JP6222958B2 - Method of operating polymer electrolyte fuel cell for cogeneration system and polymer electrolyte fuel cell for cogeneration system - Google Patents

Description

The present invention provides an oxygen-containing gas to the oxygen electrode at a location on the oxygen electrode side of a fuel cell having an oxygen electrode on one surface and a fuel electrode on the other surface of a solid polymer electrolyte membrane for a combined heat and power system. A solid polymer fuel cell for a combined heat and power system in which an oxygen supply path for supply is formed and a fuel supply path for supplying a hydrogen-containing gas to the fuel electrode is formed at a position on the fuel electrode side of the fuel cell. Operation method and oxygen for supplying an oxygen-containing gas to the oxygen electrode at a position on the oxygen electrode side of a fuel cell having an oxygen electrode on one surface of the solid polymer electrolyte membrane and a fuel electrode on the other surface The present invention relates to a polymer electrolyte fuel cell for a combined heat and power system in which a supply path is formed and a fuel supply path for supplying a hydrogen-containing gas to the fuel electrode is formed at a position on the fuel electrode side of the fuel cell.

  Such a polymer electrolyte fuel cell is, for example, installed in a general household, supplies generated power to an electric load, stores hot exhaust heat recovered by cooling the fuel cell, and stores the hot water. It is used to construct a so-called combined heat and power system, such as using hot water for hot water supply.

As a method for operating such a polymer electrolyte fuel cell, the oxygen-containing gas supplied to the oxygen electrode is adjusted to a non-humidified state or a low humidified state where the dew point is lower than the operating temperature of the fuel cell. (For example, refer to Patent Document 1).
Incidentally, in Patent Document 1, it is described that the hydrogen-containing gas supplied to the fuel electrode is adjusted to a non-humidified state or a low-humidified state where the dew point is lower than the operating temperature of the fuel cell, similarly to the oxygen-containing gas. Has been.

JP2011-258467A

  When the oxygen-containing gas supplied to the oxygen electrode is adjusted to a non-humidified state or a low humidified state where the dew point is lower than the operating temperature of the fuel cell, the amount of exhaust heat recovered by cooling the fuel cell is increased. Benefits that can be obtained.

  However, when the oxygen-containing gas supplied to the oxygen electrode is maintained in a non-humidified state or a low humidified state regardless of fluctuations in the power generation load, when the power generation load becomes a load smaller than a high load close to the rated load, The solid polymer electrolyte membrane could not be sufficiently moistened, and there was a possibility of promoting the deterioration of the fuel cell, and improvement was desired.

  That is, when the power generation load is a high load such as a rated load, a sufficient amount of moisture is generated on the oxygen electrode side due to the chemical reaction between the hydrogen-containing gas and the oxygen-containing gas. The solid polymer electrolyte membrane can be appropriately wetted by moisture.

  Thus, when the power generation load is high, the solid polymer electrolyte membrane can be appropriately wetted by the water generated by power generation, but when the power generation load becomes smaller than the high load, Since the amount of water produced on the oxygen electrode side is reduced, the solid polymer electrolyte membrane cannot be properly wetted, and there is a risk of promoting deterioration of the fuel cell.

The present invention has been made in view of the above circumstances, and its purpose is to increase the amount of exhaust heat that can be recovered when the power generation load is high, while the power generation load is smaller than the high load. In this case, the present invention is to provide a method for operating a polymer electrolyte fuel cell for a combined heat and power system that can suppress deterioration of the fuel cell.
Another object of the present invention, while the increase the waste heat that can be recovered when the power generation load is a high load, thermoelectric that degradation of the fuel cell can be suppressed when the generator load is smaller than the high-load The object is to provide a polymer electrolyte fuel cell for a co-feed system .

The solid polymer type fuel cell operating method of the present invention is the above-described oxygen electrode side portion in a fuel cell having an oxygen electrode on one surface of the solid polymer electrolyte membrane and a fuel electrode on the other surface. A solid for a combined heat and power system in which an oxygen supply path for supplying an oxygen-containing gas to an electrode is formed, and a fuel supply path for supplying a hydrogen-containing gas to the fuel electrode is formed at a location on the fuel electrode side of the fuel cell. A method for operating a polymer fuel cell, the first characteristic method is:
The humidifying state of the oxygen side humidifying means for humidifying the oxygen-containing gas supplied to the oxygen electrode is adjusted to a non-humidified state when the power generation load is equal to or higher than the set load, and the power generation load is smaller than the set load. In this case, the humidification state is adjusted to be higher than the humidification state when the set load is exceeded.

That is, the humidified state of the oxygen side humidifying means for humidifying the oxygen-containing gas supplied to the oxygen electrode, when the generator load is set load or a high load is adjusted to non-humidified state.
Then, the humidification state of the oxygen side humidifying means for humidifying the oxygen-containing gas supplied to the oxygen electrode is adjusted to a higher humidification state than the humidification state when the power generation load is smaller than the set load when the power generation load is smaller than the set load. .

That is, when the power generation load is higher than the set load, a sufficient amount of moisture is generated on the oxygen electrode side due to the chemical reaction between the hydrogen-containing gas and the oxygen-containing gas. it is possible to appropriately wet the electrolyte membrane, an oxygen-containing gas supplied to the oxygen electrode, it is adjusted to non-humidified state.

