JP3882337B2 - Fuel cell power generation facility with differential pressure self-control function - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power generation facility using a molten carbonate fuel cell, and more particularly to a fuel cell power generation facility having a differential pressure self-control function.
[0002]
[Prior art]
The molten carbonate fuel cell uses a molten carbonate that is in a molten state at a high temperature as an electrolyte, and has a feature that it can operate at a high temperature of about 650 ° C. and achieve high power generation efficiency.
FIG. 2 is an overall configuration diagram of a conventional power generation facility (hereinafter simply referred to as a fuel cell power generation facility) using such a molten carbonate fuel cell. In this figure, 1 is a desulfurizer, 2a and 2b are heat exchangers, 3 is a reformer (reformer), 4 is a fuel cell, 5 is a combustor, 6 is an exhaust heat recovery boiler, 7a is a condenser, and 7b is A knockout drum (KO drum), 8a and 8b are blowers, and 9 is a turbine compressor. The natural gas Ng as fuel is desulfurized by the desulfurizer 1, preheated by the heat exchanger 2a, and enters the reforming chamber Re of the reformer 3, where it is reformed to the anode gas Ga containing hydrogen. Then, it is cooled by the heat exchanger 2 a and supplied to the anode side A of the fuel cell 4. In the fuel cell 4, power is generated by the anode gas Ga and the cathode gas Gc, and the anode exhaust gas Ea and the cathode exhaust gas Ec after power generation are supplied to the combustor 5, where unburned components are catalytically combusted to generate a high temperature gas Eg. Then, the reforming chamber Re is heated in the heating chamber H of the reformer 3, and the combustion exhaust gas discharged from the reformer 3 preheats the air in the air preheater 2b, and further the gas temperature to room temperature in the condenser 7a. The water W is removed by the knockout drum 7b. Further, the exhaust gas is pressurized by the blower 8a, mixed with the air A pressurized by the turbine compressor 9, preheated by the heat exchanger 2b, merged with the high temperature recycle system, and then supplied to the fuel cell 4 as the cathode gas Gc. Is done. Further, the water vapor S generated in the exhaust heat recovery boiler 6 is mixed with the natural gas Ng and used for the reforming reaction, and the water W generated in the condenser 7 a is used as feed water for the boiler 6. A recycle blower 8b circulates the cathode gas to control the temperature of the fuel cell.
[0003]
The above-described fuel cell power generation facility is normally operated under pressure in order to increase power generation efficiency. Therefore, the reformer 3 and the fuel cell 4 are each built in the pressure vessel. However, since the installation area becomes large and the heat dissipation increases when each pressure vessel is individually incorporated in the pressure vessel, it has been proposed to store these main devices in one pressure vessel (for example, Japanese Patent Application No. 2-122972). issue).
On the other hand, when the differential pressure between the anode side A and the cathode side B (interelectrode differential pressure) in the fuel cell 4 increases, the anode gas Ga and the cathode gas Gc cross leak (internal leak), and the fuel is wasted. Battery performance is greatly reduced. For this reason, it is necessary to always control the inter-electrode differential pressure to a low value, for example, within about 400 mmAq. In the conventional fuel cell power generation facility, the anode exhaust gas Ea and the cathode exhaust gas Ec are led to the same combustor 5, and the combustor The pressure difference between the electrodes is made to be essentially a low value by communicating within 5.
[0004]
Further, the pressure in the fuel cell 4 (the anode side A and the cathode side B) and the pressure in the pressure vessel surrounding the fuel cell 4 are also set to a value as low as the inter-electrode differential pressure in order to prevent gas leakage (external leakage). There is always a need to control. As shown schematically in FIG. 3, this control is conventionally performed by detecting the pressure difference between the battery and the container with a differential pressure detector Dp, and the flow rate of the gas flow to be supplied and the gas flow to be discharged into the container. It was performed by adjusting with 10a and 10b.
[0005]
[Problems to be solved by the invention]
In such a conventional fuel cell power generation facility, nitrogen gas or exhaust gas is supplied into the pressure vessel. However, there is a problem that (1) the production of nitrogen gas and piping for exhaust gas circulation are costly, and (2) an expensive control valve is required for differential pressure control.
