CN111195483B - Separation membrane element, separation membrane module, and water purifier - Google Patents

Separation membrane element, separation membrane module, and water purifier Download PDF

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Publication number
CN111195483B
CN111195483B CN201910514538.7A CN201910514538A CN111195483B CN 111195483 B CN111195483 B CN 111195483B CN 201910514538 A CN201910514538 A CN 201910514538A CN 111195483 B CN111195483 B CN 111195483B
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Prior art keywords
raw water
separation membrane
flow path
membrane element
end surface
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CN201910514538.7A
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CN111195483A (en
Inventor
宇田康弘
冈崎友叶
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Nitto Denko Corp
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Nitto Denko Corp
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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
    • B01D63/08—Flat membrane modules
    • 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
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Abstract

The invention provides a separation membrane element, a separation membrane module, and a water purifier, wherein the operation performance of the separation membrane element is not easy to reduce even if the separation membrane element is operated at a high recovery rate. A separation membrane element (10) is provided with: a header pipe (21); a separation membrane (12) disposed around the liquid collection tube; a first end surface (10 p) which is one end surface of the separation membrane in the longitudinal direction of the liquid collecting pipe; a second end surface (10 q) which is the other end surface of the separation membrane in the longitudinal direction of the liquid collection tube; a first raw liquid channel (15) extending linearly from the first end surface to the second end surface; and a second raw liquid channel (16) extending linearly from the second end surface to the first end surface. The raw liquid flows into the first raw liquid channel (15) through the first end surface (10 p), flows out of the first raw liquid channel (15) through the second end surface (10 q), and then flows into the second raw liquid channel (16) through the second end surface (10 q).

Description

Separation membrane element, separation membrane module, and water purifier
Technical Field
The invention relates to a separation membrane element, a separation membrane module, and a water purifier.
Background
Separation membrane elements are used in various fields such as desalination of sea water, production of pure water, purification of tap water, wastewater treatment, and excavation of crude oil. For example, a spiral separation membrane element includes a water collection pipe and a separation membrane wound around the water collection pipe. The raw water to be treated flows through a raw water flow path defined between the separation membranes. The permeated water is collected in the water collecting pipe through the permeated water flow path.
When raw water is treated using a separation membrane element, it is desirable to be able to recover a large amount of permeate from the raw water. Patent document 1 describes an RO device having a tree structure capable of performing a stable operation over a long period of time.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 2007-125527
Patent document 2: U.S. patent application publication No. 2014/0042080
Disclosure of Invention
Problems to be solved by the invention
However, sometimes a tree-like structure cannot be adopted or a single-stage use of a separation membrane element is required. In this case, it is not easy to sufficiently exert the performance of the separation membrane element.
When the separation membrane element is used in a single stage to perform high recovery rate operation, the linear velocity of raw water is greatly reduced in the vicinity of the outlet of the raw water flow path, and the salt rejection rate and the flow rate of permeated water are greatly reduced. This is because the linear velocity of the raw water decreases, and the stirring effect of the raw water by the raw water spacer decreases, and the concentration polarization layer progresses. This reduces the salt rejection and the flow rate of the permeated water.
The reverse osmosis membrane element described in patent document 2 has a meandering raw water flow path. However, the tortuous raw water flow path creates a plurality of stagnant zones. The linear velocity of the raw water in the stagnant zone is very slow, and therefore the stagnant zone hardly contributes to the separation function.
The invention provides a separation membrane element which is not easy to reduce the operation performance even if high recovery rate operation is carried out.
Means for solving the problems
The present invention provides a separation membrane element provided with: a liquid collecting pipe; a separation membrane disposed around the liquid collecting tube; a first end surface which is one end surface of the separation membrane in the longitudinal direction of the liquid collecting tube; a second end surface which is the other end surface of the separation membrane in the longitudinal direction of the liquid collecting tube; a first raw liquid flow path extending linearly from the first end surface to the second end surface; and a second raw liquid flow path extending linearly from the second end surface to the first end surface, the raw liquid flowing into the first raw liquid flow path through the first end surface, flowing out of the first raw liquid flow path through the second end surface, and then flowing into the second raw liquid flow path through the second end surface.
In another aspect, the present invention provides a separation membrane element including: a plurality of laminated separation membranes having a flat and rectangular shape; a first end face which is one end face selected from a pair of end faces facing each other of the plurality of laminated separation membranes; a second end surface which is the other end surface selected from the pair of end surfaces; a first raw liquid flow path extending linearly from the first end surface to the second end surface; and a second raw liquid channel extending linearly from the second end surface to the first end surface, wherein the raw liquid flows into the first raw liquid channel through the first end surface, flows out of the first raw liquid channel through the second end surface, and then flows into the second raw liquid channel through the second end surface.
In another aspect, the present invention is a separation membrane element including: a liquid collecting pipe; and a plurality of dividing elements arranged in a circumferential direction of the header pipe, the plurality of dividing elements including: at least one dividing element forming a first raw liquid flow path extending in parallel to the longitudinal direction of the liquid collecting tube; and at least one dividing element that forms a second raw liquid flow path that extends parallel to the longitudinal direction of the header pipe, wherein each of the plurality of dividing elements includes an outer wall portion and a separation membrane disposed inside the outer wall portion, and the flow of the raw liquid along the circumferential direction of the header pipe is blocked by the outer wall portion of each of the plurality of dividing elements.
Effects of the invention
In the separation membrane element of the present invention, the total length of the raw liquid flow paths is 2 times or more the distance between the first end face and the second end face. By reducing the cross-sectional area of the raw liquid flow path and increasing the total length of the raw liquid flow paths, the linear velocity of the raw liquid can be increased and the progress of the concentration polarization layer can be suppressed. In other words, the separation membrane element of the present invention is not likely to have a reduced operating performance (salt rejection rate and flow rate of the permeate) even when a high recovery rate operation is performed.
Drawings
Fig. 1 is a perspective view of a separation membrane element according to an embodiment of the present invention.
Fig. 2 is a longitudinal sectional view of the separation membrane element shown in fig. 1.
Fig. 3 is an expanded perspective view of the separation membrane element shown in fig. 1.
Fig. 4A is a front view of the separation membrane element when viewed from the first end face or the second end face.
Fig. 4B is a partially enlarged perspective view of the first end face or the second end face.
Fig. 5 is a diagram illustrating a method of integrating a separator and a raw water separator.
Fig. 6 is a perspective view of a raw water spacer according to a modification.
Fig. 7A is a schematic view showing another example of the first angle and the second angle.
Fig. 7B is a schematic view showing still another example of the first angle and the second angle.
Fig. 7C is a schematic view showing still another example of the first angle and the second angle.
Fig. 8A is a perspective view of a separation membrane element according to modification 1.
Fig. 8B is a schematic plan view of the separation membrane element when viewed from the second end face.
Fig. 8C is a schematic plan view of the separation membrane element as viewed from the first end surface.
Fig. 9A is a perspective view of a separation membrane element according to modification 2.
Fig. 9B is a schematic front view of the separation membrane element when viewed from the first end face or the second end face.
Fig. 10 is a development view of 4 raw water spacers used in a separation membrane element of modification 1.
Fig. 11 is a diagram showing a curve used for determining the position of the spacer.
Fig. 12A is a schematic plan view of the separation membrane element according to embodiment 2 when viewed from the first end face or the second end face.
Fig. 12B is a developed view of a separation membrane used in the separation membrane element according to embodiment 2.
Fig. 12C is an exploded cross-sectional view of a separation membrane element according to embodiment 2.
Fig. 13A is a schematic perspective view of a separation membrane element according to embodiment 3.
Fig. 13B is a sectional view of the separation membrane element shown in fig. 13A.
Fig. 14A is a schematic plan view of the separation membrane element according to embodiment 4 when viewed from the first end face or the second end face.
Fig. 14B is a sectional view of the sectioning element.
Fig. 14C is a developed view of a separation membrane used for the partitioning member.
Fig. 14D is an exploded sectional view of the sectioning element.
Fig. 14E is a longitudinal sectional view of a separation membrane element according to embodiment 4.
Fig. 14F is another longitudinal sectional view of the separation membrane element according to embodiment 4.
Fig. 15A is a sectional view of another sectioning element.
Fig. 15B is a cross-sectional view of yet another sectioning element.
Fig. 15C is a cross-sectional view of yet another sectioning element.
Fig. 16 is a sectional view of a separation membrane module according to an embodiment of the present invention.
Fig. 17A is a cross-sectional view of a separation membrane module according to a modification.
Fig. 17B is a cross-sectional view of a separation membrane module according to another modification.
Fig. 17C is a cross-sectional view of a separation membrane module according to still another modification.
Fig. 17D is a sectional view of a separation membrane module according to still another modification.
Fig. 17E is a sectional view of a separation membrane module according to still another modification.
Fig. 18A is a perspective view of an example of the cover.
Fig. 18B is a perspective view of an example of another cover.
Fig. 19 is a view showing a modification of the cover shown in fig. 18A.
Fig. 20 is a perspective view of an example of a cover used in the separation membrane module shown in fig. 17C.
Fig. 21 is a front view of a water purifier according to an embodiment of the present invention.
Fig. 22 is a perspective view of a separation membrane element of a reference example.
Fig. 23 is a graph showing the relationship between the recovery rate and the flow rate of permeated water in the separation membrane elements of examples and reference examples.
Fig. 24 is a diagram illustrating a problem of the reverse osmosis membrane element described in patent document 2.
Detailed Description
Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the following embodiments.
Fig. 1 schematically shows the structure of a separation membrane element 10 according to the present embodiment. As shown in fig. 1, the separation membrane element 10 includes a first end surface 10p, a second end surface 10q, a first raw water channel 15, and a second raw water channel 16. The first end face 10p and the second end face 10q are end faces facing each other. The first raw water flow path 15 extends from the first end surface 10p to the second end surface 10q. The second raw water channel 16 extends from the second end surface 10q to the first end surface 10p. The first raw water flow path 15 is connected in series to the second raw water flow path 16.
As the liquid that can be treated (filtered) by the separation membrane element 10, water (raw water) can be taken out. In the present specification, for simplicity, the term "water" is used as a representative of the liquid.
Specifically, the separation membrane element 10 includes a header 21 and a stack 22. The laminate 22 includes the separation membrane 12 and is disposed around the water collection pipe 21. The first raw water flow path 15 and the second raw water flow path 16 are flow paths formed inside the stacked body 22. The first end surface 10p is one end surface of the separation membrane 12 in the longitudinal direction of the header pipe 21. The second end surface 10q is the other end surface of the separation membrane 12 in the longitudinal direction of the water collection pipe 21.