  When the power generation load is smaller than the set load, the hydrogen-containing gas and the oxygen-containing gas are adjusted by adjusting the oxygen-containing gas supplied to the oxygen electrode to a higher humidified state than the humidified state when the load is higher than the set load. The solid polymer electrolyte membrane is appropriately wetted by the wetting action of the moisture contained in the oxygen-containing gas in addition to the wetting action by the moisture generated on the oxygen electrode side.

Therefore, when the power generation load is set load or high load, the oxygen-containing gas supplied to the oxygen electrode, since it is intended to adjust the non-humidified state, accurately waste heat recovered by cooling the fuel cell Can be increased.

  In addition, when the power generation load is smaller than the set load, the oxygen-containing gas supplied to the oxygen electrode is adjusted to a higher humidified state than the humidified state when the set load or higher, so that the solid polymer electrolyte membrane Therefore, the deterioration of the fuel cell can be suppressed.

In short, according to the first characteristic method of the present invention, the amount of exhaust heat that can be recovered when the power generation load is high is increased, but the deterioration of the fuel cell is reduced when the power generation load is smaller than the high load. An operation method of a solid polymer fuel cell for a combined heat and power system that can be suppressed can be provided.

In addition to the first feature method described above, the second feature method of the solid polymer fuel cell operating method for the combined heat and power system of the present invention includes:
The humidifying state of the oxygen side humidifying means is adjusted to a higher humidifying state side as the power generation load becomes smaller than the set load.

  That is, since the humidification state of the oxygen side humidifying means is adjusted to the higher humidification side as the power generation load becomes smaller than the set load, the oxygen-containing gas supplied to the oxygen electrode is adjusted so that the power generation load is higher than the set load. However, the smaller the load, the higher the humidification state, so that the solid polymer electrolyte membrane can be appropriately wetted over and over in the entire fluctuation range of the power generation load.

  That is, the amount of water generated on the oxygen electrode side due to the chemical reaction between the hydrogen-containing gas and the oxygen-containing gas decreases as the power generation load becomes smaller than the set load, but the oxygen-containing gas supplied to the oxygen electrode is reduced. Since the power generation load is humidified so that the load is smaller than the set load, the amount of water generated on the oxygen electrode side is reduced by the water held by the oxygen-containing gas. Thus, the solid polymer electrolyte membrane can be appropriately wetted without excess or deficiency.

In short, according to the second characteristic method of the present invention, in addition to the operational effects of the first characteristic method, the solid polymer electrolyte membrane can be appropriately wetted over and over in the entire range of fluctuation of the power generation load. A method for operating a solid polymer fuel cell for a combined heat and power system that can be provided can be provided.

The third characteristic method of the solid polymer fuel cell operating method for a combined heat and power system of the present invention is the fuel cell, wherein the hydrogen-containing gas supplied to the fuel electrode is added to the fuel cell in addition to the first or second characteristic method. It is characterized in that it is adjusted to a low humidified state where the dew point is lower than the operating temperature of the cell.

  That is, since the hydrogen-containing gas supplied to the fuel electrode is adjusted to a low humidified state where the dew point is lower than the operating temperature of the fuel cell, in addition to wetting the solid polymer electrolyte membrane from the oxygen electrode side In addition, since the moisture contained in the hydrogen-containing gas can be wetted from the fuel electrode side, the entire solid polymer electrolyte membrane can be appropriately wetted.

  Moreover, since the hydrogen-containing gas is adjusted to a low humidified state where the dew point is lower than the operating temperature of the fuel cell, the hydrogen-containing gas is adjusted to a highly humidified state where the operating temperature of the fuel cell is the dew point. Compared with the case where it does, it can suppress that the waste heat amount collect | recovered by cooling a fuel battery cell falls.

In short, according to the third characteristic method of the present invention, it is possible to appropriately wet the entire solid polymer electrolyte membrane while suppressing a reduction in the amount of exhaust heat recovered by cooling the fuel cell. It is possible to provide a method for operating a solid polymer fuel cell for a combined heat and power system .

The solid polymer type fuel cell for a combined heat and power system of the present invention is provided with the oxygen electrode side portion in a fuel cell having an oxygen electrode on one surface of the solid polymer electrolyte membrane and a fuel electrode on the other surface. An oxygen supply path for supplying an oxygen-containing gas to the oxygen electrode is formed, and a fuel supply path for supplying a hydrogen-containing gas to the fuel electrode is formed at a location on the fuel electrode side of the fuel cell. The first characteristic configuration is
The control means for adjusting the humidification state of the oxygen-side humidification means for humidifying the oxygen-containing gas supplied to the oxygen electrode adjusts to a non-humidified state when the power generation load is equal to or higher than the set load, and the power generation load is set as described above. When the load is smaller than the load, the humidification state is adjusted to be higher than the humidification state when the load is equal to or higher than the set load.

That is, the control means, the humidification state of the oxygen side humidifying means for humidifying the oxygen-containing gas supplied to the oxygen electrode, when the generator load is set load or high load, adjusted to non-humidified state, and the power generation load When the load is smaller than the set load, the humidified state is adjusted to be higher than the humidified state when the set load is exceeded.

That is, when the power generation load is higher than the set load, a sufficient amount of moisture is generated on the oxygen electrode side due to the chemical reaction between the hydrogen-containing gas and the oxygen-containing gas. it is possible to appropriately wet the electrolyte membrane, an oxygen-containing gas supplied to the oxygen electrode, it is adjusted to non-humidified state.

