JP6361422B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  As one type of fuel cell system, one shown in Patent Document 1 is known. As shown in FIG. 1 of Patent Document 1, such a fuel cell system includes a reforming catalyst (21a) that reforms a supplied reforming raw material to generate a reformed gas containing hydrogen. A shift catalyst (23a) for reducing the carbon monoxide concentration from the generated reformed gas, a fuel cell (10) for generating electric power using the reformed gas and air, an anode offgas and a cathode discharged from the fuel cell And a combustion catalyst (combustor 86) for burning off-gas by a catalytic reaction.

  In the fuel cell system disclosed in Patent Document 1, combustion exhaust gas discharged from a combustion catalyst is supplied to a heat exchanger and heat exchanged with a reformed gas. In this fuel cell system, when the fuel cell system is started, the reformed gas is supplied to the combustion catalyst, the reformed gas is combusted in the combustion catalyst, and the reformed gas is heated by heat exchange with the combustion exhaust gas in the heat exchanger. Let warm. Then, the temperature of the shift catalyst is raised by the heated reformed gas, and sulfur is desorbed from the sulfur-poisoned shift catalyst.

JP 2005-353348 A

  In general, such a fuel cell system is covered with a ceramic fiber heat insulating material mainly composed of silica or alumina in order to prevent heat from escaping from the fuel cell system. However, with the continuation of the operation of the fuel cell system, the silica contained in the heat insulating material is gasified by heat and water vapor generated from the fuel cell system, and the silica covers the surface of the combustion catalyst, and the surface of the fuel catalyst is silica. A film will be formed. Then, the surface of the combustion catalyst cannot be brought into contact with the combustion exhaust gas, and the catalytic reaction of the combustion catalyst is lowered.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to recover the catalytic reaction of the combustion catalyst in the fuel cell system including the combustion catalyst.

  The invention of the fuel cell system according to claim 1, which has been made to solve the above problems, includes a reforming unit that generates reformed gas from reforming water and a reforming raw material, and the reforming unit includes the reforming unit. A reforming material supply unit that supplies a reforming material, a fuel cell that generates power using the reformed gas and an oxidant gas generated by the reforming unit, and a combustible component exhausted from the fuel cell. A combustion part for combusting an anode off-gas containing an oxidant gas, a combustion catalyst for introducing a combustion exhaust gas exhausted from the combustion part, and combusting a combustible component contained in the combustion exhaust gas by a catalytic reaction; A combustion catalyst recovery section that recovers the catalytic reaction by applying a temperature change to the combustion catalyst to damage the coating that covers the combustion catalyst and inhibits the catalytic reaction;

  As described above, the combustion catalyst recovery unit applies a sudden temperature change to the combustion catalyst, thereby damaging the coating that covers the combustion catalyst and inhibits the catalytic reaction. According to this, the coating covering the combustion catalyst is damaged, the coating is cracked, or the coating is peeled off from the combustion catalyst. For this reason, the surface of the combustion catalyst can come into contact with the combustion exhaust gas, and the catalytic reaction of the combustion catalyst is recovered.

It is a schematic diagram showing an outline of one embodiment of a fuel cell system according to the present invention. It is a time chart of "combustion catalyst recovery process". 2 is a flowchart of “combustion catalyst recovery process” of the first embodiment executed by the control device shown in FIG. 1. 4 is a flowchart of “combustion catalyst recovery process” of the second embodiment executed by the control device shown in FIG. 1.

(Configuration of fuel cell system)
Hereinafter, an embodiment of the fuel cell system 100 according to the present invention will be described. As shown in FIG. 1, the fuel cell system 100 includes a power generation unit 10 and a hot water storage tank 21. The power generation unit 10 includes a housing 10a, a fuel cell module 11, a heat exchanger 12, an inverter device 13, a water tank 14, and a control device 15.

  The fuel cell module 11 includes a casing 31, an evaporation unit 32, a reforming unit 33, and a fuel cell 34. The casing 31 is formed in a box shape with a heat insulating material. In the present embodiment, the heat insulating material is composed of ceramic fibers mainly composed of silica and alumina. The evaporation unit 32 is heated by the combustion exhaust gas burned by the combustion unit 36 to be described later, evaporates the supplied reforming water to generate water vapor, and preheats the supplied reforming raw material. . The evaporation unit 32 mixes the steam generated in this way with the preheated reforming raw material and supplies the mixture to the reforming unit 33.

  One end of a reforming material supply pipe 11a is connected to the evaporation section 32. A supply source Gs is connected to the other end of the reforming material supply pipe 11a. The supply source Gs supplies a raw material for reforming. Examples of reforming raw materials include LPG (liquefied petroleum gas), reforming gas fuel such as natural gas mainly composed of methane gas, and reforming liquid fuel such as kerosene, gasoline, and methanol. The fuel cell system 100 of the present embodiment will be described with respect to an embodiment using LPG as a reforming raw material.

  The reforming material supply pipe 11a is provided with a material flow rate sensor 11a1 and a material pump 11a2 in order from the upstream. The raw material flow sensor 11 a 1 detects the flow rate of the reforming raw material supplied to the evaporation unit 32, that is, the flow rate per unit time, and transmits the detection result (detection signal) to the control device 15. . The material pump 11a2 (corresponding to the reforming material supply unit) is a device that supplies the reforming material to the reforming unit 33 by supplying the reforming material to the evaporation unit 32. The reforming raw material supply amount (supply flow rate (flow rate per unit time)) from the supply source Gs is adjusted by the control command value.

