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WO2024190625A1 - Élément de membrane de séparation en spirale - Google Patents

Élément de membrane de séparation en spirale Download PDF

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Publication number
WO2024190625A1
WO2024190625A1 PCT/JP2024/008885 JP2024008885W WO2024190625A1 WO 2024190625 A1 WO2024190625 A1 WO 2024190625A1 JP 2024008885 W JP2024008885 W JP 2024008885W WO 2024190625 A1 WO2024190625 A1 WO 2024190625A1
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Prior art keywords
separation membrane
flow path
side flow
supply
feed
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PCT/JP2024/008885
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English (en)
Japanese (ja)
Inventor
秀 谷口
健太朗 高木
剛士 誉田
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Toray Industries Inc
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Toray Industries Inc
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Priority to JP2024516514A priority Critical patent/JPWO2024190625A1/ja
Publication of WO2024190625A1 publication Critical patent/WO2024190625A1/fr
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
    • B01D63/10—Spiral-wound membrane modules

Definitions

  • the present invention relates to a separation membrane element for separating impurities from various liquids containing impurities, particularly for use in desalinating seawater, desalinating brackish water, producing ultrapure water, or treating wastewater.
  • separation membrane elements As a technology for removing ionic substances contained in seawater and brine has been expanding as a process for saving energy and resources.
  • the separation membranes used in separation membrane elements are classified into microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, reverse osmosis membranes, and forward osmosis membranes based on their pore size and separation function. These membranes are used, for example, to produce drinking water from seawater, brine, and water containing harmful substances, to produce ultrapure water for industrial use, as well as for wastewater treatment and recovery of valuable materials, and are used differently depending on the target components to be separated and their separation performance.
  • Separation membrane elements come in a variety of shapes, but they all 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 made up of many bundled separation membranes, which increases the membrane area per separation membrane element, meaning that a large amount of permeated fluid is obtained per separation membrane element.
  • Various shapes of separation membrane elements have been proposed depending on the application and purpose, including spiral types, hollow fiber types, plate-and-frame types, rotating flat membrane types, and flat membrane integrated types.
  • spiral separation membrane elements are widely used for reverse osmosis filtration.
  • a spiral separation membrane element comprises a water collection pipe and a separation membrane unit wrapped around the water collection pipe.
  • the separation membrane unit is formed by stacking a supply-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 supply-side fluid to the water collection pipe.
  • Spiral separation membrane elements are preferably used because they can apply pressure to the raw water, allowing a large amount of permeated fluid to be extracted.
  • concentration polarization may occur, in which dissolved substances such as salts in the feed water form a concentration gradient along a direction perpendicular to the separation membrane.
  • concentration polarization occurs, the membrane surface osmotic pressure increases, reducing the performance of the 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 osmotic pressure and flow resistance. Therefore, to increase the transmembrane pressure difference, it is necessary to increase the applied pressure, reduce the membrane surface osmotic pressure, or reduce the flow resistance.
  • the applied pressure is the same, it is sufficient to reduce the membrane surface osmotic pressure or flow resistance to improve the amount of water produced.
  • Patent Document 1 proposes a net in which concentration polarization is reduced by having a repeating structure of spiral fibrous materials in the supply-side flow path material.
  • the objective of the present invention is to provide a separation membrane element that can reduce membrane surface concentration polarization while reducing flow resistance by controlling the structure of the separation membrane element.
  • a spiral separation membrane element comprising at least a water collection pipe, a separation membrane, a supply-side flow path material, and a permeate-side flow path material, wherein in a cross section perpendicular to the axial direction of the water collection pipe of the separation membrane element, for a supply-side flow path F formed by the separation membrane and the supply-side flow path material located on a straight line connecting the center of the water collection pipe and an arbitrary outer periphery, a supply-side flow path height D O on the outer periphery side and a supply-side flow path height D I on the inner periphery side are smaller than a flow path height D C in a central portion between the outer periphery side and the inner periphery side.