As shown by arrows, in the separation membrane element 10, raw water flows into the first raw water channel 15 through the first end face 10p, and flows out of the first raw water channel 15 through the second end face 10q. Thereafter, the raw water flows into the second raw water flow path 16 through the second end surface 10q, and flows out of the second raw water flow path 16 through the first end surface 10p. The raw water reciprocates between the first end face 10p and the second end face 10q.
In the conventional separation membrane element, the length of the raw water flow path is equal to the distance between the end faces of the separation membrane element. For example, when the operation is performed with the permeate recovery rate set to 50%, the flow rate of the raw water near the outlet of the raw water flow path is about half of the flow rate of the raw water near the inlet. Therefore, the linear velocity of the raw water is significantly reduced near the outlet of the raw water flow path. As a result, a concentration polarization layer develops, and the salt rejection rate and the flow rate of permeated water decrease.
In contrast, in the separation membrane element 10 of the present embodiment, the total length of the raw water flow paths is 2 times or more the distance between the first end face 10p and the second end face 10q. By reducing the cross-sectional area of the raw water flow path and increasing the total length of the raw water flow paths, the linear velocity of the raw water can be increased and the progress of the concentration polarization layer can be suppressed. In other words, the separation membrane element 10 of the present embodiment is not likely to deteriorate in operating performance (salt rejection rate and flow rate of permeated water) even when high recovery rate operation is performed. In addition, by increasing the linear velocity of the raw water, adhesion of scale can be suppressed.
In particular, when the flow path cross-sectional area of the raw water flow path is reduced stepwise as the raw water flows downstream in the raw water flow direction, the above-described effect of increasing the linear velocity of the raw water can be more sufficiently obtained.
As shown in fig. 24, the reverse osmosis membrane element described in patent document 2 includes a meandering raw water channel. The total length of the raw water flow paths is 2 times or more the distance between the end faces of the reverse osmosis membrane elements. However, the meandering raw water flow path generates a plurality of stagnation regions SA. The linear velocity of the raw water in the stagnation region SA is very low. In other words, the stagnation region SA hardly contributes to the separation function.
In contrast, in the separation membrane element 10 of the present embodiment, raw water flows out of the first raw water channel 15 through the second end face 10q, and then flows into the second raw water channel 16 through the second end face 10q. In other words, the raw water is once discharged to the outside from the first raw water flow path 15, which is a space between the separation membranes, and flows into the second raw water flow path 16, which is another space between the separation membranes. Since the raw water flows straight in each raw water flow path and the flow direction is not changed, stagnation regions are less likely to occur in both the first raw water flow path 15 and the second raw water flow path 16.
In the present embodiment, the first raw water flow passage 15 and the second raw water flow passage 16 are not bent, but extend linearly between the first end surface 10p and the second end surface 10q. The raw water flows linearly through the raw water flow paths. With this configuration, the formation of the stagnant area can be more reliably prevented.
In the present specification, "straight" means that the flow direction of raw water does not change greatly from the first end face 10p to the second end face 10q or from the second end face 10q to the first end face 10p. That is, the flow path extending linearly means a flow path having a shape and a structure in which a stagnation region is not substantially formed between the first end surface 10p and the second end surface 10q. The flow path may have a portion slightly accompanied by bending, twisting, expansion, contraction, or the like.
In the present embodiment, the length of the first raw water flow path 15 is equal to the length of the second raw water flow path 16. The flow direction of the raw water in the first raw water flow path 15 is parallel to the flow direction of the raw water in the second raw water flow path 16. In detail, the flow direction of the raw water in the first raw water flow path 15 is opposite to the flow direction of the raw water in the second raw water flow path 16 by 180 degrees. The flow direction of the raw water in the first raw water flow path 15 and the flow direction of the raw water in the second raw water flow path 16 are parallel to the longitudinal direction of the water collecting pipe 21. When moving from the first raw water flow path 15 to the second raw water flow path 16, the flow direction of the raw water is reversed by 180 degrees. With such a configuration, the separation membrane element 10 can be configured compactly.
The second raw water channel 16 may have a channel cross-sectional area smaller than that of the first raw water channel 15, for example. With this configuration, the linear velocity of the raw water in the second raw water flow path 16 is less likely to decrease. Therefore, the separation membrane element 10 is suitable for high recovery rate operation.
The flow path cross-sectional area of the first raw water flow path 15 can be calculated by dividing the volume of the space as the first raw water flow path 15 by the length of the first raw water flow path 15 in the longitudinal direction of the water collection pipe 21. The length of the first raw water flow channel 15 in the longitudinal direction of the water collection pipe 21 is equal to the shortest distance between the first end surface 10p and the second end surface 10q. The flow path sectional area of the second raw water flow path 16 can also be calculated by the same method.
In the present embodiment, the area of the first raw water channel 15 in a cross section perpendicular to a line segment connecting the first end face 10p and the second end face 10q at the shortest distance is constant. In other words, the flow path cross-sectional area of the first raw water flow path 15 is represented by the area of the first raw water flow path 15 in a cross section perpendicular to a line segment connecting the first end face 10p and the second end face 10q at the shortest distance. With this configuration, the formation of the stagnant area can be more reliably prevented. "a cross section perpendicular to a line segment connecting the first end surface 10p and the second end surface 10q at the shortest distance" is a cross section perpendicular to the longitudinal direction of the water collection pipe 21.
Similarly, the area of the second raw water channel 16 in a cross section perpendicular to a line segment connecting the first end surface 10p and the second end surface 10q at the shortest distance is constant. In other words, the flow path cross-sectional area of the second raw water flow path 16 is represented by the area of the second raw water flow path 16 in a cross section perpendicular to a line segment connecting the first end face 10p and the second end face 10q at the shortest distance. With this configuration, the formation of the stagnant area can be more reliably prevented.
The inlet of the first raw water flow path 15 is located at the first end surface 10p. The outlet of the first raw water channel 15 is located at the second end face 10q. The inlet of the second raw water flow path 16 is located at the second end face 10q. The outlet of the second raw water flow path 16 is located at the first end surface 10p. In other words, the first raw water channel 15 is open at the first end surface 10p and the second end surface 10q, respectively. The second raw water channel 16 is open at the first end surface 10p and the second end surface 10q, respectively.
Fig. 2 schematically shows a longitudinal section of the separation membrane element 10. As shown in fig. 2, the separation membrane element 10 further includes a communication channel 27. The communication flow path 27 connects the outlet of the first raw water flow path 15 at the second end face 10q and the inlet of the second raw water flow path 16 at the second end face 10q. The communication passage 27 enables the raw water to be transferred from the first raw water passage 15 to the second raw water passage 16.
In the present embodiment, communication flow channel 27 may be an internal space of cover 28 covering second end face 10q. Cover 28 covers second end face 10q to form an isolation chamber serving as communication flow channel 27. With this configuration, the raw water can be transferred from the first raw water channel 15 to the second raw water channel 16. The cover 28 is attached to the laminate 22, for example. The separation membrane element 10 may be provided with a cylindrical case covering the separation membrane 12. The cover 28 may be attached to an end of the cylindrical case. As will be described later, the cover 28 may be a part of a housing that houses the entire separation membrane element 10.
The separation membrane element 10 may also include an adapter including a partition wall that partitions an inlet of the first raw water channel 15 in the first end surface 10p and an outlet of the second raw water channel 16 in the first end surface 10p. The adapter prevents mixing of raw water to be treated and concentrated raw water (concentrated water), guides the raw water to be treated to the first raw water passage 15, and collects the concentrated water from the second raw water passage 16. Such an adapter may be attached to the laminate 22, or may be a part of a housing that houses the entire separation membrane element 10.
Fig. 3 shows a separation membrane element 10 shown in fig. 1 partially developed. The laminate 22 is composed of the separation membrane 12, the raw water spacer 13, and the permeated water spacer 14. The end face of the separation membrane 12 constitutes an end face of the laminate 22. Specifically, the stacked body 22 is composed of a plurality of separation membranes 12, a plurality of raw water spacers 13, and a plurality of permeated water spacers 14. The raw water spacer 13 and the permeated water spacer 14 are, for example, net-shaped members. As the raw water spacer 13, for example, a press-out net having a diamond-shaped opening is used. As the permeable water spacer 14, tricot knitted fabric, plain-woven fabric, or the like may be used.
The plurality of separation membranes 12 are overlapped with each other, sealed at the 3 sides in a manner of having a bag-shaped structure, and wound around the water collecting pipe 21. The raw water spacer 13 is disposed between the separation membranes 12 and 12 so as to be located outside the bag-like structure. The raw water spacer 13 secures a space as a raw water flow path between the separation membrane 12 and the separation membrane 12. The raw water flow path includes a first raw water flow path 15 and a second raw water flow path 16. The permeated water spacer 14 is disposed between the separation membrane 12 and the separation membrane 12 so as to be positioned inside the bag-like structure. The permeated water spacer 14 secures a space as a permeated water flow path between the separation membrane 12 and the separation membrane 12. The membrane leaf 11 is composed of 1 pair of separation membranes 12 and a water-permeable spacer 14. The open ends of the membrane leaves 11 are connected to the water collecting pipe 21 so that the permeated water flow path communicates with the water collecting pipe 21.
The first end surface 10p and the second end surface 10q may be end surfaces of the separation membrane 12 in the longitudinal direction of the water collection pipe 21. According to such a configuration, the first raw water flow path 15 and the second raw water flow path 16 are formed from the end portion to the end portion of the separation membrane 12, and therefore the separation function of the separation membrane 12 can be exhibited to the maximum.
The separation membrane element 10 of the present embodiment may be a spiral-type separation membrane element. Materials, structures, characteristics, manufacturing methods, and the like of spiral separation membrane elements are well known. Therefore, the technology described in the present specification can be applied to a conventional spiral separation membrane element with minimal design changes.
The separation membrane 12 is, for example, a reverse osmosis membrane, a nanofiltration membrane, an ultrafiltration membrane, or a microfiltration membrane. Typically, the separation membrane 12 is a reverse osmosis or nanofiltration membrane. The separation membrane 12 may be a composite semipermeable membrane having a porous support and a separation function layer supported by the porous support. As the porous support, an ultrafiltration membrane in which a microporous layer is formed on a nonwoven fabric can be used. Examples of the material of the microporous layer include polysulfone, polyarylethersulfone, polyimide, polyvinylidene fluoride, and the like. The separating functional layer may be composed of polyamide.
The water collecting pipe 21 collects the permeated water having permeated through each separation membrane 12 and guides the permeated water to the outside of the separation membrane element 10. The water collection pipe 21 has a plurality of through holes 21h provided at predetermined intervals along the longitudinal direction thereof. The permeated water flows into the header 21 through these through holes 21h.
