JP2016033863A - Fuel battery system and operation method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel battery system and an operation method for the same that enable impurities removing means to be used for a relatively long term and also can suppress reduction of the output of a fuel battery and deterioration of durability caused by impurities contained in gas for power generation.SOLUTION: Oxidant gas route switching means 611, 612 for switching a route passing through oxidant gas impurities removing means 41 and a bypass route 51 bypassing the oxidant gas impurities removing means 41 are provided. A controller 8 controls the oxidant gas route switching means 611, 612 so that the bypass route 51 is switched to the route passing through the oxidant gas impurities removing means 41 when an impurities supply amount determined by impurities supply amount determining means 7 exceeds a predetermined impurities supply amount.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system that suppresses a decrease in output and durability of a fuel cell due to impurities contained in power generation gas, and an operation method thereof.

  A fuel cell reacts with a fuel gas containing at least hydrogen and an oxidant gas containing at least oxygen to produce electricity and heat, and directly converts the chemical energy of the fuel into electric energy, thus obtaining high power generation efficiency. Can do.

  A fuel cell is composed of a cathode and an anode provided so as to sandwich a solid electrolyte membrane. By supplying an oxidant gas to the cathode oxidant gas flow path and a fuel gas to the anode fuel gas flow path, the fuel cell generates power. Is possible.

  The hydrogen supplied to the anode releases electrons, becomes hydrogen ions, moves through the electrolyte membrane having hydrogen ion conductivity, and moves to the cathode. The hydrogen ions that have moved to the cathode react with oxygen and electrons at the cathode to produce water.

  Moreover, in order to collect | recover the thermal energy generated at this time, it has the structure which distribute | circulates cooling water to the cooling water flow path of a fuel cell, and collect | recovers heat.

  By the way, when the oxidant gas supplied to the cathode or the fuel gas supplied to the anode contains impurities, the impurities poison the cathode or the anode catalyst, or hydrogen ions in the electrolyte membrane. There existed a subject that the output fall of a fuel cell and the fall of durability generate | occur | produced by inhibiting conductivity.

  Conventionally, in order to suppress a decrease in output or durability of the fuel cell due to impurities contained in the oxidant gas or in the fuel gas, an impurity removal means suitable for the impurity to be removed has been provided. The impurities contained in the fuel gas were removed and supplied.

  In general, a filter or the like is often used as the impurity removing means, and the impurities are removed by adsorption or separation with the filter.

  The atmosphere is often used as the oxidant gas supplied to the cathode, but the atmosphere contains various impurities that affect the output and durability of the fuel cell, such as nitrogen oxides, sulfur compounds, and dust. It can be removed with an acid gas removal filter, a dust removal filter, or the like (see, for example, Patent Document 1).

  On the other hand, for the fuel gas supplied to the anode, for example, hydrogen generated by reforming a hydrocarbon-based gas, which is a main component such as city gas, by a reforming reaction is used, but the raw material contains nitrogen. In some cases, ammonia is contained as an impurity in the fuel gas, and ammonia in the fuel gas is removed by an ammonia removing means or the like (see, for example, Patent Document 2).

  However, these impurity removal means are always small during operation because they are physically or chemically adsorbed and absorbed to remove impurities, have a short life, increase the frequency of replacement, and increase capacity. There was a problem that it was not economical and not economical.

Therefore, the conventional fuel cell system includes an impurity concentration detecting unit and a channel switching unit, and when the impurity concentration exceeds a predetermined value, the channel switching unit is configured to remove the impurity by the impurity removing unit. To suppress the consumption of the impurity removing means and extend the life (see, for example, Patent Document 3).

JP 2008-159281 A JP-A-6-84537 JP 2008-23497 A

  However, in the method using the impurity concentration detection means, it is necessary to attach an impurity concentration sensor in the middle of the gas path, which not only increases the size of the apparatus but also requires a plurality of impurity concentration sensors depending on the impurities to be removed. There was a problem that it was not economical.

  In addition, even if the concentration is low, impurities that affect the fuel cell by operating for a long time are difficult to detect with an impurity concentration sensor, and thus the impurities may not be removed.

  The present invention solves the above-described conventional problems, and without using an impurity concentration sensor, the impurity removing means can be used for a relatively long period of time, and the output of the fuel cell is reduced or the durability is deteriorated due to impurities contained in the power generation gas. It aims at providing the fuel cell system which suppressed the fall of property.

  In order to solve the above conventional problems, a fuel cell system according to the present invention includes a fuel cell, a gas supply means for supplying a power generation gas to the fuel cell, and an impurity removal means for removing impurities contained in the gas. A bypass path for bypassing the impurity removing means, a path switching means for switching between the bypass path and the bypass path, and a controller, and the controller performs a predetermined operation. Or when the condition for determining that the supply amount of the impurity exceeds a predetermined amount is satisfied, the gas supply path to the fuel cell is switched from the bypass path to the path via the impurity removal means. The path switching means is controlled.

  Thus, the impurity removing means can be used for a relatively long period of time without using an impurity concentration sensor, and it is possible to suppress a decrease in output and durability of the fuel cell due to impurities contained in the power generation gas.

  According to the present invention, the impurity removing means can be used for a relatively long period of time without using an impurity concentration sensor, and a decrease in output and durability of the fuel cell due to impurities contained in the power generation gas can be suppressed.

1 is a schematic configuration diagram of a fuel cell system according to Embodiment 1 of the present invention. The characteristic figure which shows the continuous power generation time dependence of the output fall rate of the fuel cell system of the embodiment Schematic configuration diagram of a fuel cell system in Embodiment 6 of the present invention Schematic configuration diagram of a fuel cell system in Embodiment 7 of the present invention Schematic configuration diagram of a fuel cell system in Embodiment 8 of the present invention The flowchart which shows an example of control operation of the fuel cell system of the embodiment Schematic configuration diagram of a fuel cell system according to Embodiment 9 of the present invention Schematic configuration diagram of a fuel cell system according to Embodiment 10 of the present invention

  According to a first aspect of the present invention, there is provided a fuel cell, a gas supply means for supplying a power generation gas to the fuel cell, an impurity removal means for removing impurities contained in the gas, and a bypass path for bypassing the impurity removal means And a path switching means for switching between the path through the impurity removal means and the bypass path, and a controller, and when the controller performs a predetermined operation, or the supply amount of the impurity is a predetermined amount. A fuel cell system that controls the path switching means so that the gas supply path to the fuel cell is switched from the bypass path to a path that passes through the impurity removal means when a condition that can be determined to be exceeded is satisfied; It is.

  The inventors of the present invention correlate the degree of influence of oxidant gas or impurities contained in fuel gas on the output and durability of the fuel cell with the supply amount of impurities (product of impurity concentration and supply time). Yes, the effect of impurities accumulated in the fuel cell can be eliminated to some extent by stopping and starting the fuel cell, and when the supply amount of impurities accumulated during power generation from start to stop is small, the output decreases for a longer time It has been found that power can be generated stably without affecting the durability.

  According to the configuration of the present invention, normally, when the supply amount of impurities is not more than a predetermined supply amount that does not affect the fuel cell, gas is supplied without removing the impurities by the impurity removing means, and the supply amount of impurities is the fuel cell. When the specified supply amount that affects the fuel is exceeded, the gas from which impurities are removed by the impurity removing means is supplied to reduce the influence on the fuel cell, so that the output of the fuel cell does not decrease for a longer time. Not only will it be possible to generate electricity stably, but only when the supply amount of impurities exceeds a predetermined supply amount that affects the fuel cell, impurities are removed by the impurity removal means and gas is supplied. Thus, the consumption of the impurity removing means can be suppressed, the life can be extended, and an economical fuel cell system with excellent performance and durability can be obtained.

  Moreover, when the controller performs a predetermined operation, the impurities are removed by the impurity removing means and gas is supplied, so that the consumption of the impurity removing means can be suppressed, the life can be extended, and the performance and durability are excellent. An economical fuel cell system can be obtained.

  In particular, in addition to the first invention, the second invention includes impurity supply amount determination means for determining the supply amount of the impurity, and the controller supplies the impurity supply amount determined by the impurity supply amount determination means. The path switching means is controlled so that the gas supply path to the fuel cell is switched from the bypass path to the path via the impurity removal means when a predetermined impurity supply amount is exceeded.

  According to the configuration of the present invention, normally, when the supply amount of impurities is not more than a predetermined supply amount that does not affect the fuel cell, gas is supplied without removing the impurities by the impurity removing means, and the supply amount of impurities is the fuel cell. When the specified supply amount that affects the fuel is exceeded, the gas from which impurities are removed by the impurity removing means is supplied to reduce the influence on the fuel cell, so that the output of the fuel cell does not decrease for a longer time. Not only will it be possible to generate electricity stably, but only when the supply amount of impurities exceeds a predetermined supply amount that affects the fuel cell, impurities are removed by the impurity removal means and gas is supplied. Thus, the consumption of the impurity removing means can be suppressed, the life can be extended, and an economical fuel cell system with excellent performance and durability can be obtained.

In particular, in addition to the first invention, the third invention includes continuous power generation time measuring means for measuring continuous power generation time in continuous power generation from start to next stop, and the controller includes the continuous power generation time measurement. When the continuous power generation time measured by the means exceeds a predetermined continuous power generation time, the path switching is performed so that the gas supply path to the fuel cell is switched from the bypass path to the path via the impurity removal means. Control the means.