  When the power generation load is smaller than the set load, the hydrogen-containing gas and the oxygen-containing gas are adjusted by adjusting the oxygen-containing gas supplied to the oxygen electrode to a higher humidified state than the humidified state when the load is higher than the set load. The solid polymer electrolyte membrane is appropriately wetted by the wetting action of the moisture contained in the oxygen-containing gas in addition to the wetting action by the moisture generated on the oxygen electrode side.

Therefore, when the power generation load is set load or high load, the oxygen-containing gas supplied to the oxygen electrode, since it is intended to adjust the non-humidified state, accurately waste heat recovered by cooling the fuel cell Can be increased.

  In addition, when the power generation load is smaller than the set load, the oxygen-containing gas supplied to the oxygen electrode is adjusted to a higher humidified state than the humidified state when the set load or higher, so that the solid polymer electrolyte membrane Therefore, the deterioration of the fuel cell can be suppressed.

In short, according to the first characteristic configuration of the present invention, the amount of exhaust heat that can be recovered when the power generation load is high is increased, but the deterioration of the fuel cell is reduced when the power generation load is smaller than the high load. A polymer electrolyte fuel cell for a combined heat and power system that can be suppressed can be provided.

In addition to the first characteristic configuration described above, the second characteristic configuration of the solid polymer fuel cell for the combined heat and power system of the present invention is as follows.
The control means is configured to adjust the humidification state of the oxygen-side humidification means to a higher humidification state side as the power generation load becomes smaller than the set load.

  That is, the control means adjusts the humidification state of the oxygen side humidification means to the higher humidification state side as the power generation load becomes smaller than the set load, so that the oxygen-containing gas supplied to the oxygen electrode is the power generation load. As the load becomes smaller than the set load, it is humidified in a highly humidified state, and the solid polymer electrolyte membrane can be appropriately wetted over and over in the entire fluctuation range of the power generation load.

  That is, the amount of water generated on the oxygen electrode side due to the chemical reaction between the hydrogen-containing gas and the oxygen-containing gas decreases as the power generation load becomes smaller than the set load, but the oxygen-containing gas supplied to the oxygen electrode is reduced. Since the power generation load is humidified so that the load is smaller than the set load, the amount of water generated on the oxygen electrode side is reduced by the water held by the oxygen-containing gas. Thus, the solid polymer electrolyte membrane can be appropriately wetted without excess or deficiency.

In short, according to the second characteristic configuration of the present invention, in addition to the operational effects of the first characteristic configuration, the solid polymer electrolyte membrane can be appropriately moistened without excess or deficiency over the entire range of fluctuation of the power generation load. A solid polymer fuel cell for a combined heat and power system can be provided.

According to a third characteristic configuration of the solid polymer fuel cell for the combined heat and power system of the present invention, in addition to the first or second characteristic configuration, the hydrogen-containing gas supplied to the fuel electrode is operated by the fuel cell. It is characterized by being adjusted to a low humidified state where the dew point is lower than the temperature.

  That is, since the hydrogen-containing gas supplied to the fuel electrode is adjusted to a low humidification state where the dew point is lower than the operating temperature of the fuel cell, in addition to wetting the solid polymer electrolyte membrane from the oxygen electrode side Since the hydrogen-containing gas can be moistened also from the fuel electrode side, the entire solid polymer electrolyte membrane can be appropriately moistened.

  Moreover, since the hydrogen-containing gas is adjusted to a low humidified state where the dew point is lower than the operating temperature of the fuel cell, the hydrogen-containing gas is brought into a highly humidified state where the operating temperature of the fuel cell is the dew point. Compared with the case where it adjusts, it can suppress that the waste heat amount collect | recovered by cooling a fuel battery cell falls.

In short, according to the third characteristic configuration of the present invention, it is possible to appropriately wet the entire solid polymer electrolyte membrane while suppressing a reduction in the amount of exhaust heat recovered by cooling the fuel cell. A solid polymer fuel cell for a combined heat and power system can be provided.

Overall view of cogeneration system Partial cutaway side view of cell stack Longitudinal side view of fuel cell The circuit diagram which shows the oxygen side humidifier of 1st Embodiment. The figure which shows the dew point change form of the oxygen side humidifier of 1st Embodiment. Table showing the configuration of the fuel cells used in the experiment Graph showing experimental results Graph showing experimental results The circuit diagram which shows the oxygen side humidifier of 2nd Embodiment. The figure which shows the dew point change form of the oxygen side humidifier of 2nd Embodiment.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Overall configuration of cogeneration system)
As shown in FIG. 1, a combined heat and power system includes a power generation unit 1, a hot water storage unit 3 that stores hot water heated by exhaust heat generated in the power generation unit 1 in a hot water storage tank 2 and supplies hot water, a power generation unit 1, and hot water storage. An operation control unit 4 for controlling the operation of the unit 3 is provided.

  The power generation unit 1 includes a fuel cell 5 that generates power by an electrochemical reaction between hydrogen and oxygen, a gas generation unit 6 that generates a fuel gas as a hydrogen-containing gas to be supplied to the fuel cell 5, and an oxygen-containing gas in the fuel cell 5. A blower 7 that supplies air and an inverter 8 that converts DC power output from the fuel cell 5 into AC power and supplies the AC power to a power consuming device are provided.

