JP5086571B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system that can continue to operate safely even if an abnormality occurs in a commercial power source.

  A fuel cell that uses hydrogen and oxygen to generate electric power through these electrochemical reactions has attracted attention as an environmentally friendly power generator. Fuel cells require hydrogen for power generation, but are relatively difficult to obtain because the infrastructure for supplying hydrogen itself is not widespread. In many cases, a fuel cell system in which a reformer that generates a hydrogen-rich gas containing hydrogen used for power generation is provided in the fuel cell is constructed. The reformer is a reforming unit that introduces and reforms a raw material fuel that is a hydrogen-rich gas, and a reformer that is used for reforming in a reforming unit that introduces combustion fuel and air and burns the fuel. And a combustion section that generates heat. During operation of the fuel cell system, an anode off-gas containing hydrogen that has not been used for the electrochemical reaction among the hydrogen-rich gas introduced into the fuel cell is introduced into the combustion section as fuel and burned. Since a fuel cell system having a reformer requires a predetermined time to start up again once the operation is stopped, it is desirable not to stop the operation as much as possible.

  On the other hand, the fuel cell is generally linked to a commercial power source from the viewpoint of stabilizing power supply to the power load. When an abnormality such as a power failure occurs in the commercial power supply, it is required to disconnect the fuel cell from the commercial power supply for safety.

  When the fuel cell is disconnected from the commercial power source, the electric power generated by the fuel cell is supplied exclusively to auxiliary equipment for operating the fuel cell system. Then, since the power consumption of the auxiliary machines is generally less than the minimum power generation amount of the fuel cell, the power consumption of the power generated by the fuel cell is reduced and the utilization rate of hydrogen in the fuel cell is reduced. When the utilization rate of hydrogen decreases, the amount of combustible components in the anode off-gas introduced into the combustion section of the reformer increases and incomplete combustion may occur.

  In view of the above-described problems, the present invention is a fuel capable of avoiding incomplete combustion in the combustion section of the reformer while continuing operation even when an abnormality occurs in the commercial power supply and power consumption in the power load is reduced. An object is to provide a battery system.

In order to achieve the above object, a fuel cell system according to a first aspect of the present invention generates power by an electrochemical reaction between hydrogen and oxygen, for example, as shown in FIG. 1, and uses a commercial power supply via a relay 33R. 49, a reformer 20 that generates a reformed gas g containing hydrogen to be supplied to the fuel cell 30 by introducing and heating the raw material fuel m1 and reforming the fuel cell 30; The anode offgas p containing hydrogen that has not been used for the electrochemical reaction in the fuel cell 30 and the combustion air a are introduced to burn the anode offgas p, thereby generating reforming heat used for reforming the raw material fuel m1. A reformer 20 having a combustion section 23 to be caused; an inverter 35 that converts DC power generated by the fuel cell 30 into AC power; a commercial power supply abnormality detection means 38 that detects abnormality of the commercial power supply 49; When the power supply abnormality detection means 38 detects an abnormality of the commercial power supply 49, the generated power of the fuel cell 30 is reduced while maintaining the connection state of the relay 33R, the inverter 35 is gate-blocked, and the combustion unit 23 The anode off-gas p is controlled to be stably burned, and the inverter 35 is connected to the gate when the abnormality of the commercial power supply 49 is resolved within a first predetermined time after the abnormality of the commercial power supply 49 is detected. At the same time, it includes control devices 31 and 36 that increase the power generation output of the fuel cell 30 to the state before the decrease and shut off the relay 33R when the abnormality of the commercial power supply 49 is not resolved even after the first predetermined time has elapsed. Here, the control that “the combustion of the anode off gas p is stably performed” typically reduces the amount of the raw material fuel m1 introduced into the reformer 20, and the combustion air to the combustion section 23. It is control which performs at least one of increasing the introduction amount of a.

  With this configuration, when the commercial power supply abnormality detecting means detects a commercial power supply abnormality, the generated power of the fuel cell is reduced while maintaining the connection state of the relay, the inverter gate block is performed, and the combustion unit Since the anode off-gas combustion is controlled to be performed stably, the gate block disconnects the connection between the fuel cell and the commercial power source, and the power supplied from the fuel cell to the power load decreases. Even if the amount of hydrogen consumed decreases rapidly and the amount of combustible components in the anode off-gas introduced into the combustion section increases, an incomplete combustion state can be avoided, and harmful components such as carbon monoxide are removed from the system. It is possible to avoid being discharged.

Moreover, the fuel cell system according to the invention described in claim 2 adjusts the introduction amount of the raw material fuel m1 to the reformer 20 in the fuel cell system 10 according to claim 1, for example, as shown in FIG. Raw material fuel flow rate adjusting means 28, 65; and combustion air flow rate adjusting means 29 for adjusting the amount of combustion air a introduced into the combustion section 23; when the control devices 31, 36 perform gate block The raw material fuel flow rate adjusting means 28 and 65 are controlled to reduce the amount of the raw material fuel m1 introduced into the reformer 20, and the combustion air flow rate adjusting means 29 is controlled to control the combustion air a to the combustion section 23. It is configured to increase the introduction amount.

  With this configuration, the reformed gas generated in the reformer is reduced and introduced into the combustion section by controlling the feed fuel flow rate adjusting means and reducing the amount of feed of the feed fuel into the reforming section. The anode off gas containing the amount of combustible components can be reduced, and the air with respect to the amount of combustible components introduced into the combustion section can be reduced by controlling the combustion air flow rate adjusting means to increase the amount of combustion air introduced into the combustion section. The shortage can be resolved and the combustion of the anode off gas can be stabilized.