  In general, the oxidant gas is often used in the atmosphere, but the average concentration of impurities in the atmosphere is stable within a certain range, and the average concentration of impurities in the fuel gas depends on the conditions of the reforming reaction. Therefore, it is estimated that the average supply amount of impurities contained in each gas supplied to the fuel cell per unit time is stable.

  According to the configuration of the present invention, the continuous power generation time measuring means estimates the supply amount of impurities that affect the fuel cell from the estimated average concentration of impurities and the continuous power generation time after startup, and the estimated supply amount of impurities. Measuring the power generation time exceeding the predetermined supply amount, and when the controller exceeds the predetermined continuous power generation time, the controller controls to switch the path switching means so as to remove the impurities by the impurity removal means. Therefore, it is possible to obtain an economical fuel cell system having excellent performance and durability.

  In particular, in addition to the first invention, the fourth invention includes a cumulative power generation amount measuring means for measuring a cumulative power generation amount in continuous power generation from the start to the next stop, and the controller includes the cumulative power generation. When the accumulated power generation amount measured by the power amount measuring means exceeds a predetermined power generation amount, the gas supply path to the fuel cell is switched from the bypass path to the path via the impurity removal means. In addition, the route switching means is controlled.

  The inventors of the present invention are that the current density of the current flowing through the fuel cell is higher, and the higher the amount of power, the greater the influence of impurities supplied to the fuel cell, and the lower the current density and the lower the amount of power, the impact on the fuel cell. And the cumulative amount of generated power (product of generated power and power generation time) was found to correlate with the amount of impurities supplied.

  According to the configuration of the present invention, the cumulative power generation amount measuring unit estimates the supply amount of impurities from the cumulative power generation amount of the fuel cell, measures the cumulative power amount in which the estimated supply amount of impurities exceeds a predetermined supply amount, Since the controller controls to switch the path switching means so as to remove impurities by the impurity removal means when the predetermined accumulated power generation amount is exceeded, the influence of impurities on the fuel cell can be mitigated, performance and It is possible to obtain a fuel cell system that is excellent in durability and economical.

  In particular, in addition to the first invention, the fifth invention includes an operation time measuring means for measuring the operation time of the gas supply means in continuous power generation from start to next stop, and the controller includes the operation When the operation time measured by the time measurement means exceeds a predetermined operation time, the path switching is performed so that the gas supply path to the fuel cell is switched from the bypass path to the path via the impurity removal means. Control the means.

  With this configuration, the supply path is arranged so that the amount of impurities supplied to the fuel cell is estimated from the operating time of the gas supply means for supplying the gas containing impurities, and the impurities are removed after a predetermined operating time. Since switching is performed, the influence of impurities on the fuel cell can be mitigated, and an economical fuel cell system having excellent performance and durability can be obtained.

  In particular, in addition to the first invention, the sixth invention further comprises cumulative gas supply amount measuring means for measuring the cumulative gas supply amount of the gas supply means in continuous power generation from start to next stop, and the controller However, when the cumulative gas supply amount measured by the cumulative gas supply amount measurement means exceeds a predetermined gas supply amount, the gas supply path to the fuel cell is routed from the bypass path through the impurity removal means. The route switching means is controlled to switch to the route to be performed.

  With this configuration, the supply amount of impurities accumulated in the fuel cell is estimated from the accumulated gas supply amount (product of gas supply speed and gas supply time), and impurities are removed only when the predetermined gas supply amount is exceeded. Thus, the gas supply path to the fuel cell can be switched.

  For example, when the gas supply amount is small, such as at high utilization or low output, the amount of supplied impurities is also small, so the fuel cell can generate power stably for a long time without removing impurities. For example, when the gas supply amount is large, such as at a low utilization rate or at a high output, the amount of impurities supplied is also large. Therefore, the impurity supply amount is reduced via the impurity removing means, and the gas is supplied to the fuel cell. The fuel cell system can be supplied and can generate power stably for a long time, and has an excellent performance and durability, and an economical fuel cell system can be obtained.

  In particular, in addition to the first invention, the seventh invention includes a power failure detection means for detecting a power failure, and the controller supplies the gas to the fuel cell when the power failure detection means detects a power failure. The path switching means is controlled so that the supply path is switched from the bypass path to the path passing through the impurity removing means.

  With this configuration, normally, when a power failure is detected during a power outage that requires power generation by supplying gas for power generation to the fuel cell through a bypass path that bypasses the impurity removal means, Since it is possible to generate power stably for a long time by removing impurities by switching to the route through the impurity removal means, an economical fuel cell system with excellent performance and durability even during a power outage can be obtained Is possible.

  According to an eighth aspect of the present invention, in particular, when the controller according to the first aspect of the present invention performs an activity recovery operation of the catalyst of the fuel cell, the gas supply path to the fuel cell is changed from the bypass path to the impurity. The route switching means is controlled so as to switch to a route passing through the removing means.

  When performing the activity recovery operation of the catalyst, the present inventors have a higher activity recovery effect due to the activity recovery operation when a gas with less impurities is used, and more effectively the activity reduced by the adsorption of impurities during normal power generation. I found out that it can be revived.

  Therefore, according to this configuration, when performing the activity recovery operation, gas without impurities is supplied through the path through the impurity removing means, so that the activity recovery effect by the activity recovery operation becomes higher, and the adsorption of impurities during normal power generation It is possible to restore the decreased activity with a high probability.

  In addition, since the gas passing through the bypass path that bypasses the impurity removal means is supplied to the fuel cell during normal power generation, the life of the impurity removal means can be extended.

  In the ninth invention, in particular, the activity recovery operation in the eighth invention includes an operation of increasing the amount of water in the catalyst of the fuel cell and an operation of increasing and decreasing the potential of the electrode of the fuel cell. It is characterized by at least one operation.

  In this activity recovery operation, the operation of increasing the amount of water in the catalyst can remove impurities adsorbed on the catalyst by dissolving them in water.

  Further, by increasing the potential of the fuel cell electrode, impurities adhering to the catalyst are oxidized, and the adsorption power with the catalyst can be weakened. By decreasing the potential of the fuel cell electrode, the catalyst Can be reduced and activated.

  In the tenth aspect of the invention, in particular, in the ninth aspect of the invention, the operation for increasing the amount of water in the catalyst of the fuel cell is the cooling operation of the fuel cell, the moisture per unit flow rate in the gas supplied to the fuel cell. It is at least one of an operation for increasing the amount and an operation for increasing the pressure of the gas supplied to the fuel cell.

  In the eleventh aspect of the invention, in particular, in the ninth aspect of the invention, the operation of raising and lowering the electrode potential of the fuel cell is connected to the fuel cell, the operation of applying a voltage from an external power source and sweeping the potential. An operation for controlling the size of the load, an operation for disconnecting and connecting the fuel cell and the load, an operation for flowing an inert gas to the fuel cell, and an operation for flowing an oxidant gas to the anode of the fuel cell, a cathode It is at least one of the operations of flowing the fuel gas through the fuel cell.

  In a twelfth aspect of the invention, in particular, the gas supply means in any one of the first to eleventh aspects of the invention is an oxidant gas supply means for supplying an oxidant gas to the fuel cell, and the impurity removal means is an oxidizer. The oxidant gas impurity removing means removes impurities contained in the oxidant gas.

  According to the configuration of the present invention, the supply amount that affects the fuel cell is obtained from the average concentration of the impurity in the oxidant gas and the supply time, which are assumed in advance, and the oxidant gas impurity removing means exceeds the predetermined supply amount. Impurities are present in the oxidant gas by removing impurities contained in the oxidant gas and mitigating the effects of fuel cell impurities, enabling the fuel cell to generate power continuously for a long time. Even so, it is possible to obtain an economical fuel cell system with excellent performance and durability.

  In a thirteenth aspect of the invention, in particular, the gas supply means in any one of the first to eleventh aspects of the invention is fuel gas supply means for supplying fuel gas to a fuel cell, and the impurity removal means is in fuel gas. It is a fuel gas impurity removal means which removes the impurity contained in this.

  According to the configuration of the present invention, the supply amount that affects the fuel cell is obtained from the average concentration of the impurities in the fuel gas and the supply time that are assumed in advance, and the fuel gas is removed by the fuel gas impurity removing means above the predetermined supply amount. The fuel cell is excellent in performance and durability because it removes impurities contained in it, mitigates the impact on the fuel cell, and enables the fuel cell to generate power continuously for a long time. A system can be obtained.

  The fourteenth invention is characterized in that, in particular, the impurity in any one of the first to thirteenth inventions contains at least one of a sulfur compound and ammonia.

  The inventors of the present invention have the characteristic that sulfur compounds such as sulfur dioxide in the atmosphere are adsorbed and accumulated on the cathode catalyst of the fuel cell. In addition, the accumulation can be eliminated to some extent by starting and stopping the fuel cell without affecting the durability, but the fuel cell is continuously generated for a long time, and the accumulated amount of impurities (supply amount) It has been found that when the value exceeds a predetermined value, it cannot be completely eliminated by a single start / stop, so that the output gradually decreases or the durability decreases.

