JP2003157873A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent excess supply of moisture to a fuel cell and production of flooding in the fuel cell. SOLUTION: This fuel cell system comprises a fuel cell 1 for generating electricity by hydrogen gas and air supplied; a hydrogen gas supply passage 10 for supplying the hydrogen gas to the fuel cell 1; a hydrogen off-gas circulation passage 20 for returning the hydrogen off-gas discharged from the fuel cell 1 to the hydrogen gas supply passage 10; an ejector 11 for pressurizing the hydrogen off-gas; an anode humidifier 12 for supplying moisture to a gas flowing in the hydrogen gas supply passage 10; and an anode dehumidifier 21 for removing moisture from the hydrogen gas flowing in the hydrogen off-gas circulation passage 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system that recycles off gas of fuel gas, that is, fuel off gas, mixes it with fuel gas, and supplies it to a fuel cell.

[0002]

2. Description of the Related Art A fuel cell mounted on a fuel cell vehicle or the like is provided with an anode and a cathode on both sides of a solid polymer electrolyte membrane, a fuel gas (for example, hydrogen gas) is supplied to the anode, and an oxidizer is supplied to the cathode. There is one in which a gas (for example, oxygen or air) is supplied to directly extract chemical energy involved in the redox reaction of these gases as electric energy. In this fuel cell, hydrogen gas is ionized at the anode and moves in the solid polymer electrolyte, and electrons are
It is possible to extract electrical energy from a series of electrochemical reactions that travel through an external load to the cathode and react with oxygen to produce water. As described above, since the power generation in the fuel cell is accompanied by the generation of water, the fuel gas (that is, the fuel off gas) or the oxidant gas (that is, the oxidant off gas) discharged from the cell contains water. .

By the way, in this fuel cell, when the solid polymer electrolyte membrane is dried, the ionic conductivity is lowered and the energy conversion efficiency is lowered. Therefore, in order to maintain good ionic conduction. It is necessary to supply water to the solid polymer electrolyte membrane. Therefore, in this type of fuel cell,
Generally, before supplying to the fuel cell, the fuel gas or the oxidant gas or both of them are humidified by a humidifier, and the humidified gas is supplied to the solid polymer electrolyte membrane so that the water content of the solid polymer electrolyte membrane is increased. Is supplied (JP-A-8-273687, etc.).

In addition, in this type of fuel cell, generally, the fuel gas discharged from the fuel cell after being used for power generation, that is, the fuel off-gas contains unreacted fuel gas, and therefore, in order to improve fuel efficiency. The fuel off gas is recycled by using a pressurizing device such as an ejector or a pump, mixed with fresh fuel gas, and supplied again to the fuel cell.

FIG. 7 shows the structure of a conventional general fuel cell system. Air as the oxidant gas is pressurized to a predetermined pressure by the compressor 51, humidified by the cathode humidifier 52, and supplied to the cathode of the fuel cell 50. After this air is used for power generation, it is discharged from the fuel cell 50 as air off gas and discharged via the pressure control valve 53. On the other hand, hydrogen gas as a fuel gas supplied from a fuel supply device (not shown) passes through the ejector 54, is humidified by the anode humidifier 55, and is supplied to the anode of the fuel cell 50. After the hydrogen gas is used for power generation,
It is discharged as hydrogen off-gas from the fuel cell 50 and sent to the gas-liquid separator 57 through the hydrogen off-gas circulation flow path 56.
The fuel off gas from which liquid water has been removed by the gas-liquid separator 57 is sucked into the ejector 54, mixed with fresh hydrogen gas supplied from the fuel supply device, and supplied again to the anode of the fuel cell 50.

[0006]

As described above, when recycling the hydrogen off-gas, liquid water is removed from the hydrogen off-gas by the gas-liquid separator 57, but since the hydrogen off-gas has high humidity, the liquid When the hydrogen off-gas after water removal is pressurized by the ejector 54, the vapor in the hydrogen off-gas is condensed to generate condensed water, and the condensed water is supplied to the fuel cell 50 together with the fuel gas and the fuel off-gas. It may be supplied, which may cause flooding in the fuel cell 50. Fuel cell 5
If flooding occurs within 0, the flow of fuel gas is obstructed, the flow of fuel gas becomes non-uniform, or the flow of fuel gas is partially stopped, and the power generation state becomes unstable. Occurs. Therefore, the present invention provides a fuel cell system capable of stabilizing the power generation state of the fuel cell by preventing the excessive supply of water to the fuel cell and performing the proper water supply.

