JP2008311160A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell structure and a fuel cell system capable of quickly and surely discharging water inside a manifold, regarding a fuel cell. <P>SOLUTION: A plurality of discharge ports are arranged on the manifold formed along a laminating direction of a cell laminate. When water is to be discharged from the manifold, it is inferred as to which of the plurality of discharge ports is at the vertically lowest portion, circulation of the other discharge ports are limited, while making the discharge port at the vertically lowest portion circulatable; and the water in the manifold is discharged from the discharge port at the vertically lowest portion. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system that receives a reaction gas and generates power chemically, and more particularly to a fuel cell system that improves the drainage of liquid present in a manifold.

  Along with power generation by the fuel cell, in-plane gas flow paths and manifolds arranged around the membrane electrode assembly (MEA) of the fuel cell collect liquid such as generated water generated by power generation. . For this reason, it is necessary to discharge the liquid in the in-plane flow path and the manifold out of the fuel cell.

  Therefore, a technique is disclosed in which when the fuel cell is stopped, a dry gas is supplied to the fuel cell to dry the inside of the fuel cell (see Patent Document 1).

  Further, a technique is disclosed in which discharge ports are provided at both ends of the lower part of the casing of the fuel cell so that drainage can be performed from below the fuel cell when the fuel cell is inclined (see Patent Document 2).

JP 2004-111196 A JP 2003-92130 A

  The manifold is drained during fuel cell power generation or when the operation of the fuel cell is terminated. The reason for performing power generation is that water accumulates in the manifold, which hinders the flow of the reaction gas and may cause a decrease in power generation performance. The reason why the operation is terminated is that if water is left in the manifold for a long period of time, a problem may occur due to freezing of the water. For example, if the fuel cell is started next time with the ice in the manifold and the internal temperature rises, the thermal expansion of the members constituting the fuel cell is hindered in the portion where the ice is present, and the size of the surrounding portion is reduced. It is considered that a gap is generated due to the difference, and the reaction gas leaks. Therefore, it is required to drain the water so that the flow of the reaction gas is not hindered during the operation of the fuel cell and to the extent that the thermal expansion of the peripheral members is not hindered even when the operation is frozen.

  In this regard, since water exists as a liquid in the manifold, there is a problem that it takes a lot of time to dry or discharge the water with gas. The configuration of providing the discharge ports at both ends of the discharge manifold as described in Patent Document 2 is effective in terms of discharging the liquid staying at the lower portion of the manifold. However, as shown in FIG. 7, in this technique, one of the discharge ports 104 and 105 (the discharge port 104) is not provided with the on-off valve 106, and gas is discharged when draining from the discharge port 105. The fuel leaks from the fuel cell 104 to the outside of the fuel cell. For this reason, there is a problem that it is impossible to supply gas for promoting drainage, and draining takes time.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel cell system capable of quickly discharging water in the manifold.

  In order to solve the above problems, a fuel cell system according to the present invention is configured by stacking a separator and a membrane electrode assembly having a power generation unit, and generates power by receiving supply of fuel gas and oxidizing gas as reaction gases. A fuel cell stack, a supply manifold that passes through the stack in the stacking direction and supplies a reaction gas to the power generation unit, and a discharge that passes through the stack in the stacking direction and receives off-gas discharged from the power generation unit A plurality of discharge passages provided outside the laminate and connected to the discharge manifold at different positions to receive off-gas discharged from the discharge manifold, and the plurality of discharge passages, respectively. A flow restricting means capable of restricting the flow of fluid in the exhaust manifold, and the plurality of discharge flow paths when it is determined that drainage in the discharge manifold is necessary. A control means for controlling the flow restricting means so that the discharge manifold having a connection portion with the discharge manifold can flow through the lowest discharge channel in the vertical direction and restrict the flow of the other discharge flow paths. It is characterized by having.

  In the fuel cell system according to the present invention, the discharge channel may include an estimation unit that estimates which of the portions connected to the discharge manifold is the lowest vertical portion. In this case, the plurality of discharge flow paths may include a discharge flow path connected to the discharge manifold at one end in the stacking direction of the stacked body and a discharge flow path connected at the other end. In this case, the estimating means can be an inclination detecting means for detecting the inclination of the laminated body with respect to the horizontal plane.