In addition, ammonia produced as a by-product in the fuel gas has the property of accumulating in the electrolyte membrane or adsorbing and accumulating on the anode and cathode catalysts. The accumulation can be eliminated to some extent by stopping and starting the fuel cell without affecting the output and durability. However, the fuel cell is continuously generated for a long time and the accumulated amount of ammonia (supply) It has been found that when the amount is greater than or equal to a predetermined value, the output cannot be completely eliminated by a single start / stop, so that the output gradually decreases or the durability decreases.

  According to the configuration of the present invention, the respective supply amounts that affect the fuel cell are determined from the average concentration and supply time of the sulfur compound in the oxidant gas or the ammonia in the fuel gas, which are assumed in advance, and the predetermined supply Since the sulfur compound contained in the gas or ammonia is removed by the impurity removal means above the amount, the influence on the fuel cell is alleviated, and the fuel cell can continuously generate power stably for a long time. Thus, it is possible to obtain an economical fuel cell system having excellent performance and durability.

  According to a fifteenth aspect of the invention, in particular, the impurities adsorbed to the fuel cell according to any one of the first to fourteenth aspects are washed away by condensed water formed by condensation in the fuel cell when power generation is stopped. It is characterized by this.

  With this configuration, even when power generation gas is supplied to the fuel cell through a bypass path that bypasses the impurity removal means, the impurities accumulated in the electrode during power generation are reduced by the cell temperature of the fuel cell when power generation is stopped. Since it is washed away with the condensed water generated when it is lowered and excluded from the catalyst layer, a fuel cell system in which the output of the fuel cell is not lowered and the durability is not lowered can be obtained.

  According to a sixteenth aspect of the present invention, there is provided a gas supply means for supplying a power generation gas to the fuel cell, an impurity removal means for removing impurities contained in the gas, a bypass path for bypassing the impurity removal means, and the impurity removal An operation method of a fuel cell system comprising a path switching means for switching between a path that passes through the means and the bypass path, and usually supplies the power generation gas to the fuel cell using the bypass path. In continuous power generation from start to next stop, when the continuous power generation time exceeds a predetermined continuous power generation time, when the cumulative power generation amount exceeds a predetermined power generation amount, the operation time of the gas supply means is predetermined. When the operating time of the gas supply means is exceeded, when the cumulative gas supply amount of the gas supply means exceeds a predetermined gas supply amount, or when a power failure is detected, at least one of If, switching the path switching means to route via said impurity removing means from said bypass path, is an operating method of the fuel cell system.

  By this method, normally, if the supply amount of impurities does not affect the fuel cell, the gas is supplied without removing the impurities, and the supply amount of impurities affects the fuel cell. When the supply amount is exceeded, the gas from which impurities are removed is supplied to alleviate the effect on the fuel cell, so that the fuel cell can generate power stably for a long time without lowering its output. In addition, only when the supply amount of impurities exceeds a predetermined supply amount that affects the fuel cell, impurities are removed by the impurity removal means and gas is supplied, so that the consumption of the impurity removal means can be suppressed, It is possible to extend the life, and it is possible to obtain an economical operation method of the fuel cell system which is excellent in performance and durability.

  According to a seventeenth aspect of the present invention, there is provided a gas supply system for supplying a gas for power generation to a fuel cell, a gas supply means, an impurity removal means for removing impurities contained in the gas, and a bypass path for bypassing the impurity removal means And a path switching means for switching between the path through the impurity removal means and the bypass path, and normally the fuel cell is used for the power generation using the bypass path. In the fuel cell system operation method, when the gas is supplied and the activity recovery operation of the catalyst of the fuel cell is performed, the path switching unit is switched from the bypass path to the path via the impurity removal unit.

  When performing the activity recovery operation of the catalyst, the present inventors have a higher activity recovery effect due to the activity recovery operation when a gas with less impurities is used, and more effectively the activity reduced by the adsorption of impurities during normal power generation. I found out that it can be revived.

  Therefore, according to this configuration, when performing the activity recovery operation, gas without impurities is supplied through the path through the impurity removing means, so that the activity recovery effect by the activity recovery operation becomes higher, and the adsorption of impurities during normal power generation It is possible to restore the decreased activity with a high probability.

  In addition, since the gas passing through the bypass path that bypasses the impurity removal means is supplied to the fuel cell during normal power generation, the life of the impurity removal means can be extended.

  In an eighteenth aspect of the invention, in particular, in the seventeenth aspect of the invention, the gas supply system having the gas supply means, the impurity removal means, the bypass path, and the path switching means supplies an oxidant gas to the cathode of the fuel cell. It is characterized in that it is at least one of a supply oxidant gas supply system and a fuel gas supply system for supplying fuel gas to the anode of the fuel cell.

  Therefore, according to this configuration, when performing the activity recovery operation, an oxidant gas without impurities that has passed through the path that passes through the impurity removing means is supplied to the cathode of the fuel cell, or impurities that have passed through the path that passes through the impurity removing means. Since the hydrogen-containing gas without hydrogen is supplied to the anode of the fuel cell, the activity recovery effect due to the activity recovery operation becomes higher, and the activity reduced by the adsorption of impurities during normal power generation can be restored with a high probability.

  In addition, since the gas passing through the bypass path that bypasses the impurity removal means is supplied to the fuel cell during normal power generation, the life of the impurity removal means can be extended.

  In the nineteenth aspect of the invention, in particular, the activity recovery operation in the seventeenth or eighteenth aspects of the invention increases the amount of water in the catalyst of the fuel cell, and raises and lowers the potential of the electrode of the fuel cell. It is characterized in that it is at least one of the operations.

  In the twentieth aspect of the invention, in particular, in the nineteenth aspect of the invention, the operation of increasing the amount of water in the catalyst of the fuel cell is the cooling operation of the fuel cell, the moisture per unit flow rate in the gas supplied to the fuel cell. It is at least one of an operation for increasing the amount and an operation for increasing the pressure of the gas supplied to the fuel cell.

  In the twenty-first aspect, in particular, in the nineteenth aspect, the operation of raising and lowering the electrode potential of the fuel cell is connected to the fuel cell, the operation of applying a voltage from an external power source and sweeping the potential. An operation for controlling the size of the load, an operation for disconnecting and connecting the fuel cell and the load, an operation for flowing an inert gas to the fuel cell, and an operation for flowing an oxidant gas to the anode of the fuel cell, a cathode It is at least one of the operations of flowing the fuel gas through the fuel cell.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments described above.

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

The fuel cell system according to Embodiment 1 of the present invention includes a fuel cell 1, an oxidant gas supply means 2 for supplying an oxidant gas to the cathode of the fuel cell 1, and a fuel for supplying the fuel gas to the anode of the fuel cell 1. Without removing the impurities contained in the oxidant gas by bypassing the gas supply means 3, the oxidant gas impurity removal means 41 for removing the impurities contained in the oxidant gas, and the oxidant gas impurity removal means 41 A bypass path 51 for supplying an oxidant gas from the oxidant gas supply means 2 to the cathode, an oxidant gas path switching means 611 and 612 for switching a path through the oxidant gas impurity removing means 41 and a bypass path 51; The configuration includes an impurity supply amount determination means 7 for determining the supply amount of impurities contained in the oxidant gas, and a controller 8.

  The fuel cell 1 is composed of a stack in which a plurality of fuel cell cells composed of an electrolyte membrane made of a solid polymer electrolyte having hydrogen ion conductivity and a cathode and an anode provided so as to sandwich the electrolyte membrane are stacked and fastened. Is done.

  The cathode is formed on one surface of the electrolyte membrane with a size of 15 cm × 15 cm, and is laminated on the catalyst layer composed of carbon carrying platinum particles and a polymer electrolyte having hydrogen ion conductivity. And a conductive gas diffusion layer made of carbon and fluororesin.

  The anode is formed on the other surface of the electrolyte membrane in the same size of 15 cm × 15 cm so as to face the cathode, and is made of carbon carrying platinum ruthenium alloy particles and a polymer electrolyte having hydrogen ion conductivity. It comprises a catalyst layer and a conductive gas diffusion layer made of carbon and a fluororesin and disposed so as to be laminated on the catalyst layer.

  The electrolyte membrane in which the cathode and the anode are formed is fixed to a resin frame, and the frame is further provided with an oxidant gas channel for supplying an oxidant gas and a fuel gas channel for supplying a fuel gas. A fuel battery cell is configured by being sandwiched between a pair of flat plate separators formed of carbon and resin.

  Here, the materials constituting the electrolyte membrane, the cathode, and the anode are not limited to the materials described above, and are preferably selected as appropriate according to operating conditions and the like.

  The oxidant gas supply means 2 is configured to use air as the oxidant gas and supply an oxidant gas containing at least oxygen to the cathode of the fuel cell 1 with a blower or a pump. Furthermore, in order to adjust the dew point of the oxidant gas to be supplied, a humidifier for total heat exchange with the off-oxidant gas discharged from the cathode outlet was provided.

  The fuel gas supply means 3 is configured to supply a fuel gas containing at least hydrogen to the anode by using a hydrocarbon gas such as city gas as a raw material gas and subjecting the raw material gas to a reforming reaction with water vapor.

  In addition, when the raw material gas contains an odorant such as a sulfur compound such as city gas, it is provided with a desulfurizer and further contained in the fuel gas after the reforming reaction that poisons the anode. In order to reduce the influence of carbon oxide, a reforming section and a selective oxidation section are provided after the reforming reaction to reduce the concentration of carbon monoxide to a concentration that does not affect the anode catalyst.