[0007]

In order to solve the above problems, the invention described in claim 1 provides a fuel gas (for example, hydrogen gas in the first to fifth embodiments described later) and an oxidant gas. (For example, air in first to fifth embodiments described below) to generate electric power by being supplied with the fuel cell (for example, fuel cell 1 in first to fifth embodiments described below), and the fuel. A fuel gas supply channel (for example, a hydrogen gas supply channel 10 in the first to fifth embodiments described later) for supplying the fuel gas to the cell, and a fuel off gas discharged from the fuel cell (for example, the later described). First to fifth
The fuel off-gas circulation flow path (for example, hydrogen off-gas circulation flow path 20 in the first to fifth embodiments described later) that returns the hydrogen off-gas in the embodiment to the fuel gas supply flow path, and the fuel off-gas. A pressurizing device that pressurizes (for example, the ejector 11 in the first to fifth embodiments described below) and a humidifying device that applies moisture to the gas flowing through the fuel gas supply passage (for example, the first to fifth embodiments described below). Of the anode humidifier 12) of the present embodiment and the humidifier, which are provided separately, and dehumidify water from the fuel off-gas flowing through the fuel off-gas circulation channel (for example, the first to fifth embodiments described later). Anode dehumidifier in the form of 21)
And a fuel cell system. With this configuration, the moisture (vapor) existing in the gas phase in the fuel offgas can be removed by the dehumidifier before the fuel offgas is pressurized by the pressurizer, and then the fuel offgas is added. No condensed water is generated even if pressed. In addition, since the dehumidifying device is provided separately from the humidifying device, it is possible to control the humidification degree for the fuel gas and the dehumidification degree for the fuel off-gas as desired.

The invention described in claim 2 is the same as the invention described in claim 1, wherein the dehumidifying device (for example, the anode dehumidifier 2 in the second and third embodiments described later) is used.
1) is a membrane dehumidifier that exchanges moisture between fluids that are in contact with both sides of the permeable membrane via a permeable membrane, and the fluid that removes moisture from the fuel off-gas in the dehumidifier is downstream of the pressurizer. It is characterized in that it is a fuel gas flowing through. With such a configuration, it is possible to humidify the fuel gas by giving the moisture taken from the fuel off gas to the fuel gas.

According to a third aspect of the present invention, in the invention according to the second aspect, the humidifier (for example, an anode humidifier 12 in a second embodiment described later) is the dehumidifier (for example, later described). It is arranged downstream of the anode dehumidifier 21) in the second embodiment. With this configuration, it is possible to increase the humidity difference between the two gases flowing with the permeable membrane in between as compared with the case where the humidifying device is arranged upstream of the dehumidifying device, and as a result, to the fuel off gas in the dehumidifying device. It is possible to increase the dehumidification performance, in other words, it is possible to increase the humidification performance for the fuel gas in the dehumidification device.

According to a fourth aspect of the present invention, in the invention according to the second aspect, the humidifier (for example, the anode humidifier 12 in the third embodiment described later) is the dehumidifier (for example, the later described). It is provided in a fuel gas bypass flow path (for example, a hydrogen gas bypass flow path 13 in a third embodiment described later) that bypasses the anode dehumidifier 21) in the third embodiment, and the moisture is removed from the fuel off gas. It is characterized in that it is provided with a flow rate control means (for example, a three-way valve 14 in a third embodiment which will be described later) that makes it possible to control the supply amount of the depriving fluid to the dehumidifying device. With this configuration, by controlling the supply amount, it is possible to adjust the degree of dehumidification for the fuel off gas, and it is possible to adjust the water content of the fuel gas supplied to the fuel cell. Become.

According to a fifth aspect of the present invention, in the first aspect, the dehumidifying device (for example, an anode dehumidifier 21 in a fourth embodiment described later) is provided with a permeable membrane through the permeable membrane. Is a membrane dehumidifying device that exchanges moisture between fluids contacting both surfaces of the fuel degassing device, and a fluid that removes moisture from the fuel off-gas in the dehumidifying device is a fuel gas before joining with the fuel off-gas (for example, a fourth described below). Hydrogen gas in the embodiment), and the fuel gas is sent downstream of the pressurizing means after passing through the dehumidifying device. With this configuration, it is possible to give a portion of the fuel gas moisture taken from the fuel off-gas, and join this fuel gas and the fuel gas not supplied to the dehumidifier at the downstream of the pressurizing device, It becomes possible to supply to the fuel cell.

According to a sixth aspect of the invention, in the invention according to the first aspect, the dehumidifying device (for example, an anode dehumidifier 21 in a fifth embodiment described later) is provided with a permeable membrane through the permeable membrane. Is a membrane dehumidifier that transfers and receives moisture between fluids that contact both sides of the fuel cell. The fluid that removes moisture from the fuel off gas in the dehumidifier is an oxidant gas supplied to the fuel cell (for example, an embodiment described later. Air). With this configuration, it is possible to humidify the oxidant gas by supplying the moisture taken from the fuel off gas to the oxidant gas.

According to a seventh aspect of the invention, in the invention according to the fifth or sixth aspect, a flow rate control means capable of controlling the supply amount of the fluid depriving the fuel off gas of moisture to the dehumidifying device ( For example, it is characterized by including flow rate control valves 8 and 16) in the fourth and fifth embodiments described later. With this configuration, by controlling the supply amount, it is possible to adjust the degree of dehumidification for the fuel off gas, and it is possible to adjust the water content of the fuel gas supplied to the fuel cell. Become.

The invention according to claim 8 is the invention according to claim 4 or claim 7, wherein a dew point meter for detecting the dew point of the fuel off-gas from which water has been removed by the dehumidifying device (for example, a third de- scribed later). ~ Dew point meter 22 in the fifth embodiment, based on the detection value of the dew point meter, the flow rate control means (for example, the three-way valve 14, the flow rate control valve in the third to fifth embodiments described later). 8, 16) are controlled. With this configuration, it is possible to properly adjust the degree of dehumidification for the fuel off gas.

