JPH0589899A - Internal reforming type fused carbonate fuel cell and operation thereof - Google Patents

Abstract

(57) [Summary] [Purpose] The internal reforming molten carbonate fuel cell is easily heated at the time of start-up so that independent power generation is possible. [Composition] At least a part of the fuel is burned in a catalytic combustor 2 to consume oxygen in the air, and then the combustion gas is supplied to both the anode side and the cathode side of the internal reforming molten carbonate fuel cell 1. Then, the fuel cell is heated to a predetermined temperature. [Effect] It is possible to make a power generator in the form of a package as an independent power source without using a special heating method from the outside.
The internal reforming molten carbonate fuel cell can be easily operated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal reforming molten carbonate fuel cell and a method of operating the same, and more particularly to an internal fuel cell which enables easy heating of the cell body at the start of operation of the fuel cell. The present invention relates to a reformed molten carbonate fuel cell and an operating method thereof.

[0002]

2. Description of the Related Art Since a molten carbonate fuel cell uses a molten carbonate as an electrolyte, the operating temperature of the cell is generally around 650 ° C. At the time of power generation, this temperature can be maintained by the heat generated by the battery itself, and in actual operation, it is also necessary to cool the battery in order to maintain the battery temperature at around 650 ° C.

[0003] On the other hand, at the start of power generation, that is, when the battery is started,
It is necessary to heat the cell body to around 650 ° C. to at least a temperature at which carbonate ions can move. As a heating method for this, in the external reforming molten carbonate fuel cell, reforming gas, that is, reforming gas from the reformer is used. Generally, a method of heating by supplying to the battery main body or a method of receiving an external power source only at the time of starting and heating by an electric heater is used.

As a temperature raising means at the time of starting the operation of the external reforming type molten carbonate fuel cell, a mixed gas of a fuel gas containing hydrogen and an oxidant gas containing a predetermined amount of oxygen at the time of starting the operation of the fuel cell body. It is also known that the temperature of the fuel cell is increased by burning it and introducing the obtained high temperature gas into the main body of the fuel cell (see JP-A-59-98471).

[0005]

Generally, when heating with a reforming gas or an electric heater, it is extremely difficult to make the temperature distribution generated in the battery main body uniform. For example, when a reforming gas is used, it must be supplied only to the anode side, so that a temperature difference occurs between the reforming gas and the cathode side, strain occurs in the cell, and problems such as damage to the electrolyte plate occur. Is coming. In addition, when heating with an electric heater, it is substantially difficult to install the heater for each cell, so a large temperature difference occurs between the vicinity of the heater and the vicinity thereof, and similar to the increase in the size of the battery. The phenomenon may appear significantly.

By the way, a hydrocarbon gas such as methane or natural gas is directly supplied to the anode side of a fuel cell, reformed into a hydrogen-rich gas using a catalyst inside the cell, and a molten carbonate is used as an electrolyte for oxidation. In a fuel cell that uses a mixed gas of air and carbon dioxide as an agent, a so-called internal reforming molten carbonate fuel cell, the fuel is reformed inside the cell body, that is, reformed into hydrogen. It does not have a reformer such as a quality molten carbonate fuel cell. Therefore, it is impossible to heat the battery main body by the reforming gas from the reformer itself. On the other hand, it is generally performed that the heater is heated by receiving electricity from the external power source. Heating is not always sufficient, and when it is used as an independent power source in a place where there is no external power source, for example, in a remote island, it is impossible to heat with an electric heater, and the internal reforming type molten carbonate fuel cell There is a demand for a simple and reliable method for preheating at the start of power generation.

Further, the means started in the above-mentioned Japanese Patent Laid-Open No. 59-98471 is effective as a temperature raising means for a fuel cell using a fuel containing hydrogen, that is, an external reforming fuel cell. As described above, in the case of the internal reforming type fuel cell, since the fuel used does not have a hydrogen component, the above means should be used as it is as the heating means of the internal reforming type molten carbonate fuel cell. I can't.

An object of the present invention is to disclose an internal reforming type molten carbonate fuel cell and a method of operating the same, which eliminates the above-mentioned problems of the prior art occurring at the time of starting the fuel cell. It is possible to obtain an internal reforming fuel cell that can be used as an independent power source. That is, according to the present invention, it is possible to easily heat the internal reforming fuel cell by reducing the temperature distribution in the cell even in the absence of a remote island or other power source, and after heating, supply the fuel and the oxidizer. This makes it possible to generate electricity.

[0009]

In order to achieve the above object, the present invention provides an internal reforming molten carbonate fuel cell body having a reforming catalyst on the anode side, and a part of the fuel used at the start of power generation. Disclosed is an internal reforming molten carbonate fuel cell, which is equipped with a means for mixing and burning air with air, and a means for supplying the heated gas after combustion to the anode side and / or the cathode side. To do.

