JP2001006709A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent CO-poisoning of an anode by mixing a minute amount of oxygen into a fuel gas by a simple structure, in the case of a fuel cell system for generating power by supplying a fuel gas obtained from a fuel reforming device to the anode of a fuel cell and supplying an oxidant gas to the cathode of the fuel cell. SOLUTION: In this fuel cell system, a bubble generator 51 is installed on a bottom part of a water tank 3 for storing water 31 to be used for humidifying an electrolyte layer 23 or cooling a fuel cell 2, thereby dissolving oxygen in the water 31. A fuel gas is mixed with the water 31 and supplied to an anode 21 of the fuel cell 2, and the dissolved oxygen is discharged by the heat of the fuel cell 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of supplying a hydrocarbon-based raw fuel to a fuel reformer, reforming the fuel into a hydrogen-rich fuel gas, and supplying the reformed fuel gas to a fuel cell. The present invention relates to a fuel cell system that performs power generation.

[0002]

2. Description of the Related Art In recent years, fuel cells which have high energy conversion efficiency and do not generate harmful substances by power generation reaction have attracted attention. 2. Description of the Related Art Molecular electrolyte fuel cells are known.

FIG. 8 explains the power generation principle of the fuel cell (2), in which an electrolyte layer (23) is interposed between an anode (21) and a cathode (22), and is provided outside the anode (21). Is the hydrogen chamber (2
4), an air chamber (25) is formed outside the cathode (22). The anode (21) is supplied with hydrogen as a fuel, and the cathode (22) is supplied with air (oxygen) as an oxidant. At the anode (21), hydrogen ions and electrons are generated from the hydrogen gas, the hydrogen ions pass through the electrolyte layer (23) to the cathode (22), and the electrons flow to the external circuit (26). At the cathode (22), electrons flowing from the external circuit (26) react with oxygen in the air and hydrogen ions supplied from the electrolyte layer (23) to generate water. Thus, as a whole battery,
Water is generated from hydrogen and oxygen, and an electromotive force is generated.

In an actual fuel cell system, a hydrocarbon-based fuel such as methanol is generally used as a fuel, and a hydrogen-rich reformed gas is reformed by steam-reforming the hydrocarbon-based fuel by a fuel reformer. Then, the reformed gas is supplied to a fuel cell.

FIG. 6 shows an example of the configuration of a conventional fuel cell system, in which a fuel reformer (1) for reforming a hydrocarbon-based raw fuel into a hydrogen-rich fuel gas and a solid polymer electrolyte layer A fuel cell (2) in which an anode (21) and a cathode (22) are joined to both sides of a fuel cell (23); a raw fuel cylinder (4) for supplying raw fuel to a fuel reformer (1); (2) Anode
A water tank (3) for supplying humidifying water to (21) is provided. This humidified water is also used for cooling the fuel cell (2).

The hydrogen-rich fuel gas obtained from the fuel reformer (1) is supplied to the anode (21) of the fuel cell (2). The water (31) in the water tank (3) is fed to the anode (21) of the fuel cell (2) by the water supply pump (60). On the other hand, air is sent into the cathode (22) of the fuel cell (2) as an oxidizing gas by the blower fan (50).

[0007] The steam reforming reaction in the fuel reformer (1) is carried out while the catalyst layer of the reformer (12) is heated to a high temperature by a burner (11). (Hereinafter referred to as CO) is also generated. Particularly, in a fuel cell operating at a low temperature, the generated CO poisons the anode catalyst, causing a problem that the cell performance is reduced.

Therefore, as shown in FIG. 6, a CO converter (13) is provided at the subsequent stage of the reformer (12), and C
A process for reducing CO concentration by converting O into steam is performed.

[0009]

Embedded image CO + H ₂ O → CO ₂ + H ₂

Further, depending on the CO converter (13), the CO concentration can only be reduced to about 1%. Therefore, as shown in FIG. 6, a CO remover (14) is further provided after the CO converter (13). And a process of reducing CO concentration by oxidizing CO with air, as represented by the following formula (2).

