JP4789505B2 - Fuel cell system - Google Patents

Description

  In the warm-up mode in which the reformer is warmed up, the reformer is directly connected to the combustion unit without passing through the fuel electrode of the fuel cell, and the warm-up of the reformer is completed and the fuel cell generates power. The power generation mode relates to a fuel cell system in which a reforming unit communicates with a combustion unit via a fuel electrode of a fuel cell.

  As one type of this fuel cell system, one disclosed in Patent Document 1 “Method for Stopping Fuel Cell System and Fuel Cell System Using This Method” is known. As shown in FIG. 1 of Patent Document 1, the fuel cell system includes a fuel cell 10 that generates electric power using a fuel gas and an oxidant gas supplied to a fuel electrode and an oxidant electrode, a reforming fuel, and a modified fuel cell. The reforming part 21 which produces | generates the fuel gas containing hydrogen by reforming the supplied reforming fuel with the reforming catalyst by supplying quality water, and combustible fuel is supplied, and the combustible fuel is combusted. A reformer (reformer) 20 having a combustion section 21 d that heats the reforming section 21 with the combustion gas, and the fuel gas generated in the reforming section 21 burns via the fuel electrode of the fuel cell 10. The first flow path (the first reformed gas supply pipe 71 and the first offgas supply pipe 72) for supplying to the section 21d and the fuel gas generated by the reforming section 21 bypassing the fuel electrode of the fuel cell 10 and the combustion section The second flow path (first modified) supplied to 21d A gas supply pipe 71, a second reformed gas supply pipe 77 and a first off-gas supply pipe 72) and a communication blocking means (first reformed gas valve 73 and first and second flow paths) for switching the first and second flow paths between a communication state and a cutoff state, respectively. A second reformed gas valve 78), and the communication shut-off means sets the first and second flow paths in the shut-off state and the communication state in the warm-up mode for warming up the reformer 20, respectively. As a power generation mode in which the warm-up of the device 20 is completed and the fuel cell generates power, it is well known that the first and second flow paths are in a communication state and a cutoff state, respectively.

  In such a fuel cell system, a process of purging the reforming fuel and reformed gas remaining in the reformer 20 is performed, and then the operation is stopped. As this sweeping process, a method of purging with an inert gas (for example, nitrogen gas), a method of purging with water vapor, and then purging the water vapor with air are generally known. Thereafter, when the operation of the fuel cell system is started again, the reformer 20 is warmed up, and when the warm-up is completed, power generation of the fuel cell 10 is started. When shifting from the warm-up mode to the power generation mode, the second flow path, which has been in communication until then, is shut off, and the first flow path that has been in shut-off is in communication with the first flow path. Residual gases such as inert gas and air that flow into the combustion part flow into the combustion part all at once, so that the combustion state may fluctuate and the combustion part may misfire.

Moreover, what is shown by patent document 2 "the fuel cell power generation system using the hydrogen production apparatus which has a combustor" is known. This fuel cell power generation system stably controls a combustor of a hydrogen production apparatus even in a situation where there are many load fluctuations such as a home-use distributed power supply. This fuel cell power generation system refers to the detection signal of the combustion state detection device that detects the combustion state of the combustor 51, and if the combustion state leads to misfire, at least the control current amount by the power conversion means 31 is predetermined. It is designed to decrease in range. Further, at least one of the control current amount by the power conversion means 31 and the supply air amount by the air supply device 71 is limited only during a timer count time determined in advance based on each start command of system start, stop, and load switching. It comes to control. In this case, the control is switched so as to change in a predetermined sequence in preference to other feedback control.
JP 2004-152540 A (page 5-10, FIG. 1-5) Japanese Unexamined Patent Publication No. 2004-178862 (page 3-20, FIG. 1-10)

  In the fuel cell power generation system described in Patent Document 2 described above, there is no detailed description of how to deal with misfire in the combustion section immediately after the transition from the warm-up mode in which the combustion state changes most rapidly to the power generation mode. Further, since the feedback control is stopped and the sequence control is performed during the transition period, there is a problem that the robustness is lowered. Also, since feedback control is performed again after the transition period, the inheritance of control when switching between feedback control and sequence control has also been a problem. In addition, when there is no power generation load immediately after the start of power generation and the fuel cell is configured to generate power with the minimum power generation output (minimum power generation current), in this case as well, as a load to reduce the control power generation amount Since the secondary battery 41 is provided, there is a problem that the fuel cell system is increased in size and cost.

  The present invention has been made to solve the above-described problems. When shifting from the warm-up mode to the power generation mode, the robustness decreases, the control inheritance at the time of switching decreases, the size increases, and the cost increases. It aims at providing the fuel cell system which prevents that a combustion part fluctuates and a combustion part misfires without inviting it.

