JPH1167252A - Fuel cell power generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To specify a shut-off valve and a flow control valve of an exhaust line as low temperature specification to reduce plant cost by making the capacity of a cooling device of purge gas for a housing container of a fuel cell equal to the total amount of the flow rate of the purge gas and the exhausting flow rate of residual gas in emergency stop. SOLUTION: City gas and steam from waste heat recovery device 30 are mixed, the mixture is reformed in a reformer 22, obtained anode gas containing H2 is supplied to an anode A of a fuel cell 20, and air from a turbine compressor 28 and combustion exhaust gas from the reformer 22 are mixed, obtained cathode gas containing O2 and CO2 is supplied to a cathode C to generate electric power. Part of the combustion exhaust gas is branched, cooled in a cooling device 50, and supplied to a housing 21 of a fuel cell 20 as purge gas with a purge gas blower 38 through a steam separator 37. An exhaust line having a shut-off valve 52 and a flow control valve 54 is connected to the outlet of the cooling device 50, and the capacity of the cooling device 50 is made equal to the total amount of the flow rate of purge gas and the exhausting flow rate of the residual gas in emergency stop.

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 which discharges residual gas in a plant to the atmosphere when the plant is stopped in an emergency.

[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 the figure, a power generation facility is a reformer 22 for reforming a fuel gas (city gas) mixed with steam into an anode gas containing hydrogen.
And a fuel cell 20 that generates power from a cathode gas containing oxygen and an anode gas containing hydrogen.
The anode gas produced in Step 2 is supplied to the fuel cell 20 through the anode gas line 2, and most of the anode gas is consumed in the fuel cell 20 to become the anode exhaust gas. Supplied. The fuel cell 20 is stored in a storage container 21.

[0004] The catalytic combustor 23 burns combustible components (hydrogen, carbon monoxide, methane, etc.) in the anode exhaust gas to generate a high-temperature combustion exhaust gas, which is supplied to a heating chamber of the reformer 22 and used by the combustion exhaust gas. The reforming chamber is heated, and the fuel gas is reformed by the reforming catalyst in the reforming chamber to produce anode gas. The anode gas exchanges heat with the fuel gas mixed with the steam flowing through the fuel gas line 1 by the fuel preheater 24, and after being cooled, is supplied to the anode of the fuel cell 20. Further, the combustion exhaust gas exiting the heating chamber is supplied to the cathode by the carbon dioxide gas blower 32 in the carbon dioxide gas recycling line 7. The combustion exhaust gas contains a large amount of carbon dioxide, and serves as a supply source of carbon dioxide required for the battery reaction. Air from the air line 8 is supplied to the outlet side of the carbon dioxide gas blower 32 to supply oxygen required for a cathode cell reaction. Part of the cathode exhaust gas discharged from the cathode is supplied to the cathode by the circulation line 3. The cathode exhaust gas, the combustion exhaust gas, and the air are mixed to form a cathode gas, which is supplied to the cathode.

The cathode gas undergoes a cell reaction in the fuel cell 20 to form a high-temperature cathode exhaust gas, a part of which is circulated to the cathode by the circulation line 3, and another part is supplied to the catalytic combustor 23 by the cathode exhaust line 5. The remainder is recovered by a turbine compressor 28 that drives a compressor that compresses air in a waste heat utilization line 6, and then heat energy is recovered by a waste heat recovery steam generator 30 to be discharged outside the system. You. The steam generated by the exhaust heat recovery steam generator 30 enters the fuel gas line 1 through the steam line 9, mixes with the fuel gas, and is sent to the reformer 22.

[0006] A part of the combustion exhaust gas discharged from the reformer 22 is cooled by a cooler 36 in a purge gas line 12 and water is removed by a steam-water separator 37. Supplied. Since the combustion exhaust gas has a low oxygen content and a large amount of carbon dioxide gas, it is used as suitable for a place such as the fuel cell 20 where an anode gas containing hydrogen is used. The purge gas in the storage container 21 contains carbon dioxide gas, and the purge gas discharge line 13
Is discharged to the inlet side of the carbon dioxide blower 32 and enters the cathode.

[0007] A discharge line 14 is connected to the carbon dioxide gas recycle line 7 and safely discharges residual gas in the plant to the atmosphere during an emergency stop of the plant. The discharge line 14 is provided with a shut-off valve 40 that is opened when the gas is released, and a flow control valve 42 that adjusts the flow rate of the released gas.

