JP2009211837A - Fuel cell and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell capable of processing fuel exhaust gas remaining inside a system, at the stopping operation of one of a closed type. <P>SOLUTION: The closed type fuel cell is provided with a fuel cell stack 1 generating power with hydrogen and oxygen, and is endowed with stopping operation of stopping power generation of the fuel cell stack 1, without exhausting hydrogen and oxygen to the outside. Hydrogen system capacity and oxygen system capacity are so set that a ratio of a hydrogen residue volume at beginning of the stopping operation, in the hydrogen system communicating with the fuel cell stack 1 and in which hydrogen can exist to an oxygen residue volume, at beginning of the stopping operation in the oxygen system, communicating with the fuel cell stack 1 and in which oxygen can exist is to be in an equivalent ratio, in the reaction of hydrogen and oxygen. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell and a method for operating the same, and more particularly to a method for stopping a closed fuel cell.

In general, stationary fuel cells are purged and stopped using an inert gas such as nitrogen in order to safely remove the fuel system. During this purging, since a fuel exhaust gas containing unreacted fuel is discharged out of the system, a vent line that can be safely exhausted is provided.
In contrast, in confined special environments such as space equipment and submersibles, the exhaust gas used in the fuel cell reaction cannot be released to the outside, so a closed type fuel cell that circulates and uses the exhaust gas without releasing it to the outside. Used (see Patent Document 1 and Patent Document 2).

JP 2002-313404 A JP 2002-343387 A

  In such a closed type fuel cell, the fuel exhaust gas containing unreacted fuel cannot be released to the atmosphere. Therefore, when the fuel cell is stopped, the treatment of the fuel exhaust gas remaining in the system becomes a problem. .

  The present invention has been made in view of such circumstances, and provides a fuel cell capable of treating fuel exhaust gas remaining in the system during a stop operation of a closed fuel cell, and an operating method thereof. Objective.

In order to solve the above problems, the fuel cell and the operation method thereof of the present invention employ the following means.
That is, the fuel cell according to the present invention includes a fuel cell main body that generates power by using the fuel and the oxidant, and without stopping the fuel and the oxidant to the outside when stopping the power generation of the fuel cell main body. A fuel cell having a stop operation for stopping, wherein the remaining amount of fuel at the start of the stop operation in the fuel space that communicates with the fuel cell body and in which the fuel can exist, and communicates with the fuel cell body In addition, the fuel space and the oxidant remaining amount ratio at the start of the stop operation in the oxidant space where the oxidant can exist are set to the equivalent ratio in the reaction between the fuel and the oxidant. At least one of the volume, pressure and temperature of the oxidant space is set.

According to the gas equation of state, the volume and pressure of the fuel space, and their product are proportional to the amount of fuel remaining in the fuel space. The temperature of the fuel space is inversely proportional to the amount of remaining fuel in the fuel space. Similarly, the volume and pressure of the oxidant space, and the product thereof are proportional to the amount of remaining oxidant in the oxidant space, and the temperature of the oxidant space is inversely proportional to the amount of remaining oxidant.
Therefore, at least one of the volume, pressure, and temperature of the fuel space and / or the oxidant space is appropriately set, and the remaining amount of fuel in the fuel space at the start of the stop operation and the oxidant space at the start of the stop operation If the fuel supply and the oxidant supply are stopped at the start of the stop operation, the ratio of the remaining amount of the oxidant to the remaining amount of the oxidant is determined by self-discharge or an external load. The fuel present in the fuel space and the oxidant present in the oxidant space react to consume the fuel and oxidant according to the equivalence ratio, and eventually the fuel and oxidant are almost completely consumed. Will be.

  Furthermore, in the fuel cell according to an aspect of the present invention, during the stop operation, an inert gas is supplied to the fuel space and the oxidant space so that the pressures of the fuel space and the oxidant space are maintained at predetermined values. It is characterized by doing.

By supplying the inert gas during the stop operation, the pressure in the fuel space and the oxidant space is maintained at a predetermined value, so that after the stop operation, the system is maintained with the replaced inert gas. And soundness is ensured.
The inert gas is preferably maintained at the pressure during the power generation operation. This is because the sealing material can be selected with the same pressure difference design as in the power generation operation.

  Furthermore, in the fuel cell according to another aspect of the present invention, at the start of the stop operation, the fuel space and the oxidant space are closed, and supply of gas to these spaces is stopped.

  By closing the fuel space and the oxidant space at the start of the stop operation and stopping the gas supply to these spaces, the pressure decreases due to the reaction between the fuel and the oxidant existing in these spaces, and finally The reaction proceeds up to the pressure of gas inevitably present (inert gas in fuel and oxidant and water vapor due to moisture present in the space). As a result, the fuel space and the oxidant space are maintained at a pressure equal to or higher than the saturated vapor pressure. According to the present invention, it is not necessary to hold an inert gas for purging or holding pressure, and a simple configuration is realized.

  Furthermore, the fuel cell according to another aspect of the present invention is characterized in that an inert gas having a predetermined pressure is supplied in advance into the fuel space and the oxidant space at the start of the stop operation.

Since the inert gas having a predetermined pressure is supplied in advance into the fuel space and the oxidant space during the stop operation, after the fuel and the oxidant are reacted and consumed, the fuel space and the oxidant space have a predetermined pressure. Inert gas will be left behind. Thereby, after the stop operation, the inside of the system is held by an inert gas having a predetermined pressure, and soundness is ensured.
The supply pressure of the inert gas is preferably set to atmospheric pressure or higher. Thereby, the leak of the system | strain currently hold | maintained can be detected easily, and it is suitable in the case of maintenance.

