JP2008091266A - Operation method of fuel cell system - Google Patents

Abstract

Provided is a fuel cell system operating method capable of performing stable power generation in a short time even when starting after stopping a long-time operation.
SOLUTION: A fuel cell 20, a supply source 30 of hydrogen gas supplied to the fuel cell 20, a supply path 74 connecting the supply source 30 and the fuel cell 20, and hydrogen off-gas discharged from the fuel cell 20 are removed. An operation method of the fuel cell system 1 including a circulation path 75 returning to the supply path 74, wherein the hydrogen gas flow path including the supply path 74, the fuel cell 20, and the circulation path 75 is a closed circuit. Hydrogen gas is supplied from a plurality of directions to the fuel cell 20 in the closed circuit.
[Selection] Figure 1

Description

  The present invention relates to a method for operating a fuel cell system including a fuel cell that generates electric power by an electrochemical reaction between an oxidizing gas and a fuel gas.

Conventionally, when the fuel cell system is started after the operation of the fuel cell system is stopped for a long time (for example, 1 hour 30 minutes or more), the fuel gas is circulated while supplying the fuel gas (for example, hydrogen gas) to the fuel cell. A technique is known in which the pump is rotated in reverse for a predetermined time, thereby discharging unnecessary gas remaining in the fuel gas flow path (air that has flowed in after the previous operation is completed) out of the flow path. (For example, see Patent Document 1 below).
JP 2001-114226 A

  However, in the fuel cell system of Patent Document 1, when starting the system, the circuit constituting the flow path of the fuel gas is open (open to the atmosphere). In the vicinity of the outlet, there is a difference in the time required for the fuel gas to reach each part after the system is started.

  That is, the time for the fuel gas flowing into the fuel cell through the channel (open circuit) open to the atmosphere to reach the fuel cell outlet is the fuel gas flowing into the fuel cell through the channel (closed circuit) not open to the atmosphere Is longer than the time to reach the fuel cell inlet. For this reason, the time until the fuel gas reaches the gas flow path in the fuel cell uniformly depends on the arrival time of the fuel gas flowing into the fuel cell through the flow path on the open side of the atmosphere. It takes time before stable power generation can be performed.

  The present invention has been made in view of the above circumstances, and provides a method of operating a fuel cell system capable of performing stable power generation in a short time even when the operation is started after being stopped for a long time. It is aimed.

  To achieve the above object, the present invention provides a fuel cell that receives a gas supply and generates power by an electrochemical reaction, a fuel gas supply source that is supplied to the fuel cell, the supply source, and the fuel cell. An operation method of a fuel cell system, comprising: a supply path to be connected; and a circulation path for returning fuel off-gas discharged from the fuel cell to the supply path, wherein the supply path, the fuel cell, and the circulation The fuel gas flow path including the path is a closed circuit, and the fuel gas is supplied from a plurality of directions to the fuel cell in the closed circuit.

  According to this configuration, the fuel gas flow path including the fuel cell forms a closed circuit, and the fuel cell in the closed circuit is from a plurality of directions (for example, two directions from the inlet side and the outlet side). Since the fuel gas is supplied, the fuel gas reaches the gas flow path in the fuel cell within a short time. As a result, stable power generation can be performed in a short time.

  In the operation method of the fuel cell system according to the present invention, the plurality of directions may include at least two directions from the fuel gas inlet side and from the fuel off gas outlet side of the fuel cell.

  According to this configuration, the fuel gas can be quickly supplied to the fuel off-gas outlet side where the fuel gas is difficult to spread. The fuel gas may be supplied from between the fuel gas inlet side and the fuel off gas outlet side of the fuel cell.

  In the operation method of the fuel cell system according to the present invention, the fuel gas may be supplied from the plurality of directions to the fuel cell for a predetermined time.

  According to this configuration, stable normal power generation can be started promptly after the predetermined time has elapsed.

  According to the present invention, stable power generation can be performed within a short time even when the operation is started after being stopped for a long time.

  Next, an embodiment of the operation method of the fuel cell system according to the present invention will be described. Hereinafter, the case where this fuel cell system is applied to an in-vehicle power generation system of a fuel cell vehicle will be described. However, the present invention is not limited to such an application example, and is applicable to any moving body such as a ship, an aircraft, a train, and a walking robot. For example, the present invention can be applied to a stationary power generation system in which a fuel cell is used as a power generation facility for a building (house, building, etc.).

