle of the arc is 180 degrees or less and forms the widest part of the teardrop shape. The two ends of the arc indicate the points of maximum width of the teardrop shape. A smaller arc angle results in a smaller width of the teardrop shape, and a larger angle results in a larger width of the teardrop shape. The upper part is the tip of the teardrop shape and refers to the portion with the projection. The projection is connected to a straight line connecting the two ends of the arc, and the tip of the projection is curved.

[0053] Examples of other cross-sectional shapes of the supply-side flow channel material in this embodiment are shown in Figures 11(a) to 11(d). Examples include a circular shape as shown in Figure 11(a), a shape with a flat top as shown in Figure 11(b), a shape with two depressions on the membrane surface side as shown in Figure 11(c), and a star-like shape as shown in Figure 11(d).

[0054] (Material) The material of the supply-side channel material is not particularly limited, but thermoplastic resin is preferred from the viewpoint of moldability. Among these, polyethylene and polypropylene are preferred because they do not easily damage the surface of the separation membrane and are inexpensive. Furthermore, the supply-side channel material may be formed from the same material for fibrous material A and fibrous material B, or from different materials. Additives may also be added.

[0055] (Manufacturing Method) An example of a method for forming a net-like supply channel material is shown. First, molten resin is supplied from an extruder while rotating two dies, an inner and an outer die, which have numerous holes arranged around their circumference, in opposite directions. At the moment the resin is discharged from the dies, or immediately afterward, the thread-like resin discharged from the inner die and the thread-like resin discharged from the outer die are crossed in their molten state to create a tubular net with a mesh structure. After that, the thickness, thread diameter, and intersection spacing are adjusted to desired values ​​by adjusting the cooling and solidification conditions, and then the tubular net is cut open to obtain a sheet-like net supply channel material.

[0056] As in this embodiment, to manufacture a supply-side flow channel material with controlled fibrous structure and cross-section, one method involves designing the hole shapes of two nozzles, an inner and an outer nozzle, which have numerous holes arranged around their circumference, to a desired shape, and supplying the resin while adjusting the discharge pressure and rotating them in opposite directions.

[0057] The morphology of the fibrous material in this invention can be adjusted by changing the discharge pressure, the shape of the nozzle holes, the cooling and solidification conditions (such as time), and other conditions as described above. For example, the thickness D of the supply-side flow channel material can be adjusted by changing the size of the nozzle holes and the discharge pressure, the intersection angle An can be adjusted by changing the rotation speed of the nozzle and the discharge pressure, and the distance TD between intersections can be adjusted by changing the spacing of the nozzle holes and the rotation speed. Furthermore, to increase the ratio SD / D, the amount of resin discharged can be reduced at the timing when intersections are formed (the timing when fibrous material A and fibrous material B intersect with each other, or when the outer and inner sides of nozzles rotating in opposite directions intersect), and the amount of resin discharged can be increased at the timing when fibrous material is formed between intersections. Maximum vertical diameter D of the cross-section Z １ and maximum horizontal diameter D ２ Ratio D １ / D ２ This can be adjusted by changing the shape of the nozzle hole as needed. For example, by making a rectangular discharge hole elongated vertically, a vertically elongated cross-sectional shape can be formed. In particular, since resin tends to shrink due to surface tension after discharge, the diameter of the fibrous material can be easily adjusted to a desired range by taking this into account and making the nozzle hole larger, or by shortening the distance between the nozzle and the water tank when using a water tank for cooling and solidification to speed up the cooling and solidification process, thereby maintaining the cross-sectional shape after discharge.

[0058] The methods for manufacturing the net-like supply-side channel material of this embodiment are not limited to those described above. Other methods include compressing and deforming fibrous material between intersections by embossing, imprinting, or pressing, casting molten resin into a mold and removing it, and using a 3D printer.

