JPS63279576A - Cathode recycle device for fused carbonate fuel cell - Google Patents

Abstract

PURPOSE:To dispense with a hot blower by having all oxidic gases exhausted out of the cathode, while mixing the partial gas turned to low temperature and atmospheric pressure with air, compressing it for pressure up, and supplying it to the cathode, thereby recycling it. CONSTITUTION:At a supply line 9 for feeding the cathode 2 with oxidic gas, the air A compressed by a compressor 6 is led thereinto through a heat exchanger 7, but at this heat exchanger 7, heat exchange takes place between the compressed air and the exhaust gas discharged out of an exhaust gas turbine 5. And, the compressed air is preheated and fed to the cathode 2, while the exhaust gas turns to low temperature and atmospheric pressure and is discharged out and, after the partial gas is mixed with air at the suction side of the compressor 6, it is compressed for pressure up at the compressor 6, then it is referred to the cathode 2. With this constitution, it gets off without using the conventional hot blower in consequence.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to fuel cells used in the energy sector that directly convert the chemical energy of fuel into electrical energy, and which is supplied to the cathode of a molten carbonate fuel cell. This invention relates to an oxidizing gas recycling device.

[Prior Art] Molten carbonate fuel cells that have been proposed to date include an electrolyte plate (tile) made of porous material impregnated with molten carbonate, and a cathode (oxygen electrode) and an anode (fuel electrode). One cell is a cell in which power is generated by the potential difference generated between the cathode and the anode by sandwiching them from both sides, supplying oxidizing gas to the cathode side and supplying fuel gas to the anode side. Cells are stacked in multiple layers with separators interposed in between, and used as a fuel cell stack.

The cathode recycling device that guides oxidizing gas to the cathode of the molten carbonate fuel cell is an effective means for improving the efficiency of the fuel cell power generation system and controlling the temperature of the cell. , in a configuration in which both sides of tile a are sandwiched between cathode b and anode C, oxidizing gas is flowed to the cathode b side, and fuel gas is flowing to the 7 note C side, oxidizing gas is supplied to cathode b. In order to A part of the oxidizing gas discharged from cathode b is guided to the oxidizing gas supply side by high temperature blower g, and is merged with compressed air from the compressor to control the temperature of the air supplied to cathode b. be.

Normally, the temperature inside the fuel cell reaches 650°C to 700'C, so in the conventional method shown in Fig. 2, the temperature of the oxidizing gas is lowered in the heat exchanger f, and then passed through the high-temperature blower 9 to the supply line d.
The temperature of the oxidizing gas entering cathode b is controlled at approximately 550°C.

[Problems to be Solved by the Invention] The above conventional system uses a high temperature blower Q, and the high temperature blower Q compensates for the pressure loss valve of the oxidizing gas within the fuel cell, so it is efficient. However, most high-temperature blowers usually handle gas at around 350°C, and there is no existing high-temperature blower that can input and discharge high-temperature gas at around 700°C, as shown in Figure 2. cannot be put into practical use. For practical use, 700°
A high-temperature blower Q that can handle high-temperature gas near C must be specially manufactured, which may result in an expensive product.

Therefore, the present invention attempts to enable cathode recycling without using an expensive high-temperature blower.

[Means for Solving the Problems] In order to achieve the above object, the present invention incorporates an exhaust gas turbine of an exhaust gas turbine supercharger into an exhaust line for high temperature exhaust gas discharged from the cathode, and A more branched exhaust gas branch line is connected to the inlet side of the compressor of the exhaust gas turbine supercharger, and the discharge side of the compressor is connected to the supply side of the cathode, so that the exhaust gas is recycled to the cathode.

[Operation] Air compressed by the compressor of the exhaust gas turbine supercharger is supplied to the cathode. The high-temperature exhaust gas discharged from the cathode is expanded in an exhaust gas turbine to lower its pressure and temperature. A part of the exhaust gas whose temperature has decreased is mixed with air taken into the compressor from the exhaust gas branch line, compressed and pressurized by the compressor, and then supplied to the cathode. This eliminates the need for conventional high temperature blowers.