In order to solve the above-mentioned problem, the structural feature of the invention according to claim 1 is that a fuel cell that generates power by using a fuel gas and an oxidant gas respectively supplied to a fuel electrode and an oxidant electrode, a reforming fuel, and Reforming water is supplied, reforming the supplied reforming fuel with a reforming catalyst to generate a fuel gas containing hydrogen, and combustible fuel is supplied to burn the combustible fuel. A reformer provided with a combustion section for heating the reforming section with the combustion gas, a first flow path for supplying the fuel gas generated in the reforming section to the combustion section via the fuel electrode of the fuel cell, A second flow path for supplying the fuel gas generated in the reforming section to the combustion section by bypassing the fuel electrode of the fuel cell, and a communication blocking means for switching the first and second flow paths to a communication state and a block state, respectively. The communication cutoff means warms up the reformer. The that warm-up mode, respectively blocked state and the communication state of the first and second flow paths, the first flow path and the communicating state after the time when the reformer warm-up is completed, communication state of the first flow path A fuel cell system that shuts off the second flow path when a first predetermined time elapses from the time when the reforming fuel is supplied; a reforming fuel supply means that supplies reforming fuel to the reforming unit; Hydrogen utilization rate representing the ratio of the amount of hydrogen consumed in the fuel cell to the amount of hydrogen in the fuel gas supplied to the fuel cell from the time when the flow path is in the communication state until the second predetermined time elapses Is set to the first set value, and thereafter, the hydrogen use rate is set by the hydrogen use rate setting means for setting the hydrogen use rate to the second set value larger than the first set value, and the power generation output of the fuel cell and the hydrogen use rate setting means. Supply of reforming fuel to be supplied to the reforming unit based on the hydrogen utilization rate A reforming fuel supply amount deriving unit for deriving the amount, and a reforming fuel supply control unit for controlling the reforming fuel supply unit so as to obtain the supply amount derived by the reforming fuel supply amount deriving unit; A combustion fuel supply means for supplying combustion fuel to the combustion section, a combustion state detection means for detecting the combustion state of the combustion section, and a target combustion state of the combustion section until the warm-up of the reformer is completed. 1 target combustion state is set, and the target combustion state setting for setting the target combustion state of the combustion section to the second target combustion state that is on the misfire state side from the first target combustion state after the time when the warming-up of the reformer is completed And the combustion fuel supply means are feedback controlled to adjust the combustion state of the combustion section so that the target combustion state set by the target combustion state setting means is achieved, and the rotation speed of the combustion fuel supply means is the lower limit rotation. Not to be smaller than the number And a combustion fuel supply control means for controlling the combustion fuel supply means is a diaphragm pump, and a second predetermined time elapses from the time when the first flow path is brought into communication. Until the lower limit rotational speed of the combustion fuel supply means is set to the first rotational speed, and thereafter, the lower limit rotational speed setting means for setting the lower limit rotational speed to a second rotational speed smaller than the first rotational speed. The fuel supply control means for combustion is to use the lower limit rotational speed set by the lower limit rotational speed setting means .

The feature in construction of the invention according to claim 2, Oite to claim 1, the connection cutoff means includes a first valve for opening and closing the same first passage provided in the first flow path, the second A second valve that is provided in the flow path and opens and closes the second flow path.

In the invention according to claim 1 configured as described above, when shifting from the warm-up mode to the power generation mode, from the time when the first flow path is in the communication state to the time when the first predetermined time elapses. Since the residual gas remaining in the first flow path is supplied to the combustion section together with the fuel gas from the reforming section through the second flow path, the combustible gas is generated by the residual gas as in the conventional case. By being diluted, it is possible to prevent the combustion state from fluctuating and the combustion part from misfiring.
Further, the hydrogen utilization rate setting means consumes the fuel cell with respect to the amount of hydrogen in the fuel gas supplied from the time when the first flow path is in the communication state until the second predetermined time elapses. The hydrogen utilization rate representing the ratio of the hydrogen amount thus set is set to the first set value, and thereafter, the hydrogen utilization rate is set to the second set value larger than the first set value, and the reforming fuel supply amount deriving means The amount of reforming fuel supplied to the reforming unit is derived based on the power generation output of the fuel cell and the hydrogen utilization rate set by the hydrogen utilization rate setting means, and the reforming fuel supply control means The reforming fuel supply unit is controlled so as to be the supply amount derived by the quality fuel supply amount deriving unit. Thereby, the supply amount of the reforming fuel increases by setting the hydrogen utilization rate lower than that in the power generation mode until the second predetermined time elapses from the time when the first flow path is in the communication state. Increasing the supply amount of the combustible gas supplied to the combustion unit can prevent the combustion unit from misfiring.
Further, the target combustion state setting means sets the target combustion state of the combustion section to the first target combustion state until the reformer warm-up is completed, and after the time when the reformer warm-up is completed, the combustion section The target combustion state is set to the second target combustion state, which is the misfire state side from the first target combustion state, and the combustion fuel supply control means performs feedback control on the combustion fuel supply means and is set by the target combustion state setting means The combustion state of the combustion section is adjusted so that the target combustion state is achieved, and control is performed so that the rotational speed of the combustion fuel supply means does not become lower than the lower limit rotational speed. As a result, when shifting from the warm-up mode to the power generation mode, it is possible to prevent the combustion portion from being misfired due to fluctuations in the combustion state without causing a decrease in robustness and a decrease in control inheritance at the time of switching. Can do.
Further, when a diaphragm type pump is used as the combustion fuel supply means, the combustion fuel supply is performed until the second predetermined time elapses after the lower limit rotation speed setting means sets the first flow path to the communication state. The lower limit rotational speed of the means is set to the first rotational speed, and thereafter the lower limit rotational speed is set to the second rotational speed smaller than the first rotational speed, and the combustion fuel supply control means is set by the lower limit rotational speed setting means. Use the specified lower speed limit. Thereby, it is possible to prevent pulsation due to the driving of the diaphragm pump and to control the supply amount of the combustion fuel with high accuracy.

