WO2015125755A1

WO2015125755A1 - Hollow fiber membrane element and hollow fiber membrane module

Info

Publication number: WO2015125755A1
Application number: PCT/JP2015/054204
Authority: WO
Inventors: 一成丸井; 功次徳永; 泰樹寺島; 肇末永; 熊野　淳夫
Original assignee: 東洋紡株式会社
Priority date: 2014-02-18
Filing date: 2015-02-17
Publication date: 2015-08-27
Also published as: JPWO2015125755A1; JP6565898B2

Abstract

[Problem] To provide a hollow fiber membrane element and a hollow fiber membrane module wherein the flow rate of liquid passing through the outside of the hollow fiber membrane is rapid and stagnation of the liquid within the element does not arise easily. [Solution] A hollow fiber membrane element is provided with: a core tube connected to a supply opening or a discharge opening; a hollow fiber membrane group formed from a plurality of hollow fiber membranes; and resin walls affixing the core tube and the hollow fiber membrane group at both ends thereof. The hollow fiber membrane element is characterized by the core tube having a hole only in the vicinity of a first end, which is one end of the hollow fiber membrane group, by the plurality of hollow fiber membranes being twisted in a spiral shape around the core tube so as to cross each other, by having a cross point group that includes a plurality of cross points which are the crossing points for the hollow fiber membranes with each other, and by having the cross point group at least in the vicinity of the first end of the hollow fiber membrane group.

Description

Hollow fiber membrane element and hollow fiber membrane module

The present invention relates to a hollow fiber membrane element and a hollow fiber membrane module.

Separation and concentration of liquid mixtures by membrane separation is an energy-saving method because it does not involve phase changes compared to conventional separation techniques such as distillation, and it does not involve changes in the state of substances. It is widely used in many fields such as food separation such as separation of organic matter and recovery of organic matter from industrial wastewater. Membrane water treatment has become established as an indispensable process that supports state-of-the-art technology.

Such a water treatment using a membrane is used as a membrane module in which membranes are assembled into a pressure vessel by assembling membranes into one constituent element. In particular, a hollow fiber membrane element is a spiral membrane element. Compared with, the water permeability per unit membrane area is not large, but since the membrane area per membrane module volume can be increased, the overall water permeability can be increased and the volume efficiency is very high. Excellent compactness. Further, when both the high-concentration aqueous solution and the fresh water are supplied into the module and brought into contact via the semipermeable membrane, the concentration polarization on the membrane surface can be kept small.

For example, as a hollow fiber membrane for forward osmosis, a both-end opening type is used. In this case, the flow of the membrane permeate flows from the inside (inside the hollow portion) to the outside of the hollow fiber membrane, as shown in FIG. For example, when the high osmotic pressure draw solution (DS) (seawater) flows outside the hollow fiber membrane and the low osmotic pressure feed solution (FS) (fresh water) flows through the hollow part of the hollow fiber membrane, the permeated water Flows from the inside to the outside of the hollow fiber membrane.

In this case, the membrane permeated water, which is fresh water, flows out to the outside of the hollow fiber membrane, thereby reducing the concentration of the outer surface of the hollow fiber membrane. If the flow rate of DS flowing on the outer surface of the hollow fiber membrane is not sufficiently high, a low concentration layer (concentration polarization layer) may be formed on the outer surface of the hollow fiber membrane. In that case, the effective concentration difference, that is, the osmotic pressure difference becomes small, and the membrane permeation amount by the normal osmosis treatment obtained originally may not be obtained. The same applies when FS is not fresh water but a solution having a lower concentration than DS.

Conversely, when high osmotic pressure DS (seawater) flows through the hollow portion of the hollow fiber membrane and low osmotic pressure FS (fresh water) flows outside the hollow fiber membrane, the membrane permeate flows from the outside of the hollow fiber membrane. It flows inward. In this case, since fresh water is removed as membrane permeated water from the solution on the outer surface of the hollow fiber membrane, the concentration of the outer surface of the hollow fiber membrane increases. If the flow rate of FS flowing on the outer surface of the hollow fiber membrane is not sufficiently high, a high concentration layer (concentration polarization layer) may be formed on the outer surface of the hollow fiber membrane. In that case, the effective concentration difference, that is, the osmotic pressure difference becomes small, and the membrane permeation amount by the normal osmosis treatment obtained originally may not be obtained.

In the case of a hollow fiber membrane module for forward osmosis, a so-called cross flow is used in which the flow outside the hollow fiber membrane generated from a large number of holes provided in the core tube is substantially orthogonal to the flow inside the hollow fiber membrane. There are many cases.

In the case of cross flow, the solution flowing outside the hollow fiber membrane flows from the distribution pipe at the center of the columnar hollow fiber membrane layer to the entire hollow fiber membrane layer, but the fluid is the length of the hollow fiber membrane layer. The flow of liquid passing through the hollow fiber membrane layer (outside of the hollow fiber membrane) is small because the fluid flows in the direction and the radial direction, and the fluid drifts due to slight unevenness of the hollow fiber membrane density in the hollow fiber membrane layer. There is a drawback that concentration polarization is likely to occur on the outer surface of the hollow fiber membrane. In addition, there is a disadvantage that a so-called counter-current type (the flow outside the hollow fiber membrane and the flow inside the hollow fiber membrane are in opposite directions), which is said to be efficient in the separation operation, cannot be performed.