[0008]

The temperature of the residual gas in the plant released at the time of emergency stop of the plant reaches about 650 ° C. During normal operation, it is necessary to completely shut off the high-temperature combustion exhaust gas from the carbon dioxide gas recycling line 7. Therefore, high-temperature specification valves are used for the shut-off valve 40 and the flow control valve 42, which are considerably expensive. , Raising plant costs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made to reduce the cost by using a low-temperature specification for a shutoff valve and a flow control valve of a gas discharge line by cooling and discharging residual gas in a plant. It is an object of the present invention to provide a fuel cell power generator.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a fuel cell comprising a cathode and an anode, and generating electricity from a cathode gas containing oxygen and an anode gas containing hydrogen. A storage container, a reformer that burns anode exhaust gas discharged from the anode and cathode exhaust gas discharged from the cathode, reforms a fuel gas containing water vapor with the heat, and supplies the reformed fuel gas to the anode as anode gas; A carbon dioxide gas recycle line for supplying the combustion exhaust gas from the reformer to the cathode, a discharge line connected to the carbon dioxide gas recycle line and discharging the residual gas in the device via a cooler, a shutoff valve, and a flow control valve; A purge gas line connected between the cooler and the shut-off valve and connected to the storage container via a steam separator and a purge gas blower. .

[0011] The purge gas line cools the combustion exhaust gas from the reformer with a cooler and supplies it to the storage container. The capacity of this cooler is defined as the total amount of the flow rate of the residual gas discharged at the time of emergency stop of the plant and the flow rate of the combustion exhaust gas supplied to the storage container 21. After the residual gas is cooled by this cooler, it is discharged to the combustion device through the shut-off valve and the flow control valve, so that the shut-off valve and the flow control valve can be procured with low-temperature specifications, reducing plant costs. Can be achieved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a fuel cell power generation device according to an embodiment of the present invention. In this figure, FIG.
Those having the same functions as those described above are denoted by the same reference numerals. The fuel cell power generator includes a reformer 22 that reforms a fuel gas containing steam into an anode gas containing hydrogen, and a fuel cell 2 that generates electricity from the anode gas and a cathode gas containing oxygen and carbon dioxide.
0. The fuel cell 20 is stored in a storage container 21. The anode exhaust gas discharged from the fuel cell 20 is supplied to the catalytic combustor 23 through the anode exhaust gas line 4 and burns using a combustion catalyst together with a part of the cathode exhaust gas containing oxygen. The reformer 22 comprises a reforming chamber and a catalytic combustor 23, which convert a city gas containing water vapor into a reformed gas by a catalyst.
And a heating chamber for heating the reforming chamber with the combustion exhaust gas from the furnace. Combustion exhaust gas containing carbon dioxide is supplied to the cathode by a carbon dioxide gas recycle line 7, air containing oxygen is supplied by an air line 8, and a part of the cathode exhaust gas is circulated by a circulation line 3, and these are mixed. And supplied as cathode gas. The amount of circulating gas in the circulation line 3 is adjusted by a flow control valve 56.

The city gas containing natural gas as a component is supplied by a fuel gas line 1, and after removing sulfuric acid in a desulfurizer 26, is mixed with steam from a steam line 9 to form a fuel preheater 2.
The preheater 4 enters the reforming chamber of the reformer 22. The anode gas generated from the reforming chamber is heated by the fuel preheater 24 through the anode gas line 2 and then heated by the fuel cell 20.
Is supplied to the anode. At the cathode of the fuel cell 20, the carbon dioxide from the carbon dioxide gas recycling line 7, the air from the air line 8, and the cathode exhaust gas from the circulation line 3 are mixed to form a cathode gas. Supplied by Fuel cell 2
Numeral 0 is supplied with the anode gas and the cathode gas to generate power. Anode exhaust gas containing steam and unburned components is discharged by the reaction at the anode, and supplied to the catalytic combustor 23 through the anode exhaust gas line 4. A part of the cathode exhaust gas generated by the reaction at the cathode is circulated to the cathode by the circulation line 3, another part is supplied to the catalytic combustor 23 by the cathode exhaust line 5, and the remaining part is to the exhaust heat utilization line 6. Supplied.

The catalytic combustor 23 is supplied with the anode exhaust gas and the cathode exhaust gas of the fuel cell 20. Since the fuel utilization of the fuel cell is about 80%, the anode exhaust gas contains 20%.
% Of fuel components. Cathode exhaust gas contains oxygen necessary for combustion. The combustion exhaust gas from the heating chamber of the reformer 22 contains carbon dioxide, which is necessary for the battery reaction at the cathode, and is supplied to the cathode by the carbon dioxide gas recycling line 7.

