JP2005044621A - Fuel cell power generation device and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell power generation device improved in durability by restraining deterioration by oxidization of an anode and a cathode in start and stop; and to provide its operation method. <P>SOLUTION: This fuel cell power generation device is provided with: an electrolyte 1; a pair of electrodes 21 and 22; a fuel cell 5 comprising a pair of separator plates 41 and 42; a desulfurization part 6 for desulfurizing a material gas; and a gas replacement part for replacing all or a part of a fuel gas and an oxidizer gas left in the fuel cell 5 with desulfurized material gases. Since the fuel gas and the oxidizer gas are replaced with the desulfurized material gases, deterioration of the anode 21 and the cathode 22 due to oxidation is restrained, and durability of the fuel cell power generation device is improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a fuel cell power generation apparatus and a method for operating the fuel cell power generation apparatus that suppress deterioration due to start / stop or improve durability.

  The configuration and operation of a conventional general solid polymer electrolyte fuel cell will be described with reference to FIG. In FIG. 9, reference numeral 1 denotes a solid polymer electrolyte made of perfluorocarbon sulfonic acid having hydrogen ion conductivity, and a pair of electrodes 21 and 22 are formed on both surfaces of the electrolyte 1. The electrodes 21 and 22 include a catalyst layer made of a mixture of a catalyst in which a noble metal such as platinum is supported on porous carbon and a polymer electrolyte having hydrogen ion conductivity, and air permeability and electronic conductivity laminated on the catalyst layer. A gas diffusion layer having Gaskets 31 and 32 for preventing gas mixing and leakage are disposed around the electrodes 21 and 22, respectively, and conductive materials having gas flow paths for supplying and discharging fuel gas and oxidant gas to the electrodes 21 and 22, respectively. Is sandwiched between separator plates 41 and 42.

  A stack obtained by stacking a plurality of single cells having the above configuration is referred to as a stack, and the single cell or stack is collectively referred to as a fuel cell 5. The electrode 21 on the fuel gas supply side is the anode, and the electrode 22 on the oxidant gas supply side is the cathode.

  When the fuel gas and the oxidant gas are supplied to the anode 21 and the cathode 22, respectively, and an electronic load is connected, the hydrogen contained in the fuel gas supplied to the anode 21 releases electrons at the interface between the anode 21 and the electrolyte 1 to generate hydrogen. It becomes an ion (Chemical formula 1).

  The hydrogen ions move to the cathode 22 through the electrolyte 1, receive electrons at the interface between the cathode 22 and the electrolyte 1, react with oxygen contained in the oxidant gas supplied to the cathode 22, and generate water ( 2).

  The total reaction is shown in (Chemical Formula 3).

  At this time, the flow of electrons flowing through the electronic load can be used as DC electrical energy. Moreover, since a series of reactions are exothermic reactions, the reaction heat can be used as thermal energy.

  Next, the configuration and operation of a general fuel cell power generator including the fuel processing unit 7 will be described with reference to FIG. In FIG. 9, the raw material gas containing hydrocarbons such as methane is supplied to the desulfurization section 6 and the sulfur compounds contained in the odorant and the like are adsorbed and removed. Then, it is reformed by the fuel processing unit 7 to become a fuel gas containing hydrogen, and is supplied to the anode 21 of the fuel cell 5. The fuel processing unit 7 includes a reforming unit 71 that reforms methane and the like, a CO conversion unit 72 that converts generated carbon monoxide (CO), and a CO removal unit 73 that further removes CO.

  When methane is used as the source gas, in the reforming unit 71, the reaction shown in (Chemical Formula 4) occurs with water vapor, and about 10% of CO is generated together with hydrogen.

  Thereafter, the generated CO is oxidized to carbon dioxide at the CO conversion section 72 as shown in (Chemical Formula 5), and is reduced to about 5000 ppm. Since the downstream CO remover 73 oxidizes not only CO but also hydrogen of the fuel gas, the CO concentration needs to be reduced as much as possible in the CO shift section 72.

  Further, the remaining CO is oxidized by the CO remover 73 as shown in (Chemical Formula 6), and its concentration is reduced to about 10 ppm or less.

  The overall reaction formula is shown in (Chemical Formula 7).

  Since platinum contained in the anode 21 is poisoned by CO in the operating temperature range of the fuel cell 5 and its catalytic activity deteriorates, a catalyst having CO resistance such as platinum-ruthenium is usually used for the anode 21. However, even in a CO-resistant catalyst, the CO concentration contained in the fuel gas must be suppressed to at least 10 ppm or less.

  The fuel cell power generation device is mainly composed of the fuel cell 5 and the fuel processing unit 7 described above. However, when a raw material gas such as city gas mainly composed of methane is used for home use, the merit of utility cost is increased. Therefore, an operation method is effective in which the vehicle is stopped during a time period with a small amount of electricity consumption and is operated during a time period with a large amount of electricity consumption. In general, DSS (Daily Start-up & Shut-down) operation, which operates in the daytime and stops operation in the middle of the night, can increase the utility cost, and the fuel cell power generator has an operation pattern including start and stop. It is desirable to be able to respond flexibly.

  Further, in the conventional phosphoric acid type fuel cell power generator, from the viewpoint of safety, it is necessary to replace the fuel gas remaining inside the apparatus with an inert gas such as nitrogen when stopped. Several stopping methods using an inert gas purge have been reported for solid polymer electrolyte fuel cell power generators.