  • the flow path when the feed water flows into the element, the flow path is wide where the flow velocity is high and narrow where the flow velocity is low, which allows for a good balance of flow and suppresses concentration polarization.
  • the height of the feed side flow path is small compared to the thickness of the feed side flow path material, ensuring the turbulence effect of the feed side flow path material, and a separation membrane element with excellent separation performance such as water permeability and salt rejection rate can be obtained.
  • FIG. 1 is a partially developed perspective view showing an example of a separation membrane element.
  • FIG. 2 is a plan view showing an example of the feed side channel material of the present invention.
  • FIG. 3 is a diagram showing the flow velocity distribution in a typical circular pipe or between flat plates.
  • FIG. 4 is a perspective view showing an example of a flow rate distribution supplied to a separation membrane element.
  • FIG. 5 is a diagram showing an example of a flow channel height pattern on the supply side of the separation membrane element of the present invention.
  • FIG. 6 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.
  • FIG. 7 is a diagram for explaining a graph of the supply side flow path height.
  • FIG. 8 is a diagram showing a method for measuring the flow channel height of a separation membrane element.
  • a spiral separation membrane element includes at least a water collection pipe, a separation membrane, a feed-side flow path material, and a permeate-side flow path material.
  • a polymer net is used as the supply-side flow passage material 2 that forms the flow passage on the supply side.
  • a tricot with finer spacing than the supply-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 x-axis direction 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.
  • the 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 permeate water 8 and concentrated water 9.
  • the permeate water 8 exits the spiral separation membrane element 1 from the side opposite to the side to which the feed water 7 is supplied.
  • the feed water 7 flows from one side of the spiral separation membrane element 1 to the other, so there is inevitably a sufficient distance where it is in contact with the membrane, which is why the feed water 7 is sufficiently separated into permeate water 8 and concentrate water 9.
  • a separation membrane leaf is a separation membrane formed with its permeation side surfaces facing each other, and may be formed by sandwiching a feed-side flow path material between separation membranes and folding the separation membranes so that their feed-side surfaces face inward, or by overlapping two separate separation membranes with their feed-side surfaces facing each other and sealing the periphery of the separation membranes.
  • Methods for "sealing” include adhesion using adhesives or hot melts, fusion using heat or lasers, and sandwiching a rubber sheet. Sealing using adhesives is particularly preferred as it is the simplest and most effective method.
  • a spiral separation membrane element can be made into a spiral type by layering separation membrane leaves and permeate side flow path materials alternately 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 height of the feed side flow path can be adjusted by controlling the winding tension, thickness of the members, material, etc.
  • a spiral separation membrane element can basically form a flow path of uniform height when it is wrapped with a constant tension using a feed-side flow path material of uniform thickness, a permeation-side flow path material of uniform thickness, and a membrane of uniform thickness.
  • the flow velocity distribution in a circular pipe or between two flat plates is a cone-shaped velocity distribution in which the flow is slowest at the wall and fastest at the center of the circular pipe, as shown in Figure 3, although the shape differs depending on whether the flow is turbulent or laminar.
  • the inlet is divided by a water collection pipe and can be considered as a double circular pipe, and the flow velocity is slow on the outer and inner sides and fast in between, as shown in Figure 4.
  • the spiral separation membrane element of this embodiment has end plates with various shapes, including spoke shapes, and the flow may be divided by the end plates, but even in such cases the same concept can be applied to each divided inlet.
  • the supply-side flow path height D O on the outer periphery side and the supply-side flow path height D I on the inner periphery side are smaller than the flow path height DC at the center between the outer periphery side and the inner periphery side.
