JP4742522B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and is particularly suitable for application to a fuel cell system including a pressure regulating valve that adjusts the pressures of an anode gas and a cathode gas.

  The fuel cell generates electric power by reacting hydrogen supplied to the anode side with oxygen supplied to the cathode side. In such a fuel cell, Japanese Patent Application Laid-Open No. 2003-68334 discloses a technique for adjusting a differential pressure between a hydrogen pressure before supplying the fuel cell and an oxygen pressure before supplying the fuel cell by providing a pressure regulating valve for adjusting the hydrogen pressure. It is disclosed.

JP 2003-68334 A JP 2002-373682 A JP 2002-313395 A JP 2003-203665 A JP 7-271450 A

  In the technique disclosed in Japanese Patent Laid-Open No. 2003-68334, oxygen gas before fuel cell supply is introduced into a pressure regulating valve that regulates the hydrogen pressure in order to obtain a signal pressure. However, since the oxygen gas supplied to the pressure regulating valve contains moisture, when oxygen gas is introduced into the pressure regulating valve, the moisture in the oxygen gas freezes, causing malfunctions in the pressure regulating valve, or by adjusting the moisture. There is a risk of corrosion of the pressure valve and piping.

  The present invention has been made in order to solve the above-described problems. In a system including a pressure regulating valve that adjusts a differential pressure between a hydrogen pressure and an oxygen pressure before supplying a fuel cell, moisture contained in the gas is provided. The purpose is to prevent corrosion, freezing and the like from occurring in the path including the pressure regulating valve.

In order to achieve the above object, a first invention is a fuel cell system,
A fuel cell that receives an anode gas containing hydrogen at the anode and a cathode gas containing oxygen at the cathode to generate power; and
A pressure regulating valve having a reference gas chamber into which the cathode gas is introduced and adjusting the pressure of the anode gas based on the pressure of the cathode gas ;
A water discharge means having a discharge valve provided in a predetermined path including at least the reference gas chamber of the pressure regulating valve , and discharging water from the predetermined path via the discharge valve ;
A communication state in which the cathode inlet side and the cathode outlet side of the fuel cell communicate with each other so as to form a circulation system for supplying the cathode off-gas discharged from the cathode of the fuel cell to the cathode again; A valve capable of switching between a cut-off state in which the inlet side of the cathode and the outlet side of the cathode of the fuel cell are cut off so as not to form the circulation system;
With
When water is discharged from the predetermined path by the water discharging means, the valve is set to the shut-off state .

According to a second invention, in the first invention, the moisture discharging means discharges moisture from the predetermined path when the fuel cell is stopped.

The third invention is the first or second aspect of the invention, prior Symbol moisture discharging means further comprises a gas supply means for feeding the cathode gas to the pressure regulating valve, to discharge the water together with the cathode gas from the exhaust valve It is characterized by that.

According to 1st invention, a water | moisture content can be discharged | emitted from the path | route containing a pressure regulation valve by a water | moisture-content discharge means. Therefore, it is possible to prevent the moisture from being frozen in the path including the pressure regulating valve, and it is possible to prevent the corrosion from occurring in the path including the pressure regulating valve due to the moisture. As a result, the pressure regulating valve can be reliably operated, and the reliability of the fuel cell system can be improved. Furthermore, according to the first invention, when the moisture is discharged, the circulation function is stopped, so that the moisture contained in the cathode off-gas can be prevented from being circulated and sent to the pressure regulating valve. Therefore, when moisture is discharged, it is possible to prevent moisture from being sent to the path including the pressure regulating valve.

According to the second invention, since water is discharged when the fuel cell is stopped, it is possible to prevent the water from freezing due to a temperature drop of the system after the operation is stopped. In addition, since water is discharged when the fuel cell is stopped, it is possible to prevent the pressure adjustment by the pressure regulating valve during operation of the fuel cell from being affected.

According to the third aspect of the present invention, moisture can be discharged together with the gas from the pressure regulating valve by opening the discharge valve while sending the gas to the pressure regulating valve by the gas supply means.

