JP2005310644A - Fuel cell power generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell power generator capable of preventing deterioration in performance due to negative pressure inside a fuel cell and exposure of the inside to a humidifying gas when the fuel cell power generator is stopped. <P>SOLUTION: This fuel cell power generator 100 is provided with a fuel cell 21 having a fuel gas flow passage 18a for running hydrogen-rich fuel gas and an oxidizer gas flow passage 18c for running an oxidizer gas, an oxidizer gas supply means 28 supplying oxidizer gas to the fuel cell 21, and a fuel generation means 23 generating fuel gas from material gas and steam and feeding the fuel gas to the fuel cell 21. When the fuel cell is stopped, humidified oxidizer gas filling the oxidizer gas flow passage 18c is replaced by an inert gas kept at a predetermined dew point or less, the humidified fuel gas filling the fuel gas flow passage 18a is replaced by the inert gas, and then, the fuel gas flow passage 18a and the oxidizer gas flow passage 18c are kept in an inert gas environment to be sealed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell power generation device, and more particularly to a fuel cell power generation capable of preventing performance deterioration due to negative pressure inside a fuel cell and exposure of the inside to a humidified gas when the fuel cell power generation device is stopped. Relates to the device.

  In a fuel cell power generator for home use, it can be said that it is desirable to repeat the power generation and stop of the fuel cell according to the amount of power consumption in daily life from the viewpoint of reducing energy costs.

  Specifically, DSS (Daily Start-up & Shut-down) operation, which operates the power generator during the daytime when power consumption increases and stops the power generator at night when power consumption decreases, effectively uses energy. Is excellent in terms of.

  In such a situation, technical problems and countermeasures related to repetitive operations of power generation and stop of the fuel cell have been reported so as to flexibly cope with DSS operation. For example, in order to prevent the electrolyte membrane from being dried during storage of the polymer electrolyte membrane (ion exchange membrane) and to restart the fuel cell quickly from the storage, the fuel gas remaining in the fuel cell immediately after the fuel cell is stopped In addition, a method for sealing a gas flow path of a fuel cell after replacing the oxidant gas with water or a humidified inert gas is disclosed (see Patent Document 1 as a conventional example).

Certainly, there is a possibility that the drying of the electrolyte membrane of the fuel cell can be dealt with by exposing the inside of the fuel cell to a humidified inert gas atmosphere while the fuel cell is stopped and stored as in Patent Document 1.
JP-A-6-251788

  By the way, in the above-described conventional method for stopping and storing a fuel cell, the following problems to be improved are inherent.

  That is, even if the fuel cell is sealed so as to be cut off from the external atmosphere, when the fuel cell is stored for a certain period of time (for example, about 15 hours to 3 days), air (oxygen gas) flows from the sealed portion to the inside of the fuel cell. There is a possibility of leakage. In particular, in the case of the above conventional humidified inert gas introduction method (introduction immediately after stopping), the water vapor contained in the humidified inert gas condenses due to the temperature drop inside the fuel cell, and the negative pressure is promoted. Concerns about contamination are further increased.

  Under these circumstances, if hydrogen-rich fuel gas is supplied when the fuel cell is restarted, local combustion by oxygen gas and fuel gas may occur at the anode of the fuel cell, leading to damage to the fuel cell and deterioration of the fuel cell performance. .

  Further, when the power generation and stoppage of the fuel cell are frequently repeated over a long period (for example, about 2 to 3 years), the electrode of the fuel cell is continuously immersed in water during the stoppage period. The water repellency of the electrode is deteriorated due to the atmosphere of fresh water, so that the drainage capacity during the operation of the fuel cell is impaired, and the performance of the fuel cell may be deteriorated. Therefore, it is necessary to avoid exposing the interior of the fuel cell to a humidified gas atmosphere for a long time as in the above-described conventional stopped storage method.

  In order to solve the above-described problems, the present invention has been made in view of the above-described problems. In stopping the fuel cell power generation apparatus, negative pressure inside the fuel cell and exposing the inside to a humidified gas are provided. An object of the present invention is to provide a fuel cell power generator capable of preventing the resulting performance deterioration.

  The present inventor first estimated the influence of the amount of pressure reduction in the fuel cell caused by the humidified inert gas with reference to FIG.

  FIG. 7 is a diagram showing the relationship between the outside air temperature and the amount of reduced pressure inside the fuel cell. The horizontal axis represents the outside air temperature, and the vertical axis represents the amount of reduced pressure. The figure is shown with the active gas dew point difference as a parameter (5 ° C. (short dotted line), 10 ° C. (one-dot chain line), 15 ° C. (long dotted line) and 25 ° C. (solid line)).

  For example, as indicated by an arrow in the figure, the amount of decompression of the alternate long and short dash line (dew point difference: 10 ° C.) corresponding to the outside air temperature of 20 ° C. on the horizontal axis is about 0.05 kpa. The temperature of the fuel cell filled with the gas of 10 ° C. is cooled by 10 ° C. (dew point difference (10 ° C.): 30 ° C. → 20 ° C.) to be equal to the outside air temperature (20 ° C.). This indicates the amount of pressure reduction (corresponding to the negative pressure) generated.

  According to FIG. 7, if the temperature difference between the dew point of the gas filling the inside of the fuel cell and the outside air temperature is plus 10 ° C. (one-dot chain line), it is within the normal operating temperature range of the fuel cell (eg, 0 ° C. to 40 ° C.), the amount of pressure reduction of the fuel cell can be suppressed to about 0.1 kpa or less. If the pressure is reduced to such a level, it is expected that the amount of oxygen gas mixed into the fuel cell is very small and the performance of the fuel cell can be maintained for a long time without problems of local combustion.

  As can be understood from such examination, in anticipation of the assumed outside air temperature, when the fuel cell is stopped, it is filled with the fuel gas humidified during operation (humidified to a dew point of about 70 ° C. during operation) and the humidified oxidant gas. It is important to quickly replace the inside of the fuel cell (gas flow path) with a dry inert gas before lowering the temperature of the fuel cell, for example, a dew point of 20 ° C. or lower, more preferably If the inside of the fuel cell is replaced by using an inert gas maintained at a dew point of 10 ° C. or lower, even if the outside air temperature is 0 ° C. and the fuel cell cools to near this temperature, the pressure inside the fuel cell is reduced. As can be seen from FIG. 7, the amount is only about 0.04 kpa (intersection of the alternate long and short dash line indicating the dew point difference of 10 ° C.) and is suitable.

  However, if the inside of the fuel cell is replaced with a dry inert gas in this way, there is a concern about drying of the electrolyte membrane, but if only the gas flow path of the fuel cell is replaced with a dry inert gas, It was also found that the moisture retention effect of the electrolyte membrane can be maintained to some extent by the water originally present in the fuel cell electrode.

  Here, the inside (gas flow path) of the fuel cell filled with the humidified fuel gas and the humidified oxidant gas is quickly replaced with a dry inert gas before the temperature of the fuel cell is lowered. It has been found that it is necessary to replace the inert gas with the inside of the fuel cell by an appropriate procedure.

  Specifically, the fuel gas channel of the anode is filled with fuel gas containing hydrogen gas, and the oxidant gas channel of the cathode is filled with oxidant gas containing oxygen gas. After replacing the oxidant gas with the inert gas, it is essential to replace the inert gas into the fuel cell in the order of replacing the anode fuel gas with the inert gas. The inventors of the present application have found that the potential of the ruthenium catalyst at the anode is increased, which may cause elution of ruthenium. In addition, it was also found that the potential of the platinum catalyst at the cathode rises, which may cause platinum oxidation.

  Hereinafter, the elution phenomenon of the anode ruthenium catalyst and the oxidation phenomenon of the cathode platinum catalyst will be described in detail with reference to FIG.