[0059] <Separation Membrane Element> (Permeation-side channel material) In the envelope-shaped membrane 5 of Figure 1, the separation membranes 3 are overlapped with their permeation-side surfaces facing each other, and a permeation-side channel material 4 is placed between the separation membranes 3, forming a permeation-side channel. The material of the permeation-side channel material 4 is not limited, and tricot, nonwoven fabric, porous sheet with protrusions fixed to it, film with uneven surface molding and perforation processing, and uneven nonwoven fabric can be used. In addition, protrusions that function as the permeation-side channel material 4 may be fixed to the permeation side of the separation membrane 3.

[0060] In particular, using tricot manufactured by a circular knitting machine as the permeate channel material 4 is preferable because it allows the width of the needle loop and the sinker loop to be made almost the same, so that both loops can be used as channels, and an optimal channel width that takes into account the membrane drop during operation of the separation membrane element can be uniformly manufactured, and furthermore, a permeate channel material 4 that can improve the amount of permeated fluid can be manufactured, even if it is thin, as it has sufficient pressure resistance and flow characteristics.

[0061] When the permeable channel material 4 is tricot, the fiber diameter of the fibers constituting the tricot is preferably 30 μm or more and 300 μm or less. By setting the fiber diameter of the tricot to 30 μm or more, the rigidity of the tricot body can be ensured. On the other hand, by setting the fiber diameter of the tricot to 300 μm or less, the pressure resistance of the permeable channel material 4 can be compensated for.

[0062] The thickness of the permeate-side channel material 4 is preferably 50 μm or more and 800 μm or less, and more preferably 100 μm or more and 500 μm or less. By setting the thickness of the permeate-side channel material 4 to preferably 800 μm or less, and more preferably 500 μm or less, the number of separation membrane leaves that can be packed into one vessel can be increased. On the other hand, by setting the thickness of the permeate-side channel material 4 to preferably 50 μm or more, and more preferably 100 μm or more, the flow resistance can be made relatively small, and good separation characteristics and permeation performance can be obtained.

[0063] (Length of separation membrane element) In the case of spiral-type separation membrane elements, the length of the separation membrane element commonly used is typically 12 to 40 inches. The longer the distance from the supply water inlet to the concentrated water outlet, the higher the salt concentration on the concentrated water side and the slower the flow velocity, thus increasing the effect of concentration polarization. Therefore, the longer the element length, the greater the benefit of the concentration polarization suppression effect of this embodiment. Specifically, the effect of the present invention becomes particularly pronounced in separation membrane elements with a length of 20 inches or more. Furthermore, the benefits of this embodiment are especially great in separation membrane modules equipped with multiple separation membrane elements in series inside a pressure vessel.

[0064] <Method for manufacturing a spiral-type separation membrane element> (Formation of separation membrane leaf) The separation membrane leaf may be formed by sandwiching a supply-side flow channel material between the separation membranes and folding the separation membranes so that the supply-side surfaces face inward, or by overlapping two separate separation membranes so that their supply-side surfaces face each other and sealing the periphery of the separation membranes.

[0065] Methods for "sealing" include bonding with adhesives or hot melts, fusion by heating or lasers, and integration by sandwiching a rubber sheet. Among these, sealing by bonding is the simplest and most effective, and therefore particularly preferred.

[0066] (Formation of spiral-type separation membrane element) A spiral-type separation membrane element can be constructed by alternately layering separation membrane leaves and permeable channel material on a base permeable channel material attached to a central pipe, while applying adhesive, and winding them around. At this time, the thickness of the supply channel can be adjusted by appropriately selecting the tension during winding, the thickness of the components, and the type of material.

[0067] (Additional steps) The spiral-shaped separation membrane element configured as described above may have a film and filament wrapped around it further, or end plates may be attached to it further.

[0068] <Use of Spiral-Type Separation Membrane Elements> Multiple spiral-type separation membrane elements can be connected in series or parallel and housed in a pressure vessel to form a separation membrane module. The number of elements connected is not particularly limited, but in the case of series connections, a configuration of two to seven elements is preferably used.

