JP2021128867A - Fuel cell system - Google Patents

Abstract

To provide a fuel cell system in which the amount of ions that are electrolyte membrane deterioration components can be accurately grasped, so that the life of an electrolyte membrane of a fuel cell can be more accurately predicted.SOLUTION: A fuel cell life prediction system includes a fuel cell, a membrane deterioration diagnostic cell having a membrane electrode assembly, an ion amount measurement device, and the like. In the fuel cell life prediction system, the life of an electrolyte membrane is estimated by comparing the amount of accumulated ions of the membrane deterioration diagnostic cell with a data group that shows the correlation between the amount of accumulated ions measured in advance and the life of an electrolyte membrane.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a fuel cell system.

In a solid polymer fuel cell, electric energy is generated by supplying an oxidant gas containing oxygen and a fuel gas containing hydrogen to a fuel cell stack in which a plurality of cells are stacked and causing a chemical reaction. The cell, which is the basic unit, is generally provided with MEA (Membrane Electrode Assembly: Membrane Electrode Assembly) in which electrode catalyst layers are formed on both sides of a solid polymer electrolyte membrane, a diffusion layer on the outside thereof, and a gas flow path on the outside thereof. And a gas separator is arranged.
At the fuel electrode (anode), hydrogen supplied from the flow path / diffusion layer is protonated by the catalytic action of the catalyst layer, passes through the electrolyte membrane, and moves to the oxidant electrode (cathode). The electrons generated at the same time work through an external circuit and move to the cathode. Oxygen supplied to the cathode reacts with protons and electrons on the cathode to produce water.
The generated water gives an appropriate humidity to the electrolyte membrane, and the excess water permeates the diffusion layer and is discharged to the outside of the system through the flow path.

When the polymer electrolyte fuel cell is continuously operated for a long period of time, the electrolyte membrane deteriorates and there is a possibility that pores are opened, and a cross leak of hydrogen and oxygen occurs in a single cell with pores. In the polymer electrolyte fuel cell, it is important to accurately detect the deterioration state of the electrolyte membrane because the cross leak of each single cell has a great influence on the performance and life of the polymer electrolyte fuel cell. ..

Various studies have been conducted to improve the power generation performance of fuel cells.
For example, in Patent Document 1, an ion concentration detector is provided in an anode to which hydrogen is supplied, an anode of a fuel cell having a cathode to which air is supplied, a hydrogen discharge path downstream of the cathode, and an air discharge path, and ion concentration is provided. A technique for detecting the deteriorated state of the electrolyte membrane based on the ion concentration (pH) detected by the detector is disclosed.

Further, Patent Document 2 provides a measuring means for measuring the amount of fluoride ions in a fuel cell emission substance to which a fuel gas and an oxidant gas containing oxygen are supplied and generate electric power by an electrochemical reaction, and the measurement thereof. A technique is disclosed that includes a life prediction means for predicting the life of a fuel cell by using the obtained amount of fluoride ions.

Japanese Unexamined Patent Publication No. 2006-049146 Japanese Unexamined Patent Publication No. 2005-174922

In the above-mentioned conventional technique, the sulfate ion concentration of the electrolyte membrane deterioration component is detected by an ion concentration detecting means provided downstream of the fuel cell. However, since sulfate ions are accumulated in the cell and the electrolyte membrane, the entire amount of sulfate ions does not come out to the downstream discharge path. In addition, since the amount of water varies depending on the amount of power generation, when the amount of water is large, a higher pH is detected downstream of the fuel cell than in the vicinity of the electrolyte membrane, and the amount of deterioration is underestimated. There is a problem that the life may not be predicted.

The present disclosure has been made in view of the above circumstances, and since the amount of ions, which are electrolyte membrane deterioration components, can be accurately grasped, a fuel cell system capable of more accurately predicting the life of the electrolyte membrane of the fuel cell. The main purpose is to provide.