Fig. 4A is a front view of the separation membrane element 10 when viewed from the first end face 10p or the second end face 10q. In the present embodiment, the first raw water flow path 15 is a flow path that occupies a region of the first angle θ 1 in the circumferential direction of the water collection pipe 21. The second raw water flow path 16 is a flow path occupying a region of a second angle θ 2 in the circumferential direction of the water collection pipe 21. The first angle θ 1 is different from the second angle θ 2. In detail, the first angle θ 1 is larger than the second angle θ 2. With this configuration, a decrease in the linear velocity of the raw water in the second raw water channel 16 can be sufficiently suppressed. Further, by appropriately changing the first angle θ 1 and the second angle θ 2, the linear velocity of the raw water in the first raw water flow path 15 and the linear velocity of the raw water in the second raw water flow path 16 can be made uniform.
In the example of fig. 4A, the first angle θ 1 is 240 degrees and the second angle θ 2 is 120 degrees. Therefore, the ratio of the flow path sectional area of the second raw water flow path 16 to the flow path sectional area of the first raw water flow path 15 is 0.5.
The separation membrane element 10 is further provided with a plurality of separators 23. The plurality of partitions 23 partition the first raw water flow path 15 and the second raw water flow path 16, respectively. The plurality of partitions 23 extend in the lengthwise direction of the header pipe 21, respectively. With this configuration, the first raw water flow path 15 and the second raw water flow path 16 can be reliably separated. It is possible to prevent the raw water from flowing from the first raw water flow path 15 to the second raw water flow path 16 in a short path.
The separator 23 extends from the first end face 10p to the second end face 10q. With this configuration, the first raw water flow path 15 and the second raw water flow path 16 can be reliably separated.
Fig. 4B shows a part of the first end face 10p or the second end face 10q in an enlarged manner. As shown in fig. 4B, a raw water spacer 13 is disposed between the membrane leaves 11 and the membrane leaves 11. In this example, the space on the right side of the partition 23 is the first raw water flow path 15, and the space on the left side of the partition 23 is the second raw water flow path 16. The partition 23 is integrated with the raw water spacer 13. In other words, the partition 23 may be a part of the raw water spacer 13. With this configuration, the first raw water flow path 15 and the second raw water flow path 16 can be reliably separated. It is possible to prevent the raw water from flowing from the first raw water flow path 15 to the second raw water flow path 16 in a short path. Each separator 23 has a belt-like shape.
As shown in fig. 4A, the plurality of partitions 23 include a plurality of first partitions 231 arranged in a radial direction of the water collection pipe 21 at a first angular position P1 and a plurality of second partitions 232 arranged in a radial direction of the water collection pipe 21 at a second angular position P2. The first and second angular positions P1 and P2 are predetermined angular positions in the circumferential direction of the header pipe 21. With this configuration, the first raw water flow path 15 and the second raw water flow path 16 can be reliably separated. It is possible to prevent the raw water from flowing from the first raw water flow path 15 to the second raw water flow path 16 in a short path.
Fig. 5 shows an example of a method of integrating the partition 23 with the raw water partition 13. Specifically, a tape 23a as a material member of the separator 23 is disposed at a predetermined position of the raw water spacer 13. The heat-resistant sheet 25 sandwiches the raw water spacer 13 and the tape 23a, and applies heat and pressure to the raw water spacer 13 and the tape 23a at a temperature at which the tape 23a melts and the raw water spacer 13 does not melt. The heat-resistant sheet 25 is a heat-resistant sheet whose surface has been subjected to a peeling treatment using silicone or the like. The separator 23 integrated with the raw water spacer 13 is formed by melting and solidifying the tape 23a. The separator 23 is made of, for example, a hot-melt resin. According to the method shown in fig. 5, the partition 23 can be easily integrated with the raw water partition 13. The thickness of the partition 23 can be made to coincide with the thickness of the raw water spacer 13, and the partition 23 of a smooth surface can be formed. After the separator 23 is formed, the heat-resistant sheet 25 is peeled off and removed from the raw water spacer 13. The wound body is reheated after the membrane leaves 11 and the raw water spacer 13 are wound around the water collecting pipe 21, whereby the sealing property between the separator 23 and the separation membrane 12 can also be improved.
The separator 23 may also be made of a silicone sealant. When a silicone sealant is used, a wax paper can be used instead of the heat-resistant sheet 25.
Fig. 6 shows a raw water spacer 131 according to a modification. The raw water spacer 131 includes a sheet-like body 132 having a plurality of openings, and a plurality of spacers 23 integrated with the body 132. The plurality of separators 23 are arranged in parallel with each other. The partition 23 has a thickness exceeding that of the main body portion 132. Such a raw water spacer 131 can be made in a roll-to-roll manner by processing a sheet material. The raw water spacer having the partition 23 may also be made by alternately connecting a mesh having a plurality of openings and a belt-like member as the partition 23.
Fig. 7A, 7B, and 7C show other examples of the first angle θ 1 and the second angle θ 2 described with reference to fig. 4A. The first angle θ 1 is an angle of a region occupied by the first raw water flow path 15. The second angle θ 2 is an angle of a region occupied by the second raw water flow path 16. As shown in fig. 7A, for example, the first angle θ 1 is 257 degrees, and the second angle θ 2 is 103 degrees. As shown in fig. 7B, for example, the first angle θ 1 is 270 degrees, and the second angle θ 2 is 90 degrees. As shown in fig. 7C, for example, the first angle θ 1 is 288 degrees and the second angle θ 2 is 72 degrees. The first angle θ 1 and the second angle θ 2 can be set appropriately so as to maintain the linear velocity of the raw water sufficiently.
(modification 1)
Fig. 8A schematically shows the structure of a separation membrane element 20 according to modification 1. Fig. 8B is a schematic plan view of the separation membrane element 20 when viewed from the second end face 10q. Fig. 8C is a schematic plan view of the separation membrane element 20 as viewed from the first end face 10p. All the descriptions relating to the separation membrane element 10 can be applied to the separation membrane element 20 as long as the technical contradiction is not present.
As shown in fig. 8A, the separation membrane element 20 includes, in addition to the separation membrane element 10, a third raw water channel 17 extending from the first end face 10p to the second end face 10q. As shown by arrows, in the separation membrane element 20, raw water flows into the first raw water channel 15 through the first end face 10p, and flows out of the first raw water channel 15 through the second end face 10q. Then, the raw water flows into the second raw water flow path 16 through the second end surface 10q, and flows out of the second raw water flow path 16 through the first end surface 10p. The raw water flows into the third raw water flow path 17 through the first end surface 10p, and flows out of the third raw water flow path 17 through the second end surface 10q. In other words, the raw water reciprocates 1.5 times between the first end face 10p and the second end face 10q. According to this modification, the total length of the raw water flow paths is further increased, whereby the cross-sectional area of each raw water flow path is reduced. As a result, the linear velocity of the raw water can be increased, and the progress of the concentration polarization layer can be further suppressed.
Similarly to the first raw water channel 15 and the second raw water channel 16, the third raw water channel 17 extends linearly between the first end surface 10p and the second end surface 10q. With this configuration, the formation of the stagnant area can be prevented more reliably.
When the flow direction of the raw water is reversed by 180 degrees from the first raw water flow path 15 to the second raw water flow path 16. When the flow direction of the raw water is shifted from the second raw water flow path 16 to the third raw water flow path 17, the flow direction of the raw water is reversed by 180 degrees. Such a flow of raw water can be applied to other modifications and other embodiments.
In the present modification, the first raw water flow path 15 occupies a region of the first angle θ 1 in the circumferential direction of the water collection pipe 21. The second raw water flow path 16 occupies a region of a second angle θ 2 in the circumferential direction of the water collection pipe 21. The third raw water flow path 17 occupies a region of a third angle θ 3 in the circumferential direction of the header pipe 21. The first angle θ 1 is greater than the second angle θ 2. The second angle θ 2 is larger than the third angle θ 3. With this configuration, a decrease in the linear velocity of the raw water can be sufficiently prevented. For example, the first angle θ 1 is 160 degrees, the second angle θ 2 is 120 degrees, and the third angle θ 3 is 80 degrees.
The second raw water flow path 16 has a smaller flow path cross-sectional area than the first raw water flow path 15. The third raw water flow path 17 has a flow path cross-sectional area smaller than that of the second raw water flow path 16. In other words, the raw water flow path on the downstream side has a smaller flow path cross-sectional area than the raw water flow path on the upstream side. With this configuration, the linear velocity of the raw water is less likely to decrease in the second raw water channel 16 and the third raw water channel 17. Therefore, the separation membrane element 20 is suitable for high recovery rate operation.
The plurality of partitions 23 partition the first raw water flow path 15, the second raw water flow path 16, and the third raw water flow path 17 from each other. Thus, the raw water flows through the first raw water flow path 15, the second raw water flow path 16, and the third raw water flow path 17 in this order without a short cut.
The configuration described with reference to fig. 4A is also applicable to this modification. Specifically, the plurality of partitions 23 include a plurality of first partitions arranged in a radial direction of the water collection pipe 21 at a first angular position, a plurality of second partitions arranged in the radial direction of the water collection pipe 21 at a second angular position, and a plurality of third partitions arranged in the radial direction of the water collection pipe 21 at a third angular position. The first, second, and third angular positions are predetermined angular positions in the circumferential direction of the header pipe 21. With this configuration, the first raw water flow path 15, the second raw water flow path 16, and the third raw water flow path 17 can be reliably separated from each other.
The separation membrane element 20 further includes a communication channel 31 and a communication channel 32. The communication flow path 31 connects the outlet of the first raw water flow path 15 at the second end face 10q and the inlet of the second raw water flow path 16 at the second end face 10q. The communication passage 31 is isolated from the third raw water passage 17. The communication flow path 32 connects the outlet of the second raw water flow path 16 in the first end surface 10p and the inlet of the third raw water flow path 17 in the first end surface 10p. The communication flow path 32 is isolated from the first raw water flow path 15. The communication passage 31 can transfer raw water from the first raw water passage 15 to the second raw water passage 16. The communication passage 32 can transfer raw water from the second raw water passage 16 to the third raw water passage 17.
In the present modification, communication flow path 31 may be an internal space of cover 281 covering second end face 10q. The communication flow path 32 may be an internal space of the cover 282 covering the first end surface 10p. As shown in fig. 8B, cover 281 covers second end face 10q to form an isolation chamber serving as communication flow path 31. The cover 281 isolates the outlet of the first raw water flow path 15 and the inlet of the second raw water flow path 16 from the outlet of the third raw water flow path 17. As shown in fig. 8C, the cover 282 covers the first end surface 10p to form an isolation chamber as the communication flow path 32. The cover 282 separates the outlet of the second raw water flow path 16 and the inlet of the third raw water flow path 17 from the inlet of the first raw water flow path 15. With this configuration, the raw water flows through the first raw water flow path 15, the second raw water flow path 16, and the third raw water flow path 17 in this order. The stagnation region SA described with reference to fig. 24 can be prevented from being formed. It is also possible to prevent the raw water from flowing from the first raw water flow path 15 to the third raw water flow path 17 without flowing through the second raw water flow path 16, or to prevent the raw water from returning from the third raw water flow path 17 to the first raw water flow path 15. The covers 281 and 282 are attached to the laminate 22, for example.
