JPS58164161A - Operation stopping method of fuel cell - Google Patents

Abstract

PURPOSE:To eliminate causes for deteriorating cell characteristics by heating a fuel cell when an operation is stopped in the fuel cell which pinches a matrix holding the electrolyte such as phosphoric acid with a fuel electrode and oxidizer electrode. CONSTITUTION:In a fuel gas system, a fuel feed valve 17 is closed to cut off the fuel gas feed, the N2 gas is fed to a gas partition chamber 15 and pipeline system through an N2 gas feed valve 23, and the fuel gas barges in, then the N2 gas is filled under pressure. In an oxidizer gas system, an oxidizer feed valve 20 and oxidizer discharge valve 22 are closed to cut off the feed of the oxidizer gas and an intake of the outer air, a heater 25 is heated, and the oxidizer gas system, particularly a gas partition chamber 16 is heated by means of a circulating valve 13 and circulating fan 24. The heating temperature is kept at a level not lower than the crystal deposition temperature of phosphoric acid being held in a matrix 12. Thereby, the deposition of the electrolyte and cracks or interlayer flaking of a matrix membrane can be prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing crystallization (crystal precipitation) of an electrolyte in a matrix (electrolyte holding member) of a fixed electrolyte fuel cell.

Hydrogen gas t7t uses reformed hydrogen gas obtained by reforming natural sludge such as methane and ethane as fuel gas, and as oxidizer sludge, electrolysis using air [In fixed reservoir fuel cells, the inside of the cell The role of preventing gas leakage, which mainly passes through the matrix from the electrode catalyst surface and reaches the counter electrode, is preferably given to the matrix. This matrix holds an electrolyte such as phosphoric acid under a high gas blowing pressure (0.5~2#/in).
Must have.

A fixed electrolyte fuel cell generally includes the configuration shown in FIG. That is, the fuel cell IFi includes a porous thin film member having heat resistance, corrosion resistance, and electrical insulation properties impregnated with an electrolyte such as phosphoric acid, and a matrix 2 that is separated by the matrix for gas diffusion and electrolyte permeation. A porous fuel electrode C (hydrogen electrode) 3 and an oxidizer electrode (oxygen electrode or air electrode) 4 are in contact with the gas side base material of these electrodes to play the role of current collection and to carry the reactive gas to each electrode. It consists of a gas compartment 5.6 for supplying gas and a separator plate 37.8 forming a gas compartment 5.6.

The electrode is a thin film ([1 water layer) 36.46] in which graphite powder is bonded with polytetrafluoroethylene IPTFE) on a submerged porous carbon nonwoven fabric base material 3a, 4a that facilitates the expansion and/or penetration of scum. PT is a carbon powder catalyst supporting noble metals to facilitate the electrode reaction.
It consists of a thin film (catalyst layers J3c and 4c) bonded by FE.

The matrix 2 is a thin film made by bonding heat-resistant, corrosion-resistant, and non-conductive fine powder with a small amount of PTFE. The matrix is desired to have characteristics such as high humidity due to the eD electrolyte, large electrolyte holding power, high gas bleed pressure in θ, and high mechanical strength in O.

In such fuel cells, when phosphoric acid is used as the electrolyte, the phosphoric acid impregnated into the matrix is generally used at a concentration of 95 to 100 wt1 under normal operating conditions (fi [150 to 200°C). Then, the concentration of phosphoric acid held in the matrix is 300~105w
It becomes t96. By the way, phosphoric acid at the above concentration has an ice crystal temperature as shown in FIG. 2. The vertical axis is m degrees and the horizontal axis is the concentration. In other words, 11jll of phosphorus [100wt rice cake]
The ice crystal m degree is about 42℃, and the ice crystal temperature is about 35℃ at 102wt.
At 105 wt-, the temperature is about 30°C. Such ice crystal temperature 11
When a fuel cell consisting of a matrix holding phosphoric acid at a concentration of The phosphoric acid that is used has a crystallinity below the ice crystal level, and crystallization occurs.
When this phosphoric acid crystal precipitation occurs in a matrix prepared with a small amount of TFE binder-bonded corrugated tube, it causes cracks, delamination, and structural destruction in the matrix film, resulting in a decrease in eD electrolyte retention capacity and 0. Decrease in insulation resistance, decrease in O-Made II box strength, leakage of reactant gas inside the O-cell, and mixed battery l contains Fuel Electric 4K13 and Oxidizer 1.
14 and this, t*ttstt, ts*amu□wa, a, 6ff) + 7 glass 12 gas compartments 15 and 16 for supplying reaction waste to each electrode.
It is composed of In a fuel cell having such a configuration, during operation of the cell, fuel gas is supplied to the gas compartment 15 via the fuel supply pulp 17 and the flow meter 18, and is discharged from the fuel discharge pulp 19. - 10,000, the oxidizing gas is supplied to the gas compartment 16 via the oxidizing agent supply pulp 20 and the flow meter 21, and is supplied to the oxidizing agent discharging pulp 2
It is discharged to 2.