  For example, the fuel gas and the oxidant gas remaining in the fuel cell are replaced with water or a humidified inert gas and stopped in a sealed state (see Patent Document 1). Thereby, the water retention state of the electrolyte 1 is maintained, and power generation can be started quickly upon restart.

Alternatively, the fuel cell 5 is stopped by generating power in the state where the supply of the oxidant gas is stopped, consuming oxygen from the cathode 22, and then replacing the anode 21 with an inert gas such as nitrogen (Patent Document). 2). Thereby, not only the oxidation of the cathode 22 can be suppressed, but also hydrogen diffused from the anode 21 through the electrolyte 1 can reduce and remove impurities adhering to the cathode 22.
JP-A-6-251788 JP 2002-93448 A

  However, the conventional configuration requires a gas cylinder such as nitrogen as an inert gas, which not only increases the size of the apparatus but also costs maintenance for cylinder replacement and is not economical.

  Further, in the conventional method of purging water or humidified inert gas, the temperature of the fuel cell 5 is lowered at the time of stoppage, condensation occurs inside the fuel cell 5, the volume is reduced, and a negative pressure is generated. For this reason, there have been problems such as the inflow of external oxygen, the electrolyte 1 being damaged, and the electrodes 21 and 22 being short-circuited.

  Further, in the conventional method in which the cell is generated in a state where the supply of the oxidant gas is stopped and oxygen in the cathode 22 is consumed, and then the inert gas is purged in the anode 21, the remaining oxygen that cannot be consumed in the cathode 22 remains. In addition, there is a problem that the cathode 22 is oxidized and deteriorated due to the influence of air mixed in due to diffusion or leakage. In addition, since oxygen is forcibly consumed by power generation, the potential of the cathode 22 is not uniform, and the activation state of the cathode is different every time it is stopped, and the battery voltage at startup varies.

  The present invention solves the above-described conventional problems. When the fuel cell is stopped, the fuel gas and the oxidant gas remaining in the fuel cell 5 are replaced with desulfurized raw material gas. It is an object of the present invention to provide a fuel cell generator having excellent performance, and further to provide a method of operating a fuel cell generator that suppresses deterioration due to oxidation of the anode 21 and the cathode 22 during start-up and improves durability.

  In order to solve the above-described conventional problems, a fuel cell power generation device and an operation method thereof according to the present invention include a fuel cell including an electrolyte, a pair of electrodes, and a pair of separator plates, and a desulfurization unit that desulfurizes a source gas. The fuel processing unit and the gas replacement unit are provided to replace all or part of the fuel gas and the oxidant gas remaining in the fuel cell with the desulfurized source gas when the fuel cell is stopped.

  This eliminates the need for a gas cylinder such as nitrogen, and can not only reduce the size of the apparatus while ensuring the safety of the apparatus, but also greatly reduce the maintenance and cost required for cylinder replacement.

  Further, by using the desulfurized raw material gas, deterioration due to oxidation of the anode and the cathode can be suppressed, and the durability of the fuel cell power generator can be improved.

  As described above, according to the fuel cell power generator of the present invention and the operation method thereof, by using the desulfurized raw material gas, a gas cylinder such as nitrogen becomes unnecessary, and the device can be reduced in size while ensuring the safety of the device. The maintenance and cost required for cylinder replacement can be significantly reduced.

  Further, by substituting with the source gas, deterioration due to oxidation of the anode and the cathode can be suppressed, and the durability of the fuel cell power generator can be improved.

  The invention according to claim 1 supplies and discharges an electrolyte, a pair of electrodes sandwiching the electrolyte, and a fuel gas containing at least hydrogen on one of the electrodes, and supplies and discharges an oxidizing gas containing at least oxygen on the other. A fuel cell comprising at least one cell comprising a pair of separator plates having a gas flow path, a desulfurization unit for desulfurizing a source gas, a fuel processing unit for generating fuel gas from the desulfurized source gas, and a fuel cell A gas replacement unit that replaces all or part of the fuel gas and oxidant gas remaining in the fuel cell at the time of shutdown with desulfurized source gas, and by using the desulfurized source gas, a gas cylinder such as nitrogen becomes unnecessary. Not only can the apparatus be downsized, but also maintenance and cost required for cylinder replacement can be greatly reduced.

  Moreover, by substituting with the desulfurized source gas, deterioration due to oxidation of the anode and the cathode can be suppressed, and the durability of the fuel cell power generator can be improved.

  The invention described in claim 2 is particularly preferably provided with a shutoff valve in the fuel gas and oxidant gas supply section and discharge section according to claim 1, and after the fuel gas and oxidant gas are replaced with desulfurized source gas. By closing the shut-off valve and sealing the desulfurized source gas into the fuel cell, the oxidation of the anode and cathode by the air (oxygen) diffused from the outside and the drying of the electrolyte are suppressed, and impurities etc. are mixed Can be prevented, and the durability of the apparatus can be improved.

  The invention according to claim 3 supplies and discharges an electrolyte, a pair of electrodes sandwiching the electrolyte, and a fuel gas containing at least hydrogen on one of the electrodes, and supplies and discharges an oxidant gas containing at least oxygen on the other. A fuel cell having at least one cell composed of a pair of separator plates having gas flow paths, and all or part of the fuel gas and oxidant gas remaining in the fuel cell when the fuel cell is stopped with an inert gas A gas replacement unit for replacing, and a voltage detection unit for detecting the voltage of the fuel cell. When the fuel cell is stopped, the supply of the fuel gas and the oxidant gas is stopped at the same time. After detecting below the voltage, supply of fuel gas and oxidant gas is stopped simultaneously by replacing all or part of the fuel gas and oxidant gas remaining in the fuel cell with inert gas. Then, the hydrogen diffused from the anode through the electrolyte reduces and removes the oxide film formed on the surface of the cathode platinum and impurities adhering to the cathode, which activates the cathode. The lowered battery voltage can be recovered at startup.