  Furthermore, in the fuel cell according to the present invention, the inert gas is supplied at the predetermined pressure at the time of start-up when starting the power generation operation.

  Since an inert gas having a predetermined pressure is supplied from the time of start-up, it can be operated under substantially the same pressure condition during start-up, power generation operation, and stop, and stable operation can be realized.

  The fuel cell of the present invention includes a fuel cell main body that generates power using fuel and an oxidant, and stops the fuel and the oxidant without discharging to the outside when stopping the power generation of the fuel cell main body. A fuel cell having a stop operation, wherein, during the stop operation, the remaining amount of fuel in a fuel space that communicates with the fuel cell body and in which the fuel can exist, and communicates with the fuel cell body and the oxidation The fuel and / or the oxidant is supplied to the fuel space and / or the oxidant space so that the ratio of the oxidant remaining amount in the oxidant space in which the oxidant can exist is an equivalent ratio. Features.

  During the stop operation, the fuel and / or the oxidant is set so that the ratio of the remaining amount of fuel in the fuel space and the remaining amount of oxidant in the oxidant space becomes an equivalent ratio in the reaction between the fuel and the oxidant. Is supplied to the fuel space and / or the oxidant space, so that the fuel present in the fuel space reacts with the oxidant present in the oxidant space by self-discharge or external load, according to the equivalent ratio. The fuel and oxidant will be consumed, and eventually the fuel and oxidant will be almost completely consumed.

  Furthermore, according to the fuel cell in one aspect of the present invention, the inert gas is supplied to the fuel space and the oxidant space so that the pressures of the fuel space and the oxidant space are maintained at predetermined values. Features.

By supplying the inert gas during the stop operation, the pressure in the fuel space and the oxidant space is maintained at a predetermined value, so that after the stop operation, the system is maintained with the replaced inert gas. And soundness is ensured.
The inert gas is preferably maintained at the pressure during the power generation operation. This is because the sealing material can be selected with the same pressure difference design as in the power generation operation.

  Furthermore, according to the fuel cell of another aspect of the present invention, at the start of the stop operation, the fuel space or the oxidant space is a closed space, and the smaller one of the fuel or the oxidant in light of the equivalent ratio It is characterized by supplying only.

  By closing the fuel space or oxidant space at the start of the stop operation and supplying only the smaller fuel or oxidant in view of the equivalence ratio, the pressure is increased by the reaction between the fuel and oxidant existing in these spaces. The reaction proceeds to the vapor pressure of the fuel and oxidant. As a result, the fuel and oxidant and the unavoidably existing gas at the saturated vapor pressure are maintained in the fuel space and the oxidant space at negative pressure. According to the present invention, it is not necessary to hold an inert gas for purging or holding pressure, and a simple configuration is realized.

  Furthermore, according to the fuel cell of another aspect of the present invention, an inert gas having a predetermined pressure is supplied in advance into the fuel space and the oxidant space at the start of the stop operation. .

Since an inert gas having a predetermined pressure is supplied in advance to the fuel space and the oxidant space at the start of the stop operation, after the fuel and the oxidant are reacted and consumed, the fuel space and the oxidant space are predetermined. An inert gas of pressure will be left behind. Thereby, after the stop operation, the inside of the system is held with an inert gas, and soundness is ensured.
The supply pressure of the inert gas is preferably set to atmospheric pressure or higher. Thereby, the leak of the system | strain currently hold | maintained can be detected easily, and it is suitable in the case of maintenance.

  Furthermore, according to the fuel cell of the present invention described above, the inert gas is supplied at the predetermined pressure at the time of starting when the power generation operation is started.

  Since an inert gas having a predetermined pressure is supplied from the time of start-up, it can be operated under substantially the same pressure condition during start-up, power generation operation, and stop, and stable operation can be realized.

  Further, the fuel cell operating method of the present invention includes a fuel cell main body that generates power with fuel and an oxidant, and discharges the fuel and the oxidant to the outside when the power generation of the fuel cell main body is stopped. An operation method of a fuel cell having a stop operation that stops without stopping, the remaining amount of fuel at the start of the stop operation in a fuel space that communicates with the fuel cell body and in which the fuel can exist, and the fuel The ratio of the remaining amount of oxidant at the start of the stop operation in the oxidant space that communicates with the battery body and in which the oxidant can be present is the equivalent ratio in the reaction between the fuel and the oxidant. The stop operation is performed by setting at least one of the volume, pressure and temperature of the fuel space and / or the oxidant space.

According to the gas equation of state, the volume and pressure of the fuel space, and their product are proportional to the amount of fuel remaining in the fuel space. The temperature of the fuel space is inversely proportional to the amount of remaining fuel in the fuel space. Similarly, the volume and pressure of the oxidant space, and the product thereof are proportional to the amount of remaining oxidant in the oxidant space, and the temperature of the oxidant space is inversely proportional to the amount of remaining oxidant.
Therefore, at least one of the volume, pressure, and temperature of the fuel space and / or the oxidant space is appropriately set, and the remaining amount of fuel in the fuel space at the start of the stop operation and the oxidant space at the start of the stop operation If the fuel supply and the oxidant supply are stopped at the start of the stop operation, the ratio of the remaining amount of the oxidant to the remaining amount of the oxidant is determined by self-discharge or an external load. The fuel present in the fuel space and the oxidant present in the oxidant space react to consume the fuel and oxidant according to the equivalence ratio, and eventually the fuel and oxidant are almost completely consumed. Will be.