  • Possible methods for achieving such a channel height distribution include first increasing the winding tension, then decreasing the winding tension, and finally increasing the winding tension again; first forming channels of uniform height and then tightly winding the water collection pipe 6 and the outer periphery to narrow the channel on the outer and inner periphery; widening the channel in the center by reducing the amount of adhesive applied in the center; reducing the thickness of the feed-side channel material 2 on the outer periphery and inner periphery of the spiral separation membrane element 1, widening the pitch of the feed-side channel material 2, changing the material of the feed-side channel material 2, coating a part of the feed-side channel material 2 corresponding to the center with a water-soluble material and dissolving it later to widen the center; designing the thickness of the permeate-side channel material 4 to be thicker on the outer periphery and inner periphery of the spiral separation membrane element 1; and weakening the physical strength of the separation membrane on the outer periphery and inner periphery of the spiral separation membrane element 1
  • the feed-side flow path height D F in the feed-side flow path F can be measured by using an X-ray CT device.
  • the feed-side flow path F formed by the separation membrane 3 and the feed-side flow path material 2 located on the straight line L connecting the center of the water collection tube 6 of the spiral separation membrane element to an arbitrary outer circumference, it is necessary to analyze a portion that is somewhat away from the cut surface and is not affected by the cut, so an analysis is performed from a position of 2 inches to a position of 4 inches in a direction parallel to the longitudinal direction of the water collection tube from the cut surface.
  • a rectangular parallelepiped with a length of 4 inches, a width of 1 inch, and a depth of 2 inches, centered on the straight line L on a plane on the straight line L and tangent to the center point of the water collection tube, is set as the analysis range, 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, in the case of 4 inches, it is multiplied by 4/8 to make the length 1.75 inches and the width 0.5 inches.
  • the spiral separation membrane element can be cut by any method that does not destroy the internal flow path structure, and can be cut by, for example, a disk grinder, a water jet cutter, a band saw, or the like.
  • the height D O of the supply-side flow passage on the outer periphery is the average value of 20% of the flow passages from the outer periphery. For example, if there are 60 flow passages, the average value of 12 flow passages from the outer periphery is taken as D O.
  • the height D I of the supply-side flow passage on the inner periphery is the average value of 20% of the flow passages from the water collection pipe.
  • the height D C of the flow passage in the center is the average value of the flow passages existing between D O and D I , that is, 60% of the flow passages excluding 20% of the flow passages from the outer periphery and 20% of the flow passages from the water collection pipe.
  • spiral separation membrane element (Specified operating conditions of the spiral separation membrane element) When spiral separation membrane elements such as reverse osmosis membrane elements are operated under pressure, the pores of the support membrane are crushed, and a phenomenon called compaction occurs, in which the water permeability decreases. In this case, the feed-side flow channel becomes wider than the feed-side flow channel material, and the feed water is not sufficiently disturbed, resulting in a decrease in performance in some elements. Therefore, the flow channel structure of the spiral separation membrane element may change depending on the operating conditions.
  • the supply side flow path F formed by the separation membrane and the supply side flow path material located on a straight line connecting the center of the collection pipe and any outer periphery of the spiral separation membrane element is in a state in which the supply side flow path height on the outer periphery side and the supply side flow path height on the inner periphery side are smaller than the flow path height in the center between the outer periphery side and the inner periphery side.
  • the above-mentioned predetermined operating conditions refer to the operation of the target spiral separation membrane element under the recommended operating conditions for a predetermined time.
  • Each product spiral separation membrane element has recommended operating conditions, which are described in the product specifications.
  • the recommended operating conditions for a spiral separation membrane element suitable for treating brackish water are a pressure of 1.55 MPa, a supply water temperature of 25°C, a supply water NaCl concentration of 2000 mg/L, a recovery rate of 15%, and a supply water pH of 7.0
  • the recommended operating conditions for a spiral separation membrane element suitable for treating seawater are a pressure of 5.52 MPa, a supply water temperature of 25°C, a supply water NaCl concentration of 32000 mg/L, a recovery rate of 8%, and a supply water pH of 7.0.
  • the above-mentioned specified time may be the time from when the target spiral separation membrane element is started to operate under the recommended operating conditions until the thinning of the separation membrane progresses and the thinning reaches a steady state.
