JP2000243423A - Fuel cell purging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent change in quality and deterioration of performance of a cell material even against long-term purging by enabling reaction gas of a fuel cell to be purged without using any facility exclusive for purging. SOLUTION: Cathode outlet gas is burnt in mixture with gas containing H2 in a first catalytic burner 12 to produce reducing atmosphere gas RG. The reducing atmosphere gas RG is fed to an anode 3 to purge the anode 3 in a reducing atmosphere. Anode outlet gas is burnt in mixture with gas containing O2 in a second catalytic burner 18, thereby producing oxidizing atmosphere gas OG. The oxidizing atmosphere gas OG is fed to a cathode 2 to purge the cathode 2 in an oxidizing atmosphere. A continuous gas flow can hold the reducing and oxidizing atmospheres.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purging a fuel cell used in an energy sector in which chemical energy of a fuel is directly converted into electric energy.

[0002]

2. Description of the Related Art Among the fuel cells proposed to date, a molten carbonate fuel cell is a tile (electrolyte plate) in which molten carbonate as an electrolyte is impregnated into a porous material.
Is sandwiched between the cathode (oxygen electrode) and the anode (fuel electrode) from both sides, and an oxidizing gas is supplied to the cathode side and a fuel gas is supplied to the anode side to generate a potential difference between the cathode and the anode. The power generation is performed by a single cell, and the cells are stacked in multiple layers via a separator to form a stack.

In a power generator using a molten carbonate fuel cell having such a configuration, when natural gas is used as a fuel, the natural gas is introduced into a reforming chamber of a reformer to reform the natural gas. The fuel gas is supplied to the anode of the fuel cell, while the cathode of the fuel cell is supplied with air as an oxidizing gas, and the cathode outlet gas discharged from the cathode is preheated air. After being used, the anode outlet gas discharged from the anode is supplied to the combustion chamber of the reformer after removing moisture, or a part of the cathode outlet gas and catalytic combustion After combustion in the reformer, the fuel is supplied to the combustion chamber of the reformer, and the combustion exhaust gas discharged from the combustion chamber of the reformer is supplied to the cathode.

In the fuel cell used in the above-described fuel cell power generator, in order to maintain the cell performance stably for a long period of time, the fuel cell must be purged when shifting from the power generation state to the stop state or the storage state. In the case of purging such a fuel cell, it may be necessary to perform a purge by, for example, supplying nitrogen gas to the cathode system and the anode system, or to perform performance purging gas or the like. By purging by supplying an atmospheric gas from a gas cylinder, a curl, or the like, the purge gas is replaced with a reaction gas to lower the battery voltage.

[0005]

However, if the nitrogen gas purge continues at a high temperature for a long period of time, the quality of the electrode material and the change of the fine structure may occur, which may adversely affect the battery performance and life. In the case of purging with a performance maintaining gas or the like, a dedicated gas supply system is required, and there is a problem that the number of facilities and the accompanying cost increase.

Accordingly, the present invention can prevent the deterioration of the battery material and the accompanying deterioration even when purging at a high temperature for a long time, and can reduce the cost by eliminating the need for a dedicated purge equipment. It is an object of the present invention to provide a fuel cell purging method that can be achieved.

[0007]

According to the present invention, there is provided a fuel cell comprising a fuel cell and a reformer, wherein a fuel gas reformed in a reforming chamber of the reformer is supplied to an anode of the fuel cell. Oxidizing gas is supplied to the cathode of the fuel cell, and a portion of the cathode outlet gas discharged from the cathode and part of the anode outlet gas discharged from the anode is burned in the first catalytic combustor. After that, another part of the cathode outlet gas and another part of the anode outlet gas are burned in the second catalytic combustor and then introduced into the combustion chamber of the reformer. Then, the combustion gas from the combustion chamber is supplied to the cathode, and a fuel cell power generation device having an anode recycling line is provided. H ₂ in the combustor Including by generating a reducing atmosphere gas by mixing the combustion gas, feeds sent to the anode through the anode recycle line, the anode outlet gas as a reducing atmosphere gas discharged from the anode, O in the second catalytic combustor _An oxidizing atmosphere gas is generated by mixing and burning with the gas containing ₂ , and is supplied to the cathode through the combustion chamber of the reformer, and the cathode outlet gas as the oxidizing atmosphere gas discharged from the cathode is again discharged. The first catalytic combustor is mixed and burned with a gas containing H ₂ to flow as a reducing atmosphere gas to the anode, and the reducing and oxidizing atmosphere is maintained by a continuous gas flow circulating between the cathode and the anode. The method for purging the fuel cell is as follows.

[0008] The reducing atmosphere gas generated in the first catalytic combustor is supplied to the anode, and the oxidizing gas generated in the second catalytic combustor is supplied to the cathode. It is possible to continuously generate a reducing atmosphere and an oxidizing atmosphere necessary for the cathode.

Further, fuel gas is used as a gas containing H ₂ to be supplied to the first catalytic combustor, and air from a plant air source is used as a gas containing O ₂ to be supplied to the second catalytic combustor. Thus, the entire purging operation can be performed at lower cost.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

The purging method for a fuel cell according to the present invention basically comprises purging by flowing a reducing atmosphere gas to the anode and an oxidizing atmosphere gas to the cathode. Is to use what is generated by a combustor used for a fuel cell power generator.