In the invention according to Claim 2 as constructed above, in the invention according to claim 1, the connection cutoff means comprises a first valve provided in the first flow path to open and close the same first passage, first Since the second valve is provided in two flow paths and opens and closes the second flow path, it is possible to increase the size without changing the existing structure or adding another member. It is possible to prevent the combustion part from being misfired without increasing the cost.

  Hereinafter, an embodiment of a fuel cell system according to the present invention will be described. FIG. 1 is a schematic diagram showing an outline of this fuel cell system. As shown in FIG. 1, this fuel cell system includes a fuel cell 10 and a steam reforming reformer 20 that generates a reformed gas that is a fuel gas containing hydrogen gas necessary for the fuel cell 10. . The fuel cell 10 includes a fuel electrode 11 and an air electrode 12 that is an oxidant electrode, and reformed gas supplied to the fuel electrode 11 and air (cathode air) that is an oxidant gas supplied to the air electrode 12. To generate electricity. Note that air-enriched gas may be supplied instead of air.

  An inverter (power converter) 13 is connected to the fuel cell 10. The inverter 13 converts the power generation output (power generation current) of the fuel cell 10 into AC power (AC current) and supplies it to the power usage place 15 as a user destination via the power transmission line 14. A power consuming device 15a, which is an electric appliance such as a light, an iron, a television, a washing machine, an electric kotatsu, an electric carpet, an air conditioner, and a refrigerator, is installed in the power usage place 15, and the AC power supplied from the inverter 13 It is supplied to the power consuming device 15a as needed. The power line 14 connecting the inverter 13 and the power use place 15 is also connected to the grid power source 16 of the power company (system interconnection), and the total power consumption of the power consuming device 15a is determined from the power generation output of the fuel cell 10. Is exceeded, the insufficient power is received from the system power supply 16 and compensated. The inverter 13 also has a function of measuring the direct current value input from the fuel cell 10 (output current detection means for detecting the output current of the fuel cell 10), and outputs a measurement signal to the control device 30. It has become. The wattmeter 15b is user load power detection means for detecting user load power (user power consumption), detects the total power consumption of all the power consumption devices 15a used in the power usage place 15, and controls the control device 30. To output.

  The reformer 20 includes a reforming unit 21, a cooling unit 22, a carbon monoxide shift reaction unit (hereinafter referred to as a CO shift unit) 23, a carbon monoxide selective oxidation unit (hereinafter referred to as a CO selective oxidation unit) 24, a combustion. The unit 25 and the evaporation unit 26 are included.

  The reforming unit 21 generates and derives a reformed gas from a mixed gas of fuel and water vapor supplied from the outside. Examples of the fuel include natural gas, LPG, kerosene, gasoline, methanol, and the like. In the present embodiment, description will be made on natural gas. The reforming portion 21 is formed in a bottomed cylindrical shape, and is formed of an outer flow passage 21a1 and an annular inner flow passage 21a2 each formed in an annular shape. The return channel 21a is provided.

  The return channel 21 a of the reforming unit 21 is filled with a catalyst 21 b (for example, a Ru or Ni-based catalyst), and is introduced from the reforming fuel introduced from the fuel supply pipe 41 and the water vapor supply pipe 52. The mixed gas with the steam is reacted and reformed by the catalyst 21b to generate hydrogen gas and carbon monoxide gas (so-called steam reforming reaction). At the same time, a so-called carbon monoxide shift reaction occurs in which carbon monoxide generated in the steam reforming reaction reacts with steam to transform into hydrogen gas and carbon dioxide. These generated gases (so-called reformed gas) are led to a cooling unit (heat exchange unit) 22. The steam reforming reaction is an endothermic reaction, and the carbon monoxide shift reaction is an exothermic reaction. The reforming unit 21 is provided with a temperature sensor 21c on the inner side of the inner wall directly hit by the combustion gas ejected from the combustion unit 25. This temperature sensor 21c is a combustion part temperature detection means for detecting the combustion temperature of the combustion part 25, and can also recognize the combustion state from the combustion temperature, so the combustion part combustion state for detecting the combustion state of the combustion part 25 It is a detection means. The detection result of the temperature sensor 21 c is output to the control device 30.

  The cooling unit 22 is a heat exchanger in which heat exchange is performed between the reformed gas derived from the reforming unit 21 and a mixed gas of reforming fuel and reforming water (steam). The temperature of the reformed gas is lowered by a low-temperature mixed gas and led out to the CO shift unit 23, and the mixed gas is heated by the reformed gas and led out to the reforming unit 21. Specifically, a fuel supply pipe 41 connected to a fuel supply source Sf (for example, a city gas pipe) is connected to the cooling unit 22, and reforming fuel is supplied from the fuel supply source Sf. The fuel supply pipe 41 is provided with a first fuel valve 42, a reforming fuel pump 43, a desulfurizer 44, and a second fuel valve 45 in order from the upstream. The first and second fuel valves 42 and 45 open and close the fuel supply pipe 41 according to commands from the control device 30. The reforming fuel pump 43 sucks the reforming fuel supplied from the fuel supply source Sf and discharges it to the reforming unit 21, and adjusts the reforming fuel supply amount according to a command from the control device 30. It is. The desulfurizer 44 removes sulfur (for example, sulfur compounds) in the reforming fuel. Thereby, the sulfur content is removed from the reforming fuel and supplied to the reforming unit 21.

