JP2007220611A - Humidifier of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a humidifier of a fuel cell capable of realizing further improvement in humidifying performance per volume occupied by a hollow fiber bundle. <P>SOLUTION: The humidifier is provided with a hollow fiber module 6 in which a hollow fiber bundle 4 made by bundling a plurality of hollow fibers 13 is housed in a cylindrical case 5, and an oxidant gas is circulated in a first passage passing inside of the hollow fibers 13 and an exhaust gas is circulated in a second passage circulating from a gas inlet port 7A formed in the case through the outside of the hollow fibers 13 to the outside of the case from a gas exhaust port 7B formed in the wall of the case, and the shape of the end part of the hollow fiber module 6 that is a portion where the flow velocity of the exhaust gas flowing in the hollow fiber module 6 is slow is made a conical recessed part 17 recessed in cone-shape in the central part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell humidifier, and more particularly to a technique for improving humidification efficiency.

  For example, in a fuel cell vehicle, layout requirements are strict as a particular problem, and a humidifier for humidifying an oxidant gas and supplying it to a fuel cell is no exception. In particular, in the humidifier, it is important to improve the humidifying performance per volume occupied by the hollow fiber membrane bundle, and various means have been taken so far for the purpose of improving the humidifying performance. The humidification performance here is defined as the amount of water vapor transferred.

For example, as an example of the means for improving the humidification performance, the material and size of the hollow fiber membrane, the filling rate in the module, etc. are changed, or the shape of the gas introduction part of the module case is small and far from the opening part near the introduction part. For example, a method of enlarging the opening to make the gas flow uniform (see, for example, Patent Document 1).
JP 2002-66265 A

  However, none of the conventional means has sufficient humidification performance per volume occupied by the hollow fiber membrane bundle, and further improvement in humidification performance is required.

  Then, this invention is proposed in view of the above-mentioned actual condition, and it aims at providing the humidification apparatus of the fuel cell which can implement | achieve the further improvement of the humidification performance per volume which a hollow fiber membrane bundle occupies. .

  The applicant of the present application has a large deviation in the flow velocity of the gas flowing through the hollow fiber membrane bundle housed in the housing case in the humidifying device, and the contribution rate (humidification performance) of water vapor exchange is relatively small compared to other parts. As a result of intensive investigation, it was found that the part where the gas flow rate is slow is the end of the hollow fiber membrane module.

  Therefore, in the present invention, the hollow fiber membrane bundle at the end of the hollow fiber membrane module where the gas flow rate is slowed down, and the shape of the end of the hollow fiber membrane module is shaped according to the flow rate distribution of the gas, specifically In this case, the central part is recessed.

  According to the humidifier of the present invention, the end portion of the hollow fiber membrane module is shaped according to the flow velocity distribution of the gas flowing through the hollow fiber membrane bundle housed in the housing case, thereby contributing to water vapor exchange. It is possible to improve the humidification performance per volume occupied by the hollow fiber membrane bundle by eliminating the low rate part.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

“First Embodiment”
FIG. 1 is a block diagram showing an example of a fuel cell humidifier in the first embodiment, FIG. 2 is a longitudinal sectional view of the humidifier shown in FIG. FIG. 4 (A) is an enlarged perspective view of a main part showing an end shape of a hollow fiber membrane bundle housed in a housing case, FIG. 4 (B) is an enlarged perspective view of the main part of the end portion of the hollow fiber membrane in part A in FIG. 3, FIG. 4 (C) is an enlarged perspective view of the main part of the end part of the hollow fiber membrane in part B of FIG. FIG. 6 is a gas flow velocity distribution diagram of a humidifier having a conventional structure.

  In the fuel cell 2 connected to the humidifying device 1 of the present embodiment, an anode to which hydrogen gas is supplied and a cathode to which oxygen-containing air (oxidant gas) is supplied are an electrolyte / electrode catalyst composite (membrane electrode). A power generation cell stacked with a joined body (MEA: membrane electrode assembly) in between is formed into a multi-layered stack structure, and chemical energy is converted into electrical energy by an electrochemical reaction.