  FIG. 8A is a diagram schematically showing a change with time of the fuel cell power generation voltage before and after the stop of the fuel cell indicated by the dotted line (at the time of the inert gas replacement process of the fuel cell), FIG. 8B is a diagram schematically showing a change over time of the single electrode potential (hydrogen reference) of the anode, and FIG. 8C is a change over time of the single electrode potential (hydrogen reference) of the cathode. FIG. 8 (b) and 8 (c), the first anode potential 102 and the first cathode potential 104 (both shown by a two-dot chain line) The potential change during the replacement operation with the inert gas in the order of the cathode is shown. The second anode potential 103 and the second cathode potential 105 (both shown by a one-dot chain line) The voltage change during the replacement operation with the inert gas in the order of cathode → anode is shown.

  Here, transition of the power generation voltage, anode potential, and cathode potential of the fuel cell during operation of the fuel cell will be described.

  As can be understood from the solid line in FIG. 8A, the generated voltage 101 of the fuel cell shows an output value of about 0.75 V during its operation (the left portion from the dotted line in FIG. 8).

  During operation of the fuel cell, since the anode is filled with hydrogen gas, no potential difference with respect to the hydrogen reference occurs, and both the first and second anode potentials 102 and 103 show values near zero volts. On the other hand, since the potential difference between the cathode potential and the anode potential corresponds to the generated voltage 101, a potential corresponding to the generated voltage 101 is applied to the cathode during operation of the fuel cell, and the first and second cathode potentials 104, 105 are applied. In both cases, a value of about 0.75 V equal to the generated voltage 101 is shown.

  Next, transition of the anode potential and the cathode potential when the inside of the fuel cell is replaced with an inert gas in the order of anode → cathode after the fuel cell is stopped will be described.

  As can be understood from the solid line in FIG. 8A, after the fuel cell is stopped (the right part from the dotted line in FIG. 8), the generated voltage 101 transitions from the value of 0.75 V so as to quickly approach zero volts ( More precisely, 0.15V or less).

  Here, if the anode fuel gas (hydrogen gas) is replaced with an inert gas before the cathode oxidant gas (oxygen gas), hydrogen gas does not exist in the anode inside the fuel cell, and A state is formed in which oxygen gas is present at the cathode. Then, a part of the oxygen gas of the cathode passes through the polymer electrolyte membrane and reaches the anode. As a result, a potential based on oxygen gas is developed at the anode, and as shown in FIG. 8B, the first anode potential 102 is increased in potential due to the oxygen gas. Since the potential difference of the cathode potential 104 with respect to the first anode potential 102 corresponds to the generated voltage 101, corresponding to the potential decrease of the power generation battery 101 and the potential increase of the first anode potential 102, FIG. As shown in FIG. 5, the first cathode potential 104 also shows a rising tendency.

Such an increase in anode potential is a factor that causes ruthenium elution to the anode catalyst composed of alloy fine particles of platinum (Pt) and ruthenium (Ru). More specifically, when the anode potential exceeds 0.68 V (the shaded area in FIG. 8B), a ruthenium elution reaction of Ru + 2H ₂ O → RuO ₂ + 4H ⁺ + 4e proceeds, thereby generating a power generation reaction of the fuel cell. As a result, the catalytic reaction area required for reducing the power generation efficiency is reduced.

  In addition, the increase in the cathode potential promotes the oxidation of the platinum-based cathode catalyst, which similarly reduces the catalytic reaction area necessary for the power generation reaction of the fuel cell, leading to a decrease in power generation efficiency.

  Next, the transition of the anode potential and the cathode potential when the inside of the fuel cell is replaced with an inert gas in the order of cathode → anode after the fuel cell is stopped will be described.

  If the oxidant gas (oxygen gas) of the cathode is replaced with an inert gas prior to the fuel gas (hydrogen gas) of the anode, oxygen gas does not exist at the cathode inside the fuel cell, and hydrogen at the anode. A state is formed in which gas is present.

  Then, as in the operation of the fuel cell, since the anode is filled with hydrogen gas, a potential difference with respect to the hydrogen reference does not occur, and the second anode potential 103 is stopped as shown in FIG. 8B. After that, the value near zero volts continues to change. Further, when a part of the hydrogen gas of the anode permeates the polymer electrolyte membrane and reaches the cathode, a potential based on the hydrogen gas is developed at the cathode, and the potential difference with respect to the hydrogen reference is eliminated as shown in FIG. As shown in FIG. 8 (a), the second cathode potential 105 asymptotically approaches zero volts, and accordingly, the generated voltage 101 corresponding to the potential difference between the second anode potential 103 and the second cathode potential 105 is also shown in FIG. Thus, the transition is made asymptotically near zero volts.

  In this way, it is possible to prevent a decrease in the catalytic reaction area necessary for the power generation reaction of the fuel cell as described above by avoiding the potential increase of both the anode and the cathode.

  If the cathode potential is close to zero volts, the anode potential can be stabilized in the vicinity of zero volts based on the lowered cathode potential even if the hydrogen gas of the anode is replaced with an inert gas. .

  The present invention has been made based on the above knowledge, and the gist thereof is that the humidified gas accumulated in the fuel cell by the inert gas maintained in a predetermined dry state when the fuel cell power generation device is stopped. Is replaced according to an appropriate procedure.

  Specifically, a fuel cell power generation device according to the present invention includes a fuel cell having a fuel gas flow path for flowing fuel gas and an oxidant gas flow path for flowing oxidant gas, and the oxidant gas for the oxidant gas flow. Oxidant gas supply means for supplying to the passage; and fuel generation means for generating the fuel gas from the raw material gas and water vapor and supplying the fuel gas to the fuel gas flow path, and during the power generation period of the fuel cell, A humidified fuel gas is supplied to the fuel gas flow path, and the humidified oxidant gas is supplied to the oxidant gas flow path to cause the fuel cell to generate power, and when the fuel cell is stopped, the oxidation gas is The humidified oxidant gas filling the agent gas flow path is replaced with an inert gas kept below a predetermined dew point, and then the humidified fuel gas filling the fuel gas flow path is replaced by the inert gas. Then replace It is intended to seal in a state where the fuel gas channel and the oxidizing gas channel was maintained to the atmosphere of the inert gas.

  Here, a cooling water supply means for supplying cooling water to the cooling water passage of the fuel cell is provided, and the fuel gas passage and the oxidant gas passage are sealed in a state where the inert gas atmosphere is maintained. The fuel cell may be cooled to a predetermined temperature with the cooling water.

With such a configuration, degradation of the electrode water repellent performance due to local combustion of the fuel cell due to oxygen gas contamination and water atmosphere, and ruthenium elution from the anode due to anode potential increase, and cathode cathode due to cathode potential increase. It is possible to stop the fuel cell power generation apparatus appropriately while eliminating the conventional problem of platinum oxidation. Note that the inert gas is provided with source gas supply means for supplying the source gas to the fuel generation means. The source gas supplied from the source gas supply means may be used. In this case, however, the raw material gas supply means includes a gas cleaning unit, and when the fuel cell is stopped, after the sulfur component contained in the raw material gas is removed by the gas cleaning unit, Used as the inert gas.

  By using the raw material gas as the inert gas, it is not necessary to separately provide an inert gas supply device, and the configuration of the fuel cell power generator can be simplified.

  Regarding the fuel gas flow path, as a more specific configuration, a fuel gas inlet opening / closing means for opening / closing the inlet of the fuel gas flow path, a fuel gas outlet opening / closing means for opening / closing the outlet of the fuel gas flow path, and the fuel A dew point measuring means for measuring the dew point of the gas flowing out from the gas flow path; and a control means, wherein the control means, when the fuel cell is stopped, the fuel gas inlet opening / closing means and the fuel gas outlet opening / closing means. The raw material gas is discharged from the outlet as a replacement-treated gas together with the humidified fuel gas by supplying the raw material gas from the inlet while the replacement is measured by the dew point measuring means. It is determined whether or not the fuel gas is replaced with the raw material gas based on the dew point of the treated gas.

  Then, after determining that the fuel gas has been replaced by the raw material gas, the control means puts the fuel gas inlet opening / closing means and the fuel gas outlet opening / closing means into a closed state.

