JPH09120830A - Starting method for fuel cell power-generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estatblish a starting method which does not cause deterioration in the characteristics by supplying a fuel gas to a gas passage of a fuel electrode for a certain time, then supplying an oxidator gas to gas passage of an air electrode, and at the same time, connecting the load. SOLUTION: A fuel gas is supplied to a gas passage of a fuel cell, and a certain specified time is allowed to elapse which is longer than the time T(S) in which the fuel gas flows steadily to the gas passages of all element cells. After T(S) elapsed, an oxidator gas is supplied to gas passage of air electrode along with continuous loading so as to start the power generation. Accordingly no load current flows as long as the fuel gas is not in acccess, and no corrosion will be generated on the fuel electrode. Load current flows simultaneously with introduction of the oxidator gas, and the air electrode is prevented from being exposed to a high potential in no-load condition which may cause deterioration of the air electrode catalyst. Thus the intended starting method for fuel cell power-generation device is established, whose characteristics will never be degraded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for starting a fuel cell power generator that introduces an oxidant gas and a fuel gas to generate electricity by an electrochemical reaction, and more particularly to a method for starting power generation.

[0002]

2. Description of the Related Art In a fuel cell power generator, for example, a phosphoric acid fuel cell power generator, a fuel electrode comprising a base material having a fuel gas passage and a fuel electrode catalyst layer and an oxidant gas flow passage. A single cell is formed by contacting both catalyst layers with a base material provided with a passage and an air electrode comprising an air electrode catalyst layer, and sandwiching a matrix impregnated with a phosphoric acid electrolyte to form a single cell. The fuel cell body is formed by stacking layers. When the fuel cell main body configured as described above is heated and the fuel gas having a high hydrogen concentration and the oxidant gas such as air or oxygen are caused to flow through the gas passages of the fuel electrode and the air electrode, respectively, the electrolyte layer is formed. And an electrochemical reaction occurs in both catalyst layers, a DC voltage is generated between both electrodes, and a DC current flows when connected to a load.

FIG. 3 is a characteristic diagram showing an example of a starting method of a fuel cell power generator which has been conventionally used. The fuel flow rate (flow rate of the fuel gas flowing in the gas passage of the fuel electrode), which is a main parameter, When the oxidant flow rate (flow rate of the oxidant gas flowing in the gas passage of the air electrode), load current (current flowing in the connected load) and single cell voltage (voltage generated between both electrodes of each single cell) are started It is a diagram showing the passage of time. As shown in the figure, first, the fuel gas and the oxidant gas were supplied to the gas flow passages of the fuel electrode and the air electrode, and the gas flow passages of all single cells were steadily flowed. After that, a method of connecting to a load, flowing a load current, and starting power generation is adopted.

[0004]

When the starting method as shown in FIG. 3 is used, as shown in the characteristics of the unit cell voltage, the fuel gas and the oxidant gas start to flow constantly and then the load is connected. Until it is carried out, each unit cell is exposed to a potential of about 1 [V] because it is in an unloaded state. On the other hand, the power generation characteristics of the fuel cell power generator are greatly affected by the activity of the air electrode catalyst layer of the fuel cell body, and the platinum fine particles, which are the active component of the air electrode catalyst layer, are rapidly exposed when exposed to a potential of about 1 [V]. As the size of the fuel cell body becomes coarser and the activity of the air electrode catalyst layer decreases, the deterioration of the fuel cell body is accelerated in the above-mentioned no-load state, resulting in deterioration of the characteristics.

Particularly, when the apparatus is frequently started and stopped like an on-site type fuel cell power generator which is installed in a demand area, the characteristics are deteriorated each time the apparatus is started, and as shown in FIG. The voltage will drop. Further, if a method of connecting the load with the start of the flow of the fuel gas and the oxidant gas is adopted as the starting method of the apparatus, the air electrode catalyst layer is not exposed to the potential of about 1 [V] in the unloaded state. Although it disappears, in a single cell where fuel gas has not yet flowed, due to the flow of load current,

[0006]

Embedded image The reaction of C + 2H ₂ O → CO ₂ + 4H ⁺ + 4e ⁻ (1) occurs, and the fuel electrode is corroded and greatly deteriorated. The present invention has been made in consideration of the above-mentioned problems of the prior art, and an object thereof is to prevent the air electrode from being exposed to a high potential at the start of power generation and the characteristics to be deteriorated. It is to provide a starting method that can stably use a fuel cell power generation device for a long period of time without fear of corrosion due to lack of fuel.

[0007]

In order to achieve the above object, in the present invention, a fuel cell body is formed by stacking a plurality of single cells in which an electrolyte layer is sandwiched between an air electrode and a fuel electrode. In a fuel cell power generation device for generating power by passing an oxidant gas through a gas passage provided in an air electrode and a fuel gas through a gas passage provided in a fuel electrode, a gas passage formed in a fuel electrode The time T required to supply the fuel gas and to allow the fuel gas to steadily flow through the gas passages of all the unit cells after the start of the supply.
After a predetermined time t [s] selected longer than [s] elapses, an oxidant gas is supplied to the gas passage of the air electrode, and at the same time, a load is connected to start power generation, so that the fuel cell power generation device can be operated. I will start it.