  Further, in the fuel cell system of the present invention, the plurality of discharge passages may be connected to the manifold at positions different from each other in the vertical direction in the initial posture where the fuel cell is installed.

  In the fuel cell system described above, the control means is capable of distributing all the distribution restriction means when the fuel cell is generating power and it is not determined that the drainage in the drainage manifold is necessary. It may be controlled.

  According to the present invention, when it is determined that drainage is necessary, among the plurality of discharge channels, the discharge channel connected to the discharge manifold at the bottom in the vertical direction can be circulated, and other channels Distribution is restricted. Since the liquid existing in the manifold is accumulated in the vertical lower part in the manifold, the liquid is efficiently drained by being discharged from the lowermost flow path. Moreover, it is possible to suppress the gas inside the fuel cell from being discharged by restricting the flow of the flow path other than the lowest part.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram showing a schematic configuration of a fuel cell stack 10 according to the present embodiment, and FIG. 2 is a plan view of the membrane electrode assembly according to the present embodiment. The fuel cell laminate is formed by laminating cells comprising a membrane electrode assembly shown in FIG. 2 and a separator. FIG. 1 is a view of the stacked body as viewed from the arrow side in FIG. 2, and is a projection so as to clearly show the positional relationship between an anode gas supply manifold 14a and an anode gas discharge manifold 15a described later.

  The fuel cell stack 10 is formed by stacking a plurality of unit cells 12 including a separator and a membrane electrode assembly having a power generation unit, and sandwiching the outside between end plates 13a and 13b. The fuel cell generates power by an electrochemical reaction between oxygen and hydrogen in the air, and air and hydrogen are supplied from the outside of the fuel cell stack 10 during power generation. Specifically, hydrogen is supplied from the hydrogen tank such as a high-pressure tank provided outside to the inside of the stacked body through the hydrogen supply channel 14b. After that, it is distributed to each cell 12 through the anode gas supply manifold 14a provided in the laminated body. Air is supplied to the cell 12 through an oxidizing gas supply channel (not shown) and a cathode gas supply manifold on the oxidizing gas side. Note that air in the present embodiment corresponds to an example of the oxidizing gas recited in the claims, and hydrogen corresponds to an example of the fuel gas.

  When hydrogen and oxygen are supplied to the cell 12 of the fuel cell, a power generation reaction represented by the following formula (1) occurs near the anode of the power generation unit and the following formula (2) occurs near the cathode. Power generation is performed in accordance with the power generation reaction of Formulas (1) and (2), and water is generated near the cathode. A part of the generated water diffuses to the anode side through the electrolyte membrane, and a part thereof becomes a liquid in the manifold.

2H2 → 4H ++ 4e− (1)
O2 + 4H ++ 4e− → 2H2O (2)

  The hydrogen gas after the reaction (hereinafter referred to as anode off gas) flows from the anode discharge manifold 15a through the anode off gas discharge passages 16 and 17 to a circulation passage, a combustion apparatus / diluter, etc. (not shown). In this embodiment, the anode off-gas discharge passages 16 and 17 are connected to the discharge manifold 15a at both ends of the anode gas discharge manifold 15a. The anode off-gas discharge passages 16 and 17 join at the downstream portion and communicate with the circulation passage and the like through one discharge pipe 15b. To do.

  At least a part of the anode off-gas discharge channels 16 and 17 is provided with means for suppressing the electrical conductivity of the pipes constituting the channels. For example, at least a part of the pipes constituting the anode off gas discharge channels 16 and 17 is made of resin. In the fuel cell, a potential difference is generated in the stacking direction. Therefore, when the anode offgas discharge channel is connected to the discharge manifold at a position different in the stacking direction, it is preferable to prevent a short circuit by such a configuration.