More specifically, FIG. 1 shows a fuel cell power generator used for carrying out the fuel cell purging method of the present invention, and has the following configuration.

That is, the fuel cell FC in which the tile 1 is sandwiched between the cathode 2 and the anode 3 and the reforming chamber 8a
And a reformer 8 having a combustion chamber 8b. A reforming raw material gas (natural gas) NG as a fuel is preheated by a natural gas preheater 6, and then the natural gas is supplied to a reforming chamber 8a of the reformer 8. After being introduced from the supply line 7 and reforming in the reforming chamber 8a, the fuel gas FG as the reformed gas is supplied to the anode 3 through the natural gas preheater 6 by the fuel gas supply line 9, On the other hand, to the cathode 2 of the fuel cell FC, air A as an oxidizing gas is compressed by the compressor 4 and then supplied to the cathode 2 by the air supply line 5. It is made to be performed.

Further, a part of the cathode outlet gas CG discharged from the cathode 2 to the cathode outlet gas line 10 and a part of the anode outlet gas AG discharged from the anode 3 to the anode outlet gas line 11 are 1 is introduced into the catalytic combustor 12, where it is burned and then
To the evaporator 15 through the combustion gas line 13 after being expanded by the turbine 14. The cathode outlet gas branch line 16 branched from the cathode outlet line 10 and the anode outlet line 1
The anode outlet gas branch line 17 branched from 1 is connected to a second catalytic combustor 18, and the cathode outlet gas and the anode outlet gas are burned in the second catalytic combustor 18, and then the combustion chamber 8b of the reformer 8 is burned. The combustion gas discharged from the combustion chamber 8b of the reformer 8 is supplied to the combustion gas line 1
Steam 9 is supplied to the cathode 2 of the fuel cell FC together with the air A, and the steam generated by the evaporator 15 is mixed with natural gas NG by the steam line 23 to form the reformer 8.
To the reforming chamber 8a.

A part of the cathode outlet gas is guided to the inlet side of the cathode 2 by the cathode recycle line 20 and circulated, and a part of the anode outlet gas is
An anode recycle line 22 having an adiabatic reformer 21 guides and circulates the anode 3 toward the inlet side of the anode 3. In the figure, 24, 25, 26, 27, 2
8, 29 and 30 are on-off valves.

In the method of purging a fuel cell according to the present invention, a reducing atmosphere gas to the anode 3 is generated by using the first catalytic combustor 12 used in the fuel cell power generator having the above structure, and the gas is continuously supplied to the anode 3. To be able to flush
An intermediate position of the combustion gas line 13 between the first catalytic combustor 12 and the turbine 14;
And a line 31 having an on-off valve 32 on the way.
And the above line 3 of the combustion gas line 13
An on-off valve 33 is provided on the downstream side of the connection position of No. 1, a supply line 34 of hydrogen or fuel gas FG is connected to the first catalytic combustor 12, and a supply line 35 of air A is connected to the second catalytic combustor 18. Connect.

When it becomes necessary to purge the fuel cell, an on-off valve 25 on the way of the cathode outlet gas line 10, an on-off valve 28 on the way of the anode outlet gas branch line 17 branched from the anode outlet gas line 11, and a line 31 The on-off valve 32 on the way is opened, and each on-off valve 24,
6, 27, 29, 30, and 33 are closed, and the first catalytic combustor 12 supplies H ₂ or fuel gas F as a reformed gas.
G is supplied, and H ₂ or fuel gas FG and the cathode outlet gas are mixed and burned in the first catalytic combustor 12, and H ₂ +1/2
The reducing atmosphere gas RG is generated by using a chemical reaction of O ₂ → H ₂ O so that H ₂ becomes excessive.

Next, the reducing atmosphere gas RG generated in the first catalytic combustor 12 and discharged to the combustion gas line 13 is used.
Is supplied to the anode 3 through the line 31 and the anode recycling line 22 so that the anode 3 is purged with the reducing atmosphere gas RG.

Next, the reducing atmosphere gas RG after passing through the anode 3 is led from the anode outlet gas line 11 through the branch line 17 to the second catalytic combustor 18,
The catalytic combustor 18 is supplied with air A from a plant air source as a gas containing O _2, and the reducing atmosphere gas RG as the anode outlet gas and the air A are mixed and burned so that the air becomes excessive. To generate an oxidizing atmosphere gas OG.

Subsequently, the oxidizing atmosphere gas OG generated in the second catalytic combustor 18 is supplied to the cathode 2 through the combustion chamber 8b of the reformer 8 by the combustion gas line 19, so that the cathode 2 is cooled. Purging is performed with an oxidizing atmosphere gas OG.

The oxidizing atmosphere gas OG flowing to the cathode 2 is led to a first catalytic combustor 12, where the oxidizing atmosphere gas OG is mixed and burned with H ₂ or a fuel gas FG, and is reduced from the oxidizing atmosphere gas OG. The atmosphere gas FG is converted.