  One end of a water supply pipe 11b is connected to the evaporation section 32. The other end of the water supply pipe 11b is connected to the water tank. The water supply pipe 11b is provided with a reforming water pump 11b1. With such a configuration, the reformed water is supplied from the water tank 14 to the evaporation unit 32.

  One end of a cathode air supply pipe 11 c is connected to the fuel cell 34. A cathode air blower 11c1 is connected to the other end of the cathode air supply pipe 11c. The cathode air blower 11 c 1 (corresponding to the oxidant gas supply unit) supplies cathode air (oxidant gas) to the fuel cell 34. A cathode air flow sensor 11c2 for detecting the flow rate of cathode air supplied to the fuel cell 34 is provided on the downstream side of the cathode air blower 11c1 of the cathode air supply pipe 11c.

  The reforming unit 33 is heated by the combustion exhaust gas combusted by the combustion unit 36 to be described later and supplied with heat necessary for the steam reforming reaction, so that the mixed gas (reforming raw material) supplied from the evaporation unit 32 is supplied. , Water vapor) to generate and derive the reformed gas. The reforming unit 33 is filled with a catalyst (for example, Ru or Ni-based catalyst), and the mixed gas reacts with the catalyst to be reformed to generate a gas containing hydrogen gas and carbon monoxide. (So-called steam reforming reaction). The reformed gas contains hydrogen, carbon monoxide, carbon dioxide, steam, unreformed natural gas (methane gas), and reformed water (steam) that has not been used for reforming. As described above, the reforming unit 33 generates reformed gas (fuel) from the reforming raw material and the reformed water and supplies the reformed gas (fuel) to the fuel cell 34. The steam reforming reaction is an endothermic reaction.

  The reforming unit 33 is provided with a reforming unit temperature sensor 33a (corresponding to the reforming unit temperature detection unit) that detects the temperature of the reforming unit 33 (the temperature of the catalyst). The detection result (detection signal) of the reforming unit temperature sensor 33 a is transmitted to the control device 15.

  The fuel cell 34 generates power using the reformed gas generated by the reforming unit 33 and cathode air (oxidant gas) supplied by the cathode air blower 11c1. The fuel cell 34 is configured by laminating a fuel electrode, an air electrode (oxidant electrode), and a plurality of cells 34a made of an electrolyte interposed between the two electrodes. The fuel cell 34 of the present embodiment is a solid oxide fuel cell, and uses zirconium oxide, which is a kind of solid oxide, as an electrolyte. Hydrogen, carbon monoxide, methane gas, etc. are supplied to the fuel electrode of the fuel cell 34 as fuel. The operating temperature of the fuel cell 34 is about 400 to 1000 ° C. Not only hydrogen but also natural gas and coal gas can be used directly as fuel.

  On the fuel electrode side of the cell 34a, a fuel flow path 34b through which the reformed gas as the fuel flows is formed. An air flow path 34c through which air (cathode air) that is an oxidant gas flows is formed on the air electrode side of the cell 34a.

  The fuel cell 34 is provided on the manifold 35. The reformed gas from the reforming unit 33 is supplied to the manifold 35 via the reformed gas supply pipe 38. The lower end (one end) of the fuel flow path 34b is connected to the fuel outlet of the manifold 35, and the reformed gas led out from the fuel outlet is introduced from the lower end and led out from the upper end. . The cathode air sent out by the cathode air blower 11c1 is supplied via the cathode air supply pipe 11c, introduced from the lower end of the air flow path 34c, and led out from the upper end. The fuel cell 34 is provided with a fuel cell temperature detection sensor 34 d that detects the temperature of the fuel cell 34 and outputs the detection result (detection signal) to the control device 15. The fuel cell temperature detection sensor 34d is preferably provided at the center of the fuel cell 34 in the stacking direction.

  The combustion unit 36 is provided between the fuel cell 34, the evaporation unit 32, and the reforming unit 33. The combustion unit 36 burns anode off-gas (fuel off-gas) containing combustible components exhausted from the fuel cell 34 with cathode off-gas (oxidant off-gas) exhausted from the fuel cell 34, and uses combustion exhaust gas generated after combustion. The evaporation unit 32 and the reforming unit 33 are heated.

  In the combustion unit 36, the anode off gas is burned and a flame 37 is generated. The combustion unit 36 is provided with a pair of ignition heaters 36a1 and 36a2 for igniting the anode off gas.

  The heat exchanger 12 is a device that is supplied with the combustion exhaust gas exhausted from the fuel cell module 11 and is supplied with hot water from the hot water storage tank 21 to exchange heat between the combustion exhaust gas and the hot water. The hot water storage tank 21 stores hot water, and is connected to a hot water circulation line 22 through which the hot water circulates (circulates in the direction of the arrow in FIG. 1). On the hot water circulation line 22, a circulation pump 22 a and a heat exchanger 12 are arranged in order from the lower end to the upper end of the hot water tank 21. The heat exchanger 12 is connected to a condensed water supply pipe 12 a connected to the water tank 14.

