Humidification system and fuel cell system

Abstract

This invention relates to a humidification system and a fuel cell system that can prevent malfunctions in the humidification system and achieve a good supply of cathode gas even when the fuel cell is shut down in a low-temperature environment. [Solution] The humidification system 26 includes a membrane module 40 that moves water vapor from the wet gas to the dry gas between multiple permeable membranes that allow water vapor to pass through, and a drain passage 58 that moves condensed water from the dry gas outlet to the wet gas outlet is formed inside a housing 38 that surrounds the membrane module 40.

Description

[[Technical Field]]

[0001] The present disclosure relates to a humidification system that supplies humidified gas to a fuel cell and a fuel cell system. [[Background Art]]

[0002] In recent years, research and development have been conducted on fuel cells that contribute to energy efficiency, in order to enable more people to secure access to affordable, reliable, sustainable and advanced energy.

[0003] In a fuel cell system, moisture is added to cathode gas through a humidification system (Japanese Patent No. 4418299). [[Prior Art Literature]] [[Patent Literature]]

[0004] [[Patent Document 1]] Japanese Patent No. 4418299 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0005] When a fuel cell system is stopped in a low-temperature environment, frozen water (ice) adheres to key locations inside the humidification system, which may impede the operation of the humidification system during restart.

[0006] To solve the above problem, the present application aims to prevent malfunction of the humidification system and achieve favorable supply of cathode gas even when the fuel cell is stopped in a low-temperature environment, and ultimately contributes to improved energy efficiency. [[Means for Solving the Problem]]

[0007] A first aspect of the present disclosure is a humidification system comprising: a membrane module that imparts moisture from a wet gas to a dry gas through a plurality of permeable membranes that allow water vapor to pass through; a housing that surrounds the membrane module; a dry gas introduction section connected to the housing for introducing the dry gas into the membrane module; a dry gas discharge section connected to the housing for discharging the dry gas from the membrane module; a wet gas introduction section provided in the housing for introducing the wet gas into the membrane module; a wet gas discharge section connected to the housing for discharging the wet gas from the membrane module; and a drain passage that connects the dry gas discharge section and the wet gas discharge section and allows water condensed at the dry gas discharge section to flow to the wet gas discharge section, wherein the drain passage is formed inside the housing.

[0008] A second aspect of the present disclosure is a humidification system comprising: a membrane module that imparts moisture from a wet gas to a dry gas through a plurality of permeable membranes that allow water vapor to pass through; a housing that covers the periphery of the membrane module; a dry gas introduction section connected to a first side surface of the housing for introducing the dry gas into the membrane module; a dry gas discharge section connected to a second side surface of the housing for discharging the dry gas from the membrane module; a wet gas introduction section connected to the upper surface of the housing for introducing the wet gas into the membrane module; a wet gas discharge section connected to the lower surface of the housing for discharging the wet gas from the membrane module; and a first valve connected to the wet gas discharge section, wherein the wet gas discharge section has an inclined flow path that slopes upward as it approaches the second side surface from below the housing, with its upper part overlapping the side surface of the housing; the first valve is connected to the upper end of the inclined flow path, and when viewed from the side, at least a part of the first valve overlaps the second side surface.

[0009] A third aspect of the present disclosure is a fuel cell system comprising a fuel cell stack and a humidification system according to the first or second aspect, wherein the dry gas is a cathode gas supplied to the fuel cell stack and the wet gas is a cathode-off gas discharged from the fuel cell stack. [Effects of the Invention]

[0010] According to the first embodiment, the heat of the dry gas or wet gas passing through the inside of the housing is efficiently transferred to the drain passage, thereby quickly releasing the ice in the drain passage.

[0011] According to the second embodiment, the first valve can be positioned closer to the housing with a large heat capacity, so that the first valve does not cool down easily and freezing of the first valve can be prevented.

[0012] According to the third embodiment, the heat from the cathode-off gas discharged from the fuel cell stack can be used to thaw the orifice or valves, thereby realizing a fuel cell system that can start up smoothly in low-temperature environments. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic diagram of the fuel cell system according to the embodiment. [Figure 2] Figure 2 is a cross-sectional view showing the humidification system from Figure 1, along with the surrounding piping and valves. [Figure 3] Figure 3A is a front view of the housing containing the membrane module, and Figure 3B is a schematic diagram of a portion of the permeable membrane, the first channel, and the second channel included in the membrane module. [Figure 4] Figure 4A is an enlarged cross-sectional view of the drain passage, and Figure 4B is an enlarged cross-sectional view showing a modified example of the drain passage. [Figure 5] Figure 5 is a perspective view showing the opening at the upper end of the drain passage in the housing. [Figure 6]Figure 6 is an enlarged cross-sectional view of the connection between the dry gas inlet and the housing. [Modes for carrying out the invention]

[0014] The fuel cell system 10 of this embodiment, shown in Figure 1, includes a fuel cell stack 12 that generates electricity using atmospheric air as the cathode gas and hydrogen gas as the anode gas. The fuel cell system 10 is used, for example, to supply power for driving transportation equipment such as passenger cars, trucks, ships, and aircraft, or construction work equipment. The fuel cell system 10 can also be used as a stationary power supply for facilities that use electricity, such as data centers.

