Spiral separation membrane element

Abstract

To provide a spiral separation membrane element which can be suppressed from deteriorating in performance by preventing a membrane thereof from being scratched in a step of preparing the separation membrane element.SOLUTION: A spiral separation membrane element comprises at least a water collecting pipe, a separation membrane, a supply-side flow path material and a transmission-side flow path material. On a cross section that is perpendicular to a shaft direction of the water collecting pipe of the spiral separation membrane element, a height at an inner periphery side of a supply-side flow path F formed of the separation membrane positioned on a straight line connecting a center of the water collecting pipe to an arbitrary outer periphery and the supply-side flow path material is larger than a height at an outer periphery side thereof.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a separation membrane element for separating impurities from various liquids containing impurities, particularly for use in desalination of seawater, desalination of brackish water, production of ultrapure water, or treatment of wastewater. [Background technology]

[0002] In recent years, in the technology for removing ionic substances contained in seawater, brackish water, etc., separation methods using separation membrane elements have been increasingly used 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 their pore size and separation function. These membranes are used, for example, in the production of drinking water from seawater, brackish water, and water containing harmful substances, the production of industrial ultrapure water, wastewater treatment, and recovery of valuable materials, and are used according to the target components to be separated and their separation performance.

[0003] Separation membrane elements come in various shapes, but they have in common that raw water is supplied to one side of the separation membrane and permeated fluid is obtained from the other side. Separation membrane elements are formed with many bundled separation membranes to increase the membrane area per separation membrane element, that is, to increase the amount of permeated fluid obtained per separation membrane element. Various shapes of separation membrane elements have been proposed depending on the application and purpose, such as spiral type, hollow fiber type, plate-and-frame type, rotating flat membrane type, and flat membrane integrated type.

[0004] For example, a spiral separation membrane element is widely used for reverse osmosis filtration. The spiral separation membrane element includes a water collection pipe and a separation membrane unit wound around the water collection pipe. The separation membrane unit is formed by stacking a feed-side flow path material that supplies raw water (i.e., 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 permeation-side flow path material that guides the permeated fluid that has permeated the separation membrane and been separated from the feed-side fluid to the water collection pipe. The spiral separation membrane element is preferably used because it can apply pressure to the raw water and therefore can extract a large amount of permeated fluid.

[0005] Spiral separation membrane elements are generally produced by folding a cut separation membrane sheet, then cutting a net to use as a feed-side flow path material and sandwiching it between the feed-side surface of the folded separation membrane to produce a separation membrane leaf, and then applying adhesive to the permeate side of the resulting separation membrane leaf so that it becomes an envelope-like opening on the perforated collection pipe side. After that, the permeate-side flow path material is laminated to form a set of separation membrane units, and this is spirally wound around the perforated collection pipe. However, the separation membrane can be damaged during these element production stages, causing a decrease in the desalination performance of the separation membrane element.

[0006] Therefore, methods have been proposed for suppressing the deterioration of separation membrane performance during the production process of a separation membrane element. Specifically, Patent Document 1 proposes a method of using a composite semipermeable membrane having a protective layer containing anionic polyvinyl alcohol on the surface of the separation membrane. In addition, Patent Document 2 proposes a method for preventing damage to the surface of the separation membrane during the folding process of the separation membrane, in which an insertion member is used to push the folded portion of the membrane between a pair of clamping members whose distance from each other can be changed, and then the pushed-in portion is sandwiched between the clamping members to form a fold. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] WO17 / 057692 publication [Patent Document 2] JP 2005-270921 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the above-mentioned separation membrane element requires complicated manufacturing and post-treatment processes for the separation membrane and the separation membrane element, and is not sufficient for industrial stable production. For example, in the method described in Patent Document 1, when using a spiral separation membrane element produced using a composite semipermeable membrane with a protective layer, a process is required to pass washing water through the element to remove the protective layer on the skin layer, which requires the treatment of a large amount of waste liquid. In addition, the method described in Patent Document 2 is effective in preventing damage to the folds, but is not sufficient in preventing damage to other parts where the separation membrane and the flow path material contact each other. Therefore, the object of the present invention is to provide a spiral separation membrane element that can suppress the deterioration of membrane performance at the separation membrane element production stage by controlling the structure of the separation membrane element. [Means for solving the problem]