  In the heat exchanger 12, the combustion exhaust gas from the fuel cell module 11 is introduced into the heat exchanger 12 through the combustion exhaust gas introduction part 12b, and is cooled by exchanging heat with the stored hot water. The water vapor contained in the water is condensed to produce condensed water. The combustion exhaust gas after heat exchange passes through the exhaust pipe 12c, passes through the exhaust port 10b provided in the housing 10a, and is discharged to the outside of the housing 10a. Moreover, the condensed condensed water is supplied to the water tank 14 through the condensed water supply pipe 12a. The water tank 14 purifies the condensed water with ion exchange resin.

  The heat exchanger 12, the hot water tank 21, and the hot water circulation line 22 described above constitute an exhaust heat recovery system 20. The exhaust heat recovery system 20 recovers and stores the exhaust heat of the fuel cell module 11 in hot water storage.

  A combustion catalyst 28 is provided at a portion where the inlet of the combustion exhaust gas introduction part 12 b of the heat exchanger 12 is connected to the casing 31, that is, at the outlet 31 a of the casing 31. Combustion exhaust gas exhausted from the combustion unit 36 is introduced into the combustion catalyst 28. The combustion catalyst 28 burns unburned combustible components (for example, hydrogen, methane gas, carbon monoxide, etc.) by a catalytic reaction in the combustion section 36 included in the combustion exhaust gas. The combustion catalyst 28 includes a catalyst in which a precious metal such as platinum or palladium is supported on a single ceramic body. The combustion catalyst 28 burns combustible components such as hydrogen, methane gas, and carbon monoxide not by flame combustion but by a catalytic reaction. Therefore, the combustion speed of the combustible component is high, and the combustion efficiency of the combustible component is high. Exhaust gas emission can be suppressed.

  The combustion catalyst 28 is provided with a combustion catalyst heater 28a. The combustion catalyst heater 28a is an electric heater that is heated in accordance with an instruction from the control device 15, and is used to heat the combustion catalyst 28 and raise the combustion catalyst 28 to the activation temperature of the catalyst. Further, an outlet gas temperature sensor 28b for detecting the temperature of gas exhausted from the outlet of the combustion catalyst 28 (hereinafter, abbreviated as combustion catalyst outlet gas temperature as appropriate) is provided immediately downstream of the combustion catalyst 28. ing. The detection result (detection signal) of the outlet gas temperature sensor 28 b is transmitted to the control device 15.

  The inverter device 13 sweeps the current generated by the fuel cell 34. This current is hereinafter referred to as a sweep current. The inverter device 13 converts the swept current, which is a swept DC current, into an AC current, and outputs the AC power to the power supply line 16b connected to the AC system power supply 16a and the external power load 16c (for example, an electrical appliance). To do. The inverter device 13 can detect the current value of the sweep current and can increase or decrease the sweep current amount. An alternating current from the system power supply 16a is input to the inverter device 13 through the power supply line 16b. Then, the inverter device 13 converts the input alternating current into a predetermined direct current and outputs it to an auxiliary machine (each pump, blower, heater, etc.) and the control device 15.

  The control device 15 performs overall control of the fuel cell system 100. The control device 15 controls the operation of the fuel cell system 100 by driving an auxiliary machine. The control device 15 feedback-controls the flow rate of the reforming material supplied to the evaporation unit 32 by the material pump 11a2 based on the flow rate of the reforming material to the evaporation unit 32 detected by the material flow rate sensor 11a1. Further, the control device 15 feedback-controls the flow rate of the cathode air supplied from the cathode air blower 11c1 to the fuel cell 34 based on the flow rate of the cathode air to the fuel cell 34 detected by the cathode air flow rate sensor 11c2.

  The control device 15 adjusts the flow rate of the reforming raw material supplied to the evaporation unit 32 by the raw material pump 11a2. And the control apparatus 15 adjusts the flow volume of the reforming water supplied to the evaporation part 32 by the reforming water pump 11b1. Furthermore, the control device 15 adjusts the flow rate of the cathode air supplied to the fuel cell 34 by the cathode air blower 11c1. In this way, the control device 15 adjusts the amount of heat supplied to the evaporation unit 32 and the reforming unit by adjusting the generated power generated by the fuel cell 34 and the amount of heat generated by the combustion unit 36. To do.

(Overview of combustion catalyst recovery process)
The “combustion catalyst recovery process” for recovering the catalytic reaction of the combustion catalyst 28 by damaging the silica coating covering the surface of the combustion catalyst 28 will be described below using the time chart shown in FIG. As shown in FIG. 2, the “combustion catalyst recovery process” rapidly raises the temperature of the surface of the combustion catalyst 28 (t1 to t2, t3 to t4, t5 to t6, t7 to t8, t9 to t10), and combustion. The temperature of the catalyst 28 is suddenly lowered (t2 to t3, t4 to t5, t6 to t7, t8 to t9, t10 to t11), and a sudden temperature change is repeatedly given to the combustion catalyst 28, thereby This is a treatment that damages the silica coating covering the surface. When this “combustion catalyst recovery process” is executed, the silica film covering the combustion catalyst 28 is cracked, or the silica film is peeled off from the surface of the combustion catalyst 28. Then, the surface of the combustion catalyst 28 can come into contact with the combustion exhaust gas, and the catalytic reaction of the combustion catalyst 28 is recovered. Since the temperature rise of the surface of the combustion catalyst 28 is temporary, the deterioration of the combustion catalyst 28 accompanying the temperature rise of the combustion catalyst 28 is negligibly small. Hereinafter, the “combustion catalyst recovery process” of the first embodiment will be described in detail with reference to the flowchart shown in FIG. 3.