[0015] The fuel cell stack 12 contains multiple power generation cells. Each power generation cell includes a polymer electrolyte membrane (MEA) sandwiched between an anode and a cathode, and a pair of separators that sandwich the MEA. Hydrogen is supplied to the anode of each power generation cell as the anode gas, and air is supplied to the cathode as the cathode gas.

[0016] The fuel cell system 10 includes an anode supply channel 14 for supplying anode gas to the anodes of the power generation cells of the fuel cell stack 12, an anode discharge channel 16 for discharging anode off-gas from the anodes, and an anode auxiliary system for supplying anode gas. In this specification, the illustration and description of the anode auxiliary system are omitted.

[0017] A fuel cell system 10 comprises: a cathode supply flow path 18 that supplies cathode gas to the cathodes of power generation cells of a fuel cell stack 12; a cathode discharge flow path 20 that discharges cathode off-gas from the cathodes; and a cathode auxiliary system 22. The cathode off-gas contains dry gas (air) that has not been used for reaction in the fuel cell and water vapor generated by the reaction between hydrogen and oxygen, and contains a relatively large amount of moisture. Since cathode gas has relatively less moisture compared to cathode off-gas, it is also referred to as dry gas in the following description. In addition, cathode off-gas is also referred to as wet gas in the following description.

[0018] The cathode auxiliary system 22 comprises a dry gas preparation unit 24 and a humidification system 26. The dry gas preparation unit 24 includes a compressor that pressurizes dry gas such as air, and a cooler that cools the dry gas heated by pressurization. The pressurized dry gas flows into the humidification system 26 through the cathode supply flow path 18. The humidification system 26 is connected to the cathode supply flow path 18 and the cathode discharge flow path 20, and humidifies the dry gas by supplying water vapor contained in the wet gas to the dry gas. The dry gas humidified by the humidification system 26 is supplied to the fuel cell stack 12 and used for power generation.

[0019] The humidification system 26 includes a humidification module 28, a bypass flow path 30, a first valve 32, a second valve 34, and a third valve 36. The humidification system 26 also includes a first pipe 68 that forms part of the cathode supply flow path 18 and a second pipe 70 that forms part of the cathode discharge flow path 20 (see Figure 2).

[0020] As shown in FIGS. 2 and 3A, the humidification module 28 includes a housing 38, a membrane module 40, a dry gas introduction portion 42, a dry gas discharge portion 44, a wet gas introduction portion 46, and a wet gas discharge portion 48. The housing 38 accommodates and supports the membrane module 40. The housing 38 is formed of, for example, a metal member such as an aluminum alloy, and has a larger heat capacity and relatively good thermal conductivity than the dry gas introduction portion 42, the dry gas discharge portion 44, the wet gas introduction portion 46, and the wet gas discharge portion 48.

[0021] In the following description, the terms lateral direction, stacking direction, and vertical direction are used to describe the arrangement relationship of each component configuration of the humidification system 26. The lateral direction is the horizontal direction in the normal arrangement state of the humidification system 26, and is a direction parallel to the permeable membranes 60 of the membrane module 40. In the lateral direction, the direction from the center of the membrane module 40 toward the dry gas introduction portion 42 is referred to as a first direction, and the direction from the center of the membrane module 40 toward the dry gas discharge portion 44 is referred to as a second direction.

[0022] The stacking direction is the horizontal direction in the normal arrangement state of the humidification system 26, and is the stacking direction of the permeable membranes 60 of the membrane module 40. The stacking direction is orthogonal to the lateral direction. The vertical direction is the vertical direction in the normal arrangement state of the humidification system 26, and is a direction orthogonal to the lateral direction and the stacking direction. It should be noted that the humidification system 26 mounted on the vehicle-mounted fuel cell system 10 may be tilted depending on the parking position of the vehicle. In this case, the lateral direction and the stacking direction do not necessarily coincide with the horizontal direction, and the vertical direction also does not coincide with the vertical direction.

[0023] The housing 38 is formed in a rectangular parallelepiped shape, and has a first side surface 38a, a second side surface 38b, a third side wall 38c, a fourth side wall 38d, an upper surface 38e, and a lower surface 38f. The first side surface 38a and the second side surface 38b are perpendicular to the lateral direction. A first opening 50 is formed in the first side surface 38a. The first surface 40a of the membrane module 40 is exposed at the first opening 50. Dry gas flows into the membrane module 40 through the first opening 50.

[0024] The second side surface 38b is located on the opposite side (second direction end) from the first side surface 38a in the lateral direction. A second opening 52 is formed on the second side surface 38b. The second surface 40b of the membrane module 40 is exposed through the second opening 52. The second opening 52 allows the dry gas humidified in the membrane module 40 to flow out of the housing 38.