Thus, when purging the fuel cell, the first catalytic combustor 12 → the anode 3 → the second catalytic combustor 18 →
The reducing atmosphere gas RG and the oxidizing atmosphere gas OG have a line configuration of a cathode 2, a first catalytic burner 12, an anode 3, and so on.
Can be circulated so as to maintain a reducing and oxidizing atmosphere with a continuous gas flow. Accordingly, there is no fear that deterioration of the battery material and deterioration of the performance due to the deterioration will occur even if the purging is performed for a long time, and the reducing atmosphere gas RG and the oxidizing atmosphere gas OG are the first devices which are included in the fuel cell power generator itself. The use of the second catalytic combustors 12 and 18 is extremely advantageous in that it is not necessary to prepare a dedicated device for purging.

In the above-described embodiment, an example in which the purging is required for a long time is described. However, the present invention can be applied to a case where the temperature is increased or decreased, and does not deviate from the gist of the present invention. Of course, various changes can be made within the range.

[0024]

As described above, according to the fuel cell purging method of the present invention, a fuel cell and a reformer are provided, and the fuel gas reformed in the reforming chamber of the reformer is supplied to the fuel cell. In addition to supplying to the anode, oxidizing gas is supplied to the cathode of the fuel cell, and the cathode outlet gas discharged from the cathode and a part of the anode outlet gas discharged from the anode are burned by the first catalytic combustor. After that, it is led to the turbine, and further, another part of the cathode outlet gas and another part of the anode outlet gas are burned in the second catalytic combustor, and then, are burned into the combustion chamber of the reformer. Introduce and supply the combustion gas from the combustion chamber to the cathode, and using a fuel cell power generation device having a configuration provided with an anode recycle line, the cathode outlet gas of the fuel cell power generation device,
A reducing atmosphere gas is generated by mixing and burning with a gas containing H ₂ in the first catalytic combustor, fed to the anode through the anode recycling line, and an anode outlet gas as a reducing atmosphere gas discharged from the anode To
An oxidizing atmosphere gas is generated by mixing and burning with a gas containing O ₂ in the second catalytic combustor, and is supplied to the cathode through the combustion chamber of the reformer. The oxidizing atmosphere gas discharged from the cathode The cathode outlet gas as above is mixed and burned again with the gas containing H ₂ in the first catalytic combustor so as to flow to the anode as a reducing atmosphere gas,
Since the reducing and oxidizing atmosphere is maintained by the continuous gas flow circulating between the cathode and the anode, it is possible to prevent the deterioration and performance deterioration of the battery material even for a long-time purge, and This eliminates the need for a dedicated purging facility and is advantageous in terms of cost. In addition, the fuel gas is used as the gas containing H ₂ to be supplied to the first catalytic combustor, and the _second gas is used.
By using the air from the plant air source as the gas containing O ₂ to be supplied to the catalytic combustor, excellent effects such as that the entire purging operation can be performed at lower cost can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a fuel cell purging method of the present invention.

[Explanation of symbols]

 2 Cathode 3 Anode 8 Reformer 8a Reforming chamber 8b Combustion chamber 12 First catalytic combustor 14 Turbine 15 Evaporator 18 Second catalytic combustor 22 Anode recycle line FC fuel cell CG Cathode outlet gas AG Anode outlet gas A Air FG Fuel gas RG Reduction atmosphere gas OG Oxidation atmosphere gas

Claims (2)

[Claims] 1. A fuel cell comprising a fuel cell and a reformer, wherein a fuel gas reformed in a reforming chamber of the reformer is supplied to an anode of the fuel cell and an oxidizing gas is supplied to a cathode of the fuel cell. And a part of the cathode outlet gas discharged from the cathode and the anode outlet gas discharged from the anode is burned in the first catalytic combustor, and then guided to a turbine. Is burned in the second catalytic combustor, and then introduced into the combustion chamber of the reformer to supply the combustion gas from the combustion chamber to the cathode. In addition, using a fuel cell power generator having a configuration provided with an anode recycling line, the cathode outlet gas of the fuel cell power generator is mixed and burned with a gas containing H ₂ in a first catalytic combustor to reduce the reducing atmosphere. Generate gas So, the feeds sent to the anode through the anode recycle line, the anode outlet gas as a reducing atmosphere gas discharged from the anode, an oxidizing atmosphere gas be mixed combustion gas containing O ₂ in the second catalytic combustor Is generated and supplied to the cathode through the combustion chamber of the reformer, and the cathode outlet gas as the oxidizing atmosphere gas discharged from the cathode is mixed again with the gas containing H ₂ in the first catalytic combustor. A method for purging a fuel cell, comprising: causing a combustion atmosphere to flow as a reducing atmosphere gas to an anode, and maintaining a reducing and oxidizing atmosphere by a continuous gas flow circulating between the cathode and the anode. . 2. A fuel gas is used as a gas containing H ₂ to be supplied to a first catalytic combustor, and O 2 is supplied to a second catalytic combustor.
_{2. The} method for purging a fuel cell according to claim 1, wherein air from a plant air source is used as the gas containing ₂ .