  Further, the fuel cell operating method of the present invention includes a fuel cell main body that generates power with fuel and an oxidant, and discharges the fuel and the oxidant to the outside when the power generation of the fuel cell main body is stopped. An operation method of a fuel cell having a stop operation that stops without stopping, the remaining amount of fuel in a fuel space that communicates with the fuel cell body and in which the fuel can exist during the stop operation, and the fuel cell body The fuel and / or the oxidant so that the ratio with the remaining amount of oxidant in the oxidant space where the oxidant can exist is equivalent to the fuel space and / or the oxidant space. It is characterized by supplying to.

  During the stop operation, the fuel and / or the oxidant is set so that the ratio of the remaining amount of fuel in the fuel space and the remaining amount of oxidant in the oxidant space becomes an equivalent ratio in the reaction between the fuel and the oxidant. Is supplied to the fuel space and / or the oxidant space, so that the fuel present in the fuel space reacts with the oxidant present in the oxidant space by self-discharge or external load, according to the equivalent ratio. The fuel and oxidant will be consumed, and eventually the fuel and oxidant will be almost completely consumed.

  It is also possible to use a method of reducing the amount of inert gas for purging by flowing a small amount of inert gas at the final stage while using the operation method of the present invention in which fuel and oxidant are almost completely consumed.

  According to the fuel cell and the operating method of the present invention, the fuel exhaust gas remaining in the system during the stop operation of the fuel cell can be processed without purging outside. Therefore, it is particularly effective for a closed fuel cell.

Embodiments according to the present invention will be described below with reference to the drawings.
[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIG.
FIG. 1 schematically shows a fuel cell according to an embodiment of the present invention. As the fuel cell, a polymer electrolyte fuel cell (PEFC) is suitable, but the type is not limited. The fuel cell is a closed fuel cell suitable for use in space equipment and diving. That is, the off gas discharged from the fuel cell stack and the drain water separated from the off gas are not discharged to the outside of the fuel cell, but are stored inside the fuel cell system.

The fuel cell stack (fuel cell main body) 1 is supplied with hydrogen (fuel) from a hydrogen cylinder 2 and oxygen (oxidant) from an oxygen cylinder 4.
A hydrogen humidifier 6 is provided between the hydrogen cylinder 2 and the fuel cell stack 1. Hydrogen is humidified by the hydrogen humidifier 6 and then guided to the fuel cell stack 1. The piping between the hydrogen cylinder 2 and the hydrogen humidifier 6 is provided with an on-off valve 8, a pressure regulator 9, and a flow rate regulating valve 10 in this order from the hydrogen cylinder 2 side. The operations of the on-off valve 8, the pressure regulator 9, and the flow rate adjustment valve 10 are controlled by a control unit (not shown).
A hydrogen pressure gauge 12 is provided in a pipe between the hydrogen humidifier 6 and the fuel cell stack 1. The hydrogen pressure gauge 12 measures the hydrogen pressure in the fuel cell stack 1. The output of the hydrogen pressure gauge 12 is transmitted to a control unit (not shown).

An oxygen humidifier 16 is provided between the oxygen cylinder 4 and the fuel cell stack 1. Oxygen is humidified by the oxygen humidifier 16 and then guided to the fuel cell stack 1. The piping between the oxygen cylinder 4 and the oxygen humidifier 16 is provided with an on-off valve 18, a pressure regulator 19, and a flow rate regulating valve 20 in order from the oxygen cylinder 4 side. The operations of the on-off valve 18, the pressure regulator 19 and the flow rate adjustment valve 20 are controlled by a control unit (not shown).
An oxygen pressure gauge 22 is provided in the pipe between the oxygen humidifier 16 and the fuel cell stack 1. The oxygen pressure gauge 22 measures the oxygen pressure in the fuel cell stack 1. The output of the oxygen pressure gauge 22 is transmitted to a control unit (not shown).

  In the fuel cell stack 1, power is generated by an electrochemical reaction using the supplied hydrogen and oxygen, and the generated power is taken out by an external load (not shown).

Hydrogen exhaust gas (off-gas) containing hydrogen gas and water vapor discharged from the fuel cell stack 1 is guided to the hydrogen exhaust gas-liquid separator 25. In the gas / liquid separator 25 for hydrogen exhaust gas, moisture in the hydrogen exhaust gas is condensed and stored as drain water below.
A hydrogen exhaust valve 29 is connected to the gas / liquid separator 25 for hydrogen exhaust gas. The hydrogen exhaust valve 29 is used to remove inert gas and impurities remaining in the system through which hydrogen flows, and is closed during normal operation such as startup, steady operation, and stop operation. Therefore, depending on the system configuration, the hydrogen exhaust valve 29 can be eliminated.
A hydrogen circulation pipe 33 is connected between the gas-liquid separator 25 for hydrogen exhaust gas and the hydrogen humidifier 6. A hydrogen circulation blower 35 is provided in the middle of the hydrogen circulation pipe 33. By this hydrogen circulation blower 35, hydrogen gas is taken out from the gas phase portion in the gas / liquid separator 25 for hydrogen exhaust gas and guided to the hydrogen humidifier 6. Thereby, the hydrogen gas discharged as unreacted in the fuel cell stack 1 is circulated so as to react again, thereby forming a closed path.