The fuel cell system according to the first aspect of the present invention, for example, shown with reference to FIG. 1, the control device 31 and 36, a commercial power source within a second predetermined time after the cut off relay 33R When the abnormality of 49 is resolved, the relay 33R is connected after the third predetermined time after the abnormality of the commercial power supply 49 is resolved, and the gate connection of the inverter 35 is performed to increase the power generation output of the fuel cell 30, and the second When the abnormality of the commercial power source 49 is not resolved even after a predetermined time has elapsed, the fuel cell system 10 is configured to shift to a stop process.

  With this configuration, when the abnormality of the commercial power source is resolved within the second predetermined time after the relay is disconnected, the relay is connected after the third predetermined time after the abnormality of the commercial power source is resolved. Since the power generation output is increased, safety can be ensured by refraining from connecting the relay until the commercial power supply side finishes the investigation of the abnormality. Further, since the fuel cell system is shifted to the stop process when the abnormality of the commercial power source is not resolved even after the second predetermined time has elapsed, the energy consumption necessary for the standby operation can be suppressed.

Further, the fuel cell system according to the invention described in claim 3 is, for example, as shown in FIG. 1, in the fuel cell system 10 according to claim 1 or 2 , the reformer generated by the reformer 20. Bypass means 53, 61, 62, 63 for bypassing the fuel cell 30 to the combustion unit 23 by bypassing the gas g; connected to the fuel cell 30 via the relay 33 A, the electric power generated by the fuel cell 30 and the commercial power supply 49 Including auxiliary machines 27, 28, and 29 used to operate the reformer 20 and the fuel cell 30, after the abnormality of the commercial power supply 49 is resolved. Until the third predetermined time elapses, the fuel cell 30 and the auxiliary machines 27, 28, 29 are generated in the reformer 20 by the bypass means 53, 61, 62, 63 while maintaining the non-connected state. Burning reformed gas g Bypassing the battery 30 is configured to stop the supply of oxygen to the fuel cell 30 together with the burning leads to the combustion section 23.

  With this configuration, the reformer generated by the reformer by the bypass means while maintaining the non-connected state between the fuel cell and the auxiliary machine until the third predetermined time elapses after the abnormality of the commercial power source is resolved. Since the gas bypasses the fuel cell and is guided to the combustion section and burned, the resumption of interconnection when the abnormality of the commercial power source is resolved can be performed quickly. In addition, since the supply of oxygen to the fuel cell is stopped until the third predetermined time elapses after the abnormality of the commercial power source is resolved, the fuel cell can be prevented from being exposed to a high potential state, and the fuel cell A decrease in durability of the battery can be reduced.

  According to the present invention, when the commercial power source abnormality detecting means detects a commercial power source abnormality, the generated power of the fuel cell is reduced while maintaining the connection state of the relay, the inverter gate block is performed, and the combustion unit Since the anode off-gas combustion is controlled to be performed stably, the gate block disconnects the connection between the fuel cell and the commercial power source, and the power supplied from the fuel cell to the power load decreases. Even if the amount of hydrogen consumed decreases rapidly and the amount of combustible components in the anode off-gas introduced into the combustion section increases, an incomplete combustion state can be avoided, and harmful components such as carbon monoxide are removed from the system. It is possible to avoid being discharged.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing, the same or corresponding members are denoted by the same or similar reference numerals, and redundant description is omitted. In FIG. 1, a broken line represents a control signal.

  First, the configuration of a fuel cell system 10 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic system diagram of the fuel cell system 10. The fuel cell system 10 controls a reformer 20 that generates a reformed gas g rich in hydrogen, a fuel cell 30 that generates power by an electrochemical reaction between hydrogen and oxygen, and devices that constitute the fuel cell system 10. And a power conditioner 34 that can convert DC power into AC power and has a grid connection protection function. The power conditioner 34 is an inverter 35 that converts DC power into AC power, a controller 36 that controls the electrical system of the fuel cell system 10, and a commercial power source that detects an abnormality in the commercial power source 49 that is linked to the fuel cell 30. And an abnormality detection means 38.

  The reformer 20 introduces a raw material fuel m1 and process water (not shown) and generates a reformed gas g rich in hydrogen by a steam reforming reaction, and a steam reforming reaction of the raw material fuel m1. And a combustion section 23 that generates the heat of reforming used. The raw material fuel m1 is typically composed mainly of chain hydrocarbons (including natural gas) such as methane and ethane, or hydrocarbons such as methanol and petroleum products (kerosene, gasoline, naphtha, LPG, etc.). A hydrocarbon-based fuel such as a mixture, which is suitable for combustion for heating, is used. The process water (not shown) introduced into the reforming unit 25 may be steam. The reformed gas g rich in hydrogen is a gas containing hydrogen as a main component, and is a gas supplied to the fuel cell 30 containing hydrogen in an amount of 40% by volume or more, typically about 70 to 80% by volume. is there. The hydrogen concentration in the reformed gas g may be 80% by volume or more, that is, any concentration that can generate power by an electrochemical reaction with oxygen in the oxidant gas t when supplied to the fuel cell 30.