Patent Document 1 (Japanese Patent Publication No. 7-29029) discloses a module configuration for guiding the flow outside the hollow fiber membrane in the axial direction of the module in order to eliminate such drawbacks. Specifically, the hollow fiber membrane module described in Patent Document 1 is, for example, from the vicinity of an opening provided only at one end of a core tube (supply tube) located at the center of the module, to the other end of the hollow fiber membrane layer. By flowing the liquid in the axial direction of the module toward the discharge port provided on the side, the flow velocity outside the hollow fiber membrane is increased to try to suppress concentration polarization occurring on the outer surface of the hollow fiber membrane Is.

However, also in the module of Patent Document 1, stagnation occurs in a portion (such as the vicinity of the outer peripheral end of the opening that is the liquid supply unit) that is out of the shortest distance from the opening of the supply pipe to the discharge port, and the liquid flow rate decreases. . In such a stagnation part, the concentration polarization on the membrane surface caused by the permeation of water is not eliminated, the separation efficiency is remarkably lowered, a dead space that does not contribute to the separation occurs, and the membrane cannot be used effectively.

Considering the processing efficiency for the module installation space, it is better that the volume of containers, connection parts, etc. attached to the module is small, so it is required to increase the module size to some extent. Since the diameter is increased, the flow resistance in the radial direction perpendicular to the axial direction of the module is increased, and the water to be treated is hardly distributed in the radial direction. Particularly in such a case, it is considered that the problem of the dead space as described above becomes remarkable.

On the other hand, Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-38162) discloses a module configuration for solving the problem of dead space due to an increase in module size in the case of a cross flow. That is, Patent Document 2 discloses a cross arrangement in which a hollow fiber membrane bundle is wound on a porous core material at an angle with the vertical axis of the hollow fiber membrane bundle group, and crosses alternately for each hollow fiber membrane bundle. The cross-point group with low packing density where the hollow fiber membranes intersect is concentratedly arranged near the supply part opposite to the concentrated water discharge part, and the outer periphery from the center of the cross section perpendicular to the vertical axis of the hollow fiber membrane bundle group A hollow fiber membrane module that is continuously aligned in the direction of the part is disclosed.

However, in the module of Patent Document 2, in the case of the cross flow, the problem that the flow rate of the liquid passing through the outside of the hollow fiber membrane is basically small cannot be solved.

Japanese Patent Publication No. 7-29029 JP 2001-38162 A

The present invention was devised in view of the current state of the prior art described above, and its purpose is that the flow rate of the liquid passing through the outside of the hollow fiber membrane is high and liquid stagnation hardly occurs in the element. It is to provide a yarn membrane element and a hollow fiber membrane module.

As a result of further diligent investigations on the crossing arrangement employed in the hollow fiber type reverse osmosis membrane element in order to achieve the above object, the present inventor has determined the flow direction of the fluid flowing outside the hollow fiber membrane for forward osmosis as the axis. The element structure to be oriented can reduce the concentration polarization of the outer surface of the hollow fiber membrane and reduce the loss of the permeated water amount due to forward osmosis, so that the permeated water amount can be obtained efficiently, leading to the completion of the present invention. It was.

That is, the present invention has the following configurations (1) to (6).
(1) a core tube connected to a supply port or a discharge port;
A group of hollow fiber membranes comprising a plurality of hollow fiber membranes;
A hollow fiber membrane element comprising a resin wall for fixing the core tube and the hollow fiber membrane group at both ends thereof,
The core tube has a hole only in the vicinity of the first end which is one end of the hollow fiber membrane group,
The plurality of hollow fiber membranes are spirally wound around the core tube so as to cross each other, and have a cross point group including a plurality of cross points that are intersections of the hollow fiber membranes,
The hollow fiber membrane element, wherein the cross point group exists at least in the vicinity of the first end of the hollow fiber membrane group.
(2) The hollow fiber membrane element according to (1), wherein the cross point group is present in the vicinity of a second end that is one end opposite to the first end of the hollow fiber membrane group.
(3) The hollow fiber membrane element according to (1) or (2), wherein the cross points are continuously aligned in a plane direction perpendicular to the axis of the core tube.
(4) The hollow fiber membrane group according to any one of (1) to (3), wherein the hollow fiber membrane group is covered with a cylindrical non-permeable film except for the vicinity in the vicinity of the second end. element.
(5) The hollow fiber membrane element according to any one of (1) to (4), which is used for forward osmosis or reverse osmosis.
(6) A hollow fiber membrane module comprising the hollow fiber membrane element according to any one of (1) to (5) and a container loaded with at least one hollow fiber membrane element.

According to the present invention, it is possible to provide a hollow fiber membrane element and a hollow fiber membrane module in which the flow rate of liquid passing through the outside of the hollow fiber membrane is high and liquid stagnation does not easily occur in the element.

