Fuel cell system

Abstract

To provide a fuel cell system capable of improving sealing performance of air in an exhaust cylinder without changing a layout.SOLUTION: A fuel cell system 10 includes a fuel cell stack, a water storage tank 50, a cathode off-gas exhaust pipe 63, and a drain port 54b. The water storage tank 50 stores water generated by power generation of the fuel cell stack. The cathode off-gas exhaust pipe 63 has an exhaust port 71 that opens at an exhaust end 70. The exhaust port 71 opens below the drain port 54b. That is, the fuel cell system 10 seals the exhaust port 71 with the water stored in the water storage tank 50. As a result, the fuel cell system 10 can improve sealing performance of air in the cathode off-gas exhaust pipe 63 without changing a layout.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system. [Background technology]

[0002] Conventionally, a fuel cell system includes a fuel cell. The fuel cell generates electricity to supply to a load connected to the fuel cell. The fuel cell generates electricity by chemically reacting hydrogen supplied to the anode with oxygen supplied to the cathode. The fuel cell produces water by chemically reacting hydrogen with oxygen.

[0003] The fuel cell system has an exhaust pipe and a water storage tank. The exhaust pipe connects the cathode of the fuel cell to the water storage tank and has an exhaust port that opens toward the inside of the water storage tank. The exhaust pipe introduces water produced by the fuel cell into the water storage tank along with cathode exhaust gas discharged from the fuel cell. The water introduced into the water storage tank is discharged to the outside of the water storage tank through a drain outlet provided in the water storage tank.

[0004] For example, Patent Document 1 discloses a fuel cell water tank, which is a water storage tank, that includes a first vent pipe, which serves as an exhaust pipe, and a second vent pipe. The first vent pipe introduces cathode exhaust containing a trace amount of moisture into the water storage tank. The first vent pipe connects the oxidizer electrode, which serves as the cathode in the fuel cell, to a gas phase space located vertically above the liquid level of the water stored in the water storage tank. The second vent pipe connects to the gas phase space and exhausts the cathode exhaust from within the gas phase space. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-135944 Summary of the Invention [Problem to be solved by the invention]

[0006] In a situation where there is no cathode exhaust from the fuel cell, air flowing back up the exhaust stack may enter the cathode of the fuel cell, causing deterioration of the fuel cell. In a fuel cell system, it is desirable to improve the air sealing performance in the exhaust stack without changing the layout. [Means for solving the problem]

[0007] The fuel cell system for solving the above problem comprises a fuel cell, a water storage tank for storing water produced as the fuel cell generates electricity, and an exhaust pipe for introducing cathode off-gas discharged from the cathode of the fuel cell into the water storage tank, wherein a drain outlet is opened in the tank wall extending vertically from the bottom of the water storage tank, and the exhaust pipe has an exhaust end housed in the water storage tank and an exhaust port opening at the exhaust end, and the exhaust port opens below the drain outlet.

[0008] The generated water stored in the water storage tank is periodically discharged through the drain outlet in an amount exceeding the height of the drain outlet. When water is stored in the water storage tank until the water level reaches the bottom of the drain outlet, the exhaust outlet is open underwater. In other words, the water stored in the water storage tank seals the exhaust outlet. This allows the fuel cell system to prevent air from flowing from the water storage tank into the exhaust stack. As a result, the above configuration can improve the air sealing performance in the exhaust stack without changing the layout of the fuel cell system.

[0009] In the fuel cell system, an imaginary plane including an opening edge of the exhaust port may be parallel to a bottom surface of the tank. According to this, the exhaust port opens in the water storage tank in a direction in which an imaginary plane is parallel to the water surface. When the water level in the water storage tank is below the drain outlet, in order for the water in the water storage tank to seal the exhaust port, the water level must be higher than the portion of the exhaust port's opening edge that is farthest from the tank bottom. In other words, for the same vertical length of the exhaust stack in the water storage tank, an exhaust stack that opens in a direction in which the imaginary plane is perpendicular to the water surface requires a lower water level to seal air than an exhaust stack that opens in a direction that is not perpendicular to the water surface. Furthermore, when the exhaust port opens in a direction perpendicular to the water surface, the water in the water storage tank can seal air from entering the exhaust stack even when the edge of the exhaust port is in contact with the water surface. As a result, the fuel cell system can seal air from entering the exhaust stack with a smaller amount of water than when the exhaust port opens in a direction that is not parallel to the water surface.

[0010] In the above fuel cell system, the exhaust stack may be made of metal. When the exhaust port opens below the water level in the water storage tank, the water level outside the exhaust stack is highest at the position where it contacts the outer surface of the exhaust stack. In other words, the water level in the water storage tank is inclined so that it is highest at the point where it contacts the outer surface of the exhaust stack. In this case, the water level inside the exhaust stack is also highest at the position where it contacts the inner surface of the exhaust stack. In other words, the water level in the water storage tank is inclined so that it is highest at the point where it contacts the inner surface of the exhaust stack. The rise in the water level on each of the outer and inner surfaces of the exhaust stack seals off air flowing into the exhaust stack. When the exhaust stack is made of metal, the water level at the points where it contacts the inner and outer surfaces of the exhaust stack rises higher compared to, for example, when the exhaust stack is made of synthetic resin. In other words, when the exhaust stack is made of metal, the water level around the exhaust stack rises compared to, for example, when the exhaust stack is made of synthetic resin, so air flowing into the exhaust stack can be more reliably sealed off.

