JP7740239B2 - Hollow fiber membrane module - Google Patents

Description

The present invention relates to a hollow fiber membrane module.

When conventional hollow fiber membrane modules are used in membrane processes such as forward osmosis, their structure means that the draw solution (DS) may leak into the feed solution (FS). Such DS leakage reduces the efficiency of the membrane process. In particular, when expensive polymer-based DS is used, DS leakage increases the operating costs of the membrane process. Therefore, measures to prevent leakage are necessary.

In the hollow fiber membrane modules disclosed in Patent Document 1 (International Publication No. 2005/011850) and Patent Document 2 (Japanese Patent Application Laid-Open No. 2008-100127), the permeate fluid collection member is fixed in abutment against the end (end face) of the hollow fiber membrane element by snaps (connecting members) fitted into both a recess provided on the outer surface of the longitudinal end of the hollow fiber membrane element and a recess provided on the outer surface of the permeate fluid collection member.

WO 2005/011850 Japanese Patent Application Laid-Open No. 2008-100127

However, when the pressure inside and outside the hollow fiber membrane is the same, as in FO processing, the pressure of the fluid (DS or FS) flowing through the hollow fiber membrane may become higher than the pressure of the fluid (FS or DS) flowing outside the hollow fiber membrane during FO processing.

In hollow fiber membrane modules in which the permeate fluid collection member and hollow fiber membrane element are secured with snaps, as disclosed in Patent Documents 1 and 2, if the pressure difference between the inside of the hollow portion and the outside of the hollow fiber membrane exceeds a predetermined value, the permeate fluid collection member and the end of the hollow fiber membrane element may separate, creating a gap between them (see Figures 4 and 7). When a gap is created, the DS and FS come into direct contact, causing the DS to diffuse (leak) toward the FS.

As such, even in the hollow fiber membrane modules disclosed in Patent Documents 1 and 2, there was a possibility of leakage of DS or FS (direct contact between DS and FS).

Therefore, the present invention aims to provide a hollow fiber membrane module that can prevent leakage of draw solution or feed solution during membrane processes such as forward osmosis.

(1) a pressure vessel;
at least one hollow fiber membrane element disposed in the pressure vessel;
a water collecting cap fixed liquid-tightly to the outer peripheral surface of the end of the hollow fiber membrane element;
A hollow fiber membrane module comprising:
(2) The hollow fiber membrane module according to (1), wherein a groove for an O-ring is provided on the inner peripheral surface of the water collecting cap, and an O-ring is placed in the groove, so that the water collecting cap is fixed liquid-tightly to the outer peripheral surface of the end of the hollow fiber membrane element.
(3) The hollow fiber membrane module according to (1) or (2), wherein the water collecting cap is fixed in a liquid-tight manner to the outer peripheral surface of an outer ring provided at the end of the hollow fiber membrane element.
(4) The hollow fiber membrane module according to any one of (1) to (3), which is used for forward osmosis treatment.
(5) The hollow fiber membrane module according to any one of (1) to (4), wherein the water collecting cap has a recess on its outer peripheral surface extending in the longitudinal direction of the pressure vessel.
(6) The at least one hollow fiber membrane element is a plurality of hollow fiber membrane elements,
The hollow fiber membrane module according to (5), wherein the plurality of hollow fiber membrane elements are connected in series within the pressure vessel.
(7) The hollow fiber membrane module according to (5) or (6), wherein the recesses of the water collecting cap form flow paths that communicate with the outside of the hollow fiber membranes of two adjacent hollow fiber membrane modules.

The present invention provides a hollow fiber membrane module that can prevent leakage of draw solution or feed solution during membrane processes such as forward osmosis.

