JPS5927474A - Fuel cell - Google Patents

Abstract

PURPOSE:To maintain pressure difference between the exhaust gases of fuel and an oxidant at within a given range by introducing them into an oxidizing catalyst tower, being followed by discharging part of the gases into the air and returning most part of the gases to the catalyst tower by means of a blower after moisture is separated from the gases by means of a cooling device. CONSTITUTION:Fuel gas is supplied into the fuel chamber 3 of a fuel cell 11, while oxidant gas is supplied into the oxidant chamber 3a of the fuel cell 1. The exhaust gas holes 6 and 6a of the fuel chamber 3 and the oxidant chamber 3a, are connected to the inlet part 32-1 of an oxidizing catalyst tower 32. The outlet part 32-2 of the catalyst tower 32 is connected to a control valve 35 which is regulated with a pressure gage 34. It is also connected to a cooling device 33, so that exhaust gas the moisture of which is removed is circulated by being fed back to the inlet 32-1 of the catalyst tower 32 through a recycle blower 36. As a result, the gas pressure of the cell 11 can be maintained at a given level, and pressure difference between the two systems can be eliminated by introducing both exhaust gases into areas with the same pressure. Consequently, stable operation of the fuel cell can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fuel cell with an improved gas supply and exhaust gas treatment device.

[Technical background of the invention and its problems]

A fuel cell (hereinafter abbreviated as battery) is a device that directly converts the energy contained in fuel into electrical energy.

Batteries usually have a pair of porous electrodes sandwiching an electrolyte, and a fuel gas such as hydrogen is brought into contact with the back of one electrode, and an oxidizing gas such as oxygen is brought into contact with the back of the other electrode. contact. The structure is such that electrical energy is extracted from between the two electrodes by utilizing the electrochemical reaction that occurs at this time.

Molten salts, alkaline solutions, acid baths, etc. are used as electrolytes, but the principle of a typical battery using cynic acid as an electrolyte will be explained. In FIG. 1, the electrolyte layer (1) is a fibrous sheet or mineral powder impregnated with phosphoric acid. An anode electrode (2) and a canned electrode (2a) are provided on both sides of this electrolyte layer (1). Both these electrodes (2+, (
2a) is formed from a porous member made of a carbonaceous member. In addition, a platinum catalyst is usually coated on the electrolyte layer (11 side) of these two electrodes (2J, (2a)). On the opposite side, a fuel gas chamber (3) through which the fuel gas flows and an oxidizing gas chamber (3a) through which the oxidizing gas flows are provided.In general, in a phosphoric acid fuel cell, the fuel gas is hydrogen gas; Further, the oxidant gas is air.

The operation of such a phosphoric acid battery will be explained. Hydrogen gas in the gas that has flowed into the fuel gas chamber (3) diffuses into the cavity of the porous anode electrode (2) and reaches the catalyst. Then, the hydrogen gas is dissociated into hydrogen ions and electrons by the action of the catalyst.

That is, the reaction formula U H2→2H+2e can be obtained.

Next, this hydrogen ion H+ enters the electrolyte layer (1) and migrates toward the canned electrode (2a) due to concentration diffusion. - Ten thousand electrons e flow into the anode electrode (2), and this anode electrode (2+ is charged with negative V). In addition, in the cande electrode (2a), the hydrogen ions H+ migrating from the anode electrode (2), Oxygen 02 in the air that has flowed into the oxidant gas chamber (3a) is transferred to the porous canned electrode (2).
Diffusion into the void in a). This diffused oxygen 0° and
The following reaction occurs on the surface of the catalyst between the acid ions e that have returned to the battery from the anode electrode (2) through the external electrical load and the hydrogen ions H+.

In other words, 4H"+4e +02-+ 2) (20) Thus, the reaction in which hydrogen is oxidized to water, and the chemical energy at this time becomes electrical energy, serves as a battery that provides electrical energy under an external electrical load. The entire reaction is completed.

At this time, part of the electrical energy is consumed in the electrolyte layer (1) as internal resistance of the battery. Therefore, in order to increase the efficiency of the battery, the electrolyte layer (11) is designed to be extremely thin and formed to shorten the migration distance of hydrogen ions and reduce resistance.

Further, hydrogen gas and air supplied as raw materials are usually pressurized to several atmospheres. As with general chemical reactions, this is done to increase the concentration of substances involved in the reaction as an effective means of increasing the reaction rate.

