JP2011143347A - Hollow fiber membrane module for moisture exchange - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hollow fiber membrane module for moisture exchanges fully humidifiable of a dried and unused gas and performing the humidification operation of a fuel battery for a long period of time thanks to the improvement of durability. <P>SOLUTION: The hollow fiber member module for moisture exchanges includes a cylindrical outer case, a cylindrical inner case coaxially enclosed with the outer case, a plurality of hollow fiber membranes that are extended in the axial direction in a spacing between the outer and the inner cases and are filled, a first potting section that seals the spacing by fixing a plurality of the hollow fiber membranes at both ends of the cylindrical structure that are in the spacing, introducing inlets that are provided at any of the internal or the outer case, discharge ports that are provided at the other ends of the outer or the inner case, a first fluid route leading to the other ends through the interiors of the hollow fibers in the hollow fiber membranes from one ends of the hollow fiber membranes, and a second fluid route leading to the discharge ports through the insides of the spacing and the outside of the hollow fiber membranes from the introducing inlets, and further includes a second potting section that is provided also at one end on a side opposed to a side on which the introducing inlets or the discharge ports are provided in the inner spacing of the inner case and the cylindrical structure of the inner case. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a moisture exchange hollow fiber membrane module suitable for use in, for example, a fuel cell system, and more particularly to a technique for improving the durability of the module.

  As a fuel cell, a stacked body in which separators are stacked on both sides of a flat membrane electrode assembly (MEA) is used as a unit cell, and a fuel cell stack is formed by stacking several unit cells, for example, several hundred layers. A fuel cell configured as is known. The membrane electrode structure has a three-layer structure in which an electrolyte membrane made of an ion exchange resin or the like is sandwiched between a pair of electrodes constituting a positive electrode (air electrode, cathode) and a negative electrode (fuel electrode, anode). According to such a fuel cell, for example, when a fuel gas is caused to flow through a gas passage facing the gas diffusion electrode on the fuel electrode side and an oxidant gas is caused to flow through a gas passage facing the gas diffusion electrode on the air electrode side, A chemical reaction occurs, generating electricity.

  Here, in order to stabilize the electrochemical reaction as described above, it is desirable that the membrane electrode structure is wet. For example, Patent Document 1 discloses that an anode exhaust gas after use in which the partial pressure of water vapor is increased by adding power generation generated water as water vapor to the fuel gas in the fuel gas flow path is used as a humidified gas, and unused fuel. A fuel cell system for humidifying gas is disclosed.

  By the way, in recent years, the membrane electrode structure tends to become thinner as the performance of the fuel cell becomes higher, and the phenomenon that the water generated by the electrochemical reaction and coming out to the air electrode side moves to the fuel electrode side seems to occur. It has become. For this reason, when the fuel gas is humidified, a wet state of the fuel electrode becomes excessive, and a phenomenon called flooding occurs in which contact between the fuel and the fuel electrode is hindered. On the other hand, on the air electrode side, it is known that there are cases in which the electrochemical reaction is not so hindered even when the degree of wetting is excessive. Therefore, recently, a technique for humidifying the oxidant gas rather than humidifying the fuel gas has been emphasized.

  As a conventional automobile fuel cell system for humidifying oxidant gas, for example, Patent Document 2 supplies dry unused oxidant gas to one space of a humidifier partitioned by a water vapor permeable membrane, A technique is disclosed in which exhausted oxidant gas (off-gas) after being used is supplied to the space of the water to move moisture from the off-gas to the oxidant gas via a water vapor permeable membrane.

  However, in the above technique, since the moisture is moved by contacting the gas from both sides through the substantially planar water vapor permeable membrane, the contact area is small, and the moisture is moved with respect to the continuously supplied oxidant gas. There was a problem that the humidification efficiency was not sufficient in time.

  For such a problem, for example, Patent Documents 3 and 4 describe that after filling a hollow fiber membrane in a humidifier, an unused oxidant gas is circulated inside the hollow of the hollow fiber membrane. A technique is disclosed in which off-gas is circulated so as to be in contact with the outer wall of the hollow fiber membrane and moisture is transferred through the hollow fiber membrane. According to these techniques, a large number of fine hollow fiber membranes are filled in the humidifier, and the membrane area is widened as a whole. Therefore, the contact area for performing water movement is remarkably increased. The humidification efficiency is improved compared to the technique described in.

Japanese Utility Model Publication No. 61-3671 JP-A-6-132038 JP-A-8-273687 Japanese Patent Application No. 2002-147802

  However, in the above-described conventional technology, for example, as shown in FIG. 2, a large number of hollow fiber membranes 11 are filled in the space between the outer case 10 and the inner case 15, and the fuel cell is started and stopped. Thus, a temperature difference is generated in this space, and in particular, a stress indicated by an arrow 50 is generated in the inner case 15. Similarly, a stress indicated by an arrow 51 is also generated in the potting portion 14 sealing the outer case 10 and the inner case 15. When these stresses are repeatedly generated, there is a problem that a crack occurs between the inner case 15 and the potting portion 14 around the interface 14a.

  Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and of course, it is possible to sufficiently humidify the dry unused fuel cell gas supplied into the hollow fiber membrane. An object of the present invention is to provide a moisture exchange hollow fiber membrane module that suppresses breakage of the inner case and the potting portion, improves durability, and enables humidification operation of the fuel cell over a long period of time.

  The moisture exchange hollow fiber membrane module of the present invention extends in the axial direction into a space between the cylindrical outer case, the cylindrical inner case enclosed coaxially with the outer case, and the outer case and the inner case. A plurality of hollow fiber membranes filled with a first potting portion which is a space between the outer case and the inner case and which fixes the plurality of hollow fiber membranes at both ends of the cylindrical structure to seal the space; An inlet port provided in one of the case or the outer case, a discharge port provided in the other of the outer case or the inner case, and from the one end side of the hollow fiber membrane to the other end side through the hollow interior of the hollow fiber membrane A first fluid path extending from the introduction port to the discharge port via the outside of the hollow fiber membrane, the inner space of the inner case, and the inner fluid path. In the cylindrical structure of the case, To the side where the outlet is provided it is characterized in that the second potting portion to the opposite side end is provided.

  In the moisture exchange hollow fiber membrane module having the above-described configuration, a dry unused gas (oxidant gas or fuel gas) for fuel cells, for example, is circulated through the first fluid path passing through the hollow fiber membrane, For example, the off-gas after use that has been discharged from the fuel cell and wetted through the second fluid path that passes outside the hollow fiber membrane is circulated to move the moisture of the off-gas to the unused gas, so that water can be exchanged efficiently. Of course, in addition to the first potting part between the conventional outer case and the inner case, the second potting part is also provided inside the inner case, so the rigidity of the inner case is improved. Even if stress is repeatedly generated in the inner case and the potting part by repeating the start and stop of the fuel cell operation, the deformation of the inner case is suppressed and the inner case and the potting part are broken. It is possible to suppress.

  In the present invention, it is preferable that the inner case is provided with at least one hole formed adjacent to the second potting portion and formed in the radial direction of the cylindrical structure. According to this aspect, since a temperature difference is suppressed from occurring inside and outside the inner case through the hole, it is possible to further alleviate stress generation on the inner case and the potting portion.

  In the present invention, it is preferable that at least one of the holes has a vertical opening direction. According to this aspect, since the hole is formed in the vertical direction, even if condensed water is generated in the outer case or the inner case, the condensed water is prevented from collecting by being discharged vertically downward. Further, a local temperature difference is further suppressed.

  According to the present invention, the rigidity of the inner case is improved and the occurrence of a temperature difference in the case is suppressed. Thereby, even if stress is repeatedly generated in the inner case and the potting portion by repeating the start and stop of the operation of the fuel cell, the deformation of the inner case is suppressed, and the breakage of the inner case and the potting portion can be suppressed. As a result, the durability of the moisture exchange hollow fiber membrane module can be improved.

It is a see-through | perspective perspective view which shows the conventional hollow fiber membrane module for a water exchange. It is a sectional side view which shows the hollow fiber membrane module for water exchange of FIG. FIG. 3 is a partial perspective view showing a moisture exchange hollow fiber membrane module as seen from direction A in FIG. 2. It is a see-through | perspective perspective view which shows the hollow fiber membrane module for water exchange of this invention. It is a sectional side view which shows the hollow fiber membrane module for water exchange of FIG. FIG. 6 is a partial perspective view showing the water exchange hollow fiber membrane module as seen from direction B in FIG. 5.

  Embodiments of the present invention will be described below with reference to the drawings. First, prior to the description of the embodiment, a general configuration and problems of a moisture exchange hollow fiber membrane module according to the prior art will be described with reference to FIGS. As shown in FIGS. 1 to 3, the hollow fiber membrane module for moisture exchange has an outer case 10 formed in a cylindrical shape, and an inner case 15 is coaxial with the outer case 10 in the outer case 10. Has been placed.

  In a space inside the outer case 10 and outside the inner case 15 (hereinafter sometimes referred to as a filling space), a plurality of hollow fiber membranes 11 are arranged in the axial direction of the outer case 10 and the inner case 15. Filled in parallel. Since the plurality of hollow fiber membranes 11 expand upon moisture absorption, the hollow fiber membranes 11 are filled through a predetermined interval in order to absorb the dimensional change.

