JPH01128364A - Generator of fused carbonate type fuel cell - 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 applies to fuel cells used in the energy sector that directly converts the chemical energy of fuel into electrical energy, and in particular to the cathode of molten carbonate fuel cells. The present invention relates to a power generation device for a molten carbonate fuel cell having a system for reducing the differential pressure generated between the anode and the anode to zero.

[Prior Art] The molten carbonate fuel cells that have been proposed to date use an electrolyte plate (tile), which is made by impregnating a porous material with molten carbonate as an electrolyte, as a cathode (oxygen collector) and an anode (fuel One cell is one in which electricity is generated by the potential difference generated between the cathode and the anode by sandwiching the cell from both sides with the electrodes, supplying oxidizing gas to the cathode side and supplying fuel gas to the anode side. It has a structure in which each cell is laminated in multiple layers with a separator in between.

In the above-mentioned molten carbonate fuel cell, the reaction H2+ CO3--→H20+ C02+ 2 e- takes place on the anode side, and the reaction takes place on the cathode side, so the C 02 obtained on the anode side
It is necessary to make sure that the current is sent to the cathode side.

In the conventional power generation system of a natural gas reformed molten carbonate fuel cell that uses natural gas as the fuel gas, the power generation system shown in FIG. The system is as outlined below.

That is, in order to supply oxidizing gas to the cathode 2 of the fuel cell 1, air A is compressed by a blower 4, preheated by an air preheater (not shown), and supplied to the cathode 2 by a line 5. - part is supplied to the reformer 6 by a branch line 7, and the gas discharged from the cathode 2 is discharged through a line 8 through the air preheater. On the other hand, natural gas NG supplied to the anode 3 of the fuel cell 1 is introduced into the reformer 6 through a line 9, reformed there, supplied to the anode 3, and discharged from the anode 3. The unburned gas is natural gas NG, which is introduced into the reformer 6 to be used as fuel for the reformer.
The gas containing carbon dioxide discharged from the reformer 6 is further led to the line 5 from the CO2 recovery line 10. , is supplied to the cathode 2 together with air, and carbon dioxide gas is recovered to the cathode 2 side.

[Problems to be Solved by the Invention] However, in the conventional power generation system described above, a gas pressure difference tends to occur between the cathode 2 and the 7-node 3 of the fuel cell.
If a pressure difference occurs, there is a risk of cracking the electrolyte plate, so it is necessary to prevent the pressure difference between the cathode and the anode as much as possible. Exit side (inlet side is also fine)
A differential pressure gauge 11 is provided between them, and a valve 12 is provided on the outlet side of the anode 3, and the opening degree of the valve 12 is adjusted so that the differential pressure between the node 3 and the cathode 2 falls within the suggested value of 8'. It was necessary to install a differential pressure control mechanism.

Therefore, the present invention aims to make it possible to reduce the differential pressure between the anode and cathode to zero without providing a differential pressure control mechanism as in the conventional system.

[Means for Solving the Problems] In order to achieve the above object, the present invention introduces the exhaust gas discharged from the cathode into the combustion chamber of the reformer in the same manner as the gas discharged from the anode of the fuel cell. At the same time, part of the exhaust gas from the cathode is bypassed and discharged, and carbon dioxide gas in the gas containing carbon dioxide discharged from the reformer is recovered and supplied to the cathode. The piping is configured such that natural gas is reformed by the reformer and supplied to the anode.

[Function] By making the combustion chamber side of the reformer a common header for the anode and cathode of the fuel cell, the differential pressure between the anode and cathode becomes zero, eliminating the need for a separate mechanism for differential pressure control as in the past. There is no need to provide one.

Further, carbon dioxide gas and water obtained by the reaction at the anode are taken out from the combustion chamber outlet of the reformer, and the carbon dioxide gas necessary for the cathode is sent to the cathode through an air supply line to the cathode. When the exhaust gas discharged from the cathode is introduced into the combustion chamber of the reformer, the combustion temperature cannot be raised to the temperature required for the reforming reaction because the exhaust gas contains inert gas, etc. However, by bypassing a portion of the exhaust gas, this problem can be avoided.