[0069] Furthermore, the spiral-type separation membrane elements and separation membrane modules described above can be combined with a pump to supply fluid to them, a device to pre-treat the fluid, and other components to constitute a fluid separation device. By using this separation device, for example, feedwater can be separated into permeate water such as drinking water and concentrated water that did not permeate the membrane, thereby obtaining water suitable for the purpose.

[0070] While a higher operating pressure for a fluid separation device improves the removal rate, it also increases the energy required for operation. Furthermore, considering the maintenance of the supply and permeate channels of the separation membrane element, the operating pressure when supplying water to the separation membrane module is preferably between 0.2 MPa and 6 MPa. However, for zero-deadwater (ZLD) applications, the operating pressure needs to be even higher.

[0071] While a higher supply water temperature reduces the salt removal rate, a lower temperature also reduces the membrane permeation flux, which is the permeate obtained by passing through the separation membrane per unit time. Therefore, a temperature of 5°C to 45°C is preferable.

[0072] Furthermore, if the pH of the raw water (supply water) is in the neutral range, even if the raw water is a highly saline liquid such as seawater, the formation of scale (precipitation of inorganic salts) such as magnesium is suppressed, and the deterioration of the separation membrane is also suppressed.

[0073] The water supplied to the separation membrane element in this embodiment is not particularly limited and may be pre-treated tap water, or it may be water with many impurities in the solution, such as seawater, brine, or wastewater. For example, when used for water treatment, the raw water (supply water) may be a liquid mixture containing 500 mg / L to 100 g / L of TDS (Total Dissolved Solids), such as seawater, brine, or wastewater. TDS refers to total dissolved solids and is expressed as "mass ÷ volume," but it is sometimes expressed as a "weight ratio" with 1 L considered as 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 a simpler method is to convert it from the practical salinity (S).

[0074] The spiral-type separation membrane element of this embodiment is suitably used for treating feedwater with a feedwater concentration of 30,000 mg / L or higher. Since the effect of concentration polarization becomes greater when the salinity of the feedwater is high, a significant reduction in operating pressure can be achieved.

[0075] Furthermore, the spiral-type separation membrane element of this embodiment is suitably used for ultrapure water production. In ultrapure water production, a high removal rate is required not only for salt removal but also for neutral molecules such as silica and boron. The spiral-type separation membrane element using the supply-side flow channel material of this embodiment is particularly suitable because it can suppress membrane surface concentration polarization. Also, scale is formed when the salt concentration near the separation membrane surface increases and exceeds the saturation dissolution amount, but since the spiral-type separation membrane element using the supply-side flow channel material of this embodiment can suppress concentration polarization, scale formation can be reduced.

[0076] The turbidity of the feedwater should preferably be 50 degrees (formazin) or less. In typical water treatment plants, pretreatment such as sand filtration or UF membrane treatment is performed, so the turbidity is low and does not pose a problem. By using pretreated feedwater with relatively low turbidity, it is possible to increase the water production volume while keeping the operating pressure low, even if the side diameter of the fibrous material is large.

[0077] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the descriptions in these examples.

[0078] <Measurement Method and Calculation Method> (Thickness D of the supply-side flow channel material) Using a Keyence VHX1000 digital microscope, the ultra-compact high-performance zoom lens VH-Z20T was set to 50x magnification, and the longitudinal cross-section parallel to the fibrous rows of the net-like sample was observed in accordance with the above description. The thickness of 10 arbitrary intersection points was extracted and measured, and the average value was calculated to be the thickness D of the supply-side flow channel material.

[0079] (Side diameter SD of fibrous material) Using a Keyence VHX1000 digital microscope, with the ultra-compact high-performance zoom lens VH-Z20T set to 50x magnification, the ratio SD / D of the side diameter SD to the thickness D of the supply-side flow channel material was obtained by observing the net-like sample from a longitudinal section parallel to the fibrous rows, in accordance with the description above.