[0009] The present invention and its preferred embodiments comprise the following: (1) A spiral separation membrane element including at least a water collection pipe, a separation membrane, a feed-side flow passage material, and a permeate-side flow passage material, wherein, in a cross section perpendicular to the axial direction of the water collection pipe of the spiral separation membrane element, a feed-side flow passage F formed by the separation membrane and the feed-side flow passage material located on a straight line connecting the center of the water collection pipe and an arbitrary outer periphery is determined by determining a height D of the feed-side flow passage on the inner periphery side. I is the outer flow channel height D O The spiral separation membrane element is characterized by being larger. (2) Regarding the supply side flow passage F, the supply side flow passage height D on the outer periphery O Height D of the inner supply flow passage I The spiral separation membrane element according to the above (1), wherein the ratio is 1.050 or more and 1.150 or less. (3) A fluid separation device using the spiral separation membrane element described in (1) or (2) above. Effect of the Invention

[0010] According to the present invention, a spiral separation membrane element that suppresses deterioration of the membrane performance of the spiral separation membrane element and has excellent separation performance such as water permeability and salt rejection rate can be obtained. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a partially developed perspective view showing an example of a separation membrane element. [Diagram 2] FIG. 2 is a plan view showing an example of the flow channel material on the supply side. [Diagram 3] FIG. 3 is a diagram showing an example of a flow channel height pattern on the supply side of a separation membrane element of the present invention. [Figure 4] FIG. 4 is a diagram showing an example of a feed-side flow channel height pattern of a separation membrane element other than that of the present invention. [Diagram 5] FIG. 5 is a diagram for explaining a graph of the supply side flow path height. [Figure 6] FIG. 6 is a diagram showing a method for measuring the flow channel height of a separation membrane element. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described in detail.

[0013] In this specification, "mass" is synonymous with "weight." In addition, in this specification, "to" means that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0014] <Separation membrane element> A spiral separation membrane element according to an embodiment of the present invention includes at least a water collection pipe, a separation membrane, a feed-side flow path material, and a permeate-side flow path material.

[0015] In the spiral separation membrane element 1 shown in FIG. 1, a polymer net is used as the feed-side flow passage material 2 that forms the flow passage on the feed side. In addition, a tricot with a finer spacing than the feed-side flow passage material 2 is used as the permeation-side flow passage material 4 in order to prevent the separation membrane 3 from falling and to form the flow passage on the permeation side. An envelope-shaped membrane 5 is formed by the permeation-side flow passage material 4 and the separation membrane 3 that is overlapped and adhered to both sides of the permeation-side flow passage material 4 in an envelope-like shape. The inside of the envelope-shaped membrane 5 constitutes the permeation-side flow passage. The envelope-shaped membrane 5 that is alternately laminated with the feed-side flow passage material 2 is spirally wound with a predetermined portion on the opening side adhered to the outer circumferential surface of the water collection tube 6. The direction of the x-axis shown in FIG. 1 is the longitudinal direction of the water collection tube 6. The planar direction including the y-axis and z-axis is perpendicular to the longitudinal direction of the water collection tube 6.

[0016] In the spiral separation membrane element 1, feed water 7 is usually supplied from one side in the longitudinal direction, and as the feed water 7 flows parallel to the water collection pipe 6, it is gradually separated into permeated water 8 and concentrated water 9. The permeated water 8 exits the spiral separation membrane element 1 from the side opposite to the side to which the feed water 7 is supplied.

[0017] In this system, the feed water 7 flows from one side of the spiral separation membrane element 1 to the other, so that there is necessarily a sufficient distance where the water is in contact with the membrane, and this is characterized by the fact that the feed water 7 is sufficiently separated into permeate 8 and concentrate 9.