  In addition, when the anode in which hydrogen remains is used as a reference, the cathode potential can be estimated from the voltage detected by the voltage detector. When the cathode is activated by the hydrogen diffused from the anode, the cathode potential decreases, so the activation status of the cathode can be known from the voltage detected by the voltage detector, and the cathode is always activated at a constant voltage. If it does, the battery voltage at the time of starting can be stabilized.

  In addition, after reducing the voltage of the fuel cell to a predetermined voltage, all or part of the fuel gas and oxidant gas remaining in the fuel cell is replaced with an inert gas, so that deterioration due to oxidation of the anode and cathode is suppressed. In addition, the durability of the fuel cell power generator can be improved.

  The invention according to claim 4 supplies and discharges an electrolyte, a pair of electrodes sandwiching the electrolyte, and a fuel gas containing at least hydrogen on one of the electrodes, and supplies and discharges an oxidizing gas containing at least oxygen on the other. A fuel cell having at least one cell composed of a pair of separator plates having gas flow paths, and all or part of the fuel gas and oxidant gas remaining in the fuel cell when the fuel cell is stopped with an inert gas A gas replacement unit for replacing, and a voltage detection unit for detecting the voltage of the fuel cell. When the fuel cell is stopped, the supply of the oxidant gas is stopped while the fuel gas is supplied, and the voltage detection unit detects the voltage of the fuel cell. After detecting that the voltage is lower than the predetermined voltage, the supply of the fuel gas is stopped, and the fuel gas remaining in the fuel cell and the oxidant gas are all or partly replaced with an inert gas, whereby the fuel gas When stopping the supply of the oxidizing gas remains supplied, can be the anode of the reference potential is more stable, cathode activation situation be further stabilized.

  The invention according to claim 5 supplies and discharges an electrolyte, a pair of electrodes sandwiching the electrolyte, a fuel gas containing at least hydrogen on one of the electrodes, and an oxidant gas containing at least oxygen on the other. A fuel cell having at least one cell composed of a pair of separator plates having gas flow paths, and all or part of the fuel gas and oxidant gas remaining in the fuel cell when the fuel cell is stopped with an inert gas A gas replacement unit for replacement and a voltage detection unit for detecting the voltage of the fuel cell are provided, and when the fuel cell is stopped, the supply of the oxidant gas is stopped while the fuel gas is supplied, and the oxidant gas remaining in the fuel cell All or a part of the fuel cell is replaced with an inert gas, and after the voltage detector detects that the fuel cell voltage is equal to or lower than a predetermined voltage, the supply of the fuel gas is stopped, and all the fuel gas remaining in the fuel cell Alternatively, by replacing the oxidant gas with the inert gas while supplying the fuel gas by replacing part of it with the desulfurized inert gas, the oxygen at the cathode is forcibly discharged, so that it is activated more quickly. be able to. Moreover, since oxygen remaining in the gas diffusion layer or the like that cannot be replaced only by stopping the gas is also replaced, deterioration can be further suppressed.

  The invention described in claim 6 is provided with a shutoff valve in the fuel gas and oxidant gas supply section and discharge section according to claims 3 to 5 in particular, and the fuel gas and oxidant gas remaining in the fuel cell are removed. After substituting with an inert gas 2 to 5 times the volume of each gas flow path, the shut-off valve is closed, and the inert gas is sealed in the fuel cell until it is activated, so that the anode and The active state of the cathode can be maintained.

  The invention described in claim 7 is provided with a shutoff valve in the fuel gas and oxidant gas supply section and discharge section according to claims 3 to 5, particularly for the fuel gas and oxidant gas remaining in the fuel cell. After replacing all or part with inert gas, close the shut-off valve, open the shut-off valve just before starting, and supply the inert gas for a certain period of time, so that it will diffuse from the outside due to leaks etc. during long-term stoppage The coming oxygen can be replaced immediately before power generation, and the deterioration of the electrode due to oxygen can be further suppressed.

  The invention described in claim 8 is provided with a shutoff valve in the fuel gas and oxidant gas supply section and discharge section according to claims 3 to 5 in particular, and the fuel gas and oxidant gas remaining in the fuel cell. After replacing all or part with inert gas, close the shut-off valve, and periodically open the shut-off valve and supply the inert gas for a certain period of time, due to leaks etc. during long-term shutdown Oxygen diffused from the outside can be periodically replaced, and deterioration of the electrode due to oxygen can be further suppressed.

  The invention according to claim 9 is the invention, in particular, all or a part of the fuel gas and the oxidant gas remaining in the fuel cell after the temperature of the fuel cell according to claims 3 to 5 falls below a predetermined temperature. By substituting with an inert gas, even if impurities or the like are contained in the inert gas, the reaction temperature is lowered to reduce the influence thereof, so that the durability can be further improved.

  The invention according to claim 10 is provided with a desulfurization section for desulfurizing the raw material gas and a fuel processing section for generating fuel gas from the desulfurized raw material gas. By using it as an active gas, a gas cylinder such as nitrogen becomes unnecessary, and not only the apparatus can be miniaturized, but also maintenance and cost required for cylinder replacement can be greatly reduced.