The fuel cell 5 is a polymer electrolyte fuel cell, which is supplied from the blower 7 through the air supply path 10 and hydrogen in the fuel gas generated by the gas generator 6 and supplied through the fuel gas supply path 9. It is configured to generate electricity by electrochemical reaction with oxygen in the air.
The air supply path 10 is provided with an oxygen side humidifier Ks as oxygen side humidification means, and the fuel gas supply path 9 is provided with a fuel gas side humidifier Kn that humidifies the fuel gas.

Incidentally, since the fuel gas supplied from the gas generating unit 6 is humidified by being generated by a steam reforming process as described later, the fuel gas side humidifier Kn can be omitted.
In this embodiment, the operating temperature of the fuel cell 5 is 70 ° C., and the humidified state of the fuel gas supplied from the gas generator 6 has a dew point that is 10 ° C. lower than the operating temperature of the fuel cell 5. It is in a low humidified state.

  The gas generation unit 6 includes a desulfurization unit 11 that desulfurizes a hydrocarbon-based raw fuel gas such as a supplied city gas, a water vapor generation unit 12 that generates water vapor using the supplied reformed water, and a water vapor generation unit 12. Reforming treatment section 13 for reforming reaction of the desulfurized raw fuel gas mixed with water vapor generated in the step, and carbon monoxide in the reformed gas discharged from the reforming treatment section 13 into carbon dioxide with steam. A shift section 14 that performs a shift process and a CO removal section 15 that removes carbon monoxide remaining in the shift gas discharged from the shift section 14 are provided.

Since the reforming reaction in the reforming processing unit 13 is an endothermic reaction, the reforming processing heating unit 16 that heats the reforming processing unit 13 by the combustion heat of the reforming burner 16a is provided.
Off gas from the fuel cell 5 is supplied to the reforming burner 16a through the exhaust fuel gas passage 17, and air from the blower 7 is supplied through the combustion air supply passage 18 branched from the air supply passage 10. The off gas from the fuel cell 5 is combusted.
Further, the combustion exhaust gas in the reforming burner 16a is configured to be flowed through the combustion exhaust gas passage 19 passing through the steam generation unit 12 and used as a heat source for generating steam.

A fuel gas supply amount adjusting valve 20 for adjusting the amount of fuel gas supplied to the fuel cell 5 is provided in the flow path of the fuel gas supply path 9 for supplying the raw fuel gas to the desulfurization section 11.
Then, the operation control unit 4 controls the opening degree of the fuel gas supply amount adjusting valve 20 and the operating state of the blower 7 according to the power generation load, so that the supply amount of fuel gas supplied to the fuel cell 5 and the air The power generation output from the fuel cell 5 is adjusted by adjusting the supply amount.

  That is, the operation control unit 4 adjusts the supply amount of fuel gas and the supply amount of air supplied to the fuel cell 5 to the increase side as the power generation load increases, so as to increase the power generation output from the fuel cell 5. It is configured.

  The cooling water circulation path 21 for circulating the cooling water of the fuel cell 5 is provided with a cooling water circulation pump 22 and an exhaust heat recovery heat exchanger 23 for exchanging heat between the cooling water of the fuel cell 5 and the hot water in the hot water storage tank 2. It has been.

  The hot water storage unit 3 is configured to store hot water in the hot water storage tank 2 in a state where temperature stratification is formed. Specifically, the hot water storage path 24 connecting the lower part and the upper part of the hot water storage tank 2 is provided. However, hot water extracted from the lower part of the hot water storage tank 2 is caused to flow through the exhaust heat recovery heat exchanger 23 by the operation of the hot water circulation pump 25 by passing through the exhaust heat recovery heat exchanger 23. The hot water storage tank 2 is returned to the upper part.

A water supply passage 26 for supplying water using tap water pressure is provided at the lower part of the hot water storage tank 2, and when hot water is taken out from the hot water supply passage 27 connected to the upper part of the hot water storage tank 2, water corresponding to the amount taken out is obtained. The hot water storage tank 2 is configured to be supplied with water.
Incidentally, the hot water supply passage 27 is provided with a heating gas burner 28 a and an auxiliary heater 28 for heating hot water passing through the hot water supply passage 27.

(Configuration of fuel cell)
As shown in FIGS. 2 and 3, the fuel cell 5 includes a stack of a plurality of fuel cells C each having an oxygen electrode 32 on one surface of the solid polymer electrolyte membrane 31 and a fuel electrode 33 on the other surface. Thus, the cell stack NC is configured.

That is, the oxygen side separator 35 that forms the oxygen supply path Rs for supplying the oxygen-containing gas to the oxygen electrode 32 is disposed at the oxygen electrode side location in the fuel cell C, and the fuel electrode side location in the fuel cell C is provided. A fuel-side separator 36 that forms a fuel supply path Rn for supplying a hydrogen-containing gas to the fuel electrode 33 is disposed.
A cooling water flow path F through which the cooling water for cooling the fuel cell C is passed is formed between the adjacent oxygen side separator 35 and the fuel side separator 36.

The fuel battery cell C, the oxygen side separator 35, and the fuel side separator 36 are sequentially laminated, and a power collecting current collecting portion 37 is provided at each of both end portions of the laminated body, thereby constituting the cell stack NC. Has been.
An electrical load is connected between the pair of current collectors 37.