  Several embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram showing a configuration of a fuel cell system 10 according to an embodiment of the present invention. In the present embodiment, the fuel cell 12 is a fuel cell (PEMFC) provided with a solid polymer electrolyte membrane, and is configured by stacking a plurality of cells including an electrolyte membrane, an anode, a cathode, and a separator. Between the anode and the cathode, a flow path for hydrogen gas and oxidizing gas is formed. The electrolyte membrane is a proton-conductive ion exchange membrane formed of a fluorine-based solid polymer material. Both the anode and the cathode are made of carbon cloth woven from carbon fibers. The electrode catalyst that causes an ionic reaction to the gas supplied to the anode and the cathode is formed, for example, by applying a carbon paste carrying platinum (Pt) on the surface of the electrolyte membrane. The separator is formed of a gas-impermeable conductive member such as dense carbon which is compressed by gas and impermeable to gas.

  As shown in FIG. 1, an anode gas channel 14 and a cathode gas channel 16 are introduced into the fuel cell 12. The anode gas flow path 14 is connected to a hydrogen tank 18, and hydrogen-rich anode gas is sent from the hydrogen tank 18 to the anode. In addition, an air pump 20 is provided in the cathode gas flow path 16, and cathode gas as an oxidizing gas containing oxygen is sent to the cathode by driving the air pump 20.

In the anode of the fuel cell 12, when the anode gas is sent, hydrogen ions are generated from hydrogen in the anode gas (H ₂ → 2H ⁺ + 2e ⁻ ), and when the cathode gas is sent, the cathode Oxygen ions are generated from the oxygen and electric power is generated in the fuel cell 12. At the same time, water is generated from the hydrogen ions and oxygen ions at the cathode ((1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O). Most of this water absorbs the heat generated in the fuel cell 12 to become water vapor, which is contained in the cathode offgas and discharged.

  The anode off gas discharged from the anode is discharged from the anode off gas flow path 21. The anode off gas flow path 21 is provided with a hydrogen discharge valve 22 that adjusts the discharge amount of the anode off gas. Further, a processing device 24 for diluting hydrogen in the anode off-gas is provided downstream of the hydrogen discharge valve 22.

  The cathode offgas discharged from the cathode is sent to the cathode offgas flow path 25. An air pressure regulating valve 26 is provided in the cathode off gas passage 25. A flow path 27 branched from the cathode off gas flow path 25 and connected to the cathode gas flow path 16 is provided downstream of the air pressure regulating valve 26. A part of the cathode off-gas is sent from the air pressure regulating valve 26 to the flow path 27 and returned to the cathode gas flow path 16. The flow path 27 is provided with an air circulation valve 28 that adjusts the amount of cathode off-gas returned to the cathode gas flow path 16. As described above, the system of this embodiment includes a circulation system that circulates the cathode off gas and sends it to the cathode of the fuel cell 12.

  A pressure regulating valve 30 is provided in the anode gas flow path 14. A flow path 32 branched from the cathode gas flow path 16 is introduced into the pressure regulating valve 30, and a part of the cathode gas is sent from the flow path 32 to the pressure regulating valve 30.

  The pressure regulating valve 30 has a function of adjusting the pressure of the anode gas based on the pressure of the cathode gas sent from the flow path 32. FIG. 2 is a cross-sectional view showing an example of the structure of the pressure regulating valve 30. As shown in FIG. 2, the internal space of the main body 34 of the pressure regulating valve 30 is partitioned up and down by a diaphragm 36. The space above the diaphragm 36 constitutes a reference gas chamber 38, and the space below the diaphragm 36 constitutes a gas passage 40. A cathode gas is introduced into the reference gas chamber 38 from the flow path 32. An anode gas is sent from the anode gas flow path 14 to the gas passage 40.

  The hydrogen gas passage 40 includes a valve seat 42 at an intermediate portion thereof, and an anode gas is supplied from a hydrogen gas inlet 44 to the gas passage 40 a upstream of the valve seat 42. Further, the gas passage 40 b on the downstream side of the valve seat 42 is connected to the anode gas passage 14 via the gas outlet 46. The diaphragm 36 is configured to be connected and interlocked by a stem 48. The stem 48 protrudes into the gas passage 40a and includes a valve body 50 at the tip thereof. The valve body 50 can be separated from the valve seat 42 from the gas passage 40a side. When the valve body 50 is seated on the valve seat 42, the gas passage 40a and the gas passage 40b are shut off, and the pressure regulating valve 30 is fully closed. It becomes. When the valve body 50 is separated from the valve seat 42, the gas passage 40a and the gas passage 40b communicate with each other, and the pressure regulating valve 30 is opened. FIG. 2 shows a state in which the pressure regulating valve 30 is fully closed.