[0025] No openings are formed in the third side wall 38c and the fourth side wall 38d. The top surface 38e is located at the upper end of the housing 38 and has a surface perpendicular to the vertical direction. A third opening 54 is formed in the top surface 38e. The third opening 54 exposes a portion of the top surface 40e of the membrane module 40. The third opening 54 communicates with an inlet space 54a formed in the top surface 38e of the housing 38. The inlet space 54a communicates with each of the second flow channels 64 of the membrane module 40. Wet gas is introduced into the second flow channels 64 of the membrane module 40 through the third opening 54.

[0026] The lower surface 38f is located at the lower end of the housing 38 and has a surface perpendicular to the vertical direction. A fourth opening 56 is formed in the lower surface 38f. The fourth opening 56 is rectangular in shape and exposes the lower surface 40f of the membrane module 40. The wet gas that has passed through the membrane module 40 is discharged to the wet gas discharge section 48 through the fourth opening 56.

[0027] A drain passage 58 is formed at the connection point between the second side surface 38b and the bottom surface 38f of the lower part of the housing 38. The drain passage 58 discharges water condensed at the dry gas discharge section 44, which is the outlet for humidified dry gas, to the wet gas discharge section 48, which is the outlet for wet gas. The upper end 58a of the drain passage 58 opens to the second opening 52, as shown in Figure 5. Water condensed at the dry gas discharge section 44 can flow into the drain passage 58 from the upper end 58a. The lower end 58b of the drain passage 58 opens to the fourth opening 56. The lower end 58b is located above the water storage section 48b of the wet gas discharge section 48. This allows water discharged from the drain passage 58 to be guided to the water storage section 48b, improving drainage.

[0028] As shown in Figure 4A, the drain passage 58 comprises a first straight section 58c, a second straight section 58d, and an orifice 58e. The first straight section 58c is a portion extending linearly from the upper end 58a of the drain passage 58. The second straight section 58d is a portion extending linearly from the lower end 58b of the drain passage 58. The orifice 58e is formed at the bend 58f between the first straight section 58c and the second straight section 58d, and connects the first straight section 58c and the second straight section 58d. The first straight section 58c and the second straight section 58d have the same flow path cross-sectional area. The orifice 58e has a smaller flow path cross-sectional area than the first straight section 58c and the second straight section 58d. The orifice 58e prevents dry gas leakage through the drain passage 58.

[0029] The drain passage 58 as a whole is inclined downward as it progresses in the first lateral direction. The first inclination angle θ1 formed by the first straight section 58c with the second direction is greater than the second inclination angle θ2 formed by the second straight section 58d with the second direction. The first inclination angle θ1 and the second inclination angle θ2 are set to values ​​greater than, for example, the maximum inclination angle of the vehicle (e.g., 19° or more). Such a drain passage 58 allows condensation water from the dry gas discharge section 44 to be discharged to the wet gas discharge section 48 even when the vehicle is parked on an inclined surface.

[0030] The drain passage 58 is manufactured by forming a first straight section 58c and a second straight section 58d, respectively, using a drill of a predetermined diameter. An orifice 58e is formed at the connection point between the first straight section 58c and the second straight section 58d. When precisely controlling the inner diameter of the orifice 58e, a first drilling process is performed so that the first straight section 58c and the second straight section 58d do not penetrate through. Subsequently, a second drilling process is performed using a drill with a smaller orifice diameter to connect the first straight section 58c and the second straight section 58d. Such processing enables the efficient formation of the drain passage 58 having the orifice 58e. The housing 38 may be formed by resin molding or the like, in which case the drain passage 58 may be formed together with the housing 38 by resin molding.

[0031] Furthermore, the drain passage 58 is not limited to cases where the first inclination angle θ1 of the first straight section 58c and the second inclination angle θ2 of the second straight section 58d are different. For example, as shown in Figure 4B, the drain passage 58 may have the same first inclination angle θ1 of the first straight section 58c and the same second inclination angle θ2 of the second straight section 58d, and the first straight section 58c and the second straight section 58d may be aligned on the same axis.

[0032] As shown in Figures 2, 3A, and 3B, the membrane module 40 comprises a plurality of permeable membranes 60 stacked in the stacking direction. Each permeable membrane 60 is made of a material that readily allows water vapor to pass through. The membrane module 40 is formed as a rectangular parallelepiped by stacking a plurality of rectangular permeable membranes 60.

