JPS62268066A - Starting method for fuel cell - Google Patents

Abstract

PURPOSE:To make a fuel cell body raisable up to the required starting temperature while controlling it according to a very strict program, by burning a part of fuel to be supplied, while recirculating generating heat and generated gas together with the remaining fuel, and raising the temperature to the extent of starting condition temperature of a fuel cell. CONSTITUTION:Energizing electric heaters 8 and 8' with a continuous rating current, a catalyzer surface is heated so as to become more than 500 deg.C, while an air feed blower 16 is driven while opening a control valve 10 slightly, and air is fed by degrees from a pipe line 9. On the catalyzer surface, combustion gets started, and heat of reaction in response to this combustion is generated there. Gas inclusive of nuburned fuel is recirculated while heating a cell pipe (or a cell pipe group) 11, and new fuel in quantity commensurate to fuel consumption is resupplied to a pipe line 5 from a PSA tower 4. Thus, combustion is continuously started at a catalytic combuster 7, whereby the cell pipe 5 is raised in temperature in succession. And, opening of the control valve 10 of the pipe line 9 is controlled so as to go along the specified temperature up program, adjusting an air feed quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for starting a fuel cell, particularly for use in molten carbonate and solid oxide fuel cell power plants operating under high temperature conditions. be.

[Conventional technology]

Fuel cell power plants generally include heating means to raise the temperature to their starting conditions.

A method conventionally used for this purpose will be explained with reference to FIG.

FIG. 2 is a flowchart of a conventional power generation plant using fuel cells. In the figure, 1 is a supply pipe for raw materials to the fuel reformer 2, which may already contain water vapor or contain water vapor as necessary.
In some cases, it may be replaced with a coal gasifier and gas normalizer system. 3 is a pipe to a pressure swing adsorption tower (PSA) 4; in this example, nitrogen and carbon dioxide are removed by the PSA 4, and then supplied to the fuel cell 6 via a pipe 5. For example, in the case of a conventionally known solid-state electrolyte fuel cell, the fuel cell 6 is usually 850
It starts operating at 1000°C and is used at 1000°C.

In addition, in the case of molten carbonate fuel cells, the temperature is 500°C to 5°C.
It is activated at temperatures above 50°C. In this example, the fuel cell 6 is tubular, with a fuel cell (anode) on its outer surface and an air rod (cathode) on the inner surface of the tube. To explain in more detail, the cell tube 1 constituting the fuel cell
A ceramic air introduction pipe 12 for supplying air is arranged in the inner row of 1.

Then, the cell tubes 11 of multiple stations are connected in series or in parallel 51], and the negative and positive electrodes are taken out from the respective anodes and cathodes via the electrical circuit 28, and are connected to the DC/AC converter (inverter) 29. The AC power converted into AC power is used for the power load 30.

In addition, normally, in the cell tube 11 of the fuel cell 6, the supply 5
Approximately 70% to 90% of fuel and 25% to 50% of air are consumed. That is, near the interior A (outlet of the cell tube 11) of the fuel n7!1 pond module 6, fuel and air are mixed and combusted. Thereafter, part of the air heats the air introduction pipe 12, and further heats the air heating pipe 21 through the piping 13 to the piping 18 in the gust preheater 17. The remainder is sent to another heat recovery system via piping 19. This air preheater 17 may be installed after another heat recovery system, such as a boiler gas turbine, depending on the case. Reference numeral 16 denotes an air introduction blower, which is connected to the air heating tube 21 through a pipe 20, and communicates with the air introduction pipe 12 of the fuel cell through pipes 22 and 23.

By the way, as mentioned above, in a molten carbonate fuel cell, 50
0°C to 550°C or higher, 85% for solid electrolyte fuel R4 batteries
The operating temperature of the battery cannot be reached unless it is heated to 0°C to 900°C. Therefore, in conventional fuel cell power generation plants,
The method used is to circulate heated inert gas to raise the temperature to the starting condition, then switch to the fuel and air system and enter the starting process.a41.42 in Figure 2
is an inert gas supply circulation line provided for this purpose, and 43 is a gas preheater for heating the inert gas.

The most commonly used inert gases are:
It is nitrogen gas.

[Problem that the invention seeks to solve]

As is clear from the above, the conventional method for starting up a fuel cell power plant requires an additional inert gas heating furnace or heat exchanger. Furthermore, if it is necessary to entrain water vapor into the fuel, a separate boiler and its supply piping must be provided, which raises the problem of increased equipment costs.

Moreover, the temperature increase rate for fuel cell startup is generally strictly ill! OL is required, whereas control via a heat exchanger has the problem of poor controllability because temperature changes are slow.