  The reference gas chamber 38 is provided with a bias setting spring 52 that presses the diaphragm 36 in a direction approaching the gas passage 40, and the spring 52 allows the valve body 50 to pass through the diaphragm 36 and the stem 48. Biasing is performed in a direction away from the valve seat 42.

  According to the pressure regulating valve 30 configured in this manner, the pressure of the hydrogen gas in the gas passage 40b acts on the lower surface of the diaphragm 36, and based on this, an upward force acts on the lower surface of the diaphragm 36, Since the pressure of the air in the reference gas chamber 38 and the pressing force of the spring 52 act on the upper surface of the diaphragm 36, a downward force acts on the upper surface of the diaphragm 36 based on this. The diaphragm 36 moves by being controlled by the difference between the force acting on the upper surface and the force acting on the lower surface. That is, when the force acting on the lower surface of the diaphragm 36 is larger than the force acting on the upper surface, an upward force acts on the diaphragm 36 to operate the valve body 50 in a direction approaching the valve seat 42 (that is, a valve closing direction). When the force acting on the lower surface of the diaphragm 36 becomes smaller than the force acting on the upper surface, a downward force acts on the diaphragm 36 in the direction in which the valve body 50 is separated from the valve seat 42 (ie, the valve opening direction). Operate.

  Thus, according to the pressure regulating valve 30, the supply state of the anode gas to the fuel cell 12 can be controlled based on the pressure of the cathode gas supplied into the reference gas chamber 38. Accordingly, by appropriately adjusting the pressing force of the spring 52, the differential pressure between the pressure of the cathode gas and the pressure of the anode gas supplied to the fuel cell 12 can be adjusted to a desired value.

  Thereby, the pressure difference between the pressure of the cathode gas supplied to the fuel cell 12 and the pressure of the anode gas can be set within an allowable range. In a system in which the pressure of the cathode gas and the pressure of the anode gas are desired to be substantially constant, the pressure of the cathode gas and the pressure of the anode gas supplied to the fuel cell 12 can be set to substantially the same value. Thus, the pressures of the cathode gas and the anode gas supplied to both sides of the electrolyte membrane can be made equal. Therefore, it is possible to suppress the occurrence of a problem in the electrolyte membrane due to the pressure difference between the cathode gas and the anode gas, and the reliability of the fuel cell 12 can be improved.

  Incidentally, as described above, since moisture is generated at the cathode of the fuel cell 12, the cathode off-gas discharged from the cathode contains moisture. Therefore, the cathode gas sent to the fuel cell 12 can be humidified in advance by returning the cathode off-gas containing moisture to the cathode gas flow path 16 by the air circulation valve 28, and the reaction efficiency in the fuel cell 12 can be improved.

  On the other hand, since the cathode gas is sent from the flow path 32 to the pressure regulating valve 30, the moisture contained in the cathode off gas is also sent from the flow path 32 to the pressure regulating valve 30. In this case, moisture accumulates in the signal chamber 38 of the pressure regulating valve 30, and the water freezes when the temperature is below freezing, which may impair the function of the pressure regulating valve 30. It is also assumed that the components constituting the pressure regulating valve 30 and the piping of the flow path 32 are corroded by moisture.

  For this reason, in the system of the present embodiment, as shown in FIG. 2, a discharge valve 54 for discharging moisture from the reference gas chamber 38 is provided. Then, by opening the discharge valve 54 with the air pump 20 activated, air and moisture can be forcibly discharged from the flow path 32 and the reference gas chamber 38. Thereby, it can suppress that a water | moisture content accumulates in the flow path 32 and the reference | standard gas chamber 38, and generation | occurrence | production of corrosion, freezing, etc. can be suppressed.

  The timing for opening the discharge valve 54 is preferably, for example, when the fuel cell system 10 is stopped. When the system is stopped, the discharge valve 54 is opened while the air pump 20 is operated. Thereby, the water | moisture content which remains in the flow path 32 and the pressure regulation valve 30 at the time of a system stop can be discharged | emitted, and it can suppress that a water | moisture content freezes after a system stop. Further, by closing the discharge valve 54 during normal operation, the function of the pressure regulating valve 30 can be exhibited.

  Further, the discharge valve 54 may be opened when the system is activated. In this case, when the system is started, the discharge valve 54 is opened while the air pump 20 is operated. Thereby, moisture can be discharged from the flow path 32 and the reference gas chamber 38 before starting normal operation.