[0033] The membrane module 40 has a first surface 40a, a second surface 40b, a third surface 40c, a fourth surface 40d, an upper surface 40e, and a lower surface 40f. The first surface 40a is parallel to the vertical direction and perpendicular to the horizontal direction, and is the surface facing the first side surface 38a. The second surface 40b is parallel to the first surface 40a and is located on the opposite side of the first surface 40a in the horizontal direction. The second surface 40b faces the second side surface 38b. The third surface 40c is perpendicular to the stacking direction and faces the third side wall 38c. The fourth surface 40d is perpendicular to the stacking direction and faces the fourth side wall 38d. The upper surface 40e is located at the upper end of the membrane module 40, is perpendicular to the vertical direction, and faces the upper surface 38e. The lower surface 40f faces the lower surface 38f of the membrane module 40.

[0034] Each permeable membrane 60 is stacked spaced apart in the stacking direction, and has a first gap 60a and a second gap 60b between them. The first gap 60a and the second gap 60b are adjacent to each other with the permeable membrane 60 in between. The first gap 60a forms a first channel 62, and the second gap 60b forms a second channel 64.

[0035] The flow direction of the first channel 62 and the flow direction of the second channel 64 are defined by sealing a predetermined portion of the peripheral edge of the permeable membrane 60 with a sealing member 66. The first channel 62 has its upper surface 40e and lower surface 40f closed by the sealing member 66 and is open on the first surface 40a and the second surface 40b. The first channel 62 communicates with the first opening 50 and the second opening 52 and allows dry gas to flow laterally from the first surface 40a to the second surface 40b.

[0036] The second channel 64 has its first surface 40a, second surface 40b, third surface 40c, and fourth surface 40d closed by a sealing member 66, and is open at the upper surface 40e and lower surface 40f. The second channel 64 communicates with the third opening 54 and the fourth opening 56, and allows the wet gas to flow vertically (downward) from the upper surface 40e to the lower surface 40f. By allowing the wet gas to flow downward, the droplet-like water contained in the wet gas is discharged without accumulating inside the membrane module 40. The droplet-like water discharged from the second channel 64 is collected in the water reservoir 48b of the wet gas discharge section 48 located below the membrane module 40.

[0037] The edges of the membrane module 40 are in airtight contact with the housing 38, preventing the leakage of dry gas and wet gas through the gap between the membrane module 40 and the housing 38.

[0038] The dry gas introduction section 42 is a component for connecting the first piping 68 upstream of the cathode supply channel 18 to the humidification module 28, and is connected to the first side surface 38a of the housing 38. The dry gas introduction section 42 has a first flange portion 42a that abuts against the first side surface 38a, and a first bulge portion 42b that protrudes a short distance from the first flange portion 42a in a first lateral direction. The first flange portion 42a is arranged to surround the periphery of the first bulge portion 42b and is in airtight contact with the first side surface 38a by a packing or the like. The first flange portion 42a is fixed to the housing 38 by methods such as fastening with bolts, bonding with adhesive, welding, etc. The first flange portion 42a may also be formed integrally with the housing 38 by molding.

[0039] The first bulge 42b has a dry gas inlet 42c formed at its end in the first direction, and also has a first connecting passage 42e inside. A first pipe 68, which forms part of the cathode supply passage 18, is connected to the dry gas inlet 42c via a third valve 36. The first connecting passage 42e connects the dry gas inlet 42c to the first opening 50. The first connecting passage 42e widens in diameter as it approaches the housing 38. The first bulge 42b has a dry-in inclined section 42f at its lower part. The dry-in inclined section 42f is formed from the dry gas inlet 42c to the first opening 50 and inclined downward as it approaches the housing 38.

[0040] The third inclination angle θ3 between the dry-in inclined section 42f and the first lateral direction is preferably greater than the maximum inclination angle expected in a vehicle (for example, 19°). By inclining the dry-in inclined section 42f at the third inclination angle θ3, it is possible to prevent the freezing of condensation water near the third valve 36 even if the vehicle stops in an inclined location and the operation of the fuel cell system 10 is stopped.

[0041] This dry-in inclined section 42f prevents the accumulation of condensed water near the third valve 36 by directing the water droplets that have formed near the third valve 36 downwards. This dry gas introduction section 42 prevents malfunction of the third valve 36 due to freezing in low-temperature environments.

[0042] The lateral bulge length of the first bulge portion 42b is set according to the size of the drive mechanism 36a of the third valve 36. Preferably, the bulge length of the first bulge portion 42b is formed to be as short as possible without interfering with the first flange portion 42a, etc. This allows the third valve 36 to be positioned near the housing 38, which has a large heat capacity, and effectively prevents the freezing of condensation water on the third valve 36.

[0043] As shown in Figure 2, the dry gas discharge section 44 is a component for connecting the downstream piping (not shown) of the cathode supply channel 18 to the humidification module 28, and is attached to the second side surface 38b of the housing 38. The dry gas discharge section 44 has a second flange portion 44a that abuts against the second side surface 38b, and a second bulge portion 44b that protrudes from the second flange portion 44a in a second lateral direction. The second flange portion 44a is positioned to surround the peripheral edge of the second bulge portion 44b, and the gap between it and the second side surface 38b is airtightly sealed via a packing or the like. The second flange portion 44a is fixed to the housing 38 by methods such as bolting, adhesive bonding, welding, etc.