[0011] The above fuel cell system may further include a diluter into which water and anode off-gas produced by the fuel cell flow and which dilutes the anode off-gas, and the water storage tank may be integrated with the diluter and store water discharged from the diluter.

[0012] According to this, the water storage tank stores water introduced together with the cathode off-gas through the exhaust stack, as well as water discharged from the diluter. In other words, the water storage tank efficiently introduces water produced in the fuel cell system compared to when the water storage tank does not receive wastewater from the diluter. As a result, the fuel cell system can more easily maintain the water level in the water storage tank above the drain outlet compared to when the water storage tank does not receive wastewater from the diluter.

[0013] In the above fuel cell system, the tank bottom surface may have a first bottom surface aligned with the exhaust end in the vertical direction, and a second bottom surface that is a different surface of the tank bottom surface from the first bottom surface in the vertical direction, and the first bottom surface may be lower than the second bottom surface in the vertical direction, and the second bottom surface may be higher than the exhaust port.

[0014] According to this, the exhaust end of the water storage tank opens below the second bottom surface. In other words, the air flowing into the exhaust pipe is sealed by water whose bottom surface is the first bottom surface and whose water surface is above the second bottom surface. Therefore, a smaller amount of water in the water storage tank can seal the exhaust pipe compared to when the tank bottom does not have a first bottom surface and a second bottom surface. As a result, the fuel cell system can seal the exhaust pipe more easily compared to when the tank bottom does not have a first bottom surface and a second bottom surface. [Effects of the Invention]

[0015] According to the present invention, the air sealing performance in the exhaust stack can be improved without changing the layout. [Brief explanation of the drawings]

[0016] [Figure 1]FIG. 1 is a side view showing a fuel cell forklift. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of a fuel cell system. [Figure 3] FIG. 3 is a cross-sectional view showing the cathode off-gas exhaust stack, the water tank, and the diluter. [Figure 4] FIG. 4 is an enlarged cross-sectional view showing the cathode off-gas exhaust stack. [Figure 5] FIG. 5 is a cross-sectional view showing the cathode off-gas exhaust stack, the water tank, and the diluter. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of a fuel cell system will now be described with reference to Figures 1 to 4. In this embodiment, the fuel cell system is mounted on a fuel cell forklift. <Fuel cell forklift> As shown in FIG. 1, the fuel cell forklift 100 has a vehicle body 101, a cargo handling device 102, and drive wheels 103. In the following description, front, rear, left, right, top, bottom, and bottom are determined based on the fuel cell forklift 100. The front-rear direction X is the direction of travel of the fuel cell forklift 100. The left-right direction Y is the width direction of the fuel cell forklift 100. The up-down direction Z is the height direction of the fuel cell forklift 100. In this embodiment, the up-down direction Z coincides with the vertical direction. That is, in this embodiment, the fuel cell forklift 100 is on the ground that is parallel to a horizontal plane.

[0018] The vehicle body 101 has a housing portion 101a. The housing portion 101a houses the fuel cell system 10. The fuel cell system 10 is housed in the housing portion 101a and thereby mounted on the vehicle body 101. In other words, the fuel cell forklift 100 has the fuel cell system 10.

[0019] The cargo handling device 102 is driven by the electric power generated by the fuel cell system 10. The electric power generated by the fuel cell system 10 is supplied to a cargo handling motor (not shown). The cargo handling motor uses the supplied electric power to drive the cargo handling device 102. The fuel cell forklift 100 performs cargo handling work using the cargo handling device 102.

[0020] The drive wheels 103 are driven by the electric power generated by the fuel cell system 10. The electric power generated by the fuel cell system 10 is supplied to a traction motor (not shown). The traction motor drives the drive wheels 103 using the supplied electric power. The fuel cell forklift 100 travels by the drive wheels 103.

[0021] <Fuel cell system> 2, the fuel cell system 10 includes a fuel cell stack 11 as a fuel cell, a hydrogen tank 12, and an air compressor 13. The fuel cell system 10 also includes an anode gas supply channel 21, a cathode gas supply channel 22, a first anode off-gas discharge channel 23, an anode gas circulation channel 24, a second anode off-gas discharge channel 25, and a cathode off-gas discharge channel 26. The fuel cell system 10 also includes a gas-liquid separator 30, a diluter 40, and a water storage tank 50.

[0022] The fuel cell stack 11 is made up of a plurality of fuel cell units 11a stacked together. The fuel cell units 11a are solid molecular fuel cells. The fuel cell stack 11 generates electricity when supplied with an anode gas and a cathode gas. The anode gas is hydrogen gas. The cathode gas is an oxidant gas and air.