In addition, as shown in FIG. 2, a supply side connection portion 38 is disposed outside one side of the pair of current collectors 37, and a discharge side connection portion is disposed outside the other side of the pair of current collectors 37. 39 is arranged.
The supply side connection unit 38 includes a fuel gas supply channel 9 that supplies the fuel gas generated by the gas generation unit 6, an air supply channel 10 that supplies air blown by the blower 7, and a cooling water circulation. The passage 21 is connected, and the exhaust side connection portion 39 is connected to the exhaust fuel gas passage 17 through which the off-gas from the fuel cell 5 flows, the exhaust air passage 40 through which the air discharged from the fuel cell 5 flows, and the cooling water circulation The path 21 is connected.

  Incidentally, the air supplied from the air supply path 10 to the supply side connection portion 38 sequentially passes through the oxygen supply paths Rs of the plurality of fuel cells C and flows to the exhaust air path 40 of the discharge side connection portion 39. The fuel gas supplied from the fuel gas supply path 9 to the supply side connection section 38 sequentially passes through the fuel supply paths Rn of the plurality of fuel cells C and flows to the exhaust fuel gas path 17 of the discharge side connection section 39. However, since the configuration is well known, detailed description is omitted in the present embodiment.

  In addition, the cooling water supplied to the supply side connection portion 38 through the cooling water circulation path 21 sequentially passes through the cooling water flow path F between the adjacent oxygen side separator 35 and the fuel side separator 36, and the discharge side connection portion 39. However, since the configuration is well known, detailed description is omitted in this embodiment.

(Details of fuel cell)
The solid polymer electrolyte membrane 31 is made of, for example, a fluororesin ion exchange membrane (Nafion or the like), and the oxygen electrode 32 and the fuel electrode 33 are air-permeable conductive materials carrying a catalyst as described below. The oxygen side separator 35 and the fuel side separator 36 are made of an airtight conductive material made of carbon or the like.

As shown in FIG. 3, the oxygen electrode 32 includes an oxygen-side catalyst layer 32A adjacent to the solid polymer electrolyte membrane 31, and an oxygen-side diffusion layer 32B having gas and moisture permeability.
The fuel electrode 33 includes a fuel-side catalyst layer 33A adjacent to the solid polymer electrolyte membrane 31, and a fuel-side diffusion layer 33B having gas and moisture permeability.

  The catalyst layer 32A of the oxygen electrode 32 and the catalyst layer 33A of the fuel electrode 33 are configured in such a manner that fine platinum particles (catalyst) having a particle size of several nanometers are supported on fine carbon powder. The diffusion layer 32B of the oxygen electrode 32 and the diffusion layer 33B of the fuel electrode 33 are configured using carbon paper, carbon cloth, or the like.

In this embodiment, in view of the fact that the smaller the amount of catalyst supported on the catalyst layer 33A of the fuel electrode 33, the higher the durability of the solid polymer electrolyte membrane 31, the higher the durability of the catalyst layer 33A of the fuel electrode 33. The amount of catalyst supported is set to 0.1 mgcm ⁻² .
In view of the fact that the amount of catalyst supported on the catalyst layer 32A of the oxygen electrode 32 does not affect the durability of the solid polymer electrolyte membrane 31, the amount of catalyst supported on the catalyst layer 32A of the oxygen electrode 32 is 0.3 mgcm ^−. Set to ² .

  Incidentally, although details of the mechanism of deterioration of the solid polymer electrolyte membrane 31 are unknown, it is predicted that hydrogen peroxide generated in the fuel cell C generates radicals and promotes decomposition. It can be considered that by reducing the amount of catalyst supported on the catalyst layer 33A of the fuel electrode 33, the frequency with which leaked air contacts the catalyst decreases, and the amount of hydrogen peroxide generated at the fuel electrode 33 decreases. it can.

Next, an experimental result in which a power generation test is performed by changing the catalyst loading amount of the catalyst layer 33A of the fuel electrode 33 and the catalyst loading amount of the catalyst layer 32A of the oxygen electrode 32 will be described.
In this experiment, as the fuel cell C, the amount of catalyst supported on the catalyst layer 33A of the fuel electrode 33 and the catalyst layer 32A of the oxygen electrode 32 is changed in three stages between 0.1 mgcm ^{−2 and} 0.5 mgcm ^−2. Five types of fuel cells C were prepared (see FIG. 6). In addition, the area of the fuel battery cell C of this experiment is 5 cm × 5 cm.

And when actually generating electric power using those fuel cells C, the change of the open circuit voltage (OCV) with the passage of time was measured. In other words, a single fuel cell C, and pure hydrogen to the fuel electrode 33 was supplied with 70% fuel utilization, and, by supplying pure oxygen at an oxygen utilization rate of 65% to the oxygen electrode 32, the rated (300mAcm ^{- 2} ) Continuous operation was performed, and the open circuit voltage (OCV) was measured periodically.
The cell temperature during power generation was 70 ° C., and pure hydrogen and pure oxygen were humidified with a dew point of 30 ° C.

FIG. 7 shows that the catalyst support amount of the catalyst layer 32A of the oxygen electrode 32 is 0.3 mgcm ⁻² , and the catalyst support amount of the catalyst layer 33A of the fuel electrode 33 is 0.1 mgcm ^{−2 to} 0.5 mgcm ⁻² . The experimental result about three types of fuel cell C which changes in three steps between is shown.

