JP3139574B2 - Fuel cell generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel cell power generator, and more particularly, to a molten carbonate fuel cell power generator having a line for supplying carbon dioxide from the anode side to the cathode side of a fuel cell.

[0002]

2. Description of the Related Art Molten carbonate fuel cells have features that are not found in conventional power generation devices, such as high efficiency and little impact on the environment, and have attracted attention as power generation systems following hydro, thermal and nuclear power. Are being researched and developed in various countries around the world. In particular, power generation facilities using molten carbonate fuel cells that use natural gas as fuel are distributed and installed in buildings and condominiums in urban areas. Has been spotlighted as a system that can greatly reduce the loss accompanying the above and can exhibit a thermal efficiency of 80% or more.

[0003] Such power generation equipment is provided with a reformer and a fuel cell. The reformer reforms natural gas into an anode gas containing hydrogen, and generates a power from the anode gas and a cathode gas containing oxygen by a fuel cell. The hot water is produced by the residual heat. The main cell reactions in this fuel cell are the anode reaction of H ₂ + CO ₃ ^2- → H ₂ O + CO ₂ + 2e and the cathode reaction of 1/2 O ₂ + CO ₂ + 2e → CO ₃ ^2-. Is a reaction in which hydrogen (H ₂ ) is changed to water (H ₂ O). Thus, the exhaust gas is essentially clean and has very little impact on the environment.

[0004]

In the above reaction, carbon dioxide (CO ₂ ) is consumed on the cathode side and generated on the anode side, so that carbon dioxide is circulated from the anode side to the cathode side in the power generation facility. There is a need. On the other hand, when the water vapor generated by the above reaction is circulated in the battery, the partial pressure of water vapor on the cathode side rises, and the partial pressure of oxygen and carbon dioxide contributing to the reaction decreases, so that the cathode reaction is hindered. Need to be removed. In order to remove the water vapor, a conventional power generator is provided with a condenser and a gas-liquid separator downstream of the reformer, and the exhaust gas of the reformer is condensed by the condenser, and then water droplets are formed by the gas-liquid separator. It was separated and only the gas containing carbon dioxide was circulated to the cathode side.

[0005] However, the above-described conventional power generation equipment has a problem that it takes time to increase the power generation output. That is,
The power generation equipment needs to change the power generation output in response to the power demand. In particular, in the case of the distributed fuel cell power generation, this demand is strong. For example, it is required that the output can be changed from zero to the rated output in 10 minutes. . However, the above-described conventional power generation equipment has a problem in that the amount of carbon dioxide required for power generation cannot be sufficiently supplied by the circulation of the carbon dioxide, and thus the power generation output cannot be increased in a short time.

[0006]

According to Means for Solving the Problems] The present invention, cathode gas containing oxygen and anode gas (2) containing hydrogen
(3) a fuel cell for generating electricity (20), the anode gas after reaction (2) is combusted, a reformer for reforming fuel gas to the anode gas (2) and (10), said reforming Vessel (1
0) Moisture separator for separating moisture in flue gas (7)
(18) and the exhaust gas from which water has been separated
(3) an exhaust gas circulation line, a cathode gas circulation line (9) for returning the reacted cathode gas to the inlet of the fuel cell (20) , and a combustion chamber (C) of the reformer (10).
o) From the middle of the line connecting the side and the air preheater (14),
Exhaust gas bypasser connected to the sword circulation line (9)
Sline (50) and the exhaust gas bypass line (50)
A flow control valve (52) provided at
The valve (52) is connected to the exhaust gas bypass line (50).
Flow rate is the concentration of carbon dioxide corresponding to the power output
The fuel cell power generator is characterized in that the fuel cell power generator is adjusted as described above . According to a preferred embodiment of the present invention, a concentration sensor (54) for measuring the concentration of carbon dioxide in the cathode gas circulation line (9) , and the flow control valve (52 ) according to the measurement value of the concentration sensor (54). ) and controls the control unit (54), further comprising a.

[0007]

According to the present invention, a fuel cell for generating electricity from an anode gas containing hydrogen and a cathode gas containing oxygen, and burning the reacted anode gas to convert the fuel gas into anode gas A reformer for reforming, a moisture separator for separating moisture in the combustion exhaust gas of the reformer, an exhaust gas circulation line for supplying the exhaust gas from which moisture has been separated to the cathode gas, and a cathode gas for the fuel cell after the reaction. A fuel cell power generator having a cathode gas circulation line returning to an inlet, comprising a flue gas bypass line for supplying combustion gas from a reformer to the cathode gas circulation line without separating moisture. An apparatus is provided.