[0023] The hydrogen tank 12 stores hydrogen gas. The hydrogen gas supplied to the fuel cell stack 11 is supplied from the hydrogen tank 12. The air compressor 13 compresses the air. The air compressed by the air compressor 13 is supplied to the fuel cell stack 11.

[0024] The anode gas supply channel 21 connects the anode 11b of the fuel cell stack 11 and the hydrogen tank 12. The hydrogen gas stored in the hydrogen tank 12 is introduced from the hydrogen tank 12 to the fuel cell stack 11 via the anode gas supply channel 21.

[0025] The cathode gas supply channel 22 connects the cathode 11c of the fuel cell stack 11 and the air compressor 13. Air compressed by the air compressor 13 is supplied to the cathode gas supply channel 22. The air compressed by the air compressor 13 is introduced from the air compressor 13 to the fuel cell stack 11 via the cathode gas supply channel 22.

[0026] The first anode off-gas discharge channel 23 connects the anode 11b of the fuel cell stack 11 to the gas-liquid separator 30. The anode off-gas discharged from the anode 11b of the fuel cell stack 11 is introduced from the anode 11b of the fuel cell stack 11 to the gas-liquid separator 30 via the first anode off-gas discharge channel 23. The anode off-gas mainly contains water that is produced when unreacted hydrogen gas in the fuel cell stack 11 reacts with the hydrogen and oxygen contained in the oxidant gas.

[0027] The anode off-gas discharged from the fuel cell stack 11 flows into the gas-liquid separator 30 through the first anode off-gas discharge channel 23. The gas-liquid separator 30 separates water contained in the anode off-gas from the anode off-gas.

[0028] The anode gas circulation path 24 connects the gas-liquid separator 30 and the anode gas supply path 21. The anode gas circulation path 24 receives the anode gas separated from the anode off-gas by the gas-liquid separator 30. The anode gas circulation path 24 introduces the anode gas from the gas-liquid separator 30 into the anode gas supply path 21.

[0029] The second anode off-gas discharge channel 25 connects the gas-liquid separator 30 and the diluter 40. The second anode off-gas discharge channel 25 introduces the anode off-gas, from which the anode gas has been separated by the gas-liquid separator 30, into the diluter 40. The anode off-gas flowing through the second anode off-gas discharge channel 25 mainly contains water and the anode gas that has not been separated by the gas-liquid separator 30 and remains.

[0030] The second anode off-gas discharge channel 25 is defined by the anode off-gas exhaust tube 61. In other words, the anode off-gas exhaust tube 61 connects the gas-liquid separator 30 and the diluter 40, and defines the second anode off-gas discharge channel 25 through which the anode off-gas can flow from the gas-liquid separator 30 toward the diluter 40.

[0031] The anode off-gas exhaust tube 61 has an on-off valve 62. In other words, the on-off valve 62 is provided in the second anode off-gas discharge channel 25. The on-off valve 62 is switchable between an open state in which the gas-liquid separator 30 and the diluter 40 are connected to each other, and a closed state in which the gas-liquid separator 30 and the diluter 40 are disconnected from each other in the second anode off-gas discharge channel 25. The on-off valve 62 is normally closed. When a predetermined amount of anode off-gas is accumulated in the gas-liquid separator 30, the on-off valve 62 momentarily opens. When the on-off valve 62 opens, the anode off-gas is discharged from the gas-liquid separator 30 toward the diluter 40.

[0032] The cathode off-gas discharge path 26 connects the cathode 11c of the fuel cell stack 11 to the water tank 50. The cathode off-gas is introduced from the cathode 11c of the fuel cell stack 11 to the water tank 50 through the cathode off-gas discharge path 26. The cathode off-gas mainly contains air containing unreacted oxygen in the fuel cell stack 11 and water produced when hydrogen reacts with oxygen.

[0033] An air pressure adjustment valve 64 is provided in the cathode offgas discharge path 26. The air pressure adjustment valve 64 opens and closes the cathode offgas discharge path 26. The fuel cell system 10 adjusts the pressure inside the fuel cell stack 11 by opening and closing the air pressure adjustment valve 64.

[0034] <Diluter> As shown in FIG. 3, the diluter 40 has a dilution container 41. The dilution container 41 is made of metal. The dilution container 41 has a container bottom plate 42, a container top plate 43, and a container side wall 44. The container bottom plate 42 and the container top plate 43 are each plate-shaped with a thickness direction in the vertical direction Z. The container bottom plate 42 and the container top plate 43 face each other in the vertical direction Z. The container side wall 44 connects the container bottom plate 42 and the container top plate 43. The container bottom plate 42, the container top plate 43, and the container side wall 44 define a dilution chamber 40a inside the dilution container 41. In other words, the diluter 40 has the dilution chamber 40a formed therein.

[0035] A diluter communication hole 42a is formed in the container bottom plate 42. The diluter communication hole 42a opens in the container bottom plate 42 in the up-down direction Z. In other words, the diluter communication hole 42a penetrates the container bottom plate 42 in the thickness direction.