  • the degree of thinning of the separation membrane reaches a steady state after 24 hours of operation, but it may be operated for 24 hours or more until the steady state is reached. If the specified time is 24 hours or more of operation, the steady state is reliably reached.
  • the specified conditions are a supply water temperature of 25°C, a supply water NaCl concentration of 32,000 mg/L, and an aqueous NaCl solution of pH 7.0, and the height of the flow path on the supply side of the adhesive portion is measured after 24 hours of operation at 5.52 MPa under conditions of a recovery rate of 8%.
  • the ratio D C /D of the feed-side flow channel height D C at the center between the outer circumferential side and the inner circumferential side to the feed-side flow channel material thickness D is 1.00 or less. It is preferable that not only D C /D but also D F /D, D I , D O and the like satisfy the preferred aspects of the present invention even after operation under specified conditions.
  • the horizontal axis is the position of the flow channel
  • the vertical axis is the flow channel height
  • 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.
  • the flow channel may be DI > D O or D O > D I.
  • the mortar shape As the pattern of the flow channel height, there are a mortar shape, an inverted V shape, and a combination of a straight line and an inverted U shape like ⁇ , with the outer periphery side and the inner periphery side being flat, and the mortar shape as shown in Figure 5(c) is more preferable as a shape.
  • cone-shaped refers to a supply-side flow path height pattern in which, for a supply-side flow path F, the supply-side flow path height DO on the outer periphery and the supply-side flow path height DI on the inner periphery are smaller than the flow path height DC at the center between the outer periphery and the inner periphery, and the coefficient of variation (standard deviation/average value) of the flow path height DC at the center is 0.030 or less.
  • An example of a conventional supply-side flow channel height pattern other than that of the present invention is a uniform flow channel as shown in Figure 6.
  • the ratios DO/ DC and DI /DC of the outer peripheral supply side channel height DO and the inner peripheral supply side channel height DI to the central channel height DC, respectively, are preferably 0.95 or less.
  • DO/DC and DI/DC are in this range , the balance of the feed water flowing into the spiral separation membrane element is good, and concentration polarization and pressure loss can be reduced.
  • the average flow velocity on the outer and inner sides is reduced to about 74% compared to the center. Also, if D O /D C or D I /D C is too small, the pressure loss increases, leading to a decrease in performance. Therefore, it is more preferable that D O /D C and D I /D C are each 0.70 to 0.80.
  • the feed-side flow path material used in a spiral separation membrane element is generally composed 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 at multiple points to form a net shape.
  • the driving force for permeation is the transmembrane pressure difference, so increasing the transmembrane pressure is effective in improving water production.
  • 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, decrease the flow resistance, or decrease 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 supply side flow path material plays a role in disturbing the supply water, and in order to suppress membrane surface concentration polarization, it is important to create a vortex (flow) of the supply water on the membrane surface behind the fibrous material.
  • 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.
  • the thickness D of the feed-side channel material which is the average thickness of the feed-side channel material, is preferably in the range of 0.50 mm or more and 2.0 mm or less. If the thickness D 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 the 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.
  • the feed-side channel material is thinner than this range, it causes a large pressure loss or makes fouling more likely to progress. If the feed-side channel material is thicker than this range, it is not preferable from the viewpoint of handleability, but it can be adjusted to an appropriate rigidity by selecting an appropriate intersection pitch and material.
  • the thickness of the intersections and the supply-side flow path 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. Using the measurement mode, the diameters of any 30 points on the intersections or the thickness of the supply-side flow path material can be extracted and measured, and the average value can be calculated.
  • 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.
  • 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.
  • the ratio D F /D of the feed-side flow path height D F to the thickness D of the feed-side flow path material is preferably 1.00 or less.
  • the height of the feed-side flow path is rarely larger than the thickness of the feed-side flow path material during element manufacture. This is because the feed-side flow path material and the separation membrane are wrapped so that they are in firm contact with each other so that the feed-side flow path material does not move or pop out during operation.
  • the voids in the support membrane of the reverse osmosis membrane may be crushed and thinned, or the element may be loosened, causing the feed-side flow path to widen.
