JPH10294119A - Fuel cell power generation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively use surplus energy, and increase efficiency in a fuel cell by burning anode exhaust gas and cathode exhaust gas, reforming fuel gas by its heat, supplying reformed combustion exhaust gas to a cathode, generating steam by heating supply water by the cathode exhaust gas, mixing it in the fuel gas, and supplying the cathode exhaust gas to a turbine driving device. SOLUTION: In cathode exhaust gas generated by reaction at a cathode, a part circulates by returning to a circulating line 3, the other part is supplied to a catalytic combustor 22b by a cathode exhaust gas line 5, and a residual part is supplied to an exhaust heat utilization line 6. Anode exhaust gas and cathode exhaust gas of a fuel cell 20 are supplied to the catalytic combustor 22b. A fuel component of about 20% is contained in the anode exhaust gas, and oxygen necessary for combustion is contained in the cathode gas. A part of the cathode gas is supplied to the exhaust heat utilization line 6, and is supplied to a steam generator 30 after driving the turbine of a turbine compressor 29.

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 driving a blower of a carbon dioxide gas recycling line and a cathode circulation line by using exhaust heat of cathode exhaust gas.

[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 the fuel cell 20 is supplied to the fuel cell 20 through the anode gas line 2, and the majority of the anode gas is consumed in the fuel cell 20 to become the anode exhaust gas. It is supplied to the combustion chamber.

[0004] In the reformer 22, combustible components (hydrogen, carbon monoxide, methane, etc.) in the anode exhaust gas are burned in a combustion chamber to generate a high-temperature combustion gas, which is used to heat the reforming chamber. 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. The flue gas leaving the combustion chamber is cooled by an air preheater 26 in a flue gas line 7 and then cooled by a condenser 4.
4. Water is removed through the steam separator 46, pressurized by the low-temperature blower 34, combined with the air from the air line 8 and heated by the air preheater 26 to become a cathode gas. The combustion exhaust gas contains a large amount of carbon dioxide, and serves as a source of carbon dioxide necessary for the battery reaction.

The cathode gas enters a cathode circulation line 3 circulating through the cathode and reacts in the fuel cell 20 to produce a high-temperature cathode exhaust gas. Part of the cathode gas circulates back to the cathode circulation line 3 and part of the cathode gas is circulated. Exhaust gas line 5
Is supplied to the combustion chamber of the reformer 22, and the remainder is recovered by the compressor 28 for compressing air in the exhaust heat utilization line 6 and the turbine compression for driving the generator, and the power is recovered by the generator 28. The heat energy is recovered by the generator 30 and discharged out of the system. The electric power generated by the generator is used to drive the low-temperature blower 34 of the combustion exhaust gas line and the high-temperature blower 36 of the cathode circulation line 3. 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]

In such a fuel cell device, the condenser 44, the steam separator 4
6, the gas containing carbon dioxide gas was supplied to the circulation line 3. However, by supplying the high-moisture combustion exhaust gas from which water has not been removed recently to the cathode, the efficiency of the fuel cell can be improved. It is planned. In this case, the reformer 22
A carbon dioxide gas recycle line for directly supplying combustion exhaust gas to the cathode is provided.
Is supplied. When the combustion exhaust gas is directly supplied to the cathode as described above, the thermal energy that has been conventionally released in the condenser 44 is supplied to the cathode, so that the cathode exhaust gas contains surplus energy.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to improve the efficiency of a fuel cell device by effectively utilizing surplus energy contained in cathode exhaust gas.

[0008]

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, and a fuel cell discharged from the anode. A reformer that burns the anode exhaust gas and the cathode exhaust gas discharged from the cathode, reforms the fuel gas containing water vapor with the heat, and supplies the fuel gas to the anode as anode gas, and supplies the combustion exhaust gas from this reformer to the cathode. A carbon dioxide gas recycling line, a cathode circulation line that receives air supply and circulates cathode exhaust gas to the cathode, a waste heat recovery steam generator that generates steam by heating feed water with the cathode exhaust gas, and mixes with fuel gas. The blower of the gas recycling line and the cathode circulation line is provided with a turbine drive unit. And a blower driving line for supplying the cathode exhaust.