  As for the oxidant gas flow path, as a more specific configuration, an oxidant gas inlet opening / closing means that opens and closes the inlet of the oxidant gas flow path, and an oxidant gas outlet that opens and closes the outlet of the oxidant gas flow path. Open / close means, dew point measuring means for measuring the dew point of the gas flowing out from the oxidant gas flow path, and control means, wherein the control means opens and closes the oxidant gas inlet when the fuel cell is stopped. The oxidant gas outlet opening / closing means and the oxidant gas outlet opening / closing means are opened, and the raw material gas is discharged from the outlet as a replacement-treated gas together with the humidified oxidant gas by supplying the raw material gas from the inlet, It is determined whether or not the oxidant gas has been replaced with the source gas based on the dew point of the replacement-treated gas measured by the dew point measuring means.

  Then, after determining that the oxidant gas has been replaced by the source gas, the control means puts the oxidant gas inlet opening / closing means and the oxidant gas outlet opening / closing means in a closed state.

  As described above, the control means accurately determines the replacement state of the fuel gas with the raw material gas based on the dew point of the replacement-treated gas in addition to the flow rate and replacement time of the raw material gas.

  ADVANTAGE OF THE INVENTION According to this invention, when a fuel cell power generation device stops, the fuel cell power generation device which can prevent the performance deterioration resulting from the negative pressure inside a fuel cell and exposing an inside to humidified gas is obtained.

  First, the basic power generation principle of a solid polymer electrolyte fuel cell will be outlined.

  In a fuel cell, hydrogen-rich fuel gas is supplied to an anode, and an oxidant gas containing oxygen gas is supplied to a cathode, and these are electrochemically reacted to generate electricity and heat simultaneously.

  A polymer electrolyte membrane that selectively transports hydrogen ions is used as the electrolyte membrane, and the porous catalytic reaction layers disposed on both sides of the electrolyte membrane are mainly composed of carbon powder carrying a platinum-based metal catalyst. The reaction of the following formula (1) occurs in the catalytic reaction layer of the anode, the reaction of the following formula (2) occurs in the catalytic reaction layer of the cathode, and the fuel cell as a whole has the following formula (3). A reaction occurs.

H ₂ → 2H ⁺ + 2e ⁻ (1)
1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
H ₂ + 1 / 2O ₂ → H ₂ O (3)
That is, hydrogen ions generated by the reaction of the formula (1) are transported from the anode to the cathode through the electrolyte membrane, and electrons are moved from the anode to the cathode through the external circuit. At the cathode, oxygen gas and hydrogen ions and Electrons react as shown in formula (3) to generate water, and heat of reaction due to catalytic reaction can be obtained.

  As described above, the electrolyte membrane needs to have a function of selectively transporting hydrogen ions. By holding water in the electrolyte membrane, ions that can transport hydrogen ions from the anode to the cathode using the water contained in the electrolyte membrane as a movement path. It is thought that conductivity develops.

  Therefore, in order to secure hydrogen ion transport capability, it is essential to retain the electrolyte membrane. Proper management of the electrolyte membrane water retention by preventing the electrolyte membrane from drying is important for the basic performance of the electrolyte membrane. Technical matter.

  Next, the configuration of the fuel cell according to the embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a portion including an electrolyte assembly (Membrane-Electrode Assembly; MEA) of a fuel cell according to an embodiment of the present invention.

  An anode 14a and a cathode 14c are arranged on both sides of a polymer electrolyte membrane 11 made of perfluorocarbon sulfonic acid having hydrogen ion conductivity so as to sandwich the electrolyte membrane 11. Note that the subscript a of the reference number indicates that related to the anode 14a on the side involving the fuel gas such as hydrogen gas, and the subscript c indicates that related to the cathode 14c on the side involving the oxidant gas such as air. ing.

  Both the anode 14a and the cathode 14c have a two-layer structure, and the first layer (on the side of the anode 14a) in contact with the electrolyte membrane 11 is composed of a catalyst in which an alloy of platinum and ruthenium is supported on porous carbon and hydrogen ion conduction. The catalyst reaction layer 12a (hereinafter referred to as the catalyst reaction layer 12a) of the anode 14a made of a mixture with a polymer electrolyte having a property (binder), and the first layer (cathode 14c side) is platinum on porous carbon. Catalytic reaction layer 12c (hereinafter referred to as catalytic reaction layer 12c) of cathode 14c made of a mixture of a supported catalyst and a polymer electrolyte having hydrogen ion conductivity, which is in close contact with the outer surfaces of these catalytic reaction layers 12a and 12c The second layer to be laminated is a gas diffusion layer 13a (hereinafter referred to as a gas diffusion layer 13a) of the anode 14a having both air permeability and electric conductivity. And cathode 14c of the gas diffusion layer 13c (hereinafter, referred to as the gas diffusion layer 13c) is.

  The MEA 17 includes an electrolyte membrane 11, an anode 14a, and a cathode 14c. The MEA 17 is mechanically fixed, and adjacent MEAs 17 are electrically connected in series.

  In addition, a conductive separator plate 16a (hereinafter referred to as a conductive separator plate 16a) for the anode 14a is disposed in contact with the outer surface of the anode 14a. , Conductive separator plate 16c).

  Further, a fuel for the anode 14a comprising a groove (depth: 0.5 mm) for supplying a reaction gas to the anode 14a and the cathode 14c and carrying away a reaction product gas after the reaction and an excess reaction gas that did not contribute to the reaction. An oxidizing gas channel 18c for the gas channel 18a and the cathode 14c is formed on the contact surface of the conductive separator plates 16a and 16c with the MEA 17.

  Thus, a fuel cell (single cell) 20 composed of the MEA 17 and the separator plates 16a and 16c is formed.

  For example, about 60 fuel cells 20 are stacked inside the fuel cell 21, and more specifically, the outer surface of the conductive separator plate 16a of one fuel cell 20 and the other fuel cell. The fuel cells 20 are stacked so that the outer surfaces of the conductive separator plates 16c of the cells 20 face each other and come into contact with each other.

  Further, a groove (depth: 0.5 mm) 19a formed in the conductive separator plate 16a and a conductive separator plate 16c are formed on the contact surface of the conductive separator plate 16a and the conductive separator 16c adjacent thereto. A cooling water passage 19 including a groove (depth: 0.5 mm) 19c is provided.

  Thus, the temperature of the conductive separator plates 16a and 16c is adjusted by the cooling water flowing inside the cooling water passage 19, and the temperature of the MEA 17 can be adjusted via these conductive separators 16a and 16c.

  As the conductive separator plates 16a and 16c, for example, graphite plates having an outer size of 20 cm × 32 cm × 1.3 mm and impregnated with a phenol resin are used.

  On the other hand, an MEA gasket 15a (hereinafter referred to as MEA gasket 15a) on the annular rubber anode 14a side and an MEA gasket 15c (hereinafter referred to as MEA gasket 15c) on the cathode 14c side are respectively provided on the anode side outer periphery and the cathode side outer periphery of the MEA 17. MEA gasket 15c) is provided, and the gap between the conductive separator plates 16a, 16c and the MEA 17 is sealed by the MEA gaskets 15a, 15c. Thus, the MEA gaskets 15a and 15c prevent gas mixing and gas leakage of the gas flowing through the fuel and oxidant gas flow paths 18a and 18c. Further, manifold holes (not shown) for cooling water flow, fuel gas flow and oxidant gas flow are formed outside the MEA gaskets 15a and 15c.

  The configuration of the fuel cell power generator using the fuel cell as described above will be described with reference to the drawings. FIG. 2 is a block diagram showing the configuration of the fuel cell power generator according to the embodiment of the present invention.

