JPH11354143A - Fuel cell power generating set with anode circulation line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a system to connect a nitrogen filling range to an anode at the time of plant shut-down to prevent oxidation of the anode when started up. SOLUTION: An anode circulation line 3 for circulating anode exhaust gas to an anode is arranged in a power generating set provided with a fuel cell 20 comprising a cathode and the anode to generate power using cathode gas containing oxygen and anode gas containing hydrogen, a combustor 23 for burning the anode exhaust gas discharged from the anode and cathode exhaust gas discharged from the cathode, a reformer 22 for reforming fuel gas containing steam using combustion exhaust gas in the combustor 23 to be supplied to the anode as the anode gas, a carbon dioxide gas recycle line 7 for supplying combustion exhaust gas in the reformer 22 to the cathode, an air line 8 for driving a turbine using the cathode exhaust gas to generate compressed air and for supplying the compressed air to the cathode, and a starting-up heating line 11 for supplying the combustion exhaust gas to the combustor 23 at the time of start,-up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generator for circulating nitrogen gas in an anode circulation line at the time of startup to prevent oxidation of an anode.

[0002]

2. Description of the Related Art Molten carbonate fuel cells have features not found in conventional power generators, such as high efficiency and low environmental impact, and have attracted attention as power generation systems following hydro, thermal and nuclear power. Currently, intensive research is underway.

FIG. 2 is a diagram showing an example of a power generation facility using a molten carbonate fuel cell using city gas as fuel. In FIG. 2, a power generation facility is a reformer 2 for reforming a fuel gas (city gas) mixed with steam into an anode gas containing hydrogen.
2 and a fuel cell 20 that generates electricity from a cathode gas containing oxygen and an anode gas containing hydrogen. The anode gas produced in the reformer 22 is supplied to the fuel cell 20 through the anode gas line 2 and Most of the battery 20 is consumed to become anode exhaust gas, which enters the catalytic combustor 23 through the anode exhaust gas line 4, burns together with the cathode exhaust gas, and is supplied to the heating chamber 22 b of the reformer 22.

[0004] The combustion exhaust gas discharged from the heating chamber 22 b of the reformer 22 is supplied to the cathode through the carbon dioxide gas recycling line 7. A part of the cathode exhaust gas is supplied to the catalytic combustor 23, the other is supplied to the turbine compressor 25,
Compressed air is generated and supplied to the cathode by an air line 8. The exhaust gas from the turbine compressor 25 is supplied to a steam generator 26 to generate steam, supplied to the fuel gas line 1 by the steam line 9, mixed with the fuel gas, and supplied to the reformer 22. The turbine compressor 25 has a combustor 27.
Is provided, air and fuel gas are supplied from the compressor 25, and combustion gas is supplied to the turbine compressor 25 so that compressed air can be generated even when there is no cathode exhaust gas.

The heating line 11 for starting is connected to the combustor 23, the combustion gas is generated by the burner unit 29 at the time of starting, the combustion gas is supplied to the combustor 23 having a low temperature, and the reforming reaction of the reformer 22 is performed. Is performed early and normally, and the system is raised to the operating temperature with high-temperature exhaust gas. A nitrogen supply line 12 is connected to the fuel gas line 1 so that when the fuel cell power generator is stopped, each system is filled with nitrogen to prevent oxidation. During startup, the temperature of each system is increased to the load operating temperature while replacing this nitrogen with working gas. For this reason, the nitrogen supply line 12 is provided with a considerably large nitrogen production facility 30.

When starting the fuel cell power generator, first, the combustor 2
7 is supplied with fuel gas, and the turbine compressor 25 is driven by the combustion gas.
, The turbine compressor 25 is completely started, and the supply of compressed air and the supply of steam by the steam generator 26 are enabled. Next, the burner unit 29 of the start-up heating line 11 is ignited to supply the combustion exhaust gas to the combustor 23, thereby increasing the temperature of the combustor 23 and using the combustion exhaust gas to convert the reformer 2.
2 is heated, part of the exhaust gas is released from the shut-off valve 43 to release nitrogen gas, and part of the exhaust gas is circulated through the cathode by the carbon dioxide gas recycle blower 28 to replace the nitrogen gas with the combustion exhaust gas. Increase the temperature. When the temperature rises to a predetermined temperature, fuel gas and steam are sent to the catalytic combustor 23 via the reforming chamber 22 and the anode, and compressed air is sent from the air line 8 to the catalytic combustor 23 via the cathode to burn and burn. The exhaust gas is sent to the heating chamber 22b of the reformer 22,
By performing the reforming action, the combustion exhaust gas is sent to the carbon dioxide gas recycling line 7. As these operations are repeated, the temperature of each system and device reaches the operating temperature, the startup is completed, and the load operation is started.