  The anode off gas discharge channels 16 and 17 are provided with valves 21 and 22 that can be opened and closed, respectively. The valves 21 and 22 are controlled to be opened and closed by the ECU 30. The exhaust manifold 15a corresponds to the exhaust manifold, the anode off-gas exhaust passages 16, 17 correspond to the exhaust passage, the valves 21, 22 correspond to the flow restricting means, and the ECU 30 corresponds to the control means as an example. Hereinafter, the anode off-gas discharge channel may be referred to as a discharge channel, and the anode discharge manifold may be referred to as a discharge manifold.

  FIG. 2 is a plan view of the membrane electrode assembly having the power generation unit 14. In the plane, there are an opening 24a corresponding to the anode gas supply manifold 14a, an opening 24b corresponding to the anode discharge manifold, and openings 29a and 29b corresponding to the supply manifold or discharge manifold on the cathode side. By alternately laminating separators having openings similar to the membrane electrode assemblies, a fuel cell stack having a manifold penetrating in the stacking direction is formed.

  In addition, as shown in FIG. 1, the fuel cell system of the present embodiment includes an inclination detection unit 11. As the tilt detection means, a mechanical gyro, an optical gyro, or the like can be used. The inclination detection means detects the inclination of the stacked body with respect to the horizontal plane, and thereby estimates which of the discharge flow paths 16 and 17 is in the vertical lower part. In the present embodiment, the inclination detection unit 11 is provided adjacent to the laminate, but the installation location of the inclination detection unit 11 is not limited to the vicinity of the laminate. For example, when it is mounted on a vehicle, the inclination of the laminated body corresponds to the inclination of the entire vehicle. The inclination detection unit 11 corresponds to an estimation unit and an inclination detection unit.

  In the present embodiment, the fuel cell stack 10 is mounted on the vehicle so that the end plate 13a is the front and the end plate 13b is the rear. Therefore, when the vehicle is traveling or stopped on a downhill, the vehicle is front-falling, the laminate 10 is tilted so that the end plate 13a side is lowered, and when the vehicle is uphill, the vehicle is front-up. The laminated body 10 is inclined so that the end plate 13b side is lowered. When the end plate 13a side is lowered, the discharge flow path 17 is a discharge flow path connected to the discharge manifold at the lowest vertical part.

[Process of Embodiment 1]
FIG. 3 is a flowchart in the case where the wastewater treatment is performed when the operation of the fuel cell is stopped in the present embodiment. In the present embodiment, the ECU 30 determines that the wastewater treatment is necessary when the power generation of the fuel cell is stopped. In this embodiment, when the fuel cell is generating power and it is not determined that wastewater treatment is necessary (hereinafter referred to as normal power generation), the valve 21 is open and the valve 22 is closed. Controlled. Therefore, the anode off gas is discharged from the discharge manifold 15a through the discharge flow path 16.

  When the power generation is stopped (S1), the ECU 30 determines that the drainage is necessary, and obtains the inclination information of the laminated body from the inclination detecting means 11 to determine the inclination (S2). When the end plate 13a side is lowered according to the tilt information, the ECU 30 controls the valve 21 to be closed and the valve 22 to be opened (S3). Conversely, when the end plate 13b side is lowered, the ECU 30 controls the valve 21 to be in an open state and the valve 22 to be in a closed state (S4).

  Thereafter, gas for promoting drainage (hereinafter referred to as purge gas) is supplied from the anode supply flow path side (S5). The purge gas is supplied through the anode supply channel / anode supply manifold. The purge gas is supplied for a predetermined time. For example, it may be determined in advance from the relationship between the amount of water allowed to remain in the manifold and the amount of drainage, and stored in storage means such as a memory (not shown). When the time has elapsed, the supply of purge gas is stopped and the opened valve is closed (S6), and the fuel cell 10 is left in this state. When restarting the power generation of the fuel cell, the ECU 30 opens the valve 21 again.

[Effect of Embodiment 1]
FIG. 4 is a schematic view when the end plate 13a side of the laminated body is lowered in the present embodiment. In this case, since the liquid 50 moves to a low position, it exists on the end plate 13a side of the manifold. In this state, it is difficult to discharge the liquid 50 from the discharge channel 16 on the end plate 13b side. In this regard, in the present embodiment, when the inclination detecting means 11 detects that the end plate 13b side is lowered, the liquid 50 is discharged from the discharge channel 17 on the end plate 13b side by opening the valve 17. Therefore, since the water is discharged from the place where the liquid 50 is accumulated, the water is quickly discharged.