In the present disclosure, a fuel having at least a membrane electrode assembly having an oxidant electrode catalyst layer, a fuel electrode catalyst layer, and an electrolyte film arranged between the oxidant electrode catalyst layer and the fuel electrode catalyst layer. With batteries
An oxidant gas supply unit that supplies the oxidant gas to the fuel cell,
A fuel gas supply unit that supplies fuel gas to the fuel cell and
A cooling water supply unit that supplies cooling water to the fuel cell,
A cooling water discharge unit that discharges the cooling water from the fuel cell,
A membrane deterioration diagnostic cell having the membrane electrode assembly and
An oxidant gas flow path for a membrane deterioration diagnosis cell in which the oxidant gas flows from the oxidant gas supply unit into the membrane deterioration diagnosis cell,
A fuel gas flow path for a membrane deterioration diagnosis cell in which the fuel gas flows from the fuel gas supply unit into the membrane deterioration diagnosis cell, and a fuel gas flow path for the membrane deterioration diagnosis cell.
Ion amount measuring device and
With a control unit
The membrane deterioration diagnosis cell is brought into contact with the fuel cell at the cooling water outlet of the cooling water discharge portion of the fuel cell.
The membrane deterioration diagnosis cell further has a cooling water flow path for the membrane deterioration diagnosis cell connected from the cooling water outlet of the fuel cell inside the membrane deterioration diagnosis cell.
The two gas flow paths of the oxidant gas flow path for the membrane deterioration diagnosis cell and the fuel gas flow path for the membrane deterioration diagnosis cell are connected to the cooling water flow path for the membrane deterioration diagnosis cell upstream of the gas flow path. Has a switching valve
The control unit flows gas through the gas flow path during normal operation of the fuel cell, switches the valve by the switching valve at the time of diagnosing deterioration of the electrolyte membrane of the fuel cell, and cools water in the gas flow path. Shed,
The control unit measures the amount of ions in the cooling water discharged from the membrane deterioration diagnosis cell by the ion amount measuring device at predetermined time intervals from the start of the deterioration diagnosis of the electrolyte membrane, and calculates the accumulated ion amount. death,
The control unit estimates the life of the electrolyte membrane by comparing the calculated amount of stored ions with a data group showing the correlation between the amount of stored ions measured in advance and the life of the electrolyte membrane. Provides a fuel cell system.

The present disclosure can provide a fuel cell system capable of predicting the life of an electrolyte membrane of a fuel cell with higher accuracy because the amount of ions, which is an electrolyte membrane deterioration component, can be accurately grasped.

It is a schematic block diagram which shows a part of an example of the fuel cell system of this disclosure. It is a figure which shows an example of the relationship between the amount of sulfate ion and the life of an electrolyte membrane. It is a flowchart which shows an example of the control executed by the control part used in this disclosure.

In the present disclosure, a fuel having at least a membrane electrode assembly having an oxidant electrode catalyst layer, a fuel electrode catalyst layer, and an electrolyte film arranged between the oxidant electrode catalyst layer and the fuel electrode catalyst layer. With batteries
An oxidant gas supply unit that supplies the oxidant gas to the fuel cell,
A fuel gas supply unit that supplies fuel gas to the fuel cell and
A cooling water supply unit that supplies cooling water to the fuel cell,
A cooling water discharge unit that discharges the cooling water from the fuel cell,
A membrane deterioration diagnostic cell having the membrane electrode assembly and
An oxidant gas flow path for a membrane deterioration diagnosis cell in which the oxidant gas flows from the oxidant gas supply unit into the membrane deterioration diagnosis cell,
A fuel gas flow path for a membrane deterioration diagnosis cell in which the fuel gas flows from the fuel gas supply unit into the membrane deterioration diagnosis cell, and a fuel gas flow path for the membrane deterioration diagnosis cell.
Ion amount measuring device and
With a control unit
The membrane deterioration diagnosis cell is brought into contact with the fuel cell at the cooling water outlet of the cooling water discharge portion of the fuel cell.
The membrane deterioration diagnosis cell further has a cooling water flow path for the membrane deterioration diagnosis cell connected from the cooling water outlet of the fuel cell inside the membrane deterioration diagnosis cell.
The two gas flow paths of the oxidant gas flow path for the membrane deterioration diagnosis cell and the fuel gas flow path for the membrane deterioration diagnosis cell are connected to the cooling water flow path for the membrane deterioration diagnosis cell upstream of the gas flow path. Has a switching valve
The control unit flows gas through the gas flow path during normal operation of the fuel cell, switches the valve by the switching valve at the time of diagnosing deterioration of the electrolyte membrane of the fuel cell, and cools water in the gas flow path. Shed,
The control unit measures the amount of ions in the cooling water discharged from the membrane deterioration diagnosis cell by the ion amount measuring device at predetermined time intervals from the start of the deterioration diagnosis of the electrolyte membrane, and calculates the accumulated ion amount. death,
The control unit estimates the life of the electrolyte membrane by comparing the calculated amount of stored ions with a data group showing the correlation between the amount of stored ions measured in advance and the life of the electrolyte membrane. Provides a fuel cell system.