[0011]

## STR2 ## CO + 1 / 2O ₂ → CO ₂

However, even if CO is removed efficiently, the reformed gas obtained from the fuel reformer (1) contains
It is inevitable that about 10 ppm of CO remains.
Therefore, in the fuel cell system provided with the fuel reformer (1), it is a serious problem to prevent the poisoning of the anode catalyst by a trace amount of CO.

Therefore, a method has been proposed in which oxygen is mixed in the fuel gas supplied to the fuel cell (2) to oxidize CO, thereby preventing poisoning of the anode catalyst (US Pat. No. 4). 910910). According to the method,
It is stated that by supplying oxygen having a concentration of 2 to 6% with respect to a CO concentration of 100 to 500 ppm in the fuel gas, CO poisoning of the anode catalyst can be prevented.

[0014]

However, as described above, in order to mix a very small amount of oxygen into the fuel gas, a flow meter for measuring the oxygen gas with high accuracy, a small amount of the measured oxygen gas, A device for mixing the gas with the fuel gas is required, and the configuration is complicated.
SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel cell system having a simple configuration that can mix a small amount of oxygen into fuel gas in view of the above problems.

[0015]

A fuel cell system according to the present invention comprises a fuel reformer (1) for reforming a hydrocarbon-based raw fuel into a hydrogen-rich fuel gas, and an electrolyte layer (23). Fuel cell comprising an anode (21) and a cathode (22) joined together
Wherein oxygen is dissolved in a liquid used for humidifying the electrolyte layer (23) or cooling the fuel cell (2), and the liquid is mixed with the fuel gas to form a fuel cell (2). To the anode (21).

In the fuel cell system of the present invention,
When a liquid in which oxygen is dissolved and a fuel gas are mixed and supplied to the anode (21) of the fuel cell (2), the liquid
The temperature rises due to the heat of (2), and as a result, dissolved oxygen is released as a gas. This oxygen gas is mixed with the fuel gas, and C remaining in the fuel gas
O is oxidized to prevent CO poisoning of the anode (21).

Here, the amount of oxygen to be dissolved in the liquid is very small. For example, a bubble generator (51) is provided in a tank (3) storing the liquid, and the amount of oxygen in the tank (3) is reduced. By releasing bubbles of the oxygen-containing gas into the liquid, a small amount of oxygen can be dissolved in the liquid.

If an air compressor (52) is connected to the tank (3) and the inside of the tank is pressurized to an appropriate pressure, a required amount of oxygen can be dissolved in the liquid in the tank.
Further, a sufficient amount of oxygen can be dissolved by equipping the tank (3) with a cooling device and cooling the liquid in the tank (3). Here, by controlling the temperature of the liquid in the tank, the amount of dissolved oxygen can be controlled.

As the cooling device, a heat exchanger (41) for cooling the liquid in the tank (3) by the heat of vaporization of the raw fuel supplied from the raw fuel cylinder (4) can be employed. According to the configuration, the tank (3) is used by utilizing heat of vaporization of the raw fuel or heat absorption accompanying adiabatic expansion generated when the raw fuel is supplied from the raw fuel cylinder (4) to the fuel reformer (1). Since the liquid inside is cooled, there is no need to additionally provide a special cooling device, and the system is simplified.

The oxygen-containing gas in the tank (3) is supplied to the fuel cell
If a configuration including a piping system for supplying an oxidant gas to the cathode (22) of (2) is adopted, the oxygen-containing gas contains water due to the liquid in the tank. (22) It can be humidified from the side.

A fuel cell is heated by heating a liquid in which oxygen is dissolved.
In the configuration (2) including a heating device for supplying the anode (21), the liquid in which oxygen is dissolved is heated by passing through the heating device, oxygen gas is released from the liquid, and the oxygen gas is discharged. Is supplied to the anode (21) of the fuel cell (2) together with the fuel gas obtained from the fuel reformer (1).

As the heating device, a fuel reforming device (1)
A heat exchanger (15) that heats the liquid using the reformer burner (11) as a heat source and an unreacted oxidant gas discharged from the cathode (22) of the fuel cell (2) heats the liquid. A heat exchanger (7) can be employed. According to this configuration, a new heat source is not required for heating the liquid,
The configuration is simplified.

