WO2020079833A1 - Fuel cell system and method for operating fuel cell system - Google Patents

Fuel cell system and method for operating fuel cell system Download PDF

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Publication number
WO2020079833A1
WO2020079833A1 PCT/JP2018/039012 JP2018039012W WO2020079833A1 WO 2020079833 A1 WO2020079833 A1 WO 2020079833A1 JP 2018039012 W JP2018039012 W JP 2018039012W WO 2020079833 A1 WO2020079833 A1 WO 2020079833A1
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WIPO (PCT)
Prior art keywords
reformer
fuel cell
catalyst
cell system
deterioration
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PCT/JP2018/039012
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French (fr)
Japanese (ja)
Inventor
文雄 各務
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日産自動車株式会社
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Priority to PCT/JP2018/039012 priority Critical patent/WO2020079833A1/en
Publication of WO2020079833A1 publication Critical patent/WO2020079833A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
    • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to a fuel cell system and a method of operating the fuel cell system.
  • Patent Document 1 discloses a fuel cell system in which an oxidizing agent is introduced into a reformer to oxidize and remove deposited carbon as a measure against carbon deposition.
  • Patent Document 1 the fuel cell system disclosed in Patent Document 1 above is a measure specialized only for carbon deposition, and cannot be dealt with when there are other factors that reduce the reforming performance.
  • An object of the present invention is to provide a fuel cell system and a method of operating the fuel cell system, which can cope with various factors that deteriorate the reforming performance of the reformer.
  • the fuel cell system of the present invention for achieving the above object is a fuel cell system that reforms fuel with a reformer equipped with a catalyst and supplies the reformed fuel to a fuel cell stack to generate electricity.
  • the fuel cell system includes a deterioration recovery means for supplying an oxidant gas to the reformer to recover deterioration of the catalyst of the reformer, and a deterioration recovery detection for detecting a recovery state of the catalyst by the deterioration recovery means.
  • Means and operating condition changing means for changing the operating condition so as to promote the reaction of the reformer, based on a detection signal from the deterioration recovery detecting means indicating that the catalyst is in an unrecovered state. Have.
  • a method of operating a fuel cell system of the present invention to achieve the above object when deterioration of a catalyst of a reformer for reforming fuel is detected, supplying an oxidant gas to the reformer, The recovery state of the catalyst of the reformer supplied with the oxidant is detected, and when the catalyst is in the non-recovery state, the operating condition is changed so as to accelerate the reaction of the reformer.
  • FIG. 1 is a schematic configuration diagram showing the fuel cell system according to the first embodiment.
  • a fuel cell system 100 according to an embodiment of the present invention will be described with reference to FIG.
  • the fuel cell system 100 shown in FIG. 1 reforms a fuel to generate a reformed gas RG, and supplies the reformed gas RG and the oxidant gas OG to the fuel cell stack 10 to generate electric power.
  • the reformed gas RG is an anode gas supplied to the anode electrode of the fuel cell stack 10.
  • the oxidant gas OG is a cathode gas supplied to the cathode electrode of the fuel cell stack 10.
  • the oxidant gas OG is composed of oxygen, air containing oxygen, or the like.
  • the fuel cell stack 10 of the present embodiment is applied to a solid oxide fuel cell (SOFC: Solid Oxide Fuel Cell) mounted on an automobile. Since SOFC can use not only hydrogen but also carbon monoxide and methane as an anode gas, the power generation efficiency of the fuel cell system 100 can be improved.
  • SOFC Solid Oxide Fuel Cell
  • the fuel is not particularly limited as long as it can be used as the anode gas by reforming to be used for power generation of the fuel cell stack 10.
  • ethanol which is an oxygen-containing hydrocarbon fuel
  • a case where the reformed gas RG is generated using the liquid water-containing fuel MW in which the fuel and water are mixed will be described as an example.
  • the fuel cell system 100 includes a reformer 24 including a catalyst, a deterioration recovery unit that supplies an oxidant gas OG to the reformer 24 to recover the deterioration of the catalyst of the reformer 24, and a catalyst using the deterioration recovery unit.
  • a deterioration recovery detection means for detecting the recovery state of the catalyst and the detection signal from the deterioration recovery detection means indicating that the catalyst is in the unrecovered state, the operating conditions are changed so as to accelerate the reaction of the reformer 24.
  • Operating condition changing means are used.
  • the fuel cell system 100 includes a fuel tank 21 that stores a water-containing fuel MW, an evaporator 23 that evaporates the water-containing fuel MW, and a water-containing fuel MW. Reformer 24 for generating reformed gas RG, oxidant supply unit 31 for supplying oxidant gas OG, heat exchanger 32, and exhaust combustor 41 for burning exhaust gas EG of fuel cell stack 10. , And a control unit 50.
  • a flow rate adjusting unit 22 that adjusts the supply amount of the water-containing fuel MW is arranged between the fuel tank 21 and the evaporator 23.
  • “between A and B” means “in the middle of the flow path for flowing the fluid from A to B”.
  • a temperature sensor 25 that detects the inlet temperature and the outlet temperature of the reformer 24 is attached to the reformer 24.
  • the water-containing fuel MW in the fuel tank 21 is supplied to the evaporator 23 by the flow rate adjusting unit 22 and is vaporized into a mixed gas MG containing water vapor and fuel gas.
  • the mixed gas MG is supplied to the reformer 24.
  • the reformer 24 produces hydrogen-rich reformed gas RG from the mixed gas MG by steam reforming.
  • the reformed gas RG is supplied to the fuel cell stack 10 as an anode gas.
  • the oxidant gas OG supplied from the oxidant supply unit 31 is branched by the oxidant gas control valve 43 into the two flow paths 31a and 31b.
  • the oxidant gas OG passing through the flow path 31a is supplied to the heat exchanger 32, heated in the heat exchanger 32, and then supplied to the fuel cell stack 10 as cathode gas.
  • the oxidant gas OG passing through the flow path 31b is supplied upstream of the reformer 24.
  • the exhaust gas of the anode gas and the exhaust gas of the cathode gas discharged from the fuel cell stack 10 are respectively supplied to the exhaust combustor 41.
  • the exhaust gas EG burned in the exhaust combustor 41 after passing through the heat exchanger 32, has two flow passages 32a and 32b: a main flow passage 32a flowing to the reformer 24 and a bypass flow passage 32b flowing to the evaporator 23. Is diverted to and shed.
  • An exhaust control valve 42 that adjusts the distribution amount of the exhaust gas EG to the reformer 24 and the evaporator 23 is arranged at the branch point of the two flow paths 32a and 32b.
  • the exhaust gas EG passing through the main flow path 32a is heat-exchanged with the mixed gas MG in the reformer 24 and the evaporator 23 in order, and then discharged from the evaporator 23 to the outside of the fuel cell system 100.
  • the exhaust gas EG passing through the bypass flow path 32b exchanges heat with the mixed gas MG in the evaporator 23, and then is discharged from the evaporator 23 to the outside of the fuel cell system 100.
  • the oxidant supply unit 31 corresponds to “deterioration recovery means” that supplies the oxidant gas OG to the reformer 24 to recover the deterioration of the catalyst of the reformer 24.
  • the temperature sensor 25 corresponds to "deterioration recovery detection means” for detecting the recovery state of the catalyst by the deterioration recovery means.
  • the exhaust combustor 41 and the exhaust control valve 42 correspond to “operating condition changing means” that changes the operating conditions so as to promote the reaction of the reformer 24.
  • the fuel tank 21 stores a water-containing fuel MW that is a mixture of fuel and water. By mixing and storing fuel and water, it is not necessary to separately provide a fuel tank for storing fuel and a water storage tank for storing water. Thereby, the configuration of the fuel cell system 100 can be simplified and downsized.
  • the fuel tank 21 may be provided with a concentration sensor that detects the composition of the fuel and water in the water-containing fuel MW.
  • the flow rate adjusting unit 22 is composed of an electric pump that takes out the water-containing fuel MW stored in the fuel tank 21 and supplies it to the evaporator 23 while adjusting the supply amount.
  • the flow rate adjusting unit 22 is configured to be able to adjust the supply amount of the water-containing fuel MW to the evaporator 23 based on the control signal from the control unit 50.
  • the evaporator 23 vaporizes the water-containing fuel MW supplied from the flow rate adjusting unit 22 to generate a mixed gas MG containing water vapor and fuel.
  • the evaporator 23 is heated by the exhaust gas EG from the exhaust combustor 41.
  • the exhaust gas EG flowing into the evaporator 23 is discharged to the outside of the fuel cell system 100.
  • the exhaust gas EG supplied to the evaporator 23 passes through the main passage 32a, the reformer 24 and the exhaust gas EG supplied to the evaporator 23, and the exhaust gas EG passes through the bypass passage 32b.
  • the exhaust gas EG directly supplied to the container 23 at least one of the exhaust gas EG is configured.
  • the evaporator 23 may be heated by using a heating device such as an electric heater.
  • the reformer 24 has a catalyst that accelerates the reforming reaction.
  • the reformer 24 reforms the mixed gas MG supplied from the evaporator 23 to generate the reformed gas RG supplied to the fuel cell stack 10.
  • the fuel gas and steam in the mixed gas MG cause a catalytic reaction to generate reformed gas RG by steam reforming.
  • the reformer 24 of the present embodiment steam-reforms ethanol, which is a fuel, to produce hydrogen (H 2 ), carbon monoxide (CO), and methane (CH 4 ) that are anode gases of the fuel cell stack 10. To generate.
  • the reformer 24 reforms the mixed gas MG of ethanol (C 2 H 5 OH) and steam (H 2 O) to contain hydrogen (H 2 ), carbon monoxide (CO) and methane (CH 4 ).
  • a steam reforming reaction that produces the reformed gas RG occurs.
  • operating the reformer 24 mainly by a steam reforming reaction is referred to as "normal operation”.
  • the operating temperature of the reformer 24 during normal operation is about 550 ° C. to 600 ° C., although it depends on the constituent material of the fuel and the type of catalyst.
  • the steam reforming reaction is shown as an overall reaction by the progress of the following multiple reactions.
  • the reforming performance of the reformer 24 may decrease due to various factors.
  • “reduction of the reforming performance of the reformer 24” means that the reforming reaction is less likely to proceed and the selectivity of the reforming reaction, the conversion rate of fuel, and the like are reduced.
  • the selectivity of the reforming reaction means the rate of selecting a reaction path that produces a reformed gas RG such as hydrogen used for power generation of the fuel cell stack 10 in the entire reaction of the reformer 24. .
  • Factors that deteriorate the reforming performance of the reformer 24 include deterioration of the catalyst, composition change of the water-containing fuel MW, low operating temperature (reforming temperature), fuel (mixed gas MG in this embodiment) and catalyst.
  • the contact time is short.
  • the composition of the water-containing fuel MW may change over time due to differences in the volatility of the fuel and water.
  • the reforming performance of the reformer 24 tends to improve as the operating temperature is higher and the contact time between the fuel and the catalyst is longer.
  • the deterioration of the catalyst includes the reduction of the effective specific surface area of the catalyst and the structural change of the catalyst base material.
  • Factors that reduce the effective specific surface area of the catalyst include carbon deposition and sintering of the catalyst metal. When carbon is deposited on the surface of the catalyst, the catalytic reaction is less likely to occur in the portion coated with carbon, and the effective specific surface area is reduced. Further, when the catalytic metal causes sintering, the effective specific surface area is geometrically reduced. Further, when the structure of the catalyst base material changes, the flow of the water-containing fuel MW may be blocked and the water-containing fuel MW may not reach the effective surface of the catalyst.
  • the fuel cell system 100 of the present embodiment is configured so as to cope with not only carbon deposition but also sintering of the catalyst metal and structural change of the catalyst base material as the catalyst deterioration factor.
  • the temperature sensor 25 has an inlet temperature sensor 25a for measuring the inlet temperature of the reformer 24 into which the mixed gas MG flows, and an outlet temperature sensor 25b for measuring the outlet temperature of the reformer 24 from which the mixed gas MG flows out. .
  • the inlet temperature sensor 25a detects the temperature of the mixed gas MG supplied to the reformer 24 and outputs the detected value to the control unit 50.
  • the outlet temperature sensor 25b detects the temperature of the reformed gas RG discharged from the reformer 24 and outputs the detected value to the control unit 50.
  • the inlet temperature sensor 25a and the outlet temperature sensor 25b may be integrally configured.
  • the oxidant supply unit 31 supplies an oxidant gas OG composed of oxygen or air.
  • the oxidant supply unit 31 of the present embodiment is composed of a blower that sucks air from the outside and supplies the air to the fuel cell stack 10 or the reformer 24.
  • the heat exchanger 32 heats the oxidant gas OG by exchanging heat between the oxidant gas OG supplied from the oxidant supply unit 31 and the exhaust gas EG supplied from the exhaust combustor 41.
  • the fuel cell stack 10 applied to SOFC operates at a high temperature of about 500 to 1200 ° C. Therefore, during startup and operation, the oxidant gas OG heated to a high temperature is circulated to raise the temperature of the fuel cell stack 10 or maintain the high temperature state of the fuel cell stack 10.
  • the exhaust combustor 41 burns the exhaust gas EG of the anode gas and the exhaust gas EG of the cathode gas discharged from the fuel cell stack 10.
  • the high temperature exhaust gas EG generated by the combustion of the exhaust gas EG is supplied to the heat exchanger 32.
  • the exhaust control valve 42 is configured by a three-way valve that distributes the exhaust gas EG discharged from the exhaust combustor 41 via the heat exchanger 32 to the reformer 24 and the evaporator 23.
  • the distributed exhaust gas EG heats the reformer 24 and the evaporator 23.
  • the exhaust combustor 41 and the exhaust control valve 42 form a “heating unit” that heats the reformer 24. Since the endothermic reaction is dominant in the reaction in the reformer 24 during normal operation, it is necessary to supply heat from the outside. Further, the evaporator 23 needs to supply heat from the outside in order to vaporize the liquid water-containing fuel MW. Therefore, the exhaust combustor 41 and the exhaust control valve 42 increase the respective temperatures by supplying the high temperature exhaust gas EG from the exhaust combustor 41 to the evaporator 23 and the reformer 24.
  • the exhaust control valve 42 is configured so that the ratio of the flow rate of the exhaust gas EG distributed to the main flow passage 32a communicating with the reformer 24 and the bypass flow passage 32b communicating with the evaporator 23 can be adjusted.
  • the exhaust control valve 42 reduces the flow rate of the exhaust gas EG to the bypass flow passage 32b by reducing the opening degree of the valve on the bypass flow passage 32b side and increasing the opening degree of the valve on the main flow passage 32a side. , Increase the flow rate of the exhaust gas EG to the main flow path 32a. In this way, the exhaust control valve 42 controls the operating temperature of the reformer 24 by adjusting the supply amount of the high-temperature exhaust gas EG from the exhaust combustor 41 to the reformer 24.
  • the control unit 50 is a control device that controls the operation of the fuel cell system 100.
  • the control unit 50 includes a storage unit including a ROM and a RAM, an arithmetic unit including a CPU as a main component, and an input / output unit that transmits and receives various data and control commands.
  • FIG. 2 is a flowchart showing the operating procedure of the fuel cell system 100.
  • the fuel cell system 100 detects the state of reforming performance of the catalyst of the reformer 24 that reforms the water-containing fuel MW (steps S101 and S102), and when deterioration of the catalyst of the reformer 24 is detected. Then, the oxidant gas OG is supplied to the reformer 24 to perform the deterioration recovery process (steps S103 to S105). Then, the recovery state of the catalyst of the reformer 24 to which the oxidant gas OG is supplied is detected (step S106), and if the catalyst is in the unrecovered state, the operating condition is changed so as to accelerate the reaction of the reformer 24. Yes (step S107). The details will be described below.
  • control unit 50 acquires the inlet / outlet temperature difference ⁇ T of the reformer 24 from the detection signal of the temperature sensor 25 (step S101).
  • control unit 50 determines whether the inlet / outlet temperature difference ⁇ T of the reformer 24 has become equal to or less than a predetermined threshold T1 based on the detection signal of the temperature sensor 25 (step S102).
  • FIG. 3 is a graph showing temporal changes in the inlet temperature and the outlet temperature during the normal operation of the reformer 24.
  • the degree of progress of each reaction changes and the total reaction heat of each reaction also changes. Specifically, the exothermic reaction becomes dominant and the reaction heat increases, so that the outlet temperature of the reformer 24 rises. Therefore, by detecting the inlet / outlet temperature difference ⁇ T of the reformer 24, a change in the reforming performance of the reformer 24 can be detected.
  • the control unit 50 determines that the reforming performance of the reformer 24 has not deteriorated when the inlet / outlet temperature difference ⁇ T of the reformer 24 exceeds the threshold T1. (Step S102, NO). In this case, the process returns to S101.
  • the control unit 50 determines that the reforming performance of the reformer 24 has deteriorated (step S102, YES).
  • control unit 50 supplies the oxidant gas OG to the reformer 24 to oxidize and remove the carbon deposited on the surface of the catalyst. Is started (step S103).
  • the control unit 50 controls the oxidant gas control valve 43 so as to open the channel 31b side, and supplies the oxidant gas OG upstream of the reformer 24 via the channel 31b (Ste S103).
  • the oxidant gas control valve 43 is open only on the flow path 31a side and closed on the flow path 31b side.
  • a combustion reaction oxidation reaction
  • carbon adhering to the surface of the catalyst is oxidized by oxygen proceeds as in the following formula (8) and is discharged as carbon dioxide.
  • the reformer 24 in addition to the above combustion reaction, a partial oxidation reaction as shown below is started, and hydrogen or carbon monoxide is generated as the reformed gas RG. As a result, the reformed gas RG is supplied to the fuel cell stack 10 even during the deterioration recovery process, so that power generation continues.
  • the combustion reaction of the above formula (8) and the partial oxidation reaction of the above formula (9) are exothermic reactions. Therefore, the exothermic reaction becomes dominant in the reformer 24.
  • control unit 50 determines whether the inlet / outlet temperature difference ⁇ T of the reformer 24 has become equal to or less than a predetermined threshold value T2 based on the detection signal of the temperature sensor 25 (step S106).
  • the control unit 50 recovers the catalyst deterioration by the deterioration recovery process by the supply of the oxidant gas OG in steps S103 to S105, and It is determined that the reforming performance of the quality control device 24 has improved to the extent necessary for normal operation (step S106, NO), and the operation ends. In this case, it is judged that the cause of the performance deterioration of the reformer 24 is the deterioration of the catalyst due to carbon deposition (coking).
  • the control unit 50 indicates that the catalyst is in the unrecovered state even by the deterioration recovery process by the supply of the oxidizing gas OG in steps S103 to S105. It is determined that the reforming performance of the reformer 24 has not improved to the extent necessary for normal operation (step S106, YES). In this case, it is determined that the cause of the performance deterioration of the reformer 24 is due to other factors than the carbon deposition. As described above, the deterioration recovery process can recover the deterioration of the catalyst due to the carbon deposition and can identify the cause of the deterioration of the reforming performance.
  • the control unit 50 determines that the opening degree of the exhaust control valve 42 on the side of the bypass passage 32b is small and the main passage 32a.
  • the opening degree on the side is controlled to be large, and the flow rate of the exhaust gas EG flowing from the exhaust combustor 41 to the bypass passage 32b is reduced (step S107).
  • the inflow amount of the exhaust gas EG supplied from the exhaust combustor 41 to the reformer 24 is increased, and a larger amount of heat is added to the reformer 24 for heating.
  • FIG. 4 is a graph showing the relationship between the reforming performance of the reformer 24 and the operating temperature.
  • the reforming performance of the reformer 24 tends to increase as the operating temperature increases.
  • T N the normal operating temperature
  • the catalyst is activated and the reforming performance of the reformer 24 can be improved to the target reforming performance or higher.
  • Increasing the temperature (T H -T N) is not particularly limited, for example, be a 30 °C ⁇ 60 °C. So long as the temperature increase (T H -T N) is described above, it does not lead to high temperatures to a temperature at which structural change of sintering of the catalytic metal and the catalyst substrate occurs.
  • step S107 if the performance of the reformer 24 is degraded due to some factor, the performance is improved by increasing the operating temperature of the reformer 24, and the inlet / outlet temperature difference ⁇ T is reduced again.
  • the operating temperature of the reformer 24 to be measured may be the inlet temperature, the outlet temperature or the average temperature of the reformer 24.
  • control unit 50 determines whether or not the inlet / outlet temperature difference ⁇ T of the reformer 24 is equal to or larger than a predetermined threshold T3 based on the detection signal of the temperature sensor 25 (step S108).
  • the control unit 50 determines that the reforming performance of the reformer 24 has not been improved to the extent necessary for normal operation (step). S108, NO). In this case, returning to the process of step S107, the control unit 50 repeats the operation of controlling the exhaust control valve 42 to reduce the flow rate of the exhaust gas EG flowing from the exhaust combustor 41 into the bypass passage 32b. After that, the operation of reducing the flow rate of the exhaust gas EG is repeated until the inlet / outlet temperature difference ⁇ T of the reformer 24 becomes equal to or more than the threshold value T3 (step S108, YES). When the flow rate of the exhaust gas EG flowing into the bypass passage 32b becomes 0, the operation is ended without executing step S107.