[0080] (Intersection distance) Using a Keyence VHX1000 digital microscope, with the ultra-compact high-performance zoom lens VH-Z20T set to 20x magnification, the intersection distance TD was obtained by observing the net-like sample from a direction perpendicular to the plane, as described above.

[0081] (Intersection Angle An) Using a Keyence VHX1000 digital microscope, with the ultra-compact high-performance zoom lens VH-Z20T set to 20x magnification, the intersection angle An was obtained by observing the net-like sample from a direction perpendicular to the plane, as described above.

[0082] (Cross-sectional area of ​​the supply-side flow channel material) An arbitrary fiber was extracted from the net-like sample, cut perpendicular to the longitudinal direction of the fibrous material using a sharp blade, and observed using a Keyence VHX1000 digital microscope with a miniature high-performance zoom lens VH-Z20T set to 200x magnification, according to the description above, and the cross-section was photographed. Processing was performed using ImageJ ver. 1.45 (developed by Wayne Rasband, National Institutes of Health, NIH). First, the Medium filter was selected to remove noise. Next, Find Edges was selected to extract the contours. The bit depth was changed to 8 bits, and Max Entropy and B&W were selected in Threhold to perform binarization. Save the image, trace the cross-section extracted using Microsoft PowerPoint with a freeform tool, and then define the Z-section. １ Z ２ Z ３ Created S １ / S ２ S ２ / S ３ The created cross-section Z １ and Z ２ Z ２ and Z ３ Each element was grouped and saved as an image, which was then analyzed using ImageJ. The saved images were opened in ImageJ, and the thresholds for Threhold's Default and Red were set from 0 to 240. In Analysis Particle, Size was set to 0-Infinity and Circularity to 0.00-1.00, thus achieving the desired S results as described above. １ S ２ S ３ The cross-sectional area of ​​30 locations corresponding to this was measured, and the average value was used for each example and comparative example. １ S ２ S ３ It was calculated as follows.

[0083] (Cross-sectional thread diameter of the supply-side flow channel material) An arbitrary fiber is extracted from the net-like sample, cut perpendicular to the longitudinal direction of the fibrous material, and observed using a Keyence VHX1000 digital microscope, and D is determined according to the above description.１ and D ２ The cross-sectional thread diameters at 30 locations corresponding to this were measured and their ratios were calculated, and the average values ​​were used for each example and comparative example D １ , D ２ and D １ / D ２ It was calculated as follows.

[0084] (Ratio of supply-side channel height H to supply-side channel material thickness D) An 8-inch diameter, 40-inch long spiral separation membrane element was cut at 6 inches and 12 inches from one end in a direction perpendicular to the longitudinal direction of the water collection tube, and a 6-inch long cylindrical sample was cut out. The cylindrical sample was then dried in a vacuum oven set to 40°C until there was no change in weight. To avoid disrupting the channel structure, adhesive was applied to the entire cut surface of the cylindrical sample, and the adhesive was slightly impregnated into the end of the element. After curing, the cylindrical sample was further cut into a 60-degree fan shape with the water collection tube as the central axis. The fan-shaped sample was then dried in a vacuum oven set to 40°C until there was no change in weight. A GE Phoenix v |tome| x m300 X-ray CT scanner was used to scan and obtain a 3D image under the conditions of a tube current of 100 μA, a tube voltage of 150 kV, and a resolution of 19.8 μm. Subsequently, using VGSTUDIO MAX manufactured by VOLUMEGRAPHICS, the supply-side channel height for each example and comparative example was obtained in accordance with the description above, using the analysis range of 2 to 4 inches in the depth direction (parallel to the longitudinal direction of the water collection pipe) for the cut surface 6 inches from the end when the fan-shaped sample was cut into a cylindrical sample. Similarly, the supply-side channel height for each example and comparative example was obtained using the analysis range of 2 to 4 inches in the depth direction from the cut surface 12 inches from the end when the fan-shaped sample was cut into a cylindrical sample. In this example, the average value of these two supply-side channel heights was defined as the supply-side channel height H as defined by the present invention. In addition, in this embodiment, as a guarantee that the flow channel structure in the analyzed area was not damaged, it was confirmed that the distance from the water collection tube to the outer contour of the filament winding when the cut fan-shaped sample was returned to the cylindrical sample was within ±0.5% of the average value of the distances at four points shifted 60 degrees clockwise from the cut surface of the cut cylindrical sample. By dividing the obtained supply-side flow channel height H by the supply-side flow channel material thickness D, the ratio of the supply-side flow channel height H to the supply-side flow channel material thickness D, H / D, was obtained.