  The reforming unit 25 is filled with a reforming catalyst and configured to promote a steam reforming reaction. As the reforming catalyst, a nickel-based reforming catalyst or a ruthenium-based reforming catalyst is typically used. If the gas rich in hydrogen generated by reforming the raw material fuel m1 by the action of the reforming catalyst contains a predetermined amount or more of carbon monoxide, the electrode catalyst of the fuel cell 30 is poisoned. Therefore, the reforming section 25 has a shift section (not shown) filled with a shift catalyst and a selective oxidation section (not shown) filled with a selective oxidation catalyst, and is reformed derived from the reformer 20. It is preferable that the concentration of carbon monoxide in the gas g is about 10 ppm by volume or less, preferably about 1 ppm by volume. As the shift catalyst, typically, an iron-chromium shift catalyst, a copper-zinc shift catalyst, a platinum shift catalyst, or the like is used. Typically, a platinum-based selective oxidation catalyst, a ruthenium-based selective oxidation catalyst, a platinum-ruthenium-based selective oxidation catalyst, or the like is used as the selective oxidation catalyst. The reaction in the reforming catalyst is an endothermic reaction, but the reaction in the shift part having the shift catalyst and the selective oxidation part having the selective oxidation catalyst is an exothermic reaction. A raw material fuel pipe 55 for introducing the raw material fuel m1 and a process water pipe (not shown) for introducing process water (not shown) are connected to the reforming unit 25. When the process water pipe (not shown) is connected to the raw material fuel pipe 55 closest to the reforming section 25, the process water pipe is introduced into the reforming section 25 in a state where the raw material fuel m1 and the process water (not shown) are mixed. Is preferred. However, a process water pipe (not shown) may be directly connected to the reforming unit 25. A raw material fuel valve 65 is provided in the raw material fuel pipe 55. In addition, a reformed gas pipe 51 for deriving the reformed gas g is connected to the reforming unit 25 (in the case where the reformed gas has a site for reducing the carbon monoxide concentration). Further, the reforming unit 25 is provided with a temperature detector (not shown) for detecting the temperature.

  The combustion unit 23 is disposed in the reformer 20 so as to be adjacent to a position where the reforming catalyst of the reforming unit 25 is provided. The combustion unit 23 introduces combustion fuel m2, which is a hydrocarbon-based fuel, and anode offgas p and reformed gas g, which are hydrogen-containing gases, and also introduces combustion air a, and these are used with a burner (not shown). The reforming heat used for the steam reforming reaction can be obtained by burning the steam. The combustion unit 23 introduces and burns one or more of the combustion fuel m2, the anode offgas p, and the reformed gas g according to the state of the fuel cell system 10. In the present embodiment, the same fuel as the raw material fuel m1 is used as the combustion fuel m2. That is, the raw material fuel m1 and the combustion fuel m2 are obtained by changing the names of the fuel m flowing through the fuel pipe 57 according to the application, and the components are the same. The components of the anode off gas p typically include about half of hydrogen and the other half of carbon dioxide, nitrogen, and methane. A fuel blower 28 that sends gaseous fuel m is disposed in the fuel pipe 57. When the fuel m is liquid, a fuel pump is provided in place of the fuel blower 28. In the present embodiment, the fuel blower 28 will be described. The fuel blower 28 is one of the auxiliary machines 27 of the fuel cell system 10. The combustion unit 23 is provided with a burner (not shown) as a device for generating reforming heat. The combustion section 23 includes an anode offgas pipe 52 capable of introducing the anode offgas p and the reformed gas g, a combustion fuel pipe 56 for introducing the combustion fuel m2, and a combustion air pipe 58 for introducing the combustion air a. It is connected. The combustion fuel pipe 56 is provided with a combustion fuel valve 66. Further, an exhaust gas pipe 59 for discharging the exhaust gas e after being burned by a burner (not shown) is connected to the combustion unit 23.

  The fuel cell 30 is typically a polymer electrolyte fuel cell. The fuel cell 30 includes an anode 30A for introducing the reformed gas g, a cathode 30C for introducing the oxidant gas t, and a cooling unit (not shown) that removes heat generated by an electrochemical reaction. Yes. The oxidant gas t introduced to the cathode 30C is typically air. Although the fuel cell 30 is shown in a simplified manner in the figure, in practice, a single cell is formed by sandwiching a solid polymer membrane between the anode 30A and the cathode 30C, and a plurality of this cell is formed via a cooling unit. It is configured by stacking sheets. In the fuel cell 30, hydrogen in the reformed gas g supplied to the anode 30A is decomposed into hydrogen ions and electrons, and the hydrogen ions pass through the solid polymer film and move to the cathode 30C. It moves to the cathode 30C through a conducting wire connecting to the cathode 30C, reacts with oxygen in the oxidant gas t supplied to the cathode 30C to generate water, and generates heat during this reaction. In this reaction, the direct current can be taken out by passing electrons through the conducting wire. The fuel cell 30 is electrically connected to the power conditioner 34 via the output cable 41.