[0006]
(3) The differential pressure must be precisely controlled by the differential pressure detector Dp for controlling the differential pressure between the vessel and the cathode and the flow rate adjusting valves 10a and 10b. There is a problem that the pressure difference between the inside and the battery increases. That is, in the differential pressure control by the conventional control valves 10a and 10b shown in FIG. 3, the gas in the container escapes to the cathode line through the pipe B at the time of emergency shutdown of the plant, but the cathode line pressure is instantaneously normal pressure by the emergency opening. On the other hand, since the internal pressure of the container has a large capacity, the pressure in the container is gradually released by being restricted by the flow rate of the pipe B. Therefore, at the time of emergency plant shutoff, the vessel pressure temporarily exceeds the allowable pressure with respect to the cathode pressure, and the seal portion in the battery may be damaged. In addition, this differential pressure control (differential pressure in the container and in the battery) uses a control valve and a control device, so it is susceptible to power failures and voltage fluctuations, and has a problem of poor reliability during long-term operation. there were.
[0007]
The present invention has been made to solve such problems. That is, the object of the present invention is to eliminate the supply of nitrogen gas or exhaust gas to the containment vessel for storing the reformer and the fuel cell, thereby eliminating the need for nitrogen gas as a utility and during normal plant operation. Regardless of the time of emergency shutoff, the differential pressure in the container and the battery can be controlled to a value within the allowable range, and the differential pressure can be controlled reliably without being affected by power failure or voltage fluctuation. It is to provide a fuel cell power generation facility having a self-control function.
[0008]
[Means for Solving the Problems]
According to the present invention, the fuel cell, the reformer, and the combustor for the reformer are stored in the same containment vessel, and a part of the cathode exhaust gas discharged from the fuel cell is introduced into the containment vessel, There is provided a fuel cell power generation facility having a differential pressure self-control function, characterized in that cathode exhaust gas is introduced into an inlet of a combustor through a containment vessel.
[0009]
According to the configuration of the present invention, since the cathode exhaust gas introduced into the inlet of the combustor is once introduced into the containment vessel and serves as the gas in the vessel, the supply of nitrogen gas to the containment vessel can be eliminated, This eliminates the need for nitrogen gas as a utility.
In addition, according to the above configuration, the cathode exhaust gas outlet of the fuel cell communicates with the inside of the containment vessel so that a part of the cathode exhaust gas is introduced into the containment vessel. Thus, unlike the prior art, the container / cathode side differential pressure control by the control valve is not required. Therefore, regardless of whether the plant is in normal operation or emergency shutdown, the differential pressure in the container and the battery can be suppressed to a small value within the allowable value, and it is highly reliable without being affected by power failure or voltage fluctuation. Differential pressure control is possible.
[0010]
According to a preferred embodiment of the present invention, a portion of the hot exhaust gas leaving the reformer is recirculated to the cathode inlet of the fuel cell without heat exchange with other fluids.
With this configuration, the heat quantity of the reformer combustion exhaust gas can be brought into the cathode as it is, so that the capacity of the high temperature recycle system can be reduced. In addition, the amount of heat released from the battery is not lost because the air in the containment vessel is heated and returned to the fuel cell as cathode gas again.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.
FIG. 1 is an overall configuration diagram of a fuel cell power generation facility according to the present invention. In this figure, in the fuel cell power generation facility of the present invention, the heat exchanger 2a, the reformer 3, the fuel cell 4, and the reformer combustor 5 (preferably the catalytic combustor) are in the same containment vessel 12. Stored. Further, the anode outlet pipe 13 of the fuel cell 4 is branched into two, one is supplied to the combustor 5 through the orifice 13 a, and the other is supplied to the combustor 9 a of the turbine compressor 9. Further, the cathode outlet pipe 11 of the fuel cell 4 is branched into three, one is supplied to the reformer combustor 5 via the check valve 11a, and one is supplied via the flow rate control valve 11b. The other one supplied to the cathode inlet side is supplied to the combustor 9 a of the turbine compressor 9.
[0012]
Furthermore, according to the present invention, the cathode outlet pipe 11 located in the containment vessel 12 has the open hole 17a, and also has the introduction hole 17b between the combustor 5 and the check valve 11a. The open hole 17a and the introduction hole 17b are set so that the cathode gas flows with a sufficiently small pressure loss. With this configuration, a part of the cathode exhaust gas exiting the fuel cell 4 is introduced into the containment vessel 12 through the open hole 17a, and this cathode exhaust gas is further introduced from the containment vessel 12 through the introduction hole 17b into the inlet of the combustor 5. Can be introduced.
The storage container 12 may be a pressure container or a simple sealed container for normal pressure.