[0085] <Example 1> (Preparation of supply-side flow channel material) Using polypropylene as the material, molten resin was supplied from an extruder and extruded at a predetermined discharge pressure while rotating two inner and outer dies, each having numerous elongated holes, in opposite directions. A cylindrical net with a mesh structure was formed and rapidly cooled and solidified to produce a supply-side flow channel material with a thickness D of 0.70 mm, as shown in Tables 1 to 3. Note that the thickness D of the supply-side flow channel material, the intersection angle An, the distance between intersections TD, SD / D, and D １ / D ２ The aforementioned conditions were modified as appropriate to achieve the final shape of the supply-side flow channel material shown in Table 1.

[0086] (Fabrication of spiral-type separation membrane element) Nonwoven fabric made of polyethylene terephthalate fibers (fineness: 1 decitex, thickness: approximately 85 μm, air permeability: 1 cc / cm²) ２ / sec, density 0.80g / cm ３ A DMF solution containing 16.5% by mass of polysulfone was cast onto the material to a thickness of 170 μm at room temperature (25°C), and immediately immersed in pure water for 10 minutes. Subsequently, a porous support film with a thickness of 120 μm, consisting of a fiber-reinforced polysulfone support film, was fabricated by immersion in 80°C hot water for 1 minute.

[0087] Next, the surface of the polysulfone layer of the porous support membrane was immersed in an aqueous solution containing 3.5% by mass of m-phenylenediamine for 30 seconds, then slowly pulled up vertically, and excess aqueous solution was removed from the support membrane surface by blowing nitrogen through an air nozzle. Then, an n-decane solution containing 0.15% by mass of trimesinate chloride was applied to the surface of the membrane until it was completely wet, and then left to stand for 1 minute. After that, excess solution was removed from the membrane by air blowing, and the membrane was washed with 80°C hot water for 1 minute to obtain the separation membrane roll.

[0088] The effective area of ​​the separation membrane obtained in this way, when used as a separation membrane element, is 40.88 m². ２The material was folded and cut in such a manner, and then tricot (thickness: 0.26 mm) was sandwiched between the permeable side as the permeable channel material, and the layers were stacked in an envelope shape. Leaf adhesive was applied to form an envelope-shaped membrane. This envelope-shaped membrane was spirally wrapped around a Noril water collection pipe (width: 1016 mm, diameter: 38 mm, 40 holes in a straight row) facing the supply side channel material to form a winding body. After fixing the outer surface of this winding body with tape, the edges at both ends were cut and end plates were attached, creating an 8-inch diameter separation membrane element in which supply water is supplied from one end and permeable water and concentrated water are discharged from the other end.

[0089] (Operating pressure of the separation membrane element) A separation membrane module was constructed by connecting seven of the above-mentioned separation membrane elements in series and loading them into a cylindrical pressure vessel, and the operating pressure was measured. An aqueous NaCl solution with a temperature of 25°C, a concentration of 32,000 ppm, and a pH of 7.0 was used as the feedwater, and the water production volume was 108 m³. ３ The operating pressure was adjusted to achieve a daily rate of 108 m³, and the system was operated with a recovery rate of 45%. After 90 minutes of operation, the water production volume was 108 m³. ３ The pressure at / day was defined as the operating pressure (kPa).