The fuel cell system according to the present invention comprises a fuel reformer (1) for reforming a hydrocarbon-based raw fuel into a hydrogen-rich fuel gas, and anodes (21) on both surfaces of an electrolyte layer (23). )
And a pair of electrodes comprising a cathode (22) and a cooling plate (24) for cooling the electrodes.
(2), humidification of the electrolyte layer (23) or fuel cell
Oxygen is dissolved in the liquid used for cooling in (2), the liquid is mixed with the fuel gas, and supplied to the steam separator (8).
The gas obtained from the steam separator (8) is supplied to the anode (21) of the fuel cell (2), and the liquid obtained from the steam separator (8) is supplied to the cooling plate (24) of the fuel cell (2). To be supplied to

In the fuel cell system according to the present invention, the liquid in which oxygen is dissolved is mixed with the fuel gas obtained from the fuel reformer (1), so that the liquid is heated by the fuel gas to convert the liquid into oxygen. The gas is released and the oxygen gas is supplied to the steam separator (8) together with the liquid and the fuel gas. As a result, a liquid that has released oxygen and a gas that includes oxygen gas and fuel gas are obtained from the steam-water separator (8). Then, the cooling plate (24) is cooled by supplying the liquid obtained from the steam separator (8) to the cooling plate (24) of the fuel cell (2), and the battery is cooled by the cooling plate (24). The main body is cooled. Further, CO contained in the fuel gas obtained from the steam-water separator (8) is oxidized by the oxygen gas, and the C of the anode (21) is reduced.
O poisoning is prevented. After heating the liquid in which oxygen was dissolved by a heating device, mixing with the fuel gas,
It is also possible to adopt a configuration for supplying the steam-water separator (8). In this case, the liquid in which oxygen is dissolved is heated by passing through the heating device, and oxygen gas is released from the liquid, and the oxygen gas is separated from the gas-water separator together with the fuel gas obtained from the fuel reformer (1). (8).

[0025]

As described above, in the fuel cell system according to the present invention, the humidification of the electrolyte layer (23) or the fuel cell
By dissolving oxygen in the liquid used for cooling in (2), a small amount of oxygen is mixed into the fuel gas, and by heating the liquid in which oxygen is dissolved, oxygen is released from the liquid and mixed into the fuel gas. Since the configuration is adopted, CO poisoning of the anode can be prevented with a simple configuration.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Five examples of the present invention applied to a fuel cell system having a solid polymer electrolyte fuel cell will be specifically described below with reference to FIGS.

Embodiment 1 As shown in FIG. 1, the fuel cell system of this embodiment is a fuel reformer for reforming a raw fuel such as natural gas, city gas, naphtha, methanol or the like into a hydrogen-rich fuel gas. (1), a solid polymer electrolyte fuel cell (2) having an anode (21) and a cathode (22) joined to both sides of a solid polymer electrolyte layer (23), and a fuel reformer (1). It comprises a raw fuel cylinder (4) for supplying raw fuel, and a water tank (3) for supplying liquid water for humidification and cooling to the anode (21) of the fuel cell (2).

The fuel reformer (1) comprises a burner (1) for a reformer.
1), reformer (12), CO converter (13), and CO remover (14)
And a hydrogen-rich fuel gas obtained from the fuel reformer (1) is supplied to the anode (21) of the fuel cell (2).

A bubble generator (51) is installed at the bottom of the water tank (3), and a blowing fan (5) is connected to the bubble generator (51). By sending air into the vessel (51), it is possible to generate bubbles from the bubble generator (51).

The water (31) in the water tank (3) is supplied to a water supply pump (6).
To the anode (21) of the fuel cell (2).
The air (33) in the water tank (3) is used as an oxidizing gas.
The fuel is supplied to the cathode (22) of the fuel cell (2).

In the above-mentioned fuel cell system, oxygen is dissolved in the water (31) in the tank (3) by generating bubbles (32) from the bubble generator (51). Is mixed with a hydrogen-rich fuel gas obtained from the fuel reformer (1) to form an anode (21) of the fuel cell (2).
Supplied to Air containing water in the water tank (3) is supplied to the cathode (22) of the fuel cell (2).