  The fuel cell power generation apparatus 100 mainly includes a raw material gas supply means 22 for supplying a raw material gas, a second water supply means 75 (for example, a water supply pump) for supplying water to the fuel generator 23, and a raw material. A fuel generator 23 (fuel generating means) that generates a hydrogen-rich fuel gas (reformed gas) by a reforming reaction from the raw material gas supplied from the gas supply means 22 and the water supplied from the second water supply means 75 A blower 28 as air supply means for supplying an oxidant gas (air containing oxygen gas) to the humidifier 24 via an oxidant gas supply pipe 45; and a first for supplying water to the humidifier 24 The air supplied from the water supply means 74 (for example, water supply pump) and the blower 28 is humidified by the heat of the gas discharged from the fuel cell 21 and the water supplied from the first water supply means 74. And a fuel cell 21 that generates power and generates heat using the fuel gas supplied from the fuel generator 23 to the anode inlet 21Ain and the humidified oxidant gas supplied from the humidifier 24 to the cathode inlet 21Cin. The cooling water supply means 29 for supplying cooling water to the water inlet 21Win of the fuel cell 21, the raw material gas supply means 22, the first and second water supply means 74, 75, the fuel generator 23, the blower 28, and the fuel cell 21, a control unit 25 (control means) for controlling 21, a circuit unit 26 for taking out the electric power generated by the fuel cell 21, and a voltage (power generation voltage) of the circuit unit 26 is measured and supplied from the cooling water supply unit And a measurement unit 27 that receives a detection signal of the coolant temperature.

  Here, the anode inlet 21Ain of the fuel cell 21 corresponds to the inlet side of the fuel gas flow path 18a (see FIG. 1) of the fuel cell 21, and the anode outlet 21Aout corresponds to the outlet side thereof. The inlet 21Cin corresponds to the inlet side of the oxidant gas flow path 18c (see FIG. 1) of the fuel cell 21, the cathode outlet 21Cout corresponds to the outlet side, and the water inlet 21Win of the fuel cell 21 corresponds to the fuel cell 21. On the inlet side of the cooling water passage 19 (see FIG. 1), the water outlet 21 Wout corresponds to the outlet side of the cooling water passage 19.

  The source gas supply means 22 includes a gas purifier (desulfurization unit) 22p that removes impurities in the source gas and a booster pump 22b that pumps the source gas to the fuel generator 23, thereby booster pump. The raw material gas is pumped toward the fuel generator 23 through the raw material gas supply pipe 42 by 22b.

  Further, the cooling water supply means 29 stores a predetermined amount of cooling water and includes a heater or the like (not shown) so that the temperature of the cooling water inside thereof can be adjusted, and the cooling water is supplied to the fuel cell 21. A water pump 29p for pumping to the water inlet 21Win, a cooling water inlet side temperature sensor 40 for measuring the cooling water temperature upstream of the water inlet 21Win of the fuel cell 21, and cooling downstream of the water outlet 21Wout of the fuel cell 21 And a cooling water outlet side temperature sensor 41 for measuring the water temperature. By this, the water pump 29p pumps the cooling water toward the fuel cell 21 via the cooling water supply pipe 60, and the cooling water discharge pipe 61. Then, the cooling water is discharged from the fuel cell 21. The control unit 25 receives the detection signals output from the cooling water inlet / outlet temperature sensors 40 and 41 via the measurement unit 27, and the control unit 25 operates the fuel cell power generator 100 based on the detection signals. The temperature of the fuel cell 21 is appropriately controlled according to the situation.

  The fuel generator 23 also reforms a raw material gas such as methane gas using water vapor, and part of the carbon monoxide gas (CO gas) containing fuel gas flowing out from the reforming unit 23e. Is formed by a CO shift section 23f that removes the gas by a shift reaction, and a CO removal section 23g that can reduce the concentration of the fuel gas-containing CO gas flowing out of the CO shift section 23f to 10 ppm or less. With such a configuration, the CO gas concentration is reduced to a predetermined concentration level or less, the poisoning of platinum contained in the anode 14a by the CO gas in the operating temperature range of the fuel cell 21 is prevented, and deterioration of the catalytic activity is avoided. obtain. Of course, a catalyst having CO gas resistance (CO gas oxidation or detoxification) such as a platinum-ruthenium alloy is used for the anode 14a, and measures against CO gas poisoning are taken in terms of the catalyst material.

  Further, as the valve configuration of the fuel cell power generation apparatus 100, first and second switching valves 33 and 34 such as a three-way solenoid valve, and first, second, third, fourth and fourth such as an opening and closing solenoid valve. Five on-off valves 35, 36, 37, 38, 39 are installed. Also, a first dew point sensor 54 (dew point measuring means) that measures the dew point of the gas flowing out from the anode outlet 21Aout, and a second dew point sensor 55 (dew point measuring means) that measures the dew point of the gas flowing out from the cathode outlet 21Cout. Is installed.

  More specifically, the first switching valve 33 is arranged in the middle of the fuel gas supply pipe 43 between the anode inlet 21 </ b> Ain and the fuel generator 23, and the fuel gas supply pipe is switched by the switching operation of the first switching valve 33. 43 and the anode inlet 21Ain and the connection between the fuel gas supply pipe 43 and the first bypass pipe 49 can be selected.

  The second switching valve 34 is disposed in the middle of the oxidant gas supply pipe 45 between the humidifier 24 and the cathode inlet 21Cin. By the switching operation of the second switch valve 34, the oxidant gas supply pipe 45 is disposed. And the connection between the cathode inlet Cin and the connection between the oxidant gas supply pipe 45 and the second bypass pipe 50 can be selected.

  The first dew point sensor 54 and the first on-off valve 35 are arranged in the middle of the anode exhaust pipe 44 between the anode outlet 21Aout and the water removing unit 32, whereby the first outlet valve 35 opens and closes the anode outlet. It is possible to determine whether or not appropriate power generation is being performed by measuring the dew point of the gas while controlling the gas flow flowing out from 21Aout.

  The second dew point sensor 55 and the second on-off valve 36 are disposed in the middle of the cathode exhaust pipe 46 between the cathode outlet 21Cout and the humidifier 24, and the cathode outlet 21Cout is operated by the opening / closing operation of the second on-off valve 36. The dew point of the gas can be measured while controlling the gas flow flowing out of the gas, thereby determining whether or not appropriate power generation is being performed.

  The third on-off valve 37 is a second source gas branch pipe connecting the first source gas branch pipe 51 and the fuel gas supply pipe 43 branched from the source gas supply pipe 42 upstream of the fifth on-off valve 39. 52, the presence / absence of supply of the source gas supplied from the booster pump 22b to the anode inlet 21Ain can be controlled by the opening / closing operation of the third opening / closing valve 37.

  The fourth on-off valve 38 is a third source gas branch that connects the first source gas branch pipe 51 that branches from the source gas supply pipe 42 upstream of the fifth on-off valve 39 and the oxidant gas supply pipe 45. The presence / absence of supply of the source gas supplied from the booster pump 22b to the cathode inlet 21Cin can be controlled by the opening / closing operation of the fourth opening / closing valve 38 disposed in the middle of the pipe 53.

  The fifth on-off valve 39 is disposed in the middle of the source gas supply pipe 42 between the booster pump 22b and the fuel generator 23, and the fifth on-off valve 39 opens and closes the source gas supplied from the booster pump 22b. The presence or absence of supply to the fuel generator 23 can be controlled.

  The control unit 25 receives the detection signals output from the first and second dew point sensors 54 and 55, and the control unit 25 appropriately controls the operation of the fuel cell power generator 100 based on the detection signals. ing.

  The raw material gas supply means 22 and the blower 28, the first and second water supply means 74 and 75, the operation of the fuel generator 23 and the fuel cell 21, the switching operation of the first and second switching valves 33 and 34, and The opening / closing operations of the first, second, third, fourth and fifth on-off valves 35, 36, 37, 38, 39 are controlled by the control unit 25 based on detection signals (for example, temperature signals) of various devices. Thus, an appropriate DSS operation is performed.

  Regarding the fuel cell power generation apparatus 100 described above, the gas supply operation during normal operation (power generation) will be described.

  In the gas purifier 22p of the source gas supply means 22, the performance deterioration material of the fuel cell 21 contained in the source gas is removed to purify the source gas, and then the fifth open / close state of the plugged state is opened by the booster pump 22b. The purified source gas is pumped and supplied to the fuel generator 23 through the valve 39 and the source gas supply pipe 42.

  Here, since the city gas 13A containing methane gas, ethane gas, propane gas and butane gas is used as the raw material gas, the odorant tertiary butyl mercaptan (TBM) and dimethyl contained in the city gas 13A in the gas purifying section 22p. Impurities such as sulfide (DMS) and tetrahydrothiophine (THT) are adsorbed and removed. At the same time, water is supplied from the second water supply means 75 to the inside of the fuel generator 23 and is evaporated into water vapor.