(Combustion catalyst recovery process of the first embodiment)
When the fuel cell system 100 is turned on, the program proceeds to step S11 as shown in FIG.
In step S11, the control device 15 determines that the operation time of the fuel cell system 100 has exceeded a specified time (for example, 10,000 hours) since the previous “combustion catalyst recovery process” (process after step S21). If so (step S11: YES), the program proceeds to step S12. On the other hand, if the control device 15 determines that the operation time of the fuel cell system 100 has not exceeded the specified time since the previous “combustion catalyst recovery process” (step S11: NO), step S11 is performed. Repeat the process.

  In step S12, when the control device 15 determines that the fuel cell system 100 is on standby (step S12: YES), the control device 15 advances the program to step S13. On the other hand, when the control device 15 determines that the fuel cell system 100 is not in operation standby (step S12: NO), the process of step S12 is repeated. The operation standby state is a state before the start-up operation in preparation for power generation in the fuel cell 34 and a standby state in which power generation in the fuel cell 34 is stopped. In this way, only when the fuel cell system 100 is on standby, the control device 15 executes the processes after step S13. On the other hand, when the fuel cell system 100 is in the start-up operation described above, in the power generation operation in which the fuel cell 34 is generating power, or in the operation stop in which the power generation of the fuel cell 34 is stopped, the control device 15 Does not execute the processing after step S13.

  In step S13, based on the detection result from the fuel cell temperature detection sensor 34d, the control device 15 detects that the temperature of the fuel cell 34 is lower than the ignition temperature (for example, 300 ° C.) and the reforming unit temperature sensor 33a. If it is determined that the temperature of the reforming unit 33 is lower than the coking generation temperature (for example, 100 ° C.) based on the result (step S13: YES), the program proceeds to step S21. On the other hand, when the control device 15 determines that the temperature of the fuel cell 34 is equal to or higher than the ignition temperature, or the temperature of the reforming unit 33 is equal to or higher than the coking occurrence temperature (step S13: NO), the control device 15 Repeat the process. When the temperature of the fuel cell 34 is lower than the ignition temperature, the anode off gas (reforming raw material) that has passed through the fuel flow path 34 b does not spontaneously ignite in the combustion unit 36. Further, when the temperature of the reforming section 33 is lower than the coking generation temperature, even if the reforming raw material is supplied to the reforming section 33, the occurrence of coking by the reforming raw material is suppressed in the reforming section 33. Is done.

  In step S21, the control device 15 drives the cathode air blower 11c1 to start supplying cathode air to the fuel cell 34. By the processing in step S21, supply of cathode air to the combustion catalyst 28 is started.

  In step S22, the control device 15 turns on the combustion catalyst heater 28a. By the process of step S22, the combustion catalyst 28 is raised in temperature toward the activation temperature of the catalyst.

  In step S23, when the control device 15 determines that the combustion catalyst outlet gas temperature is equal to or higher than the catalyst activation temperature (for example, 200 ° C.) based on the detection result of the outlet gas temperature sensor 28b (step S23: YES). Then, the program proceeds to step S24. On the other hand, when it is determined that the combustion catalyst outlet gas temperature is lower than the catalyst activation temperature (step S23: NO), the control device 15 repeats the process of step S23. When the combustion catalyst outlet gas temperature is equal to or higher than the catalyst activation temperature, the surface of the combustion catalyst 28 is equal to or higher than the catalyst activation temperature, and the combustion catalyst 28 can combust combustible components.

  In step S24, the control device 15 starts the temperature raising process for raising the temperature of the surface of the combustion catalyst 28 by driving the raw material pump 11a2 and starting the supply of the raw material for reforming to the reforming unit 33. . In the process of step S24, the reforming raw material supplied to the reforming unit 33 is not reformed in the reforming unit 33, is not used for power generation in the fuel cell 34, and is not burned in the combustion unit 36. For this reason, the anode off-gas containing a large amount of combustible components is supplied to the combustion catalyst 28, and this anode off-gas is combusted by the catalytic reaction in the combustion catalyst 28, and a large amount of combustion heat is generated in the combustion catalyst 28. The raw material pump 11a2 supplies the reforming raw material so that the surface temperature of the combustion catalyst 28 is raised at a first temperature gradient α or higher. The first temperature gradient α is a value obtained by dividing the temperature change Δα per unit time Δt by the unit time Δt (α = Δα / Δt (shown in FIG. 2)), for example, 10 ° C./s. . When the temperature of the surface of the combustion catalyst 28 is increased by a rapid temperature change such as the first temperature gradient α or more, the silica coating covering the surface of the combustion catalyst 28 is surely damaged.