[0013]
That is, in the fuel cell power generation facility of the present invention, the cathode exhaust gas introduced into the inlet of the combustor 5 is once introduced into the containment vessel 12 and serves as the gas in the vessel. Therefore, the supply of nitrogen gas to the storage container 12 can be eliminated, thereby eliminating the need for nitrogen gas as a utility. Further, by setting the amount of cathode exhaust gas introduced into the container to a small amount that does not raise the temperature in the container, stagnation of combustible gas (for example, even when anode gas leaks) can be prevented by the gas flow in the container. Further, even if the concentration of the combustible gas increases, it is recirculated into the system through the catalyst combustor, so that it is possible to prevent the combustible gas from entering the system.
[0014]
Further, in the fuel cell power generation facility of the present invention, the inside of the container and the cathode outlet communicate with each other via the open hole 17a and the introduction hole 17b, so that the operating pressure has a relation of anode≈cathode> container, and this relation is specially controlled. Therefore, the cathode gas is not mixed into the anode side and anodic oxidation can be prevented. Further, from this relationship, the container pressure on the cathode side in the battery is almost the same as that in the battery, and unlike the conventional technique, the differential pressure control on the container / cathode side by the control valve is not required. In addition, even in the event of an emergency plant shutdown, the pressure difference between the container and the battery can be controlled to a small value within the allowable value, and highly reliable differential pressure control that is not affected by power outages or voltage fluctuations is possible. It becomes.
[0015]
That is, in the differential pressure control using the conventional control valve, as described above, since the gas in the container passes through the pipe B at the time of emergency shutdown of the plant, the container pressure is not instantaneously opened to the cathode line, and the container pressure is higher than the cathode pressure. However, in the present invention, since the gas in the container easily flows into the reformer heating chamber or the cathode, the internal / external differential pressure of the battery can be controlled to be small.
[0016]
Further, as shown in FIG. 1, in the fuel cell power generation facility of the present invention, a part of the high-temperature exhaust gas exiting the reformer 3 is not exchanged with other fluids via the exhaust gas circulation line 16 and the circulation blower 16a. Then, it is recirculated to the cathode inlet of the fuel cell 4.
With this configuration, the heat quantity of the reformer combustion exhaust gas can be brought into the cathode as it is, so that the capacity of the high temperature recycle system can be reduced. Further, the amount of heat released from the battery is not lost because the air in the storage container 12 is heated and returned to the fuel cell as cathode gas again.
[0017]
In addition, this invention is not limited to the Example mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.
[0018]
【The invention's effect】
As described above, the fuel cell power generation facility of the present invention can eliminate supply of nitrogen gas or exhaust gas to the containment vessel that stores the reformer and the fuel cell, thereby eliminating the need for nitrogen gas as a utility, In addition, regardless of whether the plant is in normal operation or when the plant is in an emergency shutdown, the pressure difference between the container and the battery can be suppressed to a small value within the allowable range without using a control device such as a pressure control valve. It has excellent effects such as highly reliable differential pressure control that is not affected by voltage fluctuations.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a fuel cell power generation facility according to the present invention.
FIG. 2 is an overall configuration diagram of a conventional fuel cell power generation facility.
FIG. 3 is a partial configuration diagram around the fuel cell of FIG. 2;
[Explanation of symbols]
1 Desulfurizer 2a, 2b Heat exchanger 3 Reformer (reformer)
4 Fuel cell 5 Combustor 6 Waste heat recovery boiler 7a Condenser 7b Knockout drum (KO drum)
8a, 8b Blower 9 Turbine compressor 9a Combustors 10a, 10b Flow control valve 11 Cathode outlet piping 11a Check valve 11b Flow control valve 12 Storage vessel 13 Anode outlet piping 13a Orifice 14 Air line 16 Exhaust gas circulation line 16a Circulation blower 17a Open hole 17b Introduction hole

Claims (2)

The fuel cell, the reformer, and the combustor for the reformer are stored in the same containment vessel, a part of the cathode exhaust gas discharged from the fuel cell is introduced into the containment vessel, and the cathode exhaust gas is stored in the containment vessel. A fuel cell power generation facility having a differential pressure self-control function, wherein the fuel cell power generation facility is introduced into an inlet of a combustor. 2. The fuel cell power generation facility according to claim 1, wherein a part of the high-temperature exhaust gas exiting the reformer is recirculated to the cathode inlet without heat exchange with other fluids.

Images