  Furthermore, since the valve 16 is closed when supplying the purge gas, the supplied purge gas works to push out the liquid 50, so that the drainage can be performed quickly and the purge gas is prevented from being discharged from the laminate. it can.

  In addition, as purge gas, fuel gas (hydrogen in this embodiment), air, and inert gas (nitrogen etc.) can be used. In the present embodiment, since the purge gas can be prevented from being discharged as described above, it is possible to suppress the deterioration of fuel consumption when the fuel gas is used as the purge gas. Therefore, it is preferable to use the fuel gas as the purge gas from the viewpoint of simplicity of piping.

[Modification 1]
In the first embodiment, the inclination detecting means is used as the estimating means for estimating the discharge flow path whose connecting portion is the lowermost vertical part, but the present invention is not limited to this. For example, means for detecting the weight of residual water may be provided at both ends of the manifold. When the vehicle tilts, the liquid in the manifold flows downward, so that a larger load is applied to the weight sensor on the lower side. Therefore, based on the output of the weight sensor, it can be estimated that the side where the larger weight is detected is on the bottom. Thus, it is sufficient for the estimation means to be able to estimate which of the plurality of discharge channels is connected to the manifold at the vertical bottom.

[Modification 2]
FIG. 5A is a schematic diagram showing the configuration of the second modification. In the present embodiment, two anode discharge channels 26 and 27 are connected to one end of the manifold in the stacking direction. When the vehicle on which the laminated body 10 is mounted is at a substantially horizontal place, the anode discharge flow path 27 is connected to the anode discharge manifold 15a vertically below the anode discharge flow path 26. In the present modification, the anode discharge flow path 27 is present vertically below the anode discharge flow path 26 regardless of the inclination of the laminated body, unless there is a special situation such as the vehicle rolling over. Therefore, no tilt detection means is provided. In this modification, the anode discharge flow path 27 is a discharge flow path connected to the discharge manifold at the lowest vertical portion of the discharge flow paths.

  In the process of this modification, when it is determined that drainage is necessary, the ECU 30 opens the valve 32 provided in the anode discharge flow path 27 and closes the valve 31 provided in the anode discharge flow path 26. Control. Thereafter, purge gas is supplied, and the valve 32 is closed after a predetermined time has elapsed. Thereby, it can drain using the discharge flow path connected to a discharge manifold in the place near the part where the liquid has accumulated. Further, it is possible to drain the water while suppressing the purge gas from being discharged out of the stacked body.

  In this modified example, as shown in FIG. 5B, the discharge flow path 27 may be connected to the lower surface of the discharge manifold 15a. In this case, in a normal use mode, it is good also as estimating that the discharge flow path 27 is the discharge flow path connected in the lowest part.

[Modification 3]
FIG. 6 is a schematic diagram showing the configuration of the third modification. In the first embodiment and the second modification, a valve (distribution restricting means) is provided for each of the plurality of discharge channels. However, in the fuel cell system of this modification, the plurality of anode discharge channels are provided via the three-way valve 41. It is the structure which merges. When it is determined that drainage is necessary, the ECU 30 controls the three-way valve 41 to distribute the off-gas from the discharge passage connected to the manifold at the lowermost portion to the downstream pipe 15b, so that other discharge passages are provided. Is restricted from flowing to the pipe 15b. Thereby, when draining, the same process as the case where the flow restriction means is provided in each flow path can be performed by one valve. In other words, the flow restricting means is sufficient as long as the flow rate can be made variable for each of the discharge flow paths. good.

[Modification 4]
In the first embodiment, the ECU allows one of the plurality of discharge channels to be distributed during normal operation and restricts the other distribution. However, during normal operation, the ECU controls all the discharge channels to be distributed. Good. That is, when draining, it is sufficient to restrict the flow of the flow path except the discharge flow path connected to the manifold at the bottom, and the mode during normal power generation is not limited. However, if it is possible to circulate through all the discharge passages during normal power generation, the connection area between the manifold and the discharge passages is substantially increased. This is preferable because pressure loss at the connection portion can be reduced.