[0018] <Manufacturing of spiral separation membrane elements> (Formation of separation membrane leaf) The separation membrane leaf may be formed by sandwiching a feed-side flow path material between separation membranes and folding the separation membranes so that the feed-side surface faces inward, or by stacking two separate separation membranes with their feed-side surfaces facing each other and sealing the periphery of the separation membranes.

[0019] Examples of the "sealing" method include adhesion using an adhesive or hot melt, fusion using heat or a laser, and sandwiching a rubber sheet. Sealing by adhesion is particularly preferred because it is the simplest and most effective.

[0020] (Manufacturing of spiral separation membrane elements) A spiral separation membrane element can be made into a spiral type by alternately stacking separation membrane leaves and permeate side flow path materials while applying adhesive on a permeate side flow path material that serves as a base attached to a central pipe, and then winding it up. At this time, the feed side flow path height can be adjusted by controlling the winding tension, thickness, material, shape, etc. of the members.

[0021] <Structure of the spiral separation membrane element> In a spiral separation membrane element, when a uniform thickness of a feed-side flow passage material, a uniform thickness of a permeation-side flow passage material, and a uniform thickness of a membrane are wound with a constant tension, a flow passage of a basically uniform height can be formed. However, the curvature of the separation membrane in a spiral separation membrane element differs between the outer periphery and the inner periphery as shown in FIG. 5, and the curvature is larger on the inner periphery closer to the water collection pipe. The inner periphery region with a larger curvature is in a state where a stronger compressive or tensile stress is applied to the separation membrane than the outer periphery region with a smaller curvature, and in this state, the feed-side flow passage material net is pressed against the membrane surface and the shape is fixed as a separation membrane element, so the separation membrane surface on the inner periphery side tends to be more easily damaged than the separation membrane surface on the outer periphery side. In other words, an element with a flow passage distribution with a wider flow passage on the inner periphery side than a uniform flow passage can suppress damage to the separation membrane due to contact between the membrane and the flow passage material, and can maintain the membrane performance of the separation membrane before processing into an element.

[0022] In a spiral separation membrane element, the curvature of the separation membrane on the inner circumference side increases as the outer diameter of the water collection pipe becomes smaller. Therefore, the effectiveness of the present invention increases as the outer diameter of the water collection pipe becomes smaller. In particular, in a configuration in which the outer diameter of the water collection pipe is 40 mm or less, in which the curvature of the separation membrane on the inner circumference side becomes larger, the effect of suppressing the deterioration of the membrane performance of the separation membrane element is high, and the effectiveness is higher.

[0023] Therefore, in this embodiment, in a cross section perpendicular to the water collection pipe of the separation membrane element, the supply side flow passage F formed by the separation membrane and the supply side flow passage material located on a straight line connecting the center of the water collection pipe and an arbitrary outer periphery is defined as the supply side flow passage height D I is the height of the supply side flow passage on the outer periphery D O As a method for achieving such a channel height distribution, it is possible to first weaken the winding tension and then reduce the winding tension, to form a channel of uniform thickness once and then loosen the winding on the inner circumference side, to widen the channel on the inner circumference by reducing the amount of adhesive applied on the inner circumference, to widen the pitch of the feed-side channel material on the inner circumference side of the spiral separation membrane element, to change the material of the feed-side channel material, to coat a part of the feed-side channel material corresponding to the inner circumference with a water-soluble material and then dissolve it to widen the inner circumference, or to design the thickness of the feed-side channel material to be thicker on the inner circumference side of the spiral separation membrane element.