FIG. 1 is a cross-sectional schematic view showing an example of a hollow fiber membrane module according to an embodiment. FIG. 2 is a partial enlarged view of the inlet side of the hollow fiber membrane module shown in FIG. 1. FIG. 2 is a partial enlarged view of a connection portion of the hollow fiber membrane module shown in FIG. 1. FIG. 10 is a perspective view of a water collecting cap for the inlet or outlet side used in the embodiment. 5 is a perspective view of the water collecting cap shown in FIG. 4 as seen from the opposite side. FIG. FIG. 10 is a perspective view of a water collecting cap for a connecting portion used in the embodiment. FIG. 2 is a perspective view showing a connector for a connecting portion used in the embodiment. 1A is a cross-sectional view showing a conventional notched outer ring, and FIG. 1B is a cross-sectional view showing a flat outer ring. FIG. 1 is a cross-sectional view showing an example of a conventional hollow fiber membrane module. FIG. 1 is a cross-sectional schematic view showing another example of a conventional hollow fiber membrane module.

An example of a hollow fiber membrane module of the present invention will be described below with reference to the drawings. Note that in the drawings, the same reference symbols represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been changed as appropriate to clarify and simplify the drawings, and do not represent actual dimensional relationships.

<Hollow fiber membrane module>
The hollow fiber membrane module is
A pressure vessel;
at least one hollow fiber membrane element disposed in the pressure vessel;
a water collecting cap fixed liquid-tightly to the outer peripheral surface of the end of the hollow fiber membrane element;
Equipped with.

Below, we will describe a hollow fiber membrane module including multiple hollow fiber membrane elements as an example of a hollow fiber membrane module of this embodiment.

The hollow fiber membrane module shown in FIG.
a pressure vessel 1;
Two hollow fiber membrane elements 4 disposed in a pressure vessel 1;
and water collecting caps 31 and 32 fixed liquid-tightly to the outer peripheral surfaces of the ends of the two hollow fiber membrane elements 4.
The two hollow fiber membrane elements 4 are connected in series within the pressure vessel 1 .

(Pressure vessel)
The pressure vessel 1 includes a feed solution (FS) supply port 10a and a FS (concentrated FS: concentrate) discharge port 10b provided at both longitudinal ends, and also includes a draw solution (DS) supply port 11a and a DS (diluted DS: diluent) discharge port 11b provided at both longitudinal end sides.

1, the supply port 10a and the discharge port 10b are provided in a wall member 13 that constitutes the pressure vessel 1. The supply port 11a and the discharge port 11b are provided in the side surface of the pressure vessel 1.
In FIG. 1, two hollow fiber membrane elements 4 are arranged in series between two wall members 13 and 14 .

(Hollow fiber membrane element)
Each hollow fiber membrane element 4 has:
A plurality of hollow fiber membranes;
and a double core tube 2 provided in the longitudinal direction of the hollow fiber membrane element 4.

The double core pipe 2 has a porous distribution pipe 21 and an inner pipe 22 disposed inside the porous distribution pipe 21 .
An outer flow passage 21a formed by the inner wall of the perforated distribution pipe 21 and the outer wall of the inner pipe 22 communicates with the supply port 11a and the discharge port 11b.

The perforated distribution pipe 21 is a tubular body with multiple holes (not shown). For example, the perforated distribution pipe 21 distributes the draw solution supplied from the supply port 11a into the hollow fiber membrane module to the outside of the hollow fiber membranes via the outer flow path 21a and the multiple holes. It is preferable that the multiple holes in the perforated distribution pipe 21 be arranged radially in each direction.

The inner pipe 22 is a pipe installed inside the perforated distribution pipe 21 in the longitudinal direction of the hollow fiber membrane element 4. The inner flow path 22a formed by the inner wall of the inner pipe 22 is connected to the discharge port 10b.

The plurality of hollow fiber membranes are arranged around a double-core tube 2 disposed within a hollow fiber membrane element 4. The perforated distribution tube 21 and the plurality of hollow fiber membranes are fixed to each other at both ends by resin 7.
The interior (hollow portion) of each of the plurality of hollow fiber membranes communicates with the supply port 10a on the upstream side and with the inner flow path 22a on the downstream side.