(Embodiment 1)
FIG. 1 shows a configuration diagram of a fuel cell power generator according to the present invention.

  In FIG. 1, reference numeral 1 denotes a membrane-shaped solid polymer electrolyte made of a perfluorocarbon sulfonic acid polymer having hydrogen ion conductivity, and a pair of electrodes, an anode 21 and a cathode 22 are formed on both surfaces of the electrolyte 1. When the electrolyte 1 takes in moisture, the hydrogen ions of the sulfonic acid groups in the electrolyte 1 are dissociated to become charge carriers, and the electrolyte 1 passes through a reverse micelle structure formed by aggregation of several sulfonic acid groups. Shows hydrogen ion conductivity. When the water content decreases, the conductivity of the electrolyte 1 decreases. Therefore, a method was adopted in which the gas was humidified and supplied to prevent the membrane from drying.

  In addition, during power generation, when hydrogen ions move to the cathode 22, they move with water on the anode 21 side, so that the water content of the electrolyte 1 is high on the cathode 22 side and low on the anode 21 side. In order to correct this, the thickness of the electrolyte 1 was reduced so that water was back-diffused. As a result, the conductivity is increased, but the permeation of hydrogen, which is a fuel gas, and oxygen, which is an oxidant gas, is also increased, and the gas reacts directly through the electrolyte 1 to reduce current efficiency. .

  In the present invention, the property which can be said to be the conventional defect is used in reverse, and oxygen which oxidizes and deteriorates the cathode 22 at the time of starting and stopping is directly reacted with hydrogen leaking through the electrolyte 1 to efficiently remove and activate. Thus, the durability of the fuel cell power generator is improved. Further, the cathode 22 largely dominates the battery performance. In particular, the battery performance can be improved by activating the cathode 22.

  The anode 21 and the cathode 22 have a catalyst layer made of a mixture of a catalyst in which a noble metal such as platinum is supported on porous carbon and a polymer electrolyte having hydrogen ion conductivity, and air permeability and electronic conductivity laminated on the catalyst layer. It consists of a gas diffusion layer having properties. For the anode 21, an alloy catalyst such as platinum-ruthenium having CO resistance was used. Moreover, carbon paper or carbon cloth subjected to water repellent treatment was used for the gas diffusion layer.

  Gaskets 31 and 32 for preventing gas mixing and leakage are disposed around the anode 21 and the cathode 22, respectively, and further, a gas flow path for supplying and discharging fuel gas and oxidant gas to the anode 21 and cathode 22, respectively. The conductive separator plates 41 and 42 having n The voltage generated by the single cell configured as described above is about 0.75 V, and a plurality of single cells corresponding to the required voltage can be stacked in series to form a stack.

  In addition, current collector plates, insulating plates, and end plates were disposed at both ends of the separator plates 41 and 42, and fixed with fastening rods. And the electronic load 8 and the voltage detection part 9 were connected to the current collection board, and the voltage of the fuel cell 5 when a fixed electric current was sent was detected.

  In FIG. 1, 6 is a desulfurization part and can adsorb and remove (desulfurize) a sulfur compound contained as a odorant in the raw material gas. In this example, city gas 13A mainly composed of methane, ethane, propane and butane was used as a raw material gas. The desulfurized raw material gas is supplied to the fuel processing unit 7 together with water, and a fuel gas containing hydrogen is generated by a reforming reaction. The fuel processing unit 7 includes a reforming unit 71 that reforms methane and the like, a CO conversion unit 72 that converts generated CO, and a CO removal unit 73 that removes CO.

  The generated fuel gas is supplied to the anode 21 of the fuel cell 5 at a predetermined flow rate by the flow rate control unit 101. The oxidant gas is taken in from the atmosphere by a fan or the like, and is supplied to the cathode 22 of the fuel cell 5 by the flow rate control unit 102 at a predetermined flow rate. Further, fuel gas and oxidant gas were supplied after being humidified so as not to dry the membrane.

  Reference numeral 11 denotes a switching valve, which can switch the flow path so that the desulfurized source gas is supplied to the fuel processing unit 7 during power generation, and is supplied to the anode 21 and the cathode 22 of the fuel cell 5 when stopped. When the operation is stopped, the source gas is supplied to the anode 21 and the cathode at a predetermined flow rate by the flow rate control units 101 and 102, respectively. In addition, after supplying a predetermined volume, shut-off valves 121a, 121b, 122a, and 122b were provided in the supply section and the discharge section of the gas flow paths of the anode 21 and the cathode 22, respectively, in order to enclose the substituted source gas. The shut-off valves 121a and 122a on the gas channel supply section side are provided upstream of the flow control sections 101 and 102, respectively, and are supplied from the fuel processing section 7 during power generation and supplied from the desulfurization section 6 during stoppage. It was also used as a switching valve for switching the flow path of the desulfurized source gas.

  The desulfurization unit 6, the switching valve 11, the flow rate control units 101 and 102, the shut-off valves 121 a, 121 b, 122 a and 122 b, and the pipes and gas passages connecting these are used as gas replacement units.

  Using the fuel cell power generator configured as described above, an operation method was investigated in which the raw gas desulfurized on both the anode 21 and the cathode 22 was purged at the time of stopping and starting, and the remaining fuel gas and oxidant gas were respectively replaced.