Oxygen exhaust gas (off-gas) containing oxygen and water vapor discharged from the fuel cell stack 1 is guided to the oxygen exhaust gas-liquid separator 27. In this gas / liquid separator 27 for oxygen exhaust gas, the moisture in the oxygen exhaust gas is condensed and stored as drain water below.
An oxygen exhaust valve 31 is connected to the oxygen exhaust gas gas-liquid separator 27. The oxygen exhaust valve 31 is used to remove inert gas and impurities remaining in the system through which oxygen flows, and is closed during normal operation such as startup, steady operation, and stop operation. . Therefore, depending on the system configuration, the oxygen exhaust valve 31 can be eliminated.
An oxygen circulation pipe 37 is connected between the oxygen exhaust gas-liquid separator 27 and the oxygen humidifier 16. An oxygen circulation blower 39 is provided in the middle of the oxygen circulation pipe 37. Oxygen gas is taken out from the gas phase portion in the oxygen exhaust gas gas-liquid separator 27 by the oxygen circulation blower 39 and guided to the oxygen humidifier 16. Thereby, the oxygen gas discharged as unreacted in the fuel cell stack 1 is circulated so as to react again, thereby forming a closed path.

  Cooling water is supplied to the fuel cell stack 1 in order to remove reaction heat and maintain a predetermined temperature suitable for power generation. Specifically, cooling water is supplied from the circulating cooling water tank 42 to the fuel cell stack 1 by the circulating cooling water pump 44. The cooling water after cooling the fuel cell stack 1 is cooled by the cooler 46 and then returned to the circulating cooling water tank 42 again.

  Nitrogen gas is supplied from the nitrogen cylinder 48 to the upstream side of the hydrogen humidifier 6 and the oxygen humidifier 16. The nitrogen gas flowing out from the nitrogen cylinder 48 passes through the on-off valve 50 and is branched in two directions at the branching point 52 on the hydrogen humidifier 6 side and the oxygen humidifier 16 side. In each flow path branched from the branch point 52, pressure regulators 54a and 54b and flow rate regulating valves 56a and 56b are provided. The on-off valve 50, the pressure regulators 54a and 54b, and the flow rate regulating valves 56a and 56b are controlled by a control unit (not shown).

A volume in the system (hereinafter referred to as “hydrogen system volume”) that communicates with the fuel cell stack 1 and in which hydrogen can exist (hereinafter referred to as “hydrogen system volume”), and communicates with the fuel cell stack 1 and oxygen exists. The ratio of the volume of the obtained system (hereinafter referred to as “oxygen system volume”) (hereinafter referred to as “oxygen system volume”) is the equivalent ratio in the electrochemical reaction of hydrogen and oxygen. That is, since 1 mol of oxygen reacts with 2 mol of hydrogen, the ratio of the hydrogen system volume to the oxygen system volume is set to 2: 1.
The hydrogen system volume is the pipe volume from the on-off valve 8 downstream of the hydrogen cylinder 2 to the hydrogen humidifier 6, the volume of the gas phase part of the hydrogen humidifier 6, the pipe volume from the hydrogen humidifier 6 to the fuel cell stack 1, the fuel The volume of the flow path through which hydrogen in the battery stack 1 flows, the volume of the pipe from the fuel cell stack 1 to the gas / liquid separator 25 for hydrogen exhaust gas, the volume of the gas phase part of the gas / liquid separator 25 for hydrogen exhaust gas, the hydrogen exhaust gas / liquid This corresponds to the total volume of the hydrogen circulation pipe 33 from the separator 25 to the hydrogen humidifier 6. Depending on the type of valve, the pipe volume from the on-off valve 8 on the downstream side of the hydrogen cylinder 2 to the hydrogen humidifier 6 may be the volume from the pressure regulator 54a or the flow rate control valve 56a to the hydrogen humidifier 6. is there.
The oxygen system volume is the pipe volume from the on-off valve 18 downstream of the oxygen cylinder 4 to the oxygen humidifier 16, the volume of the gas phase part of the oxygen humidifier 16, the pipe volume from the oxygen humidifier 16 to the fuel cell stack 1, the fuel The volume of the flow path through which oxygen flows in the battery stack 1, the volume of the piping from the fuel cell stack 1 to the gas-liquid separator 27 for oxygen exhaust gas, the volume of the gas phase portion of the gas-liquid separator 27 for oxygen exhaust gas, the oxygen exhaust gas gas-liquid This corresponds to the total volume of the oxygen circulation pipe 37 from the separator 27 to the oxygen humidifier 16. Depending on the type of valve, the pipe volume from the on-off valve 18 downstream of the oxygen cylinder 4 to the oxygen humidifier 16 may be the volume from the pressure regulator 54b or the flow rate control valve 56b to the oxygen humidifier 16. is there.