(modification 2)
Fig. 9A schematically shows the structure of a separation membrane element 30 according to modification 2. Fig. 9B is a schematic plan view of the separation membrane element 30 when viewed from the first end face 10p or the second end face 10q. All the descriptions relating to the separation membrane elements 10 and 20 can be applied to the separation membrane element 30 as long as they are technically not contradictory.
As shown in fig. 9A and 9B, the separation membrane element 30 includes a fourth raw water channel 18 extending from the second end face 10q to the first end face 10p in addition to the structure of the separation membrane element 20. As shown by arrows, in the separation membrane element 30, raw water flows into the first raw water channel 15 through the first end face 10p, and flows out of the first raw water channel 15 through the second end face 10q. Then, the raw water flows into the second raw water flow path 16 through the second end surface 10q, and flows out of the second raw water flow path 16 through the first end surface 10p. Then, the raw water flows into the third raw water flow path 17 through the first end surface 10p, and flows out of the third raw water flow path 17 through the second end surface 10q. The raw water flows into the fourth raw water flow path 18 through the second end surface 10q, and flows out of the fourth raw water flow path 18 through the first end surface 10p. In other words, the raw water reciprocates 2 times between the first end face 10p and the second end face 10q. According to this modification, the total length of the raw water flow paths is further increased, thereby reducing the cross-sectional area of each raw water flow path. As a result, the linear velocity of the raw water can be increased, and the progress of the concentration polarization layer can be further suppressed.
Like the first raw water channel 15, the second raw water channel 16, and the third raw water channel 17, the fourth raw water channel 18 also extends linearly between the first end surface 10p and the second end surface 10q. With this configuration, the formation of the stagnant area can be more reliably prevented.
In the present modification, the first raw water flow path 15 occupies a region of the first angle θ 1 in the circumferential direction of the water collection pipe 21. The second raw water flow path 16 occupies a region of a second angle θ 2 in the circumferential direction of the water collection pipe 21. The third raw water flow path 17 occupies a region of a third angle θ 3 in the circumferential direction of the header pipe 21. The fourth raw water flow path 18 occupies a region of a fourth angle θ 4 in the circumferential direction of the water collection pipe 21. The first angle θ 1 is greater than the second angle θ 2. The second angle θ 2 is larger than the third angle θ 3. The third angle θ 3 is larger than the fourth angle θ 4. With this configuration, a decrease in the linear velocity of the raw water can be sufficiently prevented. For example, the first angle θ 1 is 120 degrees, the second angle θ 2 is 100 degrees, the third angle θ 3 is 80 degrees, and the fourth angle θ 4 is 60 degrees.
The second raw water flow path 16 has a smaller flow path cross-sectional area than the first raw water flow path 15. The third raw water flow path 17 has a flow path cross-sectional area smaller than that of the second raw water flow path 16. The fourth raw water flow path 18 has a flow path cross-sectional area smaller than that of the third raw water flow path 17. With this configuration, the linear velocity of the raw water is less likely to decrease in the second raw water flow path 16, the third raw water flow path 17, and the fourth raw water flow path 18. Therefore, the separation membrane element 30 is suitable for high recovery rate operation.
The plurality of partitions 23 partition the first raw water flow path 15, the second raw water flow path 16, the third raw water flow path 17, and the fourth raw water flow path 18 from each other. Thus, the raw water flows through the first raw water flow path 15, the second raw water flow path 16, the third raw water flow path 17, and the fourth raw water flow path 18 in this order, and does not have a short path.
As can be understood from modification 1 and modification 2, the number of raw water flow paths is not limited to 2, and may be 3 or more. As the number of raw water flow paths increases, the flow path cross-sectional area of each raw water flow path decreases, and the linear velocity of raw water increases. The number of raw water flow paths and the angle of the area occupied by each raw water flow path are determined in consideration of the reduction in membrane area of the separator 23, ease of manufacture, and the like.
As can be understood from this modification, the separation membrane element of the present embodiment may further include at least one additional raw water channel extending linearly from the first end face 10p to the second end face 10q in addition to the first raw water channel 15 and the second raw water channel 16. At least one additional raw water flow path corresponds to the third raw water flow path 17 and the fourth raw water flow path 18 in the present modification. The raw water flows out from the additional raw water flow path through the first end face 10p or the second end face 10q. Thereafter, the raw water passes through the first end surface 10p or the second end surface 10q passing through the additional raw water flow path again and flows into another additional raw water flow path located on the downstream side of the additional raw water flow path. The additional raw water flow paths may be adjacent to each other or may be separated from each other.
For example, when the separation membrane element includes n (n is an integer of 2 or more) raw water flow paths, raw water passes through the first end face 10p or the second end face 10q and flows out of the kth (k is an arbitrary integer of 1 or more and n-1 or less) raw water flow path. Thereafter, the raw water passes through the first end surface 10p or the second end surface 10q passing through when flowing out from the kth raw water flow path again, and flows into the (k + 1) th raw water flow path located on the downstream side of the kth raw water flow path.
Next, the position of the partition 23 of the raw water spacer 13 will be described.
The separation membrane elements 10, 20, and 30 include, for example, 4 membrane leaves 11 (see fig. 3) wound around a water collection pipe 21 and 4 raw water spacers 13. Each membrane leaf 11 is constituted by, for example, 1 pair of separation membranes 12 and a permeated water spacer 14. When the membrane leaves 11 and the raw water spacer 13 are wound around the water collecting pipe 21, the interval between the spacers 23 in the 4 raw water spacers 13 is not equal because the radius of the work (the separation membrane element during assembly) gradually increases. The number of the membrane leaves 11 and the raw water spacer 13 may be 4 or more.
Fig. 10 shows a separation membrane element 20 of modification 1 in which 4 raw water spacers 13 are expanded when the separation membrane element is composed of 4 membrane leaves 11 and 4 raw water spacers 13. The position of the longitudinal line indicates the position of the partition 23. The left side of fig. 10 is a side close to the water collecting pipe 21, and the partitions 23 are densely arranged. The end portions of the raw water spacer 13 are preferably arranged at equal intervals of substantially 90 degrees around the water collecting pipe 21. When 4 membrane leaves 11 and raw water spacers 13 are arranged at 90-degree intervals, the outer shape of the separation membrane element 20 is more circular, and the eccentricity of the outer diameter with respect to the center of the water collection pipe 21 can be minimized. The term "eccentricity of the outer diameter" refers to the amount of deviation between the center of the circle circumscribing the separation membrane element 20 and the center of the header pipe 21.
The position of the separator 23 can be determined by using the equation r = r in polar coordinates, for example 0 +bθ(r 0 : radius of the header pipe 21, b: constant) is determined. As shown in FIG. 11, the curve is a spiral with radii that increase at equal intervals for each turn, also known as aA basal-mede helix. The position of the separator 23 in the raw water spacer 13 in the expanded state can be determined by calculating the arc length of the spiral up to the position of the separator 23 in the state where the membrane leaves 11 and the raw water spacer 13 are wound around the water collecting pipe 21. The arc length up to a certain winding angle θ (unit: radian) can be determined by integrating the arc length r · Δ θ (product of r and Δ θ) of the minute angle Δ θ up to the winding angle θ. The constant b is represented by b = w/(2 pi). The constant b is determined so that the sum of the thicknesses of the sheet-like members coincides with the radius increase length w per turn. In the example of fig. 10, the total thickness of the sheet-like member is the total thickness of 4 membrane leaves 11 and the total thickness of 4 raw water spacers 13.
Several other embodiments will be described below. The same reference numerals are given to elements common to the respective embodiments, and descriptions thereof may be omitted. The descriptions related to the respective embodiments may be applied to each other as long as the technical contradiction is not present. The embodiments can also be combined with one another, as long as they are not technically contradictory.
(embodiment mode 2)
Fig. 12A is a plan view of the separation membrane element 40 according to embodiment 2 as viewed from the first end face 10p or the second end face 10q. Fig. 12A omits the raw water spacer and the permeated water spacer, and only the folded separation membrane 12 is shown. The separation membrane element 40 has a folded configuration. Specifically, the separation membrane 12 is folded and wound around the water collection pipe 21. In the present embodiment, a plurality of folded separation membranes 12 are used, and are wound around the water collecting pipe 21. The separation membrane element 40 of the present embodiment also achieves the same effects as the separation membrane elements (10, 20, 30) of embodiment 1.
A separator 236 is provided between the separation membrane 12 and the separation membrane 12. The separation membrane element 40 includes a plurality of separators 236. The first raw water flow path 15 and the second raw water flow path 16 are partitioned by the partition 236. The plurality of spacers 236 extend in both the radial direction of the header pipe 21 and the longitudinal direction of the header pipe 21. With this configuration, the first raw water flow path 15 and the second raw water flow path 16 can be reliably separated. The separator 236 is a member different from the raw water separator 13, and may be a member made of a material having water-blocking properties. In this case, the raw water can be more reliably prevented from flowing from the first raw water flow path 15 to the second raw water flow path 16 in a short path.
Fig. 12B shows the separation membrane 12 used in the separation membrane element 40 in an expanded state. Fig. 12C is an exploded cross-sectional view of the separation membrane element 40, and shows the positional relationship of the separation membrane 12, the raw water spacer 13, the permeated water spacer 14, and the separator 236. As shown in fig. 12B, a sealing resin 29 is provided on the surface on the transmission side of the separation membrane 12. The sealing resin 29 is provided along the outer periphery of the separation membrane 12 so as to surround the space on the transmission side of the separation membrane 12. The space on the permeation side of the separation membrane 12 is sealed with a sealing resin 29 and functions as a permeate flow path. The permeated water flow path communicates with the through hole 21h (see fig. 3) of the water collection pipe 21.
The position P1 shown by the solid line indicates the position of the convex folding portion. A position P2 indicated by a one-dot chain line indicates a position of the concave folding portion. As shown in fig. 12C, the separation membranes 12 alternately sandwich the raw water spacers 13 and the permeated water spacers 14 and are folded in a zigzag shape at the positions P1 and P2. The separator 236 is bonded to the end of the separation membrane 12.
The raw water flows linearly in a direction parallel to the folds of the separation membrane 12. The permeated water flows in a spiral shape in a direction perpendicular to the fold of the separation membrane 12.