  • the control unit 50 determines that the reforming performance of the reformer 24 has improved to the extent necessary for normal operation (step S108, YES), The operation ends.
  • FIG. 5 is a graph showing changes with time in the inlet temperature and the outlet temperature of the reformer 24 when the operation procedure of the fuel cell system 100 is executed.
  • the temperature of the reformer 24 rapidly increases during the deterioration recovery process from the supply of the oxidant gas OG in step S103 to the stop of the supply of the oxidant gas OG in step S105. . This is because the combustion reaction (equation (8)) and the partial oxidation reaction (equation (9)) proceed in the reformer 24 and the exothermic reaction becomes dominant.
  • step S105 When the supply of the oxidant gas OG is stopped in step S105, the outlet temperature of the reformer 24 drops. This is because by stopping the supply of the oxidant gas OG, the combustion reaction (equation (8)) and the partial oxidation reaction (equation (9)), which are exothermic reactions, are stopped and the reformer 24 is put into normal operation. Return. This is because the steam reforming reaction (equation (1)) mainly proceeds and the endothermic reaction becomes dominant.
  • step S106 when the inlet / outlet temperature difference ⁇ T of the reformer 24 becomes equal to or less than the predetermined threshold value T2, the control unit 50 reduces the flow rate of the exhaust gas EG flowing from the exhaust combustor 41 into the bypass passage 32b. Then, the reformer 24 is heated. As a result, the catalyst of the reformer 24 is activated and the steam reforming reaction in which the endothermic reaction is dominant proceeds, so that the outlet temperature of the reformer 24 further decreases. As a result, the inlet / outlet temperature difference ⁇ T of the reformer 24 becomes equal to or greater than the predetermined threshold value T3, and the reforming performance of the reformer 24 is improved.
  • the thresholds T1, T2, and T3 of the inlet / outlet temperature difference ⁇ T of the reformer 24 are preset to values that can maintain the reforming performance for supplying the required amount of the reformed gas RG.
  • the magnitude relationship among the threshold values T1, T2, and T3 is T1 ⁇ T3 ⁇ T2. It is preferable to set T1 to the largest value in order to raise the sensitivity of deterioration detection as the most severe condition for the first judgment of deterioration recovery detection in step S102.
  • the threshold value T2 for the determination of the second deterioration recovery detection in step S106 is preferably set to T3> T2 so that the condition is looser than the threshold value T3 for the determination of the third deterioration recovery detection in step S108. This is because, at the time of the third determination in step S108, since the operating temperature of the reformer 24 is increased so as to promote the reaction of the reformer 24 (step S107), the endothermic reaction further progresses. This is because the outlet temperature decreases, and the inlet / outlet temperature difference ⁇ T becomes larger than that at the time of the second determination in step S106.
  • the magnitude relationship between T1, T2, and T3 is not limited to the above as long as it is a temperature at which the reforming performance of the reformer 24 required for normal operation is obtained, and the same value may be used. You may change the size relationship.
  • deterioration recovery means oxidizer supply unit 31 that recovers the deterioration of the catalyst of the reformer 24 by supplying the oxidant gas OG to the reformer 24.
  • a deterioration recovery detecting means temperature sensor 25 for detecting the recovery state of the catalyst by the deterioration recovering means, and a detection signal from the deterioration recovery detecting means indicating that the catalyst is in an unrecovered state.
  • the operating condition changing means (the exhaust combustor 41 and the exhaust control valve 42) for changing the operating condition so as to promote the reaction of 24.
  • the operation method of the fuel cell system 100 is performed by oxidizing the reformer 24 when the catalyst of the reformer 24 that reforms the water-containing fuel MW (corresponding to fuel) is detected.
  • the agent gas OG is supplied, the recovery state of the catalyst of the reformer 24 to which the oxidant gas OG is supplied is detected, and the operating condition is set so as to accelerate the reaction of the reformer 24 when the catalyst is not recovered. change.
  • the fuel cell system 100 when the factor that deteriorates the reforming performance of the reformer 24 is due to carbon deposition, by supplying the oxidant gas OG to the reformer 24, The reforming performance of the reformer 24 can be restored.
  • the cause of the deterioration of the reforming performance of the reformer 24 is other than carbon deposition, it is detected that the catalyst is in an unrecovered state and the operating conditions are changed so as to promote the reaction of the reformer 24.
  • the fuel cell system 100 can continue to operate without stopping.
  • the operating condition changing means has a heating part for heating the reformer 24 based on the detection signal from the deterioration recovery detecting means.
  • the heating unit is composed of the exhaust combustor 41 and the exhaust control valve 42.
  • the deterioration recovery detecting means has a temperature sensor 25 for detecting the recovery state of the catalyst based on the temperature difference ⁇ T between the inlet temperature and the outlet temperature of the reformer 24.
  • a temperature sensor 25 for detecting the difference between the inlet temperature and the outlet temperature of the reformer 24, it is possible to detect the change in the progress of the reaction in the reformer 24, that is, the state of the reforming performance.
  • FIG. 6 is a schematic configuration diagram showing a fuel cell system 200 according to the second embodiment.
  • the fuel cell system 200 according to the second embodiment differs from the first embodiment described above in that it further includes an output sensor 54 that detects the output of the fuel cell stack 10.
  • the output sensor 54 corresponds to "deterioration recovery detection means".
  • the same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.
  • the output sensor 54 detects an electric output P output from the fuel cell stack 10.
  • the output of the fuel cell stack 10 depends on the composition of the reformed gas RG supplied to the fuel cell stack 10.
  • the composition of the reformed gas RG depends on the reforming performance of the reformer 24. Therefore, by detecting the electric output P of the fuel cell stack 10, it is possible to suppress the output reduction of the fuel cell stack 10 due to the deterioration of the composition of the reformed gas RG.
  • FIG. 7 is a flowchart showing the operating procedure of the fuel cell system according to the second embodiment.
  • the state of the reforming performance is determined based on the value of the inlet / outlet temperature difference ⁇ T of the reformer 24.
  • the second embodiment is different in that the state of the reforming performance is judged based on the electric output P of the fuel cell stack 10.
  • the steps other than steps S201, S202, S206, and S208 of the operation procedure of the fuel cell system 200 shown in FIG. 7 are the same as those of the above-described first embodiment shown in FIG. .
  • control unit 50 acquires a detection value indicating the electric output P of the fuel cell stack 10 from the detection signal of the output sensor 54 (step S201).
  • control unit 50 determines whether or not the electric output P is less than or equal to a predetermined threshold P1 based on the detection signal of the output sensor 54 (step S202).
  • the control unit 50 determines that the reforming performance of the reformer 24 has not deteriorated when the electric output P exceeds the predetermined threshold value P1 (step S202, NO). In this case, the process returns to S201.
  • control unit 50 determines that the reforming performance of the reformer 24 has deteriorated when the electric output P is less than or equal to the predetermined threshold P1 (step S202, YES).
  • control unit 50 executes the deterioration recovery process as in the first embodiment described above (steps S103 to S105).
  • control unit 50 determines, based on the detection signal of the output sensor 54, whether or not the electric output P has become equal to or less than a predetermined threshold P2 (step S206).
  • the control unit 50 recovers the deterioration of the catalyst by the deterioration recovery process and improves the reforming performance of the reformer 24 to the extent necessary for normal operation. It is determined that it has been done (step S206, NO), and the operation ends. In this case, it is judged that the cause of the performance deterioration of the reformer 24 is the deterioration of the catalyst due to carbon deposition (coking).
  • the control unit 50 indicates that the catalyst is in an unrecovered state even by the deterioration recovery process, and the reforming performance of the reformer 24 is the degree required for normal operation. It is determined that it has not improved (step S206, YES). In this case, it is determined that the cause of the performance deterioration of the reformer 24 is due to other factors than the carbon deposition.
  • control unit 50 moves from the exhaust combustor 41 to the bypass flow passage 32b, as in the first embodiment described above.
  • the reformer 24 is heated by reducing the flow rate of the inflowing exhaust gas EG (step S107).
  • control unit 50 determines, based on the detection signal of the output sensor 54, whether or not the electric output P has become equal to or higher than a predetermined threshold P3 (step S208).
  • step S208, NO the control unit 50 determines that the reforming performance of the reformer 24 has not improved to the extent necessary for normal operation. In this case, returning to the process of step S107, the control unit 50 repeats the operation of controlling the exhaust control valve 42 to reduce the flow rate of the exhaust gas EG flowing from the exhaust combustor 41 into the bypass passage 32b. After that, the operation of reducing the flow rate of the exhaust gas EG is repeated until the electric output P becomes equal to or larger than the predetermined threshold P3 (step S208, YES). When the flow rate of the exhaust gas EG flowing into the bypass passage 32b becomes 0, the operation is ended without executing step S107.
  • control unit 50 determines that the reforming performance of the reformer 24 has improved to the extent necessary for normal operation (step S208, YES), and ends the operation. .
  • the preset thresholds P1, P2, P3 of the electric output P are P1 ⁇ P3 ⁇ P2.
  • the determination of the first deterioration recovery detection in step S202 is preferably set to the largest value, because the detection sensitivity is raised as the most severe condition. Further, it is preferable that the determination of the second deterioration recovery detection in step S206 is set to P3> P2, which is looser than the determination of the third deterioration recovery detection in step S208. This is for the same reason as in the first embodiment described above. The same values may be used for P1, P2, and P3.
  • the deterioration recovery detection unit of the fuel cell system 200 has the output sensor 54 that detects the recovery state of the catalyst based on the output of the fuel cell stack 10.
  • the output sensor 54 detects the recovery state of the catalyst based on the output of the fuel cell stack 10.
  • FIG. 8 is a schematic configuration diagram showing a fuel cell system 300 according to the third embodiment.
  • the fuel cell system 300 according to the third embodiment is different from the above-described first embodiment in that a heating heater 26 is provided as a “heating unit” for heating the reformer 24.
  • the bypass passage 32b for the exhaust gas EG is not provided, which is also different from the first embodiment described above.
  • the heater 26 corresponds to "operating condition changing means". The same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.
  • the heating heater 26 is composed of an electric heater for heating the reformer 24, a warm air heater, or the like.
  • the heat generation amount of the heater 26 is controlled by the control unit 50.
  • FIG. 9 is a flowchart showing the operating procedure of the fuel cell system 300 according to the third embodiment. Except for step S307 in the operation procedure of the fuel cell system 300 shown in FIG. 9, it is the same as the above-described first embodiment shown in FIG. 2, and therefore the same reference numerals are given and the description thereof is omitted.
  • step S307 the control unit 50 heats the reformer 24 by controlling the heating amount of the heating heater 26 to increase.
  • the reformer 24 can be heated with a simpler configuration as compared with the method of controlling the exhaust control valve 42 to adjust the flow rate of the exhaust gas EG as in the first embodiment described above.
  • the fuel cell system according to the fourth embodiment uses the fuel cell system 100 according to the first embodiment shown in FIG. With reference to FIG. 1, in the fuel cell system according to the fourth embodiment, the flow rate adjusting unit 22 corresponds to “operating condition changing means”.
  • the control unit 50 controls the flow rate adjusting unit 22 to reduce the flow rate of the water-containing fuel MW supplied to the evaporator 23 and reduce the flow rate Q of the mixed gas MG supplied to the reformer 24.
  • the operating conditions are changed so as to accelerate the reaction of the reformer 24.
  • FIG. 10 is a flowchart showing the operating procedure of the fuel cell system according to the fourth embodiment.
  • the steps other than steps S407 to S411 of the operation procedure of the fuel cell system shown in FIG. 10 are the same as those in the above-described first embodiment shown in FIG.
  • FIG. 11 shows the reforming performance and operating temperature of the reformer 24 when the flow rate of the mixed gas MG supplied to the reformer 24 per unit time (hereinafter, referred to as “fuel flow rate Q”) is changed. It is a graph which shows the relationship of.
  • the reforming performance of the catalyst of the reformer 24 tends to decrease as the fuel flow rate Q in the reformer 24 increases. This is because the contact time of the mixed gas MG with the surface of the catalyst is reduced and the reforming reaction is less likely to proceed.
  • the fuel flow rate Q is reduced, the contact time of the mixed gas MG with the surface of the catalyst becomes longer, the reaction of the reformer 24 is promoted, and the reforming performance is improved. Therefore, as shown in FIG. 11, by reducing the fuel flow rate Q, the reforming performance of the reformer 24 is improved to the target reforming performance or higher at the normal operating temperature T N without changing the operating temperature. Can be made.
  • step S407 controls the flow rate adjusting unit 22 to decrease the flow rate Q of the mixed gas MG supplied to the reformer 24 (step S407).
  • the contact time of the mixed gas MG with the surface of the catalyst is increased, the reaction of the reformer 24 is promoted, and the reforming performance of the reformer 24 is improved.
  • control unit 50 determines whether or not the inlet / outlet temperature difference ⁇ T of the reformer 24 has become equal to or greater than a predetermined threshold T4, and the reforming performance of the reformer 24 is adjusted to a level required for normal operation. It is confirmed whether or not it has improved (step S408).
  • the control unit 50 determines whether the fuel flow rate Q is equal to or higher than the minimum flow rate Q1. (Step S409). If the fuel flow rate Q is extremely reduced, the reformed gas RG required for power generation of the fuel cell stack 10 cannot be obtained. Therefore, the “minimum flow rate Q1” is set in advance to a fuel flow rate that can ensure the power generation performance of the fuel cell stack 10.
  • step S407 When the fuel flow rate Q is equal to or higher than the minimum flow rate Q1, the process returns to step S407, and the control unit 50 controls the flow rate adjusting unit 22 to decrease the flow rate Q of the water-containing fuel MW supplied to the reformer 24.
  • the operation to be repeated is repeated (step S407). After that, when the inlet / outlet temperature difference ⁇ T of the reformer 24 is equal to or larger than the threshold value T4, it is determined that the reforming performance of the reformer 24 has improved to the extent necessary for normal operation (YES in step S408), and the operation is performed. To finish.
  • step S410 when the fuel flow rate Q is lower than the minimum flow rate Q1 (step S409, NO), the operating temperature of the reformer 24 is increased (step S410).
  • a method of increasing the operating temperature of the reformer 24 a method of reducing the flow rate of the exhaust gas EG flowing from the exhaust combustor 41 to the bypass passage 32b as in the first embodiment described above may be used.
  • a method of directly heating the reformer 24 using the heater 26 may be used. From the viewpoint of improving the energy efficiency of the fuel cell system, it is preferable to heat the reformer 24 using the heat quantity of the exhaust gas EG by a method of reducing the flow rate of the exhaust gas EG flowing into the bypass flow passage 32b.
  • the control unit 50 determines whether or not the inlet / outlet temperature difference ⁇ T of the reformer 24 is equal to or larger than a predetermined threshold value T5 (step S411).
  • a predetermined threshold value T5 step S411, YES
  • step S411, NO when the inlet / outlet temperature difference ⁇ T of the reformer 24 is less than the predetermined threshold T5 (step S411, NO), the reforming performance of the reformer 24 has not been improved to the extent necessary for normal operation.
  • the control unit 50 repeats the operation of increasing the operating temperature of the reformer 24.
  • the inlet / outlet temperature difference ⁇ T of the reformer 24 becomes equal to or larger than the threshold value T5, it is determined that the reforming performance of the reformer 24 has improved to the extent necessary for normal operation (step S411, YES). , The operation ends.
  • step S407 of decreasing the fuel flow rate Q is preferentially carried out over the operation of increasing the operating temperature of the quality control device 24 (step S410).
  • the operation of raising the operating temperature of the reformer 24 requires energy such as the heat quantity of the exhaust gas EG and the electric energy of the heater, so that the fuel cell system 100 as a whole loses energy. Therefore, from the viewpoint of energy efficiency, the fuel flow rate Q is preferentially reduced so that the reaction of the reformer 24 can be promoted without performing the operation of raising the operating temperature of the reformer 24. There is.
  • the threshold values T1, T2, T4, and T5 of the inlet / outlet temperature difference ⁇ T of the reformer 24 are set in advance to values that maintain the reforming performance capable of supplying the required amount of the reformed gas RG to the fuel cell stack 10. Set it.
  • the magnitude relationship among the thresholds T1, T2, T4, and T5 is T1 ⁇ T5 ⁇ T4 ⁇ T2.
  • T1 is preferably set to the largest value.
  • the condition of the second deterioration recovery detection in step S106 is preferably looser than that of the third deterioration recovery detection in step S408, and T4> T2 is preferably set. This is because, at the time of the third determination in step S408, the fuel flow rate Q is reduced so as to promote the reaction of the reformer 24 (step S407), and therefore the endothermic reaction further progresses and the outlet temperature decreases. However, this is because the inlet / outlet temperature difference ⁇ T becomes larger than that at the time of the second determination in step S106.
  • the threshold value T4 for determining the deterioration recovery detection for the third time in step SS408 is looser than the threshold value T5 for determining the deterioration recovery detection for the fourth time in step S411, and it is preferable to set T5> T4. This is because, at the time of the fourth determination in step S411, the operating temperature of the reformer 24 is raised so as to further promote the reaction of the reformer 24 (step S410), so that the endothermic reaction proceeds further. This is because the outlet temperature decreases, and the inlet / outlet temperature difference ⁇ T becomes larger than that at the time of the third determination in step S408.
  • the operating condition changing means of the fuel cell system based on the detection signal from the deterioration recovery detecting means, the flow rate Q of the mixed gas MG (fuel) supplied to the reformer 24.
  • the flow rate adjusting unit 22 for reducing By reducing the fuel flow rate Q, the contact time of the mixed gas MG with the surface of the catalyst becomes longer, so that the reforming performance of the reformer 24 can be improved.
  • FIG. 12 is a schematic configuration diagram showing a fuel cell system 500 according to the fifth embodiment.
  • FIG. 13 is a flowchart showing the operating procedure of the fuel cell system according to the fifth embodiment.
  • FIG. 14 is a graph showing the relationship between the operating temperature of the reformer 24 and the hydrogen concentration of the reformed gas.
  • the fuel cell system 500 according to the fifth embodiment differs from the first embodiment described above in that the fuel cell system 500 further includes a concentration sensor 27 that detects the hydrogen concentration of the reformed gas RG.
  • the concentration sensor 27 corresponds to “deterioration recovery detection means”. The same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.
  • the concentration sensor 27 is arranged between the reformer 24 and the fuel cell stack 10, that is, downstream of the reformer 24 and upstream of the fuel cell stack 10.
  • the ethanol reforming reaction consists of multiple chemical reactions (see equations (2) to (6)), and the composition of the reformed gas RG is determined based on the reaction rate of each reaction equation.
  • the concentration sensor 27 in this embodiment detects the hydrogen concentration.
  • the component detected by the concentration sensor 27 is not limited to hydrogen as long as it is the gas contained in the reformed gas RG, and may be carbon monoxide or methane, for example. From the viewpoint of improving the sensitivity, it is preferable to select a component whose concentration is likely to change due to deterioration of the reforming performance of the reformer 24.
  • carbon monoxide can be given as an example of a component whose concentration easily fluctuates.
  • FIG. 13 is a flowchart showing the operating procedure of the fuel cell system 500 according to the fifth embodiment.
  • the state of the reforming performance is determined based on the value of the inlet / outlet temperature difference ⁇ T of the reformer 24.
  • the fifth embodiment is different in that the state of the reforming performance is judged based on the hydrogen concentration C H2 in the reformed gas RG.
  • the steps other than steps S501, S502, S506, and S508 in the operation procedure of the fuel cell system shown in FIG. 13 are the same as those in the first embodiment shown in FIG.
  • control unit 50 acquires a detection value indicating the hydrogen concentration C H2 in the reformed gas RG from the detection signal of the concentration sensor 27 (step S501).
  • control unit 50 determines whether the hydrogen concentration C H2 in the reformed gas RG is less than or equal to a predetermined threshold C H2 1 (step S502).
  • the control unit 50 determines that the reforming performance of the reformer 24 has not deteriorated (step S502). , NO). In this case, the process returns to S501.
  • control unit 50 determines that the reforming performance of the reformer 24 has deteriorated (step S502, YES). ).
  • control unit 50 executes the deterioration recovery process as in the first embodiment described above (steps S103 to S105).
  • control unit 50 determines whether or not the hydrogen concentration C H2 in the reformed gas RG has become equal to or lower than a predetermined threshold C H2 2 (step S506).
  • the control unit 50 recovers the deterioration of the catalyst by the deterioration recovery process, and the reforming performance of the reformer 24. Is determined to have improved to the extent necessary for normal operation (step S506, NO), and the operation ends. In this case, it is judged that the cause of the performance deterioration of the reformer 24 is the deterioration of the catalyst due to carbon deposition (coking).
