JPH044570A - Method for operating fuel cell and its power generating system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention enables a pot standby state in which power transmission to the outside is substantially stopped while the battery body is maintained at an operating temperature. The present invention relates to a method of operating a fuel cell and a power generation system thereof.

[Conventional technology]

In a fuel cell power generation system, operation may be stopped for a relatively short period of time, such as at night when there is a surplus of electricity. To shorten startup time, power transmission to the outside is virtually stopped while the battery is maintained at operating temperature, in other words, the temperature of the electrolyte inside the battery is maintained above its melting point. This requires a so-called hot standby state.

-a, when temporarily stopping the operation of the battery, for example,
As noted in Publication No. 1472, it is known to supply an inert gas such as nitrogen gas to the battery body to purge the reactive gas remaining in the battery body or piping system, but this is especially true for hot standby. Speaking of time, I can't find anything that mentions the type of gas to be supplied into the battery body.

[Problem to be solved by the invention]

During hot standby, if an inert gas is supplied into the battery body to purge the reaction gas as described in the above-mentioned publication, the battery reaction may be reduced due to a change in the type of gas supplied into the battery body. can no longer be maintained in optimal condition,
This adversely affects battery characteristics, leading to a decline in battery performance and shortened battery life.Furthermore, when restarting the battery, it is necessary to switch the gas inside the battery from an inert gas to a reactive gas. Therefore, it takes a relatively long time for the battery output to become stable, which causes a problem in that efficient operation of the battery is hindered to some extent.

In particular, fuel cells are used as a power source for peak loads;
If the startup and shutdown are repeated frequently, the above-mentioned problem will become more noticeable.

In view of this, the present invention is capable of maintaining the battery reaction section in an optimal state during hot standby, suppressing deterioration of battery performance and shortening of battery life as much as possible, and
It is an object of the present invention to provide a method of operating a fuel cell and a power generation system thereof that can provide excellent starting characteristics and achieve efficient operation.

[Means to solve the problem]

In order to achieve the above object, the inventors of the present application have conducted extensive research and have obtained the following findings.

In other words, the cell reaction in a fuel cell is a solid phase (electrode)
Since the reaction takes place at the three-phase interface of the liquid phase (electrolyte) and gas phase (reactant gas), this reaction field must be maintained in an appropriate state, and for this purpose, it is necessary to appropriately wet the electrode part with the electrolyte. There is.

The wettability of an electrode varies depending on the type of gas supplied to it, and if the type of gas changes by supplying an inert gas such as nitrogen during hot standby, the electrode may become too wet or the electrolyte in the electrode may be pushed out. The reaction field deviates from the appropriate state due to electrolyte movement phenomenon.

Therefore, even if the reactive gas is supplied again when restarting the battery, it will take some time for the electrolyte to return to its original proper state, prolonging the startup time.
As the electrolyte moves, electrolyte leakage and corrosion of battery components such as separators occur, causing the electrolyte to be consumed, leading to a decline in battery performance and deterioration of the main parts of the battery, shortening its lifespan. be.

The fuel cell operating method according to the present invention was developed based on the above-mentioned investigation results and considerations based thereon.
Briefly speaking, the basic configuration is such that even during hot standby, a small amount of reactive gas is supplied into the battery main body to maintain the fuel cell in a power generation state.

In this case, the reactive gas supplied into the battery body during hot standby is mainly fuel gas such as natural gas or methane gas, which is the same type as that normally used during power generation, or hydrogen obtained by reforming it. and an oxidant gas containing oxygen and carbon dioxide.

In addition, as mentioned above, the power obtained from the battery by supplying reactive gas during hot standby can be used to raise the temperature of the heater for heating the battery body and the supplied reactive gas, which are required to maintain the hot standby state. It can be used as a power source for battery heat-insulating means such as heating equipment for heating.

Furthermore, in a fuel cell in which a fuel reforming catalyst is arranged inside the cell body, during normal power generation, a reaction gas reformed by a rib omer for fuel reforming is supplied into the cell body,
During hot standby, unmodified reaction gas may be supplied into the battery main body.