  Further, a steam supply pipe 52 connected to the evaporation section 26 is connected between the second fuel valve 45 of the fuel supply pipe 41 and the cooling section 22, and the steam supplied from the evaporation section 26 becomes reforming fuel. It is mixed and supplied to the reforming unit 21 through the cooling unit 22. A water supply pipe 51 connected to a water tank Sw that is a reforming water supply source is connected to the evaporation unit 26. The water supply pipe 51 is provided with a water pump 53 and a water valve 54 in order from the upstream. The water pump 53 sucks the reformed water supplied from the water tank Sw and discharges it to the evaporation unit 26, and adjusts the reformed water supply amount according to a command from the control device 30. The water valve 54 opens and closes the water supply pipe 51 according to a command from the control device 30.

  The evaporation section 26 heats and boiles the reformed water to generate water vapor and supplies the steam to the reforming section 21 via the cooling section 22. The evaporation section 26 is formed in a cylindrical shape and has a first shape of the combustion gas channel 27. 2 The outer peripheral flow path 27c is provided so as to cover the outer peripheral wall. The evaporating unit 26 has a water supply pipe 51 and a water vapor supply pipe 52 connected to a lower side wall surface and an upper side wall surface, respectively. Thus, the water is supplied to the water vapor supply pipe 52. As a result, water (for example, 20 ° C.) that was at a low temperature at the time of introduction is heat-exchanged with the combustion gas flowing through the second outer peripheral flow path 27c to be heated to a boiling state (100 ° C. or higher) and is derived at that temperature. It has become so. The evaporation unit 26 is provided with a temperature sensor 26 a that detects the internal temperature, and a detection signal is output to the control device 30.

  The CO shift unit 23 is a unit that reduces carbon monoxide in the reformed gas supplied from the reforming unit 21 through the cooling unit 22, that is, a carbon monoxide reducing unit. The CO shift unit 23 includes a cylindrical casing 23a and an inner cylinder 23b arranged coaxially in the casing 23a. The inner cylinder 23b has an upper end connected to the inner peripheral end of an annular support member 23c whose outer peripheral end is connected to the inner peripheral surface of the housing 23a. A reformed gas inlet 23a1 is provided on the upper surface of the housing 23a, and the other end of a connecting pipe 89 having one end connected to the CO selective oxidation unit 24 is connected to a side surface of the housing 23a. A catalyst 23d (for example, a Cu—Zn-based catalyst) is filled in the inner cylinder 23b of the CO shift portion 23 and between the inner cylinder 23b and the housing 23a. The CO shift unit 23 is provided with a temperature sensor 23e for detecting the temperature in the CO shift unit 23, for example, the temperature in the vicinity of the reformed gas inlet of the CO shift unit 23, and the detection signal is sent to the control device 30. It is output.

  In the CO shift unit 23 configured in this way, the reformed gas led out from the cooling unit 22 passes through the reformed gas inlet 23a1 and through the catalyst 23d in the inner cylinder 23b, and is turned back to the inner cylinder 23b. And is led to the CO selective oxidation unit 24 through the inside of the catalyst 23d between the casing 23a. At this time, a so-called carbon monoxide shift reaction occurs in which carbon monoxide and water vapor contained in the introduced reformed gas react with the catalyst 23d to be converted into hydrogen gas and carbon dioxide gas. This carbon monoxide shift reaction is an exothermic reaction.

  The CO selective oxidation unit 24 further reduces the carbon monoxide in the reformed gas supplied from the CO shift unit 23 and supplies it to the fuel cell 10, that is, a carbon monoxide reduction unit, and is formed in a cylindrical shape. Then, the outer peripheral wall of the evaporation part 26 is covered and provided. In this CO selective oxidation unit 24, a connecting pipe 89 and a reformed gas supply pipe 71 are respectively connected to a lower side wall surface and an upper side wall surface, and a catalyst 24a (for example, a Ru or Pt catalyst) is filled therein. The reformed gas introduced through the connection pipe 89 flows through the CO selective oxidation unit 24 and is led out from the reformed gas supply pipe 71. Further, a temperature sensor 24 b for detecting the temperature of the catalyst 24 a is provided in the CO selective oxidation unit 24, and a detection signal thereof is output to the control device 30.

  Further, the reforming gas supplied to the CO selective oxidation unit 24 is mixed with oxidizing air. That is, the connection pipe 89 is connected to the oxidation air supply pipe 61 connected to the air supply source Sa, and is supplied with oxidation air from the air supply source Sa (for example, the atmosphere). The oxidation air supply pipe 61 is provided with a filter 62, an air pump 63, and an air valve 64 in order from the upstream. The filter 62 filters air. The air pump 63 sucks in air supplied from the air supply source Sa and discharges it to the CO selective oxidation unit 24, and adjusts the air supply amount in accordance with a command from the control device 30. The air valve 64 opens and closes the oxidizing air supply pipe 61 according to a command from the control device 30. Thus, the oxidizing air is mixed with the reformed gas from the CO shift unit 23 and supplied to the CO selective oxidation unit 24.