  The anode 30 </ b> A and the reforming unit 25 are connected via a reformed gas pipe 51. The reformed gas pipe 51 is provided with a reformed gas valve 61. The anode 30 </ b> A and the combustion unit 23 are connected via an anode off-gas pipe 52, and an anode off-gas p containing hydrogen that has not been used for an electrochemical reaction in the fuel cell 30 can be introduced into the combustion unit 23. It can be done. An anode off gas valve 62 is disposed in the anode off gas pipe 52. A reformed gas pipe 51 upstream of the reformed gas valve 61 and an anode offgas pipe 52 downstream of the anode offgas valve 62 are connected by a bypass pipe 53. A bypass valve 63 is provided in the bypass pipe 53. The cathode 30C includes an oxidant gas pipe 54 that introduces an oxidant gas t, and a cathode offgas pipe (not shown) that discharges a cathode offgas (not shown) containing oxygen that has not been used for the electrochemical reaction in the fuel cell 30. Are connected to each other. The oxidant gas pipe 54 is one of the pipes branched from the air pipe 54A, and the other one branched from the air pipe 54A is the combustion air pipe 58. An air blower 29 for sending the oxidant gas t to the cathode 30C and sending the combustion air a to the combustion unit 23 is disposed in the air pipe 54A. The air blower 29 is one of the auxiliary machines 27 of the fuel cell system 10. The oxidant gas pipe 54 is provided with an oxidant gas cutoff valve 64. The oxidant gas pipe 54 is typically provided with a humidifier (not shown) that humidifies the oxidant gas t.

  The auxiliary machinery 27 is a device that mainly operates during operation of the fuel cell system 10, and in addition to the fuel blower 28 and the air blower 29 described above, a cooling water pump that sends cooling water to a cooling unit (not shown) of the fuel cell 30. And fans for ventilation. In the present embodiment, the auxiliary machinery 27 has a motor driven by receiving DC power. The auxiliary machines 27 including the fuel blower 28 and the air blower 29 are connected to the control unit 31 via signal cables, respectively, and are configured to be started and stopped by signals from the control unit 31. Each of the fuel blower 28 and the air blower 29 has an inverter, and is configured so that the discharge amount of the fluid can be adjusted by adjusting the rotation speed according to a signal from the control unit 31. . In addition, each of the valves 61 to 66 is connected to the control unit 31 via a signal cable, and is configured to open and close by a signal from the control unit 31. In the present embodiment, the fuel blower 28 and the raw material fuel valve 65 constitute a raw material fuel flow rate adjusting means, and the air blower 29 constitutes a combustion air flow rate adjusting means.

  The control unit 31 is a device that controls the operation of the fuel cell system 10. As described above, the control unit 31 transmits a signal to the accessories 27 including the fuel blower 28 and the air blower 29 to control the start / stop of the accessories 27 and discharges from the fuel blower 28 and the air blower 29. To control the flow rate of the fluid. Note that transmitting a signal to the auxiliary machinery 27 includes transmitting a signal to a power panel (not shown) that transmits power to the auxiliary machinery 27. The control unit 31 is connected to each of the valves 61 to 66 through a signal cable, and is configured to transmit an open / close signal to open / close the valve. Further, the control unit 31 transmits signals to relays 84 and 86 to be described later to control on / off of a circuit in which these are arranged. The control unit 31 is connected to a temperature detector (not shown) that detects the temperature of the reforming unit 25 by a signal cable, and is configured to receive a temperature signal.

  The power conditioner 34 has a function of interconnecting the fuel cell 30 and the commercial power source 49. The commercial power source 49 is an AC power source supplied from an electric power company. The power conditioner 34 is electrically connected to the fuel cell 30 via the output cable 41 and electrically connected to the commercial power supply 49 via the system cable 45. The power conditioner 34 has a timer 37 as a time measuring means. Moreover, the power conditioner 34 is provided with the inverter 35, the control part 36, and the commercial power supply abnormality detection means 38 as mentioned above.

  The inverter 35 has a plurality of switching elements such as IGBTs, and is a device that converts DC power into AC power by the switching operation of the switching elements. Further, the inverter 35 can perform a gate block that turns off all the switching elements, and is configured to be able to electrically cut off the interconnection between the fuel cell 30 and the commercial power supply 49 by the gate block. .

  The control unit 36 controls the availability of the gate block of the inverter 35. Further, the control unit 36 transmits signals to relays 33A and 33B and a relay 33R, which will be described later, and controls on / off of a circuit in which these are arranged. The control unit 36 is connected to a timer 37 and is configured to be able to control the relays 33A, 33B, the relay 33R, the inverter 35, and the like based on the time measured by the timer 37. The control unit 36 is connected to the control unit 31 via a signal cable, and is configured to be able to communicate the control status with each other. Although the control unit 31 and the control unit 36 are separately illustrated in FIG. 1, they may be integrally configured as a control device. Further, the control unit 36 is connected to the commercial power supply abnormality detection means 38 and is configured to perform appropriate control with respect to the abnormality that has occurred in the commercial power supply 49.

  The commercial power supply abnormality detecting means 38 is means for detecting a voltage drop or a power failure of the commercial power supply 49, and typically the following are provided as necessary. That is, the commercial power supply abnormality detection means 38 is an overvoltage detector, an undervoltage detector, a frequency increase detector, a frequency decrease detector, or a single operation detector having a function equivalent to these 1 or 2 as necessary. The above is implemented. The commercial power supply abnormality detection means 38 is connected to the control unit 36 and is configured to be able to transmit the presence or absence of abnormality of the commercial power supply 49 to the control unit 36 as a signal.

  An auxiliary machine cable 43 for transmitting DC power to the auxiliary machines 27 is connected to the output cable 41. The auxiliary machine cable 43 is provided with a relay 33A so that the auxiliary machine cable 43 can be turned on and off. The relay 33A is typically an a-contact (normally open) relay, and is configured to be turned on / off by a signal from the control unit 36. A control cable 42 for transmitting DC power generated by the fuel cell 30 to the control unit 31 is connected to the auxiliary cable 43 between the relay 33 </ b> A and the auxiliary machines 27.