[0024] Supply side channel height D in supply side channel F F can be measured non-destructively by using an X-ray CT scanner. For the feed-side flow path F formed by the separation membrane and feed-side flow path material located on the line L connecting the center of the collection pipe of the spiral separation membrane element to an arbitrary circumference, it is necessary to analyze a location that is some distance away from the cut surface and is not affected by the cut, so the analysis is performed from a position 2 inches to a position 4 inches from the cut surface in a direction parallel to the longitudinal direction of the collection pipe. For an 8-inch element, the analysis range is a rectangular parallelepiped with a length of 4 inches, a width of 1 inch, and a depth of 2 inches, with the line L as the center and the center point of the collection pipe as the contact point, on a plane on the line L, and the spatial volume of each flow path is measured. If the diameter is smaller than 8 inches, the depth is fixed at 2 inches, and the length and width are multiplied by a ratio according to the diameter to reduce it. For example, for a 4-inch element, multiply by 4 / 8 to get a length of 2 inches and a width of 0.5 inches.

[0025] Supply side flow passage height D FWhen measuring the volume of the flow passage, if one end of the flow passage touches the central pipe or the outer filament winding in the area cut by the rectangular parallelepiped, the flow passage volume will be underestimated. Therefore, only the flow passages whose both ends are cut by the long sides of the rectangular parallelepiped are considered valid.

[0026] Supply side flow passage height D on the outer periphery O For example, if there are 60 channels, the average value of the 12 channels from the periphery is used as D O The height of the inner supply flow passage D I D is the average value for 20% of the flow path from the collection pipe. O and D. I When calculating, if a decimal point occurs, the value is rounded off to an integer. O , Average value of 20% to 40% of the channel height from the outer circumference, Average value of 40% to 60% of the channel height, Average value of 60% to 80% of the channel height, D I It is preferable that the values ​​increase gradually in the order of (including the same value).

[0027] If the spiral separation membrane element is wet when the X-ray CT is measured, it is necessary to remove the water beforehand using a vacuum dryer or the like. To dry, perform vacuum drying at 40°C until there is no weight change. "No weight change" means that the spiral separation membrane element is left standing in an upright position for 24 hours or more to drain the internal water, and then vacuum dried for 24 hours or more. After that, the element is taken out of the vacuum dryer every 30 minutes and the weight is measured. The difference between the final measurement point and the immediately preceding measurement point should be 0.1% or less of the weight of the final measurement point. For example, if the final measurement point is 10.14 kg and the immediately preceding measurement is 10.15 kg, the difference is 0.01 kg, and since the final measurement point is 10.14 kg, the result is 0.01 / 10.14=0.098%, and it can be determined that the element is dry.

[0028] (Supply side flow path height pattern) As shown in Figs. 3(a) to (e), the height of the supply side flow passage in this embodiment is a flow passage height D I The height of the supply flow passage on the outer periphery DO The graph in Figure 3 can be interpreted as shown in Figure 5, where the horizontal axis represents the position of the flow channel and the vertical axis represents the flow channel height, and the distribution is shown when the flow channel height on the outer periphery side of the separation membrane element is plotted on the left side of the graph and the flow channel height on the inner periphery side is plotted on the right side of the graph.

[0029] As an example of a conventional supply side flow channel height pattern other than that of the present invention, a uniform flow channel as shown in FIG. 4 can be given.

[0030] (D O D I (ratio of Outer flow path height D O Height D of the inner supply flow passage I Ratio of D I / D O is preferably 1.050 or more and 1.150 or less. D I / D O When the thickness falls within this range, damage to the separation membrane on the inner periphery side can be suppressed, and the membrane performance of the separation membrane before being processed into an element can be maintained.

[0031] <Supply side flow path> (Supply side channel material) As shown in FIG. 2, the feed-side flow path material used in a spiral separation membrane element generally consists of a plurality of fibrous rows X made of fibrous materials A (21) arranged in one direction, and a plurality of fibrous rows Y made of fibrous materials B (22) arranged in a direction different from that of the fibrous rows X, and the fibrous rows X and the fibrous rows Y intersect with each other three-dimensionally to form intersections at a plurality of points, forming a net shape.