According to a ninth aspect of the invention, in the invention according to the fourth or seventh aspect, a cell voltage detecting device for detecting a cell voltage of the fuel cell (for example, third to fifth embodiments described later) is provided. Cell voltage detecting device 5) in the above embodiment, and based on the detection value of the cell voltage detecting device, the flow rate control means (for example, the three-way valve 14 and the flow control valve 8 in the third to fifth embodiments described later). , 16) are controlled. By configuring in this way,
It is possible to properly adjust the degree of dehumidification for the fuel off gas.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a fuel cell system according to the present invention will be described below with reference to the drawings of FIGS. 1 to 5. [First Embodiment] First, a first embodiment of the fuel cell system according to the present invention will be described with reference to the drawing of FIG. FIG. 1 is a schematic configuration diagram of a fuel cell system according to the first embodiment. The fuel cell 1 comprises a stack composed of a plurality of cells formed by sandwiching a solid polymer electrolyte membrane, such as a solid polymer ion exchange membrane, between an anode and a cathode from both sides. When hydrogen gas is supplied and air containing oxygen as an oxidant gas is supplied to the cathode, hydrogen ions generated by the catalytic reaction at the anode move to the cathode through the solid polymer electrolyte membrane and become oxygen at the cathode. Electrochemical reaction causes electricity to generate water.

Air is pressurized to a predetermined pressure by the compressor 2, humidified by the cathode humidifier 3 and supplied to the cathode of the fuel cell 1. After being used for power generation, this air is discharged from the fuel cell 1 as air off gas, passes through the cathode humidifier 3, and is discharged via the pressure control valve 4. The cathode humidifier 3 is a membrane humidifier that exchanges moisture between fluids in contact with both surfaces of the permeable membrane via the permeable membrane,
In the cathode humidifier 3, the moisture of the air off gas is transferred to the air supplied to the fuel cell 1 to humidify the air.

On the other hand, hydrogen gas supplied from a fuel supply device (not shown) passes through an ejector 11 and an anode humidifier (humidification device) 12 provided in the hydrogen gas supply passage (fuel gas supply passage) 10. Is supplied to the anode of the fuel cell 1. At this time, the fuel gas is humidified by the anode humidifier 12. The anode humidifier 12 may be any type of humidifier as long as it can humidify the fuel gas. After the hydrogen gas supplied to the fuel cell 1 is used for power generation, it is discharged from the fuel cell 1 as hydrogen off-gas, passed through the hydrogen off-gas circulation flow path (fuel off-gas circulation flow path) 20, and sucked by the ejector 11. Mixed with fresh hydrogen gas supplied from the fuel supply system,
It is humidified by the anode humidifier 12 and supplied again to the anode of the fuel cell 1.

The ejector 11 sucks the hydrogen off-gas in the hydrogen off-gas circulation flow path 20 with a negative pressure generated by the jet flow of the fuel gas supplied from the hydrogen gas supply path 10 to the ejector 11, mixes the two, and sends them out. The hydrogen off gas is pressurized when passing through the ejector 11. Therefore, the ejector 11 can be regarded as a pressurizing device for pressurizing the hydrogen off gas. An anode dehumidifier (dehumidifier) 21 is provided in the middle of the hydrogen off-gas circulation flow path 20. The anode dehumidifier 21 removes vapor phase water contained in the hydrogen off gas, that is, vapor, and may be any type of dehumidifier as long as it has this function.

In the fuel cell system configured as described above, before the high-humidity hydrogen off-gas discharged from the fuel cell 1 is pressurized by the ejector 11, the moisture in the hydrogen off-gas is removed by the anode dehumidifier 21. Because it is done
After that, even if the hydrogen off-gas is pressurized and compressed in the ejector 11, condensed water does not occur. Then, the fresh hydrogen gas and hydrogen off-gas (hereinafter referred to as mixed hydrogen gas) mixed in the ejector 11 are humidified to an appropriate water content by the anode humidifier 12 provided downstream thereof, and the hydrogen gas of the fuel cell 1 is discharged. It will be supplied to the anode. Since the anode dehumidifier 21 is provided separately from the anode humidifier 12, it is possible to control the humidification degree for hydrogen gas and the dehumidification degree for hydrogen off-gas as desired. Therefore, excessive supply of water to the fuel cell 1 can be prevented, flooding in the fuel cell 1 can be prevented, and the solid polymer electrolyte membrane of the fuel cell 1 can be kept in an appropriate water state. ,
As a result, the power generation state of the fuel cell 1 can be stabilized.

[Second Embodiment] Next, a second embodiment of the fuel cell system according to the present invention will be described with reference to the system configuration diagram of FIG. The fuel cell system according to the second embodiment differs from that according to the first embodiment in the following points. The anode dehumidifier 21 in the second embodiment is composed of a membrane dehumidifier that exchanges moisture between fluids in contact with both surfaces of the permeable membrane via the permeable membrane. The permeable membrane is a porous membrane that allows not only water vapor to pass but also a small amount of gas, and a non-porous membrane that blocks gas permeation and allows only water vapor to pass (ion hydration type or dissolution diffusion type). Etc.), but in the case of the anode dehumidifier 21 of the second embodiment, any type of permeable membrane may be used.