  The system cable 45 is provided with a relay 33R for physically disconnecting the fuel cell 30 from the commercial power supply 49, and is configured so that the circuit of the system cable 45 can be turned on / off. . An auxiliary machine cable 46 for transmitting AC power to the auxiliary machines 27 and the control unit 31 is connected to the system cable 45 between the relay 33 </ b> R and the commercial power supply 49. The control unit 31 is connected to a control cable 47 branched from the auxiliary machine cable 46. In the present embodiment, since the auxiliary machinery 27 and the control unit 31 are DC driven, the converter 39 that converts AC power supplied from the commercial power supply 49 into DC power is connected to the branch point of the control cable 47 and the system cable 45. Between the auxiliary cables 46. Further, the auxiliary machine cable 46 is provided with a relay 33B so that the circuit of the auxiliary machine cable 46 can be turned on and off. The relay 33B is typically a b-contact (normally closed) relay, and is configured to be turned on / off by a signal from the control unit 36. A load cable 48 for transmitting AC power to a power load such as an electric device that consumes power is connected to the system cable 45 between the branch point of the auxiliary cable 46 and the commercial power supply 49.

  The fuel cell system 10 includes a storage battery 81 as an emergency power source. The storage battery 81 is a control unit that includes a second predetermined time to be described later and a time required for the process of stopping the fuel cell system 10 when there is no power generation from the fuel cell 30 and the commercial power supply 49 has also failed. 31 and auxiliary machinery 27 can be operated. The storage battery 81 is connected to the control unit 31 via the control cable 82. Further, the storage battery 81 is connected via an auxiliary machine cable 43 and a storage battery cable 83 between the branch point of the control cable 42 and the relay 33 </ b> A. The storage battery cable 83 is provided with an a-contact relay 84 so that the circuit of the storage battery cable 83 can be turned on and off. Further, the storage battery 81 is connected via an auxiliary machine cable 46 and a storage battery cable 85 between the branch point of the control cable 47 and the converter 39. The storage battery cable 85 is provided with an a-contact relay 86 so that the circuit of the storage battery cable 85 can be turned on and off. Due to the cable connection relationship as described above, the storage battery 81 can store the power supplied from the commercial power supply 49 and the power generated by the fuel cell 30, and discharge toward the control unit 31 and the accessories 27. can do.

  With continued reference to FIG. 1, the operation of the fuel cell system 10 will be described. In order to start the operation of the stopped fuel cell system 10, the fuel blower 28 is started to supply the combustion fuel 23 to the combustion unit 23 and the air blower 29 is started to supply the combustion air a to the combustion unit 23. Supply. At the initial start of the fuel cell system 10, the circuit of the auxiliary machine cable 43 is turned off by the relay 33A (the state where there is no energization), and the circuit of the auxiliary machine cable 46 is turned on by the relay 33B (the state where there is current supply). The direct current power converted by the converter 39 is supplied to the fuel blower 28 and the air blower 29. That is, AC power supplied from the commercial power source 49 is input to the converter 39. Further, when the storage battery 81 has a free capacity, the circuit of the storage battery cable 85 is turned on by the relay 86, and the DC power converted by the converter 39 is supplied to the storage battery 81. When the storage battery 81 runs out of free capacity, the control unit 31 operates the relay 86 to turn off the circuit of the storage battery cable 85. The combustion fuel valve 66 is open, and the other valves 61 to 65 are closed. When the combustion fuel m2 is combusted in the combustion unit 23 to generate reforming heat and the temperature of the reforming unit 25 is increased, the raw material fuel valve 65 is opened to introduce the raw material fuel m1 into the reforming unit 25. The temperature of the reforming unit 25 is detected by a temperature detector (not shown). Process water (not shown) is also introduced into the reforming unit 25, the reforming heat is obtained from the combustion unit 23, the raw material fuel m1 undergoes a steam reforming reaction, and reformed gas g is generated. In the reformer 20, the reformed gas g is generated as described above, but since the composition of the reformed gas g is not stable at the beginning of operation, the reformed gas valve 61 and the anode off-gas valve 62 are closed. Then, the bypass valve 63 is opened, and the reformed gas g whose composition is not stable is led to the combustion section 23 without being supplied to the fuel cell 30 and burned. At this time, the reformed gas g having an unstable composition introduced into the combustion unit 23 is mainly combusted, and the insufficient amount of combustion fuel m2 is introduced into the combustion unit 23 by adjusting the opening of the combustion fuel valve 66. When the reformed gas g whose composition is not stable is sufficient, the combustion fuel valve 66 is closed.

  When the composition of the reformed gas g generated in the reformer 20 becomes stable, the control unit 31 opens the reformed gas valve 61 and the anode off-gas valve 62, closes the bypass valve 63, and reformed gas. g is introduced into the fuel cell 30. Thereby, the reformed gas g is introduced into the anode 30A of the fuel cell 30. On the other hand, the control unit 31 opens the oxidant gas shut-off valve 64, whereby the oxidant gas t is introduced into the cathode 30 </ b> C of the fuel cell 30.

