JPS59209279A - Molten salt fuel cell - Google Patents

Abstract

PURPOSE:To keep an atmosphere of a gas chamber dry with a moisture absorber when a cell is stopped and regenerating the absorber with heat generated in the cell by arranging a dryer containing moisture absorber and a fuel cell main body in a sealable container. CONSTITUTION:A fuel cell main body 2 and a dryer 4 containing moisture absorber 3 are arranged in a sealable and pressure resistant container 1. Temperature of a fuel cell 2 is raised with a supporting power source 22, and power generation is initiated at 500-650 deg.C by combining with heat generation of the fuel cell 2. When power generation is stopped, each of valves 13, 14, 18, 19, and 24 is directly closed, or after replacing hydrogen gas with an inactive gas, each of valves is closed. When temperature in a container falls near room temperature, moisture contained in air in the container is absorbed in the moisture absorber 3 in the dryer, and moisture in the container is decreased with time elapsed. The moisture absorbed in the absorber is exhaust from an exhausting pipe 23 with heat in power generation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high-temperature operating fuel cell device using hydrogen, carbon oxide, etc. as a fuel, oxygen, air, carbon dioxide, etc. as an oxidizing agent, and a molten salt as an electrolyte. .

High-temperature operating fuel cell devices are designed to obtain high current densities by taking advantage of the high rate of chemical reactions at high temperatures.

Conventional Structures and Problems Generally, high-temperature operating fuel cells use, as an electrolyte, a molten salt that allows ion movement even at high temperatures, such as a carbonate having CO&- conductivity. Using hydrogen as a fuel and a mixture of oxygen and carbon dioxide in the air as an oxidizing agent, a molten salt fuel cell is constructed in which an external reaction is carried out as described below.

As is clear from the above reaction equation, hydrogen reacts with co&- of the electrolyte and is consumed on the fuel electrode side, producing water and carbon dioxide as reaction products. On the other hand, on the oxidizing agent electrode side (hereinafter referred to as the air electrode side), oxygen and carbon dioxide gas are consumed in the form of CO wind to the electrolyte. Here, the carbon dioxide gas generated at the fuel electrode is supplied to the air electrode and consumed, so the overall reaction is H2+
! AO2→H20, and water is generated from hydrogen and oxygen. Page 3 in the electrolyte is only the movement of CO3 ions, and carbon dioxide gas is largely involved in the mass balance. Therefore, it is important that the electrolyte containing Co3 does not change during normal power generation or when the grinding is stopped.

This type of fuel cell uses molten salt as an electrolyte, and a holder containing this electrolyte is sandwiched between an air electrode and a fuel electrode from both sides.
A mixed gas of carbon dioxide and air is supplied to the gas chamber on the air electrode side, and hydrogen is supplied to the gas chamber on the fuel electrode side. Further, a current collector is provided in each gas chamber to facilitate the collection of electricity between the two electrodes. On the other hand, a flow path is provided in which the supplied mixture of air and carbon dioxide undergoes an electrochemical reaction and is discharged outside the system, and in the same way, hydrogen is discharged as carbon dioxide and water. Moreover, when generating electricity at a pressure close to normal pressure, a special high-pressure vessel is not required.

One attempt to improve performance is to place the fuel cell body inside a high-pressure container and generate electricity in a somewhat high-pressure atmosphere.

With this configuration, when power is generated at a high temperature, even if there is moisture in the fuel supplied from outside or in the air, the temperature will be high during power generation, so it will be discharged as water vapor and will react with the electrolyte. However, the power generation of the fuel cell may be stopped for reasons such as maintenance, and this operation is necessary from a practical management perspective. At this time, if the temperature of the fuel cell is regenerated and raised before the temperature of the fuel cell drops to near room temperature, there will be no major effect, but if the fuel cell is opened and stopped for a relatively long time, the temperature will naturally drop from room temperature 1. When the temperature of the fuel cell drops, the air around the fuel cell itself, and the water still contained in the replacement gas (inert gas), reacts with the electrolyte, causing the electrolyte (especially carbonate) to deliquesce. It arouses, transforms, and destroys. The deliquescent electrolyte becomes dissolved and partially creeps from the electrolyte holder and leaks to the outside of the battery, causing a short circuit phenomenon.Furthermore, the electrolyte decreases and the electrical resistance of the electrolyte holder increases. There were problems that led to a decline in battery performance.