The blower of the carbon dioxide gas recycling line and the cathode circulation line is provided with a turbine drive unit, and the exhaust gas of the cathode exhaust gas is supplied from the blower drive line to the turbine drive unit so that the excess energy of the cathode exhaust gas can be effectively used. Can be.

In the invention of claim 2, a steam line for supplying steam from the exhaust heat recovery steam generator is connected to the blower drive line.

As a method for utilizing the surplus energy of the cathode exhaust gas, a method is used in which feed water is heated with the surplus energy to generate steam, and the steam is used to drive a turbine.

[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 for reforming a fuel gas containing steam into an anode gas containing hydrogen, and a fuel cell 20 for generating electricity from the anode gas and a cathode gas containing oxygen and carbon dioxide. The reformer 22 is a reformed gas (anode gas)
And a catalytic combustor 22b that combusts gas using a catalyst to generate combustion exhaust gas. The anode exhaust gas discharged from the fuel cell 20 is supplied to the catalytic combustor 22b by the anode exhaust gas line 4 and burns together with a part of the cathode exhaust gas. Reformer body 22a
Comprises a reforming chamber for converting city gas containing water vapor into a reformed gas using a catalyst, and a heating chamber for heating the reforming chamber with combustion exhaust gas from the catalytic combustor 22b. Combustion exhaust gas containing carbon dioxide is supplied to the cathode by a carbon dioxide gas recycle line 10, air containing oxygen is supplied by an air line 8, and these are mixed and supplied as cathode gas.

The city gas containing natural gas as a component 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 main body 22a. The anode gas generated from the reforming chamber is supplied to the anode of the fuel cell 20 after the fuel gas is heated by the fuel preheater 24 through the anode gas line 2. The circulation line 3 is connected to the cathode of the fuel cell 20 and supplies a cathode gas containing oxygen and carbon dioxide. Fuel cell 2
Numeral 0 is supplied with the anode gas and the cathode gas to generate power. An anode exhaust gas containing steam and unburned components is discharged by the reaction at the anode, and supplied to the catalytic combustor 22b through the anode exhaust gas line 4. A part of the cathode exhaust gas generated by the reaction at the cathode circulates back to the circulation line 3, another part is supplied to the catalytic combustor 22 b by the cathode exhaust gas line 5, and the remaining part is discharged to the exhaust heat utilization line 6. Supplied.

An anode exhaust gas and a cathode exhaust gas of the fuel cell 20 are supplied to the catalytic combustor 22b. Since the fuel utilization of the fuel cell is about 80%, 2%
About 0% fuel component is contained. Cathode exhaust gas contains oxygen necessary for combustion. Reformer body 22a
The combustion exhaust gas from the heating chamber contains carbon dioxide gas, which is necessary for the battery reaction at the cathode, and is supplied to the cathode by the carbon dioxide gas recycling line 10.

A part of the cathode exhaust gas is used as exhaust heat utilization line 6.
After driving the turbine of the turbine compressor 29, it is supplied to the exhaust heat recovery steam generator 30. A bypass line 6 a is provided across the inlet and outlet of the turbine of the turbine compressor 29, and the flow rate is adjusted by a flow control valve 40. The flow control valve 40 controls the flow control valve 40 so as to be at a predetermined rotation speed based on a measurement value from a tachometer 42 that detects the rotation speed of the turbine compressor 29. In the exhaust heat recovery steam generator 30, feed water is converted into steam by the cathode exhaust gas driving the turbine of the turbine compressor 29, and supplied to the fuel gas line 1 through the steam line 9. Exhaust gas from the exhaust heat recovery steam generator 30 is condensed in the condenser 44, water is separated in the steam separator 46, and the separated water is sent to a pure water device (not shown). The exhaust heat recovery steam generator 30 receives water required for steam generation from a pure device (not shown). The cathode exhaust gas that has exited the steam separator 46 is released to the atmosphere.

