JPH1167238A - Fuel cell power generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power of a carbon dioxide gas recycling blower and eliminate the need for a condenser for preventing white smoke by branching part of excess steam generated in an exhaust heat recovery steam generating device, and supplying it from a steam branching line to the outlet side of the carbon dioxide gas recycling blower. SOLUTION: Part of cathode exhaust gas is supplied to a catalytic combustion device 23, other part is supplied to a cathode circulation line 3, and the remainder is supplied to an exhaust heat utilizing line 6 to rotate a turbine of a turbine compressor 27. Its exhaust gas is supplied to an exhaust heat recovery steam generating device 30, and supplied water is heated to generate steam. The steam generated is supplied to a fuel gas line 1. The excess steam is supplied to a cathode, and the flow rate of cathode gas supplied to the cathode with a carbon dioxide gas recycling blower 26 is reduced to 9/10. The capacity of the blower can be made small and cost is reduced.

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 supplying steam to a cathode to reduce the output of a carbon dioxide gas recycling blower.

[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.

[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 recycling blower 26 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 recycle blower 26 to supply oxygen required for a cathode cell reaction. Cathode exhaust gas discharged from the cathode is supplied to the cathode through the cathode circulation line 3 to the inlet side of the carbon dioxide gas recycle blower 26. The cathode exhaust gas, the combustion exhaust gas, and the air are mixed to form a cathode gas and supplied to the cathode.

The cathode gas enters a cathode circulation line 3 circulating through the cathode and undergoes a cell reaction in the fuel cell 20 to become a high-temperature cathode exhaust gas. A part of the cathode gas circulates back to the cathode circulation line 3 and the other part is circulated. The power is supplied to the catalytic combustor 23 by the cathode exhaust gas line 5, and the remainder is recovered by a turbine compressor 27 that drives a compressor that compresses air in an exhaust heat utilization line 6, and then further recovered by an exhaust heat recovery steam generator 30. Heat energy is recovered and discharged out of the system. 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. A steam discharge line 11 that branches off from the steam line 9 and discharges steam to the atmosphere is provided. The branched steam is condensed through a condenser 31 to prevent the generation of white smoke, and is then discharged to the atmosphere.

[0006]

The steam generated by the exhaust heat recovery steam generator 30 enters the fuel gas line 1 through the steam line 9 and mixes with the fuel gas to be converted into an anode gas containing hydrogen by the reformer 22. As a matter of fact, since the amount of generated steam is larger than that required for reforming, a steam discharge line 11 is provided to discharge to the atmosphere. When the steam is directly discharged to the atmosphere, white smoke is emitted and is discharged through the condenser 31. This condenser 31 is a factor that increases the plant cost. Further, the carbon dioxide gas recycle blower 26 is used for circulating the cathode gas, and the amount of the cathode gas is about 10 times that of the anode gas. Therefore, the driving power is large and the efficiency of the plant is hindered.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a fuel cell power generator that reduces the power of a carbon dioxide gas recycle blower by supplying steam to a cathode.

[0008]

To achieve the above object, according to the first aspect of the present invention, a fuel cell comprising a cathode and an anode and generating electricity from a cathode gas containing oxygen and an anode gas containing hydrogen, and a fuel cell discharged from the anode are provided. A reformer that burns the anode exhaust gas and the 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 recycling line that supplies a cathode with a blower, a cathode circulation line that circulates part of the cathode exhaust gas to supply the inlet side of the carbon dioxide gas recycling blower, and supplies air to the outlet side of the carbon dioxide gas recycling blower Air line and exhaust heat mixed with fuel gas by heating the feed water by the cathode exhaust gas to generate steam Yield comprising a steam generator, and a steam branch line for supplying the output side of the carbon dioxide gas recycling blower branches a part of the steam generated in the exhaust heat recovery steam generator.

[0009] A steam branch line is provided to supply surplus steam generated by the exhaust heat recovery steam generator to the cathode. Since the circulation flow rate of the anode gas can be reduced by the supplied steam flow rate, the power of the carbon dioxide gas recycling blower used for this circulation can be reduced. Further, since the vapor is not released to the atmosphere, a condenser for preventing white smoke is not required, and the cost is reduced.

[0010]

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 anode exhaust gas discharged from the fuel cell 20 is supplied to the catalytic combustor 23 by the anode exhaust gas line 4.
And combusts with a part of the cathode exhaust gas using a combustion catalyst. The reformer 22 includes a reforming chamber for converting 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 catalytic combustor 23. 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, mixed with the cathode exhaust gas, and supplied as cathode gas.