If the method is started by the above method, the load current does not flow in the state where the fuel gas has not reached, so that the corrosion of the fuel electrode does not occur. Further, since the load current flows at the same time as the introduction of the oxidant gas, there is no possibility that the air electrode is exposed to the high potential in the unloaded state and the air electrode catalyst is deteriorated.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a characteristic diagram showing an embodiment of a method for starting a fuel cell power generator according to the present invention. Like the conventional example of FIG. 3, the main parameters are the fuel flow rate and the oxidant flow rate. FIG. 4 is a diagram showing a lapse of time at the time of starting the load current and the unit cell voltage. As shown in the figure, in this start-up method, first, supply of fuel gas to the fuel cell body was started, and it was confirmed that the fuel gas flowed steadily to the fuel electrodes of all single cells. After the lapse of 5 minutes, the supply of the oxidant gas is started and the load is connected at the same time. At this time, a decrease in the single cell voltage was observed while the oxidant gas did not reach each single cell, and the single cell voltage increased with the arrival of the oxidant gas, and after reaching about 5 minutes, it reached an almost normal value. There is.
When the oxidizing gas is insufficient, on the air electrode side of the single cell,

[0010]

It has been confirmed that the reaction 4H ⁺ + 4e ⁻ → 2H ₂ (2) occurs, but the phenomenon that the characteristics of the single cell deteriorate due to this reaction has not been recognized. FIG. 2 is a characteristic diagram showing a change with time in stack voltage when a stack in which a plurality of unit cells are stacked is repeatedly started by using the above-mentioned starting method.
This figure also shows the characteristics when the conventional starting method of FIG. 3 is used.

As shown in the figure, when the conventional starting method is used, a voltage drop of several mV per unit cell occurs each time the starting is repeated, and the voltage drop progresses progressively. However, in the starting method of the present invention, no voltage drop is recognized. The original voltage is maintained. As described above, if the starting method of FIG. 1 is used, the load current does not flow in the state where the fuel gas is not flowing, so that the corrosion of the fuel electrode does not occur and the air electrode is exposed to the high potential. Since there is no deterioration of the air electrode catalyst layer,
The fuel cell power generator maintains stable characteristics for a long period of time.

[0012]

As described above, according to the present invention, a fuel cell body is formed by stacking a plurality of unit cells each having an electrolyte layer sandwiched between an air electrode and a fuel electrode, and a gas provided in the air electrode. In a fuel cell power generation device for generating power by flowing an oxidant gas in a communication channel and a fuel gas in a gas communication channel provided in a fuel electrode,
When a fuel gas is supplied to the gas flow passage of the fuel electrode, and the fuel gas is constantly supplied to the gas flow passages of all the unit cells after the supply is started, the predetermined time longer than the required time T [s] is selected. After the time t [s] has elapsed, the oxidant gas was supplied to the gas flow path of the air electrode, and at the same time, the load was connected to start power generation, so that the fuel cell power generator was started up. There is no risk of the air electrode being exposed to a high electric potential at times to deteriorate the characteristics, or the fuel electrode being corroded due to lack of fuel gas, and the fuel cell power generator can be used stably for a long period of time. The start-up method can be obtained.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing an embodiment of a starting method of a fuel cell power generator of the present invention, in which a fuel flow rate at start-up, an oxidant flow rate,
Characteristic diagram of time change of load current and single cell voltage

FIG. 2 is a characteristic diagram of a change in stack voltage with time of a single cell stack when a starting operation is repeatedly performed by the starting method of the present invention.

FIG. 3 is a characteristic diagram showing an example of a starting method of a fuel cell power generator that has been used conventionally, and is a time characteristic change diagram of a fuel flow rate, an oxidant flow rate, a load current, and a single cell voltage at the time of startup.

Claims (2)

[Claims] 1. A fuel cell body is formed by stacking a plurality of single cells in which an electrolyte layer is sandwiched between an air electrode and a fuel electrode, and an oxidant gas is supplied to a gas passage provided in the air electrode, and a fuel is also supplied. In a fuel cell power generation device for generating fuel gas by flowing a fuel gas through a gas flow passage provided in an electrode, the fuel gas is supplied to the gas flow passage of the fuel electrode, and after a predetermined time t [s] has passed, the air electrode A method for starting a fuel cell power generator, comprising: supplying an oxidant gas to the gas flow path of 1. and connecting a load at the same time to start power generation. 2. The predetermined time t [s] is selected to be longer than the time T [s] required for the fuel gas to steadily flow through the gas flow passages of all unit cells after the start of supply. The method for starting a fuel cell power generator according to claim 1, wherein