  When opening the discharge valve 54 and discharging water, it is preferable to close the air circulation valve 28. Thereby, it can suppress that the water | moisture content in cathode off gas is supplied to the flow path 32 and the pressure regulation valve 30 from the cathode gas flow path 16, and only the dry air can be sent to the pressure regulation valve 30. Therefore, moisture can be reliably discharged from the flow path 32 and the reference gas chamber 38.

  As described above, in the system according to the present embodiment, by opening the discharge valve 54, the flow path 32 and the pressure regulating valve 30 can be scavenged and the water can be discharged. Can be sent to the pressure regulating valve 30. Therefore, the cathode gas containing water just before being supplied to the fuel cell 12 can be sent to the pressure regulating valve 30 as the reference gas. As a result, the pressure loss and time delay generated between the cathode gas sent to the pressure regulating valve 30 and the cathode gas supplied to the fuel cell 12 can be minimized, and the cathode supplied to the fuel cell 12 can be minimized. The pressure of the anode gas can be adjusted based on a gas having approximately the same pressure as the gas. Therefore, the differential pressure between the cathode gas and the anode gas in the fuel cell 12 can be controlled with higher accuracy.

  FIG. 3 is a schematic diagram showing an example in which the present invention is applied to a system including a humidifier 56 for humidifying the cathode gas. In the system of FIG. 3, a humidifier 56 is provided downstream of the air pump 20 in the cathode gas flow path 16. A cathode off-gas channel 25 is introduced into the humidifier 56, and moisture in the cathode off-gas is sent to the cathode gas channel 16 by the humidifier 56 to humidify the cathode gas. Further, in the system of FIG. 3, a bypass passage 17 that branches from the cathode gas passage 16 and bypasses the humidifier 56, and a three-way valve 19 that controls the gas flow to the bypass passage 17 are provided. Other configurations are the same as those of the system of FIG.

  In the system of FIG. 3, the state of the three-way valve 19 is set so that the cathode gas is sent from the air pump 20 to the humidifier 56 during normal operation. On the other hand, when the discharge valve 54 is opened to discharge moisture from the pressure regulating valve 30 and the flow path 32, the state of the three-way valve 19 is set so that the cathode gas flows into the bypass flow path 17. Thereby, when discharging | emitting water | moisture content, it can suppress that the gas containing a water | moisture content is sent to the flow path 32 and the pressure regulation valve 30 from the humidifier 56, and water | moisture content is discharged | emitted reliably from the flow path 32 and the pressure regulation valve 30. be able to.

  Thus, in a system including the humidifier 56 instead of the cathode gas circulation system, a discharge valve 54 that discharges moisture from a path including the pressure regulating valve 30 may be provided. Thereby, the occurrence of corrosion and freezing due to moisture can be suppressed.

  As shown in FIG. 4, a bypass flow path 64 and a three-way valve 66 may be provided in the cathode off gas flow path 25. In this case, when the discharge valve 54 is opened and water is discharged from the pressure regulating valve 30 and the flow path 32, the state of the three-way valve 66 is set so that the cathode off gas flows to the bypass flow path 64 side and does not flow to the humidifier 56. To do. As a result, the supply of moisture from the humidifier 56 to the cathode gas channel 16 can be stopped, and the gas containing moisture is sent from the humidifier 56 to the channel 32 and the pressure regulating valve 30 as in the case of FIG. Can be prevented.

  3 and 4, even if the cathode gas is sent from the flow path 32 to the pressure regulating valve 30 without providing the bypass flow paths 17 and 64, the pressure regulating valve is opened by opening the discharge valve 54. It is possible to drain moisture from the path containing 30. Therefore, in FIGS. 3 and 4, the system may be configured without providing the bypass channels 17 and 64 and the three-way valves 19 and 66.

  FIG. 5 shows a system in which the anode gas is introduced into the reference gas chamber 38 of the pressure regulating valve 30 and the supply of the cathode gas is controlled based on the pressure of the anode gas. In this system, the anode off gas passage 21 and the anode gas passage 14 are connected by a passage 58, and the anode off gas is returned to the anode gas passage 14 by a pump 60 provided in the passage 58 and supplied to the anode of the fuel cell 12. Constitutes a circulating system.

  As described above, the system of the present embodiment uses the anode circulation system fuel cell system for increasing the anode gas utilization efficiency by circulating the anode off gas, and the use of the fuel gas by keeping the fuel gas supplied to the fuel cell inside the fuel cell. The present invention can be applied to an anode dead end type fuel cell system for improving efficiency.