  Thus, hydrogen-rich fuel gas (reformed gas) is generated from the raw material gas and water vapor by the reforming reaction in the reforming section 23e of the fuel generator 23. The fuel gas flowing out from the fuel generator 23 is connected to the fuel gas supply pipe 43 and the anode inlet 21 </ b> Ain by the switching operation of the first switching valve 33, and then is connected to the fuel cell 21 via the fuel gas supply pipe 43. While the fuel gas is supplied to the anode inlet 21Ain and flows through the fuel gas flow path 18a (see FIG. 1) of the fuel cell 21, this is used for the reaction of the formula (1) in the anode 14a.

  Of the fuel gas supplied to the fuel cell 21, the off-gas that has not been used for the power generation reaction in the fuel cell 21 flows out from the anode outlet 21 </ b> Aout and passes through the anode exhaust pipe 44 and the first dew point sensor 54. It is guided to the outside of the fuel cell 21 through the first open / close valve 35 in the opened state.

  The off gas guided to the outside is removed by the water removing unit 32 disposed in the anode exhaust pipe 44 and then sent to a combustion unit (not shown) of the fuel generator 23 where it is burned. At the same time, the heat generated by such combustion is used as heat for an endothermic reaction such as a reforming reaction.

  On the other hand, the oxidant gas (air) supplied from the blower 28 serving as the oxidant gas supply means to the humidifier 24 via the oxidant gas supply pipe 45 is supplied from the first water supply means 74 in the humidifier 24. After the humidifying treatment with the water to be performed, the oxidant gas supply pipe 45 and the cathode inlet 21Cin are made to communicate with each other by the switching operation of the second switching valve 34, and then the fuel cell 21 is connected via the oxidant gas supply pipe 45. While being supplied to the cathode inlet 21Cin and the oxidant gas flows through the oxidant gas flow path 18c (see FIG. 1) of the fuel cell 21, this is used for the reaction of the expression (2) at the cathode 14c.

  Of the humidified oxidant gas supplied to the fuel cell 21, the gas not used for the power generation reaction in the fuel cell 21 flows out from the cathode outlet 21 </ b> Cout and passes through the cathode exhaust pipe 46 to the second dew point sensor 55. And the second open / close valve 36 in the opened state is guided to the outside of the fuel cell 21.

  The remaining oxidant gas led to the outside is recirculated to the humidifier 24 through the cathode exhaust pipe 46 and water and heat contained in the recirculated oxidant gas are sent from the blower 28 inside the humidifier 24. To give fresh oxidant gas. Further, as the humidifying unit 24, a total heat exchange humidifier (not shown) using an ion exchange membrane and a hot water humidifier (not shown) are used in combination.

  Further, the cooling water accumulated in the cooling water tank 29t of the cooling water supply means 29 is supplied to the water inlet 21Win of the fuel cell 21 through the cooling water inlet side temperature sensor 40 via the cooling water supply pipe 60 by the water pump 29p. The pumped water is supplied, whereby the cooling water is guided to the cooling water passage 19 (see FIG. 1) of the fuel cell 21. Here, while the cooling water flows through the cooling water passage 19, the cooling water exchanges heat with the fuel cell 21 to remove heat from the fuel cell 21, and the temperature of the fuel cell 21 is maintained at an appropriate temperature.

  Then, the cooling water that has finished heat exchange with the fuel cell 21 is returned to the cooling water tank 29t through the cooling water discharge pipe 61 and the cooling water outlet side temperature sensor 41.

  Thus, the circuit unit 26 is connected to the output terminal 48 of the anode 14a and the output terminal 47 of the cathode 14c, and the electric power generated inside the fuel cell 21 is taken out to the circuit unit 26. The generated voltage of the circuit unit 26 is monitored by the measuring unit 27.

  Next, the operation at the start of startup of the fuel cell power generation apparatus 100 will be described.

  When the temperature of the fuel generator 23 (the reforming unit 23e) is 700 ° C. or less, the steam reforming reaction of the reforming unit 23e cannot proceed appropriately. Therefore, at the start of startup, the fuel gas flowing out from the fuel generator 23 is not led to the anode inlet 21Ain, and the fuel gas supply pipe 43 is changed to the anode exhaust pipe 44 by the switching operation of the first switching valve 33. Are communicated via the bypass pipe 49 and led to the anode exhaust pipe 44. Thereafter, the fuel gas guided to the anode exhaust pipe 44 is removed by the water removing unit 32 and then supplied to the combustor of the fuel generator 23 to be burned inside the combustor. As a result, the temperature of the fuel generator 23 (the reforming unit 23e) can be quickly increased, and the time from the start to the power generation can be shortened.

  Here, an example of the stop operation of the fuel cell power generation apparatus 100 according to the embodiment of the present invention (stop operation of the embodiment) will be described with reference to FIG. In addition, a comparison stop operation example to be compared with this will be described with reference to FIGS.

[Stop operation of the embodiment]
FIG. 3 is a flowchart showing an example of a stop operation of the fuel cell power generator according to the embodiment of the present invention.

  By adopting the stop operation with inert gas replacement inside the fuel cell 21 as shown in the flowchart of FIG. 3, the electrode water repellent caused by the local combustion of the fuel cell 21 due to oxygen gas mixing and the water atmosphere It is possible to eliminate problems such as deterioration in performance, elution of ruthenium from the anode 14a due to an increase in anode potential, and platinum oxidation of the cathode 14c due to an increase in cathode potential.

  Here, the raw material gas is used as the inert gas. As described above, by using the raw material gas as the inert gas, it is not necessary to separately provide the inert gas supply device, and the configuration of the fuel cell power generator can be simplified.

  Of course, when the inside of the fuel cell 21 is subjected to gas replacement treatment, it is necessary to select a raw material gas and clean the raw material gas so as not to adversely affect the catalyst of the fuel cell 21. Specifically, for the purpose of preventing impurities from adsorbing on the surface of the platinum catalyst of the fuel cell 21 and increasing the hydrogen overvoltage, the gas cleaning unit 22p removes impurities, particularly sulfur components, by the gas cleaning unit 22p. Is an indispensable cleaning process. Further, as the selection of the raw material gas itself, it is necessary to select a gas that does not inhibit the activity of the platinum catalyst of the fuel cell 21. From this viewpoint, methane gas, propane gas, butane gas, and ethane gas (or a mixed gas thereof) are required. It is desirable to use any gas.

  First, as a stop operation of the fuel cell power generation device 100, a power generation stop signal is transmitted from the control unit 25 to the circuit unit 26, whereby the fuel cell 21 stops the power generation operation (step S301).

  Next, as the fuel cell power generation apparatus 100 stops, the control unit 25 operates the first and second switching valves 33 and 34 as follows (step S302).

  By the switching operation of the first switching valve 33, the fuel gas supply pipe 43 and the first bypass pipe 49 are communicated to stop guiding the fuel gas flowing out from the fuel generator 23 to the anode inlet 21Ain. Similarly, by the switching operation of the second switching valve 34, the oxidant gas supply pipe 45 and the second bypass pipe 50 are communicated to guide the oxidant gas flowing out from the humidifier 24 to the cathode inlet 21Cin. Stop.

  Thereafter, in order to replace the humidified oxidant gas (oxygen gas) filled in the cathode 14c of the fuel cell 21 with the dried inert gas (raw material gas), the control unit 25 includes the third and fifth on-off valves 37 and 39. Is closed, while the fourth on-off valve 38 is opened. Thus, the source gas pumped from the booster pump 22b of the source gas supply means 22 bypassed the fuel generator 23 and was maintained in a dry state with a dew point temperature of 10 ° C. or less without being humidified here. As it is, it flows through the first source gas branch pipe 51 and the third source gas branch pipe 53 to the oxidant gas supply pipe 45 and is supplied to the cathode inlet 21Cin of the fuel cell 21. Then, the raw material gas is sent to the cathode 14c, so that the raw material gas replaces the humidified oxidant gas (oxygen gas) that fills the cathode 14c (more specifically, the oxidant gas flow path 18c). The source gas flows out from the cathode outlet 21 </ b> Cout to the cathode exhaust pipe 46 together with the oxidant gas as the replacement-treated gas, and the second dew point sensor 55 disposed in the middle of the cathode exhaust pipe 46 and the second open / close state in the plugged state. It is discharged to the outside through the valve 36 (step S303).