The separation membrane 12, the raw water spacer 13, the permeated water spacer 14, and the separator 236 are wound around the water collection pipe 21. The curvature of the separation membrane 12 differs before and after the fold, and thus the appropriate folding width differs before and after the fold. If the folding width is changed before and after the fold line in consideration of the difference in curvature, it is possible to avoid a problem such as wrinkles occurring in the separation membrane 12 when the separation membrane is wound around the water collecting pipe 21.
The partition 236 may be composed of a film capable of blocking water. Examples of the material of the thin film include resin, metal, and ceramic. In the case where the separator 236 is made of a material having flexibility, the separator 236 can be deformed together with the separation membrane 12 when wound around the water collection pipe 21. For example, the separator 236 may be made of a soft resin sheet such as polyvinyl chloride.
In the separation membrane element 40 of the present embodiment, the length of the permeate flow path in the circumferential direction is equal to the distance from the position P1 to the position P2. In other words, the permeate flow path of the separation membrane element 40 is shorter than the permeate flow path of the spiral separation membrane element, and therefore the flow resistance in the permeate flow path of the separation membrane element 40 is small. Therefore, even when the permeate spacer 14 thinner than the element used in the spiral separation membrane element is used in the separation membrane element 40 to increase the flow resistance, this can be tolerated. The separation membrane element 40 can use a thin permeable water spacer 14. By using a thin permeated water spacer 14, the membrane area of the separation membrane element 40 can be increased. The thickness of the water-permeable spacer 14 is not particularly limited, and may be 5 mils (mil) or less, or 1 to 5 mils. When the support of the separation membrane 12 has a function of flowing the permeated water to some extent, the permeated water spacer 14 may be omitted.
(embodiment mode 3)
Fig. 13A is a schematic perspective view of a separation membrane element 50 according to embodiment 3. Fig. 13B shows a cross section of the separation membrane element 50 shown in fig. 13A.
The separation membrane element 50 of the present embodiment includes a plurality of stacked flat plate-shaped separation membranes 12. The first end face 10p and the second end face 10q are end faces of the plurality of laminated separation membranes 12 that face each other, and are end faces of the separation membrane element 50. The separation membrane element 50 of the present embodiment also achieves the same effects as the separation membrane elements 10, 20, 30, and 40 of embodiments 1 and 2.
Specifically, the separation membrane element 50 includes a plurality of stacked flat plate-shaped blocks 71. Each block 71 is composed of a separation membrane 12, a raw water spacer 13, and a permeated water spacer 14. The folded separation membrane 12 is used for each block 71. The raw water spacers 13 and the permeated water spacers 14 are alternately arranged between the pleats of the separation membrane 12. One block 71 selected from the plurality of blocks 71 has a first raw water flow path 15. The other blocks 71 selected from the plurality of blocks 71 have the second raw water flow path 16. Still another block 71 selected from the plurality of blocks 71 has a third raw water flow path 17. In the present embodiment, the block 71 having the first raw water flow path 15, the block 71 having the second raw water flow path 16, and the block 71 having the third raw water flow path 17 are sequentially stacked. In the present embodiment, the raw water flow paths 15, 16, and 17 also extend linearly between the first end surface 10p and the second end surface 10q.
As indicated by arrows, in the separation membrane element 50, the raw water also reciprocates between the first end face 10p and the second end face 10q. Specifically, the raw water flows into the first raw water channel 15 through the first end face 10p, and flows out of the first raw water channel 15 through the second end face 10q. Thereafter, the raw water flows into the second raw water flow path 16 through the second end surface 10q, and flows out of the second raw water flow path 16 through the first end surface 10p. The raw water flows into the third raw water flow path 17 through the first end surface 10p, and flows out of the third raw water flow path 17 through the second end surface 10q.
The separation membrane element 50 has a rectangular shape in plan view, for example. The raw water flows in each raw water flow path from the first end face 10p toward the second end face 10q or from the second end face 10q toward the first end face 10p. The permeated water is guided in a direction perpendicular to the flow direction of the raw water and the stacking direction of the blocks 71.
The separation membrane element 50 includes a plurality of plate-like separators 237. The partition 237 partitions the first raw water flow path 15 and the second raw water flow path 16. The other partition 237 partitions the second raw water flow path 16 and the third raw water flow path 17. Each separator 237 is disposed between the separation membrane 12 and the separation membrane 12. Specifically, each of the spacers 237 is disposed between the blocks 71 and 71. With this configuration, the first raw water flow path 15 and the second raw water flow path 16 can be reliably separated. The second raw water flow path 16 and the third raw water flow path 17 can be reliably separated. The separator 237 is a member different from the raw water spacer 13, and may be a member made of a material having water-blocking properties. In this case, the raw water can be more reliably prevented from flowing from the first raw water flow path 15 to the second raw water flow path 16 in a short path. It is possible to more reliably prevent the raw water from flowing from the second raw water flow path 16 to the third raw water flow path 17 in a short path. The partition 237 may be formed of a water-blocking film, a water-blocking plate, or the like. Examples of the material of the film and the plate include resin, metal, and ceramics.
The raw water spacer 13 is disposed on the separation function layer side of the separation membrane 12. The water-permeable spacer 14 is disposed on the support side of the separation membrane 12. A sealing resin 29 is provided on the surface of the permeation side of the separation membrane 12. The sealing resin 29 is provided along the outer periphery of the separation membrane 12 so as to surround the space on the transmission side of the separation membrane 12. The space on the permeation side of the separation membrane 12 is sealed with a sealing resin 29 and functions as a permeate flow path.
The block 71 can be produced by the same method as the production method of the separation membrane element 40 described with reference to fig. 12B and 12C.
As described with reference to fig. 12B and 12C, the sealing resin 29 is provided along the outer periphery of the separation membrane 12 so as to surround the space on the transmission side of the separation membrane 12. The space on the permeation side of the separation membrane 12 is surrounded by the sealing resin 29 and functions as a permeate flow path. When the separation membrane 12 is folded, the sealing resin 29 is present on the 3-side of the block 71, and the sealing resin 29 is not present on the 1-side of the block 71. The permeated water flows out from the side 1 where the sealing resin 29 does not exist.
The position P1 shown by the solid line indicates the position of the convex folding portion. A position P2 indicated by a one-dot chain line indicates a position of the concave folding portion. As shown in fig. 12C, the separation membranes 12 alternately sandwich the raw water spacers 13 and the permeated water spacers 14 and are folded in a zigzag shape at the positions P1 and P2. Instead of the separator 236, a separator 237 is bonded to an end of the separation membrane 12.
As shown in fig. 13A, the communication flow path 31 connects the outlet of the first raw water flow path 15 at the second end face 10q and the inlet of the second raw water flow path 16 at the second end face 10q. The communication flow path 31 is isolated from the third raw water flow path 17. The communication flow path 32 connects the outlet of the second raw water flow path 16 in the first end surface 10p and the inlet of the third raw water flow path 17 in the first end surface 10p. The communication flow path 32 is isolated from the first raw water flow path 15. The communication flow path 31 can smoothly transfer raw water from the first raw water flow path 15 to the second raw water flow path 16. The communication flow path 32 can smoothly transfer the raw water from the second raw water flow path 16 to the third raw water flow path 17.
Communication flow channel 31 may be an internal space of cover 285 covering second end face 10q. Cover 285 covers second end face 10q and forms an isolation chamber serving as communication channel 31. The communication flow path 32 may be an internal space of the cover 286 covering the first end surface 10p. The cover 286 covers the first end surface 10p to form an isolation chamber as the communication flow path 32. With this configuration, the raw water can be smoothly transferred from the first raw water flow path 15 to the second raw water flow path 16, and the raw water can be smoothly transferred from the second raw water flow path 16 to the third raw water flow path 17. The stagnation region SA described with reference to fig. 24 can be prevented from being formed. Cover 285 and/or cover 286 may be a part of the entire housing that houses separation membrane element 50.
The separation membrane element 50 further includes a collection channel 33 provided to collect the permeated water. The collected flow path 33 is a flow path for collecting the permeated water through the third end surface 10 r. The third end surface 10r is one end surface selected from the other pair of end surfaces facing each other of the plurality of laminated separation membranes 12. With such a configuration, it is possible to avoid mixing of the raw water and the permeated water, and to guide the permeated water to the outside of the separation membrane element 50.
Specifically, the collecting channel 33 may be an internal space of the cover 287 covering the third end surface 10 r. The cover 287 covers the third end surface 10r and forms an isolation chamber as the collective channel 33. A flow outlet 289 is provided in the cover 287. The permeated water is guided to the outside of the separation membrane element 50 through the flow outlet 289.
The number of blocks 71 may also be 2. In this case, the 1-component separator 237 and the block 71 are omitted, and the third raw water flow path 17 is omitted. The separation membrane element 50 includes a first raw water channel 15 and a second raw water channel 16. The separation membrane element 50 may be provided with only one separator 237.
The block 71 may also have a plurality of separation membranes 12. The block 71 may have a plurality of raw water spacers 13. The block 71 may also have a plurality of permeable water spacers 14.
In the present embodiment, the first raw water channel 15 has a channel cross-sectional area equal to that of the second raw water channel 16 and equal to that of the third raw water channel 17. In other words, a plurality of blocks 71 having the same configuration are used. Therefore, the mass production effect is good, and the production cost of the separation membrane element 50 can be suppressed. Of course, the second raw water flow path 16 may have a flow path cross-sectional area smaller than that of the first raw water flow path 15. The third raw water channel 17 may have a smaller channel cross-sectional area than the second raw water channel 16. With such a configuration, the linear velocity of the raw water is less likely to decrease, and therefore a laminated separation membrane element suitable for high recovery rate operation can be provided.
Since the permeate flow path of the separation membrane element 50 of the present embodiment is shorter than that of the spiral separation membrane element, the flow resistance in the permeate flow path of the separation membrane element 50 is small. Therefore, even when the permeate spacer 14 thinner than the element used in the spiral separation membrane element is used in the separation membrane element 50 to increase the flow resistance, this can be tolerated. By using a thin permeated water spacer 14, the membrane area of the separation membrane element 50 can be increased. The thickness of the water-permeable spacer 14 is not particularly limited, and may be 5 mils (mil) or less, or 1 to 5 mils. When the support of the separation membrane 12 has a function of flowing the permeated water to some extent, the permeated water spacer 14 may be omitted.
For example, a porous structure may be provided to the support of the separation membrane 12, or a substitute function of the permeated water spacer 14 may be provided to the support of the separation membrane 12 to some extent by providing fine irregularities on the surface of the support of the separation membrane 12. In this case, the separation membrane element 50 can be configured without the water-permeable spacer 14. Since the permeated water flow path of the separation membrane element 50 is short, even if the flow resistance of the permeated water flow path is relatively large, the pressure loss of the permeated water does not become excessively large, and the effective pressure at the time of use of the separation membrane element 50 is not largely affected. When the permeated water flow path is short, not only the flow path itself is short, but also the amount of permeated water that permeates through the separation membrane 12 and flows into the permeated water flow path is small. These effects complement each other, and the pressure loss (flow loss) of the permeated water in the permeated water flow path is reduced.