[0044] The second bulge 44b has a bypass outlet 44c, a second connecting channel 44e, and a dry gas outlet 44f to which the downstream piping of the cathode supply channel 18 is connected. The bypass outlet 44c is provided on the side of the second bulge 44b in the stacking direction. The second valve 34 is connected to the bypass outlet 44c. The bypass outlet 44c is connected to the bypass channel 30 (bypass piping 72) via the second valve 34. The position of the bypass outlet 44c is set as close to the housing 38 as possible, within the range where the drive unit of the second valve 34 does not interfere with the housing 38. Also, the bypass outlet 44c is located above the lower surface 40f of the membrane module 40. When the bypass outlet 44c is positioned in this way, the occurrence of opening and closing malfunctions of the second valve 34 due to the freezing of condensation water is suppressed.

[0045] The second connecting channel 44e is formed inside the second bulge 44b and connects the second opening 52 with the bypass outlet 44c and the dry gas outlet 44f. Below the second connecting channel 44e, a dry-out inclined section 44g is formed, which slopes downward as the second bulge 44b approaches the housing 38. The lower end of the dry-out inclined section 44g is connected to the second opening 52 of the housing 38. Such a dry-out inclined section 44g prevents the accumulation of condensation water by smoothly guiding the moisture condensed inside the second bulge 44b to the drain passage 58. The fourth inclination angle θ4 between the dry-out inclined section 44g and the second direction is preferably greater than the maximum inclination angle expected in vehicles, etc. (for example, 19°).

[0046] The wet gas inlet 46 is located on the upper part of the upper surface 38e of the housing 38 and protrudes briefly upward. The wet gas inlet 46 is a component for connecting the upstream piping of the cathode discharge channel 20 extending from the fuel cell stack 12 to the humidification module 28. A third connection channel 46a formed inside the wet gas inlet 46 communicates with the inlet space 54a.

[0047] The wet gas discharge section 48 is a component for connecting the second pipe 70 downstream of the cathode discharge channel 20 to the humidification module 28. The wet gas discharge section 48 is attached to the lower surface 38f of the housing 38. The wet gas discharge section 48 comprises a fourth flange section 48a that abuts against the lower surface 38f, a water reservoir section 48b, an inclined channel 48c, and a wet gas outlet 48d. The fourth flange section 48a is positioned to surround the periphery of the water reservoir section 48b and is in close contact with the lower surface 38f via a packing or the like. The fourth flange section 48a is fixed to the housing 38 by methods such as bolting, adhesive bonding, welding, or other means.

[0048] The water reservoir 48b is formed to bulge downward from the fourth flange portion 48a. The water reservoir 48b is located below the membrane module 40 and communicates with the second flow path 64. The water reservoir 48b stores condensed water contained in the wet gas flowing out from the second flow path 64. The water reservoir 48b is located below the lower end portion 58b of the drain passage 58 and stores condensed water flowing out from the drain passage 58. The volume of the water reservoir 48b is such that it will not overflow even if water vapor present in a predetermined space including the humidification system 26 condenses.

[0049] The inclined channel 48c extends from the water reservoir 48b downward toward the dry gas discharge section 44. The inclined channel 48c slopes upward toward the dry gas discharge section 44 as it moves from the water reservoir 48b toward the dry gas discharge section 44. An inclined wall 48e is formed at the top of the inclined channel 48c, which is inclined laterally. The inclined wall 48e is positioned opposite at least a portion of the dry-out inclined section 44g of the dry gas discharge section 44, with a small gap between them. This positions the first valve 32, described later, near the housing 38, thereby suppressing freezing of the first valve 32. Furthermore, this arrangement allows for a smaller device configuration of the humidification system 26, contributing to the miniaturization of the fuel cell system 10.

[0050] For example, the inclined flow path 48c may extend downward toward the dry gas discharge section 44. In this case, the inclined flow path 48c is inclined upward toward the dry gas discharge section 44 as it moves from the water reservoir section 48b. The first valve 32 is connected to the upper end of the inclined flow path 48c, and when viewed from the side, at least a portion of the first valve 32 may overlap with the side of the dry gas discharge section 44. When viewed from the side, at least a portion of the first valve 32 may overlap with the second side surface 38b.

[0051] Furthermore, in order to position the inclined flow path 48c close to the dry gas discharge section 44, the housing 38 has a notch 38g near the drain passage 58. The notch 38g is a portion of the housing 38 that has been cut out near the drain passage 58. The inclined flow path 48c passes through the notch 38g. The inclined wall 48e of the inclined flow path 48c is positioned to cover the notch 38g. It is preferable that the fifth inclination angle θ5 between the inclined flow path 48c and the second direction be greater than the maximum inclination angle expected in a vehicle, etc. (for example, 19°). By inclining the inclined flow path 48c at such a fifth inclination angle θ5, freezing near the first valve 32 can be prevented even if the vehicle is stopped in an inclined location.