  In step S31, when the control device 15 determines that the combustion catalyst outlet gas temperature is equal to or higher than a specified temperature increase temperature (for example, 400 ° C.) based on the detection result of the outlet gas temperature sensor 28b (step S31: YES). ), The program proceeds to step S32. On the other hand, when the control device 15 determines that the combustion catalyst outlet gas temperature is lower than the specified temperature increase temperature (step S31: NO), the process of step S31 is repeated. There is a correlation between the combustion catalyst outlet gas temperature and the surface temperature of the combustion catalyst 28. For this reason, when the combustion catalyst outlet gas temperature reaches the specified temperature rise temperature, the surface temperature of the combustion catalyst 28 is raised to the second temperature T2 (for example, 800 ° C.) or more shown in FIG. Thus, when the surface temperature of the combustion catalyst 28 is raised to the second temperature T2 or higher, the silica film covering the surface of the combustion catalyst 28 is surely damaged.

  In step S32, the control device 15 stops the raw material pump 11a2, and stops the supply of the raw material for reforming to the reforming unit 33. By the processing in step S32, the supply of the anode off gas containing a large amount of combustible components to the combustion catalyst 28 is stopped, and the generation of combustion heat in the combustion catalyst 28 is stopped.

  In step S33, the control device 15 starts a temperature lowering process for lowering the temperature of the combustion catalyst 28 by turning off the combustion catalyst heater 28a. By the process of step S33, the supply of heat to the combustion catalyst 28 by the combustion catalyst heater 28a is stopped, the cathode air is supplied to the combustion catalyst 28 by the cathode air blower 11c1, and the surface of the combustion catalyst 28 is cooled. Lower the temperature. The cathode air blower 11c1 supplies cathode air so that the surface temperature of the combustion catalyst 28 falls below the second temperature gradient β. The second temperature gradient β is a value obtained by dividing the temperature change Δβ per unit time Δt by the unit time Δt (β = Δβ / Δt (shown in FIG. 2)), for example, at −10 ° C./s. is there. If the temperature of the surface of the combustion catalyst 28 is lowered by a rapid temperature change such as less than the second temperature gradient β, the silica film covering the surface of the combustion catalyst 28 is surely damaged. When the temperature change Δβ is taken as an absolute value, the cathode air blower 11c1 supplies the cathode air so that the surface temperature of the combustion catalyst 28 falls with a second temperature gradient β or more.

  In step S41, when the control device 15 determines that the combustion catalyst outlet gas temperature is equal to or lower than a specified temperature drop temperature (for example, 250 ° C.) based on the detection result of the outlet gas temperature sensor 28b (step S41: YES). Then, the program proceeds to step S42. On the other hand, when it is determined that the combustion catalyst outlet gas temperature is higher than the specified temperature drop temperature (step S41: NO), the control device 15 repeats the process of step S41. When the combustion catalyst outlet gas temperature reaches the specified temperature drop temperature, the surface temperature of the combustion catalyst 28 has fallen below the first temperature T1 (for example, 250 ° C.) shown in FIG. When the surface temperature of the combustion catalyst 28 falls below the first temperature T1, the silica coating covering the surface of the combustion catalyst 28 is surely damaged.

In step S42, the control device 15 adds 1 to the counter.
In step S43, if the control device 15 determines that the counter has exceeded a specified number of times (for example, 5 times) (step S43: YES), the control device 15 advances the program to step S44. On the other hand, when the control device 15 determines that the counter does not exceed the specified number of times (step S43: NO), the control device 15 returns the program to step S22. In this way, the processes in steps S22 to S41 are repeated a specified number of times until the counter exceeds the specified number. As a result, the surface of the combustion catalyst 28 is repeatedly heated and lowered repeatedly, and the silica coating covering the surface of the combustion catalyst 28 is sufficiently damaged. As a result, the silica coating is cracked or the silica coating is peeled off from the surface of the combustion catalyst 28.

  In step S44, the control device 15 stops the supply of cathode air by the cathode air blower 11c1.

(Effect of this embodiment)
As is apparent from the above description, the control device 15 (combustion catalyst recovery unit) applies a sudden temperature change to the combustion catalyst 28 as shown in FIG. Damage to the impairing silica coating. According to this, the silica coating covering the combustion catalyst 28 is damaged, the silica coating is cracked, or the silica coating is peeled off from the combustion catalyst 28. For this reason, the surface of the combustion catalyst 28 can come into contact with the combustion exhaust gas, and the catalytic reaction of the combustion catalyst 28 is recovered.

  The control device 15 (combustion catalyst recovery unit) supplies the reforming raw material to the reforming unit 33 by the raw material pump 11a2 (reforming raw material supply unit) (step S24 in FIG. 3). The combustion catalyst 28 is heated by burning the combustible components contained in the catalyst. According to this, since the combustible component is burned by a catalytic reaction in which the combustion speed of the combustible component is high and the combustion efficiency of the combustible component is high, the temperature of the surface of the combustion catalyst 28 rises with a rapid temperature gradient, The silica coating that coats and inhibits the catalytic reaction is reliably damaged.

  The control device 15 (combustion catalyst recovery unit) lowers the temperature of the combustion catalyst 28 by supplying cathode air (oxidant gas) to the combustion catalyst 28 by the cathode air blower 11c1 (oxidant gas supply unit). According to this, not only when the temperature of the combustion catalyst 28 is raised but also when the temperature of the combustion catalyst 28 is lowered, a sudden temperature change can be given to the combustion catalyst 28, and the silica film covering the combustion catalyst 28 can be obtained. Damage more reliably. Further, the silica film covering the combustion catalyst 28 is damaged in a shorter time.