[0036] An anode off-gas introduction hole 43a is formed in the container top plate 43. The anode off-gas introduction hole 43a is open in the up-down direction Z. In other words, the anode off-gas introduction hole 43a penetrates the container top plate 43 in the thickness direction.

[0037] 2 and 3, an anode offgas exhaust tube 61 is inserted into the anode offgas inlet 43a. The anode offgas exhaust tube 61 opens into the dilution chamber 40a. The dilution chamber 40a is connected to the gas-liquid separator 30 via the anode offgas exhaust tube 61. That is, when the on-off valve 62 is open, the anode offgas is supplied from the gas-liquid separator 30 to the dilution chamber 40. In other words, water produced by the fuel cell stack 11 and the anode offgas flow into the dilution chamber 40.

[0038] The container side wall 44 has a dilution exhaust port 44a. The dilution exhaust port 44a opens in the container side wall 44 in the front-to-rear direction X. The dilution exhaust port 44a may also open in the container side wall 44 in the left-to-right direction Y. The dilution exhaust port 44a connects the inside and outside of the dilution chamber 40a.

[0039] <Water tank> 3, the water storage tank 50 has a tank bottom plate 51, a tank top plate 52, and a tank side wall 53. The water storage tank 50 is made of resin.

[0040] The tank bottom plate 51 and the tank top plate 52 are plate-shaped and extend in the front-rear direction X and the left-right direction Y, with the thickness direction being the up-down direction Z. The tank bottom plate 51 and the tank top plate 52 are each rectangular with the longitudinal direction in the front-rear direction X. The tank bottom plate 51 and the tank top plate 52 face each other in the up-down direction Z.

[0041] The tank side wall 53 is plate-shaped and has a thickness perpendicular to the vertical direction Z. The tank side wall 53 is perpendicular to the tank bottom plate 51 and the tank top plate 52. The tank side wall 53 is made up of four plate-shaped members. Each plate-shaped member constituting the tank side wall 53 is connected at its lower edge in the vertical direction Z to an edge of the tank bottom plate 51. Each plate-shaped member constituting the tank side wall 53 is connected at its upper edge in the vertical direction Z to an edge of the tank top plate 52. Figure 2 illustrates three of the four plate-shaped members constituting the tank side wall 53. The tank side wall 53 extends in the vertical direction Z and connects the tank bottom plate 51 and the tank top plate 52. In other words, a first end of the tank side wall 53 in the vertical direction Z is connected to the tank bottom plate 51, and a second end of the tank side wall 53 in the vertical direction Z is connected to the tank top plate 52.

[0042] Inside the water storage tank 50, a tank chamber 50a is defined by a tank bottom plate 51, a tank top plate 52, and a tank side wall 53. The tank bottom plate 51 has a tank bottom surface 51a facing upward in the vertical direction Z. The tank top plate 52 has a top plate outer surface 52a and a top plate inner surface 52b in the vertical direction Z. The top plate outer surface 52a faces upward in the vertical direction Z. The top plate inner surface 52b faces downward in the vertical direction Z and faces the tank bottom surface 51a. The tank side wall 53 has a side wall outer surface 53a and a side wall inner surface 53b serving as a tank wall surface in a direction perpendicular to the vertical direction Z. The side wall outer surface 53a is connected to the top plate outer surface 52a. The side wall inner surface 53b is connected to both the tank bottom surface 51a and the top plate inner surface 52b.

[0043] The water storage tank 50 has a diluter 40 on a tank top plate 52. The diluter 40 is provided on an outer surface 52a of the tank top plate 52. In other words, the diluter 40 is provided above the water storage tank 50 in the vertical direction Z.

[0044] A cathode off-gas introduction hole 52c is formed in the tank top plate 52. The cathode off-gas introduction hole 52c is formed in a position of the tank top plate 52 that does not face the container bottom plate 42 of the diluter 40. The cathode off-gas introduction hole 52c opens in the tank top plate 52 in the up-down direction Z. In other words, the cathode off-gas introduction hole 52c penetrates the tank top plate 52 in the thickness direction.

[0045] As shown in FIGS. 2 and 3, a cathode offgas exhaust tube 63 serving as an exhaust tube is inserted into the cathode offgas inlet hole 52c. The cathode offgas exhaust tube 63 opens into the tank chamber 50a. The tank chamber 50a is connected to the cathode 11c of the fuel cell stack 11 via the cathode offgas exhaust tube 63. That is, when the air pressure regulating valve 64 is open, cathode offgas is supplied from the cathode 11c of the fuel cell stack 11 to the tank chamber 50a. In other words, air containing unreacted oxygen in the fuel cell stack 11 and water produced when hydrogen reacts with oxygen are introduced into the tank chamber 50a as cathode offgas through the cathode offgas exhaust tube 63.

[0046] The water contained in the cathode off-gas supplied by the cathode off-gas exhaust stack 63 is stored in the tank chamber 50a. That is, the water storage tank 50 stores water produced as the fuel cell stack 11 generates electricity.