  • the feed-side flow path material exists to disturb the feed water, but if there is a feed-side flow path that is extremely wider than the feed-side flow path material, the feed water will flow into the widened flow path, and sufficient disturbance effect cannot be obtained. As a result, the membrane surface concentration polarization increases, leading to a decrease in salt rejection rate.
  • D F /D 1.00 or less various methods can be employed to make D F /D 1.00 or less, such as increasing the polymer concentration of the support membrane of the separation membrane so that the voids in the support membrane are less likely to collapse even when pressure is applied, or making the feed-side flow path material bite into the separation membrane during element production so that the separation membrane becomes thinner when pressure is applied, thereby allowing the feed-side flow path material to be in contact with the separation membrane even when the feed-side flow path widens.
  • the ratio D F /D of the feed-side channel height D F to the thickness D of the feed-side channel material is preferably 0.85 or more.
  • the feed-side channel material is used to turbulently stir the feed water, and by setting D F /D to 0.85 or more, the feed-side channel does not become too narrow, and an increase in pressure loss can be suppressed. In addition, under conditions of slow flow velocity, an extreme increase in membrane surface concentration polarization can be suppressed, and good separation performance can be maintained.
  • the flow paths may be narrowed by the adhesive.
  • the flow path height of the adhesive area is not used.
  • the flow path height pattern of the adhesive area is important, but since the flow path height pattern of the adhesive area and the flow path height pattern inside the element tend to be the same, the flow path height pattern inside the element can be applied.
  • the ratio D C /D of the channel height D C at the center to the thickness D of the feed-side channel is 1.00 or less.
  • D C /D is 1.00 or less, there is no region where the feed-side channel material floats from the separation membrane, and there is no concern that the feed-side channel material will shift. In terms of performance, the feed-side channel material does not float from the separation membrane, and a sufficient disturbance effect is obtained.
  • Permeation side flow path 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 flow passage material 4 is disposed between the separation membranes 3, forming a permeate-side flow passage.
  • a permeate-side flow passage material 4 is disposed between the separation membranes 3, forming a permeate-side flow passage.
  • the material of the permeate-side flow passage material and tricot, nonwoven fabric, a porous sheet with protrusions attached, a film with an uneven shape and perforations, and an uneven nonwoven fabric can be used.
  • protrusions that function as the permeate-side flow passage material may be fixed to the permeate side of the separation membrane.
  • the separation membrane elements may be connected in series or parallel and housed in a pressure vessel to be used as a separation membrane module.
  • the above separation membrane elements and separation membrane modules can be combined with pumps that supply fluids to them and devices that pretreat the fluids to form a fluid separation device.
  • this separation device for example, it is possible to separate the supply water into permeated water, such as drinking water, and concentrated water that did not permeate the membrane, thereby obtaining water that meets the purpose.
  • 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.
  • the salt rejection rate decreases, but as the temperature decreases, the membrane permeation flux also decreases, so a temperature between 5°C and 45°C is preferable.
  • 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 membrane deterioration is also suppressed.
  • 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.
  • 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 Total Dissolved Solids
  • mass ratio assuming that 1 L is 1 kg.
  • the element was cut into a fan shape at an angle of 60 degrees with the water collection tube as the central axis to obtain an observation sample.
  • the fan-shaped sample was then dried in a vacuum oven set at 40 ° C. until there was no weight change.
  • x m300 was used to scan under conditions of a tube current of 100 ⁇ A, a tube voltage of 150 kV, and a resolution of 19.8 ⁇ m, and a 3D image was obtained. Then, analysis was performed using VGSTUDIO MAX manufactured by VOLUMEGRAPHICS to measure the height of the supply side flow channel.
  • the resolution of the X-ray CT measurement is not limited to 19.8 ⁇ m, and may be 20.0 ⁇ m or less, as long as the analysis range is within the range from the water collection tube to the outer peripheral filament winding.