  • the control unit 50 indicates that the catalyst is in a non-recovered state even by the deterioration recovery process, and the reformer 24 is modified. It is determined that the quality performance has not improved to the extent necessary for normal operation (step S506, YES). In this case, it is determined that the cause of the performance deterioration of the reformer 24 is due to other factors than the carbon deposition.
  • control unit 50 moves from the exhaust combustor 41 to the bypass flow passage 32b, as in the first embodiment described above.
  • the reformer 24 is heated by reducing the flow rate of the inflowing exhaust gas EG (step S107).
  • FIG. 14 is a graph showing the relationship between the operating temperature of the reformer 24 and the hydrogen concentration C H2 in the reformed gas RG.
  • the hydrogen concentration C H2 tends to increase as the operating temperature rises.
  • the normal operating temperature T N is raised to the operating temperature T H.
  • the catalyst is activated and the reforming performance of the reformer 24 can be improved to the target reforming performance or higher.
  • the hydrogen concentration C H2 in the reformed gas RG can be increased to the target hydrogen concentration or higher.
  • control unit 50 determines whether the hydrogen concentration C H2 in the reformed gas RG becomes the threshold C H2 3 above a predetermined (step S508).
  • Step S508, NO the control unit 50 repeats the operation of controlling the exhaust control valve 42 to reduce the flow rate of the exhaust gas EG flowing from the exhaust combustor 41 into the bypass passage 32b. After that, the operation of reducing the flow rate of the exhaust gas EG is repeated until the hydrogen concentration C H2 in the reformed gas RG becomes equal to or higher than a predetermined threshold C H23 (step S508, YES).
  • the flow rate of the exhaust gas EG flowing into the bypass passage 32b becomes 0, the operation is ended without executing step S107.
  • control unit 50 determines that the reforming performance of the reformer 24 has been improved to the extent necessary for normal operation (step). S508, YES), and the operation ends.
  • the thresholds C H2 1, C H2 2, and C H2 3 of the hydrogen concentration C H2 in the reformed gas RG set in advance are C H2 1 ⁇ C H2 3 ⁇ C H2 2.
  • the determination of the first deterioration recovery detection in step S502 is set to the largest value for C H2 1 in order to raise the detection sensitivity as the most severe condition.
  • the condition for the second deterioration recovery detection in step S506 is preferably looser than that for the third deterioration recovery detection in step S508, and it is preferable to set C H2 3> C H2 2. This is for the same reason as in the first embodiment described above.
  • the same values may be used for C H2 1, C H2 2, and C H2 3.
  • the deterioration recovery detecting unit of the fuel cell system 500 detects the recovery state of the catalyst based on the composition of the reformed gas RG reformed by the reformer 24. Have. By directly detecting the composition of the reformed gas RG, it is possible to reliably detect the deterioration of the reforming performance of the reformer 24. This can prevent the output of the fuel cell stack 10 from decreasing due to the deterioration of the composition of the reformed gas RG.
  • the deterioration recovery detection means is composed of a temperature sensor for detecting the inlet / outlet temperature difference of the reformer, an output sensor for detecting the output of the fuel cell stack, or a concentration sensor for detecting the composition of the reformed gas.
  • a temperature sensor for detecting the inlet / outlet temperature difference of the reformer for detecting the inlet / outlet temperature difference of the reformer
  • an output sensor for detecting the output of the fuel cell stack or a concentration sensor for detecting the composition of the reformed gas.
  • concentration sensor for detecting the composition of the reformed gas
  • the operation condition changing means has been described with respect to the example in which it is constituted by the heating part for heating the reformer or the flow rate adjusting part for reducing the flow rate of the fuel supplied to the reformer, but the reaction of the reformer is promoted.
  • the operating conditions can be changed as described above, and a configuration other than the above may be used, or a plurality of the above configurations may be appropriately combined and used.
  • the reformer may be further heated by using the heater when the flow rate of the exhaust gas EG flowing into the bypass passage 32b becomes 0.
  • an operation of reducing the fuel flow rate may be performed.
  • the operating condition changing means preferentially performs the operation of reducing the fuel flow rate over the operation of increasing the operating temperature of the reformer, but is not limited to this.
  • the operation to raise the operating temperature of the reformer may be prioritized over the operation to reduce the fuel flow rate, or the operation to reduce the fuel flow rate and the operation to raise the operating temperature of the reformer may be performed at the same time. You may implement.
  • the reformed gas is generated using the water-containing fuel in which the fuel and the water are mixed
  • the fuel tank and the water storage tank may be provided separately.
  • the composition of the mixed gas can be easily adjusted by adjusting the supply amounts from the fuel tank and the water storage tank to the evaporator.
  • the fuel cell stack is described as being applied to a solid oxide fuel cell (SOFC), but the present invention is not limited to this, and for example, a solid polymer membrane fuel cell (PEMFC: Polymer). It may be applied to an Electrolyte Membrane Fuel Cell, a phosphoric acid fuel cell (PAFC: Phosphoric Acid Fuel Cell) or a molten carbonate fuel cell (MCFC: Molten Carbone Fuel Cell).
  • SOFC solid oxide fuel cell
  • PEMFC Solid polymer membrane fuel cell
  • PAFC phosphoric acid fuel cell
  • MCFC Molten Carbone Fuel Cell
  • Fuel cell stack 21 fuel tank, 22 Flow rate adjustment unit, 23 Evaporator, 24 reformer, 25 Temperature sensor (deterioration recovery detection means), 25a inlet temperature sensor, 25b outlet temperature sensor, 26 heater (operating condition changing means), 27 concentration sensor (deterioration recovery detection means), 31 oxidant supply unit (deterioration recovery means), 32 heat exchanger, 32a main flow path, 32b bypass flow path, 41 Exhaust combustor (means for changing operating conditions), 42 Exhaust control valve (operating condition changing means), 43 Oxidant gas control valve, 50 control unit, 54 output sensor (deterioration recovery detection means), 100, 200, 300, 500 Fuel cell system, MW water-containing fuel (fuel), MG mixed gas, RG reformed gas, OG oxidant gas, EG Exhaust gas.
  • Fuel cell system MW water-containing fuel (fuel), MG mixed gas, RG reformed gas, OG oxidant gas, EG Exhaust gas.

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Abstract

A fuel cell system capable of dealing with factors responsible for degradation in reforming performance of reformers of various kinds and a method for operating the fuel cell system are provided. The fuel cell system generates electric power by supplying reformed fuel from a catalyst-equipped reformer to a fuel cell stack. The fuel cell system has: a degradation recovery means for recovering a degraded catalyst of a reformer by supplying an oxidant gas to the reformer; a degradation recovery detection means for detecting a recovery state of the catalyst recovered by the degradation recovery means; and an operating condition change means for changing operating conditions so as to promote reaction of the reformer on the basis of a detection signal from the degradation recovery detection means indicating that the catalyst is in a non-recovered state.

Description

燃料電池システムおよび燃料電池システムの運転方法Fuel cell system and method of operating fuel cell system
　本発明は、燃料電池システムおよび燃料電池システムの運転方法に関する。 The present invention relates to a fuel cell system and a method of operating the fuel cell system.
　改質器の改質性能は、様々な要因で低下する可能性がある。改質器の改質性能が低下する要因の一つとして、炭素析出による触媒の劣化が挙げられる。例えば、下記特許文献１には、炭素析出に対する対策として、改質器に酸化剤を投入し、析出した炭素を酸化させて除去する燃料電池システムが開示されている。 The reforming performance of the reformer may be reduced due to various factors. One of the factors that lower the reforming performance of the reformer is deterioration of the catalyst due to carbon deposition. For example, Patent Document 1 below discloses a fuel cell system in which an oxidizing agent is introduced into a reformer to oxidize and remove deposited carbon as a measure against carbon deposition.
特許第４１９２５１８号明細書Patent No. 4192518
　しかしながら、上記特許文献１に開示されている燃料電池システムは、炭素析出のみに特化した対策であり、他に改質性能の低下要因がある場合は対応できない。 However, the fuel cell system disclosed in Patent Document 1 above is a measure specialized only for carbon deposition, and cannot be dealt with when there are other factors that reduce the reforming performance.
　本発明の目的は、様々な改質器の改質性能の低下要因に対応できる燃料電池システムおよび燃料電池システムの運転方法を提供することである。 An object of the present invention is to provide a fuel cell system and a method of operating the fuel cell system, which can cope with various factors that deteriorate the reforming performance of the reformer.
　上記目的を達成するための本発明の燃料電池システムは、燃料を触媒を備えた改質器で改質して燃料電池スタックに供給して発電する燃料電池システムである。該燃料電池システムは、前記改質器に酸化剤ガスを供給して前記改質器の触媒の劣化を回復する劣化回復手段と、前記劣化回復手段による前記触媒の回復状態を検出する劣化回復検出手段と、前記触媒が未回復状態であることを示す前記劣化回復検出手段からの検出信号に基づいて、前記改質器の反応を促進するように運転条件を変更する運転条件変更手段と、を有する。 The fuel cell system of the present invention for achieving the above object is a fuel cell system that reforms fuel with a reformer equipped with a catalyst and supplies the reformed fuel to a fuel cell stack to generate electricity. The fuel cell system includes a deterioration recovery means for supplying an oxidant gas to the reformer to recover deterioration of the catalyst of the reformer, and a deterioration recovery detection for detecting a recovery state of the catalyst by the deterioration recovery means. Means and operating condition changing means for changing the operating condition so as to promote the reaction of the reformer, based on a detection signal from the deterioration recovery detecting means indicating that the catalyst is in an unrecovered state. Have.
　上記目的を達成するための本発明の燃料電池システムの運転方法は、燃料を改質する改質器の触媒の劣化が検出された場合に、前記改質器に酸化剤ガスを供給し、前記酸化剤が供給された前記改質器の前記触媒の回復状態を検出し、前記触媒が未回復状態の場合は前記改質器の反応を促進するように運転条件を変更する。 A method of operating a fuel cell system of the present invention to achieve the above object, when deterioration of a catalyst of a reformer for reforming fuel is detected, supplying an oxidant gas to the reformer, The recovery state of the catalyst of the reformer supplied with the oxidant is detected, and when the catalyst is in the non-recovery state, the operating condition is changed so as to accelerate the reaction of the reformer.
第１実施形態に係る燃料電池システムを示す概略構成図である。It is a schematic block diagram which shows the fuel cell system which concerns on 1st Embodiment. 第１実施形態に係る燃料電池システムの運転手順を示すフローチャートである。It is a flow chart which shows the operating procedure of the fuel cell system concerning a 1st embodiment. 改質器の通常運転時における入口温度と出口温度の時間変化を示すグラフである。It is a graph which shows the time change of the inlet temperature and the outlet temperature at the time of normal operation of a reformer. 改質器の改質性能と運転温度との関係を示すグラフである。It is a graph which shows the relationship between the reforming performance of a reformer, and operating temperature. 第１実施形態に係る燃料電池システムの運転手順を実行した場合の改質器の入口温度と出口温度の時間変化を示すグラフである。It is a graph which shows the time change of the inlet temperature and outlet temperature of a reformer at the time of performing the operating procedure of the fuel cell system which concerns on 1st Embodiment. 第２実施形態に係る燃料電池システムを示す概略構成図である。It is a schematic block diagram which shows the fuel cell system which concerns on 2nd Embodiment. 第２実施形態に係る燃料電池システムの運転手順を示すフローチャートである。It is a flow chart which shows the operating procedure of the fuel cell system concerning a 2nd embodiment. 第３実施形態に係る燃料電池システムを示す概略構成図である。It is a schematic block diagram which shows the fuel cell system which concerns on 3rd Embodiment. 第３実施形態に係る燃料電池システムの運転手順を示すフローチャートである。It is a flow chart which shows the operating procedure of the fuel cell system concerning a 3rd embodiment. 第４実施形態に係る燃料電池システムの運転手順を示すフローチャートである。It is a flow chart which shows the operating procedure of the fuel cell system concerning a 4th embodiment. 燃料流量を変えた場合の改質器の改質性能と運転温度との関係を示すグラフである。6 is a graph showing the relationship between the reforming performance of the reformer and the operating temperature when the fuel flow rate is changed. 第５実施形態に係る燃料電池システムを示す概略構成図である。It is a schematic block diagram which shows the fuel cell system which concerns on 5th Embodiment. 第５実施形態に係る燃料電池システムの運転手順を示すフローチャートである。It is a flow chart which shows the operating procedure of the fuel cell system concerning a 5th embodiment. 改質ガス中の水素濃度と改質器の運転温度との関係を示すグラフである。It is a graph which shows the relationship between the hydrogen concentration in reformed gas, and the operating temperature of a reformer.
　以下、添付した図面を参照しながら、本発明の実施形態を説明する。なお、以下の説明は特許請求の範囲に記載される技術的範囲や用語の意義を限定するものではない。また、図面の寸法比率は説明の都合上誇張されており、実際の比率とは異なる場合がある。 Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following description does not limit the technical scope or the meaning of terms used in the claims. Further, the dimensional ratios in the drawings are exaggerated for convenience of description, and may differ from the actual ratios.
　＜第１実施形態＞
　図１は、第１実施形態に係る燃料電池システムを示す概略構成図である。図１を参照して、本発明の実施形態に係る燃料電池システム１００について説明する。 <First Embodiment>
FIG. 1 is a schematic configuration diagram showing the fuel cell system according to the first embodiment. A fuel cell system 100 according to an embodiment of the present invention will be described with reference to FIG.
　（燃料電池システム１００）
　図１に示される燃料電池システム１００は、燃料を改質して改質ガスＲＧを生成し、改質ガスＲＧおよび酸化剤ガスＯＧを燃料電池スタック１０に供給して発電する。改質ガスＲＧは、燃料電池スタック１０のアノード電極へ供給されるアノードガスである。酸化剤ガスＯＧは、燃料電池スタック１０のカソード電極へ供給されるカソードガスである。酸化剤ガスＯＧは、酸素、あるいは酸素を含有する空気などから構成される。 (Fuel cell system 100)
The fuel cell system 100 shown in FIG. 1 reforms a fuel to generate a reformed gas RG, and supplies the reformed gas RG and the oxidant gas OG to the fuel cell stack 10 to generate electric power. The reformed gas RG is an anode gas supplied to the anode electrode of the fuel cell stack 10. The oxidant gas OG is a cathode gas supplied to the cathode electrode of the fuel cell stack 10. The oxidant gas OG is composed of oxygen, air containing oxygen, or the like.
　本実施形態の燃料電池スタック１０は、自動車に搭載される固体酸化物形燃料電池（ＳＯＦＣ：Ｓｏｌｉｄ　Ｏｘｉｄｅ　Ｆｕｅｌ　Ｃｅｌｌ）に適用される。ＳＯＦＣは、アノードガスとして水素だけでなく一酸化炭素やメタンも使用することができるため、燃料電池システム１００の発電効率を向上させることができる。 The fuel cell stack 10 of the present embodiment is applied to a solid oxide fuel cell (SOFC: Solid Oxide Fuel Cell) mounted on an automobile. Since SOFC can use not only hydrogen but also carbon monoxide and methane as an anode gas, the power generation efficiency of the fuel cell system 100 can be improved.
　燃料は、改質することでアノードガスとして燃料電池スタック１０の発電に利用可能な燃料であれば特に限定されない。燃料としては、例えば、メタン（ＣＨ４）、エタン（Ｃ２Ｈ６）、プロパン（Ｃ３Ｈ８）、ブタン（Ｃ４Ｈ１０）、ガソリン、ナフサ、灯油、軽油、天然ガス、ＬＰＧ、都市ガス、メタノール（ＣＨ３ＯＨ）、エタノール（Ｃ２Ｈ５ＯＨ）、ＤＭＥ（ＣＨ３ＯＣＨ３）、アセトン（ＣＨ３Ｃ（＝Ｏ）ＣＨ３）、バイオ燃料等が挙げられる。本実施形態では、燃料として酸素含有炭化水素燃料であるエタノールを使用した場合を例に挙げて説明する。また、本実施形態では、燃料および水を混合した液体の水含有燃料ＭＷを用いて改質ガスＲＧを生成する場合を例に挙げて説明する。 The fuel is not particularly limited as long as it can be used as the anode gas by reforming to be used for power generation of the fuel cell stack 10. Examples of the fuel include methane (CH 4 ), ethane (C 2 H 6 ), propane (C 3 H 8 ), butane (C 4 H 10 ), gasoline, naphtha, kerosene, light oil, natural gas, LPG, and city. gas, methanol (CH 3 OH), ethanol (C 2 H 5 OH), DME (CH 3 OCH 3), acetone (CH 3 C (= O) CH 3), biofuel and the like. In the present embodiment, a case where ethanol, which is an oxygen-containing hydrocarbon fuel, is used as a fuel will be described as an example. Further, in the present embodiment, a case where the reformed gas RG is generated using the liquid water-containing fuel MW in which the fuel and water are mixed will be described as an example.
　燃料電池システム１００は、触媒を備えた改質器２４と、改質器２４に酸化剤ガスＯＧを供給して改質器２４の触媒の劣化を回復する劣化回復手段と、劣化回復手段による触媒の回復状態を検出する劣化回復検出手段と、触媒が未回復状態であることを示す劣化回復検出手段からの検出信号に基づいて、改質器２４の反応を促進するように運転条件を変更する運転条件変更手段と、を有する。 The fuel cell system 100 includes a reformer 24 including a catalyst, a deterioration recovery unit that supplies an oxidant gas OG to the reformer 24 to recover the deterioration of the catalyst of the reformer 24, and a catalyst using the deterioration recovery unit. Of the deterioration recovery detection means for detecting the recovery state of the catalyst and the detection signal from the deterioration recovery detection means indicating that the catalyst is in the unrecovered state, the operating conditions are changed so as to accelerate the reaction of the reformer 24. Operating condition changing means.
　具体的には、図１を参照して、燃料電池システム１００は、水含有燃料ＭＷを貯蔵する燃料タンク２１と、水含有燃料ＭＷを蒸発させる蒸発器２３と、水含有燃料ＭＷを改質して改質ガスＲＧを生成する改質器２４と、酸化剤ガスＯＧを供給する酸化剤供給部３１と、熱交換器３２と、燃料電池スタック１０の排気ガスＥＧを燃焼する排気燃焼器４１と、制御部５０とを有する。 Specifically, referring to FIG. 1, the fuel cell system 100 includes a fuel tank 21 that stores a water-containing fuel MW, an evaporator 23 that evaporates the water-containing fuel MW, and a water-containing fuel MW. Reformer 24 for generating reformed gas RG, oxidant supply unit 31 for supplying oxidant gas OG, heat exchanger 32, and exhaust combustor 41 for burning exhaust gas EG of fuel cell stack 10. , And a control unit 50.
　燃料タンク２１と蒸発器２３との間には、水含有燃料ＭＷの供給量を調整する流量調整部２２が配置されている。なお、本明細書中、燃料電池システム１００の説明において「ＡとＢとの間」とは、「ＡからＢへ流体を流すための流路の途中」を意味する。 A flow rate adjusting unit 22 that adjusts the supply amount of the water-containing fuel MW is arranged between the fuel tank 21 and the evaporator 23. In the description of the fuel cell system 100 in the present specification, “between A and B” means “in the middle of the flow path for flowing the fluid from A to B”.
　改質器２４には、改質器２４の入口温度と出口温度を検知する温度センサ２５が取り付けられている。 A temperature sensor 25 that detects the inlet temperature and the outlet temperature of the reformer 24 is attached to the reformer 24.
　燃料タンク２１の水含有燃料ＭＷは、流量調整部２２によって蒸発器２３へ供給され、気化されて水蒸気および燃料ガスを含む混合ガスＭＧとなる。混合ガスＭＧは、改質器２４に供給される。改質器２４は、水蒸気改質によって混合ガスＭＧから水素リッチな改質ガスＲＧを生成する。改質ガスＲＧは、アノードガスとして燃料電池スタック１０に供給される。 The water-containing fuel MW in the fuel tank 21 is supplied to the evaporator 23 by the flow rate adjusting unit 22 and is vaporized into a mixed gas MG containing water vapor and fuel gas. The mixed gas MG is supplied to the reformer 24. The reformer 24 produces hydrogen-rich reformed gas RG from the mixed gas MG by steam reforming. The reformed gas RG is supplied to the fuel cell stack 10 as an anode gas.
　酸化剤供給部３１から供給された酸化剤ガスＯＧは、酸化剤ガス制御弁４３によって２つの流路３１ａ、３１ｂに分岐して流される。流路３１ａを通る酸化剤ガスＯＧは、熱交換器３２へ供給され、熱交換器３２において加熱された後、カソードガスとして燃料電池スタック１０に供給される。流路３１ｂを通る酸化剤ガスＯＧは、改質器２４の上流に供給される。 The oxidant gas OG supplied from the oxidant supply unit 31 is branched by the oxidant gas control valve 43 into the two flow paths 31a and 31b. The oxidant gas OG passing through the flow path 31a is supplied to the heat exchanger 32, heated in the heat exchanger 32, and then supplied to the fuel cell stack 10 as cathode gas. The oxidant gas OG passing through the flow path 31b is supplied upstream of the reformer 24.