In view of the above circumstances, the present invention aims to solve the technical problem of providing a method for heating a fuel cell main body to a required INa degree while controlling it according to a strict program without requiring any special additional equipment. That is.

[Means for Solving the Problems] The fuel cell startup method according to the present invention burns a part of the fuel supplied to the fuel cell/X, and recycles the generated heat and generated gas together with the remaining fuel. It is characterized by circulating the fuel and raising the temperature to the starting condition temperature of the navigation fuel N pond.

The method of the present invention applies to a part of the fuel supply system (for example, a part of the internal space of the fuel cell main body) in a conventional fuel cell power generation plant.
This can be implemented simply by providing a catalytic combustor.

[Effect]

In the method of the present invention, the heat generated by burning fuel is used to
In order to raise the temperature of the pond, the heating can be strictly controlled by simply adjusting the amount of air supplied, and it can be carried out according to a detailed heating program.

Further, since water and interstitial gas are generated by fuel combustion, the sensible heat of combustion is utilized more effectively than when only inert gas is used due to the action of these generated gases, and inert gas is not required.

[Embodiments of the invention]

FIG. 1 is a flowchart illustrating an example of a fuel cell power plant configured to carry out the start-up method according to the present invention.

In the figure, 1 is a fuel supply pipe, 2 is a fuel reformer, and 4 is a fuel supply pipe.
PSA type gas adsorption, etc., 6 is the fuel cell body, 11 is the cell tube, 12 is the air introduction tube 12. 28 is the electric circuit for taking out the negative electrode and the positive electrode from the cell tube, 2 is the DC converter (inverter), 30 is the power load 30.17 is the air preheater, 21
1 is an air heating tube, and 16 is an air introduction blower. These structures and operations are the same as the power plant shown in FIG.

On the other hand, in this power plant, the inert gas supply circulation lines 41 and 42 and the gas preheater 43 shown in FIG. 1 are not provided. Instead, the following configuration is adopted in this case.

First, a catalytic combustor 7 is provided in a part of the main body of the fuel cell 6 at the tip of a communication pipe 5 for supplying fuel to the fuel cell 6 . The inside of the catalytic combustor 7 is filled with alumina ceramic particles or porous bodies impregnated with a catalyst. As the catalyst to be impregnated, vanadium (V)
Compounds such as , samarium (Sm), and lanthanum (La) are used, and noble metals such as platinum (Pt) may also be used.

The activation temperatures of these catalysts are as follows.

V system: 500°C Sm system: 400°C La system: 450°C Pt: 340-350°C As the activation temperature of the catalyst is quite high as mentioned above,
As shown in the figure, it is necessary to preheat the catalyst surface using electric heaters 8, 8' to assist combustion. Then, the electric heater 8.8' is turned off after the temperature reaches the catalyst activation temperature or higher. From this point of view, it is preferable to use a noble metal catalyst such as platinum, which has a low activation temperature.

The air necessary for combustion in the catalytic combustor 7 is supplied to a pipe 24 branching from the pipe 22 for introducing air into the fuel cell 6.
The fuel is sent through the control valve 10 and piping 9 into the catalytic combustor 7. The control valve 10 is connected to either a thermometer T or a water vapor concentration meter S provided in the fuel R4 battery main body 6, and can adjust the air supply level according to the detected temperature or water vapor level.

After leaving the fuel ffi pond body 6, the gas containing unburned fuel after being burned in the catalytic combustor 7 passes through the recirculation blower 14 and the pipes 15 and 15' from the middle of the pipe 13, and then passes through the pipe 5. Almost the entire amount can be recycled. In addition, by introducing a part of this recirculated gas into the PSA type gas adsorption tower 4 through a pipe 25 branched from the pipe 15, it becomes possible to remove CO2 (or water vapor if necessary) contained in the recirculated gas. ing. Note that the CO2 and water vapor separated and removed here are removed to the outside of the system via piping 26.

Next, an embodiment in which the startup method according to the present invention is applied to the fuel cell power plant shown in FIG. 1 will be described.

The fuel cell module 6 housing the cell tubes 11 or a group of cell tubes must be heated as slowly as possible, usually at 100° C./hour or less, and with little temperature variation. For this purpose, the following steps were taken.

First, the valve Vl provided in the pipe 13, the valve V2 provided in the pipe 23. After confirming that the valve V3 provided in the pipe 25 is also closed, fuel gas is supplied from the PSA type gas adsorption etc. 4 to the fuel cell module 6 through the pipe 5. At the same time, the recirculation blower 14 is driven, and the piping 13, 15.15'
Creates a fuel circulation system through the. A mixture of hydrogen and carbon monoxide can be used as fuel gas.