When the operation is stopped, the fuel gas system shuts off the fuel gas supply by closing the fuel supply valve 1, and supplies the nitrogen gas to the waste compartment 15 and the piping. After supplying the fuel to the system and purging the fuel residue, hN
Fill with l gas under pressure. On the other hand, in the oxidizing gas system, the oxidizing agent supply pulp 20 and the oxidizing agent discharge pulp 2
2 is closed to cut off the supply of oxidizing gas and the inflow of outside air, and at the same time, the heater 251'' is heated to heat the circulation pulp 13 and circulation fan 14, the aluminizing gas system, especially the gas compartment 16. This heating source does not allow the phosphoric acid held within the matrix to fall below the crystallization temperature.
[Just keep K. In air-cooled fuel cells.

The circulation fan 24 constantly flows air several times the amount of air required for the reaction, and at the time of starting the fuel cell, a heater is placed in the circulation system to preheat the fuel cell to operation IIItL. Therefore, this type of fuel cell has the advantage of not requiring the above-mentioned special equipment for keeping the phosphoric acid warm.

In the embodiment, heating from the oxidant gas system has been described, but it goes without saying that the battery may be kept warm by heating and circulating nitrogen or gas in the fuel gas system.

Furthermore, as a modification, the fuel cell may be water-cooled or oil-cooled Wt.
t, a heater may be provided here or an existing heater may be used to heat the phosphoric acid to a predetermined temperature or higher while the battery is in rest.

In addition, in some cases, it is also conceivable to maintain the phosphoric acid on the plate by a predetermined degree by heating the entire area around the fuel cell.

Although the examples have been described using phosphoric acid as the electrolyte, the present invention is also applicable to cases where other electrolytes showing similar M times of precipitation are used.

As described above, according to the present invention, precipitation of the electrolyte is prevented by keeping the electrolyte of the fuel cell warm during suspension of operation of the fuel cell, and the electrical equipment of the IJTx membrane is improved.

1 @ Peeling etc. no longer occur, and the electrolyte holding power decreases.
The purpose of 111J vinegar is to eliminate the causes of a decrease in battery performance due to a decrease in insulation resistance, a decrease in IJTx strength, or leakage and mixing of reaction scum inside the battery.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of essential parts of a fuel cell to which the present invention can be applied!
FIG. 2 is an ice crystal temperature characteristic diagram of phosphoric acid, and FIG. 3 is a fluid circuit diagram of an embodiment of the present invention. IQ-...Fuel cell, 12...Matrix, 1
5.16...Gas section 1iii room, 24...M-term fan, 25...Heater O 1 M year old 2 mouth'C%H3Fθ4 f3

Claims (1)

[Claims] ]) In a fuel cell formed by sandwiching an oxidizer electrode and a matrix fuel electrode holding an electrolyte such as phosphoric acid,
A method for suspending operation of a fuel cell, which comprises keeping the fuel cell at a temperature higher than the temperature at which an electrolyte crystallizes during suspension of operation. 2) Percentage Claim II] In the method described in Jjl. 1. A method for suspending operation of a fuel cell, which comprises heating a heater in an oxidizer supply system of the fuel cell to keep a matrix warm from the oxidizer compartment side of the fuel cell when the operation is suspended.