　燃料電池スタック１０から排出されたアノードガスの排気ガスおよびカソードガスの排気ガスはそれぞれ排気燃焼器４１に供給される。排気燃焼器４１において燃焼された排気ガスＥＧは、熱交換器３２を通った後、改質器２４へ流れるメイン流路３２ａおよび蒸発器２３へ流れるバイパス流路３２ｂの２つの流路３２ａ、３２ｂに分岐して流される。 The exhaust gas of the anode gas and the exhaust gas of the cathode gas discharged from the fuel cell stack 10 are respectively supplied to the exhaust combustor 41. The exhaust gas EG burned in the exhaust combustor 41, after passing through the heat exchanger 32, has two flow passages 32a and 32b: a main flow passage 32a flowing to the reformer 24 and a bypass flow passage 32b flowing to the evaporator 23. Is diverted to and shed.
　２つの流路３２ａ、３２ｂの分岐点には、改質器２４および蒸発器２３への排気ガスＥＧの分配量を調整する排気制御弁４２が配置されている。メイン流路３２ａを通る排気ガスＥＧは、改質器２４および蒸発器２３において混合ガスＭＧと順に熱交換した後、蒸発器２３から燃料電池システム１００の外部に排出される。バイパス流路３２ｂを通る排気ガスＥＧは、蒸発器２３において混合ガスＭＧと熱交換した後、蒸発器２３から燃料電池システム１００の外部に排出される。排気ガスＥＧの熱量を蒸発器２３や改質器２４の加熱に利用することによって、燃料電池システム１００のエネルギー効率を向上させることができる。 An exhaust control valve 42 that adjusts the distribution amount of the exhaust gas EG to the reformer 24 and the evaporator 23 is arranged at the branch point of the two flow paths 32a and 32b. The exhaust gas EG passing through the main flow path 32a is heat-exchanged with the mixed gas MG in the reformer 24 and the evaporator 23 in order, and then discharged from the evaporator 23 to the outside of the fuel cell system 100. The exhaust gas EG passing through the bypass flow path 32b exchanges heat with the mixed gas MG in the evaporator 23, and then is discharged from the evaporator 23 to the outside of the fuel cell system 100. By utilizing the heat quantity of the exhaust gas EG for heating the evaporator 23 and the reformer 24, the energy efficiency of the fuel cell system 100 can be improved.
　本実施形態において、酸化剤供給部３１は、改質器２４に酸化剤ガスＯＧを供給して改質器２４の触媒の劣化を回復する「劣化回復手段」に相当する。また、温度センサ２５は、劣化回復手段による触媒の回復状態を検出する「劣化回復検出手段」に相当する。また、排気燃焼器４１および排気制御弁４２は、改質器２４の反応を促進するように運転条件を変更する「運転条件変更手段」に相当する。 In the present embodiment, the oxidant supply unit 31 corresponds to “deterioration recovery means” that supplies the oxidant gas OG to the reformer 24 to recover the deterioration of the catalyst of the reformer 24. The temperature sensor 25 corresponds to "deterioration recovery detection means" for detecting the recovery state of the catalyst by the deterioration recovery means. The exhaust combustor 41 and the exhaust control valve 42 correspond to “operating condition changing means” that changes the operating conditions so as to promote the reaction of the reformer 24.
　以下、図１を参照して、燃料電池システム１００の各部の構成について詳細に説明する。 The configuration of each part of the fuel cell system 100 will be described in detail below with reference to FIG.
　燃料タンク２１は、燃料および水を混合した水含有燃料ＭＷを貯蔵する。燃料および水を混合して貯蔵することによって、燃料を貯蔵するための燃料用タンクと、水を貯蔵するための貯水用タンクとをそれぞれ個別に設ける必要がない。これにより、燃料電池システム１００の構成を簡素化および小型化することができる。なお、燃料タンク２１には、水含有燃料ＭＷ中の燃料と水の組成を検出する濃度センサを設けてもよい。 The fuel tank 21 stores a water-containing fuel MW that is a mixture of fuel and water. By mixing and storing fuel and water, it is not necessary to separately provide a fuel tank for storing fuel and a water storage tank for storing water. Thereby, the configuration of the fuel cell system 100 can be simplified and downsized. The fuel tank 21 may be provided with a concentration sensor that detects the composition of the fuel and water in the water-containing fuel MW.
　流量調整部２２は、燃料タンク２１に貯蔵された水含有燃料ＭＷを取り出して、供給量を調整しながら蒸発器２３に供給する電動ポンプから構成される。流量調整部２２は、制御部５０からの制御信号に基づいて、蒸発器２３への水含有燃料ＭＷの供給量を調整可能に構成されている。 The flow rate adjusting unit 22 is composed of an electric pump that takes out the water-containing fuel MW stored in the fuel tank 21 and supplies it to the evaporator 23 while adjusting the supply amount. The flow rate adjusting unit 22 is configured to be able to adjust the supply amount of the water-containing fuel MW to the evaporator 23 based on the control signal from the control unit 50.
　蒸発器２３は、流量調整部２２から供給された水含有燃料ＭＷを気化して水蒸気および燃料を含む混合ガスＭＧを生成する。蒸発器２３は、排気燃焼器４１からの排気ガスＥＧによって加熱される。蒸発器２３に流入する排気ガスＥＧは、燃料電池システム１００の外部に排出される。上述したように、蒸発器２３に供給される排気ガスＥＧは、メイン流路３２ａを通って改質器２４を経て蒸発器２３に供給される排気ガスＥＧと、バイパス流路３２ｂを通って蒸発器２３に直接的に供給される排気ガスＥＧとのうち、少なくとも一方の排気ガスＥＧにより構成されている。なお、蒸発器２３は、例えば、電気ヒータ等の加熱装置を用いて加熱してもよい。 The evaporator 23 vaporizes the water-containing fuel MW supplied from the flow rate adjusting unit 22 to generate a mixed gas MG containing water vapor and fuel. The evaporator 23 is heated by the exhaust gas EG from the exhaust combustor 41. The exhaust gas EG flowing into the evaporator 23 is discharged to the outside of the fuel cell system 100. As described above, the exhaust gas EG supplied to the evaporator 23 passes through the main passage 32a, the reformer 24 and the exhaust gas EG supplied to the evaporator 23, and the exhaust gas EG passes through the bypass passage 32b. Of the exhaust gas EG directly supplied to the container 23, at least one of the exhaust gas EG is configured. The evaporator 23 may be heated by using a heating device such as an electric heater.
　改質器２４は、改質反応を促進する触媒を有する。改質器２４は、蒸発器２３から供給される混合ガスＭＧを改質して、燃料電池スタック１０に供給される改質ガスＲＧを生成する。改質器２４においては混合ガスＭＧ中の燃料ガスおよび水蒸気が触媒反応を起して水蒸気改質によって改質ガスＲＧが生成される。 The reformer 24 has a catalyst that accelerates the reforming reaction. The reformer 24 reforms the mixed gas MG supplied from the evaporator 23 to generate the reformed gas RG supplied to the fuel cell stack 10. In the reformer 24, the fuel gas and steam in the mixed gas MG cause a catalytic reaction to generate reformed gas RG by steam reforming.
　本実施形態の改質器２４は、燃料であるエタノールを水蒸気改質することにより、燃料電池スタック１０のアノードガスである水素（Ｈ２）、一酸化炭素（ＣＯ）およびメタン（ＣＨ４）を生成する。 The reformer 24 of the present embodiment steam-reforms ethanol, which is a fuel, to produce hydrogen (H 2 ), carbon monoxide (CO), and methane (CH 4 ) that are anode gases of the fuel cell stack 10. To generate.
　改質器２４では、エタノール（Ｃ２Ｈ５ＯＨ）および水蒸気（Ｈ２Ｏ）の混合ガスＭＧを改質して水素（Ｈ２）、一酸化炭素（ＣＯ）およびメタン（ＣＨ４）を含む改質ガスＲＧを生成する水蒸気改質反応が生じる。本明細書では、改質器２４を主に水蒸気改質反応によって運転させることを「通常運転」と称する。通常運転時の改質器２４の作動温度は、燃料の構成材料や触媒の種類にもよるが、約５５０℃～６００℃である。 The reformer 24 reforms the mixed gas MG of ethanol (C 2 H 5 OH) and steam (H 2 O) to contain hydrogen (H 2 ), carbon monoxide (CO) and methane (CH 4 ). A steam reforming reaction that produces the reformed gas RG occurs. In the present specification, operating the reformer 24 mainly by a steam reforming reaction is referred to as "normal operation". The operating temperature of the reformer 24 during normal operation is about 550 ° C. to 600 ° C., although it depends on the constituent material of the fuel and the type of catalyst.
Figure JPOXMLDOC01-appb-C000001
Figure JPOXMLDOC01-appb-C000001
　ここで、上記水蒸気改質反応は、下記の複数の反応が進行することによる全体反応として示される。 ▽ Here, the steam reforming reaction is shown as an overall reaction by the progress of the following multiple reactions.
Figure JPOXMLDOC01-appb-C000002
Figure JPOXMLDOC01-appb-C000002
　上述の式（３）および式（５）の化学反応は発熱反応であるのに対して式（２）、式（４）、式（６）および式（７）の化学反応は吸熱反応である。このように改質器２４では、発熱反応よりも吸熱反応が多く、全体としても吸熱反応が支配的である。 The chemical reactions of the above formulas (3) and (5) are exothermic reactions, whereas the chemical reactions of the formulas (2), (4), (6) and (7) are endothermic reactions. . As described above, in the reformer 24, the endothermic reaction is larger than the exothermic reaction, and the endothermic reaction is dominant as a whole.
　改質器２４の改質性能は、様々な要因で低下する場合がある。ここで、「改質器２４の改質性能の低下」とは、改質反応が進行しにくくなり、改質反応の選択率や燃料の転化率等が低下することを意味する。なお、改質反応の選択率とは、改質器２４の全体の反応中で燃料電池スタック１０の発電に使用される水素等の改質ガスＲＧを生成する反応経路を選択する割合を意味する。 The reforming performance of the reformer 24 may decrease due to various factors. Here, "reduction of the reforming performance of the reformer 24" means that the reforming reaction is less likely to proceed and the selectivity of the reforming reaction, the conversion rate of fuel, and the like are reduced. Note that the selectivity of the reforming reaction means the rate of selecting a reaction path that produces a reformed gas RG such as hydrogen used for power generation of the fuel cell stack 10 in the entire reaction of the reformer 24. .
　改質器２４の改質性能が低下する要因としては、触媒の劣化、水含有燃料ＭＷの組成変化、運転温度（改質温度）が低い、燃料（本実施形態では混合ガスＭＧ）と触媒との接触時間が短い等が挙げられる。水含有燃料ＭＷの組成は、燃料と水の揮発性の違い等により経時的に変化する可能性がある。水含有燃料ＭＷの組成が最適値から変化すると、燃料が供給不足になったり、その逆に過剰供給されたりして、水蒸気改質反応が進行しにくくなる。また、改質器２４の改質性能は、運転温度が高く、燃料と触媒との接触時間が長いほど向上する傾向にある。 Factors that deteriorate the reforming performance of the reformer 24 include deterioration of the catalyst, composition change of the water-containing fuel MW, low operating temperature (reforming temperature), fuel (mixed gas MG in this embodiment) and catalyst. The contact time is short. The composition of the water-containing fuel MW may change over time due to differences in the volatility of the fuel and water. When the composition of the water-containing fuel MW changes from the optimum value, the fuel becomes insufficiently supplied or, conversely, excessively supplied, so that the steam reforming reaction becomes difficult to proceed. Further, the reforming performance of the reformer 24 tends to improve as the operating temperature is higher and the contact time between the fuel and the catalyst is longer.
　触媒の劣化としては、触媒の有効比表面積の低下、触媒基材の構造変化等が挙げられる。触媒の有効比表面積が低下する要因としては、炭素析出や触媒金属のシンタリング等が挙げられる。触媒の表面に炭素が析出すると、炭素で被覆された部分では触媒反応が起きにくくなるため、有効比表面積が低下する。また、触媒金属がシンタリングを起こすと、幾何学的に有効比表面積が低下する。また、触媒基材の構造が変化すると、水含有燃料ＭＷの流れが塞がれて触媒の有効表面まで水含有燃料ＭＷが到達できない場合がある。 The deterioration of the catalyst includes the reduction of the effective specific surface area of the catalyst and the structural change of the catalyst base material. Factors that reduce the effective specific surface area of the catalyst include carbon deposition and sintering of the catalyst metal. When carbon is deposited on the surface of the catalyst, the catalytic reaction is less likely to occur in the portion coated with carbon, and the effective specific surface area is reduced. Further, when the catalytic metal causes sintering, the effective specific surface area is geometrically reduced. Further, when the structure of the catalyst base material changes, the flow of the water-containing fuel MW may be blocked and the water-containing fuel MW may not reach the effective surface of the catalyst.
　なお、触媒の劣化の要因となる触媒金属のシンタリングや触媒基材の構造変化は、非常に高温（例えば、８５０℃）で生じるため、改質器２４の通常運転の作動温度（本実施形態では約５５０℃～６００℃）では生じにくい。しかしながら、例えば、異常発生時に一時的に触媒が高温環境下に置かれた場合に触媒金属のシンタリングや触媒基材の構造変化が生じる可能性もある。そのため、本実施形態の燃料電池システム１００は、触媒の劣化要因として炭素析出だけでなく触媒金属のシンタリングや触媒基材の構造変化にも対応できるように構成している。 Since the sintering of the catalytic metal and the structural change of the catalytic base material that cause the deterioration of the catalyst occur at an extremely high temperature (for example, 850 ° C.), the operating temperature of the normal operation of the reformer 24 (the present embodiment). Is less likely to occur at about 550 ° C to 600 ° C. However, for example, when the catalyst is temporarily placed in a high temperature environment when an abnormality occurs, the sintering of the catalyst metal and the structural change of the catalyst base material may occur. Therefore, the fuel cell system 100 of the present embodiment is configured so as to cope with not only carbon deposition but also sintering of the catalyst metal and structural change of the catalyst base material as the catalyst deterioration factor.
　温度センサ２５は、混合ガスＭＧが流入する改質器２４の入口温度を測定する入口温度センサ２５ａと、混合ガスＭＧが流出する改質器２４の出口温度を測定する出口温度センサ２５ｂとを有する。入口温度センサ２５ａは、改質器２４に供給される混合ガスＭＧの温度を検出し、検出した値を制御部５０に出力する。出口温度センサ２５ｂは、改質器２４から排出される改質ガスＲＧの温度を検出し、検出した値を制御部５０に出力する。なお、入口温度センサ２５ａおよび出口温度センサ２５ｂは一体として構成されるものであってもよい。 The temperature sensor 25 has an inlet temperature sensor 25a for measuring the inlet temperature of the reformer 24 into which the mixed gas MG flows, and an outlet temperature sensor 25b for measuring the outlet temperature of the reformer 24 from which the mixed gas MG flows out. . The inlet temperature sensor 25a detects the temperature of the mixed gas MG supplied to the reformer 24 and outputs the detected value to the control unit 50. The outlet temperature sensor 25b detects the temperature of the reformed gas RG discharged from the reformer 24 and outputs the detected value to the control unit 50. The inlet temperature sensor 25a and the outlet temperature sensor 25b may be integrally configured.
　酸化剤供給部３１は、酸素または空気からなる酸化剤ガスＯＧを供給する。本実施形態の酸化剤供給部３１は、空気を外部から吸引して燃料電池スタック１０または改質器２４に供給するブロワーから構成される。 The oxidant supply unit 31 supplies an oxidant gas OG composed of oxygen or air. The oxidant supply unit 31 of the present embodiment is composed of a blower that sucks air from the outside and supplies the air to the fuel cell stack 10 or the reformer 24.
　熱交換器３２は、酸化剤供給部３１から供給される酸化剤ガスＯＧと排気燃焼器４１から供給される排気ガスＥＧとの間で熱交換して、酸化剤ガスＯＧを加熱する。ＳＯＦＣに適用される燃料電池スタック１０は、約５００～１２００℃の高温で作動する。このため、起動時および運転時には、高温に加熱された酸化剤ガスＯＧを流通させて燃料電池スタック１０を昇温し、あるいは燃料電池スタック１０の高温状態を維持する。 The heat exchanger 32 heats the oxidant gas OG by exchanging heat between the oxidant gas OG supplied from the oxidant supply unit 31 and the exhaust gas EG supplied from the exhaust combustor 41. The fuel cell stack 10 applied to SOFC operates at a high temperature of about 500 to 1200 ° C. Therefore, during startup and operation, the oxidant gas OG heated to a high temperature is circulated to raise the temperature of the fuel cell stack 10 or maintain the high temperature state of the fuel cell stack 10.
　排気燃焼器４１は、燃料電池スタック１０から排出されたアノードガスの排気ガスＥＧおよびカソードガスの排気ガスＥＧを燃焼する。排気ガスＥＧの燃焼によって生成される高温の排気ガスＥＧが熱交換器３２に供給される。 The exhaust combustor 41 burns the exhaust gas EG of the anode gas and the exhaust gas EG of the cathode gas discharged from the fuel cell stack 10. The high temperature exhaust gas EG generated by the combustion of the exhaust gas EG is supplied to the heat exchanger 32.
　排気制御弁４２は、熱交換器３２を介して排気燃焼器４１から排出される排気ガスＥＧを改質器２４および蒸発器２３へ分配する三方弁によって構成される。分配された排気ガスＥＧは、改質器２４および蒸発器２３を加熱する。 The exhaust control valve 42 is configured by a three-way valve that distributes the exhaust gas EG discharged from the exhaust combustor 41 via the heat exchanger 32 to the reformer 24 and the evaporator 23. The distributed exhaust gas EG heats the reformer 24 and the evaporator 23.
　以上のように、排気燃焼器４１および排気制御弁４２は、改質器２４を加熱する「加熱部」を構成する。通常運転時の改質器２４での反応は吸熱反応が支配的であるため、外部から熱を供給する必要がある。また、蒸発器２３は、液体の水含有燃料ＭＷを気化するために外部から熱を供給する必要がある。そこで、排気燃焼器４１および排気制御弁４２は、排気燃焼器４１からの高温の排気ガスＥＧを蒸発器２３および改質器２４に供給することによって、それぞれの温度を高温にしている。 As described above, the exhaust combustor 41 and the exhaust control valve 42 form a “heating unit” that heats the reformer 24. Since the endothermic reaction is dominant in the reaction in the reformer 24 during normal operation, it is necessary to supply heat from the outside. Further, the evaporator 23 needs to supply heat from the outside in order to vaporize the liquid water-containing fuel MW. Therefore, the exhaust combustor 41 and the exhaust control valve 42 increase the respective temperatures by supplying the high temperature exhaust gas EG from the exhaust combustor 41 to the evaporator 23 and the reformer 24.
　排気制御弁４２は、改質器２４へ連通するメイン流路３２ａと、蒸発器２３へ連通するバイパス流路３２ｂへ分配する排気ガスＥＧの流量の割合を調整可能に構成されている。排気制御弁４２は、バイパス流路３２ｂ側の弁の開度を小さくし、メイン流路３２ａ側の弁の開度を大きくすることによって、バイパス流路３２ｂへの排気ガスＥＧの流量を減少させ、メイン流路３２ａへの排気ガスＥＧの流量を増加させる。このように、排気制御弁４２は、排気燃焼器４１から改質器２４への高温の排気ガスＥＧの供給量を調整することで、改質器２４の運転温度を制御している。 The exhaust control valve 42 is configured so that the ratio of the flow rate of the exhaust gas EG distributed to the main flow passage 32a communicating with the reformer 24 and the bypass flow passage 32b communicating with the evaporator 23 can be adjusted. The exhaust control valve 42 reduces the flow rate of the exhaust gas EG to the bypass flow passage 32b by reducing the opening degree of the valve on the bypass flow passage 32b side and increasing the opening degree of the valve on the main flow passage 32a side. , Increase the flow rate of the exhaust gas EG to the main flow path 32a. In this way, the exhaust control valve 42 controls the operating temperature of the reformer 24 by adjusting the supply amount of the high-temperature exhaust gas EG from the exhaust combustor 41 to the reformer 24.
　制御部５０は、燃料電池システム１００の動作を制御する制御装置である。制御部５０は、ＲＯＭやＲＡＭから構成される記憶部と、ＣＰＵを主体に構成される演算部と、各種データや制御指令の送受信を行う入出力部と、を有する。 The control unit 50 is a control device that controls the operation of the fuel cell system 100. The control unit 50 includes a storage unit including a ROM and a RAM, an arithmetic unit including a CPU as a main component, and an input / output unit that transmits and receives various data and control commands.