Thereby, the concentration polarization on the outer surface of the hollow fiber membrane can be reduced in the entire element, and the loss of the amount of permeated water can be reduced, so that membrane separation can be performed efficiently. In addition, a so-called counter-current type separation operation that is said to be efficient in the separation operation can be performed.

It is a cross-sectional schematic diagram which shows one Embodiment of the hollow fiber membrane module of this invention. It is another schematic diagram which shows one Embodiment of the hollow fiber membrane element of this invention. It is a schematic diagram for demonstrating the relationship between the number of winds and the cross | intersection part in the hollow fiber membrane element of this invention. It is a schematic diagram for demonstrating the flow of membrane permeated water at the time of using the hollow fiber membrane for forward osmosis | permeation.

Hereinafter, an embodiment of the hollow fiber membrane element and the hollow fiber membrane module of the present invention will be described with reference to the drawings.

Referring to FIG. 1, the hollow fiber membrane element of the present embodiment includes a core tube 20 connected to a supply port 10, a hollow fiber membrane group including a plurality of hollow fiber membranes 21, a core tube 20 and a hollow fiber membrane. And

resin walls

51 and 52 for fixing the group at both ends thereof. The core tube 20 has a hole 20a only in the vicinity of the first end 4a which is one end of the hollow fiber membrane group.

The fluid flowing out from the hole 20a is dispersed in the radial direction of the hollow fiber membrane element in the vicinity of the resin wall, and then flows in the axial direction of the element (core tube) on the outer side 3 of the hollow fiber membrane. In such a hollow fiber membrane element, the flow velocity of the fluid on the outer side (outer surface) 3 of the hollow fiber membrane can be increased, so that the concentration polarization of the outer surface of the hollow fiber membrane can be reduced, and the loss of the amount of permeated water due to forward osmosis is reduced. By reducing, it becomes possible to obtain the amount of permeate efficiently. In addition, a so-called counter-current type separation operation in which the flow directions of DS and FS, which are said to be efficient in the separation operation, are opposite to each other, is possible. In particular, in the case of reverse osmosis, there is a self-cleaning effect in which fine suspended substances contained in the fluid to be treated are swept away without staying in the hollow fiber layer.

Thus, fresh water can be taken out from the low-concentration feed liquid, or the fresh water can be taken out to concentrate the low-concentration feed liquid or recover energy from the osmotic flow. Specifically, a high pressure osmotic aqueous solution (seawater) and a low pressure, low osmotic pressure fresh water are brought into contact with each other through a forward osmosis membrane, so that the low pressure fresh water has a high pressure and high osmosis through the membrane. The energy can be recovered by flowing into the pressurized aqueous solution and rotating the turbine or the like with the pressurized aqueous solution.

Further, the hollow fiber membrane group is covered with a cylindrical impermeable film 6 except for the vicinity in the vicinity of the second end 4b which is one end opposite to the first end 4a. Thereby, it can suppress that a short circuit flow arises in the clearance gap between a hollow fiber membrane group and a container, and can utilize a supply liquid efficiently as an axial flow between hollow fiber membranes.

The above-described hollow fiber membrane element can be made into a hollow fiber membrane module by loading one or more of them into a container, particularly a pressure vessel having pressure resistance that can withstand the operating pressure.

The hollow fiber membrane module shown in FIG. 1 includes at least the hollow fiber membrane element described above and a container 1 loaded with at least one hollow fiber membrane element. The

resin walls

51 and 52 of the hollow fiber membrane element are liquid-tightly fixed to the inner wall of the container 1 by O-

rings

51a and 52a.

This hollow fiber membrane module has a supply port 10 connected to the core tube 20, a supply port 11 and a discharge port 12 communicating with the inside of the hollow fiber membrane 21, and is fixed by

wall members

14 and 15. . Further, a discharge port 13 communicating with the outside of the hollow fiber membrane 21 through a portion not covered with the surrounding non-permeable film 6 in the vicinity of the second end 4 b is provided on the side surface of the container 1.

However, in FIG. 1, for the sake of simplicity, the hollow fiber membrane 21 is drawn so as to be parallel to the core tube 20, but in practice, a plurality of hollow fibers are used so that the plurality of hollow fiber membranes cross each other. A hollow fiber membrane bundle made of a membrane is spirally wound around the core tube 20. This point will be described with reference to FIG.

Referring to FIG. 2, in the hollow fiber membrane element of the present embodiment, the plurality of hollow

fiber membrane bundles

22a and 22b are spirally wound around the core tube 20 so that the plurality of hollow

fiber membrane bundles

22a and 22b intersect each other. It is wound in a shape. In other words, being wound spirally means that the array of hollow fiber membranes is wound at an angle with the axis of the core tube. Here, it has the cross point group 24 containing two or more cross points 23 which are the crossing parts of the hollow fiber membranes 21 which comprise the hollow

fiber membrane bundles

22a and 22b.

