JPH0821412B2 - Fuel cell power generation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power generation method for a fuel cell, in which hydrogen gas is supplied to a fuel electrode of a fuel cell main body and oxidizing gas is supplied to an air electrode to generate power. In particular, the present invention relates to a power generation method for a fuel cell in which water in the anode outlet gas is not drained and the air preheater is divided into two stages to enhance the cooling effect and efficiently generate power.

[Prior Art] The principle of the fuel cell is the reverse reaction of electrolysis of water,
Hydrogen in fuel and oxygen in air are chemically reacted to simultaneously extract electricity and water.

This will be described with reference to FIG. 2. In the fuel cell main body 1, a porous fuel electrode (anode) 2 that reacts with a fuel gas such as hydrogen, and an air electrode (cathode) 3 that reacts with an oxidizing gas.
And an electrolyte 4 composed of a carbonate interposed between the electrodes 2 and 3, a fuel gas containing hydrogen is supplied to the fuel electrode 2 as shown in the figure, while oxygen and carbon dioxide gas are supplied to the air electrode 3. As a result, an oxidizing gas containing oxygen is supplied, and the electrodes 2 and 3 react as shown in the figure, and hydrogen and oxygen react with each other through the carbonate ion (CO ₃ ²⁻ ) to generate electricity.

The fuel cell main body 1 is stacked in a multiplicity of stages to obtain a high output. FIG. 3 shows an example of a conventional fuel cell power generation system.

That is, in the figure, 1 is a multi-layered fuel cell body, 5 is a reformer that reforms a fuel gas such as LNG into a hydrogen-rich gas, 6 is a fuel gas compressor such as LNG, 7 is a fuel preheater, and 8 is desulfurization , 9 is a heat exchanger, 10 is a feed pump, 11 is a feed heater, 12 is a condenser, 13 is a gas-liquid separator, 14 is a blower, 15 is an air compressor, 16 is an air preheater, and 17 is a chimney. is there.

First, fuel gas such as LNG is preheated by a fuel preheater 7 from a fuel gas compressor 6, desulfurized by a desulfurizer 8 and then supplied to a reformer 5, and is heated by a water supply pump 10 through a water heater 11. The vapor is supplied to the reformer 5, where the fuel gas is reformed into hydrogen-rich gas and carbon monoxide and supplied to the fuel electrode (anode) 2 of the fuel cell body 1. Anode gas generated in this fuel electrode 2 (H ₂ O, C
(O ₂ , CO, H ₂ etc.) passes through the heat exchanger 9 and the fuel preheater 7, the feed water is heated by the heater 11, and the moisture in the anode gas is removed by the condenser 12 and the gas-liquid separator 13. After that, it is used as a heating source of the reformer 5 from the blower 14 through the heat exchanger 9. Further, the air passes from the air compressor 15 through the air preheater 16 and is preheated by the exhaust gas that has exited from the air electrode (cathode) 3 of the fuel cell main body 1, and a part of the air is heated to the air electrode 3 and the rest is heated to the reformer 5. Which is supplied as a source, burns the residual H ₂ gas and CO gas in the anode gas in the reformer 5 to heat the fuel gas and steam passing through the reformer 5 to cause a reforming reaction.
It is supplied to the air electrode 3 as CO ₂ gas.

In the conventional power generation system of the fuel cell, the vapor in the anode outlet gas generated at the fuel electrode 2 is condensed by the condenser 12 and separated by the gas-liquid separator 13 to remove the water, and the anode outlet gas (CO ₂ , CO, H ₂ ) is supplied to the reformer 5 so that the reaction temperature in the reformer 5 is maintained.

[Problems to be Solved by the Invention] However, in order to remove water (vapor) in the anode outlet gas of the fuel cell main body 1, the anode gas must be cooled and then heated again. Therefore, there is a problem that the number of devices increases and the device cannot be made compact.