First, a predetermined amount of fuel gas is supplied to the anode 21 and oxidant gas is supplied to the cathode 22 so that the cell temperature is about 70 ° C., the fuel gas utilization rate is about 75%, and the oxidant gas utilization rate is about 40%. A constant current of about 0.2 A / cm ² was applied to the substrate. At this time, the battery voltage detected by the voltage detector 9 connected to the fuel cell 5 was about 0.75V. The fuel gas and the oxidant gas were supplied after being humidified so that the dew points were 65 ° C. and 70 ° C., respectively.

  FIG. 2 is a flowchart of the driving method 1. When the fuel cell 5 was stopped, the electronic load 8 was first stopped (STEP 1), and the supply of fuel gas and oxidant gas was stopped simultaneously (STEP 2). Subsequently, the fuel gas and oxidant gas remaining in the fuel cell 5 are replaced with an inert gas (STEP 3), the shut-off valves 121a, 121b, 122a and 122b are closed, and the inert gas is sealed in the fuel cell 5 ( (Step 4).

  In this example, a raw material gas desulfurized to an inert gas was used. By using desulfurized source gas, it is possible to use infrastructure such as city gas, eliminating the need for gas cylinders such as nitrogen, not only miniaturizing equipment, but also greatly reducing maintenance and costs required for cylinder replacement, etc. Can do.

  Further, by substituting with the desulfurized raw material gas, it is possible to reduce or remove oxygen and oxidizing species that cause oxidative degradation by adsorbing to noble metals such as platinum contained in the anode 21 and the cathode 22. The durability of the power generation device can be improved.

  In addition, after replacing the fuel gas and the oxidant gas, the shutoff valves 121a, 121b, 122a and 122b are closed, and the raw material gas is sealed in the fuel cell 5, so that air (oxygen) diffused from the outside is used. Oxidation of the anode 21 and the cathode 22 and drying of the electrolyte 1 can be suppressed, contamination of impurities and the like can be prevented, and the durability of the fuel cell power generator can be improved.

Since the inert gas (raw material gas) that replaces the fuel gas and the oxidant gas remaining in the fuel cell is supplied without being humidified, its volume is kept to a minimum so that the electrolyte 1 membrane is not dried. Assuming that the concentration of the fuel gas or oxidant gas existing in each gas flow path before replacement is C ₀ and the volume of the gas flow path is V, when ΔV is allowed to flow during the time Δt, Δt The concentration C _t1 is expressed by (Equation 1).

Further, the density C _t2 after Δt is expressed by (Equation 2).

Therefore, the concentration C _tn after nΔt is expressed by (Equation 3).

  At this time, assuming that the inert gas flows k times the volume V of the gas flow path, (Equation 4) holds.

  Therefore, (Equation 3) is expressed by (Equation 5).

  Using the binomial theorem and Taylor expansion, (Equation 6) can be derived from (Equation 5).

  According to (Equation 6), when the inert gas is flowed 2 to 5 times the volume of each gas flow path, the concentration of the fuel gas or oxidant gas to be replaced is about 14 to 0.7% of the initial concentration. Can be substituted.

  In the case of this example, the fuel gas and the oxidant gas remaining in each gas channel were replaced with an inert gas having a volume three times that of each gas channel. Since air was used as the oxidant gas, it was found that the oxygen concentration in the gas flow path on the cathode 22 side was reduced to only about 1%. Since the inert gas is sealed in this state, deterioration due to oxidation of the anode 21 and the cathode 22 can be suppressed.

  Further, since the gas is replaced with the minimum necessary volume, the influence on the moisture retention state of the electrolyte 1 can be reduced.

(Embodiment 2)
FIG. 3 is a flowchart of the driving method 2. When the fuel cell 5 was stopped, the electronic load 8 was first stopped (STEP 11), and the supply of fuel gas and oxidant gas was stopped simultaneously (STEP 12). As a result, hydrogen in the anode 21 diffuses to the cathode 22 through the electrolyte 1, reacts with oxygen to generate water, and consumes oxygen in the cathode 22, so that the voltage of the fuel cell 5 gradually decreases. When the voltage detector 9 detects that the voltage of the fuel cell 5 is equal to or lower than a predetermined voltage (STEP 13), the fuel gas and oxidant gas remaining in the fuel cell 5 are replaced with an inert gas (STEP 14), and the shut-off valve 121a 121b, 122a and 122b were closed, and an inert gas was sealed in the fuel cell 5 (STEP 15).

  The difference from the operation method 1 is that the anode 21 and the cathode 22 are replaced with an inert gas after the voltage of the fuel cell 5 is detected and lowered to a predetermined voltage.

  By simultaneously stopping the supply of the fuel gas and the oxidant gas, the hydrogen diffused from the anode 21 through the electrolyte 1 reduces the oxide film formed on the platinum surface of the cathode 22 and the impurities attached to the cathode 22. Therefore, the cathode 22 is activated, and the battery voltage that has been lowered due to these factors can be recovered at the time of startup.

  At this time, the voltage of the fuel cell 5 finally decreases to 0 to 0.2 V, but in this embodiment, when the voltage drops to 0.2 V or less, it is replaced with an inert gas. By lowering the voltage to 0.2 V or less, the potential of the cathode 22 is lowered, and the platinum surface of the cathode 22 is sufficiently activated. Activation occurs even at a voltage higher than 0.2 V, but the higher the voltage, the weaker the activation effect and the smaller the voltage recovered at startup.

  Further, when the anode 21 in which hydrogen remains is used as a reference, the potential of the cathode 22 can be estimated from the voltage detected by the voltage detector 9. When the cathode 22 is activated by the hydrogen diffused from the anode 21, the potential of the cathode 22 is lowered. Therefore, the activation state of the cathode 22 can be known from the voltage detected by the voltage detection unit 9 and detected. By activating with voltage, the battery voltage at the time of start-up can be stabilized.