[0052] The wet gas outlet 48d is located at the upper end of the inclined flow path 48c. The second pipe 70, located downstream of the cathode discharge flow path 20, is connected to the wet gas outlet 48d via the first valve 32.

[0053] As shown in Figures 1 and 2, the bypass channel 30 is a channel that directs dry gas to the dry gas discharge section 44 by bypassing the membrane module 40 of the humidification module 28. As shown in Figure 2, the bypass channel 30 is composed of a bypass pipe 72 that branches off from the first pipe 68 of the humidification system 26. The downstream end of the bypass pipe 72 is connected to the dry gas discharge section 44 via a second valve 34.

[0054] The second valve 34 is positioned such that the lower end of the portion exposed to the second connecting channel 44e is higher than the lower surface 40f of the membrane module 40. This prevents the accumulation of condensation water in the vicinity of the second valve 34. It is preferable to position the second valve 34 as close to the housing 38 as possible. As shown in Figure 2, it is preferable to position the second valve 34 so that it overlaps with the first valve 32 when viewed from above. By positioning it in this way, the second valve 34 is also located near the housing 38, which has a large heat capacity, thus preventing the second valve 34 from freezing.

[0055] The humidification system 26 further includes a first pipe 68 and a second pipe 70. The first pipe 68 is connected to the upstream side of the dry gas inlet 42 and constitutes part of the upstream portion of the cathode supply channel 18. A third valve 36 is provided at the connection between the first pipe 68 and the dry gas inlet 42. The third valve 36 is a sealing valve capable of sealing the first pipe 68. The first pipe 68 has a branching point with the bypass pipe 72 near the third valve 36.

[0056] The second pipe 70 is connected to the wet gas outlet 48d of the wet gas discharge section 48 via the first valve 32. The second pipe 70 forms part of the downstream side of the cathode discharge channel 20 and discharges the wet gas that has passed through the humidification system 26.

[0057] The first valve 32 is positioned higher than the water reservoir 48b. This allows wet gas to be introduced to the first valve 32 without entraining condensed water from the water reservoir 48b. As a result, freezing of water near the first valve 32 is prevented.

[0058] Furthermore, at least a portion of the first valve 32 is positioned to face laterally toward the second side surface 38b of the housing 38. This makes it more difficult for the first valve 32 to cool down, and more effectively suppresses condensation of water on the first valve 32.

[0059] The humidification system 26 of this embodiment is configured as described above. The operation of the humidification system 26 will now be explained.

[0060] When the fuel cell system 10 is shut down, the third valve 36, the second valve 34, and the first valve 32 shown in Figure 2 are closed. The space on the cathode side of the fuel cell stack 12 is in communication with the humidification module 28, but is isolated from the outside by the third valve 36, the second valve 34, and the first valve 32.

[0061] As time passes after the fuel cell system 10 has been shut down in a low-temperature environment, the humidification system 26 cools down, and the temperature drops first from the dry gas inlet 42, dry gas outlet 44, wet gas inlet 46, and wet gas outlet 48, which have relatively small heat capacities. When the temperature of these parts falls below the dew point temperature of the water vapor contained inside the humidification module 28, water vapor condenses. Condensation of water vapor proceeds preferentially in areas with lower temperatures. The housing 38, which has a large heat capacity, cools down slowly and therefore remains at a relatively high temperature.

[0062] In the humidification system 26 of this embodiment, the first valve 32, the second valve 34, and the third valve 36 are positioned near the housing 38, which has a large heat capacity. Therefore, the first valve 32, the second valve 34, and the third valve 36 do not cool down easily due to heat conduction and radiation from the housing 38, and thus condensation on the surfaces of these valves is suppressed.

[0063] If more time passes in a low-temperature environment, the temperature of the humidification system 26 will fall below the freezing point of the condensation water, causing the condensation water to freeze. Even in this case, freezing of the first valve 32, the second valve 34, and the third valve 36 is prevented, allowing for smooth operation in low-temperature environments.

[0064] Furthermore, since the drain passage 58 is formed inside the housing 38, the heat from the high-temperature wet gas (cathode-off gas) flowing inside the housing 38 after restarting quickly thaws the internal freezing state, allowing the drain passage 58 to open promptly. This prevents malfunctions of the humidification system 26.

[0065] With regard to the above embodiments, the following additional information is disclosed.

[0066] (Note 1) The humidification system (26) of this disclosure comprises a membrane module (40) that imparts moisture from a wet gas to a dry gas via a plurality of permeable membranes (60) that allow water vapor to pass through; a housing (38) that surrounds the membrane module; a dry gas introduction section (42) connected to the housing and introducing the dry gas into the membrane module; a dry gas discharge section (44) connected to the housing and discharging the dry gas from the membrane module; a wet gas introduction section (46) provided in the housing and introducing the wet gas into the membrane module; a wet gas discharge section (48) connected to the housing and discharging the wet gas from the membrane module; and a drain passage (58) that connects the dry gas discharge section and the wet gas discharge section and allows water condensed in the dry gas discharge section to flow to the wet gas discharge section, wherein the drain passage is formed inside the housing.