The anode dehumidifier 21 includes an ejector 11
It is arranged so as to straddle the hydrogen gas supply flow passage 10 and the hydrogen off-gas circulation flow passage 20 which are located between the anode humidifier 12 and the anode humidifier 12, and inside the anode dehumidifier 21 with the permeable membrane as a boundary. The hydrogen gas after mixing flows, and the hydrogen off gas flows to the other side. Here, since the hydrogen off-gas has an extremely high humidity as compared with the hydrogen gas after mixing, inside the anode dehumidifier 21, the water in the hydrogen off-gas permeates the permeable membrane and moves to the hydrogen gas after mixing. . That is, in the anode dehumidifier 21 according to the second embodiment, the fluid that removes water from the hydrogen off-gas is the mixed hydrogen gas, and the water taken from the hydrogen off-gas is given to the mixed hydrogen gas and then mixed. The hydrogen gas is humidified.

The mixed hydrogen gas humidified by the anode dehumidifier 21 is further humidified by the anode humidifier 12. Therefore, in the fuel cell system according to the second embodiment, in addition to the function of the fuel cell system according to the first embodiment described above, the load of the anode humidifier 12 can be reduced, and The size can be reduced. Further, in the third embodiment, since the anode humidifier 12 is arranged downstream of the anode dehumidifier 21, compared with the case where the anode humidifier 12 is arranged upstream of the anode dehumidifier 21, The humidity difference between the two gases sandwiching the membrane can be increased, and as a result, the dehumidification performance for the fuel off gas in the anode dehumidifier 21 can be increased. In other words, the humidification performance for the fuel gas in the anode dehumidifier 21 can be increased. Can be increased. Since the other configurations are the same as those of the first embodiment, the same reference numerals are given to the same aspect parts and the description thereof will be omitted.

[Third Embodiment] Next, a third embodiment of the fuel cell system according to the present invention will be described with reference to the system configuration diagram of FIG. The fuel cell system according to the third embodiment is different from that according to the second embodiment in the following points. In the fuel cell system according to the third embodiment, a first hydrogen gas bypass passage (fuel gas bypass passage) 13 that bypasses the anode dehumidifier 21 is connected to the hydrogen gas supply passage 10. The anode humidifier 12 is arranged in the first hydrogen gas bypass passage 13. In addition, the hydrogen gas supply flow path 10 located between the ejector 11 and the anode dehumidifier 21.
And a three-way valve 14 for switching the flow path is provided at the connection portion between the first hydrogen gas bypass flow path 13 and the first hydrogen gas bypass flow path 13.
By switching No. 4, it is possible to select which of the anode dehumidifier 21 and the anode humidifier 12 the hydrogen gas after mixing is made to flow.

Further, in the hydrogen off-gas circulation flow path 20 downstream of the anode dehumidifier 21, the anode dehumidifier 21 is provided.
Dew point meter to detect the dew point of hydrogen off gas sent from
2 is provided, and the three-way valve 14 is switched and controlled based on the detection value of the dew point meter 22.
Since other configurations are the same as those of the second embodiment, the same reference numerals are given to the same aspect parts and the description thereof will be omitted.

The fuel cell system according to the third embodiment having the above-described structure has the following operation in addition to the operation of the fuel cell system according to the first embodiment. That is, when the detection value of the dew point meter 22 is higher than a preset upper limit value, the amount of water supplied to the fuel cell 1 is large, and it is predicted that flooding may occur in the fuel cell 1. Therefore, in this case, the three-way valve 14 is switched so that the mixed hydrogen gas flows only to the anode dehumidifier 21 and does not flow to the anode humidifier 12. As a result, the hydrogen gas after mixing is
Since it is only humidified by the anode dehumidifier 21 and is not humidified by the anode humidifier 12, it is possible to reduce the amount of humidification to the hydrogen gas after mixing, and to prevent excessive supply of water to the fuel cell 1 in advance. Can be prevented. At this time, the hydrogen off gas is dehumidified by the anode dehumidifier 21.

On the other hand, when the detected value of the dew point meter 22 is lower than the preset lower limit value, the amount of water supplied to the fuel cell 1 is small and the amount of water in the fuel cell 1 may be insufficient. As predicted, in this case, the three-way valve 14 is switched so that the hydrogen gas after mixing flows only to the anode humidifier 12 and does not flow to the anode dehumidifier 21. As a result, the hydrogen gas after mixing does not flow into the anode dehumidifier 21, so the anode dehumidifier 21 does not function as a dehumidifier, and the hydrogen off-gas passes through the anode dehumidifier 21 without being dehumidified. Therefore, the hydrogen off-gas is returned to the hydrogen gas supply passage 10 through the ejector 11 while keeping the high humidity. Then, the mixed hydrogen gas delivered from the ejector 11 is humidified by the anode humidifier 12 to an appropriate amount of water, and the fuel cell 1
Will be supplied to the anode. As a result, the water shortage of the fuel cell 1 can be prevented in advance, and the solid polymer electrolyte membrane of the fuel cell 1 can be kept in an appropriate water state,
The power generation state of the fuel cell 1 can be stabilized. This is advantageous when it is desired to quickly supply a large amount of water to the fuel cell 1, such as when the fuel cell 1 is started or when the load is suddenly increased.