  Here, the control unit 25 monitors the dew point of the replacement-treated gas that flows out from the cathode outlet 21 </ b> Cout based on the output signal of the second dew point sensor 55. Then, it is determined whether or not the dew point of the replacement-treated gas flowing out from the cathode outlet 21Cout is equal to or lower than a predetermined temperature (for example, 10 ° C.) (step S304), and if the dew point is higher than 10 ° C. (No in step S304), The source gas supply operation in step S303 is repeated.

  On the other hand, if the dew point is 10 ° C. or lower (Yes in step S304), the control unit 25 determines that the oxidant gas filled in the cathode 14c has been sufficiently replaced with the source gas, and proceeds to the next step. In order to seal the inside of the cathode 14c filled with the source gas, the controller 25 closes the second and fourth on-off valves 36 and 38 (step S305). In this way, the control unit 25 accurately determines the state of replacement of the oxidant gas by the source gas (determination of whether or not it has been replaced) based on the dew point of the replacement-treated gas in addition to the flow rate of the source gas and the replacement time. obtain.

  As described above, the gas replacement process is performed in which the humidified oxidant gas filling the inside of the cathode 14c (oxidant gas flow path 18c) of the fuel cell 21 is replaced with the dry source gas. Since the oxidant gas that fills only the oxidant gas flow path 18c is replaced with the source gas, the replacement operation can be completed in a short time and the consumption of the source gas can be suppressed as much as possible.

  Subsequently, the control unit 25 opens the third on-off valve 37 in order to replace the humidified fuel gas (hydrogen gas) filled in the anode 14a of the fuel cell 21 with the dried inert gas (raw material gas). The fourth and fifth on-off valves 38 and 39 are already plugged. Thus, the source gas pumped from the booster pump 22b of the source gas supply means 22 bypassed the fuel generator 23 and was maintained in a dry state with a dew point temperature of 10 ° C. or less without being humidified here. As it is, it flows through the first source gas branch pipe 51 and the second source gas branch pipe 52 to the fuel gas supply pipe 43 and is supplied to the anode inlet 21Ain of the fuel cell 21. Then, when this raw material gas is sent to the anode 14a, the raw material gas replaces the humidified fuel gas (hydrogen gas) that fills the anode 14a (more specifically, the fuel gas passage 18a), and this raw material gas. Flows out into the anode exhaust pipe 44 from the anode outlet 21Aout together with the fuel gas as a replacement-treated gas, and the first dew point sensor 54 and the first on-off valve 35 in the opened state are disposed in the anode exhaust pipe 44. It is discharged to the water removing unit 32 (step S306).

  Here, the control unit 25 monitors the dew point of the replacement-treated gas flowing out from the anode outlet 21Aout based on the output signal of the first dew point sensor 54. Then, it is determined whether or not the dew point of the replacement-treated gas that has flowed out of the anode outlet 21Aout is equal to or lower than a predetermined temperature (for example, 10 ° C.) (step S307), and if the dew point is higher than 10 ° C. (No in step S307), The source gas supply operation in step S306 is repeated.

  On the other hand, if the dew point is 10 ° C. or lower (Yes in step S307), the control unit 25 determines that the fuel gas filled in the anode 14a has been sufficiently replaced with the raw material gas, and proceeds to the next step to start the raw material gas. The controller 25 closes the first and third on-off valves 35 and 37 to seal the inside of the anode 14a filled with (step S308).

  Thus, the control unit 25 can accurately determine the replacement state of the fuel gas by the source gas (determination of whether or not the replacement has been performed) based on the dew point of the replacement-treated gas in addition to the flow rate of the source gas and the replacement time. .

  As described above, the gas replacement process is performed in which the humidified fuel gas filling the inside of the anode 14a (fuel gas flow path 18a) of the fuel cell 21 is replaced with a dry source gas. Since the fuel gas that fills only the fuel gas passage 18a is replaced with the raw material gas, the replacement operation can be completed in a short time, and the consumption of the raw material gas can be suppressed as much as possible.

  At this time, the fifth on-off valve 39 may be temporarily opened to purge the inside of the fuel generator 23 with the raw material gas. Then, the fifth on-off valve 39 is also closed so as to stop.

  Subsequently, in order to cool the temperature of the fuel cell 21 to the vicinity of the outside air temperature, the control unit 25 appropriately adjusts the temperature of the cooling water accumulated in the cooling water tank 29t, and supplies it to the cooling water supply pipe 60. Then, the water pump 29p supplies pressure to the water inlet 21Win of the fuel cell 21 and flows out from the water outlet 21Wout to the cooling water discharge pipe 61. In this way, the controller 25 lowers the temperature of the fuel cell 21 by causing the cooling water to flow through the cooling water passage 19 (see FIG. 1) (step S309).

  Here, the control unit 25 monitors the temperature of the cooling water flowing out from the water outlet 21Wout based on the output signal of the cooling water outlet side temperature sensor 41 arranged in the cooling water discharge pipe 61. Then, it is determined whether or not the temperature of the cooling water flowing out from the water outlet 21Wout is equal to or lower than a predetermined temperature (for example, 30 ° C.) (step S310). If the temperature is higher than 30 ° C. (No in step S310), step S309 is performed. The cooling water supply operation in is repeated.

  On the other hand, if the temperature is 30 ° C. or lower (Yes in step S310), the control unit 25 determines that the fuel cell 21 has been cooled to the vicinity of the outside air temperature, and stops the cooling water supply output of the water pump 29p ( Step S311), the series of stop operations of the fuel cell power generation device 100 is completed, and the fuel cell power generation device 100 is stored in this state until the fuel cell power generation device 100 is restarted.

  Heretofore, 10 ° C. has been exemplified as the dew point and 30 ° C. has been exemplified as the cooling water temperature, but these numerical conditions can be appropriately modified according to the change in the external environment.

[Stopping operation of the first comparative example]
FIG. 4 is a flowchart showing an example of the comparison stop operation compared to the stop operation according to the above embodiment.

  In the stop operation shown in FIG. 4, the humidified fuel gas (hydrogen gas) filled in the anode 14a is replaced with the dry inert gas (raw material gas), and then the humidified oxidant gas (oxygen gas) filled in the cathode 14c. ) Is replaced by a dry inert gas (raw material gas), which is different from the stopping operation shown in FIG. Therefore, as described above, when such a stop operation of the comparative example is performed, there is a possibility that problems such as ruthenium elution from the anode 14a and platinum oxidation at the cathode 14c may occur.

  Here, the stop operation (step S401) of the fuel cell power generation device 100, the valve operation (step S402) accompanying the stop of the fuel cell power generation device 100, and the cooling operation (steps S409 to S411) of the fuel cell 21 are shown in FIG. Since these operations are the same as those shown in (Step S301, Step S302, Steps S309 to S311), description of these operations will be omitted.

  In order to replace the humidified fuel gas (hydrogen gas) filled in the anode 14a of the fuel cell 21 with the dried inert gas (raw material gas), the control unit 25 closes the fourth and fifth on-off valves 38 and 39. On the other hand, the third on-off valve 37 is opened. Thus, the source gas pumped from the booster pump 22b of the source gas supply means 22 bypassed the fuel generator 23 and was maintained in a dry state with a dew point temperature of 10 ° C. or less without being humidified here. As it is, it flows through the first source gas branch pipe 51 and the second source gas branch pipe 52 to the fuel gas supply pipe 43 and is supplied to the anode inlet 21Ain of the fuel cell 21. Then, when this raw material gas is sent to the anode 14a, the raw material gas replaces the humidified fuel gas (hydrogen gas) that fills the anode 14a (more specifically, the fuel gas passage 18a), and this raw material gas. Flows out into the anode exhaust pipe 44 from the anode outlet 21Aout together with the fuel gas as a replacement-treated gas, and the first dew point sensor 54 and the first on-off valve 35 in the opened state are disposed in the anode exhaust pipe 44. It is discharged to the water removing unit 32 (step S403).