Purpose of the Invention Page 5 In view of the above-mentioned problems, the present invention uses a moisture adsorbent to maintain a dry gas atmosphere when stopping power generation in a high-temperature operation type molten salt fuel cell device that uses carbonate as an electrolyte. Another object of the present invention is to regenerate the moisture adsorbent using heat generated by the fuel cell.

Structure of the Invention The present invention uses reducing gas (H2, Co, etc.) as fuel,
A molten salt fuel cell that generates electricity using oxidizing gas (O2, Co2, air, etc.) as an oxidant and a dryer containing a moisture adsorbent are placed in a common sealable container, and the molten salt fuel cell generates electricity. When power generation is stopped, the water absorbent absorbs and removes water inside the gas chamber of the fuel cell and the container, and when power generation is restarted, the water adsorbent is regenerated using the heat generated by the fuel cell or from an auxiliary heat source. This is a molten salt fuel cell device characterized by: Furthermore, the present invention uses an inert gas for displacement through inorganic porous materials such as zeolite, alumina, molecular sheep, chlorides and oxides such as Ca and Mq as a moisture adsorbent. Battery gas chamber, manifold (
This is a molten salt fuel cell device characterized in that a dryer is provided in a container so as to supply a common gas chamber (gas chamber) of a stacked battery.

Description of examples Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

The molten salt fuel cell device of the present invention is shown in FIGS. 1 and 2. The difference from the conventional type is that the dryer with a built-in moisture adsorbent and the fuel cell body are placed in a sealable container so that dry gas can be supplied when power generation is stopped.
The device is configured to regenerate the moisture adsorbent using an auxiliary heat source. In other words, the fuel cell can generate electricity and the adsorbent can be regenerated at the same time.

That is, as shown in FIG. 1, which shows an embodiment when power generation is stopped, the basic structure consists of a fuel cell main body 2 and a dryer 4 containing a moisture adsorbent 3 in a sealable pressure-resistant container 1. The fuel cell main body 2 has an air chamber 7 having an air electrode 6 on both sides with an electrolyte holder 5 in between, and a fuel chamber 9 having a fuel electrode 8.

-22 On the air chamber 7 side, an inlet pipe 10 for supplying an oxidizing agent and a discharge pipe 11 are connected through a joint 12. 1
Numerals 3 and 14 are valves on the inlet side and the outlet side, which are used to supply and stop the oxidizing gas. The fuel chamber side 9 has an inlet pipe 15 for supplying fuel and an exhaust pipe 16.
are connected through a joint 17. Numerals 18 and 19 are valves on the inlet side and the outlet side, which perform the fuel gas supply and stop E operation. The entire device can be tightened to the bottom plate 20 with bolts 21 to seal the inside of the container.

The temperature of the fuel cell is raised using the Ushizu auxiliary power supply heater 22, etc., and the temperature reaches 50%, including the amount of heat generated by the fuel cell itself.
Power was generated at 0 to 660°C. In exothermic conditions, the oxidant supply/discharge pulps 13, 14 and the joint 12 are open.

Similarly, fuel supply/discharge valves 18 and 19 and joint 17
is also open.

The valve 24 of the exhaust gas outlet 23 inside the container is kept open in order to discharge the gas containing moisture inside.

When power generation is stopped, directly close the pot valve 13, 14゜18.
．． 19.24) or replace each valve (13, 14° 1B, 19.
24) Close. When the temperature inside the container drops to near room temperature, the moisture contained in the air inside the container is absorbed and removed by the moisture adsorbent 3 in the dryer. As time passes, there is almost no moisture in the container, resulting in a dry atmosphere.

The moisture absorbed by the moisture adsorbent 3 is regenerated by discharging the moisture from the discharge outlet 23 with the heat of the temperature (500 to 66° C.) during power generation of the fuel cell.

A perforated plate 4' having a plurality of holes was provided on the fuel cell frame 25 and a part of the dryer in order to facilitate ventilation for absorption and release of moisture.

Further, the next embodiment is shown in FIG. A dryer 30.31 containing a fuel cell main body 27 and a moisture adsorbent 28.29 made of an inorganic porous material is arranged in a sealable pressure-resistant container 26,
The flow of gas from the valve 32 that supplies the oxidizing agent to the air chamber of the fuel cell is divided into two directions: one is the valve 33 for gas supply during fuel cell power generation, and the other is for drying when the fuel cell power generation is stopped. Drying gas (air, inert gas) piping is provided through the dryer 3° with a valve 34 for supplying 5 NO gas to the fuel cell. 36 is a valve for exhaust gas.