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

As shown in FIG. 1, a fuel cell has a cathode 2 and an anode 3 arranged on both sides so as to sandwich a tile 1, and supplies oxidizing gas to the cathode 2 side and supplies fuel gas to the anode 3 side. In a configuration in which one cell of 1 is stacked with a separator in between, in order to supply oxidizing gas to the cathode 2, air A is compressed by a compressor 6, and then is compressed by a heat exchanger 7.
A supply line 9 is provided so that the preheated gas is supplied to the cathode 2, and an exhaust gas turbine supercharger 4 is provided in which the fan wheel of the compressor 6 and the turbine impeller of the exhaust gas turbine 5 are integrally connected by a shaft 8. The exhaust gas turbine 5 in
A heat exchanger 7 is installed in the exhaust line 10 for the oxidizing gas discharged from the cathode 2, and a heat exchanger 7 is installed in the supply line 9 so as to preheat the air. An exhaust gas branch line 11, which is the most characteristic feature of the present invention, is provided in the exhaust line 10 at a position downstream of the heat exchanger 7, and the exhaust gas branch line 11 is connected to the intake side of the compressor 6 of the exhaust gas turbine supercharger. A part of the oxidizing gas discharged from the tank is mixed with air, compressed by a compressor 6, and recycled.

Since all of the oxidizing gas discharged from the cathode 2 of the fuel cell is guided to the exhaust gas turbine 5 in the middle of the exhaust line 10, the energy of the exhaust gas is recovered as power to drive the exhaust gas turbine 5 and rotate the compressor 6. . The high temperature and high pressure oxidizing gas emitted from the cathode 2 is
By being expanded by the exhaust gas turbine 5, the pressure and temperature are lowered, and the exhaust gas is discharged from the exhaust gas turbine 5 and guided to the heat exchanger 7.

In the supply line 9 for supplying the oxidizing gas to the cathode 2, the air compressed by the compressor 6 is led through a heat exchanger 7, in which the compressed air and the exhaust gas exiting from the turbine 5 are connected. Heat exchange is performed with the exhaust gas, and the compressed air is preheated and supplied to the cathode 2.
The exhaust gas is discharged at low temperature and atmospheric pressure, and a part of it is mixed with air on the intake side of the compressor 6, and then compressed and pressurized by the compressor 6 and supplied to the cathode 2 again. At this time, the lower the temperature of the air entering the compressor 6, the higher the efficiency of the compressor 6, but in the present invention, the exhaust waste is kept at a lower temperature and mixed with the air, so the efficiency of the compressor 6 is not lowered.

[Effects of the Invention] As described above, according to the cathode recycling device for a molten carbonate fuel cell of the present invention, all of the oxidizing gas discharged from the cathode is guided to the turbine of the exhaust gas turbine supercharger for power recovery. A part of the low-temperature, atmospheric-pressure gas is introduced into the intake side of the compressor, mixed with air, compressed and pressurized by the compressor, and then supplied to the cathode for recycling, making it less expensive than conventional methods. An excellent effect can be achieved in that cathode recycling can be accelerated using an inexpensive existing exhaust gas turbine supercharger without using a high-temperature blower.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of a cathode recycling device for a molten carbonate fuel cell according to the present invention, and FIG. 2 is a schematic diagram of a conventional system. DESCRIPTION OF SYMBOLS 1... Tile, 2... Cathode, 3... Anode, 4... Exhaust gas turbine supercharger, 5... Exhaust gas turbine, 6... Compressor, 7... Heat exchanger, 9・
... Supply line, 10... Discharge line, 11... Exhaust gas branch line.

Claims (1)

[Claims] 1) Discharge from the cathode in a molten carbonate fuel cell in which a tile impregnated with molten carbonate is sandwiched between a cathode and an anode, and oxidizing gas is supplied to the cathode side and fuel gas is supplied to the anode side. The exhaust gas turbine of the exhaust gas turbine supercharger is installed in the exhaust line of the oxidizing gas, and the exhaust gas branch line branched from the exhaust line position on the downstream side of the exhaust gas turbine is connected to the intake side of the compressor of the exhaust gas turbine supercharger. A cathode recycling device for a molten carbonate fuel cell, characterized in that the device is connected to a molten carbonate fuel cell.