　次に、図２を参照して、燃料電池システム１００の運転方法について説明する。図２は、燃料電池システム１００の運転手順を示すフローチャートである。 Next, an operation method of the fuel cell system 100 will be described with reference to FIG. FIG. 2 is a flowchart showing the operating procedure of the fuel cell system 100.
　燃料電池システム１００は、水含有燃料ＭＷを改質する改質器２４の触媒の改質性能の状態を検出し（ステップＳ１０１、Ｓ１０２）、改質器２４の触媒の劣化が検出された場合に、改質器２４に酸化剤ガスＯＧを供給して劣化回復処理を実施する（ステップＳ１０３～Ｓ１０５）。その後、酸化剤ガスＯＧが供給された改質器２４の触媒の回復状態を検出（ステップＳ１０６）し、触媒が未回復状態の場合は改質器２４の反応を促進するように運転条件を変更する（ステップＳ１０７）。以下、詳細に説明する。 The fuel cell system 100 detects the state of reforming performance of the catalyst of the reformer 24 that reforms the water-containing fuel MW (steps S101 and S102), and when deterioration of the catalyst of the reformer 24 is detected. Then, the oxidant gas OG is supplied to the reformer 24 to perform the deterioration recovery process (steps S103 to S105). Then, the recovery state of the catalyst of the reformer 24 to which the oxidant gas OG is supplied is detected (step S106), and if the catalyst is in the unrecovered state, the operating condition is changed so as to accelerate the reaction of the reformer 24. Yes (step S107). The details will be described below.
　まず、制御部５０は、温度センサ２５の検出信号から、改質器２４の入出口温度差ΔＴを取得する（ステップＳ１０１）。 First, the control unit 50 acquires the inlet / outlet temperature difference ΔT of the reformer 24 from the detection signal of the temperature sensor 25 (step S101).
　次に、制御部５０は、温度センサ２５の検出信号に基づいて、改質器２４の入出口温度差ΔＴが予め定めた閾値Ｔ１以下になったか否かを判断する（ステップＳ１０２）。 Next, the control unit 50 determines whether the inlet / outlet temperature difference ΔT of the reformer 24 has become equal to or less than a predetermined threshold T1 based on the detection signal of the temperature sensor 25 (step S102).
　ここで、燃料の改質においては、上述したように複数の反応（式（２）～式（７）を参照）が同時に進行し、各反応の反応熱も異なる。このため、各反応の進行度合いによって、改質ガスＲＧの組成が変化し、各反応の合計の反応熱も変化する。 Here, in the reforming of the fuel, as described above, a plurality of reactions (see Formulas (2) to (7)) simultaneously proceed, and the reaction heats of the respective reactions also differ. Therefore, the composition of the reformed gas RG changes depending on the progress of each reaction, and the total reaction heat of each reaction also changes.
　図３は、改質器２４の通常運転時における入口温度と出口温度の時間変化を示すグラフである。図３に示すように、通常運転中に改質器２４の触媒の劣化が進行すると、各反応の進行度合いが変化し、各反応の合計の反応熱も変化する。具体的には、発熱反応が支配的になって、反応熱が増加するため、改質器２４の出口温度は上昇する。したがって、改質器２４の入出口温度差ΔＴを検知することで、改質器２４の改質性能の変化を検知することができる。 FIG. 3 is a graph showing temporal changes in the inlet temperature and the outlet temperature during the normal operation of the reformer 24. As shown in FIG. 3, as the deterioration of the catalyst of the reformer 24 progresses during normal operation, the degree of progress of each reaction changes and the total reaction heat of each reaction also changes. Specifically, the exothermic reaction becomes dominant and the reaction heat increases, so that the outlet temperature of the reformer 24 rises. Therefore, by detecting the inlet / outlet temperature difference ΔT of the reformer 24, a change in the reforming performance of the reformer 24 can be detected.
　再び図２を参照して、制御部５０は、改質器２４の入出口温度差ΔＴが閾値Ｔ１を越えている場合には、改質器２４の改質性能が低下していないと判断する（ステップＳ１０２、ＮＯ）。この場合、Ｓ１０１の処理に戻る。 Referring again to FIG. 2, the control unit 50 determines that the reforming performance of the reformer 24 has not deteriorated when the inlet / outlet temperature difference ΔT of the reformer 24 exceeds the threshold T1. (Step S102, NO). In this case, the process returns to S101.
　一方、制御部５０は、改質器２４の入出口温度差ΔＴが閾値Ｔ１以下の場合には、改質器２４の改質性能が低下したと判断する（ステップＳ１０２、ＹＥＳ）。 On the other hand, when the inlet / outlet temperature difference ΔT of the reformer 24 is less than or equal to the threshold value T1, the control unit 50 determines that the reforming performance of the reformer 24 has deteriorated (step S102, YES).
　改質器２４の改質性能が低下したと判断した場合、制御部５０は、改質器２４へ酸化剤ガスＯＧを供給して触媒の表面に析出した炭素を酸化して除去する劣化回復処理を開始する（ステップＳ１０３）。 When it is determined that the reforming performance of the reformer 24 has deteriorated, the control unit 50 supplies the oxidant gas OG to the reformer 24 to oxidize and remove the carbon deposited on the surface of the catalyst. Is started (step S103).
　具体的には、制御部５０は、酸化剤ガス制御弁４３の流路３１ｂ側を開くように制御して、流路３１ｂを介して改質器２４の上流に酸化剤ガスＯＧを供給する（ステップＳ１０３）。なお、ステップＳ１０３より前の操作では、酸化剤ガス制御弁４３は、流路３１ａ側のみ開いており、流路３１ｂ側は閉じた状態である。これにより、次式（８）のように触媒の表面に付着した炭素が酸素によって酸化する燃焼反応（酸化反応）が進行し、二酸化炭素として排出される。 Specifically, the control unit 50 controls the oxidant gas control valve 43 so as to open the channel 31b side, and supplies the oxidant gas OG upstream of the reformer 24 via the channel 31b ( Step S103). In the operation before step S103, the oxidant gas control valve 43 is open only on the flow path 31a side and closed on the flow path 31b side. As a result, a combustion reaction (oxidation reaction) in which carbon adhering to the surface of the catalyst is oxidized by oxygen proceeds as in the following formula (8) and is discharged as carbon dioxide.
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000003
　改質器２４では、上記燃焼反応に加えて、下記に示すような部分酸化反応が開始され、改質ガスＲＧとして水素や一酸化炭素が生成される。これにより、劣化回復処理中においても燃料電池スタック１０へ改質ガスＲＧが供給されるため、発電は継続する。 In the reformer 24, in addition to the above combustion reaction, a partial oxidation reaction as shown below is started, and hydrogen or carbon monoxide is generated as the reformed gas RG. As a result, the reformed gas RG is supplied to the fuel cell stack 10 even during the deterioration recovery process, so that power generation continues.
Figure JPOXMLDOC01-appb-C000004
Figure JPOXMLDOC01-appb-C000004
　上記式（８）の燃焼反応や上記式（９）の部分酸化反応は、発熱反応である。したがって、改質器２４では発熱反応が支配的になる。 The combustion reaction of the above formula (8) and the partial oxidation reaction of the above formula (9) are exothermic reactions. Therefore, the exothermic reaction becomes dominant in the reformer 24.
　改質器２４の上流に酸化剤ガスＯＧの供給を開始した時刻をｔ＝０としたとき、所定時間ｔ＝ｔ１経過するまで酸化剤ガスＯＧの供給を続ける（ステップＳ１０４、ＮＯ）。所定時間ｔ＝ｔ１経過後（ステップＳ１０４、ＹＥＳ）、制御部５０は、酸化剤ガス制御弁４３の流路３１ｂ側を閉じるように制御して、改質器２４への酸化剤ガスＯＧの供給を停止する（ステップＳ１０５）。酸化剤ガスＯＧの供給を停止して所定時間経過すると、改質器２４内は燃焼反応および部分酸化反応が停止し、水蒸気改質反応のみが進行するようになる。 When the time when the supply of the oxidant gas OG is started upstream of the reformer 24 is t = 0, the supply of the oxidant gas OG is continued until a predetermined time t = t1 has elapsed (step S104, NO). After the elapse of the predetermined time t = t1 (YES in step S104), the control unit 50 controls the oxidant gas control valve 43 to close the flow path 31b side, and supplies the oxidant gas OG to the reformer 24. Is stopped (step S105). When the supply of the oxidant gas OG is stopped and a predetermined time elapses, the combustion reaction and the partial oxidation reaction are stopped in the reformer 24, and only the steam reforming reaction proceeds.
　次に、制御部５０は、温度センサ２５の検出信号に基づいて、改質器２４の入出口温度差ΔＴが予め定めた閾値Ｔ２以下になったか否かを判断する（ステップＳ１０６）。 Next, the control unit 50 determines whether the inlet / outlet temperature difference ΔT of the reformer 24 has become equal to or less than a predetermined threshold value T2 based on the detection signal of the temperature sensor 25 (step S106).
　制御部５０は、改質器２４の入出口温度差ΔＴが閾値Ｔ２を越えている場合には、ステップＳ１０３～Ｓ１０５の酸化剤ガスＯＧの供給による劣化回復処理によって触媒の劣化が回復し、改質器２４の改質性能が通常運転に必要な程度まで向上したと判断し（ステップＳ１０６、ＮＯ）、操作を終了する。この場合、改質器２４の性能低下の要因は、炭素析出（コーキング）による触媒の劣化であったと判断される。 When the inlet / outlet temperature difference ΔT of the reformer 24 exceeds the threshold T2, the control unit 50 recovers the catalyst deterioration by the deterioration recovery process by the supply of the oxidant gas OG in steps S103 to S105, and It is determined that the reforming performance of the quality control device 24 has improved to the extent necessary for normal operation (step S106, NO), and the operation ends. In this case, it is judged that the cause of the performance deterioration of the reformer 24 is the deterioration of the catalyst due to carbon deposition (coking).
　一方、制御部５０は、改質器２４の入出口温度差ΔＴが閾値Ｔ２以下の場合には、ステップＳ１０３～Ｓ１０５の酸化剤ガスＯＧの供給による劣化回復処理によっても触媒が未回復状態であり、改質器２４の改質性能が通常運転に必要な程度まで向上していないと判断する（ステップＳ１０６、ＹＥＳ）。この場合、改質器２４の性能低下の要因は、炭素析出以外の他の要因によるものと判断される。このように、劣化回復処理によって、炭素析出による触媒の劣化を回復できるとともに、改質性能の低下要因を特定することもできる。 On the other hand, when the inlet / outlet temperature difference ΔT of the reformer 24 is less than or equal to the threshold value T2, the control unit 50 indicates that the catalyst is in the unrecovered state even by the deterioration recovery process by the supply of the oxidizing gas OG in steps S103 to S105. It is determined that the reforming performance of the reformer 24 has not improved to the extent necessary for normal operation (step S106, YES). In this case, it is determined that the cause of the performance deterioration of the reformer 24 is due to other factors than the carbon deposition. As described above, the deterioration recovery process can recover the deterioration of the catalyst due to the carbon deposition and can identify the cause of the deterioration of the reforming performance.
　改質器２４の改質性能が通常運転に必要な程度まで向上していないと判断した場合、制御部５０は、排気制御弁４２のバイパス流路３２ｂ側の開度が小さく、メイン流路３２ａ側の開度が大きくなるように制御して、排気燃焼器４１からバイパス流路３２ｂへ流入する排気ガスＥＧの流量を減少させる（ステップＳ１０７）。これにより、排気燃焼器４１から改質器２４に供給される排気ガスＥＧの流入量を増大させて、改質器２４により大きな熱量を加えて加熱する。 When determining that the reforming performance of the reformer 24 has not improved to the extent necessary for normal operation, the control unit 50 determines that the opening degree of the exhaust control valve 42 on the side of the bypass passage 32b is small and the main passage 32a. The opening degree on the side is controlled to be large, and the flow rate of the exhaust gas EG flowing from the exhaust combustor 41 to the bypass passage 32b is reduced (step S107). As a result, the inflow amount of the exhaust gas EG supplied from the exhaust combustor 41 to the reformer 24 is increased, and a larger amount of heat is added to the reformer 24 for heating.
　図４は、改質器２４の改質性能と運転温度との関係を示すグラフである。上述したように改質器２４の改質性能は、運転温度が高いほど高くなる傾向にある。図４に示すように、改質器２４の改質性能が何らかの要因で低下した場合、通常の運転温度ＴＮから上昇させて運転温度ＴＨとする。これにより、触媒が活性化し、改質器２４の改質性能を目標改質性能もしくはそれ以上の性能まで向上させることができる。上昇温度（ＴＨ－ＴＮ）は、特に限定されないが、例えば、３０℃～６０℃とすることができる。上昇温度（ＴＨ－ＴＮ）が上記の範囲であれば、触媒金属のシンタリングや触媒基材の構造変化が生じる温度にまで高温に至らない。 FIG. 4 is a graph showing the relationship between the reforming performance of the reformer 24 and the operating temperature. As described above, the reforming performance of the reformer 24 tends to increase as the operating temperature increases. As shown in FIG. 4, when the reforming performance of the reformer 24 is lowered for some reason, the normal operating temperature T N is raised to the operating temperature T H. As a result, the catalyst is activated and the reforming performance of the reformer 24 can be improved to the target reforming performance or higher. Increasing the temperature (T H -T N) is not particularly limited, for example, be a 30 ℃ ~ 60 ℃. So long as the temperature increase (T H -T N) is described above, it does not lead to high temperatures to a temperature at which structural change of sintering of the catalytic metal and the catalyst substrate occurs.
　ステップＳ１０７において、何らかの要因によって改質器２４の性能低下が見られた場合、改質器２４の運転温度を上昇させることで性能が向上し、入出口温度差ΔＴは再び低下する。なお、測定する改質器２４の運転温度は、改質器２４の入口温度、出口温度または平均温度などを用いることができる。 In step S107, if the performance of the reformer 24 is degraded due to some factor, the performance is improved by increasing the operating temperature of the reformer 24, and the inlet / outlet temperature difference ΔT is reduced again. The operating temperature of the reformer 24 to be measured may be the inlet temperature, the outlet temperature or the average temperature of the reformer 24.
　次に、制御部５０は、温度センサ２５の検出信号に基づいて、改質器２４の入出口温度差ΔＴが予め定めた閾値Ｔ３以上になったか否かを判断する（ステップＳ１０８）。 Next, the control unit 50 determines whether or not the inlet / outlet temperature difference ΔT of the reformer 24 is equal to or larger than a predetermined threshold T3 based on the detection signal of the temperature sensor 25 (step S108).
　制御部５０は、改質器２４の入出口温度差ΔＴが閾値Ｔ３よりも低い場合には、改質器２４の改質性能が通常運転に必要な程度まで向上していないと判断する（ステップＳ１０８、ＮＯ）。この場合、ステップＳ１０７の処理へ戻り、制御部５０は、排気制御弁４２を制御して、排気燃焼器４１からバイパス流路３２ｂへ流入する排気ガスＥＧの流量を減少させる操作を繰り返す。その後、改質器２４の入出口温度差ΔＴが閾値Ｔ３以上（ステップＳ１０８、ＹＥＳ）となるまで排気ガスＥＧの流量を減少させる操作を繰り返す。なお、バイパス流路３２ｂへ流入する排気ガスＥＧの流量が０となった場合には、ステップＳ１０７を実行せずに操作を終了する。 When the inlet / outlet temperature difference ΔT of the reformer 24 is lower than the threshold value T3, the control unit 50 determines that the reforming performance of the reformer 24 has not been improved to the extent necessary for normal operation (step). S108, NO). In this case, returning to the process of step S107, the control unit 50 repeats the operation of controlling the exhaust control valve 42 to reduce the flow rate of the exhaust gas EG flowing from the exhaust combustor 41 into the bypass passage 32b. After that, the operation of reducing the flow rate of the exhaust gas EG is repeated until the inlet / outlet temperature difference ΔT of the reformer 24 becomes equal to or more than the threshold value T3 (step S108, YES). When the flow rate of the exhaust gas EG flowing into the bypass passage 32b becomes 0, the operation is ended without executing step S107.
　制御部５０は、改質器２４の入出口温度差ΔＴが閾値Ｔ３以上になると、改質器２４の改質性能が通常運転に必要な程度まで向上したと判断し（ステップＳ１０８、ＹＥＳ）、操作を終了する。 When the inlet / outlet temperature difference ΔT of the reformer 24 becomes equal to or larger than the threshold value T3, the control unit 50 determines that the reforming performance of the reformer 24 has improved to the extent necessary for normal operation (step S108, YES), The operation ends.
　図５は、上記燃料電池システム１００の運転手順を実行した際の改質器２４の入口温度と出口温度の時間変化を示すグラフである。 FIG. 5 is a graph showing changes with time in the inlet temperature and the outlet temperature of the reformer 24 when the operation procedure of the fuel cell system 100 is executed.
　図５に示すように、ステップＳ１０３において酸化剤ガスＯＧを供給してからステップＳ１０５において酸化剤ガスＯＧの供給を停止するまでの劣化回復処理中は、改質器２４の温度は急激に上昇する。これは、改質器２４において燃焼反応（式（８））および部分酸化反応（式（９））が進行して発熱反応が支配的になるためである。 As shown in FIG. 5, the temperature of the reformer 24 rapidly increases during the deterioration recovery process from the supply of the oxidant gas OG in step S103 to the stop of the supply of the oxidant gas OG in step S105. . This is because the combustion reaction (equation (8)) and the partial oxidation reaction (equation (9)) proceed in the reformer 24 and the exothermic reaction becomes dominant.
　ステップＳ１０５において酸化剤ガスＯＧの供給を停止すると、改質器２４の出口温度は低下する。これは、酸化剤ガスＯＧの供給を停止することによって、発熱反応である燃焼反応（式（８））および部分酸化反応（式（９））が停止して、改質器２４が通常運転に戻る。これにより、主に水蒸気改質反応（式（１））が進行して吸熱反応が支配的になるためである。 When the supply of the oxidant gas OG is stopped in step S105, the outlet temperature of the reformer 24 drops. This is because by stopping the supply of the oxidant gas OG, the combustion reaction (equation (8)) and the partial oxidation reaction (equation (9)), which are exothermic reactions, are stopped and the reformer 24 is put into normal operation. Return. This is because the steam reforming reaction (equation (1)) mainly proceeds and the endothermic reaction becomes dominant.
　ステップＳ１０６において、改質器２４の入出口温度差ΔＴが予め定めた閾値Ｔ２以下になった場合、制御部５０は、排気燃焼器４１からバイパス流路３２ｂへ流入する排気ガスＥＧの流量を減少させて改質器２４を加熱する。これにより、改質器２４の触媒が活性化し、吸熱反応が支配的である水蒸気改質反応が進行するため改質器２４の出口温度はさらに低下する。これにより、改質器２４の入出口温度差ΔＴは、予め定めた閾値Ｔ３以上となり、改質器２４の改質性能が向上する。 In step S106, when the inlet / outlet temperature difference ΔT of the reformer 24 becomes equal to or less than the predetermined threshold value T2, the control unit 50 reduces the flow rate of the exhaust gas EG flowing from the exhaust combustor 41 into the bypass passage 32b. Then, the reformer 24 is heated. As a result, the catalyst of the reformer 24 is activated and the steam reforming reaction in which the endothermic reaction is dominant proceeds, so that the outlet temperature of the reformer 24 further decreases. As a result, the inlet / outlet temperature difference ΔT of the reformer 24 becomes equal to or greater than the predetermined threshold value T3, and the reforming performance of the reformer 24 is improved.
　ここで、改質器２４の入出口温度差ΔＴの閾値Ｔ１、Ｔ２、Ｔ３は、必要量の改質ガスＲＧを供給するための改質性能を維持できる程度の値に予め設定しておく。本実施形態では、閾値Ｔ１、Ｔ２、Ｔ３の大小関係は、Ｔ１≧Ｔ３≧Ｔ２とする。ステップＳ１０２の最初の劣化回復検出の判断は、最も厳しい条件として劣化検出の感度を上げるため、Ｔ１は最も大きい値に設定することが好ましい。また、ステップＳ１０６の２回目の劣化回復検出の判断の閾値Ｔ２は、ステップＳ１０８の３回目の劣化回復検出の判断の閾値Ｔ３よりも条件を緩く、Ｔ３＞Ｔ２に設定しておくことが好ましい。これは、ステップＳ１０８の３回目の判断時は、改質器２４の反応を促進するように改質器２４の運転温度を上昇させた（ステップＳ１０７）後のため、吸熱反応がより進行することによって出口温度が低下し、ステップＳ１０６の２回目の判断時に比べて入出口温度差ΔＴが大きくなるためである。なお、Ｔ１、Ｔ２、Ｔ３の大小関係は、通常運転に必要な程度の改質器２４の改質性能が得られる温度であれば上記に限定されず、同一の値を用いてもよいし、大小関係を入れ替えてもよい。 Here, the thresholds T1, T2, and T3 of the inlet / outlet temperature difference ΔT of the reformer 24 are preset to values that can maintain the reforming performance for supplying the required amount of the reformed gas RG. In the present embodiment, the magnitude relationship among the threshold values T1, T2, and T3 is T1 ≧ T3 ≧ T2. It is preferable to set T1 to the largest value in order to raise the sensitivity of deterioration detection as the most severe condition for the first judgment of deterioration recovery detection in step S102. Further, the threshold value T2 for the determination of the second deterioration recovery detection in step S106 is preferably set to T3> T2 so that the condition is looser than the threshold value T3 for the determination of the third deterioration recovery detection in step S108. This is because, at the time of the third determination in step S108, since the operating temperature of the reformer 24 is increased so as to promote the reaction of the reformer 24 (step S107), the endothermic reaction further progresses. This is because the outlet temperature decreases, and the inlet / outlet temperature difference ΔT becomes larger than that at the time of the second determination in step S106. The magnitude relationship between T1, T2, and T3 is not limited to the above as long as it is a temperature at which the reforming performance of the reformer 24 required for normal operation is obtained, and the same value may be used. You may change the size relationship.