The water supplied to the anode (21) of the fuel cell (2) receives the heat of the fuel gas and the reaction heat of the cell, and has a temperature of 8%.
The temperature rises to about 0 ° C. and releases dissolved oxygen.
In this way, a small amount of oxygen gas is generated at the anode (21) of the fuel cell (2). On the other hand, the fuel gas obtained from the fuel reformer (1) contains about 10 ppm of CO, but the CO in the fuel gas is converted into the oxygen gas by the anode (21) of the fuel cell (2). Oxidized by the anode (21)
CO poisoning is prevented.

For example, if the temperature of the water (31) in the water tank (3) is 2
At 0 ° C., when the water (31) is supplied to the anode (21) of the fuel cell (2) at a flow rate of 4.2 l / min, the water (3)
The amount of oxygen dissolved in 1) is 26.9 ml / min. When the water (31) is supplied to the anode (21) and the temperature is raised to 80 ° C., the amount of oxygen that can be dissolved in the water (31) is 8.
Since it is 4 ml / min, the difference of 18.5 ml / min of oxygen gas is released at the anode (21). The fuel cell (2) has a reaction area of 100 c.
m ² , the number of cells is 60, the current density is 300 mA / cm ² , and the composition of the fuel gas is H ₂ (80%) / CO ₂ (20
%) And contains 10 ppm of CO, the amount of oxygen gas required to oxidize the CO is about 17 ml / min. Therefore, the total CO contained in the fuel gas supplied from the fuel reformer (1) can be oxidized by the oxygen dissolved in the water supplied from the water tank (3).

In the fuel cell (2), a fuel gas is supplied to the anode (21) and air is supplied to the cathode (22), whereby a power generation reaction is performed. Here, the water supplied to the anode (21) causes the anode (21)
While humidification is performed from the side, humidification is also performed from the cathode (22) side by air containing moisture supplied to the cathode (22).

[Embodiment 2] The fuel cell system of this embodiment has basically the same configuration as that of Embodiment 1 as shown in FIG. 2, but differs in the following points. That is, a heat exchanger (15) heated by a reformer burner (11) is installed in a fuel reformer (1), and the heat exchanger (15) is connected to a feed water pump.
It is connected in the middle of a water supply pipe from the outlet of (6) to the anode (21) of the fuel cell (2). In addition, a heat exchanger (41) is installed in the water tank (3), and the heat exchanger (41) is
It is connected in the middle of the fuel pipe from (4) to the fuel reformer (1).

Thus, the anode (2) of the fuel cell (2) is
The water supplied to 1) is supplied to the heat exchanger (15) of the fuel reformer (1).
And a part or all of the dissolved oxygen is released. The released oxygen gas and water are supplied to a fuel reformer.
Fuel cell (2) mixed with fuel gas obtained from (1)
To the anode (21). At the anode (21), the remaining dissolved oxygen is released by receiving the heat of the battery. As a result, the anode (21) of the fuel cell (2) is
CO contained in the fuel gas from (1) is oxidized by the oxygen gas, thereby preventing the anode (21) from being poisoned with CO.

According to the fuel cell system of the second embodiment, the temperature of water has already risen at the inlet of the anode (21) of the fuel cell (2), and part or all of the dissolved oxygen has been released. Therefore, even near the anode inlet where the temperature is low,
Oxygen gas can be mixed with fuel gas, anode
(21) CO poisoning can be effectively prevented. or,
In the process of discharging the liquefied gas or compressed gas filled in the raw fuel cylinder (4) and supplying it to the fuel reformer (1), the water tank (3) is heated by heat of vaporization or heat absorption by adiabatic expansion. The water (31) can be cooled, so that the required amount of oxygen can be dissolved in the water (31).

Embodiment 3 As shown in FIG. 3, the fuel cell system of this embodiment has basically the same configuration as that of Embodiment 2 described above, but differs in the following points. That is, a cooling plate (24) is attached to the fuel cell (2), and it is possible to cool the cell body by flowing cooling water through a flow path formed in the cooling plate (24). is there. Further, water and oxygen gas supplied from the heat exchanger (15) of the fuel reformer (1) and fuel gas obtained from the fuel reformer (1) are mixed to form a steam-water separator (8). ), And the oxygen gas and the fuel gas obtained from the steam-water separator (8) are supplied to the anode (21) of the fuel cell (2),
Water obtained from the steam separator (8) is supplied to a cooling plate (24) of the fuel cell (2).