According to the present disclosure, a state close to the state in which the electrolyte membrane in the fuel cell body is actually exposed, that is, a deterioration mode of the electrolyte membrane is reproduced in a "membrane deterioration diagnosis cell" separate from the fuel cell body. By making the structure of the "membrane deterioration diagnosis cell" capable of extracting ions which are electrolyte membrane deterioration components, it is possible to predict the life of the electrolyte membrane of the fuel cell with higher accuracy.

FIG. 1 is a schematic configuration diagram showing a part of an example of the fuel cell system of the present disclosure.

The fuel cell system of the present disclosure includes at least a fuel cell, an oxidizing agent gas supply unit, a fuel gas supply unit, a cooling water supply unit, a cooling water discharge unit, a film deterioration diagnosis cell, and oxidation for a film deterioration diagnosis cell. The agent gas flow path, the fuel gas flow path for the membrane deterioration diagnosis cell, the ion amount measuring device, and the control unit are provided, and if necessary, an oxidizing agent gas discharge unit and a fuel gas discharge unit are provided.

The fuel cell has at least a membrane electrode assembly having an oxidizing agent electrode catalyst layer, a fuel electrode catalyst layer, and an electrolyte film arranged between the oxidizing agent electrode catalyst layer and the fuel electrode catalyst layer. Usually, gas diffusion layers may be provided on both sides of the membrane electrode assembly, and gas flow paths, gas separators, and the like may be provided on both sides thereof, if necessary.
The oxidant electrode catalyst layer, fuel electrode catalyst layer, electrolyte membrane, gas diffusion layer, gas flow path, and gas separator are not particularly limited, and conventionally known ones can be used.

The fuel gas supply unit includes a fuel gas supply device for supplying fuel gas to the fuel cell and a fuel gas supply flow path. As the fuel gas supply device, for example, a liquid hydrogen tank, a compressed hydrogen tank, or the like can be used.
The fuel gas discharge unit has at least a fuel gas discharge valve for adjusting the discharge flow rate of the fuel gas discharged from the fuel cell, and has a fuel gas discharge flow path as required.
The fuel cell system is a fuel gas circulation unit having a fuel gas circulation flow path that connects a fuel gas discharge flow path and a fuel gas supply flow path and circulates the fuel gas and a fuel gas circulation device arranged on the fuel gas circulation flow path. May be provided. Examples of the fuel gas circulation device include a circulation pump and the like.

The oxidant gas supply unit has at least an oxidant gas supply flow path for supplying the oxidant gas to the fuel cell, and, if necessary, an oxidant gas supply device. As the oxidant gas supply device, for example, an air compressor or the like can be used.
The oxidant gas discharge unit has an oxidant gas discharge flow path for discharging the oxidant gas from the fuel cell.

The cooling water supply unit has at least a cooling water supply device for supplying cooling water to the fuel cell and a cooling water supply flow path. As the cooling water supply device, for example, a cooling water tank, a pump, or the like can be used.
The cooling water discharge unit has a cooling water discharge flow path for discharging the cooling water from the fuel cell.