[0032] In a spiral separation membrane element, the driving force for permeation is the transmembrane pressure difference, so increasing the transmembrane pressure is effective in improving the amount of water produced. The transmembrane pressure difference is expressed as the pressure applied to the separation membrane element minus the flow resistance and osmotic pressure. Therefore, to increase the transmembrane pressure difference, it is necessary to increase the applied pressure, reduce the flow resistance, or reduce the membrane surface osmotic pressure. The membrane surface osmotic pressure increases due to the occurrence of membrane surface concentration polarization. The fibrous material of the feed-side flow path material has the role of disturbing the feed water, and in order to suppress membrane surface concentration polarization, it is important to create a vortex (flow) of the feed water on the membrane surface behind the fibrous material.

[0033] The shape of the feed-side flow passage material used in the spiral separation membrane element is not limited to this shape, and various shapes such as a grid shape or a corrugated sheet can be used as long as the space between the membranes can be secured.

[0034] (Thickness of the supply side channel material) The average thickness of the feed-side channel material is preferably in the range of 0.50 mm to 2.0 mm. If the average thickness of the feed-side channel material is in this range, the pressure loss is not too large, and a sufficient feed-side channel that is not easily clogged with substances such as foulants that may accumulate on the membrane surface or the feed-side channel material can be secured, and blockage of the feed-side channel by impurities in the feed water or foulants such as microorganisms can be suppressed, and the separation membrane element can be operated stably for a long period of time without increasing the required power of the pump. If the feed-side channel material is thinner than this range, it may cause a large pressure loss or cause fouling to progress easily. If the feed-side channel material is thicker than this range, it is not preferable from the viewpoint of handleability, but it is possible to adjust the rigidity to an appropriate level by selecting an appropriate intersection pitch and material.

[0035] The thickness of the intersections and the feed-side flow channel material can be measured using a commercially available microscope or X-ray CT measuring device by observing a longitudinal section parallel to the fiber rows and measuring the distance. The diameters of any 30 points on the intersections or the thickness of the feed-side flow channel material can be extracted and measured using the measurement mode, and the average value can be calculated.

[0036] (material) The material of the feed-side channel material is not particularly limited, but from the viewpoint of moldability, a thermoplastic resin is preferable, and in particular, polyethylene and polypropylene are preferable because they are unlikely to damage the surface of the separation membrane and are inexpensive. In addition, the feed-side channel material may be formed of the same material for the fibrous material A and the fibrous material B, or may be formed of different materials.

[0037] <Permeate side flow path> (Permeate side channel material) In the envelope-shaped membrane 5, the separation membranes 3 are stacked with their permeate side surfaces facing each other, and a permeate-side channel material 4 is disposed between the separation membranes 3, forming a permeate-side channel. The material of the permeate-side channel material is not limited, and tricot, nonwoven fabric, a porous sheet with protrusions attached, a film with a concave-convex shape and perforations, and a concave-convex nonwoven fabric can be used. In addition, protrusions that function as the permeate-side channel material may be attached to the permeate side of the separation membrane.

[0038] <Use of separation membrane elements> The separation membrane elements may be connected in series or in parallel and housed in a pressure vessel to be used as a separation membrane module.

[0039] Furthermore, the above-mentioned separation membrane element and separation membrane module can be combined with a pump for supplying a fluid thereto, a device for pretreating the fluid, etc. to form a fluid separation device. By using this separation device, for example, it is possible to separate feed water into permeated water such as drinking water and concentrated water that did not permeate the membrane, thereby obtaining water suitable for the purpose.

[0040] The higher the operating pressure of the fluid separation device, the higher the removal rate, but the more energy required for operation will be. Also, taking into consideration the retention of the supply flow path and permeation flow path of the separation membrane element, the operating pressure when permeating the supply water to the separation membrane module is preferably 0.2 MPa or more and 6 MPa or less.

[0041] As the temperature of the feed water increases, the salt rejection rate decreases, but as the temperature decreases, the membrane permeation flux also decreases. Therefore, the temperature of the feed water is preferably 5°C or higher and 45°C or lower.