Furthermore, during hot standby, the amount of reactive gas supplied into the battery main body is sufficient to be less than 10% of that during normal power generation, and during hot standby, the reactive gas discharged from the battery main body is The battery may be returned and recycled.Furthermore, during hot standby, the piping system for supplying and discharging reactive gas to and from the battery body may be closed to seal the reactive gas within the battery body.

In addition, if the reactant gas is recycled during hot standby, when the concentration of the reactant in the reactant gas falls below the set value during the recycle loop and it becomes difficult to maintain the power generation state, the battery It is preferable to supply new reactive gas into the main body, in which the concentration of the reactant exceeds the above-mentioned set value.

On the other hand, in the fuel cell power generation system according to the present invention, an auxiliary rib ohmer having a capacity of 30% or less of the capacity required during normal power generation is installed, and during hot standby,
The modified reaction gas is supplied into the battery body by the auxiliary rib omers.

Further, in another fuel cell power generation system according to the present invention, a plurality of rib ohmers are installed, and during hot standby, only a part of the plurality of rib ohmers are used to reform the reaction gas, and the reformed gas is reformed. The reactant gas thus produced is supplied into the battery main body.

[Effect]

According to the method of operating a fuel cell according to the present invention having the above-described configuration, the reaction gas is supplied into the cell body without purging the reaction gas with an inert gas during hot standby. Electrolyte movement phenomena caused by changes in the type of gas within the battery body are prevented, and the reaction field of the battery is always maintained in an appropriate state.

Therefore, it is possible to suppress a decrease in battery performance, extend the life of the battery, provide excellent starting characteristics, and achieve efficient operation.

In addition, the power obtained from the battery during hot standby is
By using it as a power source for battery heat retention means, it can be used effectively.Furthermore, the amount of reactive gas required during hot standby is much smaller than that required during normal power generation, and the reactive gas can be recycled or In this case, wasteful consumption of the reaction gas can be avoided and resources can be further saved.

On the other hand, in the fuel cell power generation system according to the present invention,
An auxiliary rib ohmer having a capacity of 30% or less of the capacity required during normal power generation is installed, and during hot standby, the reaction gas modified by the auxiliary rib ohmer is supplied into the battery body. Even in a fuel cell power generation system equipped with a normal rib ohmer, which is difficult to operate at less than 30% of the capacity required during normal power generation, it is possible to operate effectively as described above during hot standby, and The same applies to the case where, instead of installing an auxiliary rib aomer, a plurality of rib aomers are installed and only some of them are used during hot standby.

Incidentally, in a fuel cell employing a so-called internal reforming method in which a fuel reforming catalyst is disposed within the cell body, there is no need to use an auxiliary rib omer or the like. In addition, it is not necessary to operate the battery under load during hot standby;
) can also provide similar effects.

In order to compare the operating method according to the present invention having the above-described configuration with the conventional operating method in which the reaction gas inside the cell body is purged with an inert gas during hot standby, a small fuel cell was prepared and the same Under the following conditions, intermittent operation in the daytime generation-nighttime hot standby state was performed to determine the cell voltage (V).
When measured, the results shown in FIG. 5 were obtained. Note that the fuel cell was in an open state.

As is clear from FIG. 5, according to the operating method according to the present invention, the deterioration of battery performance is suppressed compared to the conventional operating method, and the cell voltage does not decrease much even after a long period of time. It is understood that this does not occur. Furthermore, it was also confirmed that the time required to restart after hot standby was shorter than when using the conventional operating method.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Example 1: FIG. 1 schematically shows an example of the main part Φ of a molten carbonate fuel cell in which an example of the fuel cell operating method according to the present invention is implemented.