By arranging the plurality of hollow fiber membranes so as to intersect with each other, voids are regularly formed in the cross point group including a plurality of intersections (cross points) of the hollow fiber membranes. Due to the existence of the regular voids, the pressure loss of the fluid flowing on the outer side 3 of the hollow fiber membrane is small in the cross point group. In addition, since non-dissolved components and particle components in the fluid flowing on the outer side 3 of the hollow fiber membrane are rarely trapped between the hollow fiber membranes, it is difficult for pressure loss to increase.

On the other hand, when the hollow fiber membrane is arranged in parallel to the core tube (particularly when it is not closest packed), the gap between the hollow fiber membranes is likely to vary, and the pressure loss of the fluid flowing outside the hollow fiber membrane 3 Since the fluid flows only in the portion where the pressure loss is small, the drift is likely to occur. In addition, non-dissolved components and particle components in the fluid are trapped between the hollow fiber membranes, and the pressure loss is likely to increase.

Therefore, by arranging the hollow fiber membranes in an intersecting manner, the pressure loss of the fluid flowing on the outer side 3 of the hollow fiber membrane is small, so that it is difficult for drift to occur. In particular, in the case of reverse osmosis, the allowable amount of contaminants composed of non-dissolved components of the fluid flowing on the outer side 3 of the hollow fiber membrane is larger than that in the parallel arrangement, and the contamination resistance of the hollow fiber membrane element is improved. To do.

The hollow fiber membrane element of this embodiment is characterized in that the cross point group 24 exists at least in the vicinity of the first end 4a of the hollow fiber membrane group. In addition, it is preferable that the cross point group 24 exists in the vicinity of a surface perpendicular to the axis of the core tube 20 passing through the hole 20a of the core tube 20.

In the cross point group, a large distance is secured between the hollow fiber membranes, and the fluid to be treated flowing outside the hollow fiber membrane is easily dispersed in the radial direction of the hollow fiber membrane group (hollow fiber membrane element) from the vicinity of the core tube. For this reason, by adjusting so that the cross point group is positioned in the vicinity of the first end 4a of the hollow fiber membrane group, for example, the fluid flowing out from the hole 20a of the core tube 20 can flow in the radial direction of the hollow fiber membrane element. It becomes easy to disperse | distribute and generation | occurrence | production of the dead space in the outer peripheral side of a hollow fiber membrane element is suppressed.

In this embodiment, the case where the core tube is connected to the supply port (when the liquid is supplied from the hole of the core tube to the outer surface of the hollow fiber membrane) has been described, but the core tube is connected to the discharge port. When the liquid on the outer surface of the hollow fiber membrane is discharged through the hole in the core tube, the fluid on the outer peripheral side of the hollow fiber membrane element easily flows into the hole in the core tube, Generation of dead space on the outer peripheral side of the yarn membrane element is suppressed.

In the hollow fiber membrane element of the present embodiment, the cross point group 24 also exists in the vicinity of the second end 4b that is one end opposite to the first end 4a of the hollow fiber membrane group. When the core tube 20 having the hole 20a only in the vicinity of the first end 4a is used, the dead space is likely to occur not only in the outer peripheral portion on the first end 4a side but also in the vicinity of the core tube 20 at the second end 4b. . Since the cross point group 24 also exists in the vicinity of the second end 4b, it is possible to suppress the occurrence of dead space in the vicinity of the core tube 20 of the second end 4b.

Note that, as shown in FIG. 2, the cross points 23 are preferably continuously aligned in a plane direction perpendicular to the axis of the core tube 20. Thereby, the radial fluid resistance in the cross point group 24 can be further reduced, and the occurrence of dead space can be more reliably suppressed.

The hollow fiber membrane element of the present embodiment is formed by, for example, spirally winding a hollow fiber membrane around a core tube and laminating the hollow fiber membranes in a radial direction with the hollow fiber membranes arranged in a cross shape. After sealing both ends of the hollow fiber membrane wound body with resin, a part of the resin (resin wall) is cut to open both ends of the hollow fiber membrane.

If the hollow fiber membrane is thin and does not have sufficient strength, as described above, the hollow fiber membrane is formed into a cross shape by winding the hollow fiber membrane bundle of a plurality of hollow fiber membranes in a cross shape. You may arrange in.

Hereinafter, specific examples of each component of the hollow fiber membrane element and the hollow fiber membrane module of the present embodiment will be described.

The core tube is a tubular member having a function of distributing the fluid supplied from the supply port to the outer side 3 (outer surface) of the hollow fiber membrane in the hollow fiber membrane element when connected to the supply port. It is preferable that the core tube is positioned substantially at the center of the hollow fiber membrane element.

When the diameter of the core tube is too large, the area occupied by the hollow fiber membrane in the membrane module is reduced, and as a result, the membrane area of the membrane element or the membrane module is reduced, so that the water permeability per volume may be lowered. Further, if the diameter of the core tube is too small, pressure loss increases when the supply fluid flows in the core tube, and as a result, the effective differential pressure applied to the hollow fiber membrane may be decreased and the processing efficiency may be reduced. In addition, the core tube may be damaged due to the strength of the hollow fiber membrane that is reduced when the supply fluid flows through the hollow fiber membrane layer due to a decrease in strength. It is important to set an optimum diameter in consideration of these influences comprehensively. The area ratio of the cross-sectional area of the core tube to the cross-sectional area of the hollow fiber membrane element is preferably 4 to 20%.