  Further, since the fuel gas and the oxidant gas remaining in the fuel cell 5 are replaced with an inert gas after the voltage of the fuel cell 5 is lowered to a predetermined voltage, deterioration due to oxidation of the anode 21 and the cathode 22 is suppressed. The durability of the fuel cell power generator can be improved.

  The battery voltage is an open circuit voltage from when the electronic load 8 is stopped until the gas supplied to the anode 21 and the cathode 22 is stopped. At this time, the open circuit voltage is 0.9 V or more, and the potential of the cathode 22 is exposed to a high potential. When the potential of the cathode 22 exceeds 0.9V, the catalytic reaction area decreases due to elution and sintering of platinum, and the reaction area decreases due to platinum oxidation and adsorption of oxidizing species. Until the gas supplied to the anode 21 and the cathode 22 is stopped as much as possible to shorten the time for maintaining the open circuit voltage, or when the electronic load 8 is stopped, so that the open circuit voltage is not generated. It is preferable to reduce the voltage by passing a current through a resistor or the like.

  When the gas supplied to the anode 21 is stopped earlier than the cathode 22, the potential of the anode 21 rises due to oxygen diffused and transmitted from the cathode 22. When the potential of the anode is exposed to a high potential, ruthenium contained in the catalyst is eluted, and CO poisoning performance is lowered. Therefore, the cathode 22 is connected simultaneously with the cathode 22 or the cathode 22 so that the potential of the anode 21 does not increase. It is preferable to stop the anode after stopping.

(Embodiment 3)
FIG. 4 is a flowchart of the driving method 3. When the fuel cell 5 was stopped, the electronic load 8 was first stopped (STEP 21), and the supply of the oxidant gas was stopped while the fuel gas was being supplied (STEP 22). As a result, hydrogen in the anode 21 diffuses to the cathode 22 through the electrolyte 1, reacts with oxygen to generate water, and consumes oxygen in the cathode 22, so that the voltage of the fuel cell 5 gradually decreases. When the voltage detector 9 detects that the voltage of the fuel cell 5 is equal to or lower than the predetermined voltage (STEP 23), the supply of the fuel gas is stopped (STEP 24), and the fuel gas and oxidant gas remaining in the fuel cell 5 are inert gas. (STEP 25), the shut-off valves 121a, 121b, 122a and 122b were closed, and an inert gas was sealed in the fuel cell 5 (STEP 26).

  The difference from the operation method 2 is that the oxidant gas is first stopped, the voltage of the fuel cell 5 is lowered to a predetermined voltage, the fuel gas is stopped, and finally the anode 21 and the cathode 22 are replaced with an inert gas. It is a point to do.

  By stopping the supply of the oxidant gas while supplying the fuel gas, even if hydrogen permeates to the cathode 21 due to diffusion, hydrogen continues to be supplied to the anode 21, so that the reference potential of the anode 21 is stabilized and the cathode The electric potential of 22 falls faster than the operation method 2, and the cathode 22 can be activated more.

  In addition, since the potential of the cathode 22 quickly decreases, the time for which the cathode 22 is held at a high potential such as an open circuit voltage can be shortened, and deterioration of the cathode 22 can be suppressed.

(Embodiment 4)
FIG. 5 is a flowchart of the driving method 4. When the fuel cell 5 was stopped, first, the electronic load 8 was stopped (STEP 31), and the supply of the oxidant gas was stopped while supplying the fuel gas (STEP 32). Next, the supply of the oxidant gas was stopped, and at the same time, an inert gas was supplied to the cathode 22 side, and the oxidant gas remaining on the cathode 22 was replaced with the inert gas (STEP 33).

  As a result, hydrogen in the anode 21 diffuses to the cathode 22 through the electrolyte 1, reacts with oxygen to generate water, and consumes oxygen in the cathode 22, so that the voltage of the fuel cell 5 decreases instantaneously. When the voltage detector 9 detects that the voltage of the fuel cell 5 is equal to or lower than the predetermined voltage (STEP 34), the supply of the fuel gas is stopped (STEP 35), and the fuel gas remaining on the anode 21 is replaced with an inert gas (STEP 36). ), Shut-off valves 121a, 121b, 122a and 122b were closed, and an inert gas was sealed in the fuel cell 5 (STEP 37).

  The difference from the operation method 3 is that the oxidant gas is stopped and at the same time an inert gas is supplied to the cathode 22, the voltage of the fuel cell 5 is lowered to a predetermined voltage, the fuel gas is stopped, and finally the anode 21. Is replaced with an inert gas.

  By replacing the oxidant gas with an inert gas while supplying the fuel gas, the oxygen of the cathode 22 can be forcibly discharged, and the potential of the cathode 22 is lowered more quickly than in the operation method 3 and more active. It can be made. Moreover, since oxygen remaining in the gas diffusion layer or the like that cannot be replaced only by stopping the gas can be replaced, deterioration can be further suppressed.

(Embodiment 5)
FIG. 6 is a flowchart of the driving method 5. When the fuel cell 5 was stopped, the electronic load 8 was first stopped (STEP 41), and the supply of the oxidant gas was stopped while the fuel gas was being supplied (STEP 42). Next, the supply of the oxidant gas was stopped, and at the same time, an inert gas was supplied to the cathode 22 side, and the oxidant gas remaining on the cathode 22 was replaced with the inert gas (STEP 43).