The problem when actually supplying gas to batteries is that unless direct contact or mixing of hydrogen and oxygen is prevented, 1c-
) I'm sorry for not having it. As can be seen in Figure 1, the electrolyte layer (1) separates the fuel gas and oxidant gas.
Only. The electrolyte layer (11, as mentioned above, is a fibrous sheet or mineral powder impregnated with phosphoric acid, and the surface tension of the phosphoric acid prevents the mixing of both gases, and the thickness is 0.
．． It is extremely thin, approximately 1 mm. Therefore, to operate the battery safely, both gases must be supplied at equal pressures. However, even when the supply gas flow fluctuates due to load fluctuations and when starting and stopping, the differential pressure between the two gases must be controlled to an extremely small difference of several tens of millimeters or less in the water column.

The gas supply method in an actual fuel cell power plant is described in Japanese Patent Application Laid-open No. 54-82636 and 51-10454.
No. 1.

It is already known in No. 51-104540, No. 5N-104539, etc. The fuel used is petroleum fuel or alcohol, which is reformed into hydrogen using a reformer. The heat source for the reformer is the exhaust gas from batteries, and the exhaust gas is supplied to a turbo compressor to pressurize the air. Technologies such as supplying it as an oxidizing agent for batteries have been put into practical use.

Instead of using a complicated gas supply system in a practical plant, battery test equipment is usually supplied from a fuel cylinder and air is supplied from a compressor. In addition, in a practical battery, the electrode area is large and the electrodes are laminated in multiple layers via an interconnector, but since the pressure control of both gases is the same, the illustration of the practical battery will be omitted and the principle diagram will be shown. use

Next, FIG. 2 shows an example of a flow diagram of hydrogen gas and oxygen gas in a conventional battery. The fuel gas supply side of the battery←1) is connected to the fuel gas cylinder α through the fuel gas supply pipe (1 First, connect the flow meter ae and the interlocked flow rate adjustment valve α.The air supply side is connected to the air compressor marked 0 via the air supply pipe (11).Then, connect the air compressor side to the pressure reducing valve (15).
1L), a flow rate controller (1L) linked to a flowmeter (16a)
7m).

On the other hand, a fuel exhaust gas pipe (Company) is connected to the fuel exhaust gas side of battery α1), and an air exhaust gas pipe (2) is connected to the air exhaust gas side.
I) is connected. Pressure regulating valves (22a) are connected to the fuel exhaust gas pipe (2o) and the air exhaust gas pipe Cυ, respectively. The pressure regulating valve (21A) is adjusted by the pressure gauge (2 East) that measures the pressure of the fuel exhaust gas of the U battery (11). Pressure gauge (2) to detect pressure difference
51 to keep the pressure difference within an allowable value.

However, while the pressure regulating valve Q3 (22a) bears the pressure before and after it, it reduces the pressure difference between the fuel exhaust gas side and the air exhaust gas side to less than a pressure difference of 20 mm to 30 mm of water column, which corresponds to about i/zooo of that pressure. The problem has often been that it is very difficult to constantly adjust and maintain the pressure.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and has the seventh purpose of constantly maintaining the pressure difference between the fuel exhaust gas side and the air exhaust gas side within a selected minute pressure difference value. The goal is to provide fuel cells that can

[Summary of the invention]

The present invention introduces fuel exhaust gas and oxidizer exhaust gas into an oxidation catalyst tower to generate a mixed gas, and releases a portion of this mixed gas to the atmosphere through a pressure regulating valve regulated by a pressure gauge. By separating the moisture from a portion of the mixed exhaust gas through a cooling device and returning the mixed exhaust gas from which moisture has been removed to the oxidation catalyst tower via a recycling blower, the pressure difference between the fuel exhaust gas and oxidizer exhaust gas is reduced. Its feature is that the fuel cell can continue to operate stably.

It is optimal to adjust the hydrogen concentration of the mixed exhaust gas to less than 2%.

[Embodiments of the invention]

Hereinafter, referring to the drawings, an embodiment of the fuel cell of the present invention will be described in which porous electrodes (2) and (2a) are disposed on both sides of (1).

Furthermore, a fuel gas chamber (3) and an oxidant gas chamber (3a) are formed on the back surfaces of both electrodes (2) and (2a), respectively. Fuel gas 'M (alo) On the fuel gas supply port (5) side, from A21 to the fuel cylinder via the fuel gas supply pipe (13),
Pressure reducing valve α clause, flow rate regulating valve regulated by flow meter shout (
17) Connect.

In addition, the oxidant gas (hereinafter referred to as air) supply port (5a) of the oxidant gas chamber (3&) is connected to an air compressor, an air supply pipe QS, a pressure reducing valve (l s a ), a flow meter (
Connect a flow control valve (17m) regulated by 16a).

Fully open the fuel exhaust gas connected to the fuel exhaust gas port (6) of the fuel gas chamber (3) and oxidize the air exhaust gas pipe 6υ connected to the air exhaust gas port (6a) of the oxidizer gas chamber (3a) at once. Connected to one inlet port (32-1) of the catalyst tower.