[0090] (NaCl removal rate) The feedwater and permeate used in the measurement of the operating pressure described above were sampled, and the NaCl concentration was determined by conductivity measurement. The NaCl removal rate was calculated from the following formula: NaCl removal rate (%) = 100 × {1 - (NaCl concentration in permeate / NaCl concentration in feedwater)}.

[0091] (Element Differential Pressure) The upstream side (supply water side) and downstream side (concentrated water side) of the cylindrical pressure vessel containing the separation membrane element were connected by piping via a differential pressure gauge (model DG16) manufactured by Nagano Keiki, and the element differential pressure (kPa) during operation was measured.

[0092] (Neutral molecule removal rate) As the feedwater, an aqueous solution was used in which boric acid manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was dissolved in an aqueous NaCl solution at a temperature of 25°C, pH 7.0, and concentration of 2000 ppm to achieve a boron concentration of 0.5 ppm, and sodium metasilicate was further dissolved to achieve a silica concentration of 20 ppm. Next, a separation membrane module, which was constructed by loading one separation membrane element into a cylindrical pressure vessel, was operated for 90 minutes at an operating pressure of 1.55 MPa and a concentrated water flow rate of 300 L / min, after which sampling was performed for 1 minute. The silica concentration and boron concentration of the feedwater and permeate water were measured using an ICP emission spectrometer (Agilent 5110VDV), and the silica removal rate and boron removal rate were calculated from the following formulas. Silica removal rate (%) = 100 × {1 - (silica concentration in permeate / silica concentration in feedwater)} Boron removal rate (%) = 100 × {1 - (boron concentration in permeate / boron concentration in feedwater)}.

[0093] (Water Production Volume Reduction Rate) Using a separation membrane module constructed by loading one separation membrane element into a cylindrical pressure vessel, water collected from Lake Biwa that had passed through a 0.01 mm spool filter was used as the supply water. The system was operated for 90 minutes at an operating pressure of 1.0 MPa and a recovery rate of 50%, and a 1-minute sample was taken to measure the initial water production volume (GPD). Subsequently, the system was operated continuously for 24 hours, and a 1-minute sample was taken to measure the water production volume after water flow (GPD). The water production volume reduction rate (%) was calculated using the following formula: Water production volume reduction rate (%) = 100 × {1 - (Water production volume after water flow / Initial water production volume)}.

[0094] (ATP Adhesion Amount) The separation membrane element used in the measurement of the water production rate reduction described above was carefully disassembled without impact, and an arbitrary envelope-shaped membrane was taken out. The side corresponding to the supply water side was indexed as the 0% position, and the side corresponding to the concentrated water side as the 100% position. The separation membrane at the 20%, 50%, and 80% positions was cut out as 3 cm square samples. The cut-out samples were placed in a resealable plastic bag, and 10 ml of Otsuka distilled water (license number: 36A1X00001) manufactured by Otsuka Pharmaceutical Co., Ltd. was added to it. Then, the resealable plastic bag containing the samples was ultrasonically treated in an ultrasonic cleaner at 25°C for 20 min to obtain an extract containing biofilm. Next, 100 μL of Kikkoman's "Lucifer (registered trademark) 250 Plus" ATP extraction reagent was added to 100 μL of the extract and left for 20 seconds. Subsequently, 100 μL of Kikkoman's "Lucifer® 250 Plus" ATP luminescence reagent was added, and the fluorescence value (RLU) was immediately measured using a Kikkoman Lumitester (C-110). Two or more measurements were performed for each extract sample, and the average value was calculated. The amount of ATP adhering to the membrane surface (pg / cm²) was then calculated using the following formula. ２ The following was calculated: ATP concentration (mol / L) = 1.172 × 10 －１３ × Average value of fluorescence intensity (RLU).