According to the third embodiment, the present invention can be applied to a fuel cell (2) having a cooling plate (24).
CO poisoning of the anode (21) can be prevented.

[Embodiment 4] As shown in FIG. 4, the fuel cell system of this embodiment has basically the same configuration as that of the above-described Embodiment 2, but differs in the following points. That is, a heat exchanger (7) that uses unreacted air discharged from the cathode (22) of the fuel cell (2) as a heat source is installed, and the water in which oxygen is dissolved is heated by the heat exchanger (7). It is.

According to this configuration, as in the second embodiment, oxygen gas can be mixed with the fuel gas even near the anode inlet where the temperature is low, and CO poisoning of the anode (21) can be effectively prevented. It is possible to improve the thermal efficiency by utilizing the waste heat of the fuel cell (2).

[Embodiment 5] As shown in FIG. 5, the fuel cell system of this embodiment has basically the same configuration as that of Embodiment 1, but differs in the following points. That is, the water tank
(3) has an airtight structure, and an air compressor (52) is connected to a bubble generator (53) installed at the bottom of the water tank (3). Further, a pressure regulating valve (9) is interposed in an air pipe extending from the water tank (3) to the cathode (22) of the fuel cell (2).

According to this configuration, the pressure in the water tank (3) is adjusted by the pressure adjusting valve (9), and the water in the water tank (3) is adjusted.
It is possible to control the amount of oxygen dissolved in (31), thereby supplying sufficient and necessary oxygen to the anode (21) of the fuel cell (2) to prevent CO poisoning of the anode (21). It is possible to

In the structures of the first to fifth embodiments,
Oxygen is dissolved in the water (31) in the water tank (3), but as a countermeasure in cold climates, oxygen is dissolved in an aqueous solution of methanol or ethanol having a low melting point to form an anode for the fuel cell (2).
It is also possible to adopt a configuration for supplying to (21). or,
In the configurations of Examples 1 to 5, the solid polymer electrolyte fuel cell has been described.
The present invention can be applied to any fuel cell in which poisoning of the anode catalyst by O occurs.

The effect of the fuel cell system of the present invention is confirmed.
As can be seen, the embodiment system shown in FIG.
A power generation experiment was performed by configuring a comparative example system. still,
The example system and the comparative example system have the following specifications.
A fuel cell (2) was employed. Electrode area: 100cm²  Solid polymer electrolyte layer: Perfluorocarbon sulfonic acid
Membrane Anode: Pt-Ru supported carbon Cathode: Pt supported carbon Stacking number: 30 cells

In addition, propane was used as a raw fuel. The composition of the fuel gas is as follows. _{H 2: 71.1% N 2:} 4.1% CH 4: 2.1% CO 2: 22.2% CO: 10ppm

The power generation experiment was performed under the following conditions. Current density: 0.5 A / cm²  Fuel gas utilization rate: 70% Oxidizing gas: air Oxidizing gas utilization rate: 20%

FIG. 7 shows the results of a power generation experiment.
As is clear from these results, in the example system, the average cell voltage hardly decreased even when the operation time reached 5 hours, whereas in the comparative example system, the average cell voltage increased with the elapse of the operation time. Is gradually decreasing. This is considered to be because CO poisoning of the anode was prevented in the example system, whereas CO poisoning occurred in the anode in the comparative example system.

The configuration of each part of the present invention is not limited to the above embodiment, and various modifications can be made within the technical scope described in the claims. For example, various fuel cell systems can be configured by arbitrarily combining Examples 1 to 5. In the third embodiment, the water tank
After the water from (3) is heated by the heat exchanger (15), it is mixed with the fuel gas from the fuel reformer (1), but the heat exchanger (15) is omitted and the water tank ( 3) Leave the water from
It is also possible to adopt a configuration in which the fuel gas is mixed with the fuel gas from the fuel reformer (1) and supplied to the steam separator (8).

[Brief description of the drawings]

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

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

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

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

FIG. 5 is a system diagram illustrating a configuration of a fifth embodiment of the fuel cell system according to the present invention.

FIG. 6 is a system diagram showing a configuration of a conventional fuel cell system.