The membrane deterioration diagnosis cell has the membrane electrode assembly. That is, the membrane electrode assembly used is the same as that used for the fuel cell.
The membrane deterioration diagnosis cell is in contact with the fuel cell at the cooling water outlet of the cooling water discharge portion of the fuel cell.
The membrane deterioration diagnosis cell further has a cooling water flow path for the membrane deterioration diagnosis cell connected from the cooling water outlet of the fuel cell inside the membrane deterioration diagnosis cell.
Deterioration of the electrolyte membrane accelerates as the temperature rises or the humidity decreases. Therefore, the deterioration of the electrolyte membrane is likely to occur at the inlet portion (= low humidity portion) of the oxidant gas (Air or the like) and / or the cooling water outlet (= high temperature portion) of the fuel cell.
Therefore, the film degradation diagnosis cells adjacent to the coolant outlet of the fuel cell to the same temperature as the high temperature portion in the fuel cell, an oxidant gas to the membrane deterioration diagnostic cell (Air, etc.), the fuel gas (H ₂ gas) or the like By splitting and flowing the fuel to the same humidity as the oxidant gas inlet, it is possible to approach an environment in which film deterioration occurs in the fuel cell.
On the other hand, the membrane deterioration diagnosis cell may have a configuration without a gas diffusion layer (GDL).
When the electrolyte membrane deteriorates, fluorine ions, sulfate ions and the like are generated as decomposition products. In order to extract these ions from the electrolyte membrane, it is necessary to dissolve them in liquid water. However, when an attempt is made to extract ions dissolved in water generated by power generation in a normal fuel cell configuration (GDL / catalyst layer / electrolyte membrane / catalyst layer / GDL), the above decomposition occurs in the microporous layer (MPL) of GDL. Things get trapped. Therefore, from the viewpoint of improving the accuracy of the membrane deterioration diagnosis, the structure of the membrane deterioration diagnosis cell may be MEA (catalyst layer / electrolyte membrane / catalyst layer) without GDL. Since it is difficult to generate electricity in the membrane deterioration diagnosis cell without GDL, the decomposition product can be extracted by configuring the cooling water to flow directly into the MEA of the membrane deterioration diagnosis cell.

The oxidant gas flow path for the film deterioration diagnosis cell is not particularly limited as long as the oxidant gas can flow from the oxidant gas supply unit into the film deterioration diagnosis cell, and the oxidant gas supply unit of the film deterioration diagnosis cell. The oxidant gas supply flow path may be branched and can be separated.
The fuel gas flow path for the membrane deterioration diagnosis cell is not particularly limited as long as the fuel gas can flow from the fuel gas supply unit into the membrane deterioration diagnosis cell, and the fuel gas supply flow of the fuel gas supply unit is not particularly limited. The road may be branched and can be divided.
The two gas flow paths of the oxidant gas flow path for the membrane deterioration diagnosis cell and the fuel gas flow path for the membrane deterioration diagnosis cell are connected to the cooling water flow path for the membrane deterioration diagnosis cell upstream of the gas flow path. Has a switching valve.
Membrane degradation diagnostic cell oxidizing gas channel, the fuel gas flow path for film degradation diagnostic cell, the oxidant gas to the membrane deterioration diagnostic cell (Air, etc.), a fuel gas (H ₂ gas) flows diverted, In addition, the switching valve allows the cooling water discharged from the cooling water outlet of the fuel cell to flow from the oxidizing agent gas flow path for the film deterioration diagnosis cell and the fuel gas flow path for the film deterioration diagnosis cell to the film deterioration diagnosis cell. Yes, it is possible to boil (extract) the deteriorated components accumulated in the MEA of the membrane deterioration diagnosis cell at the time of membrane deterioration diagnosis.

The ion amount measuring device is not particularly limited as long as it can measure the amount of ions in the cooling water discharged from the membrane deterioration diagnosis cell, and examples thereof include ion chromatography, a conductivity meter, and a pH meter. ..

The control unit controls the fuel cell system.
The control unit may be connected to a fuel cell, an oxidant gas supply device, a fuel gas supply device, a cooling water supply device, an ion amount measuring device, a switching valve, a fuel gas discharge valve, and the like via an input / output interface.
The control unit switches the switching valve, calculates the amount of stored ions, estimates the life of the electrolyte membrane, determines whether the amount of stored ions exceeds the threshold, adjusts the oxidant gas supply flow rate, and adjusts the fuel gas supply flow rate. , And adjust the cooling water supply flow rate.

The life of the electrolyte membrane is estimated by using the cumulative ion amount calculated from the ion amount measured at predetermined time intervals as a data group showing the correlation between the accumulated ion amount measured in advance by experiments and the like and the life of the electrolyte membrane. The life of the electrolyte membrane may be estimated by illuminating. By estimating the life of the electrolyte membrane, it is possible to determine whether or not the fuel cell needs to be replaced.