The carbon dioxide gas recycle line 7 is provided with a carbon dioxide gas blower 32. The circulation line 3 is connected to the inlet of the carbon dioxide gas blower 32, and the air line 8 is connected to the outlet of the carbon dioxide blower 32. , 7, and 8 are sent to the cathode. A part of the cathode exhaust gas is supplied to the exhaust heat utilization line 6, and after driving the turbine compressor 28, is supplied to the exhaust heat recovery steam generator 30. In the heat recovery steam generator 30, the feed water is supplied to the turbine compressor 28.
The exhaust gas that drives the turbine is turned into steam and supplied to the fuel gas line 1 through the steam line 9. The exhaust gas from the exhaust heat recovery steam generator 30 is released to the atmosphere.

The air enters the compressor of the turbine compressor 28, is pressurized, and is supplied to the air line 8 via a check valve 59. The air is supplied to the air blower 3 by the bypass line 10.
4 and supplied to the air line 8. A check valve 58 is provided on the inlet side of the air blower 34, and a tie line 11 connecting the compressor outlet side is provided. The air blower 34 is used as a backup for the turbine compressor 28. When the plant is started, the amount of cathode exhaust gas is small, so that the air blower 34 driven by an electric motor is used.

A discharge line 16 is provided which branches off from the carbon dioxide gas recycling line 7. The discharge line 16 is disposed like a cooler 50, a shutoff valve 52, and a flow control valve 54 from the branch point. Purge gas line 15 for cooling and supplying the combustion exhaust gas from reformer 22 to containment vessel 21
Has a steam-water separator 37 that branches off from the cooler 50 and the shut-off valve 52 of the discharge line 16 to separate moisture from the cooled combustion exhaust gas, and a purge gas blower 38 that sends the separated gas to the storage container 21. And is connected to the storage container 21. The capacity of the cooler 50 is the total amount of the residual gas release amount and the combustion exhaust gas supply amount to the storage container 21. A purge gas discharge line 13 is provided from the storage container 21 to the inlet side of the carbon dioxide blower 32, and the purge gas in the storage container 21 is sent to the cathode. Since this purge gas contains carbon dioxide, it is used at the cathode. The purge gas discharge line 13 is provided with a differential pressure control valve 57,
The pressure in the storage container 21 is reduced to a pressure on the inlet side of the carbon dioxide blower 32.

Since the shut-off valve 52 and the flow control valve 54 of the discharge line 16 need only process low-temperature cooled residual gas, they may be low-temperature-specific valves. Since the gas is at a low temperature, some leakage from the shutoff valve 52 is allowed. Thereby, the procurement cost of the shutoff valve 52 and the flow control valve 54 is greatly reduced.

[0019]

As is apparent from the above description, according to the present invention, the discharge line is provided with a cooler shared with the purge gas line, the residual gas in the plant at the time of emergency stop of the plant is cooled, and the shut-off valve and the flow control are performed. Since the valve and the low temperature specification are used, it is possible to avoid the use of a high temperature exhaust gas discharge valve which is technically problematic, thereby improving the reliability of the equipment constituting the plant. Further, the procurement cost of these valves is greatly reduced, and the plant cost can be reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a fuel cell power generation device according to an embodiment of the present invention.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel gas line 2 Anode gas line 3 Circulation line 4 Anode exhaust gas line 5 Cathode exhaust gas line 6 Exhaust heat utilization line 7 Carbon dioxide gas recycle line 8 Air line 9 Steam line 10 Air bypass line 11 Tie line 13 Purge gas discharge line 15 Purge gas line 16 Release line 20 Fuel cell 21 Container 22 Reformer 23 Catalytic combustor 24 Fuel preheater 26 Desulfurizer 28 Turbine compressor 30 Exhaust heat recovery steam generator 32 Carbon dioxide blower 34 Air blower 37 Steam separator 38 Purge gas blower 50 Cooling Container 52 Shutoff valve 54, 56 Flow control valve 57 Differential pressure control valve 58, 59 Check valve

Claims (1)

[Claims] 1. A fuel cell comprising a cathode and an anode and generating electricity from a cathode gas containing oxygen and an anode gas containing hydrogen, a storage container for storing the fuel cell, an anode exhaust gas discharged from the anode and an anode exhaust gas discharged from the cathode. A reformer that burns the cathode exhaust gas, reforms a fuel gas containing water vapor with the heat, and supplies the anode gas as an anode gas, a carbon dioxide gas recycling line that supplies the combustion exhaust gas from the reformer to the cathode, A discharge line connected to the carbon dioxide gas recycle line and discharging the residual gas in the device through a cooler, a shutoff valve, and a flow control valve, and a steam-water separator and a purge gas blower connected between the cooler and the shutoff valve And a purge gas line connected to the storage container through the storage container.