FIG. 7 is a graph showing the results of a power generation experiment performed on the system of the example and the system of the comparative example.

FIG. 8 is a diagram illustrating the principle of power generation by a fuel cell.

[Explanation of symbols]

 (1) Fuel reformer (2) Fuel cell (3) Water tank (31) Water (32) Bubbles (4) Raw fuel cylinder (5) Ventilation fan (51) Bubble generator (6) Water supply pump

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Miyake 2-5-5, Keihanhondori, Moriguchi-shi, Osaka F-term (reference) in Sanyo Electric Co., Ltd. 5H027 AA06 BA01 BA16 BA17 CC06

Claims (11)

[Claims] 1. A fuel reformer (1) for reforming a hydrocarbon-based raw fuel into a hydrogen-rich fuel gas, and an anode (21) and a cathode (22) joined to both surfaces of an electrolyte layer (23). And a fuel cell (2) comprising: a fuel cell (2) for supplying fuel gas obtained from the fuel reformer (1) to an anode (21) of the fuel cell (2);
The oxidant gas is supplied to the cathode (22) of the fuel cell (2),
In a fuel cell system that generates power, the electrolyte layer (23)
Oxygen is dissolved in a liquid used for humidification or cooling of the fuel cell (2), and the liquid and the fuel gas are mixed and supplied to the anode (21) of the fuel cell (2) to dissolve in the liquid. A fuel cell system characterized by preventing CO poisoning of the anode (21) by oxygen. 2. A tank (3) comprising a tank (3) for storing said liquid, wherein a bubble generator (51) is provided in said tank (3).
2. The fuel cell system according to claim 1, wherein oxygen is dissolved in the liquid by discharging bubbles of the oxygen-containing gas into the liquid in the liquid. 3. An air compressor (52) is provided in the tank (3).
3. The fuel cell system according to claim 2, wherein the fuel cell system is connected to pressurize the inside of the tank. 4. The fuel cell system according to claim 2, wherein the tank (3) is provided with a cooling device for cooling the liquid in the tank (3). 5. The cooling device is a heat exchanger (41) for cooling the liquid in the tank (3) by heat of vaporization of the raw fuel supplied from the raw fuel cylinder (4) or heat absorption by adiabatic expansion. 5. The fuel cell system according to 4. 6. An oxygen-containing gas in a tank (3) is supplied to a fuel cell.
The fuel cell system according to any one of claims 2 to 5, further comprising a piping system for supplying an oxidant gas to the cathode (22) of (2). 7. A fuel cell by heating a liquid in which oxygen is dissolved.
The fuel cell system according to any one of claims 1 to 6, further comprising a heating device for supplying the anode (21) to (2). 8. The fuel cell system according to claim 7, wherein the heating device is a heat exchanger (15) for heating a liquid by using a reformer burner (11) constituting the fuel reformer (1) as a heat source. . 9. The heating device comprises a cathode (2) of a fuel cell (2).
The fuel cell system according to claim 7, which is a heat exchanger (7) for heating the liquid using the unreacted oxidant gas discharged from 2) as a heat source. 10. A fuel reformer (1) for reforming a hydrocarbon-based raw fuel into a hydrogen-rich fuel gas, and a pair of an anode (21) and a cathode (22) on both surfaces of an electrolyte layer (23). Electrode and cooling plate (2)
And a fuel cell (2) provided with the fuel cell (4). The fuel gas obtained from the fuel reformer (1) is supplied to the anode (21) of the fuel cell (2), and the oxidant gas is supplied to the fuel cell (2). ) Cathode (2
2), in a fuel cell system that performs power generation, oxygen is dissolved in a liquid used for humidifying the electrolyte layer (23) or cooling the fuel cell (2), and the liquid is mixed with the fuel gas. , To the steam-water separator (8)
The gas obtained from (8) is supplied to the anode (21) of the fuel cell (2), and the liquid obtained from the steam separator (8) is supplied to the cooling plate (24) of the fuel cell (2), A fuel cell system, wherein CO poisoning of the anode (21) is prevented by oxygen gas contained in the gas. 11. The fuel cell system according to claim 10, wherein the liquid in which oxygen is dissolved is heated by a heating device, mixed with the fuel gas, and supplied to the steam separator (8).