  • the distance from the water collection tube to the outer contour of the filament winding when the cut fan-shaped sample is returned to the cylindrical sample be within a range of ⁇ 0.5% or less compared to the average value of the distances at four points shifted 60 degrees clockwise from the cut surface of the cut cylindrical sample.
  • the height of the supply side flow path can be measured from the volume of the supply side flow path.
  • the supply side flow path F formed by the separation membrane located on the straight line L connecting the center of the water collection pipe and an arbitrary outer periphery and the supply side flow path material was divided into rectangular areas of 4 inches long x 1 inch wide x 2 inches deep, the spatial volume of each flow path was measured, and the volume of the supply side flow path corresponding to each flow path was obtained.
  • the volume is smaller than that of the other flow paths, so that the flow path height cannot be compared fairly. Therefore, only the flow paths in which both ends of the flow path are in contact with the vertical line in a rectangular area of 4 inches long x 1 inch wide were analyzed. Since the obtained flow path volume is a value including the supply side flow path material, the flow path volume ignoring the supply side flow path material can be obtained by dividing it by the porosity of the supply side flow path material. The length of the arc was measured using ImageJ. The line selection tool was traced 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 path, the upper and lower arcs were measured and their average value was used as the arc length.
  • the depth of the flow path was a known value within the analysis range, and the feed side flow path height D F was obtained using the arc length and the porosity of the feed side flow path material according to formula (2).
  • the feed-side channel material was cut to a size of 50 cm x 50 cm, and the weight was measured to calculate the weight per unit area (kg/ m2 ). The obtained value was divided by the thickness of the feed-side channel material to calculate the weight per unit volume (kg/ m3 ). The porosity of the feed-side channel material was calculated using the material density (kg/ m3 ) according to formula (3).
  • Example> Preparation of spiral separation membrane element
  • a 16.0 mass % DMF solution of polysulfone was cast to a thickness of 180 ⁇ m on a nonwoven fabric made of polyethylene terephthalate fibers (fineness: 1 dtex, thickness: approximately 90 ⁇ m, air permeability: 1 cc/cm 2 /sec, density 0.80 g/cm 3 ) at room temperature (25° C.), 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 130 ⁇ m) made of a fiber-reinforced polysulfone support membrane.
  • the surface of the polysulfone layer of the porous support membrane was immersed in an aqueous solution containing 1.4 mass% of m-PDA and 1.0 weight% of ⁇ -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.
  • n-decane solution containing 0.07% by mass of trimesoyl chloride was applied so that the surface of the membrane was completely wetted, and then the membrane was left to stand for 1 minute. After that, excess solution was removed from the membrane with an air blower, and the membrane was washed with hot water at 80°C for 1 minute to obtain a composite separation membrane roll.
  • the separation membrane thus obtained was folded and cut so that the effective area of the separation membrane element was 40.9 m2 , and a polypropylene net (thickness: 0.7 mm) was sandwiched therebetween as a feed water side flow path material to prepare a separation membrane leaf.
  • a tricot (thickness: 0.26 mm) was laminated on the permeation side of the obtained separation membrane leaf as the permeation side flow path material, a leaf adhesive was applied, and the laminate was wound around a PVC (polyvinyl chloride) water collection pipe (width: 1016 mm, diameter: 47.6 mm, number of holes: 40 x one linear row) while gradually reducing the winding tension until 20% of the laminate was wrapped around it (step a). Then, the winding tension was maintained or gradually increased or decreased according to the flow path pattern until 80% of the laminate was wrapped around it (step b). Finally, the winding tension was gradually increased again (step c) and the element was spirally wound. The outer periphery of the wrapped element was fixed with tape, and then the edges were cut at both ends and end plates were attached to produce a separation membrane element with a diameter of 8 inches, from which feed water was supplied from one side and concentrated water was discharged.