[Modification 5]
In the first embodiment, the ECU 30 determines that drainage is necessary when the operation of the fuel cell is stopped. However, the present invention is not limited to this. If a large amount of water accumulates in the manifold, the flow of reaction gas used for power generation may be hindered, which may hinder power generation. Therefore, drainage may be performed during power generation. The determination of the necessity of drainage may be based on the power generation duration of the fuel cell, the elapsed time from the previous drainage, the cell voltage of the fuel cell, or the like, or a combination thereof. In any case, a determination criterion may be set in advance so that an amount of liquid that affects the power generation performance of the fuel cell does not remain in the manifold.

[Modification 6]
In Embodiment 1, it applied to the discharge system by the side of an anode. When hydrogen is used as the purge gas on the anode side, it is difficult to drain water in a short time with the prior art because of the low molecular weight and flow rate. It is preferable to apply the invention. However, rapid and reliable drainage is also required in the discharge manifold on the cathode side, and more rapid and reliable drainage is possible by applying the present invention. Therefore, the present invention may be applied to the cathode side or to both sides. Even when applied to the cathode side, the configuration and processing may be the same as those applied to the anode side.

FIG. 1 is a schematic diagram showing the configuration of the first embodiment. FIG. 2 is a plan view showing the membrane electrode assembly of the first embodiment. FIG. 3 is a flowchart showing the processing of the first embodiment. FIG. 4 is a schematic diagram for explaining the operation of the first embodiment. FIG. 5 is a schematic diagram showing the configuration of the second modification. FIG. 6 is a schematic diagram showing the configuration of the third modification. FIG. 7 is a schematic diagram showing the configuration of the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell laminated body 11 Tilt detection means 12 Fuel cell 13 End plate 14 Power generation part 15a Anode offgas discharge manifold 16, 17, 26, 27 Anode offgas discharge flow path 21, 22, 31, 32 Valves 24a, 24b, 29a, 29b Opening 30 ECU
41 Three-way valve 50 Liquid

Claims (6)

A separator and a membrane electrode assembly having a power generation unit are configured to be stacked, and a fuel cell stack that generates power by receiving supply of fuel gas and oxidizing gas as a reaction gas;
A supply manifold that passes through the stack in the stacking direction and supplies a reaction gas to the power generation unit;
A discharge manifold that passes through the stack in the stacking direction and receives off-gas discharged from the power generation unit;
A plurality of discharge passages provided outside the laminate, connected to the discharge manifold at different positions, and receiving off-gas discharged from the discharge manifold, respectively;
A flow restriction means capable of restricting the flow of fluid in each of the plurality of discharge channels;
When it is determined that drainage in the discharge manifold is necessary, among the plurality of discharge passages, the connection portion with the discharge manifold is allowed to flow through the discharge passage that is the lowest in the vertical direction. Control means for controlling the flow restriction means so as to restrict the flow of the discharge channel;
Fuel cell system comprising The fuel cell system according to claim 1,
A fuel cell system further comprising estimation means for estimating which of the connecting portions between the discharge flow path and the discharge manifold is the lowest vertical portion The fuel cell system according to claim 2, wherein
The plurality of discharge flow paths include a discharge flow path connected to the discharge manifold at one end in the stacking direction of the laminate, and a discharge flow path connected at the other end.
Fuel cell system The fuel cell system according to claim 2 or 3,
The estimation means is an inclination detection means for detecting the inclination of the laminate with respect to the horizontal plane. The fuel cell system according to claim 1,
The plurality of discharge passages are connected to the manifold at different positions in the vertical direction in the initial posture where the fuel cell is installed. The fuel cell system according to any one of claims 1 to 4, wherein
When the fuel cell is generating power and the drainage in the drainage manifold is not determined to be necessary, the control means controls all the flow restriction means to be circulated.
Fuel cell system

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