  As a result, hydrogen in the anode 21 diffuses to the cathode 22 through the electrolyte 1, reacts with oxygen to generate water, and consumes oxygen in the cathode 22, so that the voltage of the fuel cell 5 decreases instantaneously. When the voltage detector 9 detects that the voltage of the fuel cell 5 is equal to or lower than the predetermined voltage (STEP 44), the supply of the fuel gas is stopped (STEP 45), and the fuel gas remaining on the anode 21 is replaced with an inert gas (STEP 46). ), Shut-off valves 121a, 121b, 122a and 122b were closed, and an inert gas was sealed in the fuel cell 5 (STEP 47).

  Then, immediately before the start of the fuel cell 5 (STEP 48), the shut-off valves 121a, 121b, 122a and 122b are opened (STEP 49), and a certain amount of inert gas is supplied to the anode 21 and the cathode 22 again to the minimum necessary (STEP 50). Then, fuel gas and oxidant gas were respectively supplied to the anode 21 and the cathode 22 (STEP 51), and the load was started (STEP 52).

  The difference from the operation method 4 is that the inert gas is again supplied to the anode 21 and the cathode immediately before the start of the fuel cell 5.

  By supplying an inert gas for a certain period of time immediately before start-up, oxygen that diffuses from the outside due to leakage or the like can be removed immediately before power generation in the event of long-term shutdown, further suppressing deterioration of the electrode due to oxygen Can do.

  In addition, if fuel gas is supplied in a state where oxygen is mixed into the anode 21, combustion or explosion may occur, and the oxygen that is the cause is eliminated immediately before the fuel gas is supplied, so that safety can be improved.

(Embodiment 6)
FIG. 7 is a flowchart of the driving method 6. When the fuel cell 5 was stopped, the electronic load 8 was first stopped (STEP 61), and the supply of the oxidant gas was stopped while the fuel gas was being supplied (STEP 62). Next, the supply of the oxidant gas was stopped, and at the same time, an inert gas was supplied to the cathode 22 side, and the oxidant gas remaining on the cathode 22 was replaced with the inert gas (STEP 63).

  As a result, hydrogen in the anode 21 diffuses to the cathode 22 through the electrolyte 1, reacts with oxygen to generate water, and consumes oxygen in the cathode 22, so that the voltage of the fuel cell 5 decreases instantaneously. When the voltage detector 9 detects that the voltage of the fuel cell 5 is equal to or lower than the predetermined voltage (STEP 64), the supply of the fuel gas is stopped (STEP 65), and the fuel gas remaining on the anode 21 is replaced with an inert gas (STEP 66). ), Shut-off valves 121a, 121b, 122a and 122b were closed, and an inert gas was sealed in the fuel cell 5 (STEP 67).

  Then, in order to remove air that is slightly mixed in due to leakage or the like at regular intervals (STEP 68), the shut-off valves 121a, 121b, 122a and 122b are opened (STEP 69), and the anode 21 and A certain amount of inert gas was supplied to the cathode 22 as much as necessary (STEP 70). Immediately before the start (STEP 71), fuel gas and oxidant gas were supplied to the anode 21 and the cathode 22, respectively (STEP 72), and the load was started (STEP 73).

  A difference from the operation method 4 is that an inert gas is periodically supplied to the anode 21 and the cathode for a certain period of time.

  By supplying an inert gas periodically for a certain period of time until startup, oxygen that diffuses from the outside due to leaks can be replaced periodically when it stops for a long time, and the electrode deteriorates due to oxygen. Can be further suppressed.

(Embodiment 7)
FIG. 8 is a flowchart of the driving method 7. When the fuel cell 5 was stopped, the electronic load 8 was first stopped (STEP 81), and the supply of the oxidant gas was stopped while supplying the fuel gas (STEP 82). As a result, hydrogen in the anode 21 diffuses to the cathode 22 through the electrolyte 1, reacts with oxygen to generate water, and consumes oxygen in the cathode 22, so that the voltage of the fuel cell 5 gradually decreases. When the voltage detector 9 detects that the voltage of the fuel cell 5 is equal to or lower than the predetermined voltage (STEP 83), the supply of the fuel gas is stopped (STEP 84).

  When the temperature of the fuel cell 5 becomes 30 ° C. or lower (STEP 85), the fuel gas and oxidant gas remaining in the fuel cell 5 are replaced with inert gas (STEP 86), and the shut-off valves 121a, 121b, 122a are replaced. And 122b were closed, and an inert gas was sealed in the fuel cell 5 (STEP 87).

  The difference from the operation method 3 is that the fuel gas and the oxidant gas remaining in the fuel cell 5 are replaced with an inert gas after the temperature of the fuel cell 5 falls below a predetermined temperature.

  By substituting after the temperature is lowered, even if impurities are contained in the inert gas, the reaction temperature is lowered to reduce the influence thereof, so that the durability can be further improved.

  INDUSTRIAL APPLICABILITY The fuel cell power generation device and the operation method thereof according to the present invention have an effect of suppressing deterioration due to start and stop or improving durability, and are useful for power generation devices and devices using a polymer solid electrolyte membrane.

  In addition, since a source gas such as city gas is used as the inert gas, it is also useful for a stationary fuel cell cogeneration system.