[0007]

When the fuel cell power generator is stopped, each system of the plant is filled with nitrogen gas, so that a large capacity nitrogen production facility is required.
However, not all systems need to be filled with nitrogen. What is needed is a system connected to the anode. In this system, nitrogen gas is used to prevent oxidation of the anode even when the temperature is increased during startup.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a system for connecting a nitrogen filling range to an anode when a plant is stopped to prevent oxidation of the anode at the time of startup. The purpose is to provide.

[0009]

According to the first aspect of the present invention, there is provided a fuel cell comprising a cathode and an anode, generating electricity from a cathode gas containing oxygen and an anode gas containing hydrogen, and discharging the fuel cell from the anode. A combustor that burns the anode exhaust gas and the cathode exhaust gas discharged from the cathode, a reformer that reforms a fuel gas containing water vapor with the combustion exhaust gas of the combustor, and supplies the fuel gas to the anode as an anode gas; A carbon dioxide gas recycle line for supplying combustion exhaust gas to the cathode, an air line for driving the turbine by the cathode exhaust gas to generate compressed air and supply the compressed air to the cathode, and a start-up for supplying the combustion exhaust gas to the combustor at startup. A heating line, and an anode circulation line for circulating anode exhaust gas to the anode. I do.

When the anode circulation line for circulating the anode is provided and the fuel cell power generator is stopped, the anode circulation line may be filled with nitrogen, so that the capacity of the nitrogen production apparatus can be greatly reduced. Alternatively, it can be supplied by a nitrogen cylinder. Also, at the time of startup, the temperature is increased while circulating nitrogen gas to the anode, and the nitrogen gas is replaced with a working gas, so that much nitrogen is not required and replacement is easily performed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a fuel cell power generation device according to an embodiment. The power generation equipment includes a reformer 22 that reforms a fuel gas (city gas) mixed with steam into an anode gas containing hydrogen, a fuel cell 20 that generates electricity from a cathode gas containing oxygen and an anode gas containing hydrogen, Combustion of anode exhaust gas and cathode exhaust gas and combustion exhaust gas reformer 2
2 is provided with a catalytic combustor (combustor) for performing a reforming reaction.

The fuel gas line 1 is connected to a fuel preheater 24 via a shutoff valve 44, and the fuel preheater 24 is connected to a reformer 22.
And heat-exchanges with the anode gas mainly composed of hydrogen gas generated in the reforming chamber 22a to heat the city gas and the steam supplied from the steam line 9. The anode gas that has undergone heat exchange in the fuel preheater 24 is supplied to the anode through the anode gas line 2.

An anode circulation line 3 for circulating the anode exhaust gas back to the anode inlet is provided.
To prevent oxidation of the anode.

An anode exhaust gas containing a combustion component is supplied to the catalytic combustor 23 from an anode exhaust gas line 4, and a cathode exhaust gas containing oxygen is supplied from a cathode exhaust gas line 5, and burns to produce a high-temperature combustion exhaust gas. 6, the combustion exhaust gas is supplied to the heating chamber 22b, and after heating the reforming chamber 22a, the exhaust gas is supplied to the cathode by the carbon dioxide gas recycling blower 28 through the carbon dioxide gas recycling line 7. A cathode circulation line 10 that branches off from the cathode exhaust gas line 5 and returns to the cathode inlet is provided. The cathode exhaust gas is circulated to the cathode by the carbon dioxide gas recycle blower 28 via the flow rate control valve 48.

Cathode exhaust gas is supplied from a cathode exhaust gas line 5 to a turbine compressor 25, which drives a turbine to generate compressed air by a coaxially connected compressor and supplies the compressed air to the cathode through an air line 8. The exhaust gas of the turbine is supplied to a steam generator 26 to generate steam, and is supplied to the fuel gas line 1 by a steam line 9. The turbine compressor 25 is provided with a combustor 27, which is supplied with fuel gas and compressed air for combustion, supplies combustion exhaust gas to the turbine, and drives and compresses the turbine when the cathode exhaust gas is not yet sufficiently generated at the time of startup. Air is generated, and the exhaust gas generates steam in the steam generator 26.