The term "feed solution" refers to the liquid to be treated in membrane processes such as forward osmosis. It is not particularly limited as long as it contains water and components other than water, and may be either a solution or a suspension. Examples of feed solutions include seawater, brackish water, river water, lake water, industrial wastewater, and domestic wastewater.

The draw solution (DS) is a liquid containing a solute and is not particularly limited as long as it has a higher osmotic pressure than the feed solution. Examples include inorganic salt solutions, sugar solutions, and liquids containing gases with high solubility in water (such as ammonia or carbon dioxide), organic substances, magnetic fine particles, or organic polymers. The draw solution may also contain undissolved components.

(Water collection cap)
The water collecting caps 31 and 32 are fixed to the outer peripheral surfaces of the ends of the hollow fiber membrane element 4 in a liquid-tight manner.

It is preferable that grooves 31b, 32b for O-rings are provided on the inner surfaces of the water collection caps 31, 32, and O-rings are placed in the grooves 31b, 32b, so that the water collection caps are fixed liquid-tightly to the outer surface of the end of the hollow fiber membrane element (the outer surface of the outer ring 41 provided at the end of the hollow fiber membrane element 4).
The outer ring is an annular member formed on the outer periphery of the end of the hollow fiber membrane element, and multiple hollow fiber membranes are sealed and fixed inside it (see Patent Document 2). As the O-ring, O-rings made of various known rubber materials can be used.

Typically, hollow fiber membrane elements have a cylindrical shape and the outer ring has an annular shape. Therefore, by providing a groove for an O-ring on the inner surface of the water collection cap and placing the O-ring in the groove, it is easy to liquid-tightly secure the water collection cap to the outer surface of the end of the hollow fiber membrane element (the outer surface of the outer ring 41).

Similar to conventional water collection plates (e.g., the permeate fluid collection members of Patent Documents 1 and 2), the water collection cap has a common flow path that communicates with the hollow portions of multiple hollow fiber membranes. Therefore, for example, FS supplied from supply port 10a can be simultaneously supplied into the hollow portions of multiple hollow fiber membranes via holes 311 in water collection cap 31, or FS within the hollow portions of multiple hollow fiber membranes can be collected and passed through water collection cap 32 and flow paths 6b and 6a in connector 6 to inner flow path 22a.

The hole 312 of the water collecting cap 31 communicates with the inner flow path 22a of the hollow fiber membrane element 4. The hole 313 of the water collecting cap 31 communicates with the outer flow path 21a of the hollow fiber membrane element 4.
The central portion of the connector 6 is fitted into the hole 321 of the water collecting cap 32 , and the flow path 6 c of the connector 6 communicates with the outer flow paths 21 a of the two hollow fiber membrane elements 4 .

Furthermore, in this embodiment, the water collecting caps 31, 32 have a cap-like shape and an inner diameter that is approximately the same as or slightly larger than the outer diameter of the hollow fiber membrane element 4, so that they can be fitted over the end portions, including the outer rings, of the hollow fiber membrane element 4. Then, O-rings provided on the inner peripheral surfaces of the water collecting caps 31, 32 allow the water collecting caps 31, 32 to be fixed liquid-tightly to the outer peripheral surfaces of the end portions of the hollow fiber membrane element 4.
Therefore, referring mainly to Figure 2, even if the pressure inside the hollow portion becomes higher than that outside the hollow fiber membrane, causing the water collection caps 31, 32 to separate from the ends of the hollow fiber membrane element 4 and creating a certain amount of gap between them, the seal provided by the O-rings provided in the grooves 31b, 32b on the inner surfaces of the water collection caps 31, 32 is maintained, and the hollow portion of the hollow fiber membrane and the outside are maintained in a liquid-tight separation state.

Therefore, in addition to the functions of a conventional water collection plate and snap, the water collection cap of this embodiment can also prevent leakage of DS or FS.