In the third embodiment, the three-way valve 1
Reference numeral 4 represents the supply amount of hydrogen gas (that is, a fluid that removes water from hydrogen off gas) after mixing to the anode dehumidifier 21.
It can be said to be a flow rate control means for controlling to either 100% or 100%. It should be noted that the three-way valve 14 is supplied to the anode humidifier 12, and the mixed hydrogen gas and the anode dehumidifier 21 are mixed.
It is also possible to use a flow rate control valve capable of arbitrarily setting the flow rate ratio of the hydrogen gas after mixing and flowing into the chamber. By doing so, it is possible to finely adjust the degree of dehumidification for the hydrogen off-gas, and it is possible to more appropriately control the amount of water with respect to the mixed hydrogen gas supplied to the fuel cell 1.

Further, in the embodiment, the dew point of the hydrogen off-gas downstream of the anode dehumidifier 21, that is, the detection value of the dew-point meter 22 provided in the hydrogen off-gas circulation flow path 20, is measured in the fuel cell 1. The three-way valve 14 is controlled based on the detection value of the dew point meter 22 by predicting the excess or deficiency of the amount of water. Since it is also possible to predict from the cell voltage, instead of the dew point meter 22, the fuel cell 1 is provided with a cell voltage detecting device 5 for detecting each cell voltage, and based on the detected value of the cell voltage detecting device 5, The valve 14 may be controlled.

[Fourth Embodiment] Next, a fourth embodiment of the fuel cell system according to the present invention will be described with reference to the system configuration diagram of FIG. The fuel cell system according to the fourth embodiment is different from that according to the second embodiment in the following points. In the fuel cell system according to the fourth embodiment, the second hydrogen gas bypass passage 15 that bypasses the ejector 11 is connected to the hydrogen gas supply passage 10, and the anode dehumidifier 21 has the second passage.
Hydrogen gas bypass channel 15 and hydrogen off-gas circulation channel 20
It is located across and. Also in the anode dehumidifier 21, the hydrogen gas becomes a fluid that removes water from the hydrogen off gas.

The anode dehumidifier 2 is provided upstream of the anode dehumidifier 21 in the second hydrogen gas bypass passage 15.
A flow rate control valve (flow rate control means) 16 is provided to control the flow rate of the hydrogen gas (that is, a fluid that removes water from hydrogen off gas) flowing in the first flow path 1. By controlling the flow rate control valve 16 to control the flow rate of the hydrogen gas flowing to the anode dehumidifier 21, the degree of dehumidification of the hydrogen off gas by the anode dehumidifier 21 can be adjusted.

Further, in the hydrogen off-gas circulation flow path 20 downstream of the anode dehumidifier 21, the dew point of the hydrogen off-gas sent from the anode dehumidifier 21 is detected, as in the case of the third embodiment described above. A dew point meter 22 is provided. The flow rate control valve 16 is controlled based on the detection value of the dew point meter 22. Since other configurations are the same as those of the second embodiment, the same reference numerals are given to the same aspect parts and the description thereof will be omitted.

In the fuel cell system according to the fourth embodiment configured as described above, when the flow control valve 16 is open, a part of the hydrogen gas flows to the ejector 11, and the rest flows to the anode dehumidifier 21. . Anode dehumidifier 21
In the case, since the low-humidity hydrogen gas and the high-humidity hydrogen off-gas flow with the permeable membrane sandwiched between them, the moisture in the hydrogen off-gas is deprived of by the hydrogen gas, and as a result, the hydrogen off-gas is dehumidified and the second hydrogen gas bypass. The hydrogen gas flowing through the flow path 15 is humidified. Therefore, even if the hydrogen off gas is pressurized and compressed in the ejector 11 after this, condensed water does not occur. Further, the hydrogen gas humidified by the anode dehumidifier 21 is sent through the second hydrogen gas bypass passage 15 to the hydrogen gas supply passage 10 located between the ejector 11 and the anode humidifier 12. Then, the hydrogen gas that has passed through the ejector 11 and the anode dehumidifier 21
Hydrogen off gas humidified by the anode dehumidifier 2
The hydrogen gas humidified by 1 is used as the anode humidifier 12
The mixed hydrogen gas is further humidified when passing through the anode dehumidifier 21, and is supplied to the anode of the fuel cell 1.