In the fuel cell 30, an electrochemical reaction is performed by hydrogen in the reformed gas g introduced into the anode 30A and oxygen in the oxidant gas t introduced into the cathode 30C. Regarding the electrochemical reaction, the reaction represented by the following formula (1) is performed on the anode 30A side, and the reaction represented by the following formula (2) is performed on the cathode 30C side.
2H ₂ → 4H ⁺ + 4e ⁻ (1)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)
Electricity is generated by this electrochemical reaction, heat is generated, and moisture is generated. In further explanation, electric power can be obtained when electrons on the anode 30A side move to the cathode 30C side through the external electric circuit. Hydrogen ions on the anode 30A side pass through the solid polymer membrane and move to the cathode 30C side, and combine with oxygen to generate moisture. This electrochemical reaction is an exothermic reaction.

  When the reformed gas g and the oxidant gas t are supplied to the fuel cell 30 and an output is obtained by the fuel cell 30, the control unit 31 transmits a signal to the relays 33A and 33B to turn on the relay 33A, and the relay Turn 33B off. As a result, the auxiliary machinery 27 continues to operate by directly receiving the DC power generated by the fuel cell 30 instead of the power converted into DC by the converter 39. Thus, when the auxiliary machinery 27 receives DC power from the fuel cell 30, there is no conversion loss from AC to DC, and the efficiency of the fuel cell system 10 is improved. If the storage battery 81 still has free capacity, the control unit 31 activates the relays 84 and 86 to turn on the circuit of the storage battery cable 83, turns off the circuit of the storage battery cable 85, and the fuel cell 30 is connected to the storage battery 81. The generated DC power is supplied. On the other hand, since the power obtained by the fuel cell 30 is DC power, it is converted into AC power by the inverter 35 of the power conditioner 34 and transmitted to a power load (not shown). The electric power generated by the fuel cell 30 is adjusted by the control unit 31 by adjusting the reformed gas g and the oxidant gas t supplied to the fuel cell 30, so that the power consumed by the auxiliary devices 27 and the power load is summed up. On the other hand, it is controlled to a predetermined value (for example, 90% of power consumption). The insufficient power is supplied with AC power from the commercial power source 49. The heat generated in the fuel cell 30 is stored, for example, in a hot water storage tank (not shown), and is consumed in a thermal load such as hot water supply or heating as necessary. By effectively using the heat generated in the fuel cell 30, the efficiency of the fuel cell system 10 is improved.

  During the operation of the fuel cell 30, the anode off gas p is discharged from the anode 30A. The discharged anode off gas p is guided to the combustion unit 23 of the reformer 20 via the anode off gas pipe 52 and burned. By the combustion of the anode off gas p in the combustion unit 23, reforming heat used for reforming in the reforming unit 25 can be generated. When the reforming heat generated by the combustion of the anode offgas p introduced into the combustion unit 23 is insufficient, the combustion fuel m2 is introduced into the combustion unit 23 by adjusting the opening of the combustion fuel valve 66. The exhaust gas e generated by the combustion in the combustion unit 23 is discharged out of the system through the exhaust gas pipe 59. On the other hand, a cathode off gas (not shown) is discharged from the cathode 30C, and is discharged out of the system via a cathode off gas pipe (not shown).

  As described above, until the output of the fuel cell 30 can be obtained from the state where the fuel cell system 10 is stopped, the temperature of the reformer 20 is increased, and then the composition of the reformed gas g is stabilized. Therefore, it is preferable that the fuel cell system 10 is not stopped as long as there is demand.

  Incidentally, when an abnormality such as a power failure or a voltage drop occurs in the commercial power source 49, it is generally required to disconnect the commercial power source 49 and the fuel cell 30 from each other. Generally, in the distribution system on the commercial power supply 49 side, the distribution line is divided into appropriate sections, and when an abnormality occurs, the downstream side is separated from the section where the abnormality has occurred and the abnormality is investigated. This is because the power generated by the fuel cell 30 during the investigation is not applied to the distribution system on the commercial power supply 49 side, thereby ensuring the safety on the system side. When an abnormality occurs in the commercial power supply 49, the fuel cell system 10 performs the following control.

  With reference to FIG. 2, control of the fuel cell system 10 when an abnormality occurs in the commercial power supply 49 will be described. FIG. 2 is a flowchart showing control of the fuel cell system when a commercial power supply abnormality occurs. In the following description, FIG. 1 will be referred to as appropriate for the reference numerals of the components of the fuel cell system 10. In the fuel cell system 10, the control unit 36 determines whether the commercial power supply abnormality detecting unit 38 has detected an abnormality in the commercial power supply 49 (S <b> 11). This determination is repeated when no abnormality is detected. When an abnormality is detected, a gate block is performed to turn off the switching element of the inverter 35 (S12). By performing the gate block, when the abnormality of the commercial power supply 49 is quickly resolved such as an instantaneous power failure, it is possible to quickly return to the steady operation.

  When the gate block is performed, the power generated by the fuel cell 30 is not consumed except by the auxiliary machinery 27. Then, in general, the power consumption of the auxiliary machines 27 is less than the minimum power generation amount of the fuel cell 30, so that the power generation amount becomes excessive, and the fuel cell 30 is exposed to a high potential and the durability is lowered. In order to avoid this inconvenience, the control unit 31 reduces the generated power of the fuel cell 30. Moreover, when the consumption of the electric power generated by the fuel cell 30 decreases, the utilization rate of hydrogen in the reformed gas g decreases, and the amount of combustible components in the anode offgas p increases. When the anode off-gas p with an increased amount of combustible component is introduced into the combustor 23 and burned, hydrogen with high combustibility is completely combusted, but methane with low combustibility becomes incomplete combustion, and harmful components such as carbon monoxide There is a risk that the exhaust gas e containing will be discharged out of the system. In order to avoid this inconvenience, after the gate block is performed, the control unit 31 increases the amount of combustion air a introduced into the combustion unit 23 by increasing the rotational speed of the air blower 29, and the fuel blower 28 By reducing the rotation speed, the amount of the raw material fuel m1 introduced into the reforming unit 25 is decreased (S13). Thereby, combustion of anode off gas p in combustion part 23 is performed stably.