  In the fuel cell system 1 shown in FIG. 1, air as an oxidizing gas is supplied to an air supply port of the fuel cell 20 via an air supply path 71. The air supply path 71 is provided with an air filter A1 that removes particulates from the air, a compressor A3 that pressurizes the air, and a humidifier A21 that adds required moisture to the air. The air filter A1 is provided with an air flow meter (flow meter) (not shown) that detects the air flow rate. The compressor A3 is driven by the motor M.

  The air off gas discharged from the fuel cell 20 is discharged to the outside through the exhaust path 72. The exhaust path 72 is provided with a pressure adjustment valve A4 and a humidifier A21. The pressure adjustment valve A4 functions as a pressure regulator (pressure reduction) that sets the air pressure supplied to the fuel cell 20.

  Hydrogen gas as the fuel gas is supplied from the hydrogen supply source 30 to the hydrogen supply port of the fuel cell 20 through the hydrogen supply path 74. The hydrogen supply source 30 corresponds to, for example, a high-pressure hydrogen tank, but may be a so-called fuel reformer, a hydrogen storage alloy, or the like.

  In the hydrogen supply path 74, a shutoff valve H100 that supplies or stops supplying hydrogen from the hydrogen supply source 30, a hydrogen pressure regulating valve H9 that adjusts the supply pressure of hydrogen gas to the fuel cell 20 by reducing the pressure, and the fuel cell 20 A shutoff valve H21 for opening and closing between the hydrogen supply port and the hydrogen supply path 74 is provided. As the hydrogen pressure regulating valve H9, for example, a pressure regulating valve that performs mechanical pressure reduction can be used. However, a valve whose opening degree is linearly or continuously adjusted by a pulse motor may be used.

  The hydrogen gas that has not been consumed in the fuel cell 20 is discharged as hydrogen offgas (fuel offgas) to the hydrogen circulation path 75 and returned to the downstream side of the hydrogen pressure regulating valve H9 in the hydrogen supply path 74. The hydrogen circulation path 75 includes a gas-liquid separator H42 that recovers moisture from the hydrogen off-gas, a drain valve H41 that recovers the recovered product water in a tank (not shown) outside the hydrogen circulation path 75, and a hydrogen pump that pressurizes the hydrogen off-gas. H50 is provided.

  The shut-off valve H21 closes the anode side of the fuel cell 20. The operation of the hydrogen pump H50 is controlled by the control unit 50 and supplies hydrogen gas to the fuel cell 20 through the hydrogen supply path 74, or supplies hydrogen gas to the fuel cell 20 through the hydrogen supply path 74 and the hydrogen circulation path 75. Is possible. The hydrogen off-gas merges with the hydrogen gas in the hydrogen supply path 74 and is supplied to the fuel cell 20 for reuse. The shut-off valve H21 is driven by a signal from the control unit 50.

  The hydrogen circulation path 75 is connected to the exhaust path 72 on the downstream side of the humidifier A21 by the purge flow path 76 via the discharge control valve H51. The discharge control valve H51 is an electromagnetic shut-off valve, and operates according to a command from the control unit 50, whereby the hydrogen off-gas is discharged (purged) together with the air off-gas discharged from the fuel cell 20. By intermittently performing this purging operation, it is possible to prevent the cell voltage from decreasing due to an increase in the impurity concentration in the hydrogen gas.

  A cooling path 73 for circulating the cooling water is provided at the cooling water inlet / outlet of the fuel cell 20. The cooling path 73 is provided with a radiator (heat exchanger) C2 that radiates heat of the cooling water to the outside, and a pump C1 that pressurizes and circulates the cooling water. The radiator C2 is provided with a cooling fan C13 that is rotationally driven by a motor.

  The fuel cell 20 is configured as a fuel cell stack in which a required number of single cells that receive supply of hydrogen gas and air and generate electric power through an electrochemical reaction are stacked. The electric power generated by the fuel cell 20 is supplied to a power control unit (not shown). The power control unit consists of an inverter that supplies electric power to the drive motor of the vehicle, an inverter that supplies electric power to various auxiliary devices such as a compressor motor and a hydrogen pump motor, A DC-DC converter or the like that supplies power to the motors from the power storage means is provided.