FIG. 5 is a result of an experiment showing changes in relative humidity of gas flowing through the hydrogen gas supply passage 10 and the hydrogen off-gas circulation passage 20 in the fuel cell system according to the fourth embodiment. Points A to G are as follows. A: Hydrogen off gas outlet of the fuel cell 1 B: Hydrogen off gas inlet of the anode dehumidifier 21 C: Hydrogen off gas outlet of the anode dehumidifier 21 D: Exit of the ejector 11 E: Hydrogen gas supply passage 10 and hydrogen off gas circulation passage 20
Confluence point F: inlet of the anode humidifier 12 G: outlet of the anode humidifier 12

The degree of dehumidification of the hydrogen degas in the anode dehumidifier 21, in other words, the anode dehumidifier 2
The degree of humidification of the hydrogen gas in 1 can be adjusted by controlling the flow rate of the hydrogen gas by the flow control valve 16. In addition, as described in the third embodiment, it is possible to predict the excess or deficiency of the amount of water in the fuel cell 1 from the dew point of the hydrogen off gas downstream of the anode dehumidifier 21, so that the hydrogen off gas circulation flow path 20 Dew point meter 2 installed in
By controlling the flow rate control valve 16 based on the detected value of 2 and controlling the flow rate of the hydrogen gas supplied to the anode dehumidifier 21, the water content of the mixed hydrogen gas supplied to the fuel cell 1 is made appropriate. Can be controlled.

When the flow control valve 16 is fully closed, hydrogen gas does not flow to the anode dehumidifier 21, so the anode dehumidifier 21 does not function as a dehumidifier and the hydrogen off gas is not dehumidified. It passes through the anode dehumidifier 21. Therefore, the hydrogen off-gas is returned to the hydrogen gas supply passage 10 through the ejector 11 while keeping the high humidity. Then, the mixed hydrogen gas delivered from the ejector 11 is further humidified by the anode humidifier 12 and supplied to the anode of the fuel cell 1. This is advantageous when it is desired to quickly supply a large amount of water to the fuel cell 1, such as when the fuel cell 1 is started or when the load is suddenly increased.

As described above, according to the fuel cell system of the fourth embodiment, water can be supplied to the fuel cell 1 without excess or deficiency, so that the occurrence of flooding in the fuel cell 1 can be prevented. Therefore, the solid polymer electrolyte membrane of the fuel cell 1 can be maintained in an appropriate moisture state, and the power generation state of the fuel cell 1 can be stabilized.
In addition, the load on the anode humidifier 12 can be reduced,
The size of the anode humidifier 12 can be reduced.

Incidentally, also in the fourth embodiment,
As in the case of the third embodiment, the flow control valve 16 can be controlled based on the detection value of the cell voltage detection device 5 that detects each cell voltage of the fuel cell 1, instead of the dew point meter 22. Is. In the case of the fourth embodiment, the second hydrogen gas bypass passage 15 downstream of the anode dehumidifier 21 is used.
Can be connected to the hydrogen gas supply passage 10 downstream of the anode humidifier 12, the same effect as described above can be obtained.

[Fifth Embodiment] Next, a fifth embodiment of the fuel cell system according to the present invention will be described with reference to the system configuration diagram of FIG. The fuel cell system according to the fifth embodiment is different from that according to the first embodiment in the following points. The anode dehumidifier 21 in the fifth embodiment is provided with a non-porous permeable membrane (such as an ion hydration type permeable membrane or a dissolution diffusion type permeable membrane) that blocks gas permeation and permits only water vapor permeation. It is composed of a membrane dehumidifier that exchanges moisture between fluids in contact with both surfaces of the permeable membrane.

Further, the compressor 2 and the cathode humidifier 3
The air supply flow path 6 connecting with the air bypass flow path 7 is provided, and the anode dehumidifier 21 is disposed across the air bypass flow path 7 and the hydrogen off-gas circulation flow path 20, and the anode dehumidifier is dehumidified. In the vessel 21, the air flows to one side and the hydrogen off gas flows to the other side with the permeable membrane as a boundary. Here, since the hydrogen off-gas discharged from the fuel cell 1 has extremely high humidity as compared with the air flowing through the air bypass flow path 7, inside the anode dehumidifier 21, the water in the hydrogen off-gas permeates through the permeable membrane. And move to the air. That is, in the anode dehumidifier 21 of the fifth embodiment, the fluid that removes water from the hydrogen off gas is air as the oxidant gas, and the water taken from the hydrogen off gas is given to the air to humidify the air. .

Further, in the air bypass passage 7, upstream of the anode dehumidifier 21, a flow rate control valve (flow rate control means) for controlling the flow rate of the air (that is, a fluid for removing water from hydrogen off gas) flowing through the anode dehumidifier 21. ) 8 is provided. The flow rate control valve 8 is controlled to control the anode dehumidifier 2
By controlling the flow rate of the air flowing through No. 1, the degree of dehumidification of the hydrogen off gas by the anode dehumidifier 21 can be adjusted.

Further, in the hydrogen off-gas circulation channel 20 downstream of the anode dehumidifier 21, the anode dehumidifier 21 is provided as in the case of the third and fourth embodiments described above.
Dew point meter to detect the dew point of hydrogen off gas sent from
Two are provided. The flow control valve 8 is controlled based on the detection value of the dew point meter 22. Since other configurations are the same as those of the first embodiment, the same reference numerals are given to the same aspect parts and the description thereof will be omitted.