  Further, if necessary, air can be added to the anode (air bleeding) to further reduce the influence of carbon monoxide.

Here, in the atmosphere used as the oxidant gas, in addition to nitrogen oxides and sulfur oxides derived from combustion exhaust gas discharged from automobiles, factories, or household combustion appliances, unburned hydrocarbons and , Volatile organic compounds, impurities such as ammonia and hydrogen sulfide, and other impurities such as particulate matter such as dust may be included, and these impurities include sulfur compounds. Also included are those that poison the cathode catalyst of the fuel cell 1 and have adverse effects such as reduced output and reduced durability.

  The oxidant gas impurity removal means 41 is configured to be able to remove the various impurities described above that are included in the oxidant gas and adversely affect the fuel cell 1, and includes an acid gas filter, an alkaline gas filter, and a dust removal filter. ing.

  As the impurity supply amount determination unit 7 of the first embodiment, a continuous power generation time measuring unit that measures a continuous power generation time in continuous power generation from start to next stop can be used.

  When the continuous power generation time measuring means is used, the controller 8 bypasses the oxidant gas path switching means 611 and 612 when the continuous power generation time measured by the continuous power generation time measuring means exceeds a predetermined continuous power generation time. Control can be made so that the path 51 is switched to a path via the oxidant gas impurity removing means 41.

  With the configuration of the present embodiment, the continuous power generation time measuring means estimates the supply amount of impurities that affect the fuel cell 1 from the continuous power generation time after startup, and the estimated supply amount of impurities is a predetermined supply. The power generation time exceeding the amount is measured, and the controller 8 controls to switch the oxidant gas path switching means 611 and 612 so that the oxidant gas impurity removal means 41 removes impurities when the predetermined continuous power generation time is exceeded. can do.

  Using the fuel cell system configured as described above, a power generation test was conducted in the case where impurities contained in the oxidant gas that could accumulate on the cathode catalyst of the fuel cell 1 and affect the output and durability were present. .

  Sulfur dioxide was used as an impurity to be added to the oxidant gas, and the addition concentration thereof was about 5 ppb, which is a general atmospheric level with respect to the oxidant gas.

  Fuel gas is supplied to the anode so that the hydrogen utilization rate is 70%, air containing sulfur dioxide as an impurity is supplied to the cathode so that the oxygen utilization rate is 50%, and the current flowing through the fuel cell 1 is gradually increased. The power generation was started so that the output of the fuel cell system would be 750 W.

The current density flowing through the fuel cell 1 at this time was about 0.2 A / cm ² , the anode dew point was about 65 ° C., the cathode dew point was about 65 ° C., and the average temperature of the fuel cell 1 was stable at about 65 ° C. . And power generation was stopped when the continuous power generation time after starting passed 20 hours. At this time, the single cell voltage of the fuel cell 1 once increased to about 1V and then gradually decreased to about 0V.

  At this time, the average temperature of the fuel cell 1 decreased from about 65 ° C. to 40 ° C. or less when stopped. In this test, the operation of the oxidant gas path switching means 611 and 612 was temporarily stopped so that the oxidant gas was circulated only to the bypass path 51 in order to investigate the limit supply amount of impurities.

  Then, power generation was started again 4 hours after the power generation was stopped, and this series of starting and stopping cycles was repeated five times. At this time, the slope of the voltage value immediately before the stop (voltage drop rate) was approximately 0 μV / h, no significant output drop was observed, and it was confirmed that there was no problem in repeated durability.

  Next, the power generation time is extended so that the continuous power generation time after starting is 40, 60, 100, and 140 hours, the power generation is performed in the same manner, and the power generation is stopped after each continuous power generation time elapses. After a while, power generation was started again.

  This series of start-up and stop cycles was repeated 5 times, and the voltage drop rate at the time when 20 hours of continuous power generation after each start-up was obtained was determined. The test results are shown in FIG.

  From FIG. 2, the voltage drop rate was about 0 μV / h until the continuous power generation time was 60 hours. However, when the continuous power generation time is longer than that, the voltage drop rate tends to increase, that is, the continuous power generation time. It was suggested that when the length is longer, the voltage gradually decreases and the durability becomes shorter.

  From the above results, if the continuous power generation time is 60 hours or less, it is estimated that the accumulation of impurities is eliminated and the output is not lowered and the durability is not lowered by a single start / stop without removing the impurities. However, if the continuous power generation time is longer than 60 hours, if the impurities are not removed, all of the accumulated amount of impurities is not eliminated by a single start and stop. The longer the continuous power generation time, the more the accumulated amount of impurities. It has been found that it may increase gradually and affect output and durability.

  Next, the operation of the oxidant gas path switching means 611, 612, which has been temporarily stopped, is returned to the normal state, and the continuous power generation time measured by the continuous power generation time measurement means becomes the upper limit supply amount of sulfur dioxide in the atmosphere. When the corresponding 60 hours have been exceeded, the controller 8 switches the supply path with the oxidant gas path switching means 611, 612, and the oxidant gas impurity removal means 41 removes sulfur dioxide. When tests were conducted when the power generation time was 100 and 140 hours, the oxidant gas impurity removal means was connected from the bypass path 51 to the oxidant gas supply path when the continuous power generation time after starting exceeded 60 hours. There was a tendency to switch to a route via 41 and recover from the decrease in output.

  At this time, it was confirmed that the output decrease rate after 20 hours from the start was about 0 μV / h as shown in FIG.

  Next, a similar test was conducted for impurities such as nitrogen oxides, ammonia, and volatile organic compounds that may be contained in the atmosphere other than sulfur compounds such as sulfur dioxide. Although the output is temporarily reduced, the behavior of accumulating in the fuel cell 1 like sulfur dioxide is not seen, and the output reduction due to these impurities is reversibly and quickly recovered, and the durability is significantly affected. It was found that the output reduction rate was 0 μV / h.

  In other words, it was confirmed that sulfur dioxide is the main impurity that affects durability in general air.

  By the way, the average concentration of sulfur dioxide in the general atmosphere is stable at several ppb to 5 ppb, and the average supply amount of sulfur dioxide contained in the actual oxidant gas supplied to the fuel cell 1 per unit time is Estimated to be stable.

The continuous power generation time measuring means of the first embodiment estimates the supply amount of impurities that affect the fuel cell 1 from the continuous power generation time after startup, and the estimated supply amount of impurities is a predetermined supply amount ( For example, in the case of sulfur dioxide, it is configured to measure a continuous power generation time (for example, 60 hours in the case of sulfur dioxide) that exceeds 60 h at 5 ppb, and the controller 8 has a predetermined continuous power generation time (for example, carbon dioxide). In the case of sulfur, since it is controlled to switch the oxidant gas path switching means 611 and 612 so that impurities are removed by the oxidant gas impurity removal means 41 when it exceeds 60 hours), the influence of sulfur dioxide on the fuel cell 1 It was found that power generation can be stably performed without reducing the output for a long time.

  The supply limit of impurities, that is, the predetermined power generation time measured by the continuous power generation time measurement time is the material such as current density, operating conditions such as gas dew point, catalyst amount, gas permeability of gas diffusion layer, etc. Since it depends on the conditions and the type and concentration of impurities, it is preferable to experimentally simulate the environment in which the fuel cell system is installed in advance and obtain the estimated supply limit of impurities.

  Further, the impurities adsorbed on the fuel cell 1 of the first embodiment are washed away by the condensed water formed by condensation in the fuel cell 1 when power generation is stopped.

  With this configuration, even when power is generated using the bypass path 51 that bypasses the oxidant gas impurity removing means 41, the impurities accumulated in the electrodes during power generation are reduced when the battery temperature of the fuel cell 1 decreases when power generation is stopped. Since it is washed away with the generated condensed water and excluded from the catalyst layer, a fuel cell system in which the output of the fuel cell 1 is not lowered and the durability is not lowered can be obtained.

(Embodiment 2)
In the configuration of the fuel cell system of Embodiment 1, the fuel cell system of Embodiment 2 of the present invention measures the accumulated power generation amount in continuous power generation from start to next stop as the impurity supply amount determination means 7. When the accumulated power generation amount measured by the accumulated power generation amount measuring unit exceeds a predetermined amount of generated power, the oxidant gas path switching unit 611 is used. , 612 is controlled to be switched from the bypass path 51 to the path via the oxidant gas impurity removing means 41. The other configuration is the same as that of the first embodiment, and detailed description thereof is omitted.

  Using the fuel cell system configured as described above, in the same manner as in the first embodiment, the presence of impurities in the oxidant gas that may accumulate on the cathode catalyst of the fuel cell 1 and affect the output and durability. Below, the generated power was changed and the power generation test was carried out.

  Sulfur dioxide was used as an impurity to be added to the oxidant gas, and the addition concentration was adjusted to be about 5 ppb of the general atmospheric level with respect to the oxidant gas.

Fuel gas is supplied to the anode so that the hydrogen utilization rate is 70% and the gas dew point is 65 ° C., and the cathode contains sulfur dioxide as an impurity so that the oxygen utilization rate is 50% and the gas dew point is 65 ° C. When air is supplied and the current flowing through the fuel cell 1 is gradually increased, the current densities at 500 W and 250 W are about 0.13 A / cm ² and about 0.07 A / cm ² , respectively. The output behavior of was investigated.