  At the anode, the supplied hydrogen dissociates into hydrogen ions and electrons, the hydrogen ions pass through the electrolyte, the electrons pass through an external circuit to generate electric power, and move to the cathode. At the cathode, oxygen in the supplied air reacts with the hydrogen ions and the electrons to generate water, which is discharged to the outside.

  For example, a solid polymer electrolyte is used as the electrolyte of the fuel cell 2 in consideration of high energy density, low cost, light weight, and the like. The solid polymer electrolyte is composed of an ion conductive polymer membrane such as a fluororesin ion exchange membrane, and functions as an ion conductive electrolyte when saturated with water. Therefore, in this fuel cell, water is supplied. It is necessary to humidify the supply gas (oxidant gas).

  As shown in FIG. 1, the humidifier 1 is generally pressurized and heated by an exhaust gas (swelling air) rich in water vapor discharged from the cathode of the fuel cell 2 and a compressor 3 as an air introduction unit. The water permeation type humidifier used in the present invention is a hollow fiber using a hollow fiber membrane as a water permeation membrane. A membrane module (a hollow fiber membrane bundle and a case for housing it) is provided.

  In the water permeable membrane humidifier 1 configured as described above, for example, when wet air containing moisture is supplied into the hollow fiber membrane, moisture is contained in the pores (capillaries) formed in the hollow fiber membrane. Is condensed (capillary condensation) and separated, and moisture permeates from the inside to the outside of the hollow fiber membrane due to the water vapor partial pressure difference with the dry gas (dried oxidant gas) supplied to the outside of the hollow fiber membrane. The permeated moisture is humidified by contacting and evaporating with the dry gas supplied to the outside of the hollow fiber membrane bundle.

  In terms of moisture permeation, water exchange is performed both in the case where wet air is allowed to flow inside the hollow fiber membrane and the dry gas is allowed to flow outside the hollow fiber membrane and vice versa.

  As shown in FIGS. 1 to 4, the humidifier 1 includes a hollow fiber membrane module 6 including a hollow fiber membrane bundle 4 and a housing case 5 that accommodates the hollow fiber membrane bundle 4 therein, and the hollow fiber membrane. It comprises a housing 7 that houses the module 6 therein.

  The hollow fiber membrane bundle 4 is composed of a hollow fiber membrane 9 having an elongated straw shape with a circular cross section formed inside, which has a first flow path 8 serving as a flow passage penetrating in the longitudinal direction. A plurality of pieces are bundled into a cylindrical shape. A dried oxidant gas pressurized and heated by the compressor 3 is introduced into the first flow path 8 formed inside the hollow fiber membrane 9.

  The hollow fiber membrane module 6 is formed as a cylindrical body in which both ends of the hollow fiber membrane bundle 4 having a substantially cylindrical shape are accommodated. The hollow fiber membrane bundle 4 and the housing case 5 are fixed by applying a potting agent 10 (adhesive) to both ends in the longitudinal direction. The potting agent 10 not only joins the hollow fiber membrane 9 and the housing case 5 but also joins the bundled hollow fiber membranes 9 to form a potting portion.

  A plurality of gas introduction holes 11 </ b> A for supplying exhaust gas are formed on the side surface at one end of the hollow fiber membrane module 6 (side surface near one end surface) over the entire circumference. For example, a plurality of gas introduction holes 11A are formed in the circumferential direction at predetermined intervals as circular holes. Similarly, a plurality of gas discharge holes 11B are formed over the entire circumference on the side surface of the other end of the hollow fiber membrane module 6 (side surface near the other end surface), and the gas discharge holes 11B are also circular holes at predetermined intervals. A plurality are formed in the circumferential direction.

  An annular seal member 12 that seals between the housing 7 and the housing case 5 is provided on the case side surface 5 a of the housing case 5. The seal member 12 is provided at a position outside the gas introduction hole 11A and the gas discharge hole 11B and between the gas introduction hole 11A and the gas discharge hole 11B, and is in close contact with an inner wall 7a of the housing 7 described later. Is provided.