  Therefore, carbon monoxide in the reformed gas introduced into the CO selective oxidation unit 24 reacts with oxygen in the oxidizing air to become carbon dioxide. This reaction is an exothermic reaction and is promoted by the catalyst 24a. Thereby, the reformed gas is derived by further reducing the carbon monoxide concentration (10 ppm or less) by the oxidation reaction, and is supplied to the fuel electrode 11 of the fuel cell 10.

  The combustion unit 25 is supplied with combustible fuel, burns the combustible fuel, and heats the reforming unit 21 with the combustion gas, that is, heats the reforming unit 21 and supplies heat necessary for the steam reforming reaction. It generates combustion gas for the purpose. The combustion section 25 is arranged with a lower end inserted into the inner peripheral wall of the reforming section 21 with a space. The combustion gas is folded back from the inner peripheral flow path 27a along the inner peripheral wall of the reforming section 21, the first outer peripheral flow path 27b along the outer peripheral wall of the reforming section 21 and the first outer peripheral flow path 27b. Then, it flows through the combustion gas flow path 27 constituted by the second outer peripheral flow path 27 c along the heat insulating portion 28, and is exhausted as combustion exhaust gas through the exhaust pipe 81. The combustion gas passage 27 is covered with a heat insulating portion 28, and the heat of the combustion gas flowing through the inner peripheral flow passage 27a and the first outer peripheral flow passage 27b is suppressed from radiating to the outside by the heat insulating portion 28, so that the reforming portion. The heat of the combustion gas flowing through the second outer circumferential flow path 27c is effectively utilized for heating the evaporation section 26 because heat dissipation to the first outer circumferential flow path 27b is suppressed by the heat insulating section 28.

  A combustion fuel supply pipe 47 branched from the fuel supply pipe 41 is connected to the combustion section 25 upstream of the reforming fuel pump 43 so that combustion fuel is supplied. The combustion fuel supply pipe 47 is provided with a combustion fuel pump 48. The combustion fuel pump 48 is a diaphragm pump, and is a combustion fuel supply unit that sucks the combustion fuel supplied from the fuel supply source Sf and discharges it to the combustion unit 25, and burns in accordance with a command from the control device 30. The fuel supply amount is adjusted. The combustion section 25 is connected to the other end of an off-gas supply pipe 72 whose one end is connected to the outlet of the fuel electrode 11, and the reformed gas from the reformer 20 is supplied during the start-up operation of the fuel cell 10. Anode off-gas supplied through the reformed gas supply pipe 71, the bypass pipe 73 and the off-gas supply pipe 72 and discharged from the fuel cell 10 during steady operation of the fuel cell 10 (containing unused hydrogen in the fuel electrode 11). Reformed gas) is supplied through an off-gas supply pipe 72. For example, the above-mentioned combustion fuel, reformed gas, and anode off gas are combustible fuels.

  Further, a combustion air supply pipe 65 branched from the oxidation air supply pipe 61 is connected to the combustion section 25 upstream of the air pump 63, and combustion for burning combustion fuel, reformed gas or anode off gas is performed. Combustion air, which is an oxidant gas, is supplied. The combustion air supply pipe 65 is provided with a combustion air pump 66. The combustion air pump 66 sucks the combustion air supplied from the air supply source Sa and discharges it to the combustion section 25, and is a control device. The combustion air supply amount is adjusted in accordance with 30 commands. When the combustion unit 25 is ignited by a command from the control device 30, the combustion fuel, the reformed gas, or the anode off-gas supplied to the combustion unit 25 is burned to generate a high-temperature combustion gas.

  A CO selective oxidation unit 24 is connected to the inlet of the fuel electrode 11 of the fuel cell 10 via a reformed gas supply pipe 71 so that the reformed gas is supplied to the fuel electrode 11. The combustion part 25 is connected to the outlet of the fuel electrode 11 via an off-gas supply pipe 72 so that anode off-gas discharged from the fuel cell 10 is supplied to the combustion part 25. The bypass pipe 73 bypasses the fuel cell 10 and directly connects the reformed gas supply pipe 71 and the offgas supply pipe 72. The reformed gas supply pipe 71 is provided with a first reformed gas valve (first valve) 74 between the branch point of the bypass pipe 73 and the fuel cell 10. The off gas supply pipe 72 is provided with an off gas valve 75 between the junction with the bypass pipe 73 and the fuel cell 10. The bypass pipe 73 is provided with a second reformed gas valve (second valve) 76. The first and second reformed gas valves 74 and 76 and the offgas valve 75 open and close the respective pipes and are controlled by the control device 30. During start-up operation (reformer warm-up mode), the first reformed gas valve 74 and the off-gas valve are used to avoid supplying reformed gas having a high carbon monoxide concentration from the reformer 20 to the fuel cell 10. 75 is closed and the second reformed gas valve 76 is opened. During the steady operation (FC coupling mode and power generation mode), the first reformed gas valve 74 is supplied to supply the reformed gas from the reformer 20 to the fuel cell 10. The off-gas valve 75 is opened and the second reformed gas valve 76 is closed. As described above, the first and second reformed gas valves 74 and 76 constitute the communication blocking means, and the communication blocking means switches the first flow path L1 and the second flow path L2 between the communication state and the blocking state, respectively. Is.

