JPH0737602A - Gas recovery system of molten carbonate fuel cell - Google Patents

Abstract

PURPOSE:To prevent explosion and deterioration of a catalyst by installing a heat accumulator and an anode exhaust gas supply pipe at the insides of two gas passages, and by constituting directional control valves so that the anode exhaust side is connected to the exhaust gas apply pipe and another gas passage is connected to a cathode. CONSTITUTION:A fuel cell 1 consists of an electrolyte 2, an anode 3, and a cathode 4. A combustion housing 8 and two gas passages 9a, 9b are installed in a heat storage combustion chamber 7. Heat accumulators 10a, 10b, and anode exhaust gas supply pipes 11a, 11b are installed in the gas passages 9a, 9b respectively. When a first directional control valve 12 connects the exhaust gas supply pipe 11a to the exhaust side of the anode 3, a second directional control valve 13 connects the gas passage 9b to the supply side of the cathode 4, and this connection is alternately switched at specified intervals. The heat accumulators 10a, 10b alternately accumulate anode exhaust gas combustion heat to heat air 15 and to maintain automatic combustion of an anode exhaust gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten carbonate fuel cell gas recovery system which can be operated safely with a simple system configuration.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an example of a conventional exhaust gas recovery system for a molten carbonate fuel cell. The fuel cell 1 has an electrolyte 2 and an anode 3 and a cathode 4 that are in contact with both sides of the electrolyte 2. The fuel cell 1 supplies fuel gas to the anode 3 side, and the cathode 4 side is usually composed of a mixed gas of air and carbon dioxide gas. By supplying an oxidant gas, chemical energy is directly converted into electric energy by an electrochemical reaction to obtain electric power. In the exhaust gas on the anode 3 side, in addition to carbon dioxide gas and water, flammable gas composed of hydrogen and carbon monoxide remains, and the flammable gas is burned by the combustion catalyst 5
Is introduced into the catalytic combustion apparatus 6 and burned by the air supplied to the catalytic combustion apparatus 6 to recover the generated heat and also to collect and supply the combustion gas as an oxidant gas to the cathode 4. Further, in order to cool the fuel cell, it is general to provide a cathode recycle line 7 for recycling a part of the exhaust gas on the cathode 4 side to the inlet of the cathode 4.

[0003]

However, in the above-mentioned conventional method, in the catalytic combustion device 6, the combustible gas on the exhaust side of the anode 3 is mixed with oxygen.
There is a problem that the structure and control for controlling the concentration of combustible gas below the lower explosion limit become complicated. Also,
There is also a problem that the combustion catalyst deteriorates. Therefore,
The combustible gas on the exhaust side of the anode 3 is directly burned by a burner.
Although a method of burning is considered, the operating temperature of the molten carbonate fuel cell is as low as about 600 to 700 ° C., and the amount of heat of the combustible gas on the exhaust side of the anode 3 is several hundred kcal / N.
m ^{3 is,} for example, only about 200 kcal / Nm ^{3, and} it was difficult to burn with a normal burner.

The present invention solves the above problems and provides a highly safe gas recovery system for a molten carbonate fuel cell by making the exhaust gas from the anode of the fuel cell combustible by a heat storage type combustion device. The purpose is to provide.

[0005]

To this end, the present invention has an electrolyte 2 and an anode 3 and a cathode 4 which are respectively in contact with both surfaces of the electrolyte 2, and a fuel gas is supplied to the anode 3 side to form a cathode. In a molten carbonate fuel cell that supplies an oxidant gas to the fourth side, two gas passages 9a and 9b provided in a combustion housing 8 and heat storage bodies 10a and 10b and an anode arranged in the gas passages 9a and 9b Exhaust gas supply pipes 11a, 11b, first switching means 12 for alternately connecting the exhaust side of the anode 3 and the anode exhaust gas supply pipes 11a, 11b, and air for gas passages 9a, 9b.
Can be alternately connected to the gas passages 9a, 9b
And a second switching means 13 for alternately connecting the cathode 4 to the supply side of the cathode 4. It should be noted that the numbers added to the above-mentioned configurations are for comparison with the drawings in order to facilitate understanding of the present invention, and the configurations of the present invention are not limited thereby.

[0006]

In the present invention, combustion occurs alternately in the anode exhaust gas supply pipe at predetermined time intervals, and the heat storage bodies are alternately heated,
Since the heat is stored, the exhaust gas of the anode alternately supplied from the anode exhaust gas supply pipe can be automatically and continuously combusted, and the combustion gas can be continuously supplied to the cathode.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of an exhaust gas recovery system for a molten carbonate fuel cell of the present invention. Fuel cell 1
Has an electrolyte 2 in which a molten alkali carbonate is held by an electrolyte holding material, and an anode 3 and a cathode 4 which are in contact with both surfaces of the electrolyte 2, respectively, and the fuel cell 1 has about 60
The fuel gas is supplied to the anode 3 side and the oxidant gas is supplied to the cathode 4 side by operating at 0 to 700 ° C. As the fuel gas, for example, hydrocarbon and water vapor or a gas obtained by mainly reforming it into hydrogen and carbon monoxide is used, and as the oxidant gas, air and carbon dioxide gas supplied from the catalytic combustion device 6 are used. A mixed gas may be used, and the air 14 may be mixed therein. The exhaust gas from the anode 3 is collected by the regenerative combustion device 7, burned by the air 15 supplied thereto, and the combustion gas is supplied to the cathode 4 as an oxidant gas.