When the amount of catalyst supported on the catalyst layer 33A of the fuel electrode 33 is as small as 0.1 mgcm ⁻² , a decrease in the open circuit voltage (OCV) of the fuel cell C can be seen even if the operation time is 5000 hours. Absent.
When the catalyst loading amount of the catalyst layer 33A of the fuel electrode 33 is 0.3 mgcm ⁻² or when the catalyst loading amount of the catalyst layer 33A of the fuel electrode 33 is 0.5 mgcm ⁻² , the operation time elapses. Along with this, the open circuit voltage (OCV) of the fuel battery cell C is lowered, and when the amount of the catalyst supported on the catalyst layer 33A of the fuel electrode 33 is as large as 0.5 mgcm ⁻² , it greatly decreases. become.

Thereby, it can be understood that the smaller the amount of catalyst supported on the catalyst layer 33A of the fuel electrode 33, the higher the durability of the solid polymer electrolyte membrane 31.
That is, it is considered that the deterioration of the polymer electrolyte membrane 31 can be suppressed by reducing the amount of catalyst supported on the catalyst layer 33A of the fuel electrode 33.

In FIG. 8, the catalyst loading amount of the catalyst layer 33A of the fuel electrode 33 is 0.3 mgcm ⁻² , and the catalyst loading amount of the catalyst layer 32A of the oxygen electrode 32 is 0.1 mgcm ^{−2 to} 0.5 mgcm ⁻² . The experimental result about three types of fuel cell C which changes in three steps between is shown.
In any case where the catalyst loading amount of the catalyst layer 32A of the oxygen electrode 32 is different, the open circuit voltage (OCV) of the fuel cell C decreases as the operation time elapses.
Accordingly, it can be understood that the amount of catalyst supported on the catalyst layer 32A of the oxygen electrode 32 does not affect the durability of the solid polymer electrolyte membrane 31.

(Configuration of oxygen side humidifier)
As shown in FIG. 4, the oxygen-side humidifier Ks has a total heat exchanger 42 that gives moisture and heat held by the high-humidity fluid flowing through the moisture supply path 41 to the air flowing through the air supply path 10. Is provided.
The moisture supply path 41 is connected to a bypass path 41A that bypasses the total heat exchanger 42, and further controls the flow rate at which the high-humidity fluid flows to the total heat exchanger 42 through the moisture supply path 41. A flow rate control valve 43 and a second flow rate control valve 44 that controls the flow rate at which the high-humidity fluid flows through the bypass passage 41A are provided.

  Therefore, the oxygen side humidifier Ks is configured to change and adjust the humidification state of the air flowing through the air supply path 10 by adjusting the opening of the first flow control valve 43 and the second flow control valve 44. Hereinafter, the configuration of each part will be described.

A combustion exhaust gas passage 19 and an exhaust air passage 40 are connected to the moisture supply passage 41 so that the combustion exhaust gas after passing through the water vapor generation unit 12 and the air exhausted from the cell stack NC are mixed as a high-humidity fluid. It is configured to flow.
Incidentally, the combustion exhaust gas contains water generated by combustion in the reforming burner 16a, and the air discharged from the cell stack NC contains water generated by an electrochemical reaction in the fuel cell C. Is included.

The total heat exchanger 42 is made of a material (for example, an electrolyte membrane) that allows moisture and heat to pass through a partition portion between an air flow portion through which air flows and a high humidity fluid flow portion through which a high humidity fluid flows. It is comprised in the equipped form, Comprising: It is comprised so that the water | moisture content and heat which the high-humidity fluid which flows through a high-humidity fluid flow part may give to the air which flows through an air flow part .
When the entire amount of the high-humidity fluid flowing through the moisture supply path 41 flows through the total heat exchanger 42, the dew point of the air after passing through the total heat exchanger 42 is the target dew point (for example, 30 ° C.). Thus, the total heat exchanger 42 is manufactured.

(Control configuration of oxygen side humidifier)
The humidification state of the oxygen-side humidifier Ks is adjusted to the non-humidification state when the power generation load is equal to or higher than the set load, and when the power generation load is smaller than the set load, the humidification state is equal to or higher than the set load. Is also configured to be adjusted to a highly humidified state.

In the present embodiment, when the operation control unit 4 that functions as a control unit that adjusts the humidification state of the oxygen-side humidifier Ks sets the humidification state of the oxygen-side humidifier Ks to the non-humidification state when the power generation load is equal to or higher than the set load. When the power generation load is adjusted and the load is smaller than the set load, the first flow control valve is used to adjust the humidification state of the oxygen side humidifier Ks to a higher humidification state than the humidification state when the oxygen load is higher than the set load. 43 and the opening degree of the second flow control valve 44 are configured to be controlled.
In the present embodiment, the set load described above is set to the rated load.

That is, when the power generation load is the rated load, the operation control unit 4 adjusts the first flow rate control valve 43 to the fully closed opening degree and adjusts the second flow rate control valve 44 to the fully opened opening degree, The humidification state of the humidifier Ks is changed to a non-humidified state.
In this state, the dew point X of the air supplied to the cell stack NC through the air supply path 10 is a value corresponding to the humidity of the outside air sucked by the blower 7 (see FIG. 5).

Then, when the operation control unit 4 changes the power generation load to a low load smaller than the rated load, the operation control unit 4 adjusts the supply amount of the fuel gas and the supply amount of air supplied to the fuel cell 5 to gradually decrease side, The power generation output from the fuel cell 5 is gradually reduced, and accordingly, the opening degree of the first flow rate control valve 43 is controlled to gradually open, and the opening degree of the second flow rate control valve 44 is gradually raised. As shown in FIG. 5, the oxygen-side humidifier Ks is gradually brought into a highly humidified state by controlling to close.
In this state, the air supplied to the cell stack NC through the air supply path 10 is humidified in a highly humid state where the dew point Y is higher than the dew point X of the outside air.