In the figure, the fuel cell includes a battery main body 3 in which constituent members such as an anode 1 (fuel electrode), a cathode 2 (oxidation side electrode), and a matrix and separator for impregnating and retaining an electrolyte (not shown) are arranged in a known manner. It also has a heater 4 for keeping the battery body 3 warm, a rib ohmer (not shown) that is used during normal power generation to reform fuel gas such as natural gas or methane gas into hydrogen, and a heater 4 that is required during normal power generation. The auxiliary rib omer 5 is provided with a capacity that is 30% or less of the capacity of the auxiliary rib omers.

With this configuration, when the fuel cell is operated to perform normal power generation, the fuel gas is reformed by a rib omer for normal power generation, and the resulting gas containing hydrogen as a main component is fed into the cell body 3. A gas containing oxygen and carbon dioxide is supplied to the cathode 2 side while being supplied to the anode 1 side. As a result, the fuel cell enters a power generation state, and the power obtained by this power generation is transmitted to the outside.

On the other hand, during hot standby, the auxiliary rib omers 5 supply hydrogen-based gas obtained by reforming the fuel gas at a flow rate of 10% or less during normal power generation to the anode 1 side of the battery body 3. A gas containing oxygen and carbon dioxide at a flow rate corresponding to the hydrogen is supplied to the cathode 2 side of the battery body 3. As a result, the battery enters a weak power generation state, and the power obtained thereby is used as a power source for the heater 4.

As mentioned above, during hot standby, the reaction gas (in this example,
By supplying a gas containing hydrogen as a main component and a gas containing oxygen and carbon dioxide into the battery body 3, an electrolyte movement phenomenon caused by a change in the type of gas within the battery body 3 is prevented. , the reaction field of the battery is always maintained in an appropriate state, which makes it possible to suppress deterioration of battery performance and extend the life of the battery, and
Excellent starting characteristics will be provided and efficient operation will be achieved.

In this embodiment, the flow rate of the fuel gas to be reformed by the auxiliary rib omer 5 during hot standby is the same as that during normal power generation due to the balance with the capacity of the heater 4, in other words, the amount of heat required by the battery body 3. The optimum range was 4% to 8%.

Further, the heater 4 may be powered by an external power source instead of the fuel cell, and in such a case, the flow rate of the reaction gas can be significantly reduced.

Example 2: FIG. 2 schematically shows an example of the main parts of a molten carbonate fuel cell in which another example of the fuel cell operating method according to the present invention is implemented.

The fuel cell of this example has a fuel reforming catalyst 6 disposed within the anode side gas header of the cell main body 3, and is a fuel cell employing a so-called indirect internal reforming method.

Under such a configuration, when the fuel cell is operated to perform normal power generation, the fuel gas is reformed by a rib omer for normal power generation (not shown), and the obtained hydrogen is the main component. Gas is supplied to the anode 1 side of the battery body 3, and gas containing oxygen and carbon dioxide is supplied to the cathode 2 side, and the power obtained thereby is transmitted to the outside.

On the other hand, during hot standby, unreformed fuel gas (reactive gas) that does not pass through the rib omers is directly supplied to the anode side gas header of the battery body 3, and oxygen and carbon dioxide are supplied at a flow rate corresponding to the fuel gas. The gas containing the battery is supplied to the cathode 2 side of the battery body 3. The unreformed fuel gas supplied to the anode side gas header is reformed by the fuel reforming catalyst disposed there into a gas containing hydrogen as a main component, and then guided to the anode 1 side of the battery body 3, where it is guided to the anode 1 side of the battery body 3. Power generation status is maintained. The obtained battery output is then used as a power source for the heater 4.

Therefore, in this example, substantially the same effects as in Example 1 described above can be obtained, except that the auxiliary rib omers are not required.

In addition, it is also possible to install the fuel reforming catalyst at a location located near the anode inside the battery main body 3 to adopt a direct internal reforming method in which the reforming reaction and the cell reaction are performed simultaneously. Although the reforming efficiency is higher when such a method is adopted, since the fuel gas comes into contact with the electrolyte, the fuel reforming catalyst tends to deteriorate, resulting in a shortened battery life. Therefore, as in this example, when the fuel reforming catalyst is used only for reforming fuel during hot standby, the battery output is not required so much, so an indirect internal reforming method is adopted to reform the catalyst. It is considered more advantageous to carry out the reaction and the battery reaction separately to extend the life of the battery.