The water collection cap 32 used between two hollow fiber membrane elements 4 (connection portion) and the water collection cap 31 used on the discharge port 11b side (outlet side) of the DS preferably have recesses 31c, 32c on their outer surfaces extending in the longitudinal direction of the pressure vessel (see Figures 4 to 6). The recesses 31c, 32c of the water collection caps 31, 32 allow flow path 1a to be formed inside the inner wall of the pressure vessel 1, which communicates with the outside of the hollow fiber membranes of two adjacent hollow fiber membrane elements 4, and also allow flow path 1b to be formed, which communicates with the outside of the hollow membranes of the hollow fiber membrane elements 4 and the discharge port 11b. This makes it easy to ensure a flow path communicating with the outside of the hollow membranes of the hollow fiber membrane elements 4 within the hollow fiber membrane module.

In this embodiment, by fixing the water collection caps 31, 32 liquid-tightly to the outer peripheral surface of the end of the hollow fiber membrane element, it is not necessary to fix the hollow fiber membrane element 4 by sealing the gap between the hollow fiber membrane element 4 and the pressure vessel 1 with an O-ring or the like, and therefore it is possible to provide such flow paths 1a, 1b. In other words, as shown in Figure 10, if the hollow fiber membrane element 4 is fixed to the inner peripheral surface of the pressure vessel 1 in a sealed state with an O-ring 8, it is not possible to provide a flow path between the pressure vessel 1 and the hollow fiber membrane element 4.

In the hollow fiber membrane module shown in Figure 1, etc., the water collection cap 31 used on the supply port 11a side (inlet side) does not have a recess 31c. An O-ring is installed in the groove 31a on the outer surface of the water collection cap 31 used on the supply port 11a side (inlet side), sealing the outer wall of the water collection cap 31 and the inner wall of the pressure vessel 1. However, depending on the structure of the inlet side of the hollow fiber membrane module, a recess 31c may be provided.

The materials for forming the water collecting caps 31, 32, the connector 6 and the outer ring 41 are not particularly limited, but for example, a resin material is preferably used.
Examples of resin materials include polyphenylene sulfide (PPS), polyphenylene ether (PPE), polyacetal (POM), polyvinyl chloride (PVC), polyether ether ketone (PEEK), acrylonitrile butadiene styrene (ABS) resin, and fiber reinforced plastic (FRP).

Referring to Figure 8, the outer ring 42 (Figure 8(a)) used in conventional hollow fiber membrane modules has notches for snaps or O-rings. Because the strength of such outer rings 42 is weakened at the notches, the outer ring 42 had to be thickened. In contrast, the outer ring 41 (Figure 8(b)) used in this embodiment is flat, eliminating the need for notches, and therefore can be thinner than the conventional notched outer ring 42. By reducing the thickness of the outer ring 41, the inner diameter D2 of the outer ring 41 can be larger than the inner diameter D1 of the conventional outer ring 42, even with the same outer diameter. This increases the packing amount (number) of hollow fiber membranes per hollow fiber membrane module and the total membrane area of the hollow fiber membranes, thereby improving the efficiency of membrane processing.

(Overall configuration of hollow fiber membrane module, etc.)
In this embodiment, the hollow fiber membrane module is preferably used for forward osmosis (FO) treatment. As described above, when the pressure inside and outside the hollow fiber membrane is approximately the same, as in FO treatment, leakage of the draw solution (DS) or feed solution (FS) may occur. Therefore, the hollow fiber membrane module of this embodiment, which can prevent leakage of the DS or FS, is useful.

1, the draw solution (DS) is supplied from the supply port 11a, passes through the outer flow path 21a of the perforated distribution pipe 21, and is supplied to the outside of the hollow fiber membranes through the multiple holes in the perforated distribution pipe 21. The DS flows outside the hollow fiber membranes toward the outside in the radial direction of the hollow fiber membrane element 4 and passes through the flow paths 1a and 1b, and is discharged from the discharge port 11b.
Furthermore, some of the DS passes through the flow path 6c (see FIG. 7) of the connector 6 from the outer flow path 21a on the supply port 11a side (inlet side) and is supplied to the outer flow path 21a on the discharge port 11b side (outlet side), and is supplied to the outside of the hollow fiber membranes of the outlet-side hollow fiber membrane element 4. The DS that passes by flowing outside the hollow fiber membranes of the outlet-side hollow fiber membrane element 4 to the outside in the radial direction of the hollow fiber membrane element 4 is discharged from the discharge port 11b via flow path 1b.
Although FIG. 7 shows a connector 6 having two flow paths 6c, the number of flow paths 6c may be three or more (for example, four) and is not particularly limited.