(embodiment mode 4)
Fig. 14A is a schematic plan view of the separation membrane element 60 according to embodiment 4 when viewed from the first end face 10p or the second end face 10q. As shown in fig. 14A, the separation membrane element 60 of the present embodiment includes a plurality of dividing elements 81 arranged in the circumferential direction of the water collecting duct 21. The sectioning element 81 has a cross-sectional shape of a partial circular ring. "partial ring" refers to a shape obtained by cutting off a part of a ring within a specific angle range. Each of the plurality of dividing elements 81 is an independent compartment. The separation membrane element 60 as a whole has a cylindrical shape.
Each of the dividing elements 81 forms the first raw water flow path 15, the second raw water flow path 16, or the third raw water flow path 17. In the present embodiment, the 4 dividing elements 81 form the first raw water channel 15,3, the 4 dividing elements 81 form the second raw water channel 16,2, and the third raw water channel 17 is formed. Therefore, the first raw water flow path 15 has a larger flow path cross-sectional area than the second raw water flow path 16. The second raw water flow path 16 has a flow path cross-sectional area larger than that of the third raw water flow path 17. Since the flow path cross-sectional area of the raw water flow path decreases as the flow path proceeds downstream, the flow velocity of the raw water in the raw water flow path can be maintained high even when the high recovery rate operation is performed.
Fig. 14B shows a cross section of the dividing element 81 used in the separation membrane element 60 shown in fig. 14A. The cross section is a cross section perpendicular to the longitudinal direction of the header pipe 21. Each of the plurality of dividing elements 81 includes an outer wall 83 and a separation membrane 12 disposed inside the outer wall 83. The flow of raw water along the circumferential direction of the water collecting pipe 21 is blocked by the outer wall portions 83 of the plurality of dividing elements 81. With this configuration, the first raw water flow path 15 and the second raw water flow path 16 can be reliably separated. The second raw water flow path 16 and the third raw water flow path 17 can be reliably separated. The dividing elements 81 are independent of each other, and therefore, the raw water can be reliably prevented from flowing from the first raw water flow path 15 to the second raw water flow path 16 in a short path. It is possible to reliably prevent the raw water from flowing from the second raw water flow path 16 to the third raw water flow path 17 in a short path.
According to the present embodiment, the flow path cross-sectional area of each raw water flow path can be adjusted by using the divided element 81 which is formed into small segments as a unit structure of the flow path. In other words, the dividing element 81 can control the flow of raw water as one unit.
The dividing element 81 further includes a plurality of raw water spacers 13 and permeable water spacers 14. In the dividing element 81, the separation membrane 12 is folded and disposed inside the outer wall portion 83. The outer wall 83 is provided with a through hole 83h communicating with the through hole 21h of the water collection pipe 21. The outer wall portion 83 has, for example, a cylindrical shape with both ends open. The raw water spacers 13 and the permeated water spacers 14 are alternately arranged between the pleats of the separation membrane 12. The plurality of raw water spacers 13 may be connected to form one. The water permeable spacer 14 may also be divided into a plurality of sections.
As a material of the outer wall portion 83, a resin sheet made of a thermoplastic resin such as polyethylene terephthalate or polyvinyl chloride can be used. The cylindrical outer wall 83 may be formed by bending a resin sheet, or the outer wall 83 may be formed by combining a plurality of members. The separation membrane 12, the raw water spacer 13, and the permeated water spacer 14 are disposed inside the cylindrical outer wall portion 83.
According to the present embodiment, the permeated water flow path is very short. Therefore, the dividing element 81 can use a thin permeable spacer 14. By using a thin permeable water spacer 14, the membrane area of the separation membrane element 60 can be increased. The thickness of the water-permeable spacer 14 is not particularly limited, and may be 5 mils (mil) or less, or 1 to 5 mils. When the support of the separation membrane 12 has a function of flowing the permeated water to some extent, the permeated water spacer 14 may be omitted.
Fig. 14C shows the separation membrane 12 used for the sectioning element 81 in an expanded state. Fig. 14D shows the positional relationship among the separation membrane 12, the raw water spacer 13, the permeated water spacer 14, and the spacer outer wall 83 of the partitioning member 81.
As shown in fig. 14C, a sealing resin 29 is provided on the surface on the transmission side of the separation membrane 12. The sealing resin 29 is provided along the outer peripheral portion of the separation membrane 12 so as to form a space on the permeation side when the separation membrane 12 is folded and bonded. The space on the permeation side of the separation membrane 12 functions as a permeated water flow path isolated from the raw water flow path by the sealing resin 29. The gap between the support of the separation membrane 12 and the inner surface of the outer wall 83 is sealed in a watertight manner by the sealing resin 29. The permeate flow path communicates with the through hole 21h of the water collection pipe 21.
The position P1 shown by the solid line indicates the position of the convex folding portion. A position P2 indicated by a one-dot chain line indicates a position of the concave folding portion. As shown in fig. 14C, the separation membranes 12 alternately sandwich the raw water spacers 13 and the permeated water spacers 14 and are folded in a zigzag shape at the positions P1 and P2.
The raw water flows linearly in a direction parallel to the folds of the separation membrane 12. The permeated water flows in a direction perpendicular to the fold of the separation membrane 12.
Since the dividing element 81 has a sectional shape of a partial circular ring, the separation membrane 12 has a suitable folding width that varies depending on the location so that the inside of the partial circular ring is filled with the separation membrane 12, the raw water spacer 13, and the permeated water spacer 14 without a gap. By changing the folded width of the separation membrane 12 so as to prevent a large gap from being generated inside the outer wall portion 83, it is difficult to generate a gap inside. This allows the raw water to uniformly flow through the entire raw water flow path. The partitioning member 81 can also be used by folding the membrane leaf 11 of the spiral membrane element.
As shown in fig. 14D, the outer wall portion 83 is composed of, for example, 4 portions 83a, 83b, and 83 c. The sealing resin 29 (see fig. 14C) seals the supports of the folded separation membranes 12 and the space between the support of the separation membrane 12 and the outer wall 83. Thus, in the dividing element 81, the raw water flow path and the permeate flow path are isolated from each other.
Fig. 14E shows a vertical cross section of the separation membrane element 60 at a position including the permeated water channel. In fig. 14E, arrows indicate the flow of permeated water. Fig. 14F shows a vertical cross section of the separation membrane element 60 at a position including the raw water channel. In fig. 14F, arrows indicate the flow of raw water. In fig. 14E and 14F, the covers 281 and 282 described in the previous embodiments are omitted.
As shown in fig. 14E, the plurality of dividing elements 81 are disposed around the water collecting pipe 21 so that the permeate flow paths thereof communicate with the through-holes 21h of the water collecting pipe 21. A connection flow path 36 closed by a sealing resin 34 is provided between the dividing element 81 and the water collecting pipe 21. The connection passage 36 may be formed by winding a porous body such as a tricot knitted fabric or a mesh around the water collection pipe 21 for 1 or more circles. For example, the permeated water spacer 14 is wound around the header pipe 21 to form the connection channel 36. In other words, the connection flow path 36 surrounds the header 21 over 360 °. Therefore, the through-holes 21h of the header pipe 21 and the through-holes 83h of the dividing element 81 do not need to be aligned, and the number of the through-holes 21h of the header pipe 21 can be reduced. The movement of the connecting channel 36 smoothly guides the permeated water from the through-hole 83h provided in the outer wall portion 83 of the dividing element 81 to the through-hole 21h of the water collecting pipe 21.
The permeated water flow path of the dividing element 81 is closed by the sealing resin 29 disposed at positions corresponding to the inlet and outlet of the raw water flow path. The end of the separation membrane 12 is bonded to the outer wall 83 in the direction perpendicular to the longitudinal direction of the water collection pipe 21. Specifically, the top of the fold (the top on the lower side in the figure) of the concave folding portion of the separation membrane 12 shown in fig. 14D is bonded to the outer wall portion 83. Thus, in the dividing element 81, the raw water flow path and the permeate flow path are isolated from each other.
As shown in fig. 14F, both ends of the first raw water flow path 15 are open in the longitudinal direction of the water collection pipe 21.
Fig. 15A, 15B, and 15C show cross sections of the dividing elements 85, 87, and 89 according to the modified examples. As can be understood from these modifications, the arrangement and shape of the separation membrane 12, the raw water spacer 13, and the permeated water spacer 14 are not particularly limited.
In the dividing member 85 shown in fig. 15A, the separation membrane 12 is folded. The water-permeable spacers 14 have the shape of branches of trees. In other words, the permeated water flow path has the shape of a branch of a tree.
The dividing element 87 shown in fig. 15B is provided with the separation membrane 12 folded. The separation membrane 12 is folded so as to sandwich the water-permeable spacer 14, and forms a membrane leaf 11 together with the water-permeable spacer. The membrane leaf 11 comprising the separation membrane 12 and the permeate spacer 14 is folded in a zigzag shape. A raw water spacer 13 is disposed outside the folded membrane leaves 11 so as to be positioned between the separation membranes 12 and 12.
In the partitioning member 89 shown in fig. 15C, the separation membrane 12 is folded so as to sandwich the permeable water spacer 14, and forms the membrane leaf 11 together with the permeable water spacer. The membrane leaf 11 is wound in a spiral shape and disposed inside the outer wall portion 83. The raw water spacer 13 is disposed outside the membrane leaves 11 wound in a spiral shape so as to be positioned between the separation membrane 12 and the separation membrane 12. The separation membrane 12 is located between the raw water spacer 13 and the permeated water spacer 14. In this modification, a single raw water spacer 13 is used.
In a conventional spiral separation membrane element, a separation membrane wound around a water collecting pipe has a length of about 1m in a double-folded state and is long. Therefore, the manufacturing equipment of the separation membrane element also necessarily requires a large floor area.
In contrast, in the separation membrane element 60 of the present embodiment, the separation membrane 12 is not wound around the water collection pipe 21. The manufacturing process of the dividing element 81 can be performed independently of the process for attaching the dividing element 81 to the header pipe 21. Therefore, the separation membrane element 60 brings about a significant reduction in floor area of the manufacturing facility. In addition, a desired sealing portion can be formed by a process such as a thermal welding method.
The separation membrane element 60 of the present embodiment can also be used in the same manner as a conventional spiral separation membrane element. In other words, the raw water may be treated by flowing the raw water only in one direction of the separation membrane element 60.