Embodiment 3: FIG. 3 schematically shows an example of the main parts of a molten carbonate fuel cell in which another example of the fuel cell operating method according to the present invention is implemented.

The fuel cell in this example is similar to that shown in FIG.
It has a battery body 3 in which constituent members such as an anode 1, a cathode 2, a matrix and a separator for impregnating and retaining an electrolyte (not shown) are arranged in a known manner, and further includes a heater 4 for keeping the battery body 3 warm; Additionally, a reformer (not shown) used for normal power generation, etc., which reform fuel gas such as natural gas or methane gas into hydrogen, is provided.

In addition, a switching valve 9 is installed in the piping system for supplying and discharging the reactive gas, and a valve 9 is installed in the piping system for supplying and discharging the reactive gas. A blower 7 and a concentration sensor 8 for detecting the concentration of a reactant in the reaction gas are arranged in the piping.

Under such a configuration, power generation is normally performed in the same manner as in the above example, but during hot standby, the blower 7
The reaction gas discharged from the battery body 3 is returned to the battery body 3 and recycled, and the concentration of the reactant in the reaction gas monitored by the concentration sensor 8 becomes below the set value, and the power generation state is reached. When it becomes difficult to maintain the concentration of the reactant, each valve 9 is opened to supply a new reactant gas with a reactant concentration exceeding the set value into the battery main body 3.

Therefore, in this example, when replacing the reaction gas during hot standby, it is sufficient to operate the rib ohmer for normal power generation, which eliminates the need for a special auxiliary rib ohmer for low flow rates, and replaces the reaction gas. There is no wasteful consumption, and substantially the same effects as in the first embodiment described above can be obtained.

Note that if a buffer tank is provided in the middle of the recycle loop to increase the volume of the recycle loop piping system, it is possible to lengthen the exchange period of the reactant gas, thereby reducing operating costs.

Embodiment 4: FIG. 4 schematically shows an example of the main parts of a molten carbonate fuel cell in which another example of the fuel cell operating method according to the present invention is implemented.

The fuel cell of this example is equipped with a cell main body 3 and a rib omer having a configuration similar to that shown in FIGS. A valve 9 is provided to allow reaction gas to be enclosed within the battery body 3.

In this configuration, normal power generation is performed in the same manner as in the above-described example, but during hot standby, the valve 9 is closed to fill the battery body 3 with reactive gas.

This example operating method has a relatively short hot standby time during which the battery temperature does not drop below the melting point of the electrolyte.
This is particularly suitable when a heater for heat retention or the like is not required. That is, in such a case, since the battery can be kept in an open circuit state, almost no reactive gas is consumed, and therefore, the power generation state can be sufficiently maintained with only the amount of reactive gas sealed within the battery body 3. This eliminates the need for an auxiliary rib ohmer or heater.

Note that if the heater 4 is provided as in the above example and is operated by an external power source, a drop in temperature of the battery body 3 can be prevented and the hot standby time can be extended.

〔Effect of the invention〕

As is clear from the above explanation, according to the fuel cell operating method according to the present invention, the cell reaction section can be maintained in an optimal state during hot standby, thereby minimizing deterioration of cell performance. This makes it possible to extend the life of the battery, provide excellent starting characteristics, and achieve efficient operation.

In addition, the electric power obtained during hot standby can be used effectively as a power source for battery insulation means, and the amount of reactive gas required during hot standby is extremely small compared to when generating electricity. Furthermore, it is possible to avoid wasteful consumption of the reaction gas by recycling the reaction gas or by sealing it within the battery body.