On the other hand, a feed solution (FS) is supplied from the supply port 10a and flows out from the open end of the hollow fiber membrane into the interior (hollow portion) of the hollow fiber membrane. The FS then flows into the inner flow path 22a of the inner tube 22 via the flow paths 6a and 6b (branch flow paths) of the connector 6 (see Figure 7). The FS in the inner flow path 22a is then discharged from the discharge port 10b.
1 is a diagram showing the connector 6 in a schematic manner, and is not an accurate cross-sectional view of the connector 6 shown in FIG.

In Figure 1, the supply port 10a and the discharge port 10b are provided at both longitudinal ends of the hollow fiber membrane element 4, but this is not limited to this configuration. Also, in Figure 1, the supply port 10a and the discharge port 10b are provided on the end face of the pressure vessel 1, but this is not limited to this configuration and they may be provided on the outer peripheral surface of the pressure vessel 1, for example.

In addition, in Figure 1, the supply port 11a and the discharge port 11b are provided on the outer peripheral surface of the pressure vessel 1, but this is not limited to this configuration and may be provided, for example, on the end surface of the pressure vessel 1.

Examples of the semipermeable membrane constituting the hollow fiber membrane used in this embodiment include semipermeable membranes known as reverse osmosis membranes (RO membranes), forward osmosis membranes (FO membranes), nanofiltration membranes (NF membranes), and ultrafiltration membranes (UF membranes). Semipermeable membranes are preferably reverse osmosis membranes, forward osmosis membranes, or nanofiltration membranes. When using reverse osmosis membranes, forward osmosis membranes, or nanofiltration membranes as semipermeable membranes, the pressure of the feed solution is preferably 0.1 to 10.0 MPa, and more preferably 0.5 to 9.0 MPa.

Typically, RO and FO membranes have pore sizes of approximately 2 nm or less, while UF membranes have pore sizes of approximately 2 to 100 nm. NF membranes have a relatively low rejection rate for ions and salts compared to RO membranes, and typically have pore sizes of approximately 1 to 2 nm. When using RO, FO, or NF membranes as semipermeable membranes, the salt rejection rate of the RO, FO, or NF membrane is preferably 90% or higher.

The material that constitutes the semipermeable membrane is not particularly limited, but examples include cellulose-based resin, polysulfone-based resin, polyamide-based resin, and polyvinyl alcohol-based resin. It is preferable that the semipermeable membrane be made of a material that contains at least one of a cellulose-based resin and a polyvinyl alcohol-based resin.

The cellulose-based resin is preferably a cellulose acetate-based resin. Cellulose acetate-based resins are resistant to chlorine, a disinfectant, and have the ability to inhibit the growth of microorganisms. The cellulose acetate-based resin is preferably cellulose acetate, and from the standpoint of durability, cellulose triacetate is more preferred.

The polyvinyl alcohol resin is preferably a cross-linked polyvinyl alcohol resin.

Hollow fiber membranes include single-layer and composite membranes made of the same or different materials. The membrane structure may be heterogeneous (asymmetric) with a dense layer near the membrane surface, or homogeneous with high structural uniformity across the membrane thickness. For example, the former structure is preferred when used for forward osmosis. Specifically, it is preferable to use a membrane with a thin and dense dense layer (separation active layer) to enhance salt separation and to increase asymmetry so as to reduce concentration polarization in the support layer.