  The housing 7 is formed as a cylindrical body large enough to accommodate the hollow fiber membrane module 6 therein. In the housing 7, a second gas introduction pipe 13 for introducing a dry oxidant gas pressurized and heated by the compressor 3 into the inside, and the oxidant gas humidified in the hollow fiber membrane module 6 are supplied to the fuel cell. And a first gas introduction for introducing exhaust gas (wet gas) containing moisture discharged from the fuel cell 2 into the hollow fiber membrane module 6 through the gas introduction hole 11A. A tube 15 and a first gas outlet tube 16 for discharging the exhaust gas supplied into the hollow fiber membrane module 6 to the outside of the case through the gas discharge hole 11B are provided.

  In the hollow fiber membrane module 6, the gas flow path that flows from the gas introduction hole 11 </ b> A to the outside of the case through the gas discharge hole 11 </ b> B through the outside of the hollow fiber membrane 9 accommodated inside the accommodation case 5. A second flow path is formed.

  In the humidifier 1 configured as described above, the dried oxidant gas pressurized and heated by the compressor 3 is introduced into the interior from the second gas introduction pipe 13 provided in the housing 7 and then hollow. It flows through the first flow path 8 formed in each hollow fiber membrane 9 of the yarn membrane module 6. On the other hand, the exhaust gas containing moisture discharged from the cathode of the fuel cell 2 was introduced into the inside from the first gas introduction pipe 15 provided in the housing 7 and then formed on the side surface 5 a of the housing case 5. The gas is supplied from each gas introduction hole 11 </ b> A to the hollow fiber membrane bundle 4.

  The exhaust gas supplied to the hollow fiber membrane bundle 4 flows from the outside of the hollow fiber membrane bundle 4 to the inside thereof, and then is exhausted from each gas discharge hole 11B formed in the case side surface 5a. The gas is discharged out of the case through a first gas outlet pipe 16 provided in the housing 7. When the exhaust gas containing moisture flows inside the hollow fiber membrane bundle 4, the moisture permeates from the outside to the inside of the hollow fiber membrane 9 due to a water vapor partial pressure difference from the dried oxidant gas. Moisture that permeates simultaneously condenses (capillary condensation) in the capillaries (first flow paths 8) formed in each hollow fiber membrane 9, and functions to prevent permeation other than water vapor. As a result, only water vapor moves. The permeated moisture comes into contact with and vaporizes the dried oxidant gas, so that the oxidant gas flowing inside each hollow fiber membrane 9 is humidified. The humidified oxidant gas is supplied to the fuel cell 2 from the discharge side of the hollow fiber membrane module 6.

  The exhaust gas flowing through the hollow fiber membrane module 6 is the hollow fiber membrane module in the case of the comparative example of FIG. 5 (when the end surface of the hollow fiber membrane module 6 is a flat surface perpendicular to the flow direction of the dried oxidant gas). The flow velocity distribution in a cross section passing through the axis 6 is as shown in FIG. In FIG. 6, the flow rate of the exhaust gas is expressed as small, medium, large, maximum, and the flow rate is fast in that order. Moreover, the projection shape to the cross section of 11 A of gas introduction holes and the gas discharge hole 11B is shown with a broken line. From this flow velocity distribution, it can be seen that the substantially central portion of the potting portion at both ends in the longitudinal direction of the hollow fiber membrane module 6 is a portion where the flow velocity of the exhaust gas containing moisture is slow. In the part where the flow rate is slow, the flow rate of the exhaust gas is low and the contribution rate of the water vapor exchange is relatively small.