Moreover, in this embodiment, it is comprised so that the humidification state of the oxygen side humidifier Ks may be adjusted to the high humidification state side, so that power generation load becomes a load smaller than setting load.
Specifically, the operation control unit 4 adjusts the humidification state of the oxygen-side humidifier Ks to the higher humidification state side as the power generation load becomes a load smaller than the set load. The opening degree of the flow control valve 44 is configured to be controlled.

That is, a dew point detection sensor 45 that detects the dew point of the air passing through the air supply path 10 is provided at a location downstream of the total heat exchanger 42 in the air supply path 10.
The operation control unit 4 stores in advance the relationship between the electric load and the target dew point in a range where the power generation load is smaller than the set load as a relationship in which the target dew point is increased as the electric load is reduced. In the small range, the opening degree of the first flow rate control valve 43 and the second flow rate control valve 44 is adjusted so that the target dew point according to the electric load is obtained.

  Incidentally, in adjusting the humidified state of the air according to the electric load in this way, the operation control unit 4 has the electric load in the range where the power generation load is smaller than the set load, the first flow control valve 43 and the second flow control valve. The first flow rate control valve 43 and the second flow rate control are stored so that the relationship between the target opening amount of 44 and the power generation load are smaller than the set load in advance so that the target opening degree is in accordance with the electric load. You may implement with the form which adjusts the opening degree of the valve 44, and the dew point detection sensor 45 can be abbreviate | omitted in this case.

  As described above, according to the present embodiment, when the power generation load of the fuel cell 5 is a high load equal to or higher than the set load, the oxygen-side humidifier Ks that humidifies the air supplied to the cell stack NC is adjusted to a non-humidified state. Therefore, the amount of exhaust heat recovered by cooling the fuel cell C can be increased accurately.

  In addition, when the power generation load of the fuel cell 5 is smaller than the set load, the oxygen-side humidifier Ks that humidifies the air supplied to the cell stack NC is adjusted to a higher humidified state than the humidified state when the set load is exceeded. Therefore, since the solid polymer electrolyte membrane 31 can be appropriately wetted, deterioration of the fuel cell C can be suppressed.

  Moreover, according to the present embodiment, the humidification state of the oxygen side humidifier Ks is adjusted to the higher humidification state side as the power generation load of the fuel cell 5 becomes smaller than the set load. The supplied air is humidified as the power generation load of the fuel cell 5 becomes smaller than the set load, so that the humidified state is humidified, and the solid polymer electrolyte membrane 31 is excessive or insufficient in the entire fluctuation range of the power generation load. And can be properly wetted.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. This second embodiment shows another embodiment of the oxygen side humidifier Ks, and the other configuration is the same as that of the first embodiment. Only parts different from the first embodiment will be described, and the same configurations as those of the first embodiment will be denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted.

  As shown in FIG. 9, the oxygen-side humidifier Ks has a total heat exchanger 42 that gives moisture and heat held by the high-humidity fluid flowing through the moisture supply path 41 to the air flowing through the air supply path 10. Are provided, and the moisture supply path 41 is connected to a bypass path 41A that bypasses the total heat exchanger 42, as in the first embodiment.

  In the second embodiment, the high humidity fluid flows through the moisture supply passage 41 through the first electromagnetic on-off valve 46 and the bypass passage 41A for switching between a flow state in which the high-humidity fluid flowing in the moisture supply passage 41 flows to the total heat exchanger 42 and a flow stop state. A second electromagnetic opening / closing valve 47 is provided to switch between a flow state in which the fluid flows and a flow stop state.

  Accordingly, the oxygen-side humidifier Ks humidifies the air flowing through the air supply path 10 when the first electromagnetic on-off valve 46 is opened to flow and the second electromagnetic on-off valve 47 is closed to stop flow. When the first electromagnetic on-off valve 46 is closed to be in a flow stop state and the second electromagnetic on-off valve 47 is opened to be in a flow state, the air flowing through the air supply path 10 is brought into a non-humidified state where the air is not humidified. It is comprised so that it may become.

In the second embodiment, when the power generation load is equal to or higher than the set load, the operation control unit 4 adjusts the humidification state of the oxygen side humidifier Ks to the non-humidification state, and the power generation load is higher than the set load. When the load is small, the first electromagnetic on-off valve 46 and the second electromagnetic on-off valve 47 are controlled so as to adjust the humidification state to be higher than the humidification state when the load is higher than the set load.
In the second embodiment, the set load described above is set to a rated load as in the first embodiment.

In other words, when the power generation load is a rated load, the operation control unit 4 closes the first electromagnetic on-off valve 46 to stop the flow and opens the second electromagnetic on-off valve 47 to the flow state, so that the oxygen-side humidifier Adjust Ks to a non-humidified state.
Note that the dew point X of air in this state is a value corresponding to the humidity of the outside air sucked by the blower 7 (see FIG. 10).

When the operation control unit 4 changes the power generation load to a low load smaller than the rated load, the operation control unit 4 opens the first electromagnetic on-off valve 46 to be in a flow state and closes the second electromagnetic on-off valve 47 to stop the flow. Then, the oxygen side humidifier Ks is adjusted to a humidified state.
The air flowing through the air supply path 10 is humidified by the oxygen-side humidifier Ks into a highly humid state where the dew point Y is higher than the dew point X of the outside air.