The diameter of the hollow fiber membrane is not particularly limited as long as it is suitable for use in membrane processes such as reverse osmosis and forward osmosis. For example, the inner diameter is 50 to 1,000 μm, and the outer diameter is 100 to 1,500 μm. However, in this embodiment, hollow fiber membranes also include semipermeable membranes in the shape of hollow fibers (sometimes called tubular shapes) with a relatively large inner diameter of 1 mm or more.

The hollow fiber membrane's hollowness is not particularly limited as long as it is suitable for use in membrane processes such as reverse osmosis and forward osmosis, but is, for example, 15 to 65%. If the hollowness is less than this range, the flow pressure loss in the hollow portion increases, and the desired amount of permeated water may not be obtained. If the hollowness is greater than this range, sufficient pressure resistance may not be ensured during the osmosis process. The hollowness (%) can be calculated using the formula: [hollowness (%) = (inner diameter/outer diameter) ² × 100].

Hollow fiber membrane elements have a larger membrane area per element than spiral elements using spiral-wound flat membranes. For this reason, hollow fiber membranes require a significantly smaller throughput per unit membrane area to achieve the same water permeation rate, and compared to spiral elements, they can reduce membrane surface fouling caused by feed solution and extend the operating time before membrane cleaning. Furthermore, they are less likely to experience drift within the module, which is advantageous in that they can increase permeation efficiency.

The multiple hollow fiber membranes are preferably a hollow fiber membrane roll formed by spirally winding a hollow fiber membrane or a bundle of hollow fiber membranes around a core tube, thereby stacking the hollow fiber membranes radially. In a hollow fiber membrane roll, the hollow fiber membranes may be arranged in a crossing pattern. Generally, a crossing pattern results in regular voids being formed at the intersections of the hollow fiber membranes. The presence of these regular voids reduces the likelihood of undissolved components or particulate components in the fluid flowing outside the hollow fiber membranes being trapped between the hollow fiber membranes, reducing the likelihood of increased pressure loss.

Wound hollow fiber membrane bodies can be manufactured using conventional methods. For example, as described in Japanese Patent Publication Nos. 4412486, 4277147, 3591618, and 3008886, 45 to 90 or more hollow fiber membranes are assembled into a single hollow fiber membrane assembly, and then multiple hollow fiber membrane assemblies are arranged horizontally to form a flat hollow fiber membrane bundle, which is then wound around a perforated distribution pipe while traversing it. By adjusting the length and rotation speed of the perforated distribution pipe and the traverse speed of the hollow fiber membrane bundle, the wound body is wound up so that an intersection is formed on the circumferential surface at a specific position.

The hollow fiber membrane element 4 can also be manufactured by, for example, restraining both ends of the hollow fiber membrane and core tube with an outer ring, sealing them with resin, and then cutting part of the resin to open both ends of the hollow fiber membrane. For example, the length and position of the intersection of the above-mentioned hollow fiber membrane roll can be adjusted, cut at a predetermined position, and the ends of the roll can be glued together, followed by cutting both sides to produce a hollow fiber membrane element with openings on both ends of the hollow fiber membrane.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

Example 1
As the hollow fiber membrane module of Example 1, a hollow fiber membrane module containing two hollow fiber membrane elements (prototype FO elements made of cellulose triacetate, manufactured by Toyobo Co., Ltd.) similar to the embodiment shown in Fig. 1 etc. was prepared. Details of the hollow fiber membrane elements are as follows.
Element outer diameter: 10 inches Hollow fiber outer diameter: 230 μm
Hollow fiber inner diameter: 140 μm
Element total length: 1310 mm
Element effective length: 1150 mm
Effective membrane area (based on hollow fiber outer diameter): 550 ^m2
Filling rate of hollow fiber membrane: 55%
The filling rate of the hollow fiber membrane was calculated using the following formula.
Filling rate (%) = π × (outer diameter of hollow fiber membrane) ² /4 (m ² ) × total length of hollow fiber membrane (m) / volume of hollow fiber membrane roll (m ³ ) × 100%

(Comparative Example 1)
A hollow fiber membrane module containing two hollow fiber membrane elements (prototype FO elements made of cellulose triacetate, manufactured by Toyobo Co., Ltd.) was prepared as the hollow fiber membrane module of Comparative Example 1. As shown in Figure 9 etc., the hollow fiber membrane module of Comparative Example 1 differs from the hollow fiber membrane module of Example 1 in that the water collecting plates 33, 34 and the hollow fiber membrane element 4 are fixed with snaps 5. In other respects, it is the same as Example 1.