A conventional spiral separation membrane element includes a plurality of membrane leaves wound around a water collection pipe and a plurality of raw water spacers. Each membrane leaf is composed of, for example, 1 pair of separation membranes and a water-permeable spacer. In the production of a conventional spiral separation membrane element, a separation membrane is coated with an adhesive to form a membrane leaf. The timing of curing the adhesive is adjusted to end after the membrane leaves and the raw water spacer are wound around the water collecting pipe. In other words, an adhesive that takes time until curing has to be used, and the time taken for production tends to be long.
In order to eliminate the troublesome manufacturing, a new configuration of separation membrane element is desired. However, a large change in the shape of the separation membrane element is not often adopted because it requires a change in the existing water treatment facilities or increases the installation space. Therefore, a new separation membrane element that can have the same size and the same shape as those of the spiral separation membrane element is desired.
The separation membrane element 60 of the present embodiment can meet the above-described requirements. The separation membrane element 60 of the present embodiment includes a water collection pipe 21 and a plurality of dividing elements 81 arranged in the circumferential direction of the water collection pipe 21. The plurality of dividing elements 81 include at least one dividing element 81 forming the first raw water flow path 15 extending in parallel to the longitudinal direction of the water collecting pipe 21 and at least one dividing element 81 forming the second raw water flow path 16. Each of the plurality of dividing elements 81 includes an outer wall 83 and a separation membrane 12 disposed inside the outer wall 83. The flow of raw water along the circumferential direction of the water collecting pipe 21 is blocked by the outer wall portion 83 of the dividing element 81. The separation membrane element 60 of the present embodiment is not only suitable for high recovery rate operation, but also can satisfy the above-described requirements. For example, the separation membrane module may be configured by placing the separation membrane element 60 of the present embodiment in an existing pressure vessel.
(purification of tap Water Using separation Membrane element)
For example, the separation membrane element 10 can be used to purify tap water. Tap water is caused to flow into the first raw water flow path 15 through the first end surface 10p. Tap water is discharged from the first raw water channel 15 through the second end surface 10q. The flow direction of the tap water is reversed by 180 degrees, and the tap water discharged from the first raw water flow path 15 through the second end face 10q flows into the second raw water flow path 16. Tap water is discharged from the second raw water flow path 16 through the first end surface 10p. The permeated water is highly purified water, and has high added value. For example, even in countries and regions where tap water is not suitable for drinking, drinking water can be produced from tap water by treatment with the separation membrane element 10. When the high recovery rate operation is performed, the amount of tap water concentrated and discharged to be discarded is also small, and it is economical.
When the separation membrane element 10 is a reverse osmosis membrane element or a nanofiltration membrane element, it is possible to greatly remove harmful substances at an atomic level such as arsenic and heavy metals from tap water. As a result, safer drinking water is obtained. There is also an advantage in that soft water can be produced from hard water.
In the case of using the separation membrane element 20, tap water is caused to flow out of the second raw water flow path 16 through the first end face 10p, the flow direction of the tap water is reversed again by 180 degrees, and the tap water discharged from the second raw water flow path 16 through the first end face 10p is caused to flow into the third raw water flow path 17. Tap water is discharged from the third raw water flow path 17 through the second end face 10q. The permeate is suitable for use as drinking water. When the operation is performed at a high recovery rate, the amount of the concentrate is small, and it is economical.
The separation membrane element of the present invention can realize a compact and high recovery rate, and is therefore particularly suitable for purification of tap water in places where installation space is limited, such as homes.
As described above, according to the separation membrane elements 10 to 60 of the present embodiment, raw water can be treated at a high recovery rate. The "high recovery rate" may be 50% or more, or 60% or more, for example. The upper limit of the recovery rate is not particularly limited. For example, by treating tap water with a high recovery rate using the separation membrane elements 10 to 60, the amount of waste water can be reduced. As a result, water resources can be greatly saved. The "recovery rate" is a ratio of the flow rate of permeated water to the flow rate of raw water. The "flow rate of raw water" is the flow rate of raw water in the inlet of the first raw water flow path 15.
(embodiment of separation Membrane Module)
Fig. 16 shows a cross section of a separation membrane module 100 according to an embodiment of the present invention. The separation membrane module 100 includes a housing 42 and a separation membrane element 10. The separation membrane element 10 is disposed inside the housing 42. The communication flow path 27 is formed through the inner space of the casing 42. With such a configuration, the housing 42 can be easily reused, and the performance of the separation membrane module 100 can be easily restored by merely replacing the separation membrane element 10.
The casing 42 has a raw water inlet 42a, a concentrated water outlet 42b, and a permeated water outlet 42c. The raw water inlet 42a communicates with an inlet of the first raw water channel 15 in the first end surface 10p of the separation membrane element 10. The concentrated water outlet 42b communicates with the outlet of the second raw water channel 16 in the first end surface 10p of the separation membrane element 10. The concentrated water outlet 42b may be communicated with the outlet of the raw water channel on the most downstream side in the separation membrane element 10. The permeated water outlet 42c communicates with the header 21.
Fig. 17A, 17B, 17C, 17D, and 17E show cross sections of separation membrane modules 101, 102, 103, 104, and 105 according to modified examples, respectively. These figures omit the header 21 for ease of understanding. In these figures, arrows indicate the flow of raw water.
The separation membrane module 101 shown in fig. 17A includes the gasket 43 and the adapter 44 in addition to the structure of the separation membrane module 100 described with reference to fig. 16. The packing 43 is disposed between the outer peripheral surface of the separation membrane element 10 and the inner peripheral surface of the housing 42, and prevents mixing of the raw water and the concentrated water. The gasket 43 is also referred to as a brine seal. The adapter 44 connects the outlet of the second raw water flow path 16 and the raw water outlet 42b of the housing 42. The adapter 44 prevents the raw water to be supplied to the first raw water flow path 15 and the raw water discharged from the second raw water flow path 16 from being mixed. The first raw water channel 15 is connected to the second raw water channel 16 via a communication channel 27. The communication flow path 27 is a part of the internal space of the casing 42.
The separation membrane module 102 shown in fig. 17B includes the separation membrane element 20 described with reference to fig. 8A, 8B, and 8C. The raw water inlet 42a is provided in one end surface of the housing 42 in the longitudinal direction (height direction of the cylinder). The raw water outlet 42b is provided on the other end surface of the housing 42 in the longitudinal direction. In the separation membrane element 20, the first raw water flow path 15 and the second raw water flow path 16 are connected by a communication flow path 31 formed inside the cover 281. The second raw water flow path 16 and the third raw water flow path 17 are connected by a communication flow path 32 formed inside the cover 282. The inner space of the housing 42 is divided by the packing 43 into a space communicating with the raw water inlet 42a and a space communicating with the raw water outlet 42 b. The first raw water flow path 15 opens to a space communicating with the raw water inlet 42 a. The third raw water flow path 17 opens to a space communicating with the raw water outlet 42 b.
The separation membrane module 103 shown in fig. 17C includes the separation membrane element 30 described with reference to fig. 9A and 9B. In the separation membrane element 30, the first raw water channel 15 and the second raw water channel 16 are connected by a communication channel 38 formed inside the cover 283. The second raw water flow path 16 and the third raw water flow path 17 are connected by a communication flow path 39 formed inside the cover 284. The third raw water flow path 17 is connected to the fourth raw water flow path 18 through the internal space of the housing 42. The adapter 44 connects the outlet of the fourth raw water flow path 18 and the raw water outlet 42b of the housing 42.
The separation membrane module 104 shown in fig. 17D includes the separation membrane element 70. The separation membrane element 70 has a first raw water channel 15, a second raw water channel 16, a third raw water channel 17, a fourth raw water channel 18, and a fifth raw water channel 19. The first raw water flow path 15 and the second raw water flow path 16 are connected by a communication flow path 51 formed inside the cover 291. The second raw water channel 16 and the third raw water channel 17 are connected by a communication channel 52 formed inside the cover 293. The third raw water flow path 17 and the fourth raw water flow path 18 are connected by a communication flow path 53 formed inside the cover 292. The fourth raw water channel 18 and the fifth raw water channel 19 are connected by a communication channel 54 formed inside the cover 294. The inner space of the housing 42 is divided by the packing 43 into a space communicating with the raw water inlet 42a and a space communicating with the raw water outlet 42 b. The first raw water flow path 15 opens to a space communicating with the raw water inlet 42 a. The fifth raw water flow path 19 opens to a space communicating with the raw water outlet 42 b.
The separation membrane module 105 shown in fig. 17E includes the separation membrane element 80. The separation membrane element 80 has a first raw water channel 15, a second raw water channel 16, a third raw water channel 17, and a fourth raw water channel 18. The first raw water channel 15 and the second raw water channel 16 are connected by a communication channel 55 formed inside the cover 295. The second raw water flow path 16 and the third raw water flow path 17 are connected by a communication flow path 56 formed inside the cover 296. The third raw water channel 17 and the fourth raw water channel 18 are connected by a communication channel 57 formed inside the cover 297. The communication passages 55 and 57 connect the raw water passages that are not adjacent to each other. The adapter 44 connects the outlet of the fourth raw water flow path 18 and the raw water outlet 42b of the housing 42.
The separation membrane module described with reference to fig. 17A to 17E has the following configuration. When the number n of the raw water flow paths (n is an integer of 2 or more) is even, the raw water inlet 42a and the raw water outlet 42b are located on the same side, and thus an adapter 44 for connecting the raw water outlet 42b of the housing 42 and the raw water flow path is used. The number of the communication flow paths for connecting the raw water flow path and the raw water flow path is (n-1).
When the number n of the raw water flow paths is odd, the adapter 44 for connecting the raw water outlet 42b of the housing 42 to the raw water flow path is not necessary. The number of the communication flow paths for connecting the raw water flow path and the raw water flow path is (n-1).
No adapter for connecting the raw water inlet 42a of the housing 42 and the first raw water flow path 15 is required regardless of the number of raw water flow paths. It is also conceivable to use an adapter for connecting the raw water inlet 42a of the housing 42 and the first raw water flow path 15 instead of the adapter 44 for connecting the raw water outlet 42b of the housing 42 and the most downstream raw water flow path. However, for the following reason, it is advantageous to connect the raw water outlet 42b of the housing 42 to the most downstream raw water flow path via the adapter 44.
For example, the opening area of the first raw water flow path 15 is larger than the opening area of the third raw water flow path 17. The size of the adapter for connecting the first raw water flow path 15 and the raw water inlet 42a exceeds the size of the adapter for connecting the third raw water flow path 17 and the raw water outlet 42 b. In other words, it is advantageous from the viewpoint of the size of the components that the adapter 44 is provided on the outlet side. In addition, the pressure of the raw water in the raw water inlet 42a of the housing 42 is relatively high, and the pressure of the raw water in the raw water outlet 42b of the housing 42 is relatively low. When the adapter is attached to the raw water inlet 42a, the inside of the adapter becomes relatively high pressure, and the outside of the adapter becomes relatively low pressure. When the adapter is attached to the raw water outlet 42b, the inside of the adapter becomes relatively low pressure, and the outside of the adapter becomes relatively high pressure. In the latter case, it is more advantageous to impart pressure resistance to the adapter.