FIG. 2 is a diagram showing an example of the relationship between the amount of sulfate ions and the life of the electrolyte membrane. For example, the control unit may be provided with a data group as shown in FIG. 2 in advance.

The control unit physically includes, for example, an arithmetic processing unit such as a CPU (central processing unit), a ROM (read-only memory) that stores a control program processed by the CPU, control data, and the like, and mainly controls. It has a storage device such as a RAM (random access memory) used as various work areas for processing, and an input / output interface.

FIG. 3 is a flowchart showing an example of control executed by the control unit used in the present disclosure. The present disclosure is not necessarily limited to this typical example.

(1) Switching from the normal operation mode of the fuel cell to the membrane deterioration diagnosis mode The control unit flows gas through the gas flow path during the normal operation of the fuel cell (normal operation mode).
During normal operation, the divided oxidant gas and fuel gas may flow through the membrane deterioration diagnosis cell, and the temperature may be set to the cooling water outlet temperature of the fuel cell.
Further, at the time of diagnosing the deterioration of the electrolyte membrane of the fuel cell, the control unit switches the valve by the switching valve and flows the cooling water through the gas flow path (membrane deterioration diagnosis mode).
At the time of film deterioration diagnosis, from the viewpoint of switching the valve of the gas flow path and flowing the cooling water from the cooling water outlet of the fuel cell to the film deterioration diagnosis cell to improve the measurement accuracy of the ion amount in the cooling water, for example, 80 ° C. or higher. The fuel cell may be operated at a high temperature of 90 ° C. or higher, preferably 90 ° C. or higher.
The timing of switching from the normal operation mode to the membrane deterioration diagnosis mode is not particularly limited, and may be performed after a predetermined time has elapsed from the start of the fuel cell, or may be performed at the start of the fuel cell. can.

(2) Calculation of Accumulated Ion Amount The control unit measures the amount of ions in the cooling water discharged from the membrane deterioration diagnosis cell by the ion amount measuring device at predetermined time intervals from the start of the deterioration diagnosis of the electrolyte membrane. Then, the amount of accumulated ions is calculated.
The method for measuring the amount of ions in the cooling water is not particularly limited. For example, an ion amount measuring device such as a conventionally known ion chromatography, conductivity meter, and pH meter is installed in the fuel cell system, and the on amount measuring device is installed. You may use it to measure the amount of the ion.
Specifically, the measurement of the amount of ions in the cooling water is carried out so that the temperature of the cooling water outlet of the fuel cell is, for example, 80 ° C. or higher, preferably 90 ° C. or higher, from the viewpoint of improving the measurement accuracy. The cooling water discharged from the cooling water outlet of the fuel cell to generate power is allowed to flow into the membrane deterioration diagnosis cell for, for example, 10 minutes or more, preferably 60 minutes or more, and the boiled water discharged from the membrane deterioration diagnosis cell is collected. , The amount of ions in the boiled water may be measured.
The timing of the first measurement of the amount of ions from the start of the deterioration diagnosis mode is not particularly limited, and may be performed after a predetermined time has elapsed from the start of the deterioration diagnosis mode (for example, 10 minutes later, preferably 60 minutes later). However, it may be performed at the start of the deterioration diagnosis mode and can be set as appropriate.
Further, the time interval from the measurement of the ion amount to the measurement of the next ion amount is not particularly limited and can be appropriately set. For example, it may be 10 minutes later or 60 minutes later. good.
The accumulated ion amount is a cumulative value of the ion amount in the cooling water measured at predetermined time intervals from the start of the deterioration diagnosis.

(3) Estimating the life of the electrolyte membrane The control unit compares the calculated amount of stored ions with the data group showing the correlation between the amount of stored ions measured in advance and the life of the electrolyte membrane, and the life of the electrolyte membrane. To estimate.

(4) Judgment of whether or not the estimated life of the electrolyte membrane is longer than the period until the next membrane deterioration diagnosis The control unit determines whether the estimated life of the electrolyte membrane is longer than the period until the next membrane deterioration diagnosis. You may judge whether or not. Then, when the control unit determines that the estimated life of the electrolyte membrane is less than the period until the next membrane deterioration diagnosis, it determines that the fuel cell needs to be replaced.
The calculated threshold value of the stored ion amount can be appropriately set from the data group by preparing a data group showing the correlation between the stored ion amount and the life of the electrolyte membrane in advance in an experiment or the like, depending on the performance of the fuel cell or the like.