The heat storage type combustion device 7 includes a combustion housing 8 and two gas passages 9 provided in the combustion housing 8.
a, 9b, the heat storage bodies 10a, 10b arranged in the gas passages 9a, 9b, and the anode exhaust gas supply pipe 11
a and 11b, and the anode exhaust gas supply pipe 11a,
11b is connected to the exhaust side of the anode 3 via the first switching valve 12, and the gas passages 9a and 9b are connected to the second switching valve 1
It is connected to the air supply side of the cathode 4 via 3. In the embodiment of FIG. 1, the first switching valve 12 is a three-way switching valve and the second switching valve 13 is a four-way switching valve. However, the present invention is not limited to this. A combination of various switching valves can be adopted. In short, the first switching valve 12 includes the anode exhaust side and the anode exhaust gas supply pipe 11
The second switching valve 13 is a first switching means that allows the a and 11b to be alternately connected, and the second switching valve 13 allows the air to be alternately connected to the gas passages 9a and 9b, and the gas passages 9a and 9b to be connected to the cathode supply. It is the second switching means that enables the alternate connection to the air side.

The operation of the present invention having the above structure will be described. First, the first switching valve 12 and the second switching valve 1
3, in the state of FIG. 1, the exhaust gas of the anode 3 is supplied to the combustion housing 8 through the first switching valve 12 and the anode exhaust gas supply pipe 11a as shown by the solid arrow, and the air is supplied to the second housing. It is supplied to the combustion housing 8 through the switching valve 13, the gas passage 9a, and the heat storage body 10a. The heat storage body 10a has been stored at a high temperature at the time of the previous exhaust, and this heat storage body 10a
The air 15 is heated by a to a temperature at which the low-calorie gas can self-combust. In this way, the anode exhaust gas is combusted in the combustion housing 8, the combustion gas is exhausted through the heat storage body 10b on the gas passage 9b side, and the heat is stored in the heat storage body 10b.
The heat of the combustion gas is stored, and the combustion gas is supplied to the cathode 4 as an oxidant gas through the gas passage 9b and the second switching valve 13.

After a predetermined time, when the first switching valve 12 is rotated 90 ° in the direction of arrow A and the second switching valve 13 is rotated 90 ° in the direction of arrow B, the exhaust gas from the anode 3 becomes as shown by the dotted arrow. , Is supplied to the combustion housing 8 through the first switching valve 12, the anode exhaust gas supply pipe 11b, and air is supplied to the combustion housing 8 through the second switching valve 13, the gas passage 9b, and the heat storage body 10b. . The heat storage body 10b is stored at a high temperature at the time of the previous exhaust, and the heat storage body 10b heats the air 15 to a temperature at which the low-calorie gas can self-combust. In this way, the anode exhaust gas is burned in the combustion housing 8, and the combustion gas is stored in the heat storage body 10a on the gas passage 9a side.
Is exhausted through the heat storage body 10a and the combustion gas is stored in the gas passage 9a and the second switching valve 1.
It is supplied as an oxidant gas to the cathode 4 via 3

After that, the first and second switching valves 12 and 13 are switched at predetermined time intervals, and combustion alternately occurs on the anode exhaust gas supply pipe 11a side and the anode exhaust gas supply side 11b side.
Since a and 11b are alternately heated and accumulated to about 1000 ° C., the exhaust gas of the anode 3 alternately supplied from the anode exhaust gas supply pipes 11a and 11b is automatically and continuously combusted, and the combustion gas is used as a cathode. 4 can be continuously supplied.

FIG. 2 is a block diagram showing a modified example of the heat storage type combustion apparatus in the present invention. In the above embodiment, the anode exhaust gas supply pipes 11a and 11b are connected to the gas passages 9a and 9a.
Although the heat storage bodies 10a and 10b are provided so as to penetrate along the axial direction of b, in the present example, the tips of the anode exhaust gas supply pipes 11a and 11b are connected to the heat storage bodies 10a and 10b from the outer periphery of the gas passages 9a and 9b. It is placed in the front part of.
The tips of the anode exhaust gas supply pipes 11a and 11b may be arranged at the rear of the heat storage bodies 10a and 10b.

[0013]

As is apparent from the above description, according to the present invention, by making the exhaust gas of the anode of the fuel cell combustible by the regenerative combustion device, there is a risk of explosion like combustion by a conventional catalyst. It is possible to provide a highly safe gas recovery system that does not cause deterioration of catalysts and catalysts.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an exhaust gas recovery system for a molten carbonate fuel cell of the present invention.

FIG. 2 is a configuration diagram showing a modified example of the heat storage type combustion device in the present invention.

FIG. 3 is a configuration diagram showing an example of an exhaust gas recovery system for a conventional molten carbonate fuel cell.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 2 ... Electrolyte, 3 ... Anode, 4 ... Cathode 7 ... Heat storage type combustion device, 8 ... Combustion housing 9a, 9b ... Gas passage, 10a, 10b ... Heat storage body 11a, 11b ... Anode exhaust gas supply pipe, 12 ... first switching means 13 ... second switching means, 14, 15 ... air

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Sakurada 1-3-1, Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Tonen Research Institute

Claims (1)

[Claims] 1. A molten carbonate fuel having an electrolyte and an anode and a cathode that are in contact with both surfaces of the electrolyte, respectively, and supplies fuel gas to the anode side and oxidant gas to the cathode side. In the battery, two gas passages provided in the combustion housing, a heat storage body and an anode exhaust gas supply pipe disposed in these gas passages, and the anode exhaust side and the anode exhaust gas supply pipe can be alternately connected. 1. A gas recovery system comprising: a switching unit 1 and a second switching unit capable of alternately connecting air to the gas passage and alternately connecting the gas passage to the cathode air supply side. .