  The control device 15 (combustion catalyst recovery unit) determines that the anode off gas does not ignite in the combustion unit 36, that is, if the temperature of the fuel cell 34 is lower than the ignition temperature (determined as YES in step S13 in FIG. 3). The temperature raising process for raising the temperature of the surface of the combustion catalyst 28 by supplying the reforming raw material to the reforming unit 33 by the raw material pump 11a2 (reforming raw material supply unit) and burning the anode off-gas in the combustion catalyst 28 Execute. According to this, the anode off gas containing a large amount of combustible components is supplied to the combustion catalyst 28 without burning the anode off gas in the combustion section 36. Then, compared with the case where the anode off gas is burned in the combustion unit 36, the anode off gas containing a large amount of combustible components is burned by the catalytic reaction in the combustion catalyst 28. As a result, a large amount of combustion heat is generated in the combustion catalyst 28, and the temperature of the surface of the combustion catalyst 28 is raised with a rapid temperature gradient. For this reason, the silica film which coat | covers the combustion catalyst 28 and inhibits a catalytic reaction is damaged more reliably, and the catalytic reaction of the combustion catalyst 28 recovers more reliably.

  The control device 15 (combustion catalyst recovery unit) determines that the temperature of the reforming unit 33 is a temperature at which coking of the reforming material to the reforming unit 33 does not occur (determined as YES in step S13 of FIG. 3). Then, the raw material pump 11a2 (reforming raw material supply unit) supplies the reforming raw material to the reforming unit 33, burns the anode off-gas in the combustion catalyst 28, and executes the temperature raising process for raising the temperature of the combustion catalyst 28. To do. According to this, the occurrence of 33 coking in the reforming unit accompanying the supply of the reforming raw material to the reforming unit 33 is suppressed.

  The control device 15 (combustion catalyst recovery unit) gives an abrupt temperature change to the combustion catalyst 28 during operation standby in which power generation in the fuel cell 34 is stopped (YES in step S12 in FIG. 3). "Recovery process" (process after step S21) is executed. According to this, the startup of the fuel cell 34 is not delayed compared to the case where the “combustion catalyst recovery process” is executed during the startup operation of the fuel cell 34. Further, since the temperature of the combustion catalyst 28 is raised during the operation standby in which the temperature of the combustion catalyst 28 is lower than that during the power generation of the fuel cell 34, the temperature rising gradient of the combustion catalyst 28 becomes steep and the combustion catalyst 28 The silica coating that coats 28 and inhibits the catalytic reaction is more reliably damaged.

(Combustion catalyst recovery process of the second embodiment)
The difference between the “combustion catalyst recovery process” of the second embodiment and the “combustion catalyst recovery process” of the first embodiment will be described below. In the “combustion catalyst recovery process” of the second embodiment, instead of burning the combustible component contained in the anode off-gas in the combustion catalyst 28 to raise the temperature of the combustion catalyst 28, the temperature of the combustion catalyst 28 is directly raised by the combustion catalyst heater 28a. Let
Hereinafter, the “combustion catalyst recovery process” of the second embodiment will be described in detail with reference to the flowchart shown in FIG. 4.

  When the fuel cell system 100 is powered on, the program proceeds to step S111 as shown in FIG. The processing of step S111 and step S112 is the same processing as the processing of step S11 and step S12 shown in FIG. 3 of the first embodiment, respectively.

  When the determination is YES in step S112, the control device 15 turns on the combustion catalyst heater 28a in step S122, thereby starting a temperature raising process for raising the temperature of the surface of the combustion catalyst 28. The combustion catalyst heater 28a heats the combustion catalyst 28 so that the surface temperature of the combustion catalyst 28 rises above the first temperature gradient α. When the surface temperature of the combustion catalyst 28 is increased by a rapid temperature change such as the first temperature gradient α or more, the silica coating covering the combustion catalyst 28 is surely damaged. By the process of step S122, the combustion catalyst 28 is heated from the temperature equal to or lower than the first temperature T1 toward the second temperature T2 (shown in FIG. 2).

  In step S123, when the control device 15 determines that the combustion catalyst outlet gas temperature is equal to or higher than a specified temperature increase temperature (for example, 400 ° C.) based on the detection result of the outlet gas temperature sensor 28b (step S123: YES). ), The program proceeds to step S133. On the other hand, when the control device 15 determines that the combustion catalyst outlet gas temperature is lower than the specified temperature increase temperature (step S123: NO), the process of step S123 is repeated. When the combustion catalyst outlet gas temperature reaches the specified temperature rise temperature, the surface temperature of the combustion catalyst 28 is raised to a second temperature T2 (for example, 800 ° C.) or higher shown in FIG. When the surface temperature of the combustion catalyst 28 rises to the second temperature T2 or higher, the silica film covering the surface of the combustion catalyst 28 is surely damaged.

  In step S133, the control device 15 turns off the combustion catalyst heater 28a. By the process of step S133, the supply of heat to the combustion catalyst 28 by the combustion catalyst heater 28a is stopped.