Further, the air supplied to the air electrode 3 also has a cooling action because the fuel cell main body 1 itself is accompanied by an exothermic reaction, and if the exhaust gas from the air electrode 3 is preheated to a high temperature, It is not preferable because the temperature inside the air electrode 3 rises too much.
Therefore, if the capacity of the air compressor 15 is increased and the preheated air temperature is lowered, the power consumption of the compressor increases and there is a problem that efficiency deteriorates.

The present invention has been made in consideration of the above circumstances, and maintains the reforming temperature in the reformer with the minimum necessary device configuration without removing the water in the anode outlet gas generated in the fuel cell, and from the air electrode. It is an object of the present invention to provide a fuel cell power generation method capable of efficiently cooling the exhaust gas by effectively cooling the exhaust gas and reducing the power of auxiliary machinery.

[Means and Actions for Solving the Problems] In order to achieve the above-mentioned object, the present invention supplies a fuel gas and water vapor to a reformer to reform the hydrogen gas, and the hydrogen gas of the fuel cell main body is reformed. In a power generation method of a fuel cell for supplying power to a fuel electrode and supplying oxidizing gas to an air electrode of its main body to generate power, an anode gas containing water vapor generated by supplying hydrogen gas to the fuel electrode is heated by the reformer. After being used as a power source, it is supplied to the air electrode and exhaust gas from the air electrode is passed from the second air preheater to the first air preheater, while air is passed from the first air preheater to the second air preheater. , A part of the preheated air that has exited the first air preheater is supplied to the air electrode, and the high temperature preheated air that has exited the second air preheater is
It is used as a heating source for the reformer and then supplied to the air electrode, without separating the water contained in the anode outlet gas,
By supplying it as it is as a heating source of the reformer, the drain device becomes unnecessary, the inlet temperature of the fuel gas to the reformer can be increased without a preheater, and the first air preheater can be divided into two stages. By supplying the relatively low preheated air that has exited to the air electrode, the inlet air temperature can be reduced to a required value with a small flow rate, and the hot preheated air that has exited the second air preheater can be used as the heating source for the reformer It is possible to efficiently perform reforming in reformer and improve the utilization rate in a fuel cell.

[Embodiment] A preferred embodiment of the fuel cell power generation method according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an example of a flow sheet of a power plant for implementing the fuel cell power generation method of the present invention. In the figure, 1
Is a fuel cell main body, which comprises a fuel electrode (anode) 2, an air electrode (cathode) 3, and an electrolyte 4 containing a carbonate interposed between the electrodes 2 and 3. 5 is a reformer, which reacts fuel gas with steam to reform it into H ₂ gas and CO gas. The reformer 5 comprises a reaction tube 5a and a combustion chamber 5b for burning the residual H ₂ gas or CO gas in the anode outlet gas from the fuel cell body 1 with the supply air in order to heat the reaction tube 5a. 6 is a fuel gas compressor, and 8 is a desulfurizer.

The fuel gas from the fuel gas compressor 6 is connected through the first fuel preheater 18, the desulfurizer 8 and the second fuel preheater 19 to the reaction pipe 5a of the reformer 5 by the fuel gas supply line 20.

The hydrogen-rich gas that has exited the reaction tube 5a of the reformer 5 is supplied to the fuel electrode (anode) 2 of the fuel cell body 1, and the anode gas is supplied from the second fuel preheater 19 to the first by the line 21.
It is connected to flow through the fuel preheater 18 into the combustion chamber 5b of the reformer 5.

Air electrode 3 of fuel cell body 1 and combustion chamber 5b of reformer 5
Air to be supplied to the combustion chamber 5b of the reformer 5 from the air compressor 15 through the first air preheater 22 and the second air preheater 23 and the combustion air line 24, and from the combustion chamber 5b. The preheated air supplied to the cathode 3 through the line 25 and the first air preheater 22 is supplied to the cathode 3 through the air line 26 together with the gas (CO ₂ ) from the line 25 of the reformer 5. To be done.