Next, the operation of the fuel cell having the above configuration will be described.
During the power generation operation, the on-off valve 8 connected to the hydrogen cylinder 2 is opened, and the pressure regulator 9 and the flow rate adjustment valve 10 are controlled to supply hydrogen to the fuel cell stack 1 at a predetermined pressure and flow rate. Similarly, oxygen is supplied to the fuel cell stack 1 at a predetermined pressure and flow rate by opening the on-off valve 18 connected to the oxygen cylinder 4 and controlling the pressure regulator 19 and the flow rate regulating valve 20. Nitrogen is not supplied to the fuel cell stack 1 with the on-off valve 18 closed.
Hydrogen and oxygen supplied to the fuel cell stack 1 perform an electrochemical reaction through a solid polymer electrolyte membrane (not shown) and output electric power to an external load (not shown). The reaction heat generated during the reaction is removed by the cooling water supplied from the circulating cooling water tank 42 by the circulating cooling water pump 44. Thereby, the temperature in the fuel cell stack 1 is maintained at a predetermined temperature suitable for the reaction.
The hydrogen gas that has reacted in the fuel cell stack 1 is guided to the hydrogen exhaust gas-liquid separator 25 as hydrogen exhaust gas together with water vapor generated during the reaction. In the gas / liquid separator 25 for hydrogen exhaust gas, water vapor in the hydrogen exhaust gas is condensed and stored as drain water below. The hydrogen exhaust gas from which moisture has been removed by the hydrogen exhaust gas-liquid separator 25 is guided by the hydrogen circulation blower 35 to be guided to the hydrogen humidifier 6 through the hydrogen circulation pipe 33 and reused. The hydrogen exhaust valve 29 connected to the hydrogen exhaust gas-liquid separator 25 is normally closed during the power generation operation.
On the other hand, the oxygen gas that has reacted in the fuel cell stack 1 is guided to the gas / liquid separator 27 for oxygen exhaust gas as oxygen exhaust gas together with water vapor generated during the reaction. In the gas-liquid separator 27 for oxygen exhaust gas, water vapor in the oxygen exhaust gas is condensed and stored as drain water below. The oxygen exhaust gas from which moisture has been removed by the oxygen exhaust gas gas-liquid separator 27 is guided by the oxygen circulation blower 39 to be guided to the oxygen humidifier 16 through the oxygen circulation pipe 37 and reused. The oxygen exhaust valve 31 connected to the oxygen exhaust gas-liquid separator 27 is normally closed during the power generation operation.
During power generation operation, the pressure and temperature of the hydrogen system volume (see above for definition) and the oxygen system volume (see above for definition) are kept approximately equal. The pressure is maintained at a desired value by controlling the flow rate adjusting valves 10 and 20 by feeding back the output values of the hydrogen pressure gauge 12 and the oxygen pressure gauge 22. In order to maintain the system pressure, control is performed to increase the flow rate when the pressure decreases, and to decrease the flow rate when the pressure increases. About temperature, the piping which comprises hydrogen system volume, and the piping which comprises the oxygen system corresponding to the said piping are arrange | positioned in the same environment (for example, corresponding piping is installed adjacently), and desired value. Maintained.

The stop operation for stopping power generation is performed as follows.
When a stop command (not shown) is input to the control unit, the stop operation is started, and the hydrogen-side on-off valve 8 and the oxygen-side on-off valve 18, or the pressure regulators 9, 19, or the flow rate control are controlled by the command from the control unit. The valves 10 and 20 are closed, and the supply of hydrogen and oxygen is stopped. By closing both the on-off valves 8 and 18, or by closing the pressure regulators 9 and 19 or the flow control valves 10 and 20, the hydrogen system and the oxygen system are closed.
During the stop operation, hydrogen and oxygen are consumed by the self-discharge of the fuel cell stack 1 even if no external load is connected to the fuel cell stack 1. Accordingly, as hydrogen and oxygen are consumed, the pressure in the hydrogen system and oxygen system decreases. Nitrogen gas is supplied from the nitrogen cylinder 48 so as to compensate for the pressure drop. Specifically, based on the output values from the hydrogen pressure gauge 12 and the oxygen pressure gauge 22, the control unit opens the on-off valve 50 on the nitrogen gas side and maintains the pressure so as to maintain the pressure at the start of the stop operation. The regulators 54a and 54b and the flow rate adjusting valves 56a and 56b are controlled.
In this embodiment, the ratio of the hydrogen system volume to the oxygen system volume is set to the equivalent ratio in the electrochemical reaction of hydrogen and oxygen, that is, 2: 1, and the pressure and temperature at the start of the stop operation are the same for both systems. Therefore, basically, the pressure drop rates of both systems are the same. Therefore, control may be performed using either the hydrogen pressure gauge 12 or the oxygen pressure gauge 22.

Thus, nitrogen gas is supplied as hydrogen and oxygen are consumed, and eventually the hydrogen system and the oxygen system are replaced with nitrogen gas. In particular, in this embodiment, the ratio between the hydrogen system volume and the oxygen system volume is the equivalent ratio, and the pressure and temperature at the start of the stop operation are the same for both systems. The remaining amount of hydrogen and oxygen present in the system and the oxygen system is defined as the equivalent ratio. Therefore, hydrogen and oxygen can be consumed almost simultaneously without supplying hydrogen and oxygen from the hydrogen cylinder 2 and the oxygen cylinder 4 during the stop operation. Therefore, it is not necessary to purge the hydrogen system and the oxygen system with an inert gas such as nitrogen, and a stop operation suitable for the closed fuel cell as in this embodiment is realized.
Further, according to the present embodiment, after the stop operation, the hydrogen system and the oxygen system are replaced with nitrogen gas at a predetermined pressure (in this embodiment, the pressure at the start of the stop operation that is the pressure during the power generation operation). (So-called pressure holding stop), the soundness in the system can be secured.

In the present embodiment, the hydrogen system volume and the oxygen system volume are equivalent ratios, and the pressure and temperature at the start of the stop operation are made equal, but when the stop operation is started, the hydrogen and oxygen of the hydrogen system and the oxygen system are If the remaining amount is set to an equivalent ratio, a stop operation equivalent to this embodiment can be performed. For example, the hydrogen system volume and the oxygen system volume may be the same, the temperatures of both volumes at the start of the stop operation may be the same, and the hydrogen system pressure at the start of the stop operation may be twice that of the oxygen system. Alternatively, the temperature of the hydrogen system or the oxygen system may be adjusted with a heater or the like, and the remaining amount of hydrogen or oxygen may be adjusted to an equivalent ratio.
Further, in this embodiment, hydrogen and oxygen are consumed by self-discharge, but instead of this, remaining hydrogen and oxygen may be consumed by controlling an external load. In this way, hydrogen and oxygen can be consumed in a short time, and the stopping operation can be shortened.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
This embodiment is similar to the first embodiment in that nitrogen gas (inert gas) is inserted into the hydrogen system and oxygen system at a pressure equivalent to that during power generation operation after the stop operation ends (so-called pressure holding stop). Common. However, in the first embodiment, the ratio of the hydrogen system volume to the oxygen system volume is set to, for example, the equivalent ratio of 2: 1, and the hydrogen residual amount and the oxygen residual amount are set to the equivalent ratio at the start of the stop operation. In contrast, the present embodiment relates to a stopping method when the hydrogen remaining amount and the oxygen remaining amount are not set to the equivalent ratio at the start of the stopping operation.
In the present embodiment, the control unit is provided with calculation means for calculating the hydrogen residual amount of the hydrogen system and the oxygen residual amount of the oxygen system. This calculating means calculates the remaining amount of hydrogen and oxygen at predetermined time intervals from the supply flow rate of hydrogen and oxygen, the hydrogen system volume, the oxygen system volume, pressure, temperature, and the like at the start of the stop operation.
Since other configurations are the same as those of the first embodiment, description of each configuration is omitted.