  The response by the gate block is controlled so that the combustion of the anode off gas p in the combustion section 23 is stably performed within the first predetermined time after the abnormality of the commercial power supply 49 is detected (the combustion air a). This is based on experimental findings that incomplete combustion in the combustion section 23 is suppressed and the exhaust gas e containing harmful components such as carbon monoxide is not discharged out of the system. Note that the control for stably burning the anode off gas p may be performed only when one of the increase in the combustion air a and the decrease in the raw material fuel m1 is sufficient. The first predetermined time is a time during which emission of harmful components such as carbon monoxide can be prevented by controlling to stably burn the anode off gas p when the gate block is performed. 0.8 seconds.

  The control unit 36 determines whether or not the abnormality has been resolved within the first predetermined time after detecting the abnormality of the commercial power supply 49 (S14). If the abnormality has been resolved, it waits for a predetermined time (5 seconds in the present embodiment) required for safety confirmation after the abnormality is resolved (S15), and then the gate connection of the inverter 35 (release of the gate block) is performed ( S16). When the gate connection is made, the fuel cell 30 is linked to the commercial power supply 49, and the power generated by the fuel cell 30 is also supplied to the power load, thereby increasing the power consumption. For this reason, the control unit 31 increases the amount of the raw material fuel m1 introduced into the reforming unit 25 by increasing the rotational speed of the fuel blower 28 (S17), and burns by decreasing the rotational speed of the air blower 29. The amount of combustion air a introduced into the unit 23 is reduced (S18), and the generated power of the fuel cell 30 is returned to the state before the abnormality of the commercial power source 49 is detected (before the output is reduced) to continue the steady operation. .

  In the step of determining whether or not the abnormality has been resolved within the first predetermined time after detecting the abnormality of the commercial power supply 49 (S14), if the abnormality has not been resolved, the relay 33R is shut off (S21). By cutting off the relay 33R, it is possible to reliably prevent application of power to the distribution system on the commercial power supply 49 side. Then, the flow rate of the raw material fuel m1 introduced into the reforming unit 25 is set to the flow rate during the hot hold operation of the reformer 20 (S22). The hot hold operation of the reformer 20 is an operation of maintaining the temperature of the catalyst of the reforming unit 25 in a state close to the temperature at the time of steady operation, and the reformed gas g generated by the reformer 20 is removed from the combustion unit. This is an operation for directing to 23 (bypassing the anode 30A) and burning. The reformer 20 is set to the hot hold operation in order to suppress the deterioration of the durability of the fuel cell 30 and to immediately reform when the request is made while the supply of the reformed gas g to the fuel cell 30 is stopped. This is because the gas g can be supplied. As described above, since it takes a considerable time until the reformed gas g having a stable composition is generated from a state where the reformer 20 is cooled (at the ambient temperature), a hot hold operation is necessary. It becomes.

  When the flow rate of the raw material fuel m1 is set to the flow rate during the hot hold operation, the reformed gas valve 61 and the anode offgas valve 62 are closed, the bypass valve 63 is opened (S23), and the reformer generated by the reformer 20 The gas g is guided to the combustion unit 23. Then, the oxidant gas shut-off valve 64 is closed (S24), the supply of the oxidant gas t to the cathode 30C of the fuel cell 30 is stopped, and the flow rate of the combustion air a introduced into the combustion unit 23 is changed to the reformer. The flow rate during hot hold operation is set to 20 (S25). By the supply of the reformed gas g and the oxidizing gas t to the fuel cell 30 is stopped to lower the voltage of the fuel cell 30, the durability of the fuel cell 30 can be suppressed to a minimum to decrease. Although the power generation from the fuel cell 30 when stopping the supply of the reformed gas g and the oxidizing gas t to the fuel cell 30 in the hot-hold operation is eliminated, the operation of such auxiliaries 27 and the control unit 31 at this time Is performed by electric power supplied from the storage battery 81.

  Thereafter, the control unit 36 determines whether or not the abnormality has been resolved within a second predetermined time after the relay 33R is cut off (S26). If the abnormality has been resolved, it waits for the third predetermined time to elapse after the abnormality is resolved (S27). The second predetermined time is a time during which the operation of the reformer 20 is considered to be less fuel m consumption than when the reformer 20 is stopped and then started up. The third predetermined time is a time during which the connection of the distributed power source such as the fuel cell 30 to the commercial power source 49 is prohibited for safety, and differs depending on the electric power company (electric power company). Note that after the abnormality is resolved, the electric power from the commercial power supply 49 is supplied to the auxiliary machinery 27, the control unit 31, and the like. At this time, the control unit 36 turns on the relay 33B and turns off the relay 33A. The control unit 31 turns on the relay 86 to charge the storage battery 81.