The exhaust gas generated at the air electrode 3 is exhausted from the exhaust gas line 27 through the second air preheater 23 and the first air preheater 22 to a chimney or the like (not shown).
It is supplied to the steam generator 29 from 28. The steam generator 29 has a heat transfer tube 30, a gas-liquid separation drum 31 is connected to the heat transfer tube 30, the feed water in the heat transfer tube 30 is heated by the exhaust gas from the line 28, and the gas is liquid-liquid at the separation drum 31. The separated and generated steam is supplied to the reaction tube 5a of the reformer 5 through the steam line 32.

A part of the gas reformed by the reformer 5 is circulated to the desulfurizer 8 through the return line 36. Blowers 33, 3 for circulating gas are provided between the fuel electrode 2 and the air electrode 3 of the fuel cell body 1.
4 is connected.

In the above, the fuel gas such as LNG is supplied to the first fuel preheater 1
It is preheated in 8 and desulfurized in desulfurizer 8.
It is preheated to a high temperature by and is supplied to the reaction tube 5a of the reformer 5. In this reaction tube 5a, the steam generated in the steam generator 29 is
It is supplied through the steam line 32, a reforming reaction of the fuel gas occurs, and is reformed into H ₂ rich gas containing CO gas and supplied to the fuel electrode 2 of the fuel cell body 1. The anode gas discharged from the fuel electrode 2 is fed from the line 21 to the second fuel preheater 19 and the first fuel preheater 19.
After preheating the fuel gas to a high temperature through the fuel preheater 18,
It is supplied to the combustion chamber 5b of the reformer 5.

On the other hand, the air from the air compressor 15 is the first air preheater.
In the anode gas supplied from line 21, the gas is preheated by the exhaust gas from the air electrode 3 there, and further preheated to a high temperature through the second air preheater 23 and then supplied to the combustion chamber 5b of the reformer 5. The remaining H ₂ gas and CO gas are burned, and the temperature inside the reaction tube 5a is maintained at a predetermined temperature at the burning temperature. Gas such as CO ₂ gas after combustion is supplied to the air electrode 3 through the line 25, and low-temperature preheated air that has passed through the air line 26 from the first air preheater 22 is supplied to the air electrode 3. The reaction described in section 2 occurs at each pole 2 and 3, and power is generated.

[Effects of the Invention] As is clear from the above, according to the present invention, the following excellent effects are exhibited.

(1) Since water in the anode gas generated at the fuel electrode of the fuel cell main body is not removed and used as it is as a heating source for the reformer, a drain device is not required unlike the conventional case, and the cost can be reduced accordingly.

(2) By preheating the air in two stages, using the high-temperature preheated air as the heating source for the reformer and supplying the low-temperature preheated air to the air electrode, the efficiency of the reformer is maintained and the fuel in the cell body is maintained. The utilization rate can be improved.

(3) Furthermore, since efficient cooling can be performed with a small amount of air, overall efficiency is also improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an apparatus for carrying out the fuel cell power generation method of the present invention, FIG. 2 is a diagram showing details of the fuel cell, and FIG.
The figure shows a conventional example. In the figure, 1 is a fuel cell main body, 2 is a fuel electrode, 3 is an air electrode, 5
Is a reformer, 20 is a fuel gas supply line, 22 is a first air preheater, 23 is a second air preheater, and 29 is a steam generator.

Claims (1)

[Claims] 1. A fuel gas and water vapor are supplied to a reformer to be reformed into hydrogen gas, and the hydrogen gas is supplied to a fuel electrode of a fuel cell body, while an oxidizing gas is supplied to an air electrode of the body. In a fuel cell power generation method for generating power, an anode gas containing water vapor generated by supplying hydrogen gas to the fuel electrode,
After being used as a heating source for the reformer, it is supplied to the air electrode and exhaust gas from the air electrode is fed from the second air preheater to the first air heater.
Pour into the air preheater, while allowing air to flow from the first air preheater to the second air preheater.
A part of the preheated air flowing from the first air preheater to the air preheater is supplied to the air electrode, and the high temperature preheated air discharged from the second air preheater is used as the heating source of the reformer. A power generation method for a fuel cell, which comprises supplying to an air electrode after a while.