The stop operation in the present embodiment is performed as follows.
When a stop command (not shown) is input to the control unit, the stop operation is started, and the control unit calculates the hydrogen remaining amount of the hydrogen system and the oxygen remaining amount of the oxygen system at present, the hydrogen system volume, oxygen system volume, pressure, temperature. From the above, it is determined which amount is smaller than the equivalent ratio. For example, when the ratio of the current hydrogen residual amount to the oxygen residual amount is 1: 1, it is determined that there is less hydrogen than the equivalent ratio, and the ratio of the current hydrogen residual amount to the oxygen residual amount is 3: In the case of 1, it is judged that there is little oxygen with respect to an equivalent ratio. Then, the opening / closing valves 8 and 18 that are determined to have a small remaining amount with respect to the equivalent ratio are not closed, and only the opening / closing valves 18 and 8 that are determined to have a large amount with respect to the equivalent ratio are closed. Do.

Pressure regulators 54a, 54b and flow rate regulating valves 56a, 56b
In the following, for ease of explanation, the case where the ratio of the remaining hydrogen amount to the remaining oxygen amount at the start of the stop operation is 1: 1, that is, the case where the remaining hydrogen amount is less than oxygen with respect to the equivalent ratio will be described. To do.
In this case, as shown in FIG. 2, since there is little hydrogen with respect to the equivalent ratio, hydrogen continues to flow with the on-off valve 8 on the hydrogen side kept open (time T0). On the other hand, since oxygen is more than hydrogen relative to the equivalent ratio, the oxygen-side on-off valve 18 is closed to stop the supply of oxygen. Then, the on-off valve 50 connected to the nitrogen cylinder 48 is opened to supply nitrogen gas to the oxygen system. The amount of nitrogen gas supplied to the oxygen system controls the pressure regulator 54b and the flow rate adjustment valve 56b so as to maintain the pressure at the start of the stop operation in accordance with the oxygen consumption. On the other hand, the pressure regulator 54a and the flow rate adjustment valve 56a on the hydrogen side are closed, and nitrogen gas is not supplied to the hydrogen system.
Hydrogen and oxygen are consumed according to the equivalence ratio by the self-discharge of the fuel cell stack 1 or the like. The control unit calculates a hydrogen amount that is insufficient with respect to the equivalent ratio derived from the oxygen remaining amount at the start of the stop operation, and keeps the hydrogen-side on-off valve 8 open until a hydrogen amount corresponding to the hydrogen amount is supplied. The pressure regulator 9 and the flow rate adjustment valve 10 are controlled. When an amount of hydrogen that is insufficient with respect to oxygen is supplied, the on-off valve 8 is closed by an instruction from the control unit (see time T1 in FIG. 2). After time T1, hydrogen is not supplied to the fuel cell stack 1. At the same time, the pressure regulator 54a and the flow rate adjustment valve 56a for supplying nitrogen gas to the hydrogen system are opened, and supply of nitrogen gas is started. The supply amount of this nitrogen gas is performed so as to maintain a predetermined pressure while feeding back the pressure from the hydrogen pressure gauge.
In the subsequent operation, as in the first embodiment, nitrogen gas is supplied as hydrogen and oxygen are consumed. Finally, the hydrogen system and the oxygen system are replaced with nitrogen gas.

  In this embodiment, it is not necessary to leave hydrogen and oxygen at an equivalent ratio during the stop operation as in the first embodiment, and it is possible to stop while adjusting the remaining amount during the stop operation. There is an advantage that a rich operation can be performed.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG.
Similar to the first embodiment, the present embodiment is common in that the remaining amounts of hydrogen and oxygen are set to have an equivalent ratio at the start of the stop operation. However, it is different in that nitrogen gas (inert gas) is put in a pressurized state before the start of power generation (so-called pressurized inert gas filling).
Since other configurations are the same as those of the first embodiment, description of each configuration is omitted.

  In the present embodiment, when the fuel cell is started, positive pressure nitrogen gas is supplied to the hydrogen system and the oxygen system, and the start is further started by supplying hydrogen and oxygen. For example, after supplying 150 kPa of nitrogen gas to the hydrogen system and the oxygen system, 400 kPa of hydrogen and oxygen are supplied. In this case, the hydrogen concentration and oxygen concentration are about 60%. In this state, power generation operation is performed.