[0067] In the humidification system described above, a drain passage is formed inside a housing with a large heat capacity. As a result, the heat from the wet gas is transferred to the drain passage through the housing, quickly melting any frozen moisture in the drain passage. This allows the drain passage to be opened quickly after startup, even in low-temperature environments.

[0068] (Note 2) The humidification system described in Appendix 1, wherein the housing has a second opening (52) opening toward the dry gas discharge section and a fourth opening (56) opening toward the wet gas discharge section, and the drain passage may have an upper end (58a) exposed to the second opening of the housing and a lower end (58b) opening to the fourth opening of the housing. In this humidification system, since the entire drain passage is formed within the housing, the heat of the wet gas can be transferred to the drain passage through the housing, and the freezing of the drain passage can be quickly released.

[0069] (Note 3) The humidification system described in Appendix 2 includes a dry gas discharge section having a dry-out inclined section (44g) that slopes downward as it approaches the housing, and the upper end of the drain passage may be positioned where water collected in the dry-out inclined section flows in. This humidification system can smoothly discharge condensation water generated in the dry gas discharge section through the drain passage.

[0070] (Note 4) The humidification system described in Appendix 2 or 3, wherein the wet gas discharge section comprises a fourth flange portion (48a) in contact with the housing, a water reservoir portion (48b) bulging downward from the fourth flange portion, an inclined flow path (48c) extending upward from the water reservoir portion toward the dry gas discharge section, and a wet gas outlet (48d) extending from the upper end of the inclined flow path, wherein the water reservoir portion may be located below the lower end of the drain passage. This humidification system can guide water discharged from the drain passage to the water reservoir portion, thereby improving drainage.

[0071] (Note 5) The humidification system described in Appendix 2, wherein the drain passage has a first straight section (58c) extending from the upper end, a second straight section (58d) extending from the lower end, and a bent section (58f) provided at the connection between the first straight section and the second straight section, and the bent section may have an orifice (58e) having a flow path cross-sectional area smaller than the flow path cross-sectional area of ​​the first straight section and the second straight section. This humidification system can ensure a drainage slope in the drain passage, and can ensure drainage even if the humidification system is slightly tilted.

[0072] (Note 6) The humidification system of this disclosure includes a membrane module that imparts moisture from a wet gas to a dry gas through a plurality of permeable membranes that allow water vapor to pass through; a housing that surrounds the membrane module; a dry gas introduction unit connected to a first side surface (38a) of the housing for introducing the dry gas into the membrane module; a dry gas discharge unit connected to a second side surface (38b) of the housing for discharging the dry gas from the membrane module; and a wet gas introduction unit connected to the top surface (38e) of the housing for introducing the wet gas into the membrane module. The device comprises an introduction section, a wet gas discharge section connected to the lower surface (38f) of the housing for discharging the wet gas from the membrane module, and a first valve (32) connected to the wet gas discharge section, wherein the wet gas discharge section has an inclined flow path that slopes upward as it approaches the second side surface from below the housing, with its upper part overlapping the side surface of the housing, and the first valve is connected to the upper end of the inclined flow path, and at least a part of the first valve overlaps the second side surface when viewed from the side.

[0073] The humidification system described above allows the first valve, which is connected to the inclined flow path of the wet gas discharge section, to be positioned close to a housing with a large heat capacity. As a result, the first valve is less likely to cool down due to the heat of the housing, thus preventing the first valve from freezing. Furthermore, the humidification system can be made more compact.

[0074] (Note 7) The humidification system described in Appendix 6, wherein the wet gas discharge section has a water reservoir formed between a fourth opening provided on the lower surface of the housing and the first valve, the water reservoir being located below the first valve, and the first valve being positioned so as to overlap with the second side when viewed from the side. By providing a water reservoir in the wet gas discharge section, this humidification system can remove water droplets that may adhere to the first valve. Furthermore, since the first valve is positioned closer to the housing, which has a large heat capacity, freezing of the first valve can be prevented more effectively.

[0075] (Note 8) The humidification system described in Appendix 7, wherein the first valve is connected to the upper end of the inclined flow path, and when viewed from the side, at least a portion of the first valve may overlap the side of the dry gas discharge section. In this humidification system, in addition to the first valve, the second valve can be positioned closer to the housing with a large heat capacity, so that each valve is less likely to cool down, and freezing of the first valve and the second valve can be prevented.