  Both ends of the hollow fiber membrane 11 are fixed to the outer case 10 and the inner case 10 by potting portions 14. In FIG. 1, the hollow fiber membrane 11 is partially omitted, but the hollow fiber membrane 11 extends between the potting portions 14 at both ends. The potting portion 14 is formed by embedding the outside of the hollow fiber membrane 11 in the filling space with a synthetic resin or the like, and seals only the filling space with respect to the outside. Therefore, the hollow interior of the hollow fiber membrane 11 is not sealed, and both ends of the hollow fiber membrane 11 communicate with the outside. In the present embodiment, a path from the one end side (arrow 20) of the hollow fiber membrane 11 to the other end side (arrow 21) via the hollow interior of the hollow fiber membrane is defined as a first fluid path.

  The inner case 15 is provided with a gas inlet 12, and a gas outlet 13 is provided in the outer case 10 which is downstream of the inlet 12 and faces the outer case 10. In the present embodiment, a path from the inlet 12 (arrow 22) in the filling space to the outlet 13 (arrow 23) via the outside of the hollow fiber membrane 11 is defined as a second fluid path.

  In the above moisture exchange hollow fiber membrane module, for example, a dry unused fuel cell gas 20 is introduced into the first fluid path, and an off gas 22 that is an exhaust gas after the gas is used in the fuel cell is used. Since it is introduced into the second fluid path, the dry unused gas 20 passes through the hollow fiber membrane 11, and the wet off-gas 22 after use passes outside the hollow fiber membrane 11 in the filling space. The hollow fiber membrane 11 prevents gas exchange between the inside and the outside, but can move only moisture through the fine holes present on both sides thereof, so that moisture is transferred from the high wet side to the low wet side. In this way, in each of the dry unused gas 20 introduced into the first fluid path and the second fluid path and the wet off-gas 22 after use, moisture moves and the humidified unused gas 21 is used. And it is discharged as off-gas 23 after use with reduced humidity.

  In the conventional moisture exchange hollow fiber membrane module described above, the dried unused gas 20 and the wet off-gas 22 after being used are introduced into the first fluid path and the second fluid path when the fuel cell is started to operate. The temperature of the replacement hollow fiber membrane module rises. In addition, the temperature of the water exchange hollow fiber membrane module decreases due to the shutdown of the fuel cell. As described above, when the fuel cell starts and stops, a temperature difference is generated in the space filled with the hollow fiber membrane, and, for example, as shown in FIG. Similarly, a stress indicated by an arrow 51 is also generated in the potting portion 14 sealing the outer case 10 and the inner case 15. When these stresses are repeatedly generated, the inner case 15 and the potting portion 14 are deformed, and there is a problem that the inner case 15 and the potting portion 14 are broken around the interface 14a.

  4-6 is a figure which shows one Embodiment of the hollow fiber membrane module for water exchange of this invention which can solve the conventional problem mentioned above. In this hollow fiber membrane module for exchanging moisture, description of common components is omitted, and the configuration, operation, and effect unique to the present invention will be described.

  As shown in FIGS. 4 to 6, in the moisture exchange hollow fiber membrane module of the present invention, in addition to the first potting portion 14 provided at the end of the filling space between the outer case 10 and the inner case 15. The second potting part 40 is also provided inside the inner case 15 to seal the inner case 15.

  In this moisture exchange hollow fiber membrane module, even if stresses 50 and 51 are generated in the inner case 15 and the first potting part 14 as shown in FIG. 5, the second potting part 40 is filled in the inner case 15. Therefore, the rigidity of the inner case 15 and the second potting part 40 is improved. Thereby, even if stress is repeatedly generated in the inner case 15 and the first potting part 14 due to a temperature change, these deformations can be suppressed and the interface 14a can be prevented from breaking. Thereby, there exists an effect that the durability of the hollow fiber membrane module for moisture exchange is improved.

  In the moisture exchange hollow fiber membrane module of the present invention, at least one hole portion that connects the filling space and the inner case inner space at a position on the inner case 15 and adjacent to the second potting portion 40 described above. 30 is preferred. If the hole 30 is not provided, water vapor may condense in the filling space and water droplets may adhere, so that a temperature difference occurs between the water droplet portion and other space portions, and the inner case 15 and the potting. Although the stress which generate | occur | produces in the parts 14 and 40 will increase, according to this hole part 30, since the condensed water | moisture content can be discharged | emitted, the temperature difference generate | occur | produced in filling space can be suppressed. Moreover, even when moisture does not condense, the temperature difference between the spaces can be reduced because the two spaces communicate with each other.

  Further, as shown in FIG. 5, the hole portion 30 preferably communicates the filling space and the inner case inner space in the vertical direction. According to such a hole, there is an effect that the condensed water can be quickly discharged vertically downward.