In the fuel cell system according to the fifth embodiment having such a configuration, when the flow control valve 8 is open, a part of the air flowing through the air supply passage 6 passes through the air bypass passage 7. Flow to the anode dehumidifier 21. In the anode dehumidifier 21, low-humidity air and high-humidity hydrogen offgas flow with a permeable membrane sandwiched between them, so that water in the hydrogen offgas is deprived of the air, and as a result, the hydrogen offgas is dehumidified and the air bypass flow is passed. The air flowing through the passage 7 is humidified. Therefore, after this, the hydrogen off gas is ejected by the ejector 1.
Condensed water does not occur even if it is pressurized and compressed in 1. Further, the air humidified by the anode dehumidifier 21 is mixed with the air flowing through the air supply flow path 6 upstream of the cathode humidifier 3, and the mixed air is further humidified by the cathode humidifier 3, and the fuel cell 1 Is supplied to the cathode. Therefore, in the fuel cell system according to the fifth embodiment, the load on the cathode humidifier 3 can be reduced and the cathode humidifier 3 can be downsized.

Dehumidification degree of the hydrogen off gas in the anode dehumidifier 21, in other words, the anode dehumidifier 2
The degree of humidification with respect to air in 1 is determined by the flow control valve 8
It can be adjusted by controlling the flow rate of air.
Further, as described in the third embodiment, it is possible to predict the excess or deficiency of the amount of water in the fuel cell 1 from the dew point of the hydrogen off gas downstream of the anode dehumidifier 21.
The flow rate control valve 8 is controlled based on the detection value of the dew point meter 22 provided in the hydrogen off-gas circulation channel 20, and the anode dehumidifier 21 is controlled.
By controlling the flow rate of the air supplied to the fuel cell 1, the water content of the mixed hydrogen gas supplied to the fuel cell 1 can be appropriately controlled, and the water content of the air supplied to the fuel cell 1 can be controlled. It can be controlled properly.

When the flow control valve 8 is fully closed, no air will flow to the anode dehumidifier 21,
The anode dehumidifier 21 no longer functions as a dehumidifier, and the hydrogen off gas passes through the anode dehumidifier 21 without being dehumidified. Therefore, the hydrogen off-gas remains high in humidity while passing through the ejector 11 to supply the hydrogen gas supply flow path 10
Returned to. Then, the mixed hydrogen gas delivered from the ejector 11 is further humidified by the anode humidifier 12 and supplied to the anode of the fuel cell 1. This is advantageous when it is desired to quickly supply a large amount of water to the fuel cell 1, such as when the fuel cell 1 is started or when the load is suddenly increased.

As described above, according to the fuel cell system of the fifth embodiment, water can be supplied to the fuel cell 1 without excess or deficiency, so that the occurrence of flooding in the fuel cell 1 can be prevented. Therefore, the solid polymer electrolyte membrane of the fuel cell 1 can be maintained in an appropriate moisture state, and the power generation state of the fuel cell 1 can be stabilized.

Incidentally, also in the fifth embodiment,
Instead of the dew point meter 22, the flow rate control valve 8 is based on the detection value of the cell voltage detection device 5 that detects each cell voltage of the fuel cell 1.
It is possible to control Further, in the case of the fifth embodiment, since the air and the hydrogen off gas flow through the anode dehumidifier 21 with the permeable membrane interposed therebetween, the anode dehumidifier 21
When a porous permeable membrane is used as the permeable membrane of the fuel cell 1, oxygen in the air permeates the permeable membrane, and this oxygen reacts with hydrogen gas by the catalytic action at the anode of the fuel cell 1
This is not preferable because it may damage the solid polymer electrolyte membrane. Therefore, in the fifth embodiment, the permeable membrane of the anode dehumidifier 21 is preferably a non-porous permeable membrane that does not allow gas to permeate.

[Other Embodiments] The present invention is not limited to the above-described embodiments. For example, in each of the above-described embodiments, the ejector is used as the pressurizing device for pressurizing the fuel off gas, but instead of this, it is also possible to use a pump that sucks and sends out by a movable part such as rotation and sliding. Further, the fuel off-gas pressurized by the pump may be further pressurized by the ejector by using both of them together.

[0049]

As described above, according to the invention described in claim 1, before the fuel off-gas is pressurized by the pressurizing device, the moisture (vapor) existing in the gas phase in the fuel off-gas is dehumidifying device. After that, condensed water will not be generated even after pressurizing the fuel off gas, and as a result, excessive supply of water to the fuel cell can be prevented, and the power generation state of the fuel cell can be prevented. The excellent effect that it can be stabilized is exhibited. Further, since the dehumidifying device is provided separately from the humidifying device, the excellent effect that the humidifying condition for the fuel gas and the dehumidifying condition for the fuel off-gas can be respectively controlled as desired is exhibited.

According to the second aspect of the present invention, since it is possible to humidify the fuel gas by supplying the moisture taken from the fuel off gas to the fuel gas, it is possible to reduce the load on the humidifier and to humidify the humidifier. There is an effect that the miniaturization can be achieved. According to the invention described in claim 3, there is an effect that the dehumidifying performance for the fuel off gas in the dehumidifying device can be enhanced, in other words, the humidifying performance for the fuel gas in the dehumidifying device can be enhanced.