  The cycle of generating and stopping after changing the continuous power generation time after starting was repeated 5 times, and the relationship between the voltage drop rate and the continuous power generation time was examined in the same manner as in the first embodiment. The continuous power generation time was 60 hours, whereas the upper limit of the continuous power generation time at 500 W and 250 W was about 90 hours and about 180 hours, respectively.

  Here, the supply amount of sulfur dioxide supplied to the fuel cell 1 within each power generation time was about 0.8 cc, and it was found that the supply amount was the same.

That is, the output and durability of the fuel cell 1 can be explained by the accumulated exposure amount of impurities, and the supply amount of impurities correlates with the cumulative amount of generated power (product of generated power and generated time). Thus, according to the configuration of the second embodiment, the accumulated power generation amount measuring unit estimates the supply amount of impurities from the accumulated power generation amount of the fuel cell 1, and the estimated supply amount of impurities is a predetermined supply. The accumulated electric energy exceeding the amount is measured, and the controller 8 switches the oxidant gas path switching means 611 and 612 so that the oxidant gas impurity removing means 41 removes impurities when the predetermined accumulated generated electric energy is exceeded. Therefore, even when the generated power is high, the influence of impurities on the fuel cell 1 can be mitigated, and stable power generation can be achieved without a decrease in output for a long time.

(Embodiment 3)
The fuel cell system according to Embodiment 3 of the present invention is the same as that of the fuel cell system according to Embodiment 1, except that the oxidant gas supply means 2 in the continuous power generation from the start to the next stop is used as the impurity supply amount determination means 7. The operation time measuring means for measuring the operation time is used, and when the controller 8 has exceeded the predetermined operation time, the oxidant gas path switching means 611, 612 is measured. Is different from the first embodiment in that control is switched from the bypass path 51 to the path via the oxidant gas impurity removing means 41. The other configuration is the same as that of the first embodiment, and detailed description thereof is omitted.

  With this configuration, the amount of impurities supplied to the fuel cell 1 is estimated from the operating time of the oxidant gas supply means 2 for supplying the oxidant gas containing impurities, and the impurities are removed after a predetermined operating time. Thus, since the supply path is switched, the influence of impurities on the fuel cell 1 can be mitigated, and an economical fuel cell system having excellent performance and durability can be obtained.

(Embodiment 4)
The fuel cell system according to Embodiment 4 of the present invention is the same as that of the fuel cell system according to Embodiment 1, except that the oxidant gas supply means 2 in the continuous power generation from the start to the next stop is used as the impurity supply amount determination means 7. The cumulative oxidant gas supply amount measuring means for measuring the cumulative oxidant gas supply amount is used, and the controller 8 determines that the cumulative oxidant gas supply amount measured by the cumulative oxidant gas supply amount measurement means is a predetermined oxidation. The point that the oxidant gas path switching means 611 and 612 is controlled to be switched from the bypass path 51 to the path via the oxidant gas impurity removing means 41 when the amount of the oxidant gas supply is exceeded is different from the first embodiment. The other configuration is the same as that of the first embodiment, and detailed description thereof is omitted.

  With this configuration, the supply amount of impurities accumulated in the fuel cell 1 is estimated from the accumulated oxidant gas supply amount (product of the oxidant gas supply rate and the oxidant gas supply time), and exceeds a predetermined oxidant gas supply amount. Only in some cases can it be switched to remove impurities.

  For example, when the supply amount of oxidant gas is small, such as when the utilization rate is low or when the output is low, the supply amount of impurities is also small. Therefore, the fuel cell 1 stably generates power for a long time without removing impurities. For example, when the supply amount of oxidant gas is large, such as when the utilization rate is low or when the output is high, the supply amount of impurities is also large. Thus, it is possible to supply an oxidant gas to the fuel cell 1 and generate power stably for a long time, and it is possible to obtain an economical fuel cell system with excellent performance and durability.

(Embodiment 5)
The fuel cell system according to the fifth embodiment of the present invention includes a power failure detection means for detecting a power failure in place of the impurity supply amount determination means 7 in the configuration of the fuel cell system according to the first embodiment. The difference from the first embodiment is that when the detection means detects a power failure, the oxidant gas path switching means 611 and 612 are controlled to be switched from the bypass path 51 to the path via the oxidant gas impurity removal means 41. The other configuration is the same as that of the first embodiment, and detailed description thereof is omitted.

  With this configuration, during a power failure that normally requires power generation using the bypass path 51 that bypasses the oxidant gas impurity removal unit 41 and continuously generates power for a long time, the power failure detection unit detects the power failure. Then, the oxidant gas impurity removing means 41 can be used to remove impurities to stably generate power for a long time, so that an economical fuel cell system is obtained that is excellent in performance and durability even during a power failure. It becomes possible.

(Embodiment 6)
The fuel cell system according to Embodiment 6 of the present invention is configured in the oxidant gas path from the oxidant gas supply means 2 to the fuel cell 1 as shown in FIG. The fuel gas from the fuel gas supply means 3 to the fuel cell 1 is not provided without the oxidant gas impurity removal means 41, the bypass path 51 that bypasses the oxidant gas impurity removal means 41, and the oxidant gas path switching means 611 and 612. A fuel gas impurity removing means 42 for removing impurities contained in the fuel gas in the path, and a fuel gas supply means for bypassing the fuel gas impurity removing means 42 to the anode without removing the impurities by the fuel gas impurity removing means 42 The fuel gas that switches between the bypass path 52 that supplies the fuel gas from the fuel cell 3, the path that passes through the fuel gas impurity removing means 42, and the bypass path 52. Path switching means 621 and 622, the impurity supply amount determination means 7 determines the supply amount of impurities contained in the fuel gas, and the controller 8 determines the supply amount of impurities determined by the impurity supply amount determination means 7 However, when a predetermined supply amount obtained experimentally in advance is exceeded, the fuel gas path switching means 621 and 622 are controlled to be switched from the bypass path 52 to the path via the fuel gas impurity removing means 42. This is different from Form 1. The other configuration is the same as that of the first embodiment, and detailed description thereof is omitted.

  Here, in the fuel gas, ammonia is contained as an impurity by reforming the raw material gas containing nitrogen. The ammonia concentration correlates with the nitrogen concentration contained in the source gas. When ammonia is supplied to the fuel cell 1, it combines with sulfonic acid groups in the electrolyte to lower the hydrogen ion conductivity, or the anode catalyst and ammonium ions that have moved through the electrolyte membrane poison the cathode catalyst. It has the characteristic to do.

  The fuel gas impurity removing means 42 is configured to remove ammonia contained in the fuel gas. For example, an ammonia absorbing solution such as water is circulated on one side of the polymer electrolyte membrane and ammonia is contained on the other side. The thing of the structure which laminated | stacked the thing of the structure which distribute | circulates fuel gas can be used.

  When the ammonia is less than a predetermined accumulation amount, the inventors do not significantly reduce the output of the fuel cell 1 and do not affect the durability. However, if the fuel cell 1 generates power continuously for a long time and the ammonia accumulation amount (supply amount) exceeds a predetermined value, it cannot be completely eliminated by a single start / stop. It was found that the output gradually decreases and the durability decreases.

  With the configuration of the sixth embodiment, the supply amount that affects the fuel cell 1 is experimentally determined in the same manner as in the first embodiment from the average concentration of ammonia in the fuel gas assumed in advance and the supply time. The ammonia contained in the fuel gas is removed by the fuel gas impurity removing means 42 at a predetermined supply amount or more, and the influence on the fuel cell 1 can be mitigated.

In addition, as implemented on the oxidant gas supply means 2 side, instead of the impurity supply amount determination means 7 of the sixth embodiment, continuous power generation time for measuring continuous power generation time in continuous power generation from start to next stop Measuring means, or cumulative power generation amount measuring means for measuring the cumulative power generation amount, or operating time measuring means for measuring the operating time of the fuel gas supply means 3; Either of the accumulated fuel gas supply amount measuring means or the power failure detection means for detecting a power failure can be selected and used, and both can obtain the same effect and correspond to a predetermined ammonia supply amount. The fuel gas impurity removing means 42 removes ammonia contained in the fuel gas above the threshold value, mitigates the influence on the fuel cell 1, and the fuel cell 1 continuously generates power stably for a long time. Since it allows excellent performance and durability, it is possible to obtain an economical fuel cell system.

(Embodiment 7)
The fuel cell system according to the seventh embodiment of the present invention is the same as the fuel cell system according to the first embodiment, as shown in FIG. The fuel gas impurity removing means 42 for removing impurities contained therein, and the fuel gas from the fuel gas supply means 3 to the anode without bypassing the fuel gas impurity removing means 42 and removing the impurities by the fuel gas impurity removing means 42 Fuel gas path switching means 621 and 622 for switching between the bypass path 52 and the path passing through the fuel gas impurity removing means 42, and the impurity supply amount determination means 7 is an oxidant gas or Of the impurities contained in the fuel gas, the supply amount of impurities that most affect the fuel cell 1 is determined, and the controller 8 determines the impurity supply amount. When the supply amount of impurities determined by the stage 7 exceeds a predetermined supply amount obtained experimentally in advance, the oxidant gas path switching means 611 and 612 are connected from the bypass path 51 to the oxidant gas impurity removal means 41. The configuration is such that control is performed so as to switch to a route that passes through, or control is performed so that the fuel gas route switching means 621, 622 is switched from the bypass route 52 to a route that passes through the fuel gas impurity removing means 42. Other configurations are the same as those in the first embodiment, and detailed description thereof is omitted.