In addition, a cooling device (2) is connected to the outlet (32-2) of the oxidation catalyst tower (321), and a pressure regulating valve (to) that is adjusted by a pressure gauge (b) is installed.Cooling device Connect the cycle blower (g) to the other side of (c),
This recycle blower (via 361, oxidation catalyst tower 62
It is connected to the inlet port (32-1) of No.1. Cooling device i (to) is a cooler (33-1) and a drain valve (33-2)
A drain (33-3) is provided. As described above, exhaust gas treatment devices are configured in the fuel exhaust gas system and the oxidizer exhaust gas system.

Next, the effects of the present invention will be explained. The fuel exhaust gas containing unreacted hydrogen from the fuel gas chamber (3) of the battery 01) flows through the fuel exhaust gas pipe 13Ie, where it joins with the recycle gas from the recycle blower, and also flows through the air exhaust gas pipe OI.
The air exhaust gas passes through J and flows into the oxidation catalyst tower C12+. Inside this oxidation catalyst tower (32I), unreacted hydrogen gas combines with unreacted oxygen to produce water.

A part of the mixed exhaust gas containing moisture is transferred to the oxidation catalyst tower 62.
1 to pressure regulating valve C3 regulated by pressure gauge (2)
51 to the atmosphere. On the other hand, most of the mixed exhaust gas is separated from the water cooled by the cooler (33-1) inside the cooling device (c), and the water collected in the drain (33-3) is collected by the drain valve (33-2). is discharged from.

Further, the mixed exhaust gas inside the cooling device (to) is returned to the oxidation catalyst towers 6 again by the recycle blower to circulate the mixed exhaust gas.

The air volume of the mixed exhaust gas thus circulated by the recycle blower-cfi+ is adjusted so that the hydrogen concentration when mixed with the hydrogen exhaust gas is 2% or less. This is because while the explosive limit of hydrogen gas is 4°C, there is no risk of explosion if it is 2%, and the temperature rise due to the heat generated by oxidation can be suppressed to about 200°C. Ruru. In this way, safe operation can be continued without the mixed exhaust gas reaching the explosive limit and without generating high temperatures that would degrade the catalyst.

Furthermore, since the recycle blower (support) j only has to bear the pressure drop of the recycle circuit, only a small amount of power is wasted. The pressure regulating valve group 0 is automatically regulated by the pressure gauge 4), and the gas pressure of the battery ←υ can be maintained at a desired value. In this way, the gas pressures of the fuel gas and oxidant gas of battery 01) can be connected to a place with the same pressure using pipes where the pressure drop can be practically ignored, so there is no pressure difference between the two exhaust gas systems. This also reduces the need for controls to reduce the pressure difference between the two exhaust gas systems. In addition,
Of course, such exhaust gas treatment can be applied to actual power plants.

〔Effect of the invention〕

As explained above, according to the present invention, the fuel exhaust gas and the oxidizer exhaust gas are introduced into the oxidation catalyst tower, and the mixed exhaust gas is circulated from the oxidation catalyst tower to the oxidation catalyst tower via the recycle blower. Mixed exhaust gas hydrogen gas a
By keeping the temperature below 2 degrees, it is possible to suppress explosions and temperature rises, reduce the pressure difference between both exhaust gases, and provide a fuel cell that can continue stable operation for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the principle of a phosphoric acid fuel cell. FIG. 2 is a flow diagram of a conventional fuel cell, and FIG. 3 is a diagram 70 of the fuel cell of the present invention. View (1)...Electrolytic layer (21, (2a)...
・Electrode (3)...Fuel gas chamber (3a)...
Oxidizer gas chamber (g)...Fuel exhaust gas pipe 6υ・
... Air exhaust gas pipe 621 ... Oxidation catalyst tower C33
...Cooling device (foundation) ---Pressure gauge (3 pieces)
...Pressure control valve μs) ...Recycle blower Agent Patent attorney Inoue - Male

Claims (2)

[Claims] (1) Electricity generated by arranging a pair of porous electrodes with an electrolyte layer in between, and bringing fuel gas into contact with the back surface of one electrode and oxidizing gas into contact with the back surface of the other electrode. In a system that extracts electrical energy generated between the two electrodes from a chemical reaction, fuel exhaust gas and oxidizer exhaust gas are introduced into the oxidation catalyst tower, and a portion is released to the atmosphere through a pressure control valve. , the exhaust gas is treated in such a way that moisture is separated from most of the mixed exhaust gas through a cooling device, and the mixed exhaust gas from which moisture is removed is returned to the oxidation catalyst tower and circulated through a recycling blower. Fuel cell. (2) The fuel cell according to claim 1, wherein the hydrogen concentration of the mixed exhaust gas is adjusted to 2% or less.