　以上説明したように、本実施形態に係る燃料電池システム１００は、改質器２４に酸化剤ガスＯＧを供給して改質器２４の触媒の劣化を回復する劣化回復手段（酸化剤供給部３１）と、劣化回復手段による触媒の回復状態を検出する劣化回復検出手段（温度センサ２５）と、触媒が未回復状態であることを示す劣化回復検出手段からの検出信号に基づいて、改質器２４の反応を促進するように運転条件を変更する運転条件変更手段（排気燃焼器４１および排気制御弁４２）と、を有する。 As described above, in the fuel cell system 100 according to the present embodiment, deterioration recovery means (oxidizer supply unit 31 that recovers the deterioration of the catalyst of the reformer 24 by supplying the oxidant gas OG to the reformer 24. ), A deterioration recovery detecting means (temperature sensor 25) for detecting the recovery state of the catalyst by the deterioration recovering means, and a detection signal from the deterioration recovery detecting means indicating that the catalyst is in an unrecovered state. The operating condition changing means (the exhaust combustor 41 and the exhaust control valve 42) for changing the operating condition so as to promote the reaction of 24.
　また、本実施形態に係る燃料電池システム１００の運転方法は、水含有燃料ＭＷ（燃料に相当）を改質する改質器２４の触媒の劣化が検出された場合に、改質器２４に酸化剤ガスＯＧを供給し、酸化剤ガスＯＧが供給された改質器２４の触媒の回復状態を検出し、触媒が未回復状態の場合は改質器２４の反応を促進するように運転条件を変更する。 In addition, the operation method of the fuel cell system 100 according to the present embodiment is performed by oxidizing the reformer 24 when the catalyst of the reformer 24 that reforms the water-containing fuel MW (corresponding to fuel) is detected. The agent gas OG is supplied, the recovery state of the catalyst of the reformer 24 to which the oxidant gas OG is supplied is detected, and the operating condition is set so as to accelerate the reaction of the reformer 24 when the catalyst is not recovered. change.
　上記燃料電池システム１００および燃料電池システム１００の運転方法によれば、改質器２４の改質性能の低下要因が炭素析出に起因する場合、改質器２４への酸化剤ガスＯＧの供給によって、改質器２４の改質性能を回復させることができる。一方、改質器２４の改質性能の低下要因が炭素析出以外の場合は、触媒が未回復状態であることを検出し、改質器２４の反応を促進するように運転条件を変更することによって、燃料電池システム１００を停止せずに運転を継続することができる。このように、上記燃料電池システム１００および燃料電池システムの運転方法によれば、様々な改質器２４の改質性能の低下要因に対応することができる。また、上記燃料電池システム１００および燃料電池システムの運転方法によれば、改質性能の低下要因を特定することもできる。 According to the fuel cell system 100 and the method of operating the fuel cell system 100 described above, when the factor that deteriorates the reforming performance of the reformer 24 is due to carbon deposition, by supplying the oxidant gas OG to the reformer 24, The reforming performance of the reformer 24 can be restored. On the other hand, when the cause of the deterioration of the reforming performance of the reformer 24 is other than carbon deposition, it is detected that the catalyst is in an unrecovered state and the operating conditions are changed so as to promote the reaction of the reformer 24. Thus, the fuel cell system 100 can continue to operate without stopping. As described above, according to the fuel cell system 100 and the method of operating the fuel cell system, it is possible to deal with various factors causing the deterioration of the reforming performance of the reformer 24. Further, according to the above fuel cell system 100 and the method of operating the fuel cell system, it is possible to identify the cause of the deterioration of the reforming performance.
　また、運転条件変更手段は、劣化回復検出手段からの検出信号に基づいて、改質器２４を加熱する加熱部を有する。加熱部によって、改質器２４を加熱することによって、触媒を活性化させて改質性能を向上させることができる。なお、本実施形態では、加熱部は、排気燃焼器４１および排気制御弁４２によって構成される。 Also, the operating condition changing means has a heating part for heating the reformer 24 based on the detection signal from the deterioration recovery detecting means. By heating the reformer 24 by the heating unit, the catalyst can be activated and the reforming performance can be improved. In the present embodiment, the heating unit is composed of the exhaust combustor 41 and the exhaust control valve 42.
　また、劣化回復検出手段は、改質器２４の入口温度と出口温度との温度差ΔＴに基づいて触媒の回復状態を検出する温度センサ２５を有する。改質器２４の入口温度と出口温度と差を検知することで、改質器２４における反応の進行度合いの変化、すなわち改質性能の状態を検知できる。 Further, the deterioration recovery detecting means has a temperature sensor 25 for detecting the recovery state of the catalyst based on the temperature difference ΔT between the inlet temperature and the outlet temperature of the reformer 24. By detecting the difference between the inlet temperature and the outlet temperature of the reformer 24, it is possible to detect the change in the progress of the reaction in the reformer 24, that is, the state of the reforming performance.
　＜第２実施形態＞
　次に、図６および図７を参照して、本発明の第２実施形態に係る燃料電池システム２００およびその運転方法について説明する。 <Second Embodiment>
Next, with reference to FIGS. 6 and 7, a fuel cell system 200 according to a second embodiment of the present invention and an operating method thereof will be described.
　図６は、第２実施形態に係る燃料電池システム２００を示す概略構成図である。図６に示すように、第２実施形態に係る燃料電池システム２００は、燃料電池スタック１０の出力を検出する出力センサ５４をさらに有する点で前述した第１実施形態と異なる。出力センサ５４は、「劣化回復検出手段」に相当する。なお、前述した第１実施形態と同様の構成については、同一の符号を付してその説明を省略する。 FIG. 6 is a schematic configuration diagram showing a fuel cell system 200 according to the second embodiment. As shown in FIG. 6, the fuel cell system 200 according to the second embodiment differs from the first embodiment described above in that it further includes an output sensor 54 that detects the output of the fuel cell stack 10. The output sensor 54 corresponds to "deterioration recovery detection means". The same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.
　出力センサ５４は、燃料電池スタック１０から出力される電気出力Ｐを検出する。ここで、燃料電池スタック１０の出力は、燃料電池スタック１０に供給される改質ガスＲＧの組成に依存する。また、改質ガスＲＧの組成は、改質器２４の改質性能に依存する。したがって、燃料電池スタック１０の電気出力Ｐを検出することによって、改質ガスＲＧの組成の悪化による燃料電池スタック１０の出力低下を抑制することができる。 The output sensor 54 detects an electric output P output from the fuel cell stack 10. Here, the output of the fuel cell stack 10 depends on the composition of the reformed gas RG supplied to the fuel cell stack 10. The composition of the reformed gas RG depends on the reforming performance of the reformer 24. Therefore, by detecting the electric output P of the fuel cell stack 10, it is possible to suppress the output reduction of the fuel cell stack 10 due to the deterioration of the composition of the reformed gas RG.
　図７は、第２実施形態に係る燃料電池システムの運転手順を示すフローチャートである。前述した第１実施形態では、改質器２４の劣化回復を検出する際に、改質器２４の入出口温度差ΔＴの値を基に改質性能の状態を判断していたのに対し、第２実施形態では、燃料電池スタック１０の電気出力Ｐを基に改質性能の状態を判断する点で異なる。図７に示す燃料電池システム２００の運転手順のステップＳ２０１、Ｓ２０２、Ｓ２０６、Ｓ２０８以外は、図２に示す前述した第１実施形態と同様のため、同一の符号を付してその説明を省略する。 FIG. 7 is a flowchart showing the operating procedure of the fuel cell system according to the second embodiment. In the first embodiment described above, when the deterioration recovery of the reformer 24 is detected, the state of the reforming performance is determined based on the value of the inlet / outlet temperature difference ΔT of the reformer 24. The second embodiment is different in that the state of the reforming performance is judged based on the electric output P of the fuel cell stack 10. The steps other than steps S201, S202, S206, and S208 of the operation procedure of the fuel cell system 200 shown in FIG. 7 are the same as those of the above-described first embodiment shown in FIG. .
　まず、制御部５０は、出力センサ５４の検出信号から、燃料電池スタック１０の電気出力Ｐを示す検出値を取得する（ステップＳ２０１）。 First, the control unit 50 acquires a detection value indicating the electric output P of the fuel cell stack 10 from the detection signal of the output sensor 54 (step S201).
　次に、制御部５０は、出力センサ５４の検出信号に基づいて、電気出力Ｐが予め定めた閾値Ｐ１以下であるか否かを判断する（ステップＳ２０２）。 Next, the control unit 50 determines whether or not the electric output P is less than or equal to a predetermined threshold P1 based on the detection signal of the output sensor 54 (step S202).
　制御部５０は、電気出力Ｐが予め定めた閾値Ｐ１を越えている場合には、改質器２４の改質性能が低下していないと判断する（ステップＳ２０２、ＮＯ）。この場合、Ｓ２０１の処理に戻る。 The control unit 50 determines that the reforming performance of the reformer 24 has not deteriorated when the electric output P exceeds the predetermined threshold value P1 (step S202, NO). In this case, the process returns to S201.
　一方、制御部５０は、電気出力Ｐが予め定めた閾値Ｐ１以下の場合には、改質器２４の改質性能が低下したと判断する（ステップＳ２０２、ＹＥＳ）。 On the other hand, the control unit 50 determines that the reforming performance of the reformer 24 has deteriorated when the electric output P is less than or equal to the predetermined threshold P1 (step S202, YES).
　改質器２４の改質性能が低下したと判断した場合、制御部５０は、前述した第１実施形態と同様に、劣化回復処理を実行する（ステップＳ１０３～Ｓ１０５）。 When it is determined that the reforming performance of the reformer 24 has deteriorated, the control unit 50 executes the deterioration recovery process as in the first embodiment described above (steps S103 to S105).
　次に、制御部５０は、出力センサ５４の検出信号に基づいて、電気出力Ｐが予め定めた閾値Ｐ２以下になったか否かを判断する（ステップＳ２０６）。 Next, the control unit 50 determines, based on the detection signal of the output sensor 54, whether or not the electric output P has become equal to or less than a predetermined threshold P2 (step S206).
　制御部５０は、電気出力Ｐが予め定めた閾値Ｐ２を越えている場合には、劣化回復処理によって触媒の劣化が回復し、改質器２４の改質性能が通常運転に必要な程度まで向上したと判断し（ステップＳ２０６、ＮＯ）、操作を終了する。この場合、改質器２４の性能低下の要因は、炭素析出（コーキング）による触媒の劣化であったと判断される。 When the electric output P exceeds the predetermined threshold value P2, the control unit 50 recovers the deterioration of the catalyst by the deterioration recovery process and improves the reforming performance of the reformer 24 to the extent necessary for normal operation. It is determined that it has been done (step S206, NO), and the operation ends. In this case, it is judged that the cause of the performance deterioration of the reformer 24 is the deterioration of the catalyst due to carbon deposition (coking).
　一方、制御部５０は、電気出力Ｐが予め定めた閾値Ｐ２以下の場合には、劣化回復処理によっても触媒が未回復状態であり、改質器２４の改質性能が通常運転に必要な程度まで向上していないと判断する（ステップＳ２０６、ＹＥＳ）。この場合、改質器２４の性能低下の要因は、炭素析出以外の他の要因によるものと判断される。 On the other hand, when the electric output P is less than or equal to the predetermined threshold value P2, the control unit 50 indicates that the catalyst is in an unrecovered state even by the deterioration recovery process, and the reforming performance of the reformer 24 is the degree required for normal operation. It is determined that it has not improved (step S206, YES). In this case, it is determined that the cause of the performance deterioration of the reformer 24 is due to other factors than the carbon deposition.
　改質器２４の改質性能が通常運転に必要な程度まで向上していないと判断した場合、制御部５０は、前述した第１実施形態と同様に、排気燃焼器４１からバイパス流路３２ｂへ流入する排気ガスＥＧの流量を減少させて改質器２４を加熱する（ステップＳ１０７）。 When it is determined that the reforming performance of the reformer 24 has not improved to the extent necessary for normal operation, the control unit 50 moves from the exhaust combustor 41 to the bypass flow passage 32b, as in the first embodiment described above. The reformer 24 is heated by reducing the flow rate of the inflowing exhaust gas EG (step S107).
　次に、制御部５０は、出力センサ５４の検出信号に基づいて、電気出力Ｐが予め定めた閾値Ｐ３以上になったか否かを判断する（ステップＳ２０８）。 Next, the control unit 50 determines, based on the detection signal of the output sensor 54, whether or not the electric output P has become equal to or higher than a predetermined threshold P3 (step S208).
　制御部５０は、電気出力Ｐが予め定めた閾値Ｐ３よりも低い場合には、改質器２４の改質性能が通常運転に必要な程度まで向上していないと判断する（ステップＳ２０８、ＮＯ）。この場合、ステップＳ１０７の処理へ戻り、制御部５０は、排気制御弁４２を制御して、排気燃焼器４１からバイパス流路３２ｂへ流入する排気ガスＥＧの流量を減少させる操作を繰り返す。その後、電気出力Ｐが予め定めた閾値Ｐ３以上（ステップＳ２０８、ＹＥＳ）となるまで排気ガスＥＧの流量を減少させる操作を繰り返す。なお、バイパス流路３２ｂへ流入する排気ガスＥＧの流量が０となった場合には、ステップＳ１０７を実行せずに操作を終了する。 When the electric output P is lower than the predetermined threshold value P3, the control unit 50 determines that the reforming performance of the reformer 24 has not improved to the extent necessary for normal operation (step S208, NO). . In this case, returning to the process of step S107, the control unit 50 repeats the operation of controlling the exhaust control valve 42 to reduce the flow rate of the exhaust gas EG flowing from the exhaust combustor 41 into the bypass passage 32b. After that, the operation of reducing the flow rate of the exhaust gas EG is repeated until the electric output P becomes equal to or larger than the predetermined threshold P3 (step S208, YES). When the flow rate of the exhaust gas EG flowing into the bypass passage 32b becomes 0, the operation is ended without executing step S107.
　制御部５０は、電気出力Ｐが予め定めた閾値Ｐ３以上になると、改質器２４の改質性能が通常運転に必要な程度まで向上したと判断し（ステップＳ２０８、ＹＥＳ）、操作を終了する。 When the electric output P becomes equal to or higher than the predetermined threshold value P3, the control unit 50 determines that the reforming performance of the reformer 24 has improved to the extent necessary for normal operation (step S208, YES), and ends the operation. .
　予め設定する電気出力Ｐの閾値Ｐ１、Ｐ２、Ｐ３は、Ｐ１≧Ｐ３≧Ｐ２とする。ステップＳ２０２の最初の劣化回復検出の判断は、最も厳しい条件として検出の感度を上げるため、Ｐ１は最も大きい値に設定することが好ましい。また、ステップＳ２０６の２回目の劣化回復検出の判断は、ステップＳ２０８の３回目の劣化回復検出の判断よりも条件を緩く、Ｐ３＞Ｐ２に設定しておくことが好ましい。これは、前述した第１実施形態と同様の理由によるものである。なお、Ｐ１、Ｐ２、Ｐ３は、同一の値を用いてもよい。 The preset thresholds P1, P2, P3 of the electric output P are P1 ≧ P3 ≧ P2. The determination of the first deterioration recovery detection in step S202 is preferably set to the largest value, because the detection sensitivity is raised as the most severe condition. Further, it is preferable that the determination of the second deterioration recovery detection in step S206 is set to P3> P2, which is looser than the determination of the third deterioration recovery detection in step S208. This is for the same reason as in the first embodiment described above. The same values may be used for P1, P2, and P3.
　以上説明したように、本実施形態に係る燃料電池システム２００の劣化回復検出手段は、燃料電池スタック１０の出力に基づいて触媒の回復状態を検出する出力センサ５４を有する。燃料電池スタック１０の電気出力Ｐを検出することによって、改質ガスＲＧの組成の悪化による燃料電池スタック１０の出力低下を抑制することができる。 As described above, the deterioration recovery detection unit of the fuel cell system 200 according to the present embodiment has the output sensor 54 that detects the recovery state of the catalyst based on the output of the fuel cell stack 10. By detecting the electrical output P of the fuel cell stack 10, it is possible to suppress the output reduction of the fuel cell stack 10 due to the deterioration of the composition of the reformed gas RG.
　＜第３実施形態＞
　次に、図８および図９を参照して、本発明の第３実施形態に係る燃料電池システム３００およびその運転方法について説明する。 <Third Embodiment>
Next, with reference to FIGS. 8 and 9, a fuel cell system 300 according to a third embodiment of the present invention and an operating method thereof will be described.
　図８は、第３実施形態に係る燃料電池システム３００を示す概略構成図である。 FIG. 8 is a schematic configuration diagram showing a fuel cell system 300 according to the third embodiment.
　第３実施形態に係る燃料電池システム３００は、改質器２４を加熱する「加熱部」として加熱ヒータ２６を有する点で前述した第１実施形態と異なる。また、排気ガスＥＧのバイパス流路３２ｂは設けられていない点でも前述した第１実施形態と異なる。加熱ヒータ２６は、「運転条件変更手段」に相当する。なお、前述した第１実施形態と同様の構成については、同一の符号を付してその説明を省略する。 The fuel cell system 300 according to the third embodiment is different from the above-described first embodiment in that a heating heater 26 is provided as a “heating unit” for heating the reformer 24. In addition, the bypass passage 32b for the exhaust gas EG is not provided, which is also different from the first embodiment described above. The heater 26 corresponds to "operating condition changing means". The same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.
　加熱ヒータ２６は、改質器２４を加熱する電気ヒータや温風ヒータ等によって構成される。加熱ヒータ２６の発熱量は、制御部５０により制御される。 The heating heater 26 is composed of an electric heater for heating the reformer 24, a warm air heater, or the like. The heat generation amount of the heater 26 is controlled by the control unit 50.
　図９は、第３実施形態に係る燃料電池システム３００の運転手順を示すフローチャートである。図９に示す燃料電池システム３００の運転手順のステップＳ３０７以外は、図２に示す前述した第１実施形態と同様のため、同一の符号を付してその説明を省略する。 FIG. 9 is a flowchart showing the operating procedure of the fuel cell system 300 according to the third embodiment. Except for step S307 in the operation procedure of the fuel cell system 300 shown in FIG. 9, it is the same as the above-described first embodiment shown in FIG. 2, and therefore the same reference numerals are given and the description thereof is omitted.
　ステップＳ３０７では、制御部５０は、加熱ヒータ２６の発熱量が大きくなるように制御して、改質器２４を加熱する。これにより、前述した第１実施形態のように排気制御弁４２を制御して排気ガスＥＧの流量を調整する方法に比べて、より簡単な構成で改質器２４を加熱することができる。 In step S307, the control unit 50 heats the reformer 24 by controlling the heating amount of the heating heater 26 to increase. As a result, the reformer 24 can be heated with a simpler configuration as compared with the method of controlling the exhaust control valve 42 to adjust the flow rate of the exhaust gas EG as in the first embodiment described above.
　＜第４実施形態＞
　次に、図１０および図１１を参照して、本発明の第４実施形態に係る燃料電池システムの運転方法について説明する。 <Fourth Embodiment>
Next, a method of operating the fuel cell system according to the fourth embodiment of the present invention will be described with reference to FIGS. 10 and 11.
　第４実施形態に係る燃料電池システムは、図１に示す第１実施形態に係る燃料電池システム１００を用いる。図１を参照して、第４実施形態に係る燃料電池システムにおいて、流量調整部２２は、「運転条件変更手段」に相当する。制御部５０は、流量調整部２２を制御して、蒸発器２３へ供給される水含有燃料ＭＷの流量を減少させて、改質器２４へ供給される混合ガスＭＧの流量Ｑを減少させることによって改質器２４の反応を促進するように運転条件を変更している。 The fuel cell system according to the fourth embodiment uses the fuel cell system 100 according to the first embodiment shown in FIG. With reference to FIG. 1, in the fuel cell system according to the fourth embodiment, the flow rate adjusting unit 22 corresponds to “operating condition changing means”. The control unit 50 controls the flow rate adjusting unit 22 to reduce the flow rate of the water-containing fuel MW supplied to the evaporator 23 and reduce the flow rate Q of the mixed gas MG supplied to the reformer 24. The operating conditions are changed so as to accelerate the reaction of the reformer 24.