  According to this configuration, normally, when the supply amount of impurities does not affect the fuel cell 1, the gas is supplied without removing the impurities, and the supply amount of impurities affects the fuel cell 1. When the supply amount exceeds the predetermined supply amount, the gas from which impurities are removed is supplied to alleviate the influence on the fuel cell 1, so that the fuel cell 1 can generate power stably for a long time without lowering the output. In addition, the oxidant gas impurity removing means 41 and the fuel gas impurity removing means 42 can remove impurities only when the supply amount of impurities exceeds a predetermined supply amount that affects the fuel cell 1. Since the gas is supplied after being removed, the consumption of the oxidant gas impurity removing means 41 and the fuel gas impurity removing means 42 can be suppressed, the life can be extended, and the fuel cell system has excellent performance and durability and is economical. It can be obtained operating method.

(Embodiment 8)
FIG. 5 is a schematic configuration diagram showing a fuel cell system according to Embodiment 8 of the present invention.

  The fuel cell 1 of the fuel cell system according to Embodiment 8 of the present invention includes a membrane electrode assembly (MEA) in which an anode and a cathode are formed to face each other on both surfaces of an electrolyte membrane.

  Here, the electrolyte is composed of a solid polymer electrolyte made of a perfluorocarbon sulfonic acid polymer having hydrogen ion conductivity, for example.

  In addition, the anode and the cathode were laminated on the catalyst layer, which includes a catalyst layer made of a mixture of a highly oxidation-resistant porous carbon supporting a noble metal such as platinum and a polymer electrolyte having hydrogen ion conductivity. It is composed of a gas diffusion layer having air permeability and electronic conductivity.

  At this time, a platinum-ruthenium alloy catalyst that suppresses poisoning by impurities contained in the fuel gas, particularly carbon monoxide, is generally used as the anode catalyst. As the gas diffusion layer, water-repellent carbon paper, carbon cloth, carbon nonwoven fabric, or the like is used.

  The anode-side separator and the cathode-side separator are arranged so as to face each other with the MEA interposed therebetween, and a fuel gas flow path for supplying and discharging fuel gas to the MEA-side surface of the anode-side separator is provided on the cathode-side separator. An oxidant gas flow path for supplying and discharging oxidant gas is formed on the MEA side surface.

  Here, the anode-side separator and the cathode-side separator are mainly formed of a conductive material such as carbon.

  The anode-side separator, the cathode-side separator, and the MEA are sealed by an anode-side gasket and a cathode-side gasket, respectively, so that the respective fluids do not leak to different fluid flow paths and the outside.

  The fuel cell stack (fuel cell 1) is configured by stacking a plurality of cells including the MEA having the above configuration and each separator.

  Here, the materials constituting the electrolyte membrane, the cathode, and the anode are not limited to the materials described above, and are preferably selected as appropriate according to operating conditions and the like.

  The fuel cell 1 is connected to a fuel gas supply means 3 for supplying a fuel gas containing hydrogen on the anode side and an oxidant gas supply means 2 for supplying an oxidant gas containing oxygen in the atmosphere to the cathode side. ing.

  The oxidant gas supply means 2 is configured to use air as the oxidant gas and supply an oxidant gas containing at least oxygen to the cathode of the fuel cell 1 with a blower or a pump. Furthermore, in order to adjust the dew point of the oxidant gas to be supplied, a humidifier for total heat exchange with the off-oxidant gas discharged from the cathode outlet was provided.

  The fuel gas supply means 3 is configured to supply a fuel gas containing at least hydrogen to the anode by using a hydrocarbon gas such as city gas as a raw material gas and subjecting the raw material gas to a reforming reaction with water vapor.

  In addition, when the raw material gas contains an odorant such as a sulfur compound such as city gas, it is provided with a desulfurizer and further contained in the fuel gas after the reforming reaction that poisons the anode. In order to reduce the influence of carbon oxide, a reforming section and a selective oxidation section are provided after the reforming reaction to reduce the concentration of carbon monoxide to a concentration that does not affect the anode catalyst.

  Further, if necessary, air can be added to the anode (air bleeding) to further reduce the influence of carbon monoxide.

  Here, in the atmosphere used as the oxidant gas, in addition to nitrogen oxides and sulfur oxides derived from combustion exhaust gas discharged from automobiles, factories, or household combustion appliances, unburned hydrocarbons and , Volatile organic compounds, impurities such as ammonia and hydrogen sulfide, and other impurities such as particulate matter such as dust may be included, and these impurities include sulfur compounds. Also included are those that poison the cathode catalyst of the fuel cell 1 and have adverse effects such as reduced output and reduced durability.

Further, the oxidant gas impurity removing means 41 includes a dust removing filter that removes dust in the atmosphere, and acid gas removal that removes sulfur-based impurities such as sulfur dioxide and hydrogen sulfide, and acid gases in the atmosphere such as nitrogen oxides. The filter and an alkaline gas removal filter that removes alkaline gas such as ammonia in the atmosphere. In the oxidant gas impurity removing means 41, each filter can be selected in accordance with the installation environment, the contamination resistance of the fuel cell 1, and the like.

  Further, the fuel cell 1 is provided with a voltage detector (not shown) for detecting the cell voltage of the fuel cell 1.

  An oxidant gas supply valve is provided in a pipe (oxidant gas supply path) connecting the oxidant gas supply means 2 and the fuel cell 1. The fuel cell 1 is connected to a pipe (oxidant gas discharge path) through which a gas such as an oxidant gas that has not been used at the cathode is discharged. The oxidant gas discharge path is connected to the oxidant gas. A discharge valve (not shown) is provided.

  With this configuration, by closing the oxidant gas supply valve and the oxidant gas discharge valve while the power generation of the fuel cell 1 is stopped, oxygen entering the cathode from the outside is shut off, and the oxygen concentration in the cathode is quickly reduced, The electrode potential of the cathode is quickly lowered to maintain a low potential. Therefore, the cathode catalyst can be efficiently reduced and activated.

  Further, the controller 8 can control the operation of the fuel cell 1 to start, generate power, and stop, and can control the operation of the internal load and the power output device. Further, the controller 8 operates the oxidant gas path switching means 611, 612 for switching between the path passing through the oxidant gas impurity removal means 41 and the bypass path 51 bypassing the oxidant gas impurity removal means 41, The oxidant gas supply path can be switched to the bypass path 51 during operation, and the oxidant gas supply path can be switched to the path via the oxidant gas impurity removing means 41 during start-up, stop, and activity recovery operations.

  Further, the controller 8 may be in any form as long as it is a device that controls each device constituting the fuel cell system, for example, an arithmetic processing unit exemplified by a microprocessor, a CPU, etc. A storage unit including a memory or the like that stores a program for executing a control operation is provided.

  Note that the controller 8 is not only configured as a single controller, but also configured as a controller group in which a plurality of controllers cooperate to execute control of the fuel cell system. I do not care. Moreover, the controller 8 may be comprised with the microcontroller, and may be comprised by MPU, PLC (programmable logic controller), a logic circuit, etc.

  By the way, the oxidant gas used for power generation of the fuel cell 1 usually uses the atmosphere in the environment in which it is installed, but the atmosphere often contains various impurities, such as volcanoes and combustion. There are sulfur compounds such as sulfur dioxide contained in exhaust gas, nitrogen oxides abundantly contained in combustion exhaust gas of factories and automobiles, and ammonia which is a malodorous component.

  These impurities may adversely affect the fuel cell 1 and may be mixed with the oxidant gas and adsorbed on the cathode catalyst to inhibit a chemical reaction necessary for power generation, thereby reducing the output of the fuel cell 1. In particular, the sulfur compound has a relatively strong adsorptive power, and if a large amount of the sulfur compound accumulates on the cathode, it becomes difficult to remove, which causes the power generation efficiency and durability of the fuel cell 1 to deteriorate.

  The present inventors paid attention to this sulfur compound having a relatively large influence on power generation performance, and as a result of intensive studies, the effect of catalyst activation can be achieved by using a gas with less impurities when performing catalyst activation operation. Found that would be higher.

That is, it was found that when the catalyst activation operation is performed on the fuel cell 1 whose voltage has been lowered by the durability test, the rate of increase in voltage is increased when a gas not containing impurities is used.
This phenomenon is effective not only for cathode impurities but also for anode impurities such as ammonia.

  Hereinafter, an example of an operation sequence of the fuel cell system capable of suppressing a decrease in catalyst activity due to impurities will be described using sulfur dioxide contained in the atmosphere among sulfur compounds as an example, with reference to the flowchart of FIG.

  When the fuel cell 1 is in a steady power generation state, the gas path generates power using the bypass path 51 that does not pass through the oxidant gas impurity removal means 41. Depending on the concentration of impurities in the gas, the catalyst is gradually poisoned and the voltage drops. When the voltage falls below a certain value, the controller 8 controls the oxidant gas path switching means 611, 612 to switch the oxidant gas gas supply path from the bypass path 51 to the path through the oxidant gas impurity removal means 41. Then, various active recovery operations are performed.

  Here, the threshold is set at the specified voltage, but it may be specified by the operation time or the like. This activation recovery operation may be performed independently, or the activation recovery operation may be performed in combination with the start operation and the stop operation.