  Here, the control unit 25 monitors the dew point of the replacement-treated gas flowing out from the anode outlet 21Aout based on the output signal of the first dew point sensor 54. Then, it is determined whether or not the dew point of the replacement-treated gas that has flowed out of the anode outlet 21Aout is equal to or lower than a predetermined temperature (for example, 10 ° C.) (step S404), and if the dew point is higher than 10 ° C. (No in step S404), The source gas supply operation in step S403 is repeated.

  On the other hand, if the dew point is 10 ° C. or lower (Yes in step S404), the control unit 25 determines that the fuel gas filled in the anode 14a has been sufficiently replaced with the raw material gas, and proceeds to the next step. In order to seal the inside of the anode 14a filled with gas, the control unit 25 closes the first and third on-off valves 35 and 37 (step S405).

  In this way, a gas replacement process is performed in which the humidified fuel gas filling the anode 14a (fuel gas flow path 18a) of the fuel cell 21 is replaced with a dry source gas.

  Subsequently, in order to replace the humidified oxidant gas (oxygen gas) filled in the cathode 14c of the fuel cell 21 with the dry inert gas (raw material gas), the control unit 25 opens the fourth on-off valve 38. . The third and fifth on-off valves 37 and 39 are already closed. Thus, the source gas pumped from the booster pump 22b of the source gas supply means 22 bypassed the fuel generator 23 and was maintained in a dry state with a dew point temperature of 10 ° C. or less without being humidified here. As it is, it flows through the first source gas branch pipe 51 and the third source gas branch pipe 53 to the oxidant gas supply pipe 45 and is supplied to the cathode inlet 21Cin of the fuel cell 21. Then, the raw material gas is sent to the cathode 14c, whereby the humidified oxidant gas (oxygen gas) filling the cathode 14c (more specifically, the oxidant gas flow path 18c) is replaced by the raw material gas, and the raw material gas is replaced. The gas flows into the cathode exhaust pipe 46 from the cathode outlet 21Cout together with the oxidant gas as the replacement-treated gas, and the second dew point sensor 55 disposed in the middle of the cathode exhaust pipe 46 and the opened second on-off valve It is discharged outside through 36 (step S406).

  Here, the control unit 25 monitors the dew point of the replacement-treated gas that flows out from the cathode outlet 21 </ b> Cout based on the output signal of the second dew point sensor 55. Then, it is determined whether or not the dew point of the replacement-treated gas flowing out from the cathode outlet 21Cout is equal to or lower than a predetermined temperature (for example, 10 ° C.) (step S407), and if the dew point is higher than 10 ° C. (No in step S407), The source gas supply operation in step S406 is repeated.

  On the other hand, if the dew point is 10 ° C. or lower (Yes in step S407), the control unit 25 determines that the oxidant gas filled in the cathode 14c has been sufficiently replaced with the source gas, and proceeds to the next step. In order to seal the inside of the cathode 14c filled with the source gas, the control unit 25 closes the second and fourth on-off valves 36 and 38 (step S408).

  In this way, a gas replacement process is performed in which the humidified oxidant gas filling the cathode 14c (oxidant gas flow path 18c) of the fuel cell 21 is replaced with a dry source gas.

  Heretofore, 10 ° C. has been exemplified as the dew point, and this numerical condition can be appropriately modified according to the change in the external environment.

[Stop operation of second comparative example]
FIG. 5 is a flowchart showing another example of the comparison stop operation compared to the stop operation according to the above embodiment.

  In the stop operation shown in FIG. 5, the humidified fuel gas (hydrogen gas) filled in the anode 14a and the humidified oxidant gas (oxygen gas) filled in the cathode 14c are not replaced by the dried raw material gas, and the control unit 25 is cooling the fuel cell 21 in this state. Therefore, as described above, when such a stop operation of the comparative example is performed, there is a possibility that a problem of electrode water repellency due to local combustion of the fuel cell 21 due to oxygen gas mixture and an atmosphere of water may occur. .

  First, as a stop operation of the fuel cell power generator 100, a power generation stop signal is transmitted to the circuit unit 26 of the control unit 25, whereby the fuel cell 21 stops the power generation operation (step S501).

  Next, with the stop of the fuel cell power generator 100, the control unit 25 operates the first and second switching valves 33 and 34 as follows (step S502).

  By the switching operation of the first switching valve 33, the fuel gas supply pipe 43 and the first bypass pipe 49 are communicated to stop guiding the fuel gas flowing out from the fuel generator 23 to the anode inlet 21Ain. Similarly, by the switching operation of the second switching valve 34, the oxidant gas supply pipe 45 and the second bypass pipe 50 are communicated to guide the oxidant gas flowing out from the humidifier 24 to the cathode inlet 21Cin. Stop.

  Thereafter, in order to seal the inside of the anode 14a filled with the humidified fuel gas, the control unit 25 closes the first and third on-off valves 35 and 37 (step S503), and humidifies the oxidant gas. In order to seal the inside of the cathode 14c filled with the control unit 25, the second and fourth on-off valves 36 and 38 are closed (step S504).

  Note that the cooling operation of the fuel cell 21 (steps S505 to S507) is the same as that shown in FIG. 3 (steps S309 to S311), and thus the description of these operations is omitted.

  The performance evaluation of the fuel cell 21 obtained by the start / stop test (DSS test) based on the sequence described in the stop operation (FIG. 3) according to the embodiment is the stop operation (FIGS. 4 and 4) of the first and second comparative examples. It was compared with that based on the sequence described in 5).

  In this characteristic evaluation, the following fuel cell 21 (MEA17) was used.

  Carbon powder acetylene black (Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd., particle size 35 nm) is mixed with an aqueous dispersion of polytetrafluoroethylene (PTFE) (D1 manufactured by Daikin Kogyo Co., Ltd.) as a dry weight. A water repellent ink containing 20% by weight of PTFE is prepared. This ink is applied and impregnated on carbon paper (TGPH060H manufactured by Toray Industries, Inc.) serving as a base material for the gas diffusion layers 13a and 13c, and is heat-treated at 300 ° C. using a hot air dryer to form the gas diffusion layer 13a. , 13c (about 200 μm).

  On the other hand, a catalyst body (50% by weight Pt) obtained by supporting a Pt catalyst (or Pt-Ru catalyst) on Ketjen Black (Ketjen Black EC manufactured by Ketjen Black International Co., Ltd., particle size 30 nm), which is carbon powder. ) 66 parts by weight is mixed with 33 parts by weight (polymer dry weight) of perfluorocarbon sulfonate ionomer (5% by weight Nafion dispersion manufactured by Aldrich, USA) which is a hydrogen ion conductive material and binder. The resulting mixture is molded to form catalyst reaction layers 12a and 12c (10 to 20 μm).

  The gas diffusion layers 13a and 13c and the catalytic reaction layers 12a and 12c thus manufactured are bonded to both surfaces of the polymer electrolyte membrane 11 (Nafion 112 electrolyte membrane manufactured by DuPont, USA) to complete the MEA 17.

  In such a material system of the fuel cell power generation apparatus 100, the fuel cell 21 is started (power generation) and stopped up to 4000 times, and the stacks of the stop operation of the embodiment and the stop operations of the first and second comparative examples are each stacked. The change in voltage was measured.

Here, as the power generation conditions at the time of power generation of the fuel cell 21, the cooling water tank 29t accumulated so that the cooling water inlet side temperature sensor 40 indicates 60 ° C. and the cooling water outlet side temperature sensor 41 indicates 65 ° C. The temperature of the cooling water and the flow rate of the cooling water flowing through the cooling water supply pipe 60 / cooling water discharge pipe 61 are adjusted. Further, the fuel gas is humidified so as to maintain the fuel gas dew point of 70 ° C., and its utilization rate is adjusted to 70%. Further, the oxidant gas is humidified so that the dew point of the oxidant gas is maintained at 70 ° C., and the utilization rate is adjusted to 40%. In this case, the current density of the fuel cell 21 was 0.2 A / cm ² .