The material of the hollow fiber membrane is not particularly limited as long as the desired separation performance (preferably high separation performance equivalent to the reverse osmosis membrane) can be expressed. For example, cellulose acetate resin, polyamide resin, sulfonated polysulfone resin Polyvinyl alcohol resins can be used. Among these, sulfonated polysulfone resins such as cellulose acetate resin, sulfonated polysulfone, and sulfonated polyethersulfone are resistant to chlorine as a fungicide, and can easily suppress the growth of microorganisms. preferable. In particular, there is a feature that can effectively suppress microbial contamination on the membrane surface. Among cellulose acetates, cellulose triacetate is preferable from the viewpoint of durability.

The outer diameter of the hollow fiber membrane is not particularly limited as long as it is used for a forward osmosis membrane. For example, the outer diameter is 160 to 320 μm. If the outer diameter is smaller than the above range, the inner diameter is inevitably small, and thus the flow pressure loss of the fluid flowing through the hollow portion of the hollow fiber membrane becomes large, which may cause a problem. On the other hand, if the outer diameter is larger than the above range, the membrane area per unit volume in the module cannot be increased, and the compactness that is one of the merits of the hollow fiber membrane module is impaired.

The hollow rate of the hollow fiber membrane is not particularly limited as long as it is used for the forward osmosis membrane. For example, 15 to 45%. When the hollow ratio is smaller than the above range, the flow pressure loss of the hollow portion is increased, and a desired amount of permeated water may not be obtained. Moreover, when the hollow ratio is larger than the above range, there is a possibility that sufficient pressure resistance cannot be ensured even when used in forward osmosis treatment. The hollow ratio (%) is expressed by the following formula:
Hollow ratio (%) = (inner diameter / outer diameter) ² × 100
It can ask for.

The non-permeable film is not particularly limited as long as it does not substantially permeate the fluid flowing outside the hollow fiber membrane (liquid to be treated) or has a large pressure loss when the fluid permeates, It is preferable to use a commercially available resinous film, rubber sheet, cloth with small eyes, and the like.

In order for the non-permeable film to withstand the pressure loss of the fluid flowing outside the hollow fiber membrane, a support member may be wound on the non-permeable film. As the support member, linear materials such as natural fibers, synthetic polymer fibers, inorganic fibers, or woven fabrics themselves, or those in which an adhesive is attached thereto are used. This support member maintains the pressure difference between the inside and outside of the hollow fiber membrane assembly.

In the hollow fiber membrane element of the present invention, in order to improve the uniformity of the axial flow of the fluid flowing outside the hollow fiber membrane, a rectifying member such as a rectifying plate may be provided in the hollow fiber membrane layer. .

The outer diameter of the hollow fiber membrane wound body is preferably 130 to 420 mm. If the outer diameter is too large, operability in maintenance management such as membrane exchange work may be deteriorated. If the outer diameter is too small, the membrane area per unit membrane element is reduced, the processing amount is reduced, and this is not preferable from the viewpoint of economy.

The length of the hollow fiber membrane wound body is preferably 0.2 to 1.6 m. When this length is too long, the flow pressure loss inside the hollow of the hollow fiber membrane increases, and the forward osmosis performance can be lowered. For this reason, it is preferable to shorten the length, particularly when the module is enlarged. However, if it is too short, the membrane area per unit membrane element is reduced and the amount of treatment is reduced, which is not preferable in terms of economy. Moreover, when the ratio with the outer diameter of the hollow fiber membrane winding body is small, the fluid to be treated is difficult to flow in the axial direction.

In the hollow fiber membrane wound body, the number of windings (winding number) of the hollow fiber membrane is not particularly limited. For example, as shown in (a) to (c) of FIG. .0. In each of (a) to (c) of FIG. 3, the number of crosspoint groups (including both ends) is 5, 4, and 3. If the number of winds is 0.5 or more, the cross point group can be formed at two or more places including both ends, so that both the vicinity of the first end and the vicinity of the second end are crossed. A point group can be arranged and can be suitably used in the present invention.

As the hollow fiber membrane, for example, as described in Japanese Patent No. 3591618, a membrane-forming solution composed of cellulose triacetate, ethylene glycol (EG), and N-methyl-2-pyrrolidone (NMP) is obtained from a three-part nozzle. A hollow fiber membrane is obtained by discharging, passing through the air running part, and immersed in a coagulating liquid consisting of water / EG / NMP, and then the hollow fiber membrane is washed with water and then heat treated to produce a cellulose acetate-based hollow fiber membrane. can do. Also, after purifying the copolymer polyamide obtained by low-temperature solution polymerization method from terephthalic acid dichloride, 4,4'-diaminodiphenylsulfone, and piperazine, it is dissolved in a dimethylacetamide solution containing CaCl ₂ and diglycerin to form a film-forming solution. The polyamide-based hollow fiber membrane can be produced by discharging this solution from the three-divided nozzle through the aerial running section into the coagulating liquid, washing the resulting hollow fiber membrane with water, and then heat-treating it.