  When the activity recovery operation is completed and the steady operation is started, the oxidant gas path switching means 611 and 612 are controlled again by the controller 8 to change the gas supply path from the path passing through the oxidant gas impurity removing means 41 to the bypass path. Switch to 51. Eventually, the system is stopped by performing an activity recovery operation when the system is stopped. Here, the end of the activity recovery operation can be determined by a voltage, or can be performed after a predetermined time.

  In general, the activity recovery operation is roughly divided into three types. The first type is to weaken the adsorption power of impurities to the catalyst by oxidizing the impurities adhering to the catalyst by raising the potential of the electrode. For example, when a sulfur compound is contained as an impurity, the adsorption power to the catalyst is weakened by becoming sulfur dioxide.

  The second type is that the catalyst itself is reduced to recover its activity by lowering the potential of the electrode. In the third type, by increasing the amount of water in the catalyst, impurities adsorbed on the catalyst are dissolved in water and discharged.

  These three types of activity recovery operations are effective even with at least one type of operation, but the effect becomes greater when the three types of operations are performed. Further, although the three types of operations are effective even if they are performed continuously or after a period of time, the effect becomes greater if they are performed continuously.

  First, an activation recovery operation for raising or lowering the potentials of the first and second types of electrodes will be described.

  The first is an operation of increasing or decreasing the potential by connecting an external power source to the fuel cell 1 and applying a voltage. When performing this operation, it is preferable to flow hydrogen gas to the anode serving as the reference electrode and to flow a gas (for example, nitrogen) inert to the cell reaction to the cathode serving as the working electrode.

  The second is a method of changing the potential by increasing or decreasing the load connected to the fuel cell 1. For example, if the external load is reduced, the voltage is increased, the cathode potential is increased, and if a higher load is applied, the potential is decreased. Further, if the load is disconnected, the highest potential is obtained.

  Third, an inert gas is allowed to flow through the fuel cell 1, an oxidant gas is allowed to flow through the anode, and a fuel gas is allowed to flow through the cathode. These gases may flow through the gas path to the electrode, or for example, only the gas supplied to the cathode may be stopped and the fuel gas may be diffused from the anode side through the polymer electrolyte membrane. Hydrogen gas may be generated at the cathode by applying a load of

  Alternatively, the gas supplied to the anode may be stopped and the oxidant gas may be diffused from the cathode side through the polymer electrolyte membrane. By any of these methods, it becomes possible to raise or lower the potential of the electrode, and oxidation of impurities adsorbed on the catalyst or reduction of the catalyst occurs, and the activity is restored.

  Next, the activity recovery operation for increasing the amount of water in the third type of catalyst will be described. The first is to cool the fuel cell 1 and lower the temperature. In this case, the flow rate of the cooling water may be increased, the temperature of the cooling water may be decreased, or the temperature control may be turned off if the fuel cell 1 is controlling the temperature with a heater.

  The second is to increase the amount of water per unit flow rate in the gas supplied to the fuel cell 1. This can be achieved by increasing the dew point of the supply gas. The third is to increase the pressure of the gas supplied to the fuel cell 1. For this purpose, the gas supply amount may be increased, or the pressure may be increased by reducing the size of the gas discharge port of the fuel cell 1. As the pressure increases, the dew point in the fuel cell 1 decreases and condensed water increases. By any of these methods, the amount of condensed water can be increased, the amount of water in the catalyst can be increased, and impurities can be dissolved in water and washed away.

  Using the fuel cell system configured as described above, a power generation test was conducted in the case where impurities contained in the oxidant gas that could accumulate on the cathode catalyst of the fuel cell 1 and affect the output and durability were present. . Note that the present invention is not limited to the power generation test.

  The controller 8 is configured to control the oxidant gas path switching means 611 and 612 so that the oxidant gas passes through the bypass path 51.

  Sulfur dioxide was used as an impurity to be added to the oxidant gas, and the addition concentration thereof was about 5 ppb at the atmospheric level with respect to the oxidant gas.

The cathode has a utilization rate of 0% so that the hydrogen utilization rate becomes 70%, the air containing sulfur dioxide as an impurity is supplied, the current flowing through the fuel cell 1 is gradually increased, and the fuel cell Power generation was started so that the output of the system would be 750W. The current density flowing through the fuel cell 1 at this time was about 0.2 A / cm ² , the anode dew point was about 65 ° C., the cathode dew point was about 65 ° C., and the average temperature of the fuel cell 1 was about 65 ° C.

  Next, continuous power generation is started after startup, and when the voltage drops by 20 μV, the controller 8 controls the oxidant gas path switching means 611 and 612 so that the oxidant gas passes through the oxidant gas impurity removal means 41. Then, after switching to be supplied to the fuel cell 1, it was stopped.

  At this time, the single cell voltage of the fuel cell 1 once increased to about 1V and then gradually decreased to about 0V. At this time, the average temperature of the fuel cell 1 dropped from about 65 ° C. to 40 ° C. or less when stopped. Four hours later, the operation was started again, and the controller 8 controlled the oxidant gas path switching means 611 and 612 so that the oxidant gas was supplied to the fuel cell 1 via the bypass path 51. . This series of starting and stopping cycles was repeated five times.

In each case, when the change in voltage after 20 hours from the start of power generation was examined, the amount of voltage drop every 5 cycles was 0 μV / hr, and the output drop was recovered by removing impurities at the start and stop. I confirmed that.

  According to the operation method using the fuel cell system of the eighth embodiment, the potential of the cathode rises to a high voltage of about 1V when starting and stopping, so that the impurities adsorbed on the catalyst are oxidized and 0V after stopping. Since the voltage is reduced until the catalyst is reduced, the activity is restored, and further, the temperature of the fuel cell 1 is lowered from 65 ° C. to 40 ° C. at the time of stoppage. Can do.

  By supplying the oxidant gas via the oxidant gas impurity removal means 41 to the fuel cell 1 at the time of starting and stopping by the oxidant gas path switching means 611 and 612, the voltage decrease rate is reduced and the effect of the activity recovery operation is improved. Further, since the amount of gas that permeates the oxidant gas impurity removing unit 41 can be reduced, the life of the oxidant gas impurity removing unit 41 can be extended. Therefore, it is possible to obtain an economical fuel cell system that can measure the long life of the oxidant gas impurity removing means 41 while the fuel cell system does not have a decrease in output or durability of the fuel cell 1. became.

(Embodiment 9)
FIG. 7 is a schematic configuration diagram showing a fuel cell system according to Embodiment 9 of the present invention. The fuel cell system according to the ninth embodiment of the present invention is the same as the fuel cell system according to the eighth embodiment, except that the oxidant gas impurity removing means 41 is provided in the oxidant gas path from the oxidant gas supply means 2 to the fuel cell 1. The bypass path 51 for bypassing the oxidant gas impurity removing means 41 and the oxidant gas path switching means 611 and 612 are not provided, and the fuel gas path from the fuel gas supply means 3 to the fuel cell 1 is not in the fuel gas. The fuel gas impurity removing means 42 for removing impurities contained therein, and the fuel gas from the fuel gas supply means 3 is supplied to the anode without bypassing the fuel gas impurity removing means 42 and removing the impurities by the fuel gas impurity removing means 42 Fuel gas path switching means 62 for switching between the bypass path 52 to be switched, the path through the fuel gas impurity removing means 42 and the bypass path 52. Comprises 622, start-stop, and when the active recovery operation is operated as a fuel gas through a path through the fuel gas impurity removing means 42 is supplied to the fuel cell 1. Other configurations are the same as those of the eighth embodiment, and detailed description thereof is omitted.

  Here, in the fuel gas, ammonia is contained as an impurity by reforming the raw material gas containing nitrogen. The ammonia concentration correlates with the nitrogen concentration contained in the source gas. When ammonia is supplied to the fuel cell 1, it binds to the sulfonic acid group in the electrolyte to reduce hydrogen ion conductivity, or ammonium ions that have moved through the anode catalyst and the electrolyte membrane poison the cathode catalyst. .

  The fuel gas impurity removing means 42 is configured to remove ammonia contained in the fuel gas. For example, an ammonia absorbing solution such as water is circulated on one side of the polymer electrolyte membrane and ammonia is contained on the other side. A structure in which a plurality of fuel gas flow structures are stacked can be used.

  When the ammonia is less than a predetermined accumulation amount, the inventors do not significantly reduce the output of the fuel cell 1 and do not affect the durability. Although it can be eliminated, if the fuel cell 1 generates power continuously for a long time and the accumulated amount of ammonia exceeds a predetermined value, it cannot be completely eliminated by a single start / stop, so output gradually. Has been found to decrease or durability to decrease.

With the configuration of the ninth embodiment, during the activation recovery operation at the time of starting and stopping, the fuel gas not containing impurities is supplied to the fuel cell 1 via the path passing through the fuel gas impurity removing means 42, so that the output is recovered. Since the rate becomes high, the influence on the fuel cell 1 is reduced, and the fuel cell 1 can continuously generate power stably for a long time. Further, since the amount of fuel gas permeating through the fuel gas impurity removing means 42 can be reduced, the life of the fuel gas impurity removing means 42 can be extended. Therefore, it is possible to obtain an economical fuel cell system in which the fuel gas impurity removing means 42 can be extended in life while the fuel cell system does not have a decrease in output or durability. Become.