Similarly, the gas flow from the valve 36 that supplies hydrogen to the fuel gas chamber is divided into two directions: one is the gas supply valve 37 during fuel cell power generation, and the other is the dry gas (displacement) valve 37 when fuel cell power generation is stopped. Valve 3 that supplies gas) to the fuel cell
At 8, dry gas piping is provided through the dryer 31. 39 is a valve for exhaust gas. During fuel cell power generation, if the amount of heat is insufficient, or as a starting heat source, use the auxiliary power heater 4.
Use ゜. When regenerating the water adsorbent, the amount of heat generated by the fuel cell is used, and the water released from the adsorbent is discharged by opening the discharge pulps 41 and 42.

In this way, when the moisture inside the fuel cell is removed and the fuel cell becomes almost completely dry, each valve is closed and maintained.

The molten salt fuel cell itself was prototyped using a known method.

The air electrode is a sintered body of a nickel composite oxide containing lithium, the fuel electrode is a sintered porous body of nickel, and the electrolyte is a mixture of 60 wt% potassium carbonate and 40 wt% lithium aluminate powder. % and hot pressed at a temperature of 1500°C.

Approximately 300 to 500 g of zeolite was used as the inorganic porous material per 100 W of the fuel cell. First, hydrogen gas as a fuel and air containing carbon dioxide gas as an oxidizing agent were supplied in an amount several times the theoretical amount, and the operating temperature was 650°C and the current density was 100mA/7.
After generating power for 00 hours, power generation was stopped, the temperature was lowered in a room-temperature trench, and after being left for about 5 and 10 days, the performance was examined when power was generated again at the predetermined temperature and current density. The following table shows the performance of conventional example A which does not use a dryer, first embodiment B of the present invention in which moisture is removed from the container, and second embodiment C of the present invention in which moisture is removed from the battery gas chamber. .

table The degree of decrease compared to the initial performance is expressed as a percentage.

111・-As is clear from the table, the conventional type has a temperature of 30 to 4 after being left for 6 days.
0%, the performance decreases by 6091+ or more when left for 10 days, whereas in the embodiment of the present invention, although there are some differences between A and B, the performance decrease is only a few, and compared to the conventional type. te1
This is a performance improvement of more than 0 times. If Examples A and B are used extensively, further improvement in performance can be expected.

In conventional examples, the electrolyte in the electrolyte holder absorbs moisture in the gas, causing deliquescence and some leaking to the outside.
This is thought to be due to an increase in resistance due to alteration of the electrolyte. This phenomenon has been confirmed through experiments.

Effects of the Invention As described above, according to the present invention, the molten salt fuel cell device has almost no deterioration in performance even when power generation is stopped due to maintenance, maintains stable performance, and has a long service life. can. Moreover, the fuel cell can generate electricity and regenerate the adsorbent at the same time.

[Brief explanation of the drawing]

Figure 1 shows a molten salt fuel cell manufactured by Japanese Patent Application Laid-Open No. 5-1-2010, which is an embodiment of the present invention.
9-209279 (4) Fig. 2 is a block diagram of a molten salt fuel cell device according to a second embodiment of the present invention. 1...Pressure container, 2...Battery body, 3
...Moisture adsorbent, 4...Dryer, 6.
... Electrolyte holding body, 7 ... Air chamber, 9.
... Fuel chamber, 10 ... Inlet side pipe for oxidizing agent supply, 15 ... Inlet side pipe for fuel supply,
22...Heater for auxiliary power supply, 2S...
Frame, 4'...Perforated plate.

Claims (1)

[Scope of Claims] A molten salt fuel cell main body that generates electricity using a reducing gas as a fuel and an oxidizing gas as an oxidizing agent and a dryer containing a moisture adsorbent are arranged in a common sealable container, When power generation of the molten salt fuel cell is stopped, the moisture adsorbent absorbs and removes moisture inside the gas chamber and the container of the fuel cell, and when power generation is restarted, the fuel cell generates heat and heat resistance due to the auxiliary heat source is eliminated. A molten fuel cell device characterized in that it regenerates a moisture adsorbent in quantity.