A means for returning a part of the heated gas discharged from the cell body to a means side for mixing and burning the used fuel and air, and the cell temperature are not monitored. By further including means for controlling the amount of gas, it is possible to achieve the object more.
The present invention further relates to a method for operating an internal reforming molten carbonate fuel cell in which a hydrogen-free fuel such as methane gas or natural gas is directly supplied to the fuel cell without reforming to generate electric power. At times, a part of the fuel and air are burned, oxygen in the air is consumed, and then the heated gas after burning is supplied to the anode side and / or the cathode side, thereby making the fuel cell main body suitable for operation. Also disclosed is a method of operating an internal reforming molten carbonate fuel cell, which is characterized by heating to different temperatures.

A part of the heated gas discharged from the cell body is returned to the side of the means for mixing and burning the used fuel and air, and further, a part of the fuel and the fuel of air are It is a more preferable embodiment to carry out the reaction under an air amount smaller than that required for the oxidation reaction of the fuel.

[0012]

That is, in the present invention, a part of the fuel is mixed with air and burned, and the gas whose temperature has risen is supplied to the anode side and / or the cathode side to make the temperature distribution in the cell uniform. It heats the battery. In the present invention,
All oxygen in the air in the mixed gas of the fuel gas and air is consumed in the oxidation reaction of the fuel, so even if it is supplied to the anode side, the anode is not oxidized. Also, as a matter of course, since the fuel is not reformed, it does not reduce the cathode.

Combustion of fuel and air may be carried out using a combustion furnace or may be carried out using a catalytic combustor. Further, when the heated gas is recycled and used, improvement in heating efficiency can be expected. At this time, by detecting the battery temperature and controlling the recycled gas amount, fuel, air, and exhaust gas amount according to the temperature, heating can be easily performed under desired conditions.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in more detail based on the description of embodiments with reference to the drawings. FIG. 1 is a block diagram showing only a portion related to heating of a cell body at the start of power generation of an internal reforming molten carbonate fuel cell according to the present invention. In the figure, 1 is an internal reforming type molten carbonate fuel cell main body having a reforming catalyst on the anode side, and a conventionally known one can be used as it is in the present invention. No detailed explanation will be given.

A pipe 21 for a fuel gas inlet is connected to the cell body. The pipe 21 has a branch pipe 22,
The branch pipe 22 is connected to the battery main body 1 via a flow control valve 32.
Is connected to a catalytic combustor 2 provided adjacent to the. A pipe 23 for further introducing air to the catalytic combustor 2
Are connected via a flow control valve 33, and a pipe 24 is provided on the combustion gas discharge side. The pipe 24 is bifurcated, and one branch pipe 25 is connected via a flow control valve 35. The branch pipe 26 is connected to the fuel supply pipe 21, and the other branch pipe 26 communicates with the oxidant inlet side of the cell body. Further, a valve 31 is provided downstream of the branch portion of the branch pipe 22 in the fuel supply pipe 21, and steam is supplied further downstream in order to smoothly reform the fuel in the cell body. The pipe 27 is connected via a valve 37.

Further, in this embodiment, branch pipes 42, 4 are provided from the anode side exhaust pipe 41 and the cathode side exhaust pipe 43 provided on the gas exhaust side of the battery body 1, respectively.
4 is provided, and both branch pipes 42 and 44 merge 45 to form a pipe line 46, which is connected and opened to the air introduction pipe 23. Flow rate control valves 51 and 53 are provided on the downstream sides of the branch portions of the branch pipes of the discharge pipes, respectively.
A valve 52 is provided in the. Further, the recycle blower 3 is provided in the pipe line 46 at an appropriate position in the flow line, and acts to recirculate the gas in the pipe line to the upstream side, that is, the air introduction pipe 33 side.

The internal reforming molten carbonate fuel cell according to the present invention having such a structure is operated as follows at the start of power generation. The valve 31 provided in the fuel supply pipe 21 is closed, and the flow rate control valves 32 and 33 are adjusted to supply a predetermined amount of fuel gas of natural gas containing methane as a main component from the fuel supply pipe 21 side and a predetermined amount. Air is introduced from each of the air introduction pipes 23 and made to flow into the catalytic combustor 2. The inflowing fuel and air are agitated and mixed in the catalytic combustor 2 and burned. Since the combustion gas generated by this combustion may contain an oxygen component at the beginning of combustion, the valve 35 is closed and first introduced into the cathode side, and after a certain period of time, the valve 35 is opened and supplied to the anode side. By supplying this combustion gas, the entire fuel cell body is heated equally without any particular temperature gradient. Therefore, up to a predetermined temperature, for example, about 650 ° C., without causing inconvenience such as damage to the equipment due to partial thermal expansion
It can be heated up to.