During the stop operation, as in the first embodiment, the remaining amounts of hydrogen and oxygen are set to an equivalent ratio, so that the hydrogen and oxygen are not supplied additionally, and are left in accordance with the consumption of the remaining hydrogen and oxygen. . When almost all of the hydrogen and oxygen are consumed, the hydrogen system and oxygen system are kept pressurized with the 150 kPa nitrogen gas supplied at startup.
As described above, according to the present embodiment, by allowing nitrogen, which is an inert gas, to exist before power generation, the hydrogen system and the oxygen system can be changed to nitrogen without supplying new nitrogen after the stop operation. Furthermore, since it is in a pressurized state, a leak in the system can be easily detected, and maintenance can be easily performed.

  As described in the first embodiment, it is sufficient that the hydrogen and oxygen remaining amounts in the hydrogen system and the oxygen system are set to an equivalent ratio when the stop operation is started, and by controlling the pressure and temperature. The remaining amount of hydrogen and oxygen may be equivalent ratio.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described with reference to FIG.
Similar to the third embodiment, this embodiment is common in that nitrogen gas (inert gas) is put in a hydrogen system and an oxygen system in a pressurized state before the start of power generation (so-called pressurized inert gas filling). To do. However, in the third embodiment, the ratio of the hydrogen system volume to the oxygen system volume is set to, for example, the equivalent ratio of 2: 1, and the hydrogen residual amount and the oxygen residual amount are set to the equivalent ratio at the start of the stop operation. In contrast, the present embodiment relates to a stopping method when the hydrogen remaining amount and the oxygen remaining amount are not set to the equivalent ratio at the start of the stopping operation. In this respect, the relationship between the first embodiment and the second embodiment corresponds to the relationship between the third embodiment and the present embodiment.
In the present embodiment, as in the second embodiment, the control unit is provided with computing means for computing the hydrogen remaining amount of the hydrogen system and the oxygen remaining amount of the oxygen system. This calculating means calculates the remaining amount of hydrogen and oxygen at predetermined time intervals from the supply flow rate of hydrogen and oxygen, the hydrogen system volume, the oxygen system volume, pressure, temperature, and the like at the start of the stop operation.
Since other configurations are the same as those of the third embodiment, description of each configuration is omitted.

As in the second embodiment, the stop operation in the present embodiment obtains the remaining amounts of oxygen and hydrogen and continues to supply the smaller gas with respect to the equivalent ratio while stopping the supply of the other gas. To do. After the stop operation is completed, hydrogen and oxygen are consumed, and the hydrogen system and the oxygen system are kept pressurized with the nitrogen gas supplied at the time of startup.
In the present embodiment, it is not necessary to leave hydrogen and oxygen at an equivalent ratio during the stop operation as in the third embodiment, and it can be stopped while adjusting the remaining amount during the stop operation. There is an advantage that a rich operation can be performed.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described with reference to FIG.
FIG. 3 shows a schematic configuration of the fuel cell according to the present embodiment. FIG. 3 is the same as FIG. 1 shown in the first embodiment, except that the system to which nitrogen is supplied from the nitrogen cylinder 48 is abolished, and other configurations are the same. Therefore, the same code | symbol is attached | subjected about a common structure and the description is abbreviate | omitted.

The stop operation for stopping power generation is performed as follows.
In this embodiment, even if hydrogen and oxygen are consumed, the pressure is reduced by the reaction of hydrogen and oxygen without supplying nitrogen gas as in the above embodiments, and finally the pressure is reduced to about the saturated vapor pressure. Thus, the operation is stopped in a negative pressure state that is lower than the atmospheric pressure (so-called vapor pressure stop).
When a stop command (not shown) is input to the control unit, the stop operation is started, and the hydrogen side on-off valve 8 and the oxygen side on-off valve 18 are closed by the command from the control unit, and the supply of hydrogen and oxygen is stopped. Is done. When the on-off valves 8 and 18 are closed, the hydrogen system and the oxygen system are closed.
Hydrogen and oxygen are consumed by the self-discharge of the fuel cell stack 1, and the pressure of the hydrogen system and the oxygen system decreases.
In the present embodiment, as in the first embodiment, the ratio between the hydrogen system volume and the oxygen system volume is the equivalent ratio, and the pressure and temperature at the start of the stop operation are the same for both volumes. Therefore, basically, the pressure drop rates of both volumes are equivalent. Therefore, in the end, the hydrogen system and the oxygen system are about saturated vapor pressure. In addition, inevitable impurity gas may be contained in the system, and in that case, the system is stopped at a pressure equal to or higher than the saturated vapor pressure of hydrogen and oxygen.
Thus, according to this embodiment, unlike the first to fourth embodiments, it is not necessary to provide a nitrogen cylinder or a nitrogen gas supply line, so that a simple configuration can be realized.

  As described in the first embodiment, it is sufficient that the hydrogen and oxygen remaining amounts in the hydrogen system and the oxygen system are set to an equivalent ratio when the stop operation is started, and by controlling the pressure and temperature. The remaining amount of hydrogen and oxygen may be equivalent ratio.

[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described with reference to FIG.
Similar to the fifth embodiment, the present embodiment is common in that the system is maintained at about the saturated vapor pressure after the stop operation is completed (so-called vapor pressure stop). However, in the fifth embodiment, the ratio of the hydrogen system volume to the oxygen system volume is set to, for example, the equivalent ratio of 2: 1, and the hydrogen residual amount and the oxygen residual amount are set to the equivalent ratio at the start of the stop operation. In contrast, the present embodiment relates to a stopping method when the hydrogen remaining amount and the oxygen remaining amount are not set to the equivalent ratio at the start of the stopping operation. In this respect, the relationship between the first embodiment and the second embodiment and the relationship between the third embodiment and the fourth embodiment correspond to the relationship between the fifth embodiment and the present embodiment.
In the present embodiment, as in the second and fourth embodiments, the control unit is provided with calculation means for calculating the hydrogen remaining amount of the hydrogen system and the oxygen remaining amount of the oxygen system. This calculating means calculates the remaining amount of hydrogen and oxygen at predetermined time intervals from the supply flow rate of hydrogen and oxygen, the hydrogen system volume, the oxygen system volume, pressure, temperature, and the like at the start of the stop operation.
Since other configurations are the same as those of the fifth embodiment, description of each configuration is omitted.