  The method of forming the first potting portion 14 and the second potting portion 40 in the present invention is not particularly limited, and can be formed using any fixing means. In the present embodiment, the hollow space 11 is filled in the filling space with the end portions of the outer case 10 and the inner case 15 upright, the lower end portion is immersed and fixed in resin, and then turned upside down. In the same manner, the other end portion is potted by being dipped in resin and fixed. When potting, the soaked resin seals the inside and outside of the hollow fiber membrane 11, but since the distance between the hollow fiber membranes 11 is smaller than the diameter of the hollow fiber membrane 11, the resin is soaked by capillary action. The height is different and the inside is sealed shallower than the outside of the hollow fiber membrane 11. For this reason, by cutting and removing the outer case 10, the inner case 15 and the hollow fiber membrane 11 together by the immersion depth of potting that seals the inside of the hollow fiber membrane 11, the inside of the hollow fiber membrane 11 is external to the outside of the module. The resin can remain only outside the hollow fiber membrane 11 and the filling space can be sealed. In this way, the first potting portion 14 can be formed.

  After the formation of the first potting portion 14, the second potting portion 40 performs masking so that the resin does not enter the hollow fiber membrane 11, so that the cylindrical structure is immersed again in the resin, and the inside of the inner case 15 It can be formed by sealing only.

  In this embodiment, the expansion coefficient due to the wetness of the hollow fiber membrane 11 is grasped in advance. And, in order to suppress the movement of the hollow fiber membranes 11 when the expansion rate reaches the maximum, the hollow fiber membranes 11 are in close contact with each other so as to be packed densely without gaps, or the gaps are reduced and the density is high. Each is arranged to be filled. On the other hand, in the dry state, the hollow fiber membrane 11 is disposed with a void (gap) between them.

  As the hollow fiber membrane 11 in the present invention, a known hollow fiber membrane can be selected. Specifically, polymers such as phenol sulfonic acid, polystyrene sulfonic acid, polytrifluorostyrene sulfonic acid, perfluorocarbon sulfonic acid, etc. Examples include an ion exchange membrane and a hollow fiber membrane such as a polymer resin or ceramic.

  In the above description, an example has been described in which a dry unused gas is passed through the first fluid path, and a wet off-gas after use is passed through the second fluid path. However, the present invention is limited to this embodiment. Instead, it is also possible to exchange moisture by flowing wet off-gas after use in the first fluid path and flowing dry unused gas in the second fluid path.

  Further, the introduction port 12 provided in the inner case 15 and the discharge port 13 provided in the outer case 10 do not limit the gas flow direction to this direction. And a mode of discharging the gas from the inlet 12 is also included.

  Furthermore, in the above description, the case where the outer case 10 and the inner case 15 are cylindrical has been described as an example. However, the moisture-exchange hollow fiber membrane module of the present invention is not limited to a cylindrical shape, and for example, has a cross section. It can also be a polygonal cylinder.

  According to the present invention, the moisture of the off-gas discharged from the fuel cell can be reused for humidifying the unused oxidant gas, and the durability of the moisture exchange hollow fiber membrane module can be increased for a long time. Since proper humidification of the fuel cell is possible, it is extremely promising when applied to an in-vehicle fuel cell system that requires strict and stable operation.

M ... Hollow fiber membrane module for moisture exchange,
10 ... Outer case,
11 ... Hollow fiber membrane,
12 ... Gas inlet,
13 ... Gas outlet,
14 ... 1st potting part (conventional potting part),
14a ... Interface between inner case and first potting part,
15 ... Inner case,
20 ... Unused gas (low wetness),
21 ... Unused gas (after water exchange),
22: Off-gas after use (high humidity),
23 ... Off-gas after use (after water exchange),
30 ... hole,
40 ... the second potting part,
50 ... Stress (inner case),
51: Stress (potting part).

Claims (3)

A cylindrical outer case,
A cylindrical inner case enclosed coaxially with the outer case;
A plurality of hollow fiber membranes extending in the axial direction and filled in the space between the outer case and the inner case;
A first potting portion which is a space between the outer case and the inner case and which fixes the plurality of hollow fiber membranes at both ends of the cylindrical structure and seals the space;
An inlet provided in one of the inner case or the outer case;
An outlet provided in the other of the outer case or the inner case;
A first fluid path from one end of the hollow fiber membrane to the other end via the hollow interior of the hollow fiber membrane;
A second fluid path from the introduction port in the space and through the outside of the hollow fiber membrane to the discharge port,
In addition, a second potting portion is provided at one end of the inner space of the inner case and opposite to the side where the inlet or the outlet is provided in the cylindrical structure of the inner case. A hollow fiber membrane module for water exchange characterized by the above.   2. The moisture exchange hollow fiber membrane according to claim 1, wherein the inner case includes at least one hole portion adjacent to the second potting portion and formed in a radial direction of the cylindrical structure. module. The hollow fiber membrane module for moisture exchange according to claim 2, wherein the opening direction of at least one of the holes is a vertical direction.

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