[0095] (Fouling test using feedwater containing solids) A separation membrane module, consisting of one separation membrane element loaded into a cylindrical pressure vessel, was used. Industrial water with a turbidity of 100 degrees was used as the feedwater, and the module was operated for two weeks at an operating pressure of 1.0 MPa and a recovery rate of 50%. The differential pressure before and after operation was measured, and the difference was taken to calculate the differential pressure rise (kPa). In addition, the separation membrane element was removed from the pressure vessel after operation, and its end face was observed to check for protrusion of the feed-side flow channel material. If the feed-side flow channel material was protruding, the maximum protrusion distance (mm) from the end face was measured with a ruler.

[0096] The separation membrane element equipped with the fabricated supply-side flow channel material was evaluated using the method described above, and the results are shown in Table 1.

[0097] <Examples 2-26> Separation membrane elements were fabricated in the same manner as in Example 1, except that the shape of the supply-side flow channel material was as shown in Tables 1-3. Separation membrane modules, consisting of one or seven separation membrane elements loaded into a cylindrical pressure vessel, were used, and their performance was evaluated under the same conditions as in Example 1. The results are shown in Tables 1-3.

[0098] <Comparative Example 1> Separation membrane elements were fabricated in the same manner as in Example 1, except that the supply-side flow path material was as shown in Table 4. Separation membrane modules, consisting of one or seven separation membrane elements loaded into a cylindrical pressure vessel, were used, and their performance was evaluated under the same conditions as in Example 1. The results are shown in Table 4.

[0099] <Comparative Examples 2-6> Separation membrane elements were fabricated in the same manner as in Example 1, except that the supply-side flow channel material was as shown in Table 4. Separation membrane modules, consisting of one or seven separation membrane elements loaded into a cylindrical pressure vessel, were used, and their performance was evaluated under the same conditions as in Example 1. The results are shown in Table 4.

[0100]

[0101]

[0102]

[0103]

[0104] As is clear from the results shown in Tables 1 to 4, the separation membrane elements of Examples 1 to 26 can be said to have stable separation performance that sufficiently disturbs the feedwater, suppresses concentration polarization on the separation membrane surface, and exhibits excellent fouling resistance.

[0105] The separation membrane element of the present invention is particularly suitable for use in RO water purifiers and for desalination of brine and seawater. Although the present invention has been described in detail using specific embodiments, various modifications and variations are possible without departing from the intent and scope of the present invention.

[0106] 1. Spiral-type separation membrane element 2. 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. Supply water 8. Permeate water 9. Concentrated water D. Thickness of the supply-side channel material L. A series of lines connecting the diagonals of a quadrilateral formed by the four intersection points of fibrous rows X and Y P. １ , P ２ , P ３ , P ４ , P ５ Intersection TD, Distance between intersections SD, Side diameter An, Intersection angle TL, Circle with fiber diameter as its diameter CL, Straight line connecting the center of the water collection pipe to an arbitrary outer circumference F, Supply side flow path Z, Cross-section of the fibrous material Z １ Upper half cross-section Z ２ Lower half cross-section Z ３ Cross section Z ２ The convex hull figure L enclosing the Ｃ A straight line S divides the circumcircle of the cross-section Z into two vertical halves. １ The cross-sectional area S of the upper half when the cross-section Z is divided into two. ２ The cross-sectional area S of the lower half when the cross-section Z is divided into two. ３ Cross section Z ２ Cross section Z that encapsulates the convex shape. ３ Cross-sectional area D １ Maximum vertical diameter D of the cross-section Z ２ Maximum transverse diameter C of cross-section Z; Circumscribed circle C of cross-section Z. １ , C ２ Intersection TL １ , TL ２ Line segment P １ P ２ Tangent to a circle perpendicular to it