According to the invention described in claim 4, by controlling the supply amount, it is possible to adjust the degree of dehumidification with respect to the fuel off-gas, and at the same time, the moisture content of the fuel gas supplied to the fuel cell is adjusted. Since it can be adjusted, the amount of water in the fuel cell can be appropriately maintained, and the excellent effect that the power generation state of the fuel cell can be further stabilized is exhibited.

According to the fifth aspect of the present invention, it is possible to supply a part of the fuel gas with the moisture taken from the fuel off-gas, and the fuel gas and the fuel gas not supplied to the dehumidifying device are supplied to the pressurizing device. Since it is possible to join the fuel cells downstream and supply the fuel cells to the fuel cell, it is possible to reduce the load on the humidifying device and to reduce the size of the humidifying device.

According to the invention described in claim 6, it is possible to humidify the oxidant gas by supplying the water taken from the fuel off gas to the oxidant gas. According to the invention described in claim 7, by controlling the supply amount, it is possible to adjust the degree of dehumidification with respect to the fuel off gas, and adjust the water content of the fuel gas supplied to the fuel cell. Therefore, it is possible to maintain an appropriate amount of water in the fuel cell and to stabilize the power generation state of the fuel cell, which is an excellent effect. According to the invention described in claim 8 or claim 9, there is an effect that the degree of dehumidification for the fuel off gas can be appropriately adjusted.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a fuel cell system according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram in a second embodiment of a fuel cell system according to the present invention.

FIG. 3 is a schematic configuration diagram of a fuel cell system according to a third embodiment of the invention.

FIG. 4 is a schematic configuration diagram of a fuel cell system according to a fourth embodiment of the present invention.

FIG. 5 is a diagram for explaining changes in relative humidity of gas in the fourth embodiment.

FIG. 6 is a schematic configuration diagram of a fuel cell system according to a fifth embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a conventional general fuel cell system.

[Explanation of symbols]

1 Fuel Cell 5 Cell Voltage Detector 8 Flow Control Valve (Flow Control Means) 10 Hydrogen Gas Supply Channel (Fuel Gas Supply Channel) 11 Ejector (Pressurizer) 12 Anode Humidifier (Humidifier) 13 First Hydrogen Gas Bypass flow path (fuel gas bypass flow path) 14 Three-way valve (flow rate control means) 16 Flow rate control valve (flow rate control means) 20 Hydrogen off gas circulation flow path (fuel off gas circulation flow path) 21 Anode dehumidifier (dehumidifier) 22 Dew point Total

Claims (9)

[Claims] 1. A fuel cell for supplying electric power by supplying a fuel gas and an oxidant gas, a fuel gas supply passage for supplying the fuel gas to the fuel cell, and a fuel off gas discharged from the fuel cell. A fuel off-gas circulation channel that returns to the fuel gas supply channel, a pressurizing device that pressurizes the fuel off gas, a humidifying device that moisturizes the gas flowing through the fuel gas supply channel, and a humidifying device that is provided separately. And a dehumidifying device that removes water from the fuel off-gas flowing through the fuel off-gas circulation flow path. 2. The dehumidifying device is a membrane dehumidifying device that exchanges moisture between fluids in contact with both surfaces of the permeable membrane via a permeable membrane, and the fluid that removes moisture from the fuel off gas in the dehumidifying device is The fuel cell system according to claim 1, wherein the fuel gas is a fuel gas flowing downstream of the pressurizing device. 3. The fuel cell system according to claim 2, wherein the humidifying device is arranged downstream of the dehumidifying device. 4. The flow rate control means, wherein the humidifying device is provided in a fuel gas bypass flow path that bypasses the dehumidifying device, and makes it possible to control a supply amount of a fluid that removes water from the fuel off-gas to the dehumidifying device. The fuel cell system according to claim 2, further comprising: 5. The dehumidifying device is a membrane dehumidifying device that exchanges moisture between fluids in contact with both sides of the permeable membrane via a permeable membrane, and the fluid that removes moisture from the fuel off gas in the dehumidifying device is The fuel cell system according to claim 1, wherein the fuel gas is a fuel gas before joining with the fuel off-gas, and the fuel gas is sent to a downstream side of the pressurizing means after passing through the dehumidifying device. 6. The dehumidifying device is a membrane dehumidifying device that exchanges moisture between fluids in contact with both sides of the permeable membrane through a permeable membrane, and the fluid that removes moisture from the fuel off-gas in the dehumidifying device is The fuel cell system according to claim 1, which is an oxidant gas supplied to the fuel cell. 7. The fuel cell system according to claim 5, further comprising a flow rate control means capable of controlling a supply amount of a fluid that removes water from the fuel off-gas to the dehumidifying device. 8. A dew point meter for detecting the dew point of the fuel off-gas from which water has been removed by the dehumidifying device, and the flow rate control means is controlled based on the detection value of the dew point meter. The fuel cell system according to claim 4 or claim 7. 9. A cell voltage detecting device for detecting a cell voltage of the fuel cell is provided, and the flow rate control means is controlled based on a detection value of the cell voltage detecting device. Item 7. The fuel cell system according to Item 7.