[0076] (Note 9) The humidification system described in Appendix 8, wherein the dry gas discharge section includes a dry-out inclined section (44g) at its lower end that slopes downward as it approaches the housing, and the inclined flow path of the wet gas discharge section has an inclined wall (48e) at its upper end that slopes upward as it moves from the water reservoir towards the dry gas discharge section, and the inclined wall may face at least a portion of the dry-out inclined section of the dry gas discharge section. This humidification system can effectively prevent the first valve from freezing because the first valve can be positioned close to the housing, which has a large heat capacity.

[0077] (Note 10) The humidification system described in Appendix 9 may have a dry gas inlet section at its lower part that slopes downward as it approaches the housing from the first valve. In this humidification system, the third valve provided at the inlet of the dry gas inlet section can be positioned closer to the housing, making it less likely for the third valve to cool down and preventing it from freezing.

[0078] (Note 11) The humidification system described in Appendix 10 is characterized in that the dry gas flows laterally through the first gap (60a) of the permeable membrane, the wet gas flows vertically through the second gap (60b) of the permeable membrane, and the wet gas discharge section may be located below the housing. In this humidification system, since droplets in the second gap of the membrane module are discharged by gravity, damage to the permeable membrane and blockage of the second gap due to ice growth inside the membrane module can be prevented.

[0079] (Note 12) The humidification system described in Appendix 11 may have a housing with a larger heat capacity than the dry gas inlet, the dry gas outlet, the wet gas inlet, and the wet gas outlet. In this humidification system, the second valve can be positioned closer to the housing with a larger heat capacity in addition to the first valve, so that each valve is less likely to cool down, and freezing of the first valve and the second valve can be prevented.

[0080] (Note 13) The fuel cell system (10) of this disclosure comprises a fuel cell stack (12) and a humidification system described in any one of appendices 1 to 12, wherein the dry gas is a cathode gas supplied to the fuel cell stack and the wet gas is a cathode-off gas discharged from the fuel cell stack. This fuel cell system can utilize the heat of the wet gas heated in the fuel cell stack to thaw the freezing of the drain passage or valve, and can therefore be started up smoothly even in low-temperature environments.

[0081] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of Symbols]

[0082] 10…Fuel cell system 12…Fuel cell stack 26…Humidification system 30…Bypass channel 32...1st valve 34...2nd valve 36…Third valve 38…Housing 40…Membrane module 42…Dry gas inlet 42f...Dry-in inclined section 44...Dry gas discharge section 44g...Dry-out inclined section 46...Wet gas inlet section 48...Wet gas discharge section 48a...Fourth flange section 48b...Water storage section 48c...Inclined channel 48d...Wet gas outlet 52...Second opening 56...Fourth opening 58...Drain passage 58a...Top end 58b...Bottom end 58c...First straight section 58d...Second straight section 58e... Orifice 58f... Bending point 60...Permeable membrane 60a...First gap 60b...Second gap 68...First piping

Claims

1. A membrane module that transfers moisture from a wet gas to a dry gas through multiple permeable membranes that allow water vapor to pass through, A housing that surrounds the aforementioned membrane module, A dry gas introduction unit connected to the housing for introducing the dry gas into the membrane module, A dry gas discharge unit connected to the housing and which discharges the dry gas from the membrane module, A wet gas introduction unit provided in the housing for introducing the wet gas into the membrane module, A wet gas discharge unit connected to the housing and for discharging the wet gas from the membrane module, The dry gas discharge section and the wet gas discharge section are connected, and a drain passage is provided to allow water condensed in the dry gas discharge section to flow to the wet gas discharge section. The drain passage is formed inside the housing, and is part of a humidification system.

2. A humidification system according to claim 1, The aforementioned housing is A second opening that opens toward the dry gas discharge section, It has a fourth opening that opens toward the wet gas discharge section, A humidification system in which the drain passage has an upper end that opens into the second opening of the housing and a lower end that opens into the fourth opening of the housing.

3. A humidification system according to claim 2, The dry gas discharge section has a dry-out inclined section that slopes downward as it approaches the housing, A humidification system in which the upper end of the drain passage is located at a position into which water collected in the dry-out inclined section flows.

4. A humidification system according to claim 2, The aforementioned wet gas discharge section is A fourth flange portion that abuts against the housing, The water storage section bulges downward from the fourth flange portion, A sloping channel extends upward from the water storage section towards the dry gas discharge section, It comprises a wet gas outlet extending from the upper end of the aforementioned inclined flow path, The water storage section is a humidification system located below the lower end of the drain passage.

5. A humidification system according to claim 2, The aforementioned drain passage is A first straight section extending from the upper end, A second straight section extending from the lower end, It has a bent portion provided at the connection point between the first straight portion and the second straight portion, A humidification system in which an orifice having a flow path cross-sectional area smaller than the flow path cross-sectional area of ​​the first straight section and the second straight section is formed in the bent section.

6. Fuel cell stack and A humidification system according to any one of claims 1 to 5, comprising: The dry gas is the cathode gas supplied to the fuel cell stack. A fuel cell system in which the wet gas is the cathode-off gas discharged from the fuel cell stack.

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