The hollow fiber membrane obtained as described above is incorporated into the hollow fiber membrane element by a conventionally known method. Incorporation of the hollow fiber membrane is, for example, 45 to 90 hollow fiber membranes as described in Japanese Patent No. 4421486, Japanese Patent No. 4277147, Japanese Patent No. 3591618, Japanese Patent No. 3008886 or the like. More than that is collected into one hollow fiber membrane assembly, and a plurality of these hollow fiber membrane assemblies are arranged side by side as a flat hollow fiber membrane bundle and wound around a core tube having a large number of holes while traversing. By adjusting the length and rotation speed of the core tube and the traverse speed of the hollow fiber membrane bundle at this time, the core tube is wound up so that an intersection is formed on the peripheral surface at a specific position. Next, the wound body is cut at a predetermined position by adjusting the length and the position of the intersection. After that, on the outer periphery of the wound body of the hollow fiber, the non-permeable film is arranged, leaving the opposite side of the core tube with the hole, and after bonding both ends of the wound body, both sides are cut. Then, a hollow fiber membrane opening is formed to produce a hollow fiber membrane element.

In addition, the hollow fiber membrane element of the present invention can take a larger membrane area per element than a spiral flat membrane, and depending on the size of the hollow fiber membrane, A membrane area approximately 10 times that of the spiral type can be obtained. Therefore, the hollow fiber membrane may have a very small amount of treatment per unit membrane area when obtaining the same water permeation amount, and can reduce the contamination of the membrane surface that occurs when the supply water permeates the membrane as compared to the spiral type. The operation time until the membrane is washed can be increased. Furthermore, since the drift in the element is difficult to occur, it is suitable for water treatment using a concentration difference as a driving force.

The hollow fiber membrane module of the present invention ensures a radial flow even when the module size is increased (particularly when the module diameter is increased and the length is shortened). It eliminates the dead space inside and realizes a uniform distribution flow from the supply side to the drainage side, can effectively use the membrane without causing uneven flow, can increase the separation efficiency, and can continuously operate stably, The detergency can also be improved.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In addition, the measurement of the characteristic value measured in the Example followed the following method.

(1) Measurement of the inner diameter, outer diameter, and hollow ratio of the hollow fiber membrane An appropriate number of hollow fiber membranes are passed through a hole of 3 mm in diameter in the center of the slide glass so that the hollow fiber membrane does not fall out, and the upper and lower surfaces of the slide glass. The hollow fiber membrane was cut along with a razor to obtain a hollow fiber membrane cross-sectional sample. Next, using a projector Nikon PROFILE PROJECTOR V-12, the short diameter and the long diameter in two directions are measured for each cross section of the hollow fiber membrane, and the respective arithmetic average values are calculated as the inner diameter and the outer diameter of the cross section of the hollow fiber membrane. It was. The same measurement was performed for the five cross sections, and the average values were defined as the inner diameter and outer diameter of the hollow fiber membrane. The hollow ratio was calculated by (inner diameter / outer diameter) ² × 100.

(2) Element length measurement One end of a hollow fiber membrane element in which both ends of the hollow fiber membrane winding body are sealed with resin, and then a part of the resin (resin wall) is cut to open both ends of the hollow fiber membrane. It was obtained by measuring a linear distance parallel to the central axis from the other end to the other end.

(3) Measurement of element diameter The diameter of the resin wall of the hollow fiber membrane element was measured.

(4) Measurement of membrane area per element The membrane area is calculated from the following formula: from the outer diameter of the hollow fiber membrane, the number of hollow fiber membranes present in the hollow fiber membrane element, and the average effective length of the hollow fiber membranes:
Membrane area (m ² ) = π × Outer diameter of hollow fiber membrane (m) × Number of hollow fiber membranes × Average effective length of hollow fiber membrane (m)
Determined by

The average effective length of the hollow fiber membrane was calculated as follows.
Measure the distance between the inner sides of the resin at the end of the element, that is, the apparent effective length (LE) of the hollow fiber membrane, the outer diameter (DO) of the element body, and the outer diameter (DI) of the core tube. Value with wind number (WD) in the following formula:
LO2 = LE ² + (π × DO × WD) ²
LI2 = LE ² + (π × DI × WD) ²
Average effective length = ((LO2) ^0.5 + (LI2) ^0.5 ) / 2
By substituting into, the average effective length can be calculated.

(5) Measurement of the number of winds The number of winds was determined from the number of times (the number of rotations) the hollow fiber membrane was wound on the central axis (core tube) from one end to the other end of the hollow fiber membrane roll-up body.

(6) Measurement of filling rate By dividing the total volume of hollow fiber membranes (hollow fiber membrane outer diameter standard) present in the hollow fiber membrane wound body by the volume of the hollow fiber membrane wound body (by the following formula), the filling rate Asked.