As in the second embodiment, the stop operation in the present embodiment obtains the remaining amounts of oxygen and hydrogen and continues to supply the smaller gas with respect to the equivalent ratio while stopping the supply of the other gas. To do. However, in this embodiment, nitrogen gas is not supplied (this is the same as in the fifth embodiment). After the stop operation is completed, hydrogen and oxygen are consumed, and the hydrogen system and the oxygen system are brought to a state of about the saturated vapor pressure of hydrogen and oxygen.
In this embodiment, it is not necessary to leave hydrogen and oxygen at an equivalent ratio during the stop operation as in the fifth embodiment, and it can be stopped while adjusting the remaining amount during the stop operation. There is an advantage that a rich operation can be performed.

It is the schematic block diagram which showed one Embodiment of the fuel cell of this invention. It is a timing chart which showed the supply timing of hydrogen, oxygen, and nitrogen. It is the schematic block diagram which showed other embodiment of the fuel cell of this invention.

Explanation of symbols

1 Fuel cell stack (fuel cell body)
2 Hydrogen cylinder 4 Oxygen cylinder 6 Hydrogen humidifier 25 Gas / liquid separator for hydrogen exhaust gas 27 Gas / liquid separator for oxygen exhaust gas 33 Hydrogen circulation pipe 35 Hydrogen circulation blower 37 Oxygen circulation pipe 39 Oxygen circulation blower 48 Nitrogen cylinder

Claims (12)

Comprising a fuel cell body that generates electricity with fuel and oxidant;
A fuel cell comprising a stop operation for stopping the fuel cell body without stopping the fuel and the oxidant when the power generation of the fuel cell body is stopped,
The remaining amount of fuel at the start of the stop operation in the fuel space that communicates with the fuel cell body and in which the fuel can exist, and the oxidant space that communicates with the fuel cell body and in which the oxidant can exist The volume, pressure, and temperature of the fuel space and / or the oxidant space are set so that the ratio of the remaining amount of oxidant at the start of the stop operation is the equivalent ratio in the reaction between the fuel and the oxidant. At least one is set, The fuel cell characterized by the above-mentioned.   The inert gas is supplied to the fuel space and the oxidant space so that the pressures of the fuel space and the oxidant space are maintained at predetermined values during the stop operation. Fuel cell.   2. The fuel cell according to claim 1, wherein at the start of the stop operation, the fuel space and the oxidant space are closed, and gas supply to these spaces is stopped.   2. The fuel cell according to claim 1, wherein an inert gas having a predetermined pressure is supplied in advance into the fuel space and the oxidant space at the start of the stop operation.   The fuel cell according to claim 4, wherein the inert gas is supplied at the predetermined pressure at the time of start-up when starting a power generation operation. Comprising a fuel cell body that generates electricity with fuel and oxidant;
A fuel cell comprising a stop operation for stopping the fuel cell body without stopping the fuel and the oxidant when the power generation of the fuel cell body is stopped,
During the stop operation, the remaining amount of fuel in the fuel space that communicates with the fuel cell body and in which the fuel can exist, and the oxidant in the oxidant space that communicates with the fuel cell body and in which the oxidant can exist The fuel cell, wherein the fuel and / or the oxidant is supplied to the fuel space and / or the oxidant space so that the ratio to the remaining amount is an equivalent ratio.   The fuel cell according to claim 6, wherein an inert gas is supplied to the fuel space and the oxidant space so as to maintain a pressure in the fuel space and the oxidant space at a predetermined value.   7. The fuel or the oxidant space is a closed space at the start of the stop operation, and only the smaller one of the fuel or the oxidant is supplied in light of the equivalence ratio. Fuel cell.   7. The fuel cell according to claim 6, wherein an inert gas having a predetermined pressure is supplied in advance into the fuel space and the oxidant space at the start of the stop operation.   The fuel cell according to claim 9, wherein the inert gas is supplied at the predetermined pressure at the time of start-up when starting a power generation operation. Comprising a fuel cell body that generates electricity with fuel and oxidant;
A method of operating a fuel cell comprising a stop operation for stopping the fuel cell main body without stopping the fuel and the oxidant when the power generation is stopped.
The remaining amount of fuel at the start of the stop operation in the fuel space that communicates with the fuel cell body and in which the fuel can exist, and the oxidant space that communicates with the fuel cell body and in which the oxidant can exist The volume, pressure, and temperature of the fuel space and / or the oxidant space are set so that the ratio of the remaining amount of oxidant at the start of the stop operation is the equivalent ratio in the reaction between the fuel and the oxidant. A method of operating a fuel cell, wherein at least one is set and the stop operation is performed. Comprising a fuel cell body that generates electricity with fuel and oxidant;
A method of operating a fuel cell comprising a stop operation for stopping the fuel cell main body without stopping the fuel and the oxidant when the power generation is stopped.
During the stop operation, the remaining amount of fuel in the fuel space that communicates with the fuel cell body and in which the fuel can exist, and the oxidant in the oxidant space that communicates with the fuel cell body and in which the oxidant can exist A method for operating a fuel cell, comprising supplying the fuel and / or the oxidant to the fuel space and / or the oxidant space so that a ratio to a remaining amount is an equivalent ratio.

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