The start-up heating line 11 is connected to the catalytic combustor 23 and supplies combustion exhaust gas at the time of start-up. The start-up heating line 11 is provided with a burner unit 29, receives city gas as a fuel gas, and compresses it from the air line 8. Combustion by air. The nitrogen supply line 12 is connected to the fuel gas line 1. The nitrogen supply source is a simple device consisting of only the nitrogen cylinder 32. In FIG. 1, reference numerals 40 to 46 denote shut-off valves, reference numerals 47 to 48 denote flow control valves, and reference numerals 49 to 50 denote check valves.

Next, the startup of the fuel cell power generator will be described. Although the anode circulation line 3 is filled with nitrogen, it is further filled at the time of startup. Fuel gas is supplied to the combustor 27 to generate combustion gas, and the turbine compressor 25
To generate compressed air and supply it to the combustor 27. Further, steam is generated by the steam generation device 26 using the turbine exhaust gas.

It is started by the following procedure. The shutoff valve 46 of the nitrogen supply line 12 is opened to fill the anode circulation line 1 with nitrogen via the reformer 22 and the fuel preheater 24, and the anode circulation blower 31 is operated to start circulation of nitrogen. The burner unit 29 of the start-up heating line 11 is ignited, and the high-temperature combustion gas is supplied to the catalytic combustor 23 at 700 ° C.
Heat to a degree. Closing the shutoff valves 40, 41, 42, 43
And the high-temperature combustion gas passes through the heating chamber 22b,
3 from the system. The anode circulation blower 31 continues to operate, the carbon dioxide gas recycle blower 28 also starts operating, and in parallel with the temperature rise of the catalytic combustor 23 and the reformer 22, the shut-off valve 42 is slightly opened to raise the temperature of the cathode side. I do.

When the temperature of the reformer 22 reaches about 700 ° C., the shut-off valves 44 and 45 are opened to supply fuel gas and steam to the reformer 22, and the reformed gas (anode gas) is supplied to the reforming chamber 22a. Is generated and supplied to the anode. On the cathode side, when the fuel cell temperature becomes 300 to 350 ° C., the shut-off valve 40 is opened, and air is introduced from the air line 8. The shut-off valve 42 is adjusted in the opening direction to adjust the rotation speed of the carbon dioxide gas recycle blower 28 to increase the fuel cell temperature. At the same time, the shut-off valve 43 is closed and the shut-off valve 41 is opened to complete the startup.

In the above, the fuel cell temperature is 30
From 0 to 350 ° C., instead of opening the shut-off valve 42,
The shutoff valve 40 may be opened to supply air to the cathode side.

[0021]

As is apparent from the above description, according to the present invention, the anode circulation line is provided, and when the fuel cell is stopped and started, only this line needs to be filled with nitrogen gas. Equipment is not required, and manufacturing and operating costs can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a conventional fuel cell power generator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel gas line 2 Anode gas line 3 Anode circulation line 4 Anode exhaust gas line 5 Cathode exhaust gas line 6 Combustion exhaust gas line 7 Carbon dioxide gas recycling line 8 Air line 9 Steam line 10 Cathode circulation line 11 Starting heating line 12 Nitrogen supply line 20 Fuel Battery 22 Reformer 22a Reforming chamber 22b Heating chamber 23 Catalytic combustor 24 Fuel preheater 25 Turbine compressor 26 Steam generator 27 Combustor 28 Carbon dioxide recycle blower 30 Nitrogen production facility 32 Nitrogen cylinder 40, 41, 42, 43 , 44,45 46 Shut-off valve 47,48 Flow control valve 49,50 Check valve

Claims (1)

[Claims] 1. A fuel cell, comprising a cathode and an anode, generating electricity from a cathode gas containing oxygen and an anode gas containing hydrogen, a combustor for burning anode exhaust gas discharged from the anode and cathode exhaust gas discharged from the cathode, A reformer that reforms a fuel gas containing water vapor with the combustion exhaust gas of the combustor and supplies the fuel gas to the anode as anode gas, a carbon dioxide gas recycling line that supplies the combustion exhaust gas of the reformer to the cathode, and a turbine using the cathode exhaust gas Circulating anode exhaust gas to the anode in a power generating apparatus comprising: an air line that drives compressed air to supply compressed air to the cathode; and a startup heating line that supplies combustion exhaust gas to the combustor at startup. Cell power generation with anode circulation line characterized by having an anode circulation line apparatus.