<Evaluation test>
The hollow fiber membrane modules of Example 1 and Comparative Example 1 were subjected to forward osmosis treatment under the following conditions.
FS supplied to the hollow part of the hollow fiber membrane: 3.5% NaCl solution FS inlet flow rate: 15 L/min FS inlet temperature: 30°C
DS supplied to the outside of the hollow fiber membrane: 75 wt% (ADEKA Pluronic (registered trademark) 17R-4, ADEKA Corporation)
DS inlet flow rate: 10 L/min DS inlet temperature: 30°C

10 minutes after the start of forward osmosis treatment, FO performance was measured and a concentrated FS sample was taken. Without diluting the concentrated FS sample, TOC (total organic carbon) was measured according to JIS K 0102, Section 22.2 (Combustion Oxidation - Infrared Automatic Measurement Method). This determined the amount of solute in DS that leaked into the FS, and the DS-BF ratio (ratio of DS leakage to DS flow rate) per membrane area was calculated from the obtained TOC measurement value. The results are shown in Table 1.

The results shown in Table 1 show that the DS-BF ratio per membrane area is significantly lower in Example 1 than in Comparative Example 1. This shows that the hollow fiber membrane module of Example 1 suppresses DS leakage compared to Comparative Example 1.

The embodiments and examples disclosed herein should be considered in all respects as illustrative and not restrictive. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

1 Pressure vessel, 1a Flow path, 10a Supply port, 10b Discharge port, 11a Supply port, 11b Discharge port, 13, 14 Wall member, 2 Double core pipe, 21 Perforated distribution pipe, 21a Outer flow path, 22 Inner pipe, 22a Inner flow path, 31, 32 Water collection cap, 31a, 31b, 32a, 32b Groove, 31c, 32c Recess, 311, 312, 313, 321 Hole, 4 Hollow fiber membrane element, 41, 42 Outer ring, 5 Snap, 6 Connector, 6a, 6b, 6c Flow path, 7 Resin, 8 O-ring.

Claims (6)

A pressure vessel;
at least one hollow fiber membrane element disposed in the pressure vessel;
a water collecting cap fixed liquid-tightly to the outer peripheral surface of the end of the hollow fiber membrane element;
Equipped with
the pressure vessel includes a feed solution inlet port, a feed solution outlet port, a draw solution inlet port, and a draw solution outlet port;
a groove for an O-ring is provided on the inner peripheral surface of the water collecting cap, and an O-ring is placed in the groove, thereby liquid-tightly fixing the water collecting cap to the outer peripheral surface of the end of the hollow fiber membrane element . 2. The hollow fiber membrane module according to claim 1 , wherein the water collecting cap is fixed in a liquid-tight manner to the outer peripheral surface of an outer ring provided at the end of the hollow fiber membrane element. The hollow fiber membrane module according to claim 1 or 2 , which is used for forward osmosis treatment. The hollow fiber membrane module according to any one of claims 1 to 3 , wherein the water collecting cap has a groove on its outer peripheral surface that extends in the longitudinal direction of the pressure vessel. the at least one hollow fiber membrane element is a plurality of hollow fiber membrane elements,
The hollow fiber membrane module according to claim 4 , wherein the plurality of hollow fiber membrane elements are connected in series within the pressure vessel. The hollow fiber membrane module according to claim 4 or 5 , wherein the grooves of the water collecting caps form flow paths that communicate with the outside of the hollow fiber membranes of two adjacent hollow fiber membrane modules.