The city gas containing natural gas as a component is supplied to the desulfurizer 2
5, is supplied by the fuel gas line 1, mixed with the steam from the steam line 9, preheated by the fuel preheater 24, and enters the reforming chamber of the reformer 22. The anode gas generated from the reforming chamber is supplied to the fuel preheater 24 by the anode gas line 2.
After the fuel gas is heated by the above, the fuel gas is supplied to the anode of the fuel cell 20. At the cathode of the fuel cell 20, the carbon dioxide from the carbon dioxide recycling line 7, the cathode exhaust gas from the cathode circulation line 3, and the oxygen from the air line 8 are mixed to form a cathode gas, which is further combined with a steam branch line. A mixed gas to which steam from 10 is added is supplied. The fuel cell 20 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. Cathode exhaust gas generated by the reaction at the cathode is partially supplied to the catalytic combustor 23 through the cathode exhaust gas line 5,
Another part is supplied to the cathode circulation line 3, and the remaining part is supplied to the exhaust heat utilization line 6.

An anode exhaust gas and a cathode exhaust gas of the fuel cell 20 are supplied to the catalytic combustor 23. 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 recycling line 7 is provided with a carbon dioxide gas recycling blower 26, the cathode circulation line 3 is connected to the inlet side of the carbon dioxide gas recycling blower 26, and the air line 8 and the steam branch line 10 are connected to the outlet side. Are connected, and gas from these lines 3, 7, 8, and 10 is sent to the cathode. The cathode circulation line 3 circulates a part of the cathode exhaust gas to the cathode, and the flow rate is adjusted by a flow control valve 32.

A part of the cathode exhaust gas is supplied to a waste heat utilization line 6.
After driving the turbine of the turbine compressor 27, it is supplied to the exhaust heat recovery steam generator 30. In the exhaust heat recovery steam generator 30, feed water is converted into steam by exhaust gas that drives the turbine of the turbine compressor 27, and is 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 steam line 9 is provided with a flow control valve 33 for controlling the flow rate of steam supplied to the fuel gas line 1. A steam branch line 10 is provided branching from the steam line 9, and supplies steam to the outlet side of the carbon dioxide gas recycle blower 26 at the cathode inlet. A flow control valve 34 is provided in the steam branch line 10 to control the amount of steam to be supplied. The air compressed by the turbine compressor 27 is pressurized by the air blower 28 of the air line 8 and supplies air to the outlet of the carbon dioxide gas recycle blower 26 at the cathode inlet.

A part of the cathode exhaust gas is a catalytic combustor 23.
And the other part is supplied to the cathode circulation line 3, the remainder is supplied to the exhaust heat utilization line 6 to rotate the turbine of the turbine compressor 27, and the exhaust gas is supplied to the exhaust heat recovery steam generator 30. Then, the feedwater is heated to generate steam. This steam is supplied to the fuel gas line 1, but this steam amount does not require all of the generated steam amount, and a considerable amount is surplus. This surplus amount is, for example, about one tenth of the cathode gas circulating through the cathode. Therefore, by supplying the surplus steam amount to the cathode, the flow rate of the cathode gas pushed into the cathode by the carbon dioxide gas recycle blower 26 can be reduced to about 9/10. As a result, the driving power of the carbon dioxide recycle blower 26 can be reduced, and its rated capacity can be reduced, so that the production or purchase cost can be reduced.

[0017]

As is apparent from the above description, the present invention can reduce the driving power of the carbon dioxide gas recycle blower by supplying surplus steam generated by the exhaust heat recovery steam generator to the cathode. Further, the capacity of the blower can be reduced, and the production or purchase cost can be reduced. In addition, since it is not necessary to provide a condenser for preventing white smoke and release excess steam to the atmosphere as in the related art, a condenser is not required, which contributes to cost reduction.

[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 Cathode circulation line 4 Anode exhaust gas line 5 Cathode exhaust gas line 6 Exhaust heat utilization line 7 Carbon dioxide gas recycling line 8 Air line 9 Steam line 10 Steam branch line 11 Steam release line 20 Fuel cell 22 Reforming Apparatus 23 Catalytic combustor 24 Fuel preheater 25 Desulfurizer 26 Carbon dioxide gas recycle blower 27 Turbine compressor 28 Air blower 30 Exhaust heat recovery steam generator 31 Condenser 32,33,34 Flow control valve

Claims (1)

[Claims] 1. A fuel cell comprising a cathode and an anode, which generates electricity from a cathode gas containing oxygen and an anode gas containing hydrogen, and an anode exhaust gas discharged from the anode and a cathode exhaust gas discharged from the cathode are burned. A reformer for reforming a fuel gas containing water vapor and supplying it to the anode as an anode gas, a carbon dioxide gas recycling line for supplying the combustion exhaust gas of the reformer to the cathode with a carbon dioxide gas recycling blower, and a part of the cathode exhaust gas A cathode circulation line for supplying air to the inlet side of the carbon dioxide gas recycling blower, an air line for supplying air to the outlet side of the carbon dioxide gas recycling blower, and heating the feed water by the cathode exhaust gas to generate steam. The exhaust heat recovery steam generator mixed into the fuel gas and the steam generated by the exhaust heat recovery steam generator A fuel cell power generator, comprising: a steam branch line that partially branches and supplies the branch to the outlet side of the carbon dioxide gas recycling blower.