  The control unit 50 is configured by a control computer system having a known configuration such as a CPU, ROM, RAM, HDD, input / output interface, display, and the like, and a required load such as an accelerator signal of a vehicle (not shown) and each part of the fuel cell system 1 Control information is received from these sensors (pressure sensor, temperature sensor, flow sensor, output ammeter, output voltmeter, etc.), and the operation of valves and motors in each part of the system is controlled.

  When starting the fuel cell system 1 configured as described above, the discharge control valve H51 is operated to close the purge flow path 76. In addition, the hydrogen pump H50 is operated in reverse to the normal operation, and the fuel gas is conveyed toward the fuel cell 20 through the hydrogen supply path 74 and the hydrogen circulation path 75. When the purge flow path 76 is closed, as shown in FIG. 2, the hydrogen supply path 74, the fuel cell 20, and the hydrogen circulation path 75 form a closed circuit.

  In this closed circuit, the fuel gas supplied from the hydrogen supply source 30 flows from the hydrogen supply source 30 while flowing into the inlet 20a of the fuel cell 20 through the hydrogen supply path 74, as indicated by the solid arrow. The fuel gas flows into the outlet 20b of the fuel cell 20 through a part of the hydrogen supply path 74 and the hydrogen circulation path 75 without leaking out of the closed circuit, as indicated by a broken line arrow.

  At this time, since the fuel gas flow path including the fuel cell 20 forms a closed circuit, compared with the case where the fuel gas flow path is an open circuit, hydrogen gas is not leaked to the outside of the closed circuit. The time until the fuel cell gas reaches the outlet 20b of the fuel cell 20 through a part of the supply channel 74 and the hydrogen circulation channel 75 is shortened.

  FIG. 3 shows changes in the concentration of the fuel gas at the inlet 20a of the fuel cell 20 and the concentration of the fuel gas at the outlet 20b of the fuel cell 20 after the fuel cell system 1 is started. As can be seen from FIG. 3, according to the operation method of the fuel cell system 1 according to this embodiment, the gas concentration at the outlet 20b of the fuel cell 20 is substantially the same as the gas concentration at the inlet 20a of the fuel cell 20. Settling to a predetermined value.

  On the other hand, in the case of the conventional operation method of the fuel cell system, the gas concentration at the outlet 20b of the fuel cell 20 becomes a predetermined value after a slight delay after the gas concentration at the inlet 20a of the fuel cell 20 has settled to the predetermined value. Calm down.

  As described above, according to the operation method of the fuel cell system 1 according to the present embodiment, the time until the fuel gas reaches the outlet 20b of the fuel cell 20 through part of the hydrogen supply path 74 and the hydrogen circulation path 75, Since the time until the fuel gas reaches the inlet 20a of the fuel cell 20 through the hydrogen supply path 74 is substantially the same, the time until the fuel gas reaches the fuel cell 20 uniformly becomes shorter than before.

  As a result, even when the operation of the fuel cell system 1 is stopped for a long time and started, stable power generation can be performed within a short time.

1 is a schematic view showing an embodiment of a fuel cell system according to the present invention. It is a schematic diagram which shows the closed circuit of the fuel gas flow path constructed | assembled in the fuel cell system of FIG. It is a graph which shows the relationship between the hydrogen gas density | concentration in the fuel gas inlet side and fuel off-gas outlet side of a fuel cell, and passage of time after starting a system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 20 ... Fuel cell, 30 ... Hydrogen supply source, 74 ... Hydrogen supply path, 75 ... Hydrogen circulation path, 76 ... Purge flow path, H50 ... Hydrogen pump

Claims (3)

A fuel cell that receives a gas supply and generates electric power through an electrochemical reaction, a supply source of fuel gas supplied to the fuel cell, a supply path that connects the supply source and the fuel cell, and an exhaust from the fuel cell A circulation path for returning the fuel off-gas to the supply path,
A fuel cell comprising a step of supplying a fuel gas from a plurality of directions to the fuel cell in the closed circuit after the fuel gas flow path including the supply path, the fuel cell, and the circulation path is a closed circuit. How to operate the system.   2. The method of operating a fuel cell system according to claim 1, wherein the plurality of directions include at least two directions from a fuel gas inlet side and a fuel off-gas outlet side of the fuel cell.   The operation method of the fuel cell system according to claim 1 or 2, wherein the fuel gas is supplied to the fuel cell from the plurality of directions for a predetermined time.

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