　図１０は、第４実施形態に係る燃料電池システムの運転手順を示すフローチャートである。図１０に示す燃料電池システムの運転手順のステップＳ４０７～Ｓ４１１以外は、図２に示す前述した第１実施形態と同様のため、同一の符号を付してその説明を省略する。 FIG. 10 is a flowchart showing the operating procedure of the fuel cell system according to the fourth embodiment. The steps other than steps S407 to S411 of the operation procedure of the fuel cell system shown in FIG. 10 are the same as those in the above-described first embodiment shown in FIG.
　図１１は、改質器２４へ供給される混合ガスＭＧの単位時間当たりの流量（以下、「燃料流量Ｑ」と称する。）を変えた場合の改質器２４の改質性能と運転温度との関係を示すグラフである。改質器２４の触媒は、改質器２４における燃料流量Ｑが高いほど改質性能が低下する傾向がある。これは、触媒の表面への混合ガスＭＧの接触時間が減少することによって、改質反応が進みにくくなるためである。一方で、燃料流量Ｑを減らすと、触媒の表面への混合ガスＭＧの接触時間が長くなり、改質器２４の反応が促進されて改質性能が向上する。したがって、図１１に示すように、燃料流量Ｑを減らすことによって、通常の運転温度ＴＮにおいて運転温度を変えずに改質器２４の改質性能を目標改質性能もしくはそれ以上の性能まで向上させることができる。 FIG. 11 shows the reforming performance and operating temperature of the reformer 24 when the flow rate of the mixed gas MG supplied to the reformer 24 per unit time (hereinafter, referred to as “fuel flow rate Q”) is changed. It is a graph which shows the relationship of. The reforming performance of the catalyst of the reformer 24 tends to decrease as the fuel flow rate Q in the reformer 24 increases. This is because the contact time of the mixed gas MG with the surface of the catalyst is reduced and the reforming reaction is less likely to proceed. On the other hand, when the fuel flow rate Q is reduced, the contact time of the mixed gas MG with the surface of the catalyst becomes longer, the reaction of the reformer 24 is promoted, and the reforming performance is improved. Therefore, as shown in FIG. 11, by reducing the fuel flow rate Q, the reforming performance of the reformer 24 is improved to the target reforming performance or higher at the normal operating temperature T N without changing the operating temperature. Can be made.
　本実施形態では、上記性質に着目して、ステップＳ１０３～Ｓ１０５の劣化回復処理によって改質器２４の改質性能が通常運転に必要な程度まで向上していないと判断した場合（ステップＳ１０６、ＹＥＳ）、流量調整部２２を制御して、改質器２４へ供給される混合ガスＭＧの流量Ｑを減少させる（ステップＳ４０７）。これにより、触媒の表面への混合ガスＭＧの接触時間を増加させて、改質器２４の反応を促進し、改質器２４の改質性能を向上させる。 In this embodiment, paying attention to the above properties, when it is determined that the reforming performance of the reformer 24 has not been improved to the extent necessary for normal operation by the deterioration recovery process of steps S103 to S105 (step S106, YES). ), And controls the flow rate adjusting unit 22 to decrease the flow rate Q of the mixed gas MG supplied to the reformer 24 (step S407). As a result, the contact time of the mixed gas MG with the surface of the catalyst is increased, the reaction of the reformer 24 is promoted, and the reforming performance of the reformer 24 is improved.
　次に、制御部５０は、改質器２４の入出口温度差ΔＴが予め定めた閾値Ｔ４以上になったか否かを判断し、改質器２４の改質性能が通常運転に必要な程度まで向上したか否かを確認する（ステップＳ４０８）。 Next, the control unit 50 determines whether or not the inlet / outlet temperature difference ΔT of the reformer 24 has become equal to or greater than a predetermined threshold T4, and the reforming performance of the reformer 24 is adjusted to a level required for normal operation. It is confirmed whether or not it has improved (step S408).
　改質器２４の改質性能が通常運転に必要な程度まで向上していないと判断した場合（ステップＳ４０８、ＮＯ）、制御部５０は、燃料流量Ｑが最低流量Ｑ１以上か否かを判断する（ステップＳ４０９）。燃料流量Ｑが極端に低下すると、燃料電池スタック１０の発電に必要な改質ガスＲＧを得られなくなる。このため、「最低流量Ｑ１」は、燃料電池スタック１０の発電性能を担保できる燃料流量に予め設定しておく。 When it is determined that the reforming performance of the reformer 24 has not improved to the extent necessary for normal operation (step S408, NO), the control unit 50 determines whether the fuel flow rate Q is equal to or higher than the minimum flow rate Q1. (Step S409). If the fuel flow rate Q is extremely reduced, the reformed gas RG required for power generation of the fuel cell stack 10 cannot be obtained. Therefore, the “minimum flow rate Q1” is set in advance to a fuel flow rate that can ensure the power generation performance of the fuel cell stack 10.
　燃料流量Ｑが最低流量Ｑ１以上の場合には、ステップＳ４０７の処理へ戻り、制御部５０は、流量調整部２２を制御して、改質器２４へ供給する水含有燃料ＭＷの流量Ｑを減少させる操作を繰り返す（ステップＳ４０７）。その後、改質器２４の入出口温度差ΔＴが閾値Ｔ４以上の場合には、改質器２４の改質性能が通常運転に必要な程度まで向上したと判断し（ステップＳ４０８、ＹＥＳ）、操作を終了する。 When the fuel flow rate Q is equal to or higher than the minimum flow rate Q1, the process returns to step S407, and the control unit 50 controls the flow rate adjusting unit 22 to decrease the flow rate Q of the water-containing fuel MW supplied to the reformer 24. The operation to be repeated is repeated (step S407). After that, when the inlet / outlet temperature difference ΔT of the reformer 24 is equal to or larger than the threshold value T4, it is determined that the reforming performance of the reformer 24 has improved to the extent necessary for normal operation (YES in step S408), and the operation is performed. To finish.
　一方、燃料流量Ｑが最低流量Ｑ１を下回る場合（ステップＳ４０９、ＮＯ）は、改質器２４の運転温度を上昇させる（ステップＳ４１０）。改質器２４の運転温度を上昇させる方法としては、前述した第１実施形態のように排気燃焼器４１からバイパス流路３２ｂへ流入する排気ガスＥＧの流量を減少させる方法を用いてもよいし、加熱ヒータ２６を用いて改質器２４を直接的に加熱する方法を用いてもよい。燃料電池システムのエネルギー効率を向上させる観点からは、バイパス流路３２ｂへ流入する排気ガスＥＧの流量を減少させる方法によって排気ガスＥＧの熱量を利用して改質器２４を加熱することが好ましい。 On the other hand, when the fuel flow rate Q is lower than the minimum flow rate Q1 (step S409, NO), the operating temperature of the reformer 24 is increased (step S410). As a method of increasing the operating temperature of the reformer 24, a method of reducing the flow rate of the exhaust gas EG flowing from the exhaust combustor 41 to the bypass passage 32b as in the first embodiment described above may be used. Alternatively, a method of directly heating the reformer 24 using the heater 26 may be used. From the viewpoint of improving the energy efficiency of the fuel cell system, it is preferable to heat the reformer 24 using the heat quantity of the exhaust gas EG by a method of reducing the flow rate of the exhaust gas EG flowing into the bypass flow passage 32b.
　次に、制御部５０は、改質器２４の入出口温度差ΔＴが予め定めた閾値Ｔ５以上になったか否かを判断する（ステップＳ４１１）。改質器２４の入出口温度差ΔＴが予め定めた閾値Ｔ５以上になった場合（ステップＳ４１１、ＹＥＳ）は、改質器２４の改質性能が通常運転に必要な程度まで向上したと判断し、操作を終了する。 Next, the control unit 50 determines whether or not the inlet / outlet temperature difference ΔT of the reformer 24 is equal to or larger than a predetermined threshold value T5 (step S411). When the inlet / outlet temperature difference ΔT of the reformer 24 becomes equal to or larger than the predetermined threshold T5 (step S411, YES), it is determined that the reforming performance of the reformer 24 has improved to the extent necessary for normal operation. , The operation ends.
　一方、改質器２４の入出口温度差ΔＴが予め定めた閾値Ｔ５を下回る場合（ステップＳ４１１、ＮＯ）は、改質器２４の改質性能が通常運転に必要な程度まで向上していないと判断し、ステップＳ４１０の処理へ戻り、制御部５０は、改質器２４の運転温度を上昇させる操作を繰り返す。その後、改質器２４の入出口温度差ΔＴが閾値Ｔ５以上となった場合には、改質器２４の改質性能が通常運転に必要な程度まで向上したと判断し（ステップＳ４１１、ＹＥＳ）、操作を終了する。 On the other hand, when the inlet / outlet temperature difference ΔT of the reformer 24 is less than the predetermined threshold T5 (step S411, NO), the reforming performance of the reformer 24 has not been improved to the extent necessary for normal operation. After making a determination and returning to the process of step S410, the control unit 50 repeats the operation of increasing the operating temperature of the reformer 24. After that, when the inlet / outlet temperature difference ΔT of the reformer 24 becomes equal to or larger than the threshold value T5, it is determined that the reforming performance of the reformer 24 has improved to the extent necessary for normal operation (step S411, YES). , The operation ends.
　なお、本実施形態では、酸化剤ガスＯＧの供給による劣化回復処理によって改質器２４の改質性能が通常運転に必要な程度まで向上していないと判断した場合（ステップＳ１０６、ＹＥＳ）、改質器２４の運転温度を上昇させる操作（ステップＳ４１０）よりも燃料流量Ｑを減らす操作（ステップＳ４０７）を優先的に実施する。改質器２４の運転温度を上昇させる操作は、排気ガスＥＧの熱量や加熱ヒータの電気エネルギー等のエネルギーが必要になるため、燃料電池システム１００全体としてはエネルギー損失となる。したがって、エネルギー効率の観点から、改質器２４の運転温度を上昇させる操作を実施しなくても改質器２４の反応を促進できるように、燃料流量Ｑを減らす操作を優先的に実施している。 In the present embodiment, when it is determined that the reforming performance of the reformer 24 has not been improved to the extent necessary for normal operation by the deterioration recovery process by supplying the oxidant gas OG (step S106, YES), The operation (step S407) of decreasing the fuel flow rate Q is preferentially carried out over the operation of increasing the operating temperature of the quality control device 24 (step S410). The operation of raising the operating temperature of the reformer 24 requires energy such as the heat quantity of the exhaust gas EG and the electric energy of the heater, so that the fuel cell system 100 as a whole loses energy. Therefore, from the viewpoint of energy efficiency, the fuel flow rate Q is preferentially reduced so that the reaction of the reformer 24 can be promoted without performing the operation of raising the operating temperature of the reformer 24. There is.
　ここで、改質器２４の入出口温度差ΔＴの閾値Ｔ１、Ｔ２、Ｔ４、Ｔ５は、必要量の改質ガスＲＧを燃料電池スタック１０に供給できる改質性能を維持する程度の値に予め設定しておく。本実施形態では、閾値Ｔ１、Ｔ２、Ｔ４、Ｔ５の大小関係は、Ｔ１≧Ｔ５≧Ｔ４≧Ｔ２とする。前述した第１実施形態と同様に、ステップＳ１０２の最初の劣化回復検出の判断は、最も厳しい条件として検出の感度を上げるため、Ｔ１は最も大きい値に設定することが好ましい。ステップＳ１０６の２回目の劣化回復検出の判断は、ステップＳ４０８の３回目の劣化回復検出の判断よりも条件を緩く、Ｔ４＞Ｔ２に設定しておくことが好ましい。これは、ステップＳ４０８の３回目の判断時は、改質器２４の反応を促進するように燃料流量Ｑを減らした（ステップＳ４０７）後のため、吸熱反応がより進行することによって出口温度が低下し、ステップＳ１０６の２回目の判断時に比べて入出口温度差ΔＴが大きくなるためである。また、ステップＳＳ４０８の３回目の劣化回復検出の判断の閾値Ｔ４は、ステップＳ４１１の４回目の劣化回復検出の判断の閾値Ｔ５よりも条件を緩く、Ｔ５＞Ｔ４に設定しておくことが好ましい。これは、ステップＳ４１１の４回目の判断時は、改質器２４の反応をさらに促進するように改質器２４の運転温度を上昇させた（ステップＳ４１０）後のため、吸熱反応がより進行することによって出口温度が低下し、ステップＳ４０８の３回目の判断時に比べて入出口温度差ΔＴが大きくなるためである。 Here, the threshold values T1, T2, T4, and T5 of the inlet / outlet temperature difference ΔT of the reformer 24 are set in advance to values that maintain the reforming performance capable of supplying the required amount of the reformed gas RG to the fuel cell stack 10. Set it. In the present embodiment, the magnitude relationship among the thresholds T1, T2, T4, and T5 is T1 ≧ T5 ≧ T4 ≧ T2. As in the case of the first embodiment described above, the determination of the first deterioration recovery detection in step S102 is the most severe condition, and the detection sensitivity is increased. Therefore, T1 is preferably set to the largest value. The condition of the second deterioration recovery detection in step S106 is preferably looser than that of the third deterioration recovery detection in step S408, and T4> T2 is preferably set. This is because, at the time of the third determination in step S408, the fuel flow rate Q is reduced so as to promote the reaction of the reformer 24 (step S407), and therefore the endothermic reaction further progresses and the outlet temperature decreases. However, this is because the inlet / outlet temperature difference ΔT becomes larger than that at the time of the second determination in step S106. Further, the threshold value T4 for determining the deterioration recovery detection for the third time in step SS408 is looser than the threshold value T5 for determining the deterioration recovery detection for the fourth time in step S411, and it is preferable to set T5> T4. This is because, at the time of the fourth determination in step S411, the operating temperature of the reformer 24 is raised so as to further promote the reaction of the reformer 24 (step S410), so that the endothermic reaction proceeds further. This is because the outlet temperature decreases, and the inlet / outlet temperature difference ΔT becomes larger than that at the time of the third determination in step S408.
　以上説明したように、本実施形態に係る燃料電池システムの運転条件変更手段は、劣化回復検出手段からの検出信号に基づいて、改質器２４に供給される混合ガスＭＧ（燃料）の流量Ｑを低減する流量調整部２２を有する。燃料流量Ｑを減らすことによって、触媒の表面への混合ガスＭＧの接触時間が長くなるため、改質器２４の改質性能を向上させることができる。 As described above, the operating condition changing means of the fuel cell system according to the present embodiment, based on the detection signal from the deterioration recovery detecting means, the flow rate Q of the mixed gas MG (fuel) supplied to the reformer 24. The flow rate adjusting unit 22 for reducing By reducing the fuel flow rate Q, the contact time of the mixed gas MG with the surface of the catalyst becomes longer, so that the reforming performance of the reformer 24 can be improved.
　＜第５実施形態＞
　次に、図１２～図１４を参照して、本発明の第５実施形態に係る燃料電池システム５００およびその運転方法について説明する。 <Fifth Embodiment>
Next, with reference to FIG. 12 to FIG. 14, a fuel cell system 500 according to the fifth embodiment of the present invention and an operating method thereof will be described.
　図１２は、第５実施形態に係る燃料電池システム５００を示す概略構成図である。図１３は、第５実施形態に係る燃料電池システムの運転手順を示すフローチャートである。図１４は、改質器２４の運転温度と改質ガスの水素濃度との関係を示すグラフである。 FIG. 12 is a schematic configuration diagram showing a fuel cell system 500 according to the fifth embodiment. FIG. 13 is a flowchart showing the operating procedure of the fuel cell system according to the fifth embodiment. FIG. 14 is a graph showing the relationship between the operating temperature of the reformer 24 and the hydrogen concentration of the reformed gas.
　第５実施形態に係る燃料電池システム５００は、改質ガスＲＧの水素濃度を検知する濃度センサ２７をさらに有する点で前述した第１実施形態と異なる。第５実施形態に係る燃料電池システム５００において、濃度センサ２７は、「劣化回復検出手段」に相当する。なお、前述した第１実施形態と同様の構成については、同一の符号を付してその説明を省略する。 The fuel cell system 500 according to the fifth embodiment differs from the first embodiment described above in that the fuel cell system 500 further includes a concentration sensor 27 that detects the hydrogen concentration of the reformed gas RG. In the fuel cell system 500 according to the fifth embodiment, the concentration sensor 27 corresponds to “deterioration recovery detection means”. The same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.
　濃度センサ２７は、改質器２４と燃料電池スタック１０との間、すなわち改質器２４の下流かつ燃料電池スタック１０の上流に配置される。 The concentration sensor 27 is arranged between the reformer 24 and the fuel cell stack 10, that is, downstream of the reformer 24 and upstream of the fuel cell stack 10.
　前述したようにエタノール改質反応は複数の化学反応（式（２）～（６）を参照）から成り立っており、各反応式の反応速度に基づいて、改質ガスＲＧの組成が決まる。改質ガスＲＧ中には種々のガスが含まれるが、本実施形態では濃度センサ２７は、水素濃度を検知する。なお、濃度センサ２７が検知する成分は、改質ガスＲＧ中に含まれるガスである限りにおいて水素に限定されず、例えば、一酸化炭素やメタンでもよい。感度を向上させる観点からは、改質器２４の改質性能の低下により濃度が変動しやすい成分を選択することが好ましい。水素の他に濃度が変動しやすい成分としては、例えば、一酸化炭素が挙げられる。 As mentioned above, the ethanol reforming reaction consists of multiple chemical reactions (see equations (2) to (6)), and the composition of the reformed gas RG is determined based on the reaction rate of each reaction equation. Although various gases are contained in the reformed gas RG, the concentration sensor 27 in this embodiment detects the hydrogen concentration. The component detected by the concentration sensor 27 is not limited to hydrogen as long as it is the gas contained in the reformed gas RG, and may be carbon monoxide or methane, for example. From the viewpoint of improving the sensitivity, it is preferable to select a component whose concentration is likely to change due to deterioration of the reforming performance of the reformer 24. In addition to hydrogen, carbon monoxide can be given as an example of a component whose concentration easily fluctuates.
　図１３は、第５実施形態に係る燃料電池システム５００の運転手順を示すフローチャートである。前述した第１実施形態では、改質器２４の劣化回復を検出する際に、改質器２４の入出口温度差ΔＴの値を基に改質性能の状態を判断していたのに対し、第５実施形態では、改質ガスＲＧ中の水素濃度ＣＨ２を基に改質性能の状態を判断する点で異なる。図１３に示す燃料電池システムの運転手順のステップＳ５０１、Ｓ５０２、Ｓ５０６、Ｓ５０８以外は、図２に示す前述した第１実施形態と同様のため、同一の符号を付してその説明を省略する。 FIG. 13 is a flowchart showing the operating procedure of the fuel cell system 500 according to the fifth embodiment. In the first embodiment described above, when the deterioration recovery of the reformer 24 is detected, the state of the reforming performance is determined based on the value of the inlet / outlet temperature difference ΔT of the reformer 24. The fifth embodiment is different in that the state of the reforming performance is judged based on the hydrogen concentration C H2 in the reformed gas RG. The steps other than steps S501, S502, S506, and S508 in the operation procedure of the fuel cell system shown in FIG. 13 are the same as those in the first embodiment shown in FIG.
　まず、制御部５０は、濃度センサ２７の検出信号から、改質ガスＲＧ中の水素濃度ＣＨ２を示す検出値を取得する（ステップＳ５０１）。 First, the control unit 50 acquires a detection value indicating the hydrogen concentration C H2 in the reformed gas RG from the detection signal of the concentration sensor 27 (step S501).
　次に、制御部５０は、改質ガスＲＧ中の水素濃度ＣＨ２が予め定めた閾値ＣＨ２１以下であるか否かを判断する（ステップＳ５０２）。 Next, the control unit 50 determines whether the hydrogen concentration C H2 in the reformed gas RG is less than or equal to a predetermined threshold C H2 1 (step S502).
　制御部５０は、改質ガスＲＧ中の水素濃度ＣＨ２が予め定めた閾値ＣＨ２１を越えている場合には、改質器２４の改質性能が低下していないと判断する（ステップＳ５０２、ＮＯ）。この場合、Ｓ５０１の処理に戻る。 When the hydrogen concentration C H2 in the reformed gas RG exceeds the predetermined threshold C H21 , the control unit 50 determines that the reforming performance of the reformer 24 has not deteriorated (step S502). , NO). In this case, the process returns to S501.
　一方、制御部５０は、改質ガスＲＧ中の水素濃度ＣＨ２が予め定めた閾値ＣＨ２１以下の場合には、改質器２４の改質性能が低下したと判断する（ステップＳ５０２、ＹＥＳ）。 On the other hand, when the hydrogen concentration C H2 in the reformed gas RG is less than or equal to the predetermined threshold C H21 , the control unit 50 determines that the reforming performance of the reformer 24 has deteriorated (step S502, YES). ).