  Therefore, in the present embodiment, the hollow fiber membrane module 6 has a concave shape such that the end surface enters the other end of the hollow fiber membrane bundle 4, and the depth from the end surface of the hollow fiber membrane module 6 in the concave shape is reduced. The length of the gas flowing in from the gas introduction hole 11A is varied according to the flow velocity distribution in the hollow fiber membrane module 6. In other words, by deepening the concave portion of the hollow fiber membrane bundle 4 at a portion where the flow velocity is small, the region where the contribution rate of water vapor exchange is small is eliminated, and the humidification performance per unit volume (water exchange performance) occupied by the hollow fiber membrane bundle 4 is better. Further improvement is planned. Specifically, as shown in FIG. 3, the shape of the end face of the hollow fiber membrane module 6 is a shape in which the center is dented in a mortar shape. In the present embodiment, by forming the mortar recess 17, there is no region where the contribution rate of water vapor exchange is small, so that the humidification performance per volume occupied by the hollow fiber membrane bundle 4 can be enhanced.

  Moreover, by making the end surface of the hollow fiber membrane module 6 into a mortar shape, the tip opening shape of the hollow fiber membrane 9 other than the hollow fiber membrane 9 in the central portion is inclined (see FIG. 4B), and the first The opening area of the flow path 8 increases. Thereby, the pressure loss in the gas inflow / outflow end part of the hollow fiber membrane bundle 4 is reduced.

  Further, the dried oxidant gas introduced into the housing case 5 from the second gas introduction pipe 13 is once expanded in the air layer 18 formed in front of the gas inflow / outflow end portion of the hollow fiber membrane bundle 4, respectively. The hollow fiber membrane 9 takes a path to flow into the first flow path 8. As the volume (thickness) of the air layer 18 increases, the pressure loss can be reduced, and the dried oxidant gas can be evenly supplied to each hollow fiber membrane 9, leading to improved water exchange performance.

  Therefore, if the recessed part 17 is formed in the edge part of a hollow fiber membrane module like this embodiment, the volume expansion of the air layer 18 can also be achieved simultaneously and the further pressure loss reduction effect can be acquired.

  In the first embodiment described above, a dry oxidant gas is allowed to flow inside the hollow fiber membrane 9 (first flow path 8), and an exhaust gas containing moisture is allowed to flow outside the hollow fiber membrane 9, On the contrary, the exhaust gas containing the moisture discharged from the fuel cell 2 may flow inside the hollow fiber membrane 9 and the dry oxidant gas may flow outside the hollow fiber membrane 9.

  Furthermore, the recessed part 17 can be easily manufactured by scraping off the end surface of the flat hollow fiber membrane module 6 of the comparative example shown in FIG. 5 by machining.

“Second Embodiment”
FIG. 7 is a longitudinal sectional view of the humidifying device of the second embodiment. In the second embodiment, only parts different from the first embodiment will be described, and the description of the same parts as the first embodiment will be omitted.

  In the first embodiment, the gas inflow / outflow end face shape of the hollow fiber membrane bundle 4 is a mortar shape that is dented into a spherical shape. However, in the second embodiment, as shown in FIG. Each of the potting portions has a conical shape recessed inside. By forming the concave portion 19 that is recessed in the conical shape, the humidifying performance per volume occupied by the hollow fiber membrane bundle 4 can be enhanced.

“Third Embodiment”
FIG. 8 is a longitudinal sectional view of the humidifier of the third embodiment, and FIG. 9 is a diagram of the shaft of the hollow fiber membrane module 6 for exhaust gas, the first gas introduction pipe 15 and the first gas outlet pipe 16 in the humidification apparatus shown in FIG. It is a flow velocity distribution figure in the section which passes along an axis. In FIG. 9, the projection shapes on the cross sections of the gas introduction hole 11A and the gas discharge hole 11B are indicated by broken lines. In the third embodiment, only parts different from the first embodiment will be described, and the description of the same parts as the first embodiment will be omitted.

  In the third embodiment, the arrangement of the gas introduction holes 11A and the gas discharge holes 11B and the shape of the end face of the hollow fiber membrane module 6 are different from the first embodiment.