Fig. 18A is a perspective view of an example of the cover 282. The top view of fig. 18A is a view when viewed from the outer surface side of cover 282. The lower view of fig. 18A is a view when viewed from the inner surface side of cover 282. The cover 282 has a recess that functions as an opening 15p facing the first raw water flow path 15 and a communication flow path 32.
Fig. 18B is a perspective view of an example of the cover 281. The upper view of fig. 18B is a view as viewed from the outer surface side of cover 281. The lower view of fig. 18B is a view when viewed from the inner surface side of the cover 281. The cover 281 has a concave portion functioning as an opening 17p facing the third raw water flow path 17 and a communication flow path 31.
The covers 281 and 282 are resin members made by injection molding, for example. The covers 281 and 282 each have a circular shape in plan view. According to the configuration shown in fig. 18A, connection between the cover 282 and the element main body (stacked body 22) of the separation membrane element is easy. According to the configuration shown in fig. 18B, connection of the cover 281 and the element main body (stacked body 22) of the separation membrane element is easy.
Fig. 19 shows a modification of the cover 282 shown in fig. 18A. As shown in fig. 19, the cover 282 may be provided with a groove 282a for inserting a brine seal (U-shaped gasket). The groove 282a is provided over the entire circumferential direction of the cover 282. With this structure, the pad 43 described with reference to fig. 17A can be held by the cover 282.
Fig. 20 is a perspective view of an example of a cover 284 used in the separation membrane element 30 of the separation membrane module 103 shown in fig. 17C. The upper view of fig. 20 is a view when viewed from the outer surface side of the separation membrane element 30. The lower view of fig. 20 is a view when viewed from the inner surface side of the separation membrane element 30. The cover 284 has a recess that functions as an opening 15p facing the first raw water flow path 15 and a communication flow path 39. The communication flow path 39 is a flow path connecting the second raw water flow path 16 and the third raw water flow path 17. The cover 284 includes an adapter 44 that connects the fourth raw water channel 18 and the raw water outlet 42b (see fig. 17C) of the housing 42. The nozzle-like portion functioning as the adapter 44 is integrally formed with the other portions. The adapter 44 can be fitted to the raw water outlet 42b of the housing 42 using a sealing member such as an O-ring.
(embodiment of Water purifier)
Fig. 21 is a front view of a water purifier according to an embodiment of the present invention. The water purifier 200 includes a pre-filter 90, an activated carbon filter 91, and a separation membrane filter 92. The pre-filter 90, the activated carbon filter 91, and the separation membrane filter 92 are connected to each other so that raw water flows in this order. The prefilter 90 is, for example, a fiber filter made of nonwoven fabric. The separation membrane filter 92 may use the separation membrane element 10, 20, 30, 40, 50, 60, 70, or 80 of the present embodiment. With this configuration, pure water can be produced at a high recovery rate and a high flow rate of the permeated water.
The raw water is, for example, tap water. The water purifier 200 of the present embodiment can achieve a high recovery rate and a high flow rate of permeate water, and is therefore particularly suitable for use in countries and regions where water resources are scarce.
According to the water purifier 200 of the present embodiment, the tap water is purified by passing through the pre-filter 90. The tap water purified by the pre-filter 90 is further purified by the separation membrane filter 92. In detail, the tap water is purified through the pre-filter 90. The pre-filter 90 is a fiber filter through which solid components are filtered. The tap water purified by the pre-filter 90 is further purified by passing through an activated carbon filter 91. The activated carbon filter 91 adsorbs and removes components dissolved in tap water. In particular, when a reverse osmosis membrane is used as the separation membrane in the separation membrane filter 92, the reverse osmosis membrane is easily damaged by chlorine. The reverse osmosis membrane of the separation membrane filter 92 can be protected by removing the chlorine component added to the tap water for sterilization by the activated carbon filter 91. The tap water purified by the pre-filter 90 and the activated carbon filter 91 is further purified by the separation membrane filter 92. The permeate produced by the water purifier 200 is extremely pure and suitable for use as drinking water.
The pre-filter 90, the activated carbon filter 91, and the separation membrane filter 92 are housed in the casing, respectively, and attached to the main body 93 of the water purifier 200. The pre-filter 90, the activated carbon filter 91, and the separation membrane filter 92 can be removed from the main body 93 and replaced as necessary.
Examples
In order to confirm the superiority of the separation membrane element of the present invention, the following experiment was performed. A separation membrane element described with reference to fig. 13A and 13B was produced as a separation membrane element of the example. The first raw water flow path, the second raw water flow path and the third raw water flow path have the same flow path cross-sectional area. As a separation membrane element of the reference example, a laminated separation membrane element having the structure shown in fig. 22 was produced. This separation membrane element has no communication flow path, and raw water flows only in one direction.
The flow rate (cm) of permeated water in the separation membrane elements of examples and reference examples was measured by the following method 3 In/min). As raw water, a water having a concentration of 750 ppm by weight was usedAn aqueous NaCl solution comprising NaCl. The relationship between the recovery rate and the flow rate of the permeated water was examined by setting the pressure of the raw water at the inlet of the separation membrane element to 0.3MPa and changing the opening degree of the valve disposed on the downstream side of the separation membrane element. The results are shown in FIG. 23.
In fig. 23, the horizontal axis represents the recovery rate of permeated water. The vertical axis represents the flow rate of permeated water. As can be seen from the graph of fig. 23, the flow rate of the permeated water in the separation membrane element of the example greatly exceeded the flow rate of the permeated water in the separation membrane element of the reference example at all the recovery rates of the experiment. The following are examples of factors that cause such a large difference.
The cross-sectional area of the raw water channel in the separation membrane element of the example was 1/3 of the cross-sectional area of the raw water channel in the separation membrane element of the reference example. Therefore, in the case where the flow rate of the concentrated water is the same, the flow rate of the concentrated water at the outlet of the raw water flow path of the separation membrane element of the example is 3 times the flow rate of the concentrated water at the outlet of the raw water flow path of the separation membrane element of the reference example. When the flow velocity of the concentrated water is high, concentration polarization can be suppressed, and therefore the flow rate of the permeated water increases.
For example, when compared at a 50% recovery rate, the flow rate of the permeated water in the example was about 1.6 times that in the reference example. A 60% increase in the flow rate of permeate water means a 60% increase in the flow rate of concentrate water when compared at the same recovery rate. Since the flow rate of the concentrated water in the separation membrane element of the example was 1.6 times that in the separation membrane element of the reference example, the flow rate of the concentrated water at the outlet of the raw water passage of the separation membrane element of the example was about 5 times (3 × 1.6= 4.8) as compared with the flow rate of the concentrated water at the outlet of the raw water passage of the separation membrane element of the reference example. It can be said that this large difference in flow velocity of the concentrate water brings about a large difference in the flow rate of the permeate water.
Industrial applicability
The separation membrane element of the present invention can be used in various applications such as desalination of seawater, production of pure water, purification of tap water, and wastewater treatment. The separation membrane element of the present invention is suitable for applications requiring compact design, such as a water purifier for home use.

Claims (13)

1. A separation membrane element provided with:
a liquid collecting pipe;
a separation membrane disposed around the liquid collection tube;
a first end surface which is one end surface of the separation membrane in the longitudinal direction of the liquid collecting tube;
a second end surface which is the other end surface of the separation membrane in the longitudinal direction of the liquid collecting tube;
a first raw liquid channel extending linearly from the first end surface to the second end surface; and
a second raw liquid channel linearly extending from the second end surface to the first end surface,
the first raw liquid flow path is a flow path that occupies a region of a first angle in the circumferential direction of the header pipe,
the second raw liquid flow path is a flow path occupying a region of a second angle in the circumferential direction of the header pipe,
the first angle is different from the second angle,
the dope flows into the first dope channel through the first end face, flows out of the first dope channel through the second end face, and then flows into the second dope channel through the second end face.
2. The separation membrane element of claim 1,
the second raw liquid channel has a channel cross-sectional area smaller than that of the first raw liquid channel.
3. The separation membrane element of claim 1,
further comprising a plurality of partitions for partitioning the first raw liquid flow path and the second raw liquid flow path,
the plurality of partitions extend in the lengthwise direction of the liquid collecting pipe, respectively.
4. The separation membrane element of claim 3, wherein,
further comprising a stock solution spacer disposed in the first stock solution channel and the second stock solution channel,
the plurality of separators are respectively integrated with the dope spacer.
5. The separation membrane element of claim 4,
determining a first angular position and a second angular position in a circumferential direction of the header pipe,
the plurality of spacers includes a plurality of first spacers arranged in a radial direction of the header at the first angular position and a plurality of second spacers arranged in the radial direction of the header at the second angular position.
6. The separation membrane element of claim 3, wherein,
the separator is made of at least one selected from the group consisting of a hot-melt resin and a silicone sealant.
7. The separation membrane element of claim 1,
further comprising a third raw liquid channel extending linearly from the first end surface to the second end surface,
the dope flows out from the second dope channel through the first end surface, and then flows into the third dope channel through the first end surface.
8. The separation membrane element of claim 1,
further comprising at least one additional raw liquid channel extending linearly from the first end surface to the second end surface,
the dope flows out from the additional dope passage through the first end face or the second end face, then flows into another additional dope passage located on the downstream side of the additional dope passage through the first end face or the second end face through which the dope flows out from the additional dope passage again.
9. The separation membrane element of claim 1,
and folding the separation membrane to be wound on the liquid collecting pipe.
10. The separation membrane element of claim 9, wherein,
further comprising a plurality of partitions for partitioning the first raw liquid flow path and the second raw liquid flow path,
the plurality of separators extend in both the radial direction of the header pipe and the longitudinal direction of the header pipe.
11. The separation membrane element of claim 1,
further comprises a plurality of dividing elements arranged along the circumferential direction of the liquid collecting pipe,
the first raw liquid channel and the second raw liquid channel are formed by the plurality of dividing elements,
the plurality of dividing elements each include an outer wall portion and the separation membrane disposed inside the outer wall portion,
the flow of the raw liquid in the circumferential direction of the header pipe is blocked by the outer wall portions of the plurality of dividing elements.
12. A separation membrane module is provided with:
a housing; and
the separation membrane element according to any one of claims 1 to 11 disposed inside the housing.
13. A water purifier is provided with:
a pre-filter;
an activated carbon filter; and
a separation membrane filter is arranged on the upper surface of the filter body,
the pre-filter, the activated carbon filter and the separation membrane filter are connected to each other in such a manner that raw water flows in this order in sequence,
the separation membrane filter comprising the separation membrane element according to any one of claims 1 to 11.
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