  The first flow path L1 is a flow path for supplying the fuel gas generated in the reforming section 21 to the combustion section 25 via the fuel electrode 11 of the fuel cell 10, and the second flow path L2 is the reforming section 21. This is a flow path for supplying the fuel gas generated in step 1 to the combustion unit 25 by bypassing the fuel electrode 11 of the fuel cell 10. The first flow path L1 is a flow path that connects the CO selective oxidation unit 24 and the combustion unit 25 via the fuel cell 10 and supplies fuel gas to the reformed gas supply pipe 71 and the fuel electrode 11 of the fuel cell 10. A flow path (not shown) and an off-gas supply pipe 72. The second flow path L2 is a flow path that connects the CO selective oxidation unit 24 and the combustion unit 25 without passing through the fuel cell 10, and includes a reformed gas supply pipe 71, a bypass pipe 73, and an off-gas supply pipe 72. ing. In addition, the 2nd flow path L2 may connect the fuel gas outlet of the reformer 20, and the inlet of the combustion part 25 irrespective of the 1st flow path L1, besides providing the bypass path 73.

  The tip of a cathode air supply pipe 67 branched from the combustion air supply pipe 65 upstream of the air pump 66 is connected to the inlet of the air electrode 12 of the fuel cell 10. Air is supplied. The cathode air supply pipe 67 is provided with a cathode air pump 68 and a cathode air valve 69 in order from the upstream. The cathode air pump 68 sucks air supplied from the air supply source Sa and discharges it to the air electrode 12 of the fuel cell 10, and adjusts the cathode air supply amount in accordance with a command from the control device 30. . The cathode air valve 69 opens and closes the cathode air supply pipe 67 according to a command from the control device 30. Further, one end of an exhaust pipe 82 whose other end is opened to the outside is connected to the outlet of the air electrode 12 of the fuel cell 10.

  A reformed gas condenser 77, an anode offgas condenser 78, and a cathode offgas condenser 79 are provided in the middle of the reformed gas supply pipe 71, offgas supply pipe 72, and exhaust pipe 82, respectively. The reformed gas condenser 77 condenses water vapor in the reformed gas supplied to the fuel electrode 11 of the fuel cell 10 flowing in the reformed gas supply pipe 71. The anode offgas condenser 78 condenses water vapor in the anode offgas discharged from the fuel electrode 11 of the fuel cell 10 flowing in the offgas supply pipe 72. The cathode offgas condenser 79 condenses the water vapor in the cathode offgas discharged from the air electrode 12 of the fuel cell 10 flowing in the exhaust pipe 82. Each of the condensers 77 to 79 is provided with a refrigerant pipe through which a low-temperature liquid in a hot water tank (not shown) or a liquid cooled by a radiator and a cooling fan is supplied, and each gas is exchanged by heat exchange with the liquid. The water vapor inside is condensed.

  These condensers 77, 78, and 79 communicate with the pure water device 95 through the pipe 84, and the condensed water condensed in each of the condensers 77, 78, and 79 is led out to the pure water device 95 and collected. It has become so. The deionizer 95 converts the condensed water supplied from each of the condensers 77, 78, and 79, that is, recovered water, into pure water using a built-in ion exchange resin. The purified water is led to the water tank Sw. To do. A water supply pipe 91 for introducing makeup water (tap water) supplied from a tap water supply source (for example, a water pipe) is connected to the water purifier 95, and the amount of water stored in the water purifier 95 is the lower limit water level. Below that, tap water is supplied.

  Further, the fuel cell system includes a control device 30. The control device 30 includes the temperature sensors 21c, 23e, 24b, and 26a, the inverter 13, the voltmeter 15b, and the pumps 43, 48, 53, and 63 described above. , 66, 68, valves 42, 45, 54, 64, 69, 74, 75, 76, and the combustion section 25 are connected (see FIG. 2). The control device 30 includes a microcomputer (not shown), and the microcomputer includes an input / output interface, a CPU, a RAM, and a ROM (all not shown) connected through a bus. The CPU inputs each temperature from each temperature sensor 21c, 23e, 24b, 26a, the output current from the inverter 13 (output current of the fuel cell 10), and the power consumption from the wattmeter 15b, and inputs each pump 43, By controlling the valves 48, 53, 63, 66, and 68, the valves 42, 45, 54, 64, 69, 74, 75, and 76, and the combustion section 25, the start-up operation and the steady operation of the system are executed. . The RAM temporarily stores variables necessary for executing the program, and the ROM stores the program.

  Further, as shown in FIG. 3, the control device 30 displays a map or an arithmetic expression indicating the correlation between the output power (output current) of the fuel cell 10 and the reforming fuel supply amount for each hydrogen utilization rate. I remember it. In this embodiment, hydrogen utilization rates of 75% and 85% are shown. The hydrogen utilization rate represents the ratio of the amount of hydrogen consumed in the fuel cell 10 to the amount of hydrogen in the fuel gas supplied to the fuel cell 10. As the hydrogen utilization rate increases, the amount of reforming fuel supplied with the same output power decreases.