[0047] A tank communication hole 52d is formed in the tank top plate 52. The tank communication hole 52d is a hole different from the cathode off-gas introduction hole 52c. The tank communication hole 52d opens in the up-down direction Z at a position on the tank top plate 52 different from the cathode off-gas introduction hole 52c. In other words, the tank communication hole 52d penetrates the tank top plate 52 in the thickness direction.

[0048] The tank communication hole 52d is formed in a position on the tank top plate 52 facing the container bottom plate 42 of the diluter 40. The tank communication hole 52d is formed in a position aligned with the diluter communication hole 42a in the vertical direction Z. That is, the tank communication hole 52d communicates with the diluter communication hole 42a. In other words, the tank chamber 50a communicates with the dilution chamber 40a via the tank communication hole 52d and the diluter communication hole 42a. The diluter 40 and the water storage tank 50 are connected without, for example, piping. In other words, the water storage tank 50 is integrated with the diluter 40.

[0049] The cathode off-gas discharge path 26 is connected to the dilution chamber 40a via the tank chamber 50a, the tank communication hole 52d, and the diluter communication hole 42a. In other words, oxygen that remains unreacted in the fuel cell stack 11 in the cathode off-gas introduced into the tank chamber 50a via the cathode off-gas discharge path 26 passes through the tank chamber 50a and flows into the dilution chamber 40a. The diluter 40 dilutes the hydrogen contained in the anode off-gas introduced from the gas-liquid separator 30 with oxygen flowing in from the water storage tank 50 and exhausts the diluted off-gas from the dilution exhaust port 44a. In other words, the diluter 40 dilutes the anode off-gas. Water generated during the dilution process flows into the tank chamber 50a via the diluter communication hole 42a and the tank communication hole 52d. The water generated in the diluter 40 is stored in the water storage tank 50. In other words, the water storage tank 50 stores water discharged from the diluter 40.

[0050] A drain pipe 54 is provided on the tank side wall 53. The drain pipe 54 has a drain outlet 54b. The drain outlet 54b opens toward the tank chamber 50a in the front-to-rear direction X. In other words, the drain outlet 54b opens on the tank side wall 53 of the water storage tank 50. The direction in which the drain outlet 54b opens may be any direction perpendicular to the up-down direction Z. For example, the drain outlet 54b may open in the left-right direction Y.

[0051] The drain tube 54 is cylindrical and has an axis extending in the front-rear direction X. The drain tube 54 is aligned with the exhaust end portion 70 in the front-rear direction X. In other words, the axis of the drain tube 54 intersects the axis of the cathode off-gas exhaust tube 63. The drain tube 54 has a drain port 54b that opens into the tank chamber 50a at a first end in the front-rear direction X, and opens to the outside of the tank chamber 50a at a second end. The drain tube 54 protrudes from the side wall outer surface 53a at the second end. In other words, the second end of the drain tube 54 is located away from the side wall outer surface 53a in the front-rear direction X. A drain valve (not shown) is attached to the second end of the drain tube 54. The drain valve is openable and closable. Note that, instead of the drain valve, for example, a removable lid that closes the drain tube 54 may be provided at the second end of the drain tube 54.

[0052] The drain pipe 54 has a drain outlet edge 54a at its first end. The drain outlet edge 54a is the edge of the drain outlet 54b. The drain outlet edge 54a has its entire circumference in a plane perpendicular to the front-to-rear direction X and parallel to the up-down direction Z. The lower end of the drain outlet edge 54a in the up-down direction Z is located a distance H1 from the tank bottom surface 51a. In other words, the shortest distance between the drain outlet edge 54a and the tank bottom surface 51a is distance H1.

[0053] When the drain valve attached to the drain pipe 54 is open, water stored in the water storage tank 50 is discharged outside the water storage tank 50 through the drain outlet 54b. The drain outlet 54b discharges water that is above the tank bottom surface 51a by a distance H1. The water stored in the water storage tank 50 forms a water surface F in the tank chamber 50a. The water surface F is parallel to both the tank bottom surface 51a and the top panel inner surface 52b. In other words, when the height of the water surface F in the tank chamber 50a exceeds the distance H1 and the drain valve is open, the water storage tank 50 discharges the excess amount of water through the drain outlet 54b. When water having a height of the water surface F of the distance H1 is stored in the water storage tank 50, the water surface F is maintained at the height of the water surface F at the distance H1 from the tank bottom surface 51a unless the water is discharged by a method other than draining from the drain outlet 54b. The water is discharged by opening the drain valve periodically according to the amount of water stored in the water storage tank 50.

[0054] <Cathode off-gas exhaust stack> The fuel cell system 10 has a cathode offgas exhaust stack 63. The cathode offgas exhaust stack 63 defines the cathode offgas discharge path 26. That is, the cathode offgas exhaust stack 63 connects the cathode 11c of the fuel cell stack 11 to the water tank 50. In other words, the cathode offgas exhaust stack 63 introduces the cathode offgas discharged from the cathode 11c of the fuel cell stack 11 into the water tank 50.