[0042] In addition, when the pH of the raw water is in the neutral range, even if the raw water is a liquid with a high salt concentration such as seawater, the formation of scale such as magnesium is suppressed, and deterioration of the membrane is also suppressed.

[0043] (supply water) The water supplied to the separation membrane element of this embodiment is not particularly limited, and may be tap water that has been treated in advance, or may be water with a large amount of impurities in the solution, such as seawater, brine, or sewage. 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. In general, TDS refers to the total dissolved solids content, and is expressed as "mass / volume", but it 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 a solution filtered through a 0.45 μm filter at a temperature of 39.5 to 40.5° C., but it is more convenient to convert it from the practical salinity (S). EXAMPLES

[0044] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0045] (Measurement of thickness of flow passage material on the supply side) The feed-side channel material was cut into a piece of 10 x 10 cm, and a longitudinal section parallel to the fibrous rows of the feed-side channel material was observed at a magnification of 20x using a Keyence One-Shot 3D Shape Measuring Instrument VR-3000. The thickness of 30 arbitrary intersections was measured and the average value was calculated.

[0046] (Supply side flow path height) The separation membrane element was cut in a direction perpendicular to the longitudinal direction of the water collection pipe, from the position 6 inches to the position 12 inches from the end, and a cylindrical sample 6 inches long was cut out. In order to prevent the flow path structure from collapsing, adhesive was applied to the entire surface from both sides of the cut surface of the element, and the adhesive was slightly impregnated from the end of the element. The cylindrical sample was cut into a column with a fan-shaped bottom with a central angle of 60 degrees to obtain an observation sample. The fan-shaped sample was then dried in a vacuum oven set at 40°C until there was no change in weight. A GE X-ray CT measuring device Phoenix v |tome| x m300 was used to scan the sample under conditions of a tube current of 100 μA, a tube voltage of 150 kV, and a resolution of 19.8 μm, and a 3D image was obtained. Analysis was then performed using VOLUMEGRAPHICS' VGSTUDIO MAX, and the supply side flow path height was measured.

[0047] The height of the supply-side channel can be measured from the volume of the supply-side channel. As shown in Figure 6, in a cross section perpendicular to the axial direction of the collection pipe of the separation membrane element, the center of the collection pipe is the contact point, and the supply-side channel F formed by the separation membrane and the supply-side channel material located on the line L connecting the center of the collection pipe to an arbitrary periphery is divided into a rectangular area of ​​4 inches long x 1 inch wide x 2 inches deep, and the spatial volume of each channel is measured to obtain the volume of the supply-side channel corresponding to each channel. If one end of the channel is in contact with the collection pipe or the filament winding on the periphery, the volume will be smaller than the other channels, so it is not possible to compare the channel heights fairly. Therefore, only the channels that have both ends touching a vertical line in a rectangular area of ​​4 inches long x 1 inch wide were analyzed. Since the obtained channel volume includes the supply-side channel material, the channel volume ignoring the supply-side channel material can be obtained by dividing it by the porosity of the supply-side channel material. The length of the arc was measured using ImageJ. The line was traced with the line selection tool according to the scale on the screen, and the relationship between the actual size and pixels was set with Set Scale. The arc length was obtained by tracing along the arc with the broken line selection tool and selecting Measure. Since arcs exist above and below the flow channel, the arcs above and below were measured and their average value was used as the arc length. The depth of the flow channel is a known value within the analysis range, and the height D of the flow channel on the supply side was calculated using the arc length and the porosity of the flow channel material on the supply side according to formula (1). F obtained.

[0048]

number

[0049] (Measurement of porosity of feed side channel material) The feed channel material was cut to a size of 50 cm x 50 cm, weighed, and calculated as the weight per unit area (kg / m 2 The obtained value was divided by the thickness of the flow passage material on the supply side to obtain the weight per unit volume (kg / m 3 ) was calculated from the formula (2). 3 ) was used to calculate the porosity of the feed channel material.