　改質器２４の改質性能が低下したと判断した場合、制御部５０は、前述した第１実施形態と同様に、劣化回復処理を実行する（ステップＳ１０３～Ｓ１０５）。 When it is determined that the reforming performance of the reformer 24 has deteriorated, the control unit 50 executes the deterioration recovery process as in the first embodiment described above (steps S103 to S105).
　次に、制御部５０は、改質ガスＲＧ中の水素濃度ＣＨ２が予め定めた閾値ＣＨ２２以下になったか否かを判断する（ステップＳ５０６）。 Next, the control unit 50 determines whether or not the hydrogen concentration C H2 in the reformed gas RG has become equal to or lower than a predetermined threshold C H2 2 (step S506).
　制御部５０は、改質ガスＲＧ中の水素濃度ＣＨ２が予め定めた閾値ＣＨ２２を越えている場合には、劣化回復処理によって触媒の劣化が回復し、改質器２４の改質性能が通常運転に必要な程度まで向上したと判断し（ステップＳ５０６、ＮＯ）、操作を終了する。この場合、改質器２４の性能低下の要因は、炭素析出（コーキング）による触媒の劣化であったと判断される。 When the hydrogen concentration C H2 in the reformed gas RG exceeds a predetermined threshold C H2 2, the control unit 50 recovers the deterioration of the catalyst by the deterioration recovery process, and the reforming performance of the reformer 24. Is determined to have improved to the extent necessary for normal operation (step S506, NO), and the operation ends. In this case, it is judged that the cause of the performance deterioration of the reformer 24 is the deterioration of the catalyst due to carbon deposition (coking).
　一方、制御部５０は、改質ガスＲＧ中の水素濃度ＣＨ２が予め定めた閾値ＣＨ２２以下の場合には、劣化回復処理によっても触媒が未回復状態であり、改質器２４の改質性能が通常運転に必要な程度まで向上していないと判断する（ステップＳ５０６、ＹＥＳ）。この場合、改質器２４の性能低下の要因は、炭素析出以外の他の要因によるものと判断される。 On the other hand, when the hydrogen concentration C H2 in the reformed gas RG is equal to or lower than the predetermined threshold C H22 , the control unit 50 indicates that the catalyst is in a non-recovered state even by the deterioration recovery process, and the reformer 24 is modified. It is determined that the quality performance has not improved to the extent necessary for normal operation (step S506, YES). In this case, it is determined that the cause of the performance deterioration of the reformer 24 is due to other factors than the carbon deposition.
　改質器２４の改質性能が通常運転に必要な程度まで向上していないと判断した場合、制御部５０は、前述した第１実施形態と同様に、排気燃焼器４１からバイパス流路３２ｂへ流入する排気ガスＥＧの流量を減少させて改質器２４を加熱する（ステップＳ１０７）。 When it is determined that the reforming performance of the reformer 24 has not improved to the extent necessary for normal operation, the control unit 50 moves from the exhaust combustor 41 to the bypass flow passage 32b, as in the first embodiment described above. The reformer 24 is heated by reducing the flow rate of the inflowing exhaust gas EG (step S107).
　図１４は、改質器２４の運転温度と改質ガスＲＧ中の水素濃度ＣＨ２との関係を示すグラフである。水素濃度ＣＨ２は、運転温度が上昇するとともに増大する傾向がある。図１４に示すように改質器２４の改質性能が何らかの要因で低下した場合、通常の運転温度ＴＮから上昇させて運転温度ＴＨとする。これにより、触媒が活性化し、改質器２４の改質性能を目標改質性能もしくはそれ以上の性能まで向上させることができる。その結果、改質ガスＲＧ中の水素濃度ＣＨ２を目標水素濃度もしくはそれ以上の濃度まで向上させることができる。 FIG. 14 is a graph showing the relationship between the operating temperature of the reformer 24 and the hydrogen concentration C H2 in the reformed gas RG. The hydrogen concentration C H2 tends to increase as the operating temperature rises. As shown in FIG. 14, when the reforming performance of the reformer 24 is lowered for some reason, the normal operating temperature T N is raised to the operating temperature T H. As a result, the catalyst is activated and the reforming performance of the reformer 24 can be improved to the target reforming performance or higher. As a result, the hydrogen concentration C H2 in the reformed gas RG can be increased to the target hydrogen concentration or higher.
　再び図１３を参照して、制御部５０は、改質ガスＲＧ中の水素濃度ＣＨ２が予め定めた閾値ＣＨ２３以上になったか否かを判断する（ステップＳ５０８）。 Referring again to FIG. 13, the control unit 50, determines whether the hydrogen concentration C H2 in the reformed gas RG becomes the threshold C H2 3 above a predetermined (step S508).
　制御部５０は、改質ガスＲＧ中の水素濃度ＣＨ２が予め定めた閾値ＣＨ２３よりも低い場合には、改質器２４の改質性能が通常運転に必要な程度まで向上していないと判断する（ステップＳ５０８、ＮＯ）。ステップＳ１０７の処理へ戻り、制御部５０は、排気制御弁４２を制御して、排気燃焼器４１からバイパス流路３２ｂへ流入する排気ガスＥＧの流量を減少させる操作を繰り返す。その後、改質ガスＲＧ中の水素濃度ＣＨ２が予め定めた閾値ＣＨ２３以上（ステップＳ５０８、ＹＥＳ）となるまで排気ガスＥＧの流量を減少させる操作を繰り返す。なお、バイパス流路３２ｂへ流入する排気ガスＥＧの流量が０となった場合には、ステップＳ１０７を実行せずに操作を終了する。 When the hydrogen concentration C H2 in the reformed gas RG is lower than the predetermined threshold C H23 , the control unit 50 does not improve the reforming performance of the reformer 24 to the extent necessary for normal operation. (Step S508, NO). Returning to the processing of step S107, the control unit 50 repeats the operation of controlling the exhaust control valve 42 to reduce the flow rate of the exhaust gas EG flowing from the exhaust combustor 41 into the bypass passage 32b. After that, the operation of reducing the flow rate of the exhaust gas EG is repeated until the hydrogen concentration C H2 in the reformed gas RG becomes equal to or higher than a predetermined threshold C H23 (step S508, YES). When the flow rate of the exhaust gas EG flowing into the bypass passage 32b becomes 0, the operation is ended without executing step S107.
　制御部５０は、改質ガスＲＧ中の水素濃度ＣＨ２が予め定めた閾値ＣＨ２３以上になると、改質器２４の改質性能が通常運転に必要な程度まで向上したと判断し（ステップＳ５０８、ＹＥＳ）、操作を終了する。 When the hydrogen concentration C H2 in the reformed gas RG becomes equal to or higher than a predetermined threshold C H23 , the control unit 50 determines that the reforming performance of the reformer 24 has been improved to the extent necessary for normal operation (step). S508, YES), and the operation ends.
　予め設定する改質ガスＲＧ中の水素濃度ＣＨ２の閾値ＣＨ２１、ＣＨ２２、ＣＨ２３は、ＣＨ２１≧ＣＨ２３≧ＣＨ２２とする。ステップＳ５０２の最初の劣化回復検出の判断は、最も厳しい条件として検出の感度を上げるため、ＣＨ２１は最も大きい値に設定することが好ましい。また、ステップＳ５０６の２回目の劣化回復検出の判断は、ステップＳ５０８の３回目の劣化回復検出の判断よりも条件を緩く、ＣＨ２３＞ＣＨ２２に設定しておくことが好ましい。これは、前述した第１実施形態と同様の理由によるものである。なお、ＣＨ２１、ＣＨ２２、ＣＨ２３は、同一の値を用いてもよい。 The thresholds C H2 1, C H2 2, and C H2 3 of the hydrogen concentration C H2 in the reformed gas RG set in advance are C H2 1 ≧ C H2 3 ≧ C H2 2. The determination of the first deterioration recovery detection in step S502 is set to the largest value for C H2 1 in order to raise the detection sensitivity as the most severe condition. The condition for the second deterioration recovery detection in step S506 is preferably looser than that for the third deterioration recovery detection in step S508, and it is preferable to set C H2 3> C H2 2. This is for the same reason as in the first embodiment described above. The same values may be used for C H2 1, C H2 2, and C H2 3.
　以上説明したように、本実施形態に係る燃料電池システム５００の劣化回復検出手段は、改質器２４によって改質された改質ガスＲＧの組成に基づいて触媒の回復状態を検出する濃度センサ２７を有する。改質ガスＲＧの組成を直接的に検出することによって、改質器２４の改質性能の低下を確実に検知することができる。これにより、改質ガスＲＧの組成の悪化による燃料電池スタック１０の出力低下を抑制することができる。 As described above, the deterioration recovery detecting unit of the fuel cell system 500 according to the present embodiment detects the recovery state of the catalyst based on the composition of the reformed gas RG reformed by the reformer 24. Have. By directly detecting the composition of the reformed gas RG, it is possible to reliably detect the deterioration of the reforming performance of the reformer 24. This can prevent the output of the fuel cell stack 10 from decreasing due to the deterioration of the composition of the reformed gas RG.
　以上、実施形態を通じて本発明に係る燃料電池システムおよび燃料電池システムの運転方法を説明したが、本発明は実施形態において説明した内容のみに限定されることはなく、特許請求の範囲の記載に基づいて適宜変更することが可能である。 The fuel cell system and the method of operating the fuel cell system according to the present invention have been described above through the embodiments. However, the present invention is not limited to the contents described in the embodiments, and is based on the claims. Can be changed as appropriate.
　例えば、劣化回復検出手段は、改質器の入出口温度差を検出する温度センサ、燃料電池スタックの出力を検出する出力センサまたは改質ガスの組成を検出する濃度センサによって構成される例について説明したが、触媒の回復状態を検出できる限りにおいて特に限定されず、上記以外の構成を用いてもよいし、上記の複数の構成を適宜組み合わせて用いてもよい。 For example, an explanation will be given of an example in which the deterioration recovery detection means is composed of a temperature sensor for detecting the inlet / outlet temperature difference of the reformer, an output sensor for detecting the output of the fuel cell stack, or a concentration sensor for detecting the composition of the reformed gas. However, it is not particularly limited as long as the recovery state of the catalyst can be detected, and a configuration other than the above may be used, or a plurality of the above configurations may be appropriately combined and used.
　また、運転条件変更手段は、改質器を加熱する加熱部または改質器に供給される燃料の流量を低減する流量調整部によって構成される例について説明したが、改質器の反応を促進するように運転条件を変更できる限りにおいて特に限定されず、上記以外の構成を用いてもよいし、上記の複数の構成を適宜組み合わせて用いてもよい。 Further, the operation condition changing means has been described with respect to the example in which it is constituted by the heating part for heating the reformer or the flow rate adjusting part for reducing the flow rate of the fuel supplied to the reformer, but the reaction of the reformer is promoted. There is no particular limitation as long as the operating conditions can be changed as described above, and a configuration other than the above may be used, or a plurality of the above configurations may be appropriately combined and used.
　また、第１実施形態の燃料電池システムの運転方法において、バイパス流路３２ｂへ流入する排気ガスＥＧの流量が０となった場合に、加熱ヒータを用いて改質器をさらに加熱してもよいし、燃料流量を減らす操作を実施してもよい。 In the method for operating the fuel cell system according to the first embodiment, the reformer may be further heated by using the heater when the flow rate of the exhaust gas EG flowing into the bypass passage 32b becomes 0. However, an operation of reducing the fuel flow rate may be performed.
　また、第４実施形態の燃料電池システムの運転方法において、運転条件変更手段は、改質器の運転温度を上昇させる操作よりも燃料流量を減らす操作を優先的に実施するとしたが、これに限定されずに、燃料流量を減らす操作よりも改質器の運転温度を上昇させる操作を優先的に実施してもよいし、燃料流量を減らす操作と改質器の運転温度を上昇させる操作を同時に実施してもよい。 Further, in the operating method of the fuel cell system according to the fourth embodiment, the operating condition changing means preferentially performs the operation of reducing the fuel flow rate over the operation of increasing the operating temperature of the reformer, but is not limited to this. Instead, the operation to raise the operating temperature of the reformer may be prioritized over the operation to reduce the fuel flow rate, or the operation to reduce the fuel flow rate and the operation to raise the operating temperature of the reformer may be performed at the same time. You may implement.
　また、燃料および水を混合した水含有燃料を用いて改質ガスを生成する形態に限定されず、燃料用タンクと貯水用タンクをそれぞれ個別に設けてもよい。この場合、燃料タンクおよび貯水タンクから蒸発器への供給量をそれぞれ調整することによって混合ガスの組成を容易に調整することができる。 Also, it is not limited to the mode in which the reformed gas is generated using the water-containing fuel in which the fuel and the water are mixed, and the fuel tank and the water storage tank may be provided separately. In this case, the composition of the mixed gas can be easily adjusted by adjusting the supply amounts from the fuel tank and the water storage tank to the evaporator.
　また、前述した実施形態では、燃料電池スタックは、固体酸化物形燃料電池（ＳＯＦＣ）に適用されるとして説明したが、これに限定されず、例えば、固体高分子膜形燃料電池（ＰＥＭＦＣ：Ｐｏｌｙｍｅｒ　Ｅｌｅｃｔｒｏｌｙｔｅ　Ｍｅｍｂｒａｎｅ　Ｆｕｅｌ　Ｃｅｌｌ）、リン酸形燃料電池（ＰＡＦＣ：Ｐｈｏｓｐｈｏｒｉｃ　Ａｃｉｄ　Ｆｕｅｌ　Ｃｅｌｌ）または溶融炭酸塩形燃料電池（ＭＣＦＣ：Ｍｏｌｔｅｎ　Ｃａｒｂｏｎａｔｅ　Ｆｕｅｌ　Ｃｅｌｌ）に適用してもよい。 Further, in the above-described embodiment, the fuel cell stack is described as being applied to a solid oxide fuel cell (SOFC), but the present invention is not limited to this, and for example, a solid polymer membrane fuel cell (PEMFC: Polymer). It may be applied to an Electrolyte Membrane Fuel Cell, a phosphoric acid fuel cell (PAFC: Phosphoric Acid Fuel Cell) or a molten carbonate fuel cell (MCFC: Molten Carbone Fuel Cell).
１０　　　燃料電池スタック、
２１　　　燃料タンク、
２２　　　流量調整部、
２３　　　蒸発器、
２４　　　改質器、
２５　　　温度センサ（劣化回復検出手段）、
２５ａ　　入口温度センサ、
２５ｂ　　出口温度センサ、
２６　　　加熱ヒータ（運転条件変更手段）、
２７　　　濃度センサ（劣化回復検出手段）、
３１　　　酸化剤供給部（劣化回復手段）、
３２　　　熱交換器、
３２ａ　　メイン流路、
３２ｂ　　バイパス流路、
４１　　　排気燃焼器（運転条件変更手段）、
４２　　　排気制御弁（運転条件変更手段）、
４３　　　酸化剤ガス制御弁、
５０　　　制御部、
５４　　　出力センサ（劣化回復検出手段）、
１００、２００、３００、５００　燃料電池システム、
ＭＷ　　　水含有燃料（燃料）、
ＭＧ　　　混合ガス、
ＲＧ　　　改質ガス、
ＯＧ　　　酸化剤ガス、
ＥＧ　　　排気ガス。 10 Fuel cell stack,
21 fuel tank,
22 Flow rate adjustment unit,
23 Evaporator,
24 reformer,
25 Temperature sensor (deterioration recovery detection means),
25a inlet temperature sensor,
25b outlet temperature sensor,
26 heater (operating condition changing means),
27 concentration sensor (deterioration recovery detection means),
31 oxidant supply unit (deterioration recovery means),
32 heat exchanger,
32a main flow path,
32b bypass flow path,
41 Exhaust combustor (means for changing operating conditions),
42 Exhaust control valve (operating condition changing means),
43 Oxidant gas control valve,
50 control unit,
54 output sensor (deterioration recovery detection means),
100, 200, 300, 500 Fuel cell system,
MW water-containing fuel (fuel),
MG mixed gas,
RG reformed gas,
OG oxidant gas,
EG Exhaust gas.

Claims (7)

  1. 　燃料を触媒を備えた改質器で改質して燃料電池スタックに供給して発電する燃料電池システムにおいて、
    　前記改質器に酸化剤ガスを供給して前記改質器の触媒の劣化を回復する劣化回復手段と、
    　前記劣化回復手段による前記触媒の回復状態を検出する劣化回復検出手段と、
    　前記触媒が未回復状態であることを示す前記劣化回復検出手段からの検出信号に基づいて、前記改質器の反応を促進するように運転条件を変更する運転条件変更手段と、を有する、燃料電池システム。     In a fuel cell system that reforms fuel with a reformer equipped with a catalyst and supplies it to a fuel cell stack to generate electricity,
    Deterioration recovery means for supplying an oxidant gas to the reformer to recover the deterioration of the catalyst of the reformer,
    Deterioration recovery detection means for detecting the recovery state of the catalyst by the deterioration recovery means,
    An operating condition changing means for changing the operating condition so as to promote the reaction of the reformer, based on a detection signal from the deterioration recovery detecting means indicating that the catalyst is in an unrecovered state, Battery system.
  2. 　前記運転条件変更手段は、前記劣化回復検出手段からの前記検出信号に基づいて、前記改質器を加熱する加熱部を有する、請求項１に記載の燃料電池システム。 The fuel cell system according to claim 1, wherein the operating condition changing unit has a heating unit that heats the reformer based on the detection signal from the deterioration recovery detecting unit.
  3. 　前記運転条件変更手段は、前記劣化回復検出手段からの前記検出信号に基づいて、前記改質器に供給される前記燃料の流量を低減する流量調整部を有する、請求項１または請求項２に記載の燃料電池システム。 The operating condition changing means includes a flow rate adjusting section that reduces a flow rate of the fuel supplied to the reformer based on the detection signal from the deterioration recovery detecting means. The fuel cell system described.
  4. 　前記劣化回復検出手段は、前記改質器の入口温度と出口温度との差に基づいて前記触媒の回復状態を検出する温度センサを有する、請求項１～３のいずれか一項に記載の燃料電池システム。 4. The fuel according to claim 1, wherein the deterioration recovery detection unit has a temperature sensor that detects a recovery state of the catalyst based on a difference between an inlet temperature and an outlet temperature of the reformer. Battery system.
  5. 　前記劣化回復検出手段は、前記燃料電池スタックの出力に基づいて前記触媒の回復状態を検出する出力センサを有する、請求項１～４のいずれか一項に記載の燃料電池システム。 The fuel cell system according to any one of claims 1 to 4, wherein the deterioration recovery detection means has an output sensor that detects a recovery state of the catalyst based on an output of the fuel cell stack.
  6. 　前記劣化回復検出手段は、前記改質器によって改質された改質ガスの組成に基づいて前記触媒の回復状態を検出する濃度センサを有する、請求項１～５のいずれか一項に記載の燃料電池システム。 6. The deterioration recovery detection unit according to claim 1, further comprising a concentration sensor that detects a recovery state of the catalyst based on the composition of the reformed gas reformed by the reformer. Fuel cell system.
  7. 　燃料を改質する改質器の触媒の劣化が検出された場合に、前記改質器に酸化剤ガスを供給し、
    　前記酸化剤ガスが供給された前記改質器の前記触媒の回復状態を検出し、
    　前記触媒が未回復状態の場合は前記改質器の反応を促進するように運転条件を変更する、燃料電池システムの運転方法。     When deterioration of the catalyst of the reformer that reforms the fuel is detected, oxidant gas is supplied to the reformer,
    Detecting the recovery state of the catalyst of the reformer supplied with the oxidizing gas,
    A method of operating a fuel cell system, wherein operating conditions are changed so as to accelerate the reaction of the reformer when the catalyst is in a non-recovered state.
PCT/JP2018/039012 2018-10-19 2018-10-19 Fuel cell system and method for operating fuel cell system WO2020079833A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005340075A (en) * 2004-05-28 2005-12-08 Kyocera Corp Operation stopping method of fuel cell
JP2006315921A (en) * 2005-05-13 2006-11-24 Toyota Motor Corp Hydrogen production system and fuel cell system
JP2012038689A (en) * 2010-08-11 2012-02-23 Ngk Spark Plug Co Ltd Operation method of fuel cell
JP2016192334A (en) * 2015-03-31 2016-11-10 株式会社デンソー Fuel battery system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005340075A (en) * 2004-05-28 2005-12-08 Kyocera Corp Operation stopping method of fuel cell
JP2006315921A (en) * 2005-05-13 2006-11-24 Toyota Motor Corp Hydrogen production system and fuel cell system
JP2012038689A (en) * 2010-08-11 2012-02-23 Ngk Spark Plug Co Ltd Operation method of fuel cell
JP2016192334A (en) * 2015-03-31 2016-11-10 株式会社デンソー Fuel battery system

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