  In FIG. 6, the horizontal axis represents the number of start and stop times of the fuel cell, and the vertical axis represents the stack voltage. The stop operation of the embodiment (FIG. 3) and the stop operations of the first and second comparative examples (FIG. 4 and FIG. 5) shows how the voltage changes.

  In the stop operation of the embodiment, the mixing of oxygen gas due to negative pressure based on the repeated operation of power generation and stop is suppressed, local combustion can be prevented, and the electrode water repellency performance is also deteriorated due to the water atmosphere. Since the deterioration of the catalyst due to the potential increase of the anode 14a and the cathode 14c can be avoided, the performance of the fuel cell 21 is not deteriorated, and the voltage of the fuel cell 21 is maintained for a long time without depending on the number of start / stop times. Is maintained stably.

  On the other hand, in the stop operation of the first comparative example, it is presumed that the catalyst deterioration of the fuel cell 21 has progressed due to the potential increase of the anode 14a and the cathode 14c, and a decrease in the stack voltage is observed as the number of start / stops increases. Is done.

  Further, in the stop operation of the second comparative example, oxygen gas inside the fuel cell is mixed due to negative pressure based on the repeated operation of power generation and stop, so that local combustion occurs there and is caused by the atmosphere of water It is presumed that the electrode water repellency performance has deteriorated, a slight decrease in the stack voltage is observed after the number of start / stops of 1000 times, and the stack voltage sharply decreases after 3000 times.

  The fuel cell power generator according to the present invention can stabilize the performance of the fuel cell even when the fuel cell is stopped and generated repeatedly, and is useful as a household fuel cell power generator.

It is sectional drawing of the part containing the electrolyte assembly of the fuel cell which concerns on embodiment of this invention. 1 is a block diagram showing a configuration of a fuel cell power generator according to an embodiment of the present invention. It is a flowchart which shows an example of the stop operation | movement of the fuel cell electric power generating apparatus which concerns on embodiment of this invention. It is a flowchart which shows an example of the comparison stop operation compared with the stop operation which concerns on embodiment. It is a flowchart which shows the other example of the comparison stop operation compared with the stop operation which concerns on embodiment. The horizontal axis represents the number of start and stop times of the fuel cell, and the vertical axis represents the stack voltage, and shows the state of voltage change between the stop operation of the embodiment and the stop operation of the first and second comparative examples. is there. It is the figure which showed the relationship between external temperature and the pressure reduction amount inside a fuel cell. It is the figure which showed typically the time-dependent change of the fuel cell power generation voltage, the anode single electrode battery, and the cathode single electrode potential before and after the stop of the fuel cell (at the time of the inert gas replacement process of the fuel cell).

Explanation of symbols

11 Electrolyte Membrane 12a Anode Catalytic Reaction Layer 12c Cathode Catalytic Reaction Layer 13a Anode Gas Diffusion Layer 13c Cathode Gas Diffusion Layer 14a Anode 14c Cathode 15a MEA Gasket 15c on Anode Side MEA Gasket 16a on Cathode Side Conductivity for Anode Separator plate 16c Conductive separator plate 17 for the cathode MEA
18a Fuel gas passage 18c Oxidant gas passage 19 Cooling water passage 19a Groove 19c formed in the conductive separator plate 16a Groove 20 formed in the conductive separator plate 16c 20 Fuel cell 21 Fuel cell 22 Raw material gas supply means 22p Gas purifier 22b Booster pump 23 Fuel generator 23e Reformer 23f Transformer 23g CO removal unit 24 Humidification unit 25 Control unit 26 Circuit unit 27 Measurement unit 28 Blower 29 Cooling water supply means 29p Water pump 29t Cooling water tank
32 Water removal part 33 1st switching valve 34 2nd switching valve 35 1st switching valve 36 2nd switching valve 37 3rd switching valve 38 4th switching valve 39 5th switching valve 40 Cooling water inlet Side temperature sensor 41 Cooling water outlet side temperature sensor 42 Raw material gas supply pipe 43 Fuel gas supply pipe 44 Anode exhaust pipe 45 Oxidant gas supply pipe 46 Cathode exhaust pipe 47 Cathode output terminal 48 Anode output terminal 49 First bypass pipe 50 Second bypass pipe 51 First source gas branch pipe 52 Second source gas branch pipe 53 Third source gas branch pipe 54 First dew point sensor 55 Second dew point sensor 60 Cooling water supply pipe 61 Cooling water Discharge pipe 74 First water supply means 75 Second water supply means 100 Fuel cell power generator

Claims (8)

A fuel cell having a fuel gas flow channel for flowing fuel gas and an oxidant gas flow channel for flowing oxidant gas, an oxidant gas supply means for supplying the oxidant gas to the oxidant gas flow channel, source gas and water vapor Fuel generating means for generating the fuel gas from and supplying the fuel gas to the fuel gas flow path,
During the power generation period of the fuel cell, a humidified fuel gas is supplied to the fuel gas channel, and a humidified oxidant gas is supplied to the oxidant gas channel to cause the fuel cell to generate power, and the fuel cell When the battery is stopped, the humidified oxidant gas filling the oxidant gas flow path is replaced with an inert gas kept at a predetermined dew point or lower, and then the humidification gas filling the fuel gas flow path is filled. A fuel cell power generator that seals the fuel gas flow path and the oxidant gas flow path maintained in the inert gas atmosphere after replacing the fuel gas with the inert gas.   A cooling water supply means for supplying cooling water to the cooling water passage of the fuel cell, and sealing the fuel gas passage and the oxidant gas passage in an inert gas atmosphere; The fuel cell power generator according to claim 1, wherein the battery is cooled to a predetermined temperature by the cooling water.   3. The fuel cell power generator according to claim 2, further comprising a source gas supply unit that supplies the source gas to the fuel generation unit, wherein the inert gas is a source gas supplied from the source gas supply unit.   The source gas supply means includes a gas cleaning unit, and when the fuel cell is stopped, the source gas is used as the inert gas after the sulfur component contained in the source gas is removed by the gas cleaning unit. The fuel cell power generator according to claim 3.   Fuel gas inlet opening / closing means for opening / closing the inlet of the fuel gas flow path, fuel gas outlet opening / closing means for opening / closing the outlet of the fuel gas flow path, and dew point measurement for measuring the dew point of the gas flowing out from the fuel gas flow path Means and a control means, and when the fuel cell is stopped, the control means opens the fuel gas inlet opening / closing means and the fuel gas outlet opening / closing means to open the fuel gas from the inlet. The supply gas discharges the raw material gas together with the humidified fuel gas as a replacement processed gas from the outlet, while the fuel is supplied by the raw material gas based on the dew point of the replacement processed gas measured by the dew point measuring means. The fuel cell power generator according to claim 3, wherein it is determined whether or not the gas is replaced.   6. The fuel cell power generator according to claim 5, wherein after the control means determines that the fuel gas is replaced by the raw material gas, the fuel gas inlet opening / closing means and the fuel gas outlet opening / closing means are closed.   Oxidant gas inlet opening / closing means for opening / closing the inlet of the oxidant gas flow path, oxidant gas outlet opening / closing means for opening / closing the outlet of the oxidant gas flow path, and dew point of gas flowing out from the oxidant gas flow path A dew point measuring means for measuring the fuel cell, and a control means, wherein the control means opens the oxidant gas inlet opening and closing means and the oxidant gas outlet opening and closing means when the fuel cell is stopped, By supplying the source gas from the inlet, the source gas is discharged from the outlet as a replacement-treated gas together with the humidified oxidant gas, while the dew point of the replacement-treated gas measured by the dew point measuring means is 4. The fuel cell power generator according to claim 3, wherein it is determined whether or not the oxidant gas is replaced with the raw material gas.   8. The fuel cell power generation according to claim 7, wherein the control means sets the oxidant gas inlet opening / closing means and the oxidant gas outlet opening / closing means to a closed state after determining that the oxidant gas is replaced by the source gas. apparatus.

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