Configuration diagram of fuel cell power generator of the present invention Flow chart showing operation method 1 of the apparatus Flow chart showing operation method 2 of the apparatus Flow chart showing operation method 3 of the apparatus Flow chart showing operation method 4 of the apparatus Flow chart showing operation method 5 of the apparatus Flow chart showing operation method 6 of the apparatus Flow chart showing operation method 7 of the apparatus Configuration diagram of conventional fuel cell power generator

Explanation of symbols

1 Electrolyte 21 Electrode (Anode)
22 electrode (cathode)
41, 42 Separator plate 5 Fuel cell 6 Desulfurization unit 7 Fuel processing unit 9 Voltage detection unit 121a, 121b, 122a, 122b Shut-off valve

Claims (10)

A pair of electrodes having an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas flow path for supplying and discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying and discharging an oxidizing gas containing at least oxygen to the other of the electrodes A fuel cell comprising at least one cell comprising a separator plate, a desulfurization unit for desulfurizing a source gas, a fuel processing unit for generating the fuel gas from the desulfurized source gas, and the fuel when the fuel cell is stopped A fuel cell power generator comprising: a gas replacement unit that replaces all or part of the fuel gas remaining in the battery and the oxidant gas with the raw material gas that has been desulfurized. A fuel gas and an oxidant gas supply unit and a discharge unit are provided with a shutoff valve, the fuel gas and the oxidant gas are replaced with a desulfurized raw material gas, the shutoff valve is closed, and the desulfurized raw material gas is replaced with a fuel cell. The fuel cell power generator according to claim 1, which is enclosed in the inside. A pair of electrodes having an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas flow path for supplying and discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying and discharging an oxidizing gas containing at least oxygen to the other of the electrodes A fuel cell comprising at least one cell composed of a separator plate, and a gas that replaces all or part of the fuel gas and the oxidant gas remaining in the fuel cell with an inert gas when the fuel cell is stopped A replacement unit and a voltage detection unit for detecting the voltage of the fuel cell, and when the fuel cell is stopped, the supply of the fuel gas and the oxidant gas is stopped at the same time, and the voltage detection unit detects the voltage of the fuel cell. Is detected to be equal to or lower than a predetermined voltage, and all or part of the fuel gas and the oxidant gas remaining in the fuel cell are replaced with the inert gas. Way operation of the apparatus. A pair of electrodes having an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas flow path for supplying and discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying and discharging an oxidizing gas containing at least oxygen to the other of the electrodes A fuel cell comprising at least one cell composed of a separator plate, and a gas that replaces all or part of the fuel gas and the oxidant gas remaining in the fuel cell with an inert gas when the fuel cell is stopped A replacement unit; and a voltage detection unit that detects a voltage of the fuel cell, and when the fuel cell is stopped, the supply of the oxidant gas is stopped while the fuel gas is being supplied. Is detected to be equal to or lower than a predetermined voltage, the supply of the fuel gas is stopped, and all or part of the fuel gas and the oxidant gas remaining in the fuel cell are removed. Serial operating method of the fuel cell power plant replaced with an inert gas. A pair of electrodes having an electrolyte, a pair of electrodes sandwiching the electrolyte, and a gas flow path for supplying and discharging a fuel gas containing at least hydrogen to one of the electrodes and supplying and discharging an oxidizing gas containing at least oxygen to the other of the electrodes A fuel cell comprising at least one cell composed of a separator plate, and a gas that replaces all or part of the fuel gas and the oxidant gas remaining in the fuel cell with an inert gas when the fuel cell is stopped A replacement unit; and a voltage detection unit that detects a voltage of the fuel cell, and when the fuel cell is stopped, the supply of the oxidant gas is stopped while the fuel gas is being supplied, and the fuel cell remaining in the fuel cell After all or part of the oxidant gas is replaced with the inert gas, and the voltage detector detects that the voltage of the fuel cell is equal to or lower than a predetermined voltage, the supply of the fuel gas is stopped. And, operating method of the fuel cell power plant to replace all or part of the fuel gas remaining within the fuel cell in the inert gas. The fuel gas and oxidant gas supply section and discharge section are equipped with shut-off valves, and the fuel gas and oxidant gas remaining in the fuel cell are replaced with an inert gas 2 to 5 times the volume of each gas flow path. 6. The method of operating a fuel cell power generator according to claim 3, wherein the inert gas is sealed in the fuel cell until the shutoff valve is closed and started. The fuel gas and oxidant gas supply part and the discharge part are provided with shut-off valves, and after replacing all or part of the fuel gas and oxidant gas remaining in the fuel cell with an inert gas, the shut-off valve is The method for operating a fuel cell power generator according to any one of claims 3 to 5, wherein the shut-off valve is opened immediately before starting to close and the inert gas is supplied for a predetermined time. The fuel gas and oxidant gas supply part and the discharge part are provided with shut-off valves, and after replacing all or part of the fuel gas and oxidant gas remaining in the fuel cell with an inert gas, the shut-off valve is 6. The method of operating a fuel cell power generator according to claim 3, wherein the shut-off valve is periodically opened and the inert gas is supplied for a certain period of time until the valve is closed and activated. 6. The fuel cell according to claim 3, wherein after the temperature of the fuel cell becomes equal to or lower than a predetermined temperature, all or a part of the fuel gas and the oxidant gas remaining in the fuel cell are replaced with an inert gas. An operation method of the fuel cell power generator according to claim. The desulfurization part which desulfurizes raw material gas, and the fuel processing part which produces | generates fuel gas from the said desulfurized raw material gas, The said desulfurized raw material gas is used as inert gas of any one of Claims 3-9 Operation method of fuel cell power generator.

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