According to a preferred embodiment of the present invention, there is provided a flow control valve for controlling a flow rate of an exhaust gas bypass line, a concentration sensor for measuring a carbon dioxide concentration in a cathode gas circulation line, and a function of a measured value of the concentration sensor. A control device for controlling the flow control valve.

[0009]

When the power generation output of the fuel cell rises, the anode reaction of H ₂ + CO ₃ ^2- → H ₂ O + CO ₂ + 2e and the reaction of 1/2 O ₂ + CO ₂ + 2e → CO ₃ ^2- The cathode reaction becomes active. That is, as the power generation output increases, the consumption of hydrogen (H ₂ ) and oxygen (O ₂ ) increases, but the generation of carbon dioxide (CO ₂ ) also increases. Therefore, if the generated carbon dioxide is returned to the cathode side in a short time, the shortage of the carbon dioxide does not occur, and the power generation output can be increased in a short time. The present invention is based on such findings.

That is, a circulating means by an exhaust gas circulating line of a conventional power generation apparatus, that is, an exhaust gas of a reformer is condensed by a condenser, water droplets are separated by a gas-liquid separator, and then only a gas containing carbon dioxide is cathode. It was found that the supply of carbon dioxide was delayed in the circulating means circulating to the side. Further, it was found that even if exhaust gas containing water vapor was circulated in the battery, the power generation output could be increased without inhibiting the cathode reaction for a short time.

Therefore, according to the structure of the present invention, the reformer
Exhaust gas bypass line for directly supplying the combustion exhaust gas of (10) to the cathode gas circulation line (9) without separating water
Since (50) is provided, only the gas containing carbon dioxide generated in the fuel cell (20) can be returned to the cathode side in a short time. In particular, the cathode gas circulation line (9)
By measuring the carbon dioxide concentration and controlling the flow control valve (52) according to the measured value, carbon dioxide having a concentration corresponding to the rate of increase in output can be supplied to the cathode gas.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram showing a power generation facility according to the present invention. In this figure, a power generation facility includes a reformer 10 for reforming a fuel gas into an anode gas containing hydrogen,
A fuel cell 20 for generating electricity from the anode gas and a cathode gas containing oxygen, a catalytic combustor 30 for burning the reacted anode gas, that is, an anode exhaust gas, and a reformer 1
A heat exchanger, that is, a fuel preheater 40 for exchanging heat between a high-temperature anode gas that has exited 0 and a low-temperature fuel gas supplied to the reformer 10 is provided. Further, the power generation equipment includes a desulfurizer 12 for removing sulfur contained in the fuel gas, an air preheater 14 for preheating air, a condenser 16 for condensing moisture in exhaust gas, and a separator for separating condensed moisture. Gas-liquid separator 18
And

A fuel gas such as a natural gas containing sulfur is desulfurized by a desulfurizer 12, supplied to a fuel heater 40 through a line 1, heated by the fuel preheater 40 and sent to a reformer 10. Supplied.

The reformer 10 reforms the fuel gas by heat transfer from the combustion chamber Co in which the high-temperature combustion gas supplied from the catalytic combustor 30 via the combustion gas line 6 completely burns. And a reforming chamber Re. The reformer 10 is preferably a plate-type reformer in which the combustion chamber Co and the reforming chamber Re have a planar shape, and a plurality of the chambers are stacked. The reforming chamber Re is filled with a reforming catalyst, and the fuel gas is reformed into a high-temperature anode gas containing hydrogen by the high-temperature combustion gas generated in the combustion chamber Co. The combustion exhaust gas whose temperature has been lowered by the heat release is supplied to the air preheater 14 through the combustion exhaust gas line 7 to heat the air, and then the moisture is separated by the condenser 16 and the gas-liquid separator 18. On the other hand, the high-temperature anode gas that has exited the reformer 10 is supplied to the fuel preheater 40 via the anode gas line 2 and is cooled by the fuel preheater 40.
It is supplied to the fuel cell 20.

The fuel cell 20 has an anode side A through which anode gas passes and a cathode side C through which cathode gas passes.
The hydrogen and carbon monoxide in the anode gas and the oxygen and carbon dioxide in the cathode gas generate electricity by a chemical reaction. The fuel cell 20 is preferably a molten carbonate fuel cell.

The anode exhaust gas and the cathode exhaust gas (the cathode gas after the reaction) exiting the fuel cell 20 are supplied to the catalytic combustor 30 via the anode exhaust gas line 4 and the cathode exhaust gas line 5. The catalyst combustor 30 is filled with a honeycomb-shaped combustion catalyst containing nickel as a main component, so that unburned components contained in the anode exhaust gas are burned by oxygen contained in the cathode exhaust gas.
The high-temperature combustion gas generated in the catalytic combustor 30 is supplied to the combustion chamber Co of the reformer 10 via the line 6.