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

FIG. 1 shows an embodiment of the present invention.
is introduced into the reformer 6 via a line 9 via a natural gas preheater 13 and a desulfurizer 14, reformed there, and passed through the natural gas preheater 13 via a line 15. In addition to supplying the anode 3 to the node 3,
The gas discharged from the reformer 6 is introduced into the combustion chamber of the reformer 6 through the discharge line 16, while the air △
After being compressed by the blower 4, the entire amount is supplied to the cathode 2 through the air preheater 7 and the line 5, and
The gas discharged from the cathode 2 is directly introduced into the combustion chamber of the reformer 6 through the line 18, which is a feature of the present invention, so that the combustion chamber side of the reformer 6 is connected to the cathode side gas and the anode side. It is used as a common header for gas, and a branch line 1 is installed in the middle of the above line 18.
9 is connected, a part of the gas discharged from the cathode 2 is bypassed by the branch line 19, and the air preheater 17 is connected to the air preheater 17.
Let it drain through. In addition, since the combustion chamber side of the reformer 6 is used as a common header for each exhaust gas from the anode 3 and cathode 2 as described above, carbon dioxide (CO2) required by the cathode 2 is transferred from the anode 3 side. The gas (
In order to recover the carbon dioxide gas (containing carbon dioxide gas and water obtained at the anode), it is guided through a line 20 to a steam generator 21, a heat recovery heat exchanger 22, and a steam/water separator 23. The carbon dioxide gas (
The gas containing CO2 is sent from the steam/water separator 23 to the CO2 recovery line 24 in order to be sent to the cathode 2 of the fuel cell 1.
On the other hand, water (I(20) separated from the gas in the steam/water separator 23 is led to the steam generator 21 through a line 25, from where it is introduced into the inlet side of the air preheater 17. The waste gas is introduced into the natural gas line 9 and fed into the reformer 6 together with the natural gas.

In conventional power generation systems using molten carbonate fuel cells, the gas discharged from the cathode 2 is discharged after heat recovery, but in the present invention, the exhaust gas from the cathode side is combined with the gas discharged from the anode 3. Similarly, the combustion chamber side of the reformer 6 is introduced into the combustion chamber of the reformer 6.
Since the common header is used for the gas from the node and the gas from the cathode, the differential pressure between the anode 3 and the cathode 2 becomes zero in principle. Therefore, it is possible to omit separately installing a differential pressure control mechanism. At this time, cathode 2
The gas discharged from the fuel cell contains a large amount of cooling air inside the fuel cell (cooling air accounts for 7 to 70% of the air required for the reaction).
8 times), the entire amount of exhaust gas from cathode 2 is transferred to reformer 6.
If the exhaust gas is introduced into the combustion chamber of the cathode 2, it will not be possible to raise the combustion temperature to the temperature required for the reforming reaction, but since a part of the exhaust gas from the cathode 2 is bypassed by the branch line 19, the temperature required for reforming will be increased. can be secured. In this case, since the exhaust gas contains a large amount of cooling gas, a large amount of air is bypassed.

On the other hand, the gas taken out from the combustion chamber outlet of the reformer 6 contains CO2 and 820 obtained at the anode 3, but after heat recovery, this gas is passed through the steam separator 23 to become carbon dioxide. The water is mixed into the natural gas and recovered as steam necessary for the reforming reaction, and the carbon dioxide gas is recovered by being supplied to the cathode 2 together with air. At this time, the gas taken out from the combustion chamber of the reformer 6 is separated into steam and water and recovered as is, so that the C 02 and 820 produced by the reaction at the 7 nodes 3 can be recovered without being diluted as much as possible.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it is of course possible to make various changes within the scope of the present invention, such as omitting a heat exchanger for heat recovery, etc., without departing from the gist of the present invention. It is.

[Effects of the Invention] As described above, according to the present invention, the gas discharged from the cathode of the molten carbonate fuel cell is directly introduced into the combustion chamber of the reformer, and the gas discharged from the combustion chamber side of the reformer is directly introduced into the combustion chamber of the reformer. Since it is used as a common header for gas from the cathode and gas from the anode, the differential pressure between the anode and cathode can be reduced to zero in principle, and there is no need to install a mechanism to control the differential pressure. In addition, since the gas containing CO2 and H2O taken out from the combustion chamber outlet of the reformer is separated and recovered, CO2 and 820 produced at the anode can be removed.
It is possible to achieve excellent effects such as being able to recover the material without diluting it as much as possible.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of the present invention, and FIG. 2 is a diagram schematically showing a power generation system using a conventional molten carbonate fuel cell. DESCRIPTION OF SYMBOLS 1... Fuel cell, 2... Cathode, 3... Anode, 6... Reformer, 17... Air preheater, 18...
- Line, 19...branch line, 23...steam water separator.

Claims (1)

[Claims] 1) The gas discharged from the anode of the molten carbonate fuel cell is introduced into the combustion chamber of the reformer, and a part of the gas discharged from the cathode is bypassed and the rest is introduced into the combustion chamber of the reformer. The carbon dioxide gas in the gas from the combustion chamber outlet of the reformer is recovered and supplied to the cathode, and the natural gas is reformed by the reformer to the anode. What is claimed is: 1. A power generation device using a molten carbonate fuel cell, characterized in that each pipe is connected to supply a molten carbonate fuel cell.