(Embodiment 10)
FIG. 8 is a schematic configuration diagram showing a fuel cell system according to Embodiment 10 of the present invention. The fuel cell system of the tenth embodiment is the same as that of the eighth embodiment, except that the fuel gas impurity removing means removes impurities contained in the fuel gas in the fuel gas path from the fuel gas supply means 3 to the fuel cell 1. 42, a bypass path 52 for supplying the fuel gas from the fuel gas supply means 3 to the anode without bypassing the fuel gas impurity removal means 42 and removing the impurities by the fuel gas impurity removal means 42, and a fuel gas impurity removal means Fuel gas path switching means 621, 622 for switching between the path passing through 42 and the bypass path 52, and during the start-stop and active recovery operations, the oxidant gas path switching means 611, 612 and the fuel gas path switching means 621, 622 are provided. And the gas that has passed through the oxidant gas impurity removing means 41 and the fuel gas impurity removing means 42 is supplied to the fuel cell 1. It is operated to supply. Other configurations are the same as those of the eighth embodiment, and detailed description thereof is omitted.

  According to this configuration, since the output recovery effect by the activity recovery operation is improved both when the impurity is mixed in the oxidant gas and when the impurity is mixed in the fuel gas, the fuel cell 1 can be used for a long time. Since it is possible to generate power continuously and stably, it is excellent in performance and durability, and because it is the use of the oxidant gas impurity removal means 41 or the fuel gas impurity removal means 42 only during the activity recovery operation, The consumption of the oxidant gas impurity removing unit 41 and the fuel gas impurity removing unit 42 is suppressed, and the lifetimes of the oxidant gas impurity removing unit 41 and the fuel gas impurity removing unit 42 can be extended. The driving method can be obtained.

  As described above, the fuel cell system and the operation method thereof according to the present invention can improve resistance to impurities in the gas, and can be applied to uses such as stationary fuel cell systems.

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Oxidant gas supply means 3 Fuel gas supply means 7 Impurity supply amount determination means 8 Controller 41 Oxidant gas impurity removal means 42 Fuel gas impurity removal means 51, 52 Bypass path 611, 612 Oxidant gas path switching means 621,622 Fuel gas path switching means

Claims (21)

A fuel cell;
Gas supply means for supplying gas for power generation to the fuel cell;
Impurity removing means for removing impurities contained in the gas;
A bypass path for bypassing the impurity removing means;
Path switching means for switching between the path through the impurity removal means and the bypass path;
A controller, and
When the controller performs a predetermined operation or when a condition for determining that the supply amount of the impurity exceeds a predetermined amount is satisfied, the controller supplies the gas supply path to the fuel cell from the bypass path to the impurity. A fuel cell system that controls the path switching means to switch to a path that passes through a removing means. Impurity supply amount determination means for determining the supply amount of the impurities,
When the impurity supply amount determined by the impurity supply amount determination unit exceeds a predetermined impurity supply amount, the controller changes the gas supply path to the fuel cell from the bypass path to the impurity removal unit. Controlling the route switching means so as to switch to a route that passes through;
The fuel cell system according to claim 1. Comprising continuous power generation time measuring means for measuring continuous power generation time in continuous power generation from start to next stop,
When the continuous power generation time measured by the continuous power generation time measuring means exceeds a predetermined continuous power generation time, the controller changes the gas supply path to the fuel cell from the bypass path to the impurity removal means. Controlling the route switching means so as to switch to a route that passes through;
The fuel cell system according to claim 1. It has a cumulative power generation amount measuring means for measuring the cumulative power generation amount in continuous power generation from the start to the next stop,
The controller removes the impurities from the bypass path by supplying the gas supply path to the fuel cell when the cumulative power generation amount measured by the cumulative power generation amount measuring unit exceeds a predetermined power generation amount. Controlling the route switching means to switch to a route passing through the means;
The fuel cell system according to claim 1. Comprising an operation time measuring means for measuring the operation time of the gas supply means in continuous power generation from start to next stop,
The controller, when the operation time measured by the operation time measuring means exceeds a predetermined operation time, the gas supply path to the fuel cell is routed from the bypass path via the impurity removal means Controlling the route switching means to switch to
The fuel cell system according to claim 1. A cumulative gas supply amount measuring means for measuring a cumulative gas supply amount of the gas supply means in continuous power generation from start to next stop;
When the cumulative gas supply amount measured by the cumulative gas supply amount measuring unit exceeds a predetermined gas supply amount, the controller removes the impurities from the bypass route by supplying the gas supply route to the fuel cell. Controlling the route switching means to switch to a route passing through the means;
The fuel cell system according to claim 1. Power failure detection means to detect power failure,
When the power failure detection means detects a power failure, the controller switches the path switching means so that the gas supply path to the fuel cell is switched from the bypass path to a path via the impurity removal means. Control,
The fuel cell system according to claim 1. The controller switches the path so that the gas supply path to the fuel cell is switched from the bypass path to the path via the impurity removing means when performing the activity recovery operation of the catalyst of the fuel cell. Control means,
The fuel cell system according to claim 1.   9. The activity recovery operation according to claim 8, wherein the activity recovery operation is at least one of an operation of increasing the amount of water in the catalyst of the fuel cell and an operation of increasing and decreasing the potential of the electrode of the fuel cell. Fuel cell system. The operation of increasing the amount of water in the catalyst of the fuel cell includes the cooling operation of the fuel cell, the operation of increasing the amount of water per unit flow rate in the gas supplied to the fuel cell, and the operation of supplying the fuel cell At least one operation of increasing the pressure of the gas,
The fuel cell system according to claim 9. The operation of raising and lowering the electrode potential of the fuel cell includes the operation of applying a voltage from an external power source and sweeping the potential, the operation of controlling the size of the load connected to the fuel cell, the fuel cell and the load At least one of an operation of cutting and connecting to the fuel cell, an operation of flowing an inert gas to the fuel cell, an operation of flowing an oxidant gas to the anode of the fuel cell, and an operation of flowing the fuel gas to the cathode is there,
The fuel cell system according to claim 9. The gas supply means is an oxidant gas supply means for supplying an oxidant gas to the fuel cell,
The impurity removing means is an oxidant gas impurity removing means for removing impurities contained in the oxidant gas.
The fuel cell system according to any one of claims 1 to 11. The gas supply means is a fuel gas supply means for supplying fuel gas to the fuel cell;
The impurity removing means is a fuel gas impurity removing means for removing impurities contained in the fuel gas.
The fuel cell system according to any one of claims 1 to 11. The impurities include at least one of a sulfur compound and ammonia.
The fuel cell system according to any one of claims 1 to 13. The impurities adsorbed on the fuel cell are washed away by condensed water formed by condensation in the fuel cell when power generation is stopped.
The fuel cell system according to any one of claims 1 to 14. Gas supply means for supplying power generation gas to the fuel cell;
Impurity removing means for removing impurities contained in the gas;
A bypass path for bypassing the impurity removing means;
Path switching means for switching between the path through the impurity removal means and the bypass path;
A method for operating a fuel cell system comprising:
Usually, the gas for power generation is supplied to the fuel cell using the bypass path,
In continuous power generation from start to next stop,
If the continuous power generation time exceeds the predetermined continuous power generation time,
If the cumulative amount of generated power exceeds the specified amount of generated power,
When the operation time of the gas supply means exceeds a predetermined operation time,
When the cumulative gas supply amount of the gas supply means exceeds a predetermined gas supply amount,
When a power failure is detected,
In at least one of the cases, the path switching means is switched from the bypass path to the path via the impurity removal means,
Operation method of fuel cell system. A gas supply system for supplying gas for power generation to the fuel cell; a gas supply means; an impurity removal means for removing impurities contained in the gas; a bypass path for bypassing the impurity removal means; and the impurity removal means An operation method of a fuel cell system having a route switching means for switching between a route passing through and the bypass route,
Usually, the gas for power generation is supplied to the fuel cell using the bypass path,
When performing the activity recovery operation of the catalyst of the fuel cell, the path switching means is switched from the bypass path to a path via the impurity removal means,
Operation method of fuel cell system. The gas supply system having the gas supply means, the impurity removal means, the bypass path, and the path switching means includes an oxidant gas supply system that supplies an oxidant gas to the cathode of the fuel cell, and an anode of the fuel cell. At least one of a fuel gas supply system for supplying fuel gas to
The operation method of the fuel cell system according to claim 17.   The activity recovery operation is at least one of an operation of increasing the amount of water in the catalyst of the fuel cell and an operation of increasing and decreasing the potential of the electrode of the fuel cell. A method for operating the fuel cell system according to claim 1. The operation of increasing the amount of water in the catalyst of the fuel cell includes the cooling operation of the fuel cell, the operation of increasing the amount of water per unit flow rate in the gas supplied to the fuel cell, and the operation of supplying the fuel cell At least one operation of increasing the pressure of the gas,
The operation method of the fuel cell system according to claim 19. The operation of raising and lowering the electrode potential of the fuel cell includes the operation of applying a voltage from an external power source and sweeping the potential, the operation of controlling the size of the load connected to the fuel cell, the fuel cell and the load At least one of an operation of cutting and connecting to the fuel cell, an operation of flowing an inert gas to the fuel cell, an operation of flowing an oxidant gas to the anode of the fuel cell, and an operation of flowing the fuel gas to the cathode is there,
The operation method of the fuel cell system according to claim 19.