[0055] The cathode offgas exhaust pipe 63 is connected at a first end to the cathode 11c of the fuel cell stack 11 and at a second end to the water tank 50. The cathode offgas exhaust pipe 63 is made of metal. The cathode offgas exhaust pipe 63 is inserted into the cathode offgas inlet hole 52c. The outer diameter of the cathode offgas exhaust pipe 63 matches the hole diameter of the cathode offgas inlet hole 52c. The cathode offgas exhaust pipe 63 extends in the up-down direction Z in the tank chamber 50a. That is, in the tank chamber 50a, the axis of the cathode offgas exhaust pipe 63 is perpendicular to the axis of the drain pipe 54.

[0056] The cathode offgas exhaust tube 63 has an exhaust end portion 70 at a portion of the cathode offgas exhaust tube 63 in the axial direction that is accommodated in the water storage tank 50. The exhaust end portion 70 is accommodated in the tank chamber 50a. In other words, the cathode offgas exhaust tube 63 has the exhaust end portion 70 that is accommodated in the water storage tank 50. The cathode offgas exhaust tube 63 has an exhaust tube outer peripheral surface 70a and an exhaust tube inner peripheral surface 70b. The cathode offgas exhaust tube 63 has the exhaust end portion 70 on the second end side.

[0057] The cathode off-gas exhaust stack 63 has an exhaust port 71 that opens at an exhaust end 70. The exhaust port 71 opens in a direction from the tank top plate 52 toward the tank bottom plate 51. The exhaust port 71 has an exhaust opening edge 71a as an opening edge. In FIG. 3, an imaginary plane P including the exhaust opening edge 71a is indicated by a two-dot chain line. The imaginary plane P is a plane that is perpendicular to the up-down direction Z. In other words, the imaginary plane P is parallel to the water surface F. Therefore, the imaginary plane P including the exhaust opening edge 71a of the exhaust port 71 is parallel to the tank bottom surface 51a.

[0058] The exhaust opening edge 71a is located below the lower end of the drain port edge 54a in the vertical direction Z. Specifically, when the distance from the tank bottom surface 51a to the imaginary plane P is defined as a distance H2, the exhaust port 71 opens at the exhaust end portion 70 so that the distance H2 is smaller than the distance H1. In other words, the exhaust port 71 opens below the drain port 54b.

[0059] When the water surface F is spaced a distance H1 from the tank bottom surface 51a, the exhaust port 71 opens below the water surface F. That is, the exhaust port 71 opens into the water stored in the water storage tank 50. In other words, the cathode off-gas exhaust tube 63 is housed in the tank chamber 50a so that the second end is submerged in water.

[0060] The cathode off-gas exhaust stack 63 is in contact with the water surface F at both the exhaust stack outer peripheral surface 70a and the exhaust stack inner peripheral surface 70b. The water surface F is divided into an outer water surface F1 that is in contact with the exhaust stack outer peripheral surface 70a and an inner water surface F2 that is in contact with the exhaust stack inner peripheral surface 70b. The outer water surface F1 is in contact with both the exhaust stack outer peripheral surface 70a and the side wall inner surface 53b. The inner water surface F2 is in contact with the exhaust stack inner peripheral surface 70b. In the vertical direction Z, the outer water surface F1 is lower than the inner water surface F2. In other words, the height from the tank bottom surface 51a of the inner water surface F2 is higher than the outer water surface F1.

[0061] <Water surface shape> As shown in FIGS. 3 and 4 , the external water surface F1 contacts the exhaust stack outer peripheral surface 70a at a first contact edge C1. The first contact edge C1 surrounds the exhaust stack outer peripheral surface 70a in the circumferential direction of the cathode offgas exhaust stack 63 and contacts the cathode offgas exhaust stack 63 along the exhaust stack outer peripheral surface 70a. The external water surface F1 is farthest from the tank bottom surface 51a at the first contact edge C1 in the vertical direction Z. In other words, the external water surface F1 is highest at the first contact edge C1. As the external water surface F1 moves away from the exhaust stack outer peripheral surface 70a in the radial direction of the cathode offgas exhaust stack 63 from the first contact edge C1, it becomes a surface that is perpendicular to the vertical direction Z and faces upward. In other words, the contact angle between the exhaust stack outer peripheral surface 70a and the external water surface F1 is an acute angle.

[0062] The inner water surface F2 contacts the exhaust tube inner circumferential surface 70b at a second contact edge C2. The second contact edge C2 is surrounded by the exhaust tube inner circumferential surface 70b in the circumferential direction of the cathode offgas exhaust tube 63 and contacts the cathode offgas exhaust tube 63 along the exhaust tube inner circumferential surface 70b. The inner water surface F2 is farthest from the tank bottom surface 51a in the vertical direction Z at the second contact edge C2. In other words, the inner water surface F2 is highest at the second contact edge C2. As the inner water surface F2 moves away from the exhaust tube inner circumferential surface 70b toward the inside in the radial direction of the cathode offgas exhaust tube 63 from the second contact edge C2, it becomes a surface that is perpendicular to the vertical direction Z and faces upward. In other words, the contact angle between the exhaust tube inner circumferential surface 70b and the inner water surface F2 is an acute angle.