When the cell body is heated to a predetermined temperature, the valve 31 is opened, the operation of the catalytic combustor is stopped, and the internal reforming fuel cell is switched to a normal operating state. Since the subsequent operating conditions are exactly the same as the operating conditions of the conventionally known internal reforming fuel cell, the description thereof will be omitted. The combustion gas supplied to the fuel cell main body is discharged from the exhaust pipes 41 and 43 on the anode side and the cathode side, respectively. The main components of the exhaust gas are residual methane,
It is carbon dioxide, carbon monoxide, water vapor, and nitrogen, and has a considerable amount of heat. Therefore, the battery body can be heated more efficiently by reducing and reusing the exhaust gas to the upstream side.

In that case, the flow control valves 51 and 53 provided in the exhaust pipes 41 and 43 are adjusted to limit the amount of exhaust gas, and at the same time, the valves 52 and 54 provided in the respective branch pipes 42 and 44 are installed. The exhaust gas is opened and fed into the recycle blower 3 through the pipe line 46, and is reduced into the air supply pipe 23 by the action of the blower. The reduced recycled exhaust gas mixes with the incoming air and flows into the catalytic combustor 2. Combustion occurs in the catalytic combustor 2 by mixing with the fuel introduced separately.

For such control, although not shown in the figure, one or a plurality of temperature detecting means are installed at a predetermined position of the battery main body, information from the temperature detecting means is monitored, and fuel and air are detected in accordance with the information. It is extremely effective to appropriately control the supply amount, the discharge amount of the heating gas, and the flow rate of the reflux gas. In addition, in the experiment conducted on the same battery main body, the heating rate was 15 ° C./° C. when the exhaust gas was not recirculated and when it was conducted.
h, and about 30 ° C./h, and the time required for heating to 650 ° C. was 44 hours and 22 hours.

In the present invention, by appropriately controlling the amounts of fuel and air to be introduced, it is possible to consume all the oxygen in the air by the oxidation reaction in the combustion in the combustor, and supply the combustion gas to the anode side. However, since the anode is not oxidized and the fuel used is unreformed fuel, the cathode is not oxidized. Therefore, the power generation of the conventionally known internal reforming molten carbonate fuel cell is not possible. The previous heating can be performed easily and surely, and the battery can be operated without causing any inconvenience.

In the description of the above embodiments, the catalyst combustor is used as the combustor, but this is merely an example, and any combustor such as a combustion furnace may be used in the same manner. Will be easily understood.

[0023]

According to the present invention, the internal reforming molten carbonate fuel cell can be easily heated to the power generation start temperature. Further, the battery can be easily started even in the absence of an external power source such as a remote island as an independent power source.

[Brief description of drawings]

FIG. 1 is a block diagram showing only a portion related to heating of an internal reforming molten carbonate fuel cell body according to the present invention.

[Explanation of symbols]

1: Internal reforming molten carbonate fuel cell, 2: Catalytic combustor, 3: Recycle blower, 21: Fuel supply pipe,
23: Air supply pipe

Front Page Continuation (72) Inventor Ken Minahana 3-1-1, Sachimachi, Hitachi City, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Hiroaki Suzuki 3-1-1, Sachimachi, Hitachi City, Ibaraki Prefecture No. Stock Company Hitachi Ltd.Hitachi factory

Claims (5)

[Claims] 1. An internal reforming molten carbonate fuel cell body having a reforming catalyst on the anode side, means for mixing and burning the used fuel and air at the start of power generation, and heating gas after combustion on the anode side and And / or a means for supplying to the cathode side, and an internal reforming molten carbonate fuel cell. 2. A means for returning a part of the heating gas discharged from the internal reforming type molten carbonate fuel cell body to a means side for mixing and burning the used fuel and air at the start of the power generation,
An internal reforming molten carbonate fuel cell, further comprising means for monitoring the cell temperature and controlling the supply amount of fuel and air and the exhaust gas amount. 3. A method for operating an internal reforming molten carbonate fuel cell in which a hydrogen-free fuel such as methane gas or natural gas is directly supplied to the fuel cell without reforming to generate electric power, and power generation is started. At times, the fuel and air are burned to consume oxygen in the air, and then the heated gas after burning is supplied to the anode side and / or the cathode side to bring the fuel cell main body to a temperature suitable for operation. A method for operating an internal reforming molten carbonate fuel cell, which comprises heating. 4. The cell temperature is monitored, and the supply amount of fuel and air and the exhaust gas amount are controlled based on the values, and a part of the heating gas discharged from the battery main body is used as a fuel to be used at the start of the power generation. The method for operating an internal reforming molten carbonate fuel cell according to claim 3, further comprising refluxing to the side of means for mixing and burning with air. 5. The fuel according to claim 3 or 4, characterized in that a part of the fuel and air are fueled under an air amount smaller than that required for the oxidation reaction of the fuel. Operating method of internal reforming molten carbonate fuel cell.