The air compressed by the turbine compressor 29 is pressurized by the low-temperature blower 34 of the air line 8 and supplied to the cathode circulation line 3. A bypass line 8a is provided between the inlet and the outlet of the compressor, and a bypass line 8b is provided between the inlet and the outlet of the low-temperature blower 34. Each of the bypass lines 8a and 8b is provided with a check valve 8c. An orifice 8d is provided on the outlet side of the low-temperature blower 34 to adjust the air flow rate. The low-temperature blower 34 is driven by the electric motor M and rotates according to an output command (indicated by OI).

A blower drive line 11 is provided which branches off from the cathode exhaust gas line 6. A high temperature blower 36 is provided in the cathode circulation line 3, and a carbon dioxide gas circulation blower 38 is provided in the carbon dioxide gas recycling line 10. Each blower 36, 38 includes a turbine 47 and an electric motor 48.
Driven by The electric motor 48 is used when the cathode exhaust gas is not sufficiently generated at the start of the operation of the fuel cell, is operated by an output command (OI), and is driven by the turbine 47 after the start. The blower drive line 11 is connected to the high temperature blower 36 and the carbonic acid circulation blower 38, and the exhaust gas after driving the turbine 47 is discharged to the turbine exhaust line 12
Is supplied to the exhaust heat recovery steam generator 30 and used for steam generation. A tachometer 42 is provided on the rotation axis of each of the blowers 36 and 38, and each blower 3
The output of the blowers 36 and 38 is controlled by controlling the rotation speed to a predetermined value by the flow control valves 40 provided for each of the blowers 36 and 38.

A steam line 9a branched from the steam line 9
Is connected to the blower drive line 11 to supply steam to the turbines 47 of the high-temperature blower 36 and the carbon dioxide gas circulating blower 38. As a result, the turbine 47 is driven by both the cathode exhaust gas and the steam.

[0019]

As is apparent from the above description, according to the present invention, when the high-moisture combustion exhaust gas combusted in the reformer is supplied to the cathode to improve the battery efficiency, the supply produces the exhaust gas in the cathode exhaust gas. The battery efficiency can be further improved by using the surplus energy for driving the circulation blowers provided in the cathode circulation line and the carbon dioxide gas recycling line. Further, by changing the drive of the blower from a motor to a turbine, it is possible to abolish the generator and its control device provided for driving the motor in the related art, thereby realizing 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 6a Bypass line 8 Air line 8a, 8b Bypass line 8c Check valve 8d Orifice 9, 9a Steam line 10 Carbon dioxide gas Recycle line 11 Blower drive line 12 Turbine exhaust line 20 Fuel cell 22 Reformer 22a Reformer main body 22b Catalytic combustor 24 Fuel preheater 29 Turbine compressor 30 Exhaust heat recovery steam generator 34 Low temperature blower 36 High temperature blower 38 Carbon dioxide gas Circulation blower 40 Flow control valve 42 Tachometer 44 Condenser 46 Steam separator 47 Turbine 48 Motor

Claims (2)

[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 that reforms fuel gas containing water vapor and supplies it to the anode as anode gas, a carbon dioxide gas recycle line that supplies combustion exhaust gas from the reformer to the cathode, and a supply of air that circulates cathode exhaust gas to the cathode A cathode circulation line, an exhaust heat recovery steam generator that generates steam by heating the feed water by the cathode exhaust gas and mixes the fuel gas, and a blower for the carbon dioxide gas recycling line and the cathode circulation line are provided with a turbine driving device. A blower drive line for supplying cathode exhaust gas to the turbine drive. Characteristic fuel cell power generator. 2. The fuel cell power generator according to claim 1, wherein a steam line for supplying steam from the exhaust heat recovery steam generator is connected to the blower drive line.