  That is, the gas introduction hole 11 </ b> A formed on the side surface at one end of the hollow fiber membrane module 6 (side surface near one end) faces the first gas introduction tube 15 with the axis of the hollow fiber membrane module 6 interposed therebetween. A plurality of surfaces are formed. A plurality of gas introduction holes 11A are formed on the surface at predetermined intervals, for example, as circular holes. Similarly, the gas discharge hole 11B formed in the other side surface (side surface near the other end) of the hollow fiber membrane module 6 is formed in the first gas outlet pipe 16 with the axis of the hollow fiber membrane module 6 interposed therebetween. A plurality are formed on the opposing surfaces. Similarly, a plurality of gas discharge holes 11B are formed on the surface as circular holes at predetermined intervals.

  Accordingly, the flow rate distribution of the exhaust gas in the third embodiment is as shown in FIG. 9, and the end face shape of the hollow fiber membrane module 6 as shown in FIG. 8 is eliminated so as to eliminate the region where the flow rate is low and the contribution rate of water vapor exchange is small. To do. The end surface 20A of the hollow fiber membrane module 6 on the first gas introduction tube 15 side is a surface that is inclined with respect to the axis of the hollow fiber membrane module 6, and the normal direction toward the outside of the hollow fiber membrane module 6 is the first direction. An obtuse angle is formed with respect to the direction of gas flow through the gas introduction pipe 15. Similarly, the other end surface 20B of the hollow fiber membrane module 6 on the first gas outlet tube 16 side is a surface that is inclined with respect to the axis of the hollow fiber membrane module 6, and is a normal line that faces the outside of the hollow fiber membrane module 6. The direction makes an acute angle with respect to the direction of gas flow through the first gas outlet pipe 16. Therefore, in 3rd Embodiment, since the area | region where the flow rate is slow and there is little contribution rate of water vapor | steam exchange is eliminated, the humidification performance per volume which the hollow fiber membrane bundle 4 occupies can be improved.

  Furthermore, the opening shape of the tip end of the hollow fiber membrane 9 becomes oblique, and the opening area of the first flow path 8 increases. Thereby, the pressure loss in the gas inflow / outflow end part of the hollow fiber membrane bundle 4 is reduced.

  Further, in the third embodiment, the inclined surfaces 20A and 20B can be formed with fewer man-hours than scraping into a concave shape like the concave portions 17 and 19 of the first and second embodiments, and the humidifier 1 is manufactured. Cost reduction can also be realized.

  Although specific embodiments to which the present invention is applied have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.

  The second gas inlet pipe 13 and the second gas outlet pipe 14 may be provided perpendicular to the inclined surfaces 20A and 20B on the end face of the hollow fiber membrane module 6.

  Thus, if the oxidant gas is introduced perpendicularly to the tip opening portion of the hollow fiber membrane 9 that opens obliquely, a greater pressure loss reduction effect can be obtained.

It is a block diagram which shows an example of the humidification apparatus of the fuel cell in 1st Embodiment. It is the longitudinal cross-sectional view of the humidification apparatus which fractured | ruptured the housing part of FIG. 1 and showed the internal storage case. It is a longitudinal cross-sectional view of the humidification apparatus broken and shown to the part by which the hollow fiber membrane bundle of 1st Embodiment is arrange | positioned. FIG. 4A is an enlarged perspective view of the main part showing the end shape of the hollow fiber membrane bundle housed in the housing case, and FIG. A perspective view and FIG.4 (C) are the principal part expansion perspective views of the hollow fiber membrane edge part in B part in FIG. It is a longitudinal cross-sectional view of the humidification apparatus of the comparative example of 1st Embodiment. It is a flow velocity distribution figure of exhaust gas in a humidification device of a comparative example of a 1st embodiment. It is a longitudinal cross-sectional view of the humidification apparatus of 2nd Embodiment. It is a longitudinal cross-sectional view of the humidification apparatus of 3rd Embodiment. FIG. 9 is a flow velocity distribution diagram of exhaust gas in the humidifier shown in FIG. 8.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Humidifying device 2 ... Fuel cell 3 ... Compressor 4 ... Hollow fiber membrane bundle 5 ... Housing case 5a ... Case side surface 5b ... Case inner wall 6 ... Hollow fiber membrane module 7 ... Housing case 8 ... 1st flow path 9 ... Hollow fiber membrane 11A ... Gas inlet hole 11B ... Gas outlet hole 13 ... Second gas inlet pipe 14 ... Second gas outlet pipe 15 ... First gas inlet pipe 16 ... First gas outlet pipe 17, 19 ... Recess 18 ... Air layer 20 ... Inclined surface