  In the system of FIG. 5, a flow path 62 branched from the anode gas flow path 14 is provided, and the flow path 62 is introduced into the reference gas chamber 38 of the pressure regulating valve 30. On the other hand, the cathode gas channel 16 is introduced into the gas channel 40 of the pressure regulating valve 30. Therefore, the pressure of the cathode gas supplied to the fuel cell 12 can be adjusted to a desired value based on the pressure of the anode gas sent to the reference gas chamber 38.

  The anode gas supplied to the fuel cell 12 may also contain moisture. When the anode gas is supplied to the reference gas chamber 38 of the pressure regulating valve 30, the cathode gas is supplied to the reference gas chamber 38 in the same manner as when the cathode gas is supplied to the reference gas chamber 38. Corrosion, freezing, etc. may occur. In the system of FIG. 5 as well, by providing the discharge valve 54 that discharges moisture from the pressure regulating valve 30, the moisture contained in the anode gas causes corrosion, freezing, and the like in the flow path 62 and the pressure regulating valve 30. Can be suppressed.

  In the example of FIG. 5, a processing device 64 is provided downstream of the discharge valve 54. The processing device 64 is a device that performs a predetermined process in order to avoid that hydrogen in the anode gas discharged from the discharge valve 54 is discharged into the atmosphere as it is. The hydrogen gas discharged from the discharge valve 54 is subjected to processing such as dilution by the processing device 64 and then discharged to the atmosphere.

  FIG. 6 shows an example in which the processing device 24 and the processing device 64 are configured in common in the system of FIG. According to the system shown in FIG. 5, the fuel cell system 10 can be simply configured because only one device is required to process hydrogen in the anode gas. 5 and 6 exemplifies a system including a circulation system for circulating the anode gas, but the anode gas may be exhausted without being circulated similarly to FIG.

  As described above, according to the present embodiment, since the discharge valve 54 for discharging moisture from the pressure regulating valve 30 is provided, the water accumulated in the path including the pressure regulating valve 30 and the flow path 32 can be surely discharged. It becomes possible. Therefore, it is possible to prevent moisture from freezing in the flow path 32 and the pressure regulating valve 30, and it is possible to prevent corrosion due to moisture. Thereby, the pressure regulating valve 30 can be reliably operated, and the reliability of the fuel cell system 10 can be improved.

It is a mimetic diagram showing the composition of the fuel cell system concerning one embodiment of the present invention. It is sectional drawing which shows an example of the structure of a pressure regulation valve. It is a schematic diagram which shows the example which applied this invention to the system provided with the humidifier for humidifying cathode gas. It is a schematic diagram which shows the example which provided the bypass flow path and the three-way valve in the cathode offgas flow path. It is a schematic diagram showing a system for introducing an anode gas into a reference gas chamber of a pressure regulating valve and controlling the supply of cathode gas based on the pressure of the anode gas. FIG. 6 is a schematic diagram illustrating an example in which hydrogen treatment apparatuses are configured in common in the system of FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell system 12 Fuel cell 20 Air pump 24,64 Processing device 27 Flow path 28 Air circulation valve 30 Pressure regulating valve 32, 62 Flow path 38 Reference gas chamber 54 Discharge valve

Claims (3)

A fuel cell that receives an anode gas containing hydrogen at the anode and a cathode gas containing oxygen at the cathode to generate power; and
A pressure regulating valve having a reference gas chamber into which the cathode gas is introduced and adjusting the pressure of the anode gas based on the pressure of the cathode gas ;
A water discharge means having a discharge valve provided in a predetermined path including at least the reference gas chamber of the pressure regulating valve , and discharging water from the predetermined path via the discharge valve ;
A communication state in which the cathode inlet side and the cathode outlet side of the fuel cell communicate with each other so as to form a circulation system for supplying the cathode off-gas discharged from the cathode of the fuel cell to the cathode again; A valve capable of switching between a cut-off state in which the inlet side of the cathode and the outlet side of the cathode of the fuel cell are cut off so as not to form the circulation system;
With
The fuel cell system according to claim 1, wherein when the moisture is discharged from the predetermined path by the moisture discharging means, the valve is in the shut-off state . Before Symbol water discharge means, the fuel cell system according to claim 1, characterized in that for discharging water from said predetermined path during operation stop of the fuel cell. Before SL moisture discharging means further comprises a gas supply means for feeding the cathode gas to the pressure regulating valve,
The fuel cell system according to claim 1 or 2, wherein moisture is discharged together with the cathode gas from the discharge valve.

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