  The operation of the fuel cell system described above will be described with reference to FIGS. When a start switch (not shown) is turned on at time t0, control device 30 starts warm-up operation (start-up operation) of the fuel cell system (step 102). Specifically, the control device 30 advances the program to the warm-up operation routine shown in FIG. 5, and performs the warm-up operation of the reformer 20 in this warm-up operation routine.

  The control device 30 executes the processing after step 202 every time this routine is started. The control device 30 closes the first reformed gas valve 74 and the offgas valve 75 and opens the second reformed gas valve 76 to directly connect the CO selective oxidation unit 24 to the combustion unit 25 (step 202). The open second fuel valve 45 is closed and the fuel supply source Sf is connected only to the combustion unit 25 (step 204).

  The control device 30 drives the combustion fuel pump 48 and the combustion air pump 66 to supply combustion fuel and combustion air to the combustion unit 25 (step 206), and ignites the combustion unit 25 (step 208). Thereby, combustion is started in the combustion part 25.

  The control device 30 sets the target temperature that is the target combustion state of the combustion unit 25 to the first target temperature (for example, 800 ° C.) that is the first target combustion state (step 210). This first target temperature is higher than a second target temperature (for example, 700 ° C.) set for steady operation. This is due to the following reason. That is, since it is desired to warm up the reformer 20 as early as possible in the warm-up operation, it is necessary to heat it at as high a temperature as possible in consideration of the heat-resistant temperature of the reforming catalyst 21b. The second target temperature is set to an optimum temperature in consideration of the activation temperature of the reforming catalyst 21b. Then, the control device 30 detects the combustion temperature of the combustion section 25 by the temperature sensor 21c (step 212), and first sets the combustion temperature of the combustion section 25 detected by feedback control of the combustion fuel pump 48. The target temperature is adjusted (step 214). As a result, the combustion fuel is combusted and the combustion gas flows through the combustion gas flow path 27, and the reforming catalyst 21 a and the evaporation unit 26 in the reforming unit 21 are heated by the combustion gas.

  The control device 30 detects the temperature of the evaporation unit 26 by the temperature sensor 26a, and when the detected temperature is equal to or higher than the first predetermined temperature Th1 (time t1), the water valve 54 is opened and the water pump 53 is driven. A predetermined amount of water in the water tank Sw is supplied to the reforming unit 21 through the evaporation unit 26 (steps 216 and 218).

  The control device 30 starts counting the timer from the time (time t1) when the temperature of the evaporation unit 26 becomes equal to or higher than the predetermined temperature Th1. When the timer reaches a predetermined time Tm1 (for example, 1 minute) or more (step 220), the second fuel valve 45 is opened at time t2 to connect the fuel supply source Sf to the reforming unit 21 and the reforming fuel pump 43. Is driven to supply the reforming fuel from the fuel supply source Sf to the reforming unit 21 by a predetermined flow rate (step 222). Further, the air valve 64 is opened to connect the air supply source Sa to the CO selective oxidation unit 24 and the air pump 63 is driven to supply the air from the air supply source Sa to the CO selective oxidation unit 24 by a predetermined flow rate (predetermined supply amount). (Step 224). Thus, the reformed fuel and steam mixed gas are supplied to the reforming unit 21, and the reforming unit 21 generates the reformed gas by causing the steam reforming reaction and the carbon monoxide shift reaction described above. Then, the reformed gas derived from the reforming unit 21 is reduced in carbon monoxide gas by the CO shift unit 23 and the CO selective oxidation unit 24 and derived from the CO selective oxidation unit 24, and burns without passing through the fuel cell 10. It is supplied directly to the section 25 and burned. Then, after executing the process of step 224, the control device 30 advances the program to step 226 to end this routine, and proceeds to step 104 and subsequent steps shown in FIG.

  In this way, during the generation of the reformed gas, the control device 30 detects the temperature of the catalyst 24a of the CO selective oxidation unit 24 by the temperature sensor 24b in step 104, and the detected temperature is lower than the second predetermined temperature Th2. If this is the case, it is determined that the warm-up of the reformer 20 has not been completed, and the process of step 104 is repeatedly performed. The temperature of the catalyst 24a of the CO selective oxidation unit 24 is increased and the detected temperature is the second predetermined value. If the temperature becomes equal to or higher than Th2 (time t3), it is determined that the reformer 20 has been warmed up, and the program proceeds to step 106.

  In step 106, the control device 30 changes the combustion part target temperature previously set to the first target temperature in step 210 to the second target temperature after the time point when the reformer 20 has been warmed up. As a result, the control device 30 detects the combustion temperature of the combustion unit 25 by the temperature sensor 21c, and becomes the second target temperature that sets the combustion temperature of the combustion unit 25 detected by feedback control of the combustion fuel pump 48. Adjust to. Therefore, the temperature of the reforming unit 21 is lowered to the activation temperature of the reforming catalyst 21b.