Next, the electric heaters 8 and 8' are energized so that the surface of the catalyst becomes 50%
Heat the temperature to 0°C or above, drive the air supply blower 16 while slightly opening the control valve 10, and pass the pipe 9 through the pipe 20, air heating pipe 21 (in a cold state), pipes 22 and 24.
Air is gradually supplied from At the surface of the catalyst, combustion occurs so that the oxygen in the air thus supplied is completely consumed, and corresponding heat of reaction is generated. Not yet! ! !
The gas containing the burnt fuel is recirculated while heating the cell tube (or cell tube group) 11 with the generated heat. Also, new fuel is supplied from the PSA tower 4 to the pipe 5 in an amount commensurate with the fuel consumption. In this way, combustion occurs continuously in the catalytic combustor 7, and the temperature of the cell tube 11 is continuously raised.

Naturally, the temperature increase rate of the cell tube 11 depends on the magnitude of the reaction heat, which in turn depends on the air supply level. Therefore, in order to raise the temperature in accordance with a predetermined temperature raising program, the opening degree of the control valve 10 provided in the piping 9 is controlled and the air supply is adjusted each time. At this time, by detecting the achieved temperature with a thermometer T provided in the fuel cell module 6 and setting the opening degree of the control valve 10 to II based on the detected temperature, reliable control according to the temperature increase program is possible. be. Incidentally, when the detected temperature reaches 3 degrees or higher for activation of the catalyst, the electric heaters 8 and 8' may be turned off, since the combustion reaction on the catalyst surface proceeds even without external heating.

The operating temperature condition of the fuel cell (100
0° C.), open valves V+ and V2 to introduce air into the fuel cell and start power generation.

Since this amount of introduced air is in excess of the amount consumed by the fuel cell, combustion of the remaining fuel by the excess air continues in the vicinity of the cell outlet indicated by A in the figure. For this reason, the temperature of the exhaust gas is maintained at a high temperature (B) close to 1000° C., so the exhaust gas is passed through the air preheater 17 and used for preheating the supplied air.

When the fuel consists only of hydrogen gas, the supply of air from the pipe 24 is cut off after the fuel cell is activated. However, when the fuel is a mixed gas of hydrogen gas and carbon monoxide gas, the air supply from the pipe 24 is continuously carried out without being cut off even if J5 is reached after the fuel cell is activated. As a result, in the catalytic combustor, partial combustion of hydrogen contained in the fuel gas is continued for a period of time, and a water vapor content of 3 to 4% is maintained at the inlet as well as residual heat of the fuel. In this case, the water vapor layer is detected by the water vapor thermometer S provided in the fuel cell 6, and the opening degree of the control valve 10 is adjusted based on the detection. By doing so, the water vapor layer can be controlled.

In addition, when water or carbon dioxide in the gas flow flowing through the membrane roll becomes excessive, check valve V3 to switch the gas flow to PS.
It is returned to Tower A and purged of excess water and carbon dioxide. The amount should be about 2 to 5% of the return gas, and this is the valve v
This is done by adjusting the opening of step 3 or operating a flow port setting device (not shown).

As is clear from the above explanation, in the method of this embodiment, a part of the fuel gas is catalytically combusted, and the combustion heat generated at that time directly heats the fuel cell to raise the temperature to a predetermined operating temperature. There is. Therefore, when compared with the conventional method of raising the temperature to a predetermined starting temperature via a high-temperature inert gas, the following various advantages can be obtained.

The first is that it has good heating efficiency. This means that the rate of temperature rise can be precisely controlled and the fuel cell can be started up smoothly and in a short time. As a result, it is possible to start up the fuel cell module in a short time, and since the fuel cell module can be raised easily, there is no risk of damage.

Second, there is no need for an inert gas supply line or preheater. In addition, since the necessary amount of mixed steam can be achieved by partial combustion of hydrogen, there is no need to use separate boiler equipment. Therefore, the effect of reducing device costs can be obtained.

Thirdly, since there is no need to switch between inert gas and fuel gas, the startup process is simplified.

(Effects of the Invention) As detailed above, according to the startup method of the present invention, the fuel cell main body 8 It has remarkable effects such as being able to smoothly and quickly raise the temperature to the required temperature while controlling the drum according to a complete program.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an example of a fuel cell power generation plant configured to carry out the startup method of the present invention, and FIG. 2 is a flowchart for explaining a conventional startup method in a fuel cell power generation plant.

Claims (1)

[Claims] combusting a portion of the fuel supplied to the fuel cell and recirculating the generated heat and product gas with the remaining fuel;
A method for starting a fuel cell, the method comprising raising the temperature to the temperature required for starting the fuel cell.