  Therefore, in the second embodiment, when the power generation load of the fuel cell 5 is a high load equal to or higher than the set load, the oxygen side humidifier Ks that humidifies the air supplied to the cell stack NC is adjusted to a non-humidified state. Therefore, the amount of exhaust heat recovered by cooling the fuel battery cell C can be accurately increased.

  In addition, when the power generation load of the fuel cell 5 is smaller than the set load, the oxygen-side humidifier Ks that humidifies the air supplied to the cell stack NC is adjusted to a higher humidified state than the humidified state when the set load is exceeded. Therefore, since the solid polymer electrolyte membrane 31 can be appropriately wetted, deterioration of the fuel cell C can be suppressed.

[Another embodiment ]

( 1 ) In the first and second embodiments, the case where the power generation load is the rated load is exemplified as the case where the power generation load is equal to or higher than the set load. However, the power generation load is a reference load whose set value is lower than the rated load. The time when the power generation load is larger than the set load may be implemented.

( 2 ) In the first and second embodiments, the oxygen-side humidifier Ks is provided with the total heat exchanger 42 in which the combustion exhaust gas and the air discharged from the cell stack NC flow in a mixed state as a high-humidity fluid. Although the case was illustrated, as the total heat exchanger 42, the combustion exhaust gas side total heat exchanger in which the combustion exhaust gas flows as a high humidity fluid, and the exhaust air side total heat exchanger in which the air discharged from the cell stack NC flows as a high humidity fluid A heat exchanger may be provided separately, and the total heat exchanger may be used selectively in accordance with a target humidification state.

( 3 ) In the first and second embodiments, the oxygen-side humidifier Ks including the total heat exchanger 42 is exemplified as the oxygen-side humidifier, but the oxygen-side humidifier includes oxygen in the stored humidified water. Various types of humidifiers can be used, such as using a so-called bubbling humidifier that jets gas and humidifies. In this case, for example, the humidified state can be adjusted by adjusting the temperature of the humidified water by adjusting the heating amount of the electric heater that heats the humidified water.

( 4 ) In the first and second embodiments, the case where the fuel gas reformed in the gas generator 6 is supplied as the hydrogen-containing gas supplied to the fuel electrode 33 is exemplified. Hydrogen stored in a storage alloy or the like may be supplied to the fuel electrode 33. In this case, it is preferable to humidify the hydrogen supplied to the fuel electrode 33. Specifically, the fuel-side humidifier Kn Therefore, it is preferable to adjust to a low humidification state where the dew point is lower than the operating temperature (for example, 70 ° C.) of the fuel cell C.

4 Control means 31 Solid polymer electrolyte membrane 32 Oxygen electrode 33 Fuel electrode C Fuel cell Ks Oxygen side humidification means Rs Oxygen supply path Rn Fuel supply path

Claims (6)

An oxygen supply path for supplying an oxygen-containing gas to the oxygen electrode is formed at a position on the oxygen electrode side in a fuel cell having an oxygen electrode on one surface of the solid polymer electrolyte membrane and a fuel electrode on the other surface. And, in the fuel cell side portion of the fuel cell, a method for operating the polymer electrolyte fuel cell for a combined heat and power system in which a fuel supply path for supplying a hydrogen-containing gas to the fuel electrode is formed,
The humidifying state of the oxygen side humidifying means for humidifying the oxygen-containing gas supplied to the oxygen electrode is adjusted to a non-humidified state when the power generation load is equal to or higher than the set load, and the power generation load is smaller than the set load. In the case of the above, the method for operating the solid polymer fuel cell for a combined heat and power system , wherein the humidification state is adjusted to be higher than the humidification state when the set load is exceeded. The method for operating a polymer electrolyte fuel cell for a combined heat and power system according to claim 1, wherein the humidification state of the oxygen side humidifying means is adjusted to a higher humidification state side as the power generation load becomes smaller than the set load. The operation of the polymer electrolyte fuel cell for a combined heat and power system according to claim 1 or 2, wherein the hydrogen-containing gas supplied to the fuel electrode is adjusted to a low humidification state in which a dew point is lower than an operating temperature of the fuel cell. Method. An oxygen supply path for supplying an oxygen-containing gas to the oxygen electrode is formed at a position on the oxygen electrode side in a fuel cell having an oxygen electrode on one surface of the solid polymer electrolyte membrane and a fuel electrode on the other surface. And a polymer electrolyte fuel cell for a combined heat and power system in which a fuel supply path for supplying a hydrogen-containing gas to the fuel electrode is formed at a position on the fuel electrode side in the fuel cell,
The control means for adjusting the humidification state of the oxygen-side humidification means for humidifying the oxygen-containing gas supplied to the oxygen electrode adjusts to a non-humidified state when the power generation load is equal to or higher than the set load, and the power generation load is set as described above. When the load is smaller than the load, the polymer electrolyte fuel cell for a combined heat and power system is configured to be adjusted to a higher humidification state than a humidification state when the load is equal to or higher than the set load. The solid for a combined heat and power system according to claim 4, wherein the control unit is configured to adjust the humidification state of the oxygen-side humidification unit to a higher humidification state side as the power generation load becomes smaller than the set load. Polymer fuel cell. The solid polymer fuel cell for a combined heat and power system according to claim 4 or 5, wherein the hydrogen-containing gas supplied to the fuel electrode is adjusted to a low humidification state in which a dew point is lower than an operating temperature of the fuel cell. .

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