  In addition, the control device 30 opens the first reformed gas valve 74 and the offgas valve 75 after the time point (time t4) when the warming-up of the reformer 20 is completed (step 108). As a result, the CO selective oxidation unit 24 is connected to the inlet of the fuel electrode 11 of the fuel cell 10 and the outlet of the fuel electrode 11 is connected to the combustion unit 25 at time t4, from time t4 to time t5 ( At a predetermined time T1), the CO selective oxidation unit 24 enters the combustion unit 25 through both the first flow path L1 (flow path passing through the fuel cell 10) and the second flow path L2 (flow path not passing through the fuel cell 10). Connecting. Thereby, the fuel gas produced | generated in the reforming part 21 is supplied to the combustion part 25 through both the 1st and 2nd flow paths L1, L2.

  The control device 30 performs FC coupling control (transient control for connecting the fuel cell (FC) to the reformer) from when the first reformed gas valve 74 and the offgas valve 75 are opened until a first predetermined time T1 elapses. Is executed (step 112). Specifically, the control device 30 advances the program to the FC coupling routine shown in FIG. 6, and executes the processing from step 302 onward whenever this routine is started.

  The control device 30 sets the hydrogen utilization rate to the first set value C1-k1 (step 302), and detects the power generation output (power generation current) by the inverter 13 (step 304). C1 is the second set value (85%), and k1 is a constant (10%). And the control apparatus 30 selects the thing of 1st setting value C1-k1 from the map shown in FIG. 3, and the fuel of the reforming fuel according to the power generation output (power generation current) detected previously from the selected map is shown. The supply amount is derived (step 306), and the reforming fuel pump 43 is controlled to adjust to the derived supply amount (step 308). Thereby, the supply amount of the reforming fuel is increased from the required amount, and the combustible gas supplied to the combustion unit 25 (the reforming fuel not reformed by the reforming unit 21 and not used in the fuel cell 10). (Including hydrogen).

  Further, the control device 30 controls the combustion fuel pump 48 from the time when the first reformed gas valve 74 and the offgas valve 75 are opened (time t4) to the time when the first predetermined time T1 has elapsed (time t5). The minimum rotation speed is set from the second rotation speed C2 (500 rotations) to a higher first rotation speed C2 + k2 (750 rotations) (step 310). Then, after executing the process of step 310, control device 30 advances the program to step 312, ends this routine, and returns to step 110 shown in FIG. The first rotational speed is set so as to be suppressed to a magnitude sufficient to control pulsation generated by driving the combustion fuel pump 48 that is a diaphragm pump. The second rotational speed is set in consideration of the sliding resistance of the combustion fuel pump 48.

  When the first predetermined time T1 has elapsed from the time when the first reformed gas valve 74 is opened (time t5), the control device 30 closes the second reformed gas valve 76 (step 114). As a result, after time t5, the second flow path L2 is cut off and only the first flow path L1 is in communication, so that all the fuel gas from the CO selective oxidation unit 24 is supplied to the fuel cell 10 and the fuel cell 10 Starts power generation.

  The control device 30 performs the above-described FC coupling control from the time t5 until the second predetermined time T2 elapses from the time when the first reformed gas valve 74 is opened (time t4), and the supply amount of the reforming fuel. The supply amount of combustible gas (including reforming fuel that has not been reformed by the reforming unit 21 and hydrogen that has not been used by the fuel cell 10) that is supplied to the combustion unit 25 by increasing the amount of fuel is increased. (Step 118). Specifically, the control device 30 advances the program to the FC coupling routine shown in FIG. 6 in the same manner as described above, and when this routine ends, the control device 30 returns to step 116 shown in FIG. The first and second predetermined times T1 and T2 are determined experimentally because they differ depending on the system.

  Then, when the second predetermined time T2 elapses from the time when the first reformed gas valve 74 is opened (time t6), the control device 30 starts normal power generation thereafter. Specifically, the control device 30 sets the hydrogen utilization rate to the second set value C1 (step 120), and detects the power generation output (power generation current) by the inverter 13 (step 122). And the control apparatus 30 selects the thing of 1st setting value C1 (75%) from the map shown in FIG. 3, and it is for the reforming according to the power generation output (power generation current) detected previously from the selected map. A fuel supply amount is derived (step 124), and the reforming fuel pump 43 is controlled to be adjusted to the derived supply amount (step 126).

  Control device 30 repeatedly executes the processing of steps 128 and 130 until an operation stop instruction is issued. In other words, the control device 30 determines that the amount of hydrogen generated in the reformer 20 is a predetermined amount, that is, the output current of the fuel cell system is determined based on the current / power consumed at the power use place 15. The reforming fuel, the combustion fuel, the combustion air, the oxidizing air, the cathode air, and the reforming water are supplied so that the output current becomes (step 128).

  The control device 30 calculates the reforming fuel supply amount so that the hydrogen amount becomes a predetermined amount (the same processing as steps 122 to 126), and drives the reforming fuel pump 43 so as to obtain the supply amount. . The reforming water supply amount is calculated based on the reforming fuel supply amount and S / C (steam carbon ratio), and the water pump 53 is driven so as to obtain the supply amount. When the combustion energy of the anode off gas alone is insufficient for the combustion unit 25, the amount of combustion fuel supplied to the combustion unit 25 is calculated and the combustion fuel pump 48 is adjusted so as to be the amount supplied. Driven. At this time, the minimum rotational speed of the combustion fuel pump 48 is set to the second rotational speed C2. Further, the combustion air pump 66 is driven so that the combustion air supply amount is calculated based on the reforming fuel supply