  In step S134, the control device 15 starts the temperature lowering process for lowering the temperature of the combustion catalyst 28 by driving the cathode air blower 11c1 and starting the supply of the cathode air to the fuel cell 34. Through the processing in step S134, cathode air is supplied to the combustion catalyst 28, and the surface of the combustion catalyst 28 is cooled and the temperature is lowered. The cathode air blower 11c1 supplies the cathode air so that the surface temperature of the combustion catalyst 28 falls below the second temperature gradient β. If the temperature of the surface of the combustion catalyst 28 is lowered by a rapid temperature change such as less than the second temperature gradient β, the silica film covering the surface of the combustion catalyst 28 is surely damaged.

  In step S141, when the control device 15 determines that the combustion catalyst outlet gas temperature is equal to or lower than a specified temperature drop temperature (for example, 250 ° C.) based on the detection result of the outlet gas temperature sensor 28b (step S141: YES). Then, the program proceeds to step S142. On the other hand, when it is determined that the combustion catalyst outlet gas temperature is higher than the specified temperature drop temperature (step S141: NO), the control device 15 repeats the process of step S141. When the combustion catalyst outlet gas temperature reaches the specified temperature drop temperature, the surface temperature of the combustion catalyst 28 is lowered to a first temperature T1 (for example, 250 ° C.) or less shown in FIG. When the surface temperature of the combustion catalyst 28 falls below the first temperature T1, the silica coating covering the surface of the combustion catalyst 28 is surely damaged.

  The processes of step S142, step S143, and step S144 are the same as the processes of step S42, step S43, and step S44 shown in FIG. 3 of the first embodiment, respectively. However, in step S143, if the counter exceeds the specified number of times, the program returns to step S111. If the counter does not exceed the specified number of times, the program proceeds to step S144. By such processing of step S142 to step S144, the processing of step S122 to step S141 is repeated a specified number of times. As a result, the surface of the combustion catalyst 28 is repeatedly heated and lowered repeatedly, and the silica coating covering the surface of the combustion catalyst 28 is sufficiently damaged. As a result, the silica coating is cracked or the silica coating is peeled off from the surface of the combustion catalyst 28.

  As is apparent from the above description, the control device 15 (combustion catalyst recovery unit) heats the combustion catalyst 28 by the combustion catalyst heater 28a, thereby raising the temperature of the combustion catalyst 28. According to this, the temperature of the combustion catalyst 28 is reliably increased, and the silica coating that covers the combustion catalyst 28 and inhibits the catalytic reaction is surely damaged. Further, since the temperature of the combustion catalyst 28 is raised by the electric combustion catalyst heater 28a, the reforming raw material is not consumed to raise the temperature of the combustion catalyst 28. Moreover, if electric power in a time zone with a low electricity bill, for example, midnight electric power, is used for the combustion catalyst heater 28a, the catalytic reaction of the combustion catalyst 28 can be recovered at low cost.

(Another embodiment)
In the “combustion catalyst recovery process” of the first embodiment described above, when the condition that the anode off gas does not ignite in the combustion section 36 is satisfied (YES determination in step S13 in FIG. 3), the raw material for reforming is supplied by the raw material pump 11a2. The fuel is supplied to the reforming unit 33, and the combustible component is combusted in the combustion catalyst 28 without igniting the anode off-gas in the combustion unit 36, thereby raising the temperature of the combustion catalyst 28. However, there may be an embodiment in which the anode off gas is combusted in the combustion unit 36 and the combustible component contained in the combustion exhaust gas is combusted in the combustion catalyst 28 to raise the temperature of the combustion catalyst 28.

  In the embodiment described above, the temperature increase and the temperature decrease of the combustion catalyst 28 are repeated a specified number of times to damage the silica film covering the surface of the combustion catalyst 28. However, there is no problem even in an embodiment in which the silica film covering the surface of the combustion catalyst 28 is damaged by raising and lowering the temperature of the combustion catalyst 28 only once. Further, in a state where the surface temperature of the combustion catalyst 28 is equal to or lower than the first temperature T1, the surface temperature of the combustion catalyst 28 is raised only once with a temperature gradient equal to or higher than the first temperature gradient α to the second temperature T2 or higher, An embodiment in which the silica coating covering the surface of the combustion catalyst 28 is damaged may be used. Further, in the state where the surface temperature of the combustion catalyst 28 is equal to or higher than the second temperature T2, the surface temperature of the combustion catalyst 28 is lowered only once with a temperature gradient less than the second temperature gradient β to the first temperature T1 or less, and combustion An embodiment in which the silica film covering the surface of the catalyst 28 is damaged may be used.

  An embodiment using methane gas as the reforming raw material may be used. In this embodiment, the ignition temperature in step S13 of FIG. 3 is, for example, 400 ° C., the catalyst activation temperature in step S23 is, for example, 400 ° C., the specified temperature increase temperature in step S31 is, for example, 500 ° C., and in step S41 The specified temperature drop temperature is 450 ° C., for example.