  • PVC polyvinyl chloride
  • the separation membrane element was placed in a pressure vessel, and an aqueous NaCl solution with a temperature of 25° C., a concentration of 32,000 mg/L, and a pH of 7.0 was used as the feed water, and the operating pressure was 5.52 MPa and the recovery rate was 8%. After 24 hours of operation, sampling was carried out for 1 minute, and the amount of water permeated (gallons) per day was expressed as the amount of freshwater produced (GPD (gallons/day)).
  • TDS removal rate Removal rate (TDS removal rate)
  • TDS removal rate (%) 100 ⁇ 1-(TDS concentration in permeate water/TDS concentration in feed water) ⁇ (Element differential pressure)
  • the upstream side (feed water side) and downstream side (concentrate water side) of the cylindrical pressure vessel in which the separation membrane element was loaded were connected by piping via a Nagano Keiki differential pressure gauge (type DG16), and the element differential pressure during operation was measured.
  • the operating conditions were a feed water flow rate of 150 L/min, an operating pressure of 1.0 MPa, and reverse osmosis membrane treated water was used as the feed water.
  • the cock of the permeate water piping was closed, and the operation was performed in a state in which membrane filtration was essentially not possible, that is, the entire amount of the feed water was discharged as concentrated water, and the element differential pressure (kPa) was measured.
  • Example 1 The prepared separation membrane element was placed in a pressure vessel and evaluated under the above-mentioned conditions. The results are shown in Table 1.
  • Example 2 A separation membrane element was produced in the same manner as in Example 1, except that the feed side flow paths were as shown in Tables 1 and 2.
  • the separation membrane element was placed in a pressure vessel and each performance was evaluated under the same conditions as in Example 1, with the results shown in Table 1.
  • Comparative Example (Comparative Examples 1 and 2) A separation membrane element was produced in the same manner as in Example 1, except that the feed side flow path was as shown in Table 2.
  • the separation membrane element was placed in a pressure vessel and each performance was evaluated under the conditions described above, with the results shown in Table 2.
  • the separation membrane elements of Examples 1 to 8 can be said to have excellent and stable separation performance, sufficiently disturbing the supply water while minimizing pressure loss and suppressing membrane surface concentration polarization.
  • the membrane element of the present invention is particularly suitable for use as an RO water purifier and for desalinizing brackish water or seawater.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

L'invention concerne un élément de membrane de séparation avec lequel il est possible de réduire la polarisation de concentration d'une surface de membrane tout en réduisant la résistance à l'écoulement dans un trajet d'écoulement côté alimentation lorsque l'élément de membrane de séparation est actionné. Cet élément de membrane de séparation comprend un tube de collecte d'eau, une membrane de séparation, un élément de trajet d'écoulement côté alimentation et un élément de trajet d'écoulement côté transmission. Dans une section transversale perpendiculaire à la direction axiale du tube de collecte d'eau dans l'élément de membrane de séparation, par rapport à un trajet d'écoulement côté alimentation (F) qui est formé par l'élément de trajet d'écoulement côté alimentation et la membrane de séparation et qui est positionné sur une ligne droite reliant le centre du tube de collecte d'eau à une périphérie externe discrétionnaire, la hauteur du trajet d'écoulement côté alimentation entre un côté périphérique externe et un côté périphérique interne est inférieure à la hauteur de trajet d'écoulement d'une section centrale entre le côté périphérique externe et le côté périphérique interne.
PCT/JP2024/008885 2023-03-10 2024-03-07 Élément de membrane de séparation en spirale Pending WO2024190625A1 (fr)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017047417A (ja) * 2015-08-31 2017-03-09 東レ株式会社 分離膜モジュール、分離膜エレメントおよびテレスコープ防止板
JP2020082068A (ja) * 2018-11-19 2020-06-04 日東電工株式会社 分離膜エレメント、分離膜モジュール及び浄水器

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017047417A (ja) * 2015-08-31 2017-03-09 東レ株式会社 分離膜モジュール、分離膜エレメントおよびテレスコープ防止板
JP2020082068A (ja) * 2018-11-19 2020-06-04 日東電工株式会社 分離膜エレメント、分離膜モジュール及び浄水器

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