[0050]

number

[0051] (Fabrication of spiral separation membrane element) Nonwoven fabric made of polyethylene terephthalate fibers (fineness: 1 decitex, thickness: approx. 90 μm, air permeability: 1 cc / cm 2 / sec, density 0.80g / cm 3 A 18.5 mass % solution of polysulfone in DMF was cast onto the support membrane at room temperature (25°C) to a thickness of 150 μm, and the resultant roll was immediately immersed in pure water and left for 5 minutes, and then immersed in warm water at 80°C for 1 minute to produce a roll of a porous support layer (thickness 115 μm) made of a fiber-reinforced polysulfone support membrane.

[0052] The surface of the polysulfone layer of the porous support membrane was then immersed in an aqueous solution containing 3.0% by mass of m-PDA and 1.0% by weight of ε-caprolactam for 2 minutes, and then slowly pulled up vertically. Excess aqueous solution was removed from the surface of the support membrane by blowing nitrogen from an air nozzle.

[0053] Then, a n-decane solution containing 0.15% by mass of trimesoyl chloride was applied so that the surface of the membrane was completely wetted, and the membrane was left to stand for 1 minute. After that, excess solution was removed from the membrane by air blowing, and the membrane was washed with hot water at 80°C for 1 minute to obtain a composite separation membrane roll.

[0054] The separation membrane thus obtained was used in a separation membrane element with an effective area of ​​47.0 m 2 A polypropylene net (thickness: 0.76 mm) was then sandwiched between the membrane as a feed water side flow path material to prepare a separation membrane leaf.

[0055] Tricot (thickness: 0.26 mm) was laminated on the permeate side of the obtained separation membrane leaf as the permeate side flow path material, a leaf adhesive was applied, and the laminate was spirally wound around an ABS (acrylonitrile butadiene styrene copolymer synthetic resin) water collection pipe (width: 1,016 mm, diameter: 38 mm, number of holes: 40 in one straight row) with the wrapping tension increased in stages each time the laminate was wrapped by 20%. After the outer periphery of the wrapped body was fixed with tape, the edges at both ends were cut and end plates were attached, to produce a spiral separation membrane element in which feed water is supplied from one side and concentrated water is discharged.

[0056] (Water production capacity of spiral separation membrane element) The spiral separation membrane element was placed in a pressure vessel, and the feed water was an aqueous NaCl solution with a temperature of 25°C, a concentration of 32,000 ppm, and a pH of 7.0. The operating pressure was 5.52 MPa, and the recovery rate was 8%. After 3 hours of operation, a 1-minute sample was taken, and the amount of water produced per day (m 3 The data are expressed as 100 mg / day.

[0057] (Spiral separation membrane element removal rate (TDS removal rate)) The TDS concentration of the feed water used during the 1-minute operation to measure the amount of water produced and the sampled permeate was determined by conductivity measurement, and the TDS removal rate was calculated using the following formula.

[0058] TDS removal rate (%) = 100 x {1 - (TDS concentration in permeate water / TDS concentration in feed water)} (Water production volume after dismantling the spiral membrane element) After measuring the water production volume and removal rate of the spiral separation membrane element, the tape securing the end plates of the spiral separation membrane element and the outer peripheral surface of the wound body was removed, and the wound body was then rewound. Thirty samples of the effective portion of the composite separation membrane other than the adhesive sealed portion were taken from any location within 20% of the outer periphery of the laminate and 20% of the water collection pipe. The composite separation membrane was fed with a NaCl aqueous solution having a temperature of 25°C, a concentration of 32,000 ppm, and a pH of 7.0 at an operating pressure of 5.52 MPa. The membrane permeation flux (m 3 / m 2 / day) was obtained, and the average value of 30 locations was calculated as the amount of water produced by the disassembled spiral separation membrane element.