On the other hand, in the fuel cell power generation system according to the present invention, an auxiliary rib ohmer having a capacity of 30% or less of the capacity required during normal power generation is installed, and during hot standby,
A fuel cell with a normal rib ohmer that is difficult to operate at less than 30% of the capacity required for normal power generation because the auxiliary rib ohmer supplies reformed reaction gas into the cell body. In the power generation system as well, effective operation as described above is possible during hot standby, and instead of installing an auxiliary rib ohmer, multiple rib ohmers can be installed and only some of them can be operated during hot standby. A similar effect can be obtained when using .

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram schematically showing an example of the main parts of a molten carbonate fuel cell in which an example of the method of operating a fuel cell according to the present invention is implemented, and FIG. FIG. 3 is a schematic configuration diagram schematically showing an example of the main parts of a molten carbonate fuel cell in which another example of the operating method is implemented, and FIG. A schematic configuration diagram schematically showing an example of the main parts of a molten carbonate fuel cell, Part 4
FIG. 5 is a schematic configuration diagram schematically showing an example of the main part of a molten carbonate fuel cell in which another example of the fuel cell operating method according to the present invention is implemented, and FIG. It is a figure provided for explanation of the comparison result of the operating method of a battery, and the conventional method. The symbols and names of parts in the figures correspond as follows. 1-anode, 2-cathode. 3-Battery body. 4- Heater, 5- Auxiliary reformer, 36- Fuel reforming catalyst, Hoop lower, 8- Concentration sensor. 9-valve

Claims (1)

[Claims] 1. Supplying a reactive gas into the battery body during hot standby in which power transmission to the outside is substantially stopped while maintaining the temperature of the electrolyte disposed within the battery body above its melting point. A method of operating a fuel cell characterized by: 2. A fuel characterized by maintaining the battery body in a power generation state during hot standby, in which power transmission to the outside is substantially stopped while the temperature of the electrolyte disposed within the battery body is maintained above the melting point. How to operate a battery. 3. The method of operating a fuel cell according to claim 2, wherein the electric power obtained during hot standby is used as a power source for the battery heat-insulating means. 4. In a fuel cell in which a fuel reforming catalyst is disposed within the cell body, during normal power generation, a reaction gas reformed by a reformer for fuel gas reforming is supplied into the cell body;
During hot standby, in which power transmission to the outside is substantially stopped while the temperature of the electrolyte disposed within the battery body is maintained above its melting point, an unmodified reaction gas is supplied into the battery body. How to operate a fuel cell. 5. The method of operating a fuel cell according to claim 1 or 4, wherein the flow rate of the reaction gas supplied into the cell body during hot standby is set to 10% or less during normal power generation. 6. During hot standby, in which power transmission to the outside is substantially stopped while the temperature of the electrolyte disposed within the battery body is maintained above its melting point, the reactive gas discharged from the battery body is transferred into the battery body. A method of operating a fuel cell characterized by recycling the fuel cell. 7. A piping system for supplying and discharging reactive gas to and from the battery body during hot standby, which substantially stops power transmission to the outside while maintaining the temperature of the electrolyte disposed within the battery body above its melting point. 1. A method of operating a fuel cell, comprising: closing the cell body and sealing a reactant gas inside the cell body. 8. A claim characterized in that when the concentration of the reactant in the reactant gas becomes below a set value during the recycle loop, a new reactant gas is supplied into the battery body in which the concentration of the reactant exceeds the set value. The method of operating a fuel cell according to item 6. 9. An auxiliary reformer for fuel gas reforming with a capacity of 30% or less of the capacity required during normal power generation is installed, and the temperature of the electrolyte placed inside the battery is maintained above the melting point while the external A fuel cell power generation system characterized in that during hot standby in which power transmission to the cell is substantially stopped, a reaction gas reformed by the auxiliary reformer is supplied into the cell main body. 10. Multiple rib oars for fuel gas reforming are installed,
During hot standby, when the temperature of the electrolyte placed in the battery body is maintained above its melting point and power transmission to the outside is substantially stopped, only some of the above-mentioned plurality of reformers are used to release the reactive gas. A fuel cell power generation system characterized in that the fuel cell power generation system is configured to reform the reaction gas and supply the reformed reaction gas into the cell main body.