Claims

1. A supply-side channel material for a separation membrane element in the shape of a net, comprising a fibrous row X composed of a plurality of fibrous materials A arranged in one direction, and a fibrous row Y composed of a plurality of fibrous materials B arranged in a direction different from the fibrous row X, wherein the fibrous row X and the fibrous row Y intersect in three dimensions at their intersections, characterized in that the thickness D of the supply-side channel material is 0.50 mm or more and 1.00 mm or less, the intersection angle An at the intersections is 70 degrees or more and 110 degrees or less, the distance TD between adjacent intersections is 1.50 mm or more and 2.80 mm or less, and the ratio SD / D of the side diameter SD of the fibrous materials to the thickness D is 0.55 or more and 0.70 or less.

2. The supply-side flow channel material for a separation membrane element according to claim 1, characterized in that the ratio SD / D of the side diameter SD to the thickness D is 0.60 or more and 0.70 or less.

3. The supply-side flow channel material for a separation membrane element according to claim 1 or 2, characterized in that the distance TD between the intersections is 1.50 mm or more and 2.40 mm or less.

4. The supply-side flow channel material for a separation membrane element according to claim 1 or 2, characterized in that the crossing angle An is 80 degrees or more and 110 degrees or less.

5. At least one of the cross-sections Z in a direction perpendicular to the longitudinal direction of said fibrous material A or said fibrous material B is obtained by drawing a straight line parallel to the plane of a feed-side channel material that bisects a circumscribed circle in contact with said cross-section Z vertically into upper and lower halves, and the upper half cross-section Z of said cross-section Z １ has an area defined as S １ , the lower half cross-section Z ２ has an area defined as S ２ , where the ratio S １ / S ２ is 0.20 or more and 0.90 or less, said area S ２ to the area S of a convex hull figure Z ２ surrounding said cross-section Z ３ has a ratio S ３ / S ２ / S ３ is 0.75 or more and 1.00 or less, the ratio of the maximum vertical diameter D １ of said cross-section Z to the maximum horizontal diameter D ２ is D １ / D ２ is 1.05 or more and 2.00 or less, the feed-side channel material for a separation membrane element according to claim 1 or 2.

6. The ratio S ２ / S ３ The supply-side flow channel material for a separation membrane element according to claim 5, wherein the ratio is 0.90 or more and 1.00 or less.

7. The supply-side flow channel material for a separation membrane element according to claim 5, wherein the cross-sectional shape of the cross-section Z is teardrop-shaped.

8. The ratio S １ / S ２ The supply-side flow channel material for a separation membrane element according to claim 5, wherein the ratio is 0.30 or more and 0.60 or less.

9. In the fibrous material A and the fibrous material B, in 50% or more of the cross-sectional surface Z other than the intersection, ratio S １ / S ２ The ratio S is 0.20 or more and 0.90 or less. ２ / S ３ The ratio D is 0.75 or more and 1.00 or less. １ / D ２ The supply-side flow channel material for a separation membrane element according to claim 5, wherein the ratio is 1.05 or more and 2.00 or less.

10. A separation membrane element comprising at least a water collection pipe, a separation membrane, a supply-side flow channel material, and a permeate-side flow channel material, wherein the supply-side flow channel material is the supply-side flow channel material for a separation membrane element according to claim 1 or 2.

11. The separation membrane element according to claim 10, wherein the ratio H / D of the height H of the supply channel to the thickness D is 0.950 or more and 0.995 or less.

12. The separation membrane element according to claim 10, characterized in that it is used for treating feedwater with a salt concentration of 30,000 mg / L or more.

13. The separation membrane element according to claim 10, characterized in that it is used for the production of ultrapure water.

14. The separation membrane element according to claim 10, characterized in that the length of the element is 20 inches or more.

15. A separation membrane module comprising a plurality of separation membrane elements according to claim 10 inside a pressure vessel.

16. A fluid separation apparatus comprising the separation membrane element according to claim 10.

Images