The reformer 1 is not provided with the catalytic combustor 30.
In some cases, the unburned portion contained in the anode exhaust gas is burned by the oxygen contained in the cathode exhaust gas in the combustion chamber Co of zero.

The cathode gas line 3 of the fuel cell 20 is connected to an air line 8 and an air preheater 14 from an air source (not shown).
The air is supplied via. The flue gas from which water has been separated by the gas-liquid separator 18 is supplied to the air line 8 to supply carbon dioxide necessary for the reaction of the battery.

Further, a part of the cathode exhaust gas passing through the cathode side C of the fuel cell is circulated to the cathode line 3 via the cathode circulation line 9. The cathode circulation line 9 is usually provided with a heat exchanger (not shown) and a blower 22 so that the temperature and flow rate of the circulating cathode gas can be controlled.

The power generation apparatus further includes the flue gas 7 from the reformer 10 and the cathode gas circulation line 9 without separating moisture.
An exhaust gas bypass line 50 for supplying the exhaust gas to the exhaust gas. The exhaust gas bypass line 50 has a flow control valve 52 for adjusting the flow rate of the exhaust gas bypass line, and a concentration sensor 54 for measuring the carbon dioxide concentration in the cathode gas circulation line.
And the flow control valve 52 according to the measurement value of the concentration sensor 54.
And a control device 56 for controlling the

The exhaust gas bypass line 50 is connected to the reformer 10
From the middle of the line connecting the air preheater 14 to the upstream of the blower 22 of the cathode circulation line 9 (on the side of the cathode exhaust gas line 5), a flow control valve 52 is provided in the middle. The flow control valve 52 is preferably adjusted so as to have a carbon dioxide concentration corresponding to the power generation output. Thereby, the concentration of carbon dioxide in the cathode gas is increased in a short time, and the flow control valve 52 is gradually closed as the concentration of carbon dioxide in the gas circulated through the condenser 16 and the gas-liquid separator 18 increases. It is possible to prevent the gas containing water from being circulated for a long time.

According to the configuration of the present invention described above, by providing the exhaust gas bypass line for directly supplying the combustion exhaust gas of the reformer to the cathode gas circulation line without separating moisture, the carbon dioxide generated in the fuel cell can be reduced. It can be returned to the cathode side in a short time. Further, if the concentration of carbon dioxide in the cathode gas circulation line is measured and the flow rate control valve is controlled according to the measured value, carbon dioxide having a concentration corresponding to the rate of increase in output can be supplied to the cathode gas.

[0023]

Therefore, according to the present invention, the power generation output can be increased in a short time with a simple structure and without providing a carbon dioxide storage tank or the like.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing a power generator according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fuel gas line 2 Anode gas line 3 Cathode gas line 4 Anode exhaust gas line 5 Cathode exhaust gas line 6 Combustion gas line 7 Combustion exhaust gas line 8 Cathode gas line 9 Cathode gas circulation line 10 Reformer 12 Desulfurizer 14 Air preheater 16 Condensation Device 18 gas-liquid separator 20 fuel cell 30 catalytic combustor 40 fuel preheater 50 exhaust gas bypass line 52 flow control valve 54 concentration sensor 56 controller

Claims (2)

(57) [Claims] 1. A fuel cell for generating electricity from an anode gas (2) containing hydrogen and a cathode gas (3) containing oxygen.
And (20), is burned anode gas (2) after the reaction, reformer for reforming fuel gas to the anode gas (2) and (10), said reformer (10) of the flue gas (7) A water separator (18) for separating water therein, an exhaust gas circulation line for supplying exhaust gas from which water has been separated to the cathode gas (3) , and a cathode gas for returning the reacted cathode gas to the inlet of the fuel cell (20) A circulation line (9) , a combustion chamber (Co) side of the reformer (10) and an air preheater.
Cathode circulation line from the middle of the line connecting (14)
Exhaust gas bypass line communicating with (9) (50)
And a flow control provided in the exhaust gas bypass line (50).
A valve (52), wherein the flow control valve (52) is connected to the exhaust gas bypass line.
Carbon dioxide corresponding to the power generation output at the flow rate in (50)
A fuel cell power generator, wherein the fuel cell power is adjusted so as to have a concentration of 0.1 %. 2. A concentration sensor (54) for measuring the concentration of carbon dioxide in the cathode gas circulation line (9) , and a control for controlling the flow control valve (52) in accordance with a measurement value of the concentration sensor (54). The fuel cell power generator according to claim 1, further comprising a device (54) .