  In the embodiment described above, in step S11 of FIG. 3 or step S111 of FIG. 4, the operation time of the fuel cell system 100 executes the previous “combustion catalyst recovery process” (the process after step S21 or step S122). When the specified time is exceeded, the program proceeds to step S12 or step S112, and “combustion catalyst recovery process” is executed. However, there may be an embodiment in which the “combustion catalyst recovery process” is executed when a decrease in the catalytic reaction of the combustion catalyst 28 is detected. In this embodiment, for example, carbon monoxide contained in the gas is detected by a carbon monoxide concentration sensor (not shown) that detects the concentration of carbon monoxide contained in the gas exhausted from the outlet of the combustion catalyst 28. When the predetermined value is exceeded, a decrease in the catalytic reaction of the combustion catalyst 28 is detected.

  In the embodiment described above, the “combustion catalyst recovery process” is executed while the fuel cell system 100 is on standby. However, the “combustion catalyst recovery process” may be an embodiment that is executed during start-up operation or shutdown of the fuel cell system 100.

  In the embodiment described above, the temperature of the combustion catalyst 28 is increased or decreased during the temperature increasing process or the temperature decreasing process. However, there may be an embodiment in which the temperature of the surface of the combustion catalyst 28 is raised or lowered by raising or lowering the temperature inside the combustion catalyst 28 in the temperature raising process or the temperature lowering process.

  Instead of the outlet gas temperature sensor 28b, a combustion catalyst temperature sensor (not shown) for directly detecting the temperature of the combustion catalyst 28 may be provided. In this embodiment, in step S23 of FIG. 3, the control device 15 determines whether or not the surface temperature of the combustion catalyst 28 is equal to or higher than the activation temperature of the catalyst based on the detection result from the combustion catalyst temperature sensor. In step S31 of FIG. 3 and step S123 of FIG. 4, the control device 15 increases the surface temperature of the combustion catalyst 28 to the second temperature T2 or more shown in FIG. 2 based on the detection result from the combustion catalyst temperature sensor. Determine if it is warm. Further, in step S41 of FIG. 3 or step S141 of FIG. 4, the control device 15 lowers the surface temperature of the combustion catalyst 28 below the first temperature T1 shown in FIG. 2 based on the detection result from the combustion catalyst temperature sensor. Judge whether or not.

  In the above description, the present invention has been described with respect to an embodiment in which the silica film covering the surface of the combustion catalyst 28 is damaged. However, the technical idea of the present invention can be applied to any coating that covers the surface of the combustion catalyst 28 and inhibits the catalytic reaction and is damaged by applying a sudden temperature change.

  Raw material pump 11a2 (reforming raw material supply unit), 11c1 ... cathode air blower (oxidant gas supply unit), 15 ... control device (combustion catalyst recovery unit), 28 ... combustion catalyst, 28a ... combustion catalyst heater, 33 ... modified 33, a reforming part temperature sensor (reforming part temperature detecting part), 34 ... a fuel cell, 36 ... a combustion part.

Claims (7)

A reforming section for generating a reformed gas from the reforming water and the reforming raw material;
A reforming material supply unit for supplying the reforming material to the reforming unit;
A fuel cell that generates electric power from the reformed gas and the oxidant gas generated by the reforming unit;
A combustion section for burning an anode off-gas containing combustible components exhausted from the fuel cell with an oxidant gas;
Combustion catalyst in which combustion exhaust gas exhausted from the combustion section is introduced, and combustible components contained in the combustion exhaust gas are combusted by a catalytic reaction;
A fuel cell system comprising: a combustion catalyst recovery section that recovers the catalytic reaction by applying a rapid temperature change to the combustion catalyst to damage the coating that covers the combustion catalyst and inhibits the catalytic reaction.   The combustion catalyst recovery unit supplies the reforming material to the reforming unit by the reforming material supply unit, and burns the combustible component contained in the anode offgas in the combustion catalyst, thereby The fuel cell system according to claim 1, wherein a temperature raising process for raising the temperature of the combustion catalyst is executed, and the sudden temperature change is given to the combustion catalyst. A combustion catalyst heater for heating the combustion catalyst;
2. The combustion catalyst recovery unit performs a temperature increasing process for heating the combustion catalyst by heating the combustion catalyst with the combustion catalyst heater, and gives the sudden temperature change to the combustion catalyst. The fuel cell system described in 1. An oxidant gas supply unit for supplying an oxidant gas to the combustion catalyst;
The combustion catalyst recovery unit supplies the oxidant gas to the combustion catalyst by the oxidant gas supply unit, and executes a temperature lowering process for lowering the temperature of the combustion catalyst, thereby causing the rapid temperature change to occur in the combustion The fuel cell system according to any one of claims 1 to 3, which is applied to the catalyst.   In the combustion catalyst, the combustion catalyst recovery unit supplies the reforming material to the reforming unit by the reforming material supply unit when the anode off gas does not ignite in the combustion unit. 3. The fuel cell system according to claim 2, wherein the temperature increasing process for increasing the temperature of the combustion catalyst is performed by burning the anode off gas. It further has a reforming unit temperature detection unit for detecting the temperature of the reforming unit,
The combustion catalyst recovery unit increases the temperature when the temperature of the reforming unit detected by the reforming unit temperature detection unit is a temperature at which coking of the reforming material to the reforming unit does not occur. The fuel cell system according to claim 2 or 5, wherein the temperature process is performed.   The fuel according to any one of claims 1 to 6, wherein the combustion catalyst recovery unit applies the rapid temperature change to the combustion catalyst during operation standby in which the power generation in the fuel cell is stopped. Battery system.

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