[0063] [Operation of this embodiment] The operation of this embodiment will be described. The fuel cell stack 11 discharges cathode offgas containing water into the water storage tank 50 through the cathode offgas exhaust pipe 63. The water contained in the cathode offgas is stored in the water storage tank 50. The water stored in the water storage tank 50 is periodically discharged from the drain outlet 54b by opening the drain valve until the height of the water surface F reaches the lower end of the drain outlet 54b in the vertical direction Z. The exhaust end 70 opens at the exhaust port 71 which is lower than the drain outlet 54b, and therefore the cathode offgas exhaust pipe 63 has the exhaust port 71 below the water surface F. By opening the cathode offgas exhaust pipe 63 underwater, it blocks the flow path of air from the water storage tank 50 to the fuel cell stack 11.

[0064] [Effects of this embodiment] The effects of this embodiment will be described. (1) The cathode offgas exhaust tube 63 has an exhaust port 71 that opens below the water surface F. Therefore, the exhaust port 71 is sealed by the water in the water storage tank 50 even when the drain valve is open. This prevents air from flowing from the tank chamber 50a into the cathode offgas exhaust tube 63. In other words, the fuel cell system 10 prevents air from flowing into the cathode 11c of the fuel cell stack 11 by opening the cathode offgas exhaust tube 63 underwater. Therefore, the fuel cell system 10 can improve the air sealing performance of the cathode offgas exhaust tube 63 without changing the layout.

[0065] (2) Consider a case where the water surface F in the tank chamber 50a is below the drain port 54b. In this case, for the water in the tank chamber 50a to seal the exhaust port 71, the height of the water surface F must be higher than the exhaust opening edge 71a of the exhaust port 71. For example, if the exhaust end portion 70 is bent within the tank chamber 50a so that the imaginary plane P of the exhaust port 71 is parallel to the sidewall inner surface 53b, the height of the water surface F must be higher than the upper end of the exhaust opening edge 71a. For the same distance from the top panel inner surface 52b to the exhaust end portion 70, the height of the water surface F required to seal in air is lower than when the imaginary plane P is not parallel to the tank bottom surface 51a. Furthermore, if the cathode off-gas exhaust pipe 63 opens in a direction perpendicular to the water surface F, the water in the tank chamber 50a can seal off air flowing into the cathode off-gas exhaust pipe 63 even when the exhaust opening edge 71a of the exhaust port 71 is in contact with the water surface F. As a result, the fuel cell system 10 can seal off air flowing into the cathode off-gas exhaust stack 63 with a smaller amount of water than when the exhaust port 71 is open in a direction not parallel to the water surface F.

[0066] (3) When the exhaust port 71 opens below the water level F in the tank chamber 50a, the outer water surface F1 is highest at the first contact edge C1. In other words, the outer water surface F1 is inclined so as to be highest at the first contact edge C1. In this case, the inner water surface F2 is highest at the second contact edge C2. In other words, the inner water surface F2 is inclined so as to be highest at the second contact edge C2. The increase in height of the outer water surface F1 and the inner water surface F2 at the first contact edge C1 and the second contact edge C2 seals off air that flows into the cathode offgas exhaust tube 63. When the cathode offgas exhaust tube 63 is made of metal, the heights of the first contact edge C1 and the second contact edge C2 from the tank bottom surface 51a are higher than when, for example, the cathode offgas exhaust tube 63 is made of synthetic resin. In other words, when the cathode off-gas exhaust pipe 63 is made of metal, the water surface F around the exhaust port 71 rises higher than when the cathode off-gas exhaust pipe 63 is made of synthetic resin, for example, and therefore air can be sealed off more reliably.

[0067] (4) The water storage tank 50 stores water drained from the diluter 40. Water produced in the fuel cell system 10 is introduced into the water storage tank 50 more efficiently than in a case where the water storage tank 50 does not receive drainage from the diluter 40. As a result, the fuel cell system 10 can easily maintain the water surface F in the tank chamber 50a at a height higher than the drain outlet 54b, compared to a case where the water storage tank 50 does not receive drainage from the diluter 40.

[0068] (5) The fuel cell system 10 is mounted on a fuel cell forklift 100. In the environment in which the fuel cell forklift 100 travels, it is desirable to maintain the road surface, for example, to prevent water from leaking onto the road surface on which the fuel cell forklift 100 travels. In other words, the fuel cell forklift 100 is equipped with a water tank 50 that stores water produced during power generation in the fuel cell stack 11 inside the vehicle body 101. Therefore, the fuel cell system 10 can improve the sealing performance of the cathode off-gas exhaust stack 63 without requiring any changes to the internal layout of the fuel cell forklift 100.

[0069] [Example of change] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0070] The water storage tank 50 and the diluter 40 do not have to be integrated. In this case, the fuel cell system 10 preferably has piping or the like so that water produced in the process of diluting the anode off-gas in the diluter 40 can be introduced into the water storage tank 50.