Filling factor (%) = π × (outer diameter of the hollow fiber ^{^{membrane) 2/4 (m 2)}} × total overall length (m) / hollow fiber membrane winding body volume of the hollow fiber membrane ^{(m 3)} × 100%
In addition, hollow fiber membrane rolled-up body volume = π × DO ² × LE
Total length of hollow fiber membranes = average effective length × number of hollow fiber membranes.

(7) Measurement of water permeability One hollow fiber membrane element is loaded into a pressure vessel to produce a hollow fiber membrane module, and among the nozzles communicating with the respective openings of the hollow fiber membrane, the sodium chloride concentration from one nozzle 0.2 g / L of fresh water was supplied by a supply pump, and fresh water was discharged from the other nozzle. On the other hand, a high-concentration aqueous solution having a sodium chloride concentration of 70 g / L is supplied to a core tube communicating with the outside of the hollow fiber membrane by a supply pump, and after passing through the outside of the hollow fiber membrane, communicates with the outside of the hollow fiber membrane assembly. The pressure and flow rate are adjusted with a flow rate adjustment valve.

The supply pressure of the high concentration aqueous solution is PDS1 (MPa), the supply flow rate is QDS1 (L / min), the amount of discharged water of the high concentration aqueous solution is QDS2 (L / min), the supply flow rate of fresh water is QFS1 (L / min), When the outflow flow rate was QFS2 (L / min) and the freshwater outflow pressure was PFS2 (kPa), the flow rate increment (QDS2-QDS1) of the high-concentration aqueous solution under the conditions was measured as the water permeability of the module. The temperature was adjusted to 25 ° C.

PDS1 = 2.2 MPa
PFS2 = 10 kPa or less QDS1 / (QDS2-QDS1) = 2
QFS2 / (QDS2-QDS1) = 0.1
However, the inlet pressure of fresh water was set to 0.1 MPa, and when it exceeded 0.1 MPa, QFS1 was set to be 0.1 MPa.

(Comparative Example 1)
Cellulose triacetate (CTA, Daicel Chemical Industries, LT35) 41% by weight, N-methyl-2-pyrrolidone (NMP, Mitsubishi Chemical) 50% by weight, ethylene glycol (EG, Mitsubishi Chemical) 8.7% by weight, Benzoic acid (Nacalai Tesque) 0.3% by weight was uniformly dissolved at 180 ° C. to obtain a film forming stock solution. The obtained film-forming stock solution was degassed under reduced pressure, and then discharged from an arc-type (three-division) nozzle into a space cut off from the outside air at 163 ° C. After passing through a space time of 0.03 seconds, NMP / EG / It was immersed in a 12 ° C. coagulation bath consisting of water = 4.25 / 0.75 / 95. Subsequently, the hollow fiber membrane was washed by a multistage inclined submerged washing method and shaken off in a wet state. The obtained hollow fiber membrane was immersed in water at 90 ° C. and subjected to hot water treatment for 20 minutes. The obtained hollow fiber membrane had an inner diameter of 85 μm and an outer diameter of 175 μm.

The obtained hollow fiber membranes were arranged in a crossing manner around a core tube having a hole radially about 20 cm from one end to form an aggregate of hollow fiber membranes. The bundle of hollow fiber membranes was traversed while rotating the core tube about its axis, and the hollow fiber membranes were arranged in a crossing manner by being wound around the core tube. After both ends of the hollow fiber membrane assembly were fixed by potting with an epoxy resin, the both ends of the resin portion were cut to open the hollow portion of the hollow fiber membrane, thereby producing a hollow fiber membrane element. In that case, the outer peripheral part except the part about 30 cm center side from the other edge part was covered with the non-permeable film.

The obtained hollow fiber membrane element had a wind number of 2, a length of about 110 cm, an outer diameter of 130 mm, a hollow fiber membrane filling rate of 51%, and a membrane area of 105 m ² . In addition, the intersection part (cross point group) of this hollow fiber membrane existed in the part of about 1/4 length of element length from both ends, respectively. That is, in Comparative Example 1, the hollow fiber membrane group is crossed both near the first end (near the core tube hole) and near the second end (near the position where the non-permeable film is not covered). There was no point group.

This hollow fiber membrane element was loaded into a pressure vessel to produce a hollow fiber membrane module. About the obtained hollow fiber membrane module, the water permeability of said (7) was measured. In this case, the test was performed in a direction in which the flow direction of fresh water and the flow direction of salt water face each other, that is, in a countercurrent state. The results are shown in Table 1.

(Comparative Example 2)
Using the same module as in Comparative Example 1, the same test as in Comparative Example 1 was performed, except that the flow direction of fresh water and the flow direction of salt water were the same direction, that is, a parallel flow state. The results are shown in Table 1.

Example 1
A hollow fiber membrane similar to Comparative Example 1 was used in the same manner as in Comparative Example 1 except that the intersection of the hollow fiber membranes was present only near the first end (near the hole in the core tube). A membrane element was prepared. This hollow fiber membrane element was loaded into a pressure vessel and tested as a module in the same manner as in Comparative Example 1. The results are shown in Table 1.