Claims (5)

A hollow fiber membrane module containing a hollow fiber membrane bundle formed by bundling a plurality of hollow fiber membranes in a cylindrical case,
In the first flow path passing through the inside of the hollow fiber membrane, either a dry oxidant gas or an exhaust gas containing moisture discharged from the fuel cell is circulated,
From the gas introduction hole formed on the side surface of the hollow fiber membrane module, passes outside the membrane of the hollow fiber membrane, and flows from the gas discharge hole formed on the side surface of the hollow fiber membrane module to the outside of the hollow fiber membrane module. A gas different from the gas flowing through the first channel is circulated through the second channel,
A fuel cell humidifier for humidifying the oxidant gas with the exhaust gas,
When the hollow fiber membrane module includes a plurality of the gas introduction holes over the entire side surface near one end surface, and a plurality of the gas discharge holes over the entire side surface near the other end surface,
At least one of the end surfaces of the hollow fiber membrane bundle has a concave shape so as to enter the other end of the hollow fiber membrane bundle, and the depth of the concave shape from the end surface of the hollow fiber membrane module. The fuel cell humidifying device is characterized in that the gas flowing in from the gas introduction hole is made different according to a flow velocity distribution in the hollow fiber membrane module. A fuel cell humidifier according to claim 1,
The humidifying device for a fuel cell, wherein the concave shape is a mortar shape. A fuel cell humidifier according to claim 1,
The humidifying device for a fuel cell, wherein the concave shape is a conical shape. A hollow fiber membrane module containing a hollow fiber membrane bundle formed by bundling a plurality of hollow fiber membranes in a cylindrical case,
In the first flow path passing through the inside of the hollow fiber membrane, either a dry oxidant gas or an exhaust gas containing moisture discharged from the fuel cell is circulated,
From the gas introduction hole formed on the side surface of the hollow fiber membrane module, passes outside the membrane of the hollow fiber membrane, and flows from the gas discharge hole formed on the side surface of the hollow fiber membrane module to the outside of the hollow fiber membrane module. A gas different from the gas flowing through the first channel is circulated through the second channel,
A fuel cell humidifier for humidifying the oxidant gas with the exhaust gas,
A side surface of the housing that covers the hollow fiber membrane module includes a first gas introduction pipe that supplies gas to the second flow path, and a first gas that discharges gas discharged from the second flow path to the outside from the housing. A gas outlet pipe is provided,
The center of the gas introduction hole is a side surface near one end of the hollow fiber membrane module so as to face the first gas introduction pipe across the axis of the hollow fiber membrane module. A plurality of the gas discharge holes are provided such that the center is a side surface near the other end, and is located at a position facing the first gas outlet pipe across the axis of the hollow fiber membrane module. If
The normal direction of the end surface of the hollow fiber module on the first gas outlet pipe side toward the outside of the hollow fiber module is an acute angle with respect to the gas flow direction of the first gas outlet pipe, or A normal direction of the end face of the hollow fiber module on the side of one gas introduction pipe toward the outside of the hollow fiber module is an obtuse angle with respect to the gas flow direction of the first gas introduction pipe. Humidifier. A humidifying device for a fuel cell according to claim 4,
One end surface of the housing includes a second gas introduction pipe that supplies gas to the first flow path, and the other end surface of the housing allows gas discharged from the first flow path to the outside from the housing. A second gas outlet pipe for discharging,
The second gas introduction pipe is perpendicular to an end surface of the hollow fiber module on the first gas outlet pipe side, or the second gas outlet pipe is on the first gas inlet pipe side. A humidifier for a fuel cell, wherein the humidifier is arranged so as to be perpendicular to an end face of the hollow fiber module.

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