[0071] The water tank 50 does not have to be made of resin. For example, the water tank 50 may be made of metal. The cathode off-gas exhaust pipe 63 does not have to be made of metal. The cathode off-gas exhaust pipe 63 may be made of any material that allows the first and second contact edges C1, C2 to form acute contact angles with the water surface F.

[0072] The imaginary plane P does not have to be parallel to the tank bottom surface 51a. For example, the imaginary plane P may be perpendicular to the tank bottom surface 51a. In other words, the cathode off-gas exhaust pipe 63 may be bent in the tank chamber 50a and have an exhaust port 71 that opens in a direction perpendicular to the up-down direction Z. In this case, the cathode off-gas exhaust pipe 63 has the exhaust port 71 such that the entire circumference of the exhaust opening edge 71a is below the water surface F.

[0073] The tank bottom plate 51 and the tank top plate 52 do not have to be rectangular. For example, the tank bottom plate 51 and the tank top plate 52 may each be circular. In this case, the water storage tank 50 has a cylindrical shape with the tank chamber 50a formed therein. In this case, the tank side wall 53 is a single cylindrical member having an inner diameter that matches the radius of the tank bottom plate 51.

[0074] The tank bottom plate 51 and the tank top plate 52 may have different shapes. In this case, the tank side wall 53 has a shape that connects the tank bottom plate 51 and the tank top plate 52. The cathode offgas exhaust stack 63 does not have to be cylindrical. For example, the cathode offgas exhaust stack 63 may be in the shape of a square pillar that defines the cathode offgas discharge channel 26 therein.

[0075] The drain pipe 54 and the cathode offgas exhaust pipe 63 do not have to be aligned in the front-rear direction X. In other words, the drain pipe 54 may be located at a different position in the left-right direction Y from the cathode offgas exhaust pipe 63.

[0076] The tank bottom surface 51a does not have to be flat. For example, as shown in FIG. 5, the tank bottom surface 51a may have a first bottom surface 511a and a second bottom surface 512a. The first bottom surface 511a and the second bottom surface 512a each face the top plate inner surface 52b. The first bottom surface 511a is aligned with the exhaust end portion 70 in the vertical direction Z. The second bottom surface 512a is located lower than the first bottom surface 511a in the vertical direction Z. The second bottom surface 512a is located higher than the exhaust port 71 of the exhaust end portion 70. The drain port 54b opens higher than the second bottom surface 512a. In other words, the second bottom surface 512a is located between the first bottom surface 511a and the drain port 54b in the vertical direction Z.

[0077] In this case, the cathode off-gas exhaust tube 63 is located above the first bottom surface 511a and is sealed by the water surface F, which is located above the second bottom surface 512a. Therefore, a smaller amount of water stored in the water storage tank 50 can seal the cathode off-gas exhaust tube 63 compared to when the tank bottom surface 51a does not have the first bottom surface 511a and the second bottom surface 512a. As a result, the fuel cell system 10 can seal the cathode off-gas exhaust tube 63 more easily than when the tank bottom surface 51a does not have the first bottom surface 511a and the second bottom surface 512a.

[0078] The fuel cell stack 11 may be composed of a single fuel cell. The fuel cell system 10 does not have to be mounted on the fuel cell forklift 100. For example, the fuel cell system 10 may be mounted on a stationary power generator. [Explanation of symbols]

[0079] 10...fuel cell system, 11...fuel cell stack as fuel cell, 11c...cathode, 40...diluter, 50...water storage tank, 51a...tank bottom, 53b...inner side wall surface as tank wall, 54b...drain outlet, 63...cathode off-gas exhaust stack as exhaust stack, 70...exhaust end, 71...exhaust port, 71a...exhaust opening edge as opening edge, 511a...first bottom surface, 512a...second bottom surface, P...imaginary plane, Z...up and down direction.

Claims

1. A fuel cell; a water storage tank for storing water generated by the power generation of the fuel cell; an exhaust pipe that introduces cathode off-gas discharged from the cathode of the fuel cell into the water storage tank; A drain outlet is opened in a tank wall surface extending vertically from the tank bottom surface of the water storage tank, The exhaust stack comprises: an exhaust end portion housed in the water tank; an exhaust port opening at the exhaust end, The fuel cell system is characterized in that the exhaust port opens below the drain port.

2. 2. The fuel cell system according to claim 1, wherein an imaginary plane including an opening edge of the exhaust port is parallel to the bottom surface of the tank.

3. 3. The fuel cell system according to claim 1, wherein the exhaust pipe is made of metal.

4. a diluter into which water and anode off-gas produced by the fuel cell flow and which dilutes the anode off-gas; 3. The fuel cell system according to claim 1, wherein the water storage tank is integrated with the diluter and stores water discharged from the diluter.

5. The tank bottom surface is a first bottom surface aligned with the exhaust end portion in the vertical direction; The tank has a second bottom surface which is a surface different from the first bottom surface in the vertical direction, the first bottom surface is located lower than the second bottom surface in the up-down direction, 3. The fuel cell system according to claim 1, wherein the second bottom surface is located above the exhaust port.

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