  When the third predetermined time has elapsed, the relay 33R is connected and the inverter 35 is connected to the gate (S28). Then, the control unit 31 increases the introduction amount of the raw material fuel m1 to the reforming unit 25 by increasing the rotational speed of the fuel blower 28 (S29), and opens the reformed gas valve 61 and the anode off-gas valve 62. The bypass valve 63 is closed (S30), and the reformed gas g is supplied to the anode 30A of the fuel cell 30. Thereafter, the oxidant gas shut-off valve 64 is opened (S31), the supply of the oxidant gas t to the cathode 30C of the fuel cell 30 is restarted, and the rotational speed of the air blower 29 is increased to burn the combustion part 23. The introduction amount of the working air a is increased to obtain a flow rate during steady operation (S32). As a result, the fuel cell system 10 returns to the steady operation state, and the electric power generated by the fuel cell 30 is supplied to the electric power load. When the fuel cell system 10 returns to the steady operation state, the control unit 36 turns on the relay 33A and turns off the relay 33B, and the DC power generated by the fuel cell 30 is supplied to the auxiliary devices 27. Like that.

  If the abnormality is not resolved in the step (S26) of determining whether or not the abnormality is resolved within the second predetermined time after the abnormality of the commercial power supply 49 is detected, the abnormality of the commercial power supply 49 is resolved early. Therefore, the process proceeds to a step of stopping the fuel cell system 10 (S41), and the consumption of the fuel m in a state where the power generation by the fuel cell 30 is not performed is prevented. The stop of the fuel cell system 10 is performed by sealing the inert gas such as nitrogen gas or the reformed gas g into the reforming section 25 and taking measures to suppress the deterioration of the catalyst of the reforming section 25, and then the auxiliary equipment 27 This is done by stopping. When the stop process is performed, electric power is supplied from the storage battery 81 to the auxiliary machinery 27, the control unit 31, and the like.

  In the above description, the fuel cell 30 has been described as a polymer electrolyte fuel cell, but may be a fuel cell other than a polymer electrolyte fuel cell such as a phosphoric acid fuel cell. However, the polymer electrolyte fuel cell can be operated at a relatively low temperature and can be downsized, so that it is suitable for installation in a general household.

1 is a schematic system diagram showing a fuel cell system according to an embodiment of the present invention. It is a flowchart which shows the control at the time of commercial power supply abnormality generation | occurrence | production.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell system 20 Reformer 23 Combustion part 27 Auxiliary machine 28 Fuel blower (auxiliary machine)
29 Air blower (auxiliary machine)
30 Fuel cell 31, 36 Control unit 33A Relay 33R Relay 35 Inverter 38 Commercial power supply abnormality detecting means 49 Commercial power supply 53 Bypass pipe 61 Reformed gas valve 62 Anode off gas valve 65 Raw material fuel valve a Combustion air g Reformed gas m1 Raw material fuel p Anode off gas

Claims (3)

A fuel cell that generates electricity through an electrochemical reaction between hydrogen and oxygen and is connected to a commercial power source via a relay;
A reformer that generates a reformed gas containing hydrogen to be supplied to the fuel cell by introducing and heating the raw material fuel, and hydrogen that has not been used for an electrochemical reaction in the fuel cell A reformer having a combustion section for generating reforming heat used for reforming the raw material fuel by introducing an anode offgas containing the combustion air and burning the anode offgas;
An inverter that converts DC power generated by the fuel cell into AC power;
A commercial power supply abnormality detecting means for detecting a commercial power supply abnormality;
When the commercial power supply abnormality detecting means detects a commercial power supply abnormality, the generated power of the fuel cell is reduced while maintaining the connection state of the relay, and the inverter is gate-blocked and the anode in the combustion unit Control is performed so that off-gas combustion is performed stably, and the inverter is connected to the gate when the abnormality of the commercial power source is resolved within a first predetermined time after the abnormality of the commercial power source is detected. the power generation output of the fuel cell is increased to a state of pre-reduction, e Bei and a control device for interrupting the relay when the first even predetermined time elapses of the commercial power failure persists;
The control device connects the relay after a third predetermined time after the commercial power supply abnormality is resolved when the abnormality of the commercial power supply is resolved within a second predetermined time period after the relay is disconnected. The inverter is connected to the gate to increase the power generation output of the fuel cell, and when the abnormality of the commercial power source is not resolved even after the second predetermined time has elapsed, the fuel cell system is shifted to the stop step. Composed;
Fuel cell system. Raw material fuel flow rate adjusting means for adjusting the amount of the raw material fuel introduced into the reformer;
Combustion air flow rate adjusting means for adjusting the amount of the combustion air introduced into the combustion section;
The control device controls the raw fuel flow rate adjusting means when the gate block is performed to reduce the amount of the raw material fuel introduced into the reformer and also controls the combustion air flow rate adjusting means. Configured to increase the amount of the combustion air introduced into the combustion section;
The fuel cell system according to claim 1. Bypass means for guiding the reformed gas generated in the reformer to the combustion section, bypassing the fuel cell;
It is connected to the fuel cell via a relay, operates by receiving power generated by the fuel cell and power supplied from the commercial power source, and is used for operating the reformer and the fuel cell. Equipped with a machine;
Until the third predetermined time elapses after the abnormality of the commercial power source is resolved, the control device maintains the non-connected state between the fuel cell and the auxiliary machine with the reformer by the bypass means. The generated reformed gas is bypassed the fuel cell and led to the combustion section to be burned, and the supply of oxygen to the fuel cell is stopped;
The fuel cell system according to claim 1 or 2 .

Images