[0059] (Removal rate of the spiral separation membrane element disassembled membrane (TDS removal rate)) The TDS concentration of the feed water and the sampled permeate water used to measure the amount of water produced by the disassembled spiral separation membrane element was determined by conductivity measurement, and the TDS removal rate was calculated using the following formula. The average value of 30 locations was used as the removal rate of the disassembled spiral separation membrane element.

[0060] TDS removal rate (%) = 100 x {1 - (TDS concentration in permeate water / TDS concentration in feed water)} Example 1 The produced spiral separation membrane element was placed in a pressure vessel and evaluated under the conditions described above. The results are shown in Table 1.

[0061] (Examples 2 to 3) A spiral separation membrane element was produced in the same manner as in Example 1, except that the thickness of the feed-side flow passage material was changed to set the feed-side flow passage height as shown in Table 1.

[0062] The spiral separation membrane element was placed in a pressure vessel and the performance was evaluated under the same conditions as in Example 1. The results are shown in Table 1.

[0063] (Examples 4 to 11) A spiral separation membrane element was produced in the same manner as in Example 1, except that the wrapping tension conditions of the laminate were changed and the feed side flow channel height was set as shown in Table 1.

[0064] The spiral separation membrane element was placed in a pressure vessel and the performance was evaluated under the same conditions as in Example 1. The results are shown in Table 1.

[0065] The spiral separation membrane element was placed in a pressure vessel and the performance was evaluated under the same conditions as in Example 1. The results are shown in Table 1.

[0066] <Comparative Example> (Comparative Examples 1 to 4) A spiral separation membrane element was produced in the same manner as in Example 1, except that the wrapping tension conditions of the laminate were changed and the feed side flow channel height was set as shown in Table 2.

[0067] The spiral separation membrane element was placed in a pressure vessel and its performance was evaluated under the conditions described above. The results are shown in Table 2.

[0068] [Table 1]

[0069] [Table 2]

[0070] As is clear from the results shown in Tables 1 and 2, the spiral separation membrane elements of Examples 1 to 11 can be said to have excellent and stable desalination performance. Furthermore, in the spiral separation membrane elements of Examples 1 to 11, even in the membrane disassembled 20% from the inner circumference side (water collection pipe side), there was a tendency for the membrane to maintain excellent performance similar to that of the membrane disassembled 20% from the outer circumference side. [Industrial Applicability]

[0071] The separation membrane element of the present invention can be suitably used, in particular, for desalination of seawater, desalination of brackish water, production of ultrapure water, or wastewater treatment.

[0072] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. [Explanation of symbols]

[0073] 1 Spiral 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 membrane 6 Water collection pipe 7 Supply water 8 Permeate water 9 Concentrated water c Intersection distance of the supply side channel material in the direction perpendicular to the supply water flow direction d Intersection distance parallel to the feed water flow direction of the feed side channel material L is a straight line connecting the center of the water collection tube of the spiral separation membrane element and any periphery. F Supply side flow path D F Average height of supply side channel D O Average height of the supply side flow passage from the outer periphery to 20% D I Average height of the supply side flow passage at 20% from the inner circumference

Claims

1. A spiral separation membrane element including at least a water collection pipe, a separation membrane, a supply-side flow passage material, and a permeation-side flow passage material, wherein, in a cross section perpendicular to the axial direction of the water collection pipe of the spiral separation membrane element, a supply-side flow passage F formed by the separation membrane and the supply-side flow passage material located on a straight line connecting the center of the water collection pipe and an arbitrary outer periphery is provided with a supply-side flow passage height D on the inner periphery side. Ｉ is the outer periphery flow channel height D Ｏ The spiral separation membrane element is characterized by being larger.

2. Regarding the supply side flow passage F, the supply side flow passage height D on the outer periphery Ｏ The height D of the inner supply side flow passage relative to the Ｉ 2. The spiral separation membrane element according to claim 1, wherein the ratio of is 1.050 or more and 1.150 or less.

3. A fluid separation device using the spiral separation membrane element according to claim 1 or 2.

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