(5) Judgment whether the estimated life of the electrolyte membrane is more than twice the period until the next membrane deterioration diagnosis On the other hand, the control unit determines whether the estimated life of the electrolyte membrane is until the next membrane deterioration diagnosis. If it is determined that the period is longer than that, the control may be terminated, or it may be determined whether or not the estimated lifetime of the electrolyte membrane is twice or more the period until the next membrane deterioration diagnosis.
When the control unit determines that the estimated lifetime of the electrolyte membrane is more than twice the period until the next membrane deterioration diagnosis, it stores the calculated accumulated ion amount, ends the control, and terminates the control, and the accumulated ion amount. May be integrated into the amount of accumulated ions calculated at the next membrane deterioration diagnosis.
On the other hand, if the control unit determines that the estimated life of the electrolyte membrane is less than twice the period until the next membrane deterioration diagnosis, it changes the control such as output limitation so as to lower the operating temperature of the fuel cell. Moreover, the calculated accumulated ion amount may be stored and the control may be terminated, and the accumulated ion amount may be integrated into the accumulated ion amount calculated at the next membrane deterioration diagnosis.
The method of limiting the output is not particularly limited, and the output of the fuel cell is limited by adjusting the supply flow rate of these gases by sending a signal from the control unit to the fuel gas supply unit, the oxidant gas supply unit, and the like. You may.

The start time of the second and subsequent membrane deterioration diagnoses after the completion of the first membrane deterioration diagnosis of the control unit is not particularly limited, and is continuously performed after the completion of the first membrane deterioration diagnosis. It may be performed at regular intervals for a certain period of time.

Claims (1)

A fuel cell having at least a membrane electrode assembly having an oxidant electrode catalyst layer, a fuel electrode catalyst layer, and an electrolyte membrane arranged between the oxidant electrode catalyst layer and the fuel electrode catalyst layer.
An oxidant gas supply unit that supplies the oxidant gas to the fuel cell,
A fuel gas supply unit that supplies fuel gas to the fuel cell and
A cooling water supply unit that supplies cooling water to the fuel cell,
A cooling water discharge unit that discharges the cooling water from the fuel cell,
A membrane deterioration diagnostic cell having the membrane electrode assembly and
An oxidant gas flow path for a membrane deterioration diagnosis cell in which the oxidant gas flows from the oxidant gas supply unit into the membrane deterioration diagnosis cell,
A fuel gas flow path for a membrane deterioration diagnosis cell in which the fuel gas flows from the fuel gas supply unit into the membrane deterioration diagnosis cell, and a fuel gas flow path for the membrane deterioration diagnosis cell.
Ion amount measuring device and
With a control unit
The membrane deterioration diagnosis cell is brought into contact with the fuel cell at the cooling water outlet of the cooling water discharge portion of the fuel cell.
The membrane deterioration diagnosis cell further has a cooling water flow path for the membrane deterioration diagnosis cell connected from the cooling water outlet of the fuel cell inside the membrane deterioration diagnosis cell.
The two gas flow paths of the oxidant gas flow path for the membrane deterioration diagnosis cell and the fuel gas flow path for the membrane deterioration diagnosis cell are connected to the cooling water flow path for the membrane deterioration diagnosis cell upstream of the gas flow path. Has a switching valve
The control unit flows gas through the gas flow path during normal operation of the fuel cell, switches the valve by the switching valve at the time of diagnosing deterioration of the electrolyte membrane of the fuel cell, and cools water in the gas flow path. Shed,
The control unit measures the amount of ions in the cooling water discharged from the membrane deterioration diagnosis cell by the ion amount measuring device at predetermined time intervals from the start of the deterioration diagnosis of the electrolyte membrane, and calculates the accumulated ion amount. death,
The control unit estimates the life of the electrolyte membrane by comparing the calculated amount of stored ions with a data group showing the correlation between the amount of stored ions measured in advance and the life of the electrolyte membrane. Fuel cell system.

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