(Example 2)
Comparative Example 1 except that the same hollow fiber membrane as in Comparative Example 1 was used and the intersection of the hollow fiber membranes was present only in the vicinity of the second end (near the position where the non-permeable film was not covered). A hollow fiber membrane element was produced in the same manner as described above. This hollow fiber membrane element was loaded into a pressure vessel and tested as a module in the same manner as in Comparative Example 1. The results are shown in Table 1.

Example 3
A hollow fiber membrane was used in the same manner as in Comparative Example 1 except that the same hollow fiber membrane as in Comparative Example 1 was used and the intersection of the hollow fiber membranes was present in the vicinity of the first end and in the vicinity of the second end. An element was produced. This hollow fiber membrane element was loaded into a pressure vessel and tested as a module in the same manner as in Comparative Example 1. The results are shown in Table 1.

(Comparative Example 3)
Using the same hollow fiber membrane as in Comparative Example 1, the hollow fiber membranes were arranged in a crossing manner around the porous core tube to form an aggregate of hollow fiber membranes. The bundle of hollow fiber membranes was traversed while rotating the porous core tube about its axis, and the hollow fiber membranes were arranged in a crossing manner by being wound around the porous core tube. After both ends of the hollow fiber membrane assembly were fixed by potting with an epoxy resin, the both ends of the resin portion were cut to open the hollow portion of the hollow fiber membrane, thereby producing a hollow fiber membrane element.

The obtained hollow fiber membrane element had a wind number of 1, a length of about 110 cm, an outer diameter of 130 mm, a hollow fiber membrane filling rate of 51%, and a membrane area of 105 m ² . The hollow fiber membrane element was loaded into a pressure vessel and various tests were conducted as a module. The results are shown in Table 1 together with details of the hollow fiber membrane and elements.

From the results shown in Table 1, in Examples 1 to 3 in which the cross point group is arranged near the first end or the second end, the comparative example in which the cross point group is not arranged near the first end or the second end It can be seen that the amount of permeate increases more than 1 and 2. In particular, in Example 3 in which the cross point group is arranged in both the vicinity of the first end and the vicinity of the second end, the permeated water amount is increased as compared with Examples 1 and 2. In the above examples, measurements are performed using a relatively small hollow fiber membrane module, but when similar measurements are performed using a larger module, the difference between the examples and comparative examples, The difference between the third embodiment and the first and second embodiments is predicted to be more remarkable.

It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

The hollow fiber membrane element of the present invention has a high water permeability of the membrane, and is extremely useful in the field of generating energy by using water treatment or a concentration difference as a driving force.

Specifically, it can be used for concentration and recovery of organic substances, volume reduction by concentration of waste water, desalination of seawater, and the like. Also, fresh water is permeated using the difference in concentration between the low concentration aqueous solution and the high concentration pressurized aqueous solution as a driving force, and the turbine is operated with the flow rate and pressure of the high concentration aqueous solution in the pressurized state increased by the permeated fresh water. It can be used to generate energy by turning it. In particular, it can be suitably used for fresh water treatment for generating energy such as electric power by utilizing osmotic pressure due to a difference in concentration between seawater or concentrated seawater and fresh water.

1 container, 10, 11 supply port, 12, 13 discharge port, 14, 15 wall member, 20 core tube, 21 hollow fiber membrane, 22a, 22b hollow fiber membrane bundle, 23 cross point, 24 cross point group, 3 hollow fiber Outside of membrane, 4a first end, 4b second end, 51, 52 Resin wall, 6 Non-permeable film.

Claims

A core tube connected to the supply or discharge port;
A group of hollow fiber membranes comprising a plurality of hollow fiber membranes;
A hollow fiber membrane element comprising a resin wall for fixing the core tube and the hollow fiber membrane group at both ends thereof,
The core tube has a hole only in the vicinity of the first end which is one end of the hollow fiber membrane group,
The plurality of hollow fiber membranes are spirally wound around the core tube so as to cross each other, and have a cross point group including a plurality of cross points that are intersections of the hollow fiber membranes,
The hollow fiber membrane element, wherein the cross point group exists at least in the vicinity of the first end of the hollow fiber membrane group.
Further, the hollow fiber membrane element according to claim 1, wherein the cross point group is present in the vicinity of a second end which is one end opposite to the first end of the hollow fiber membrane group.
The hollow fiber membrane element according to claim 1 or 2, wherein the cross points are continuously aligned in a plane direction perpendicular to the axis of the core tube.
The hollow fiber membrane element according to any one of claims 1 to 3, wherein the hollow fiber membrane group is covered with a cylindrical non-permeable film except for the vicinity in the vicinity of the second end.
The hollow fiber membrane element according to any one of claims 1 to 4, which is used for forward osmosis or reverse osmosis.
A hollow fiber membrane module comprising the hollow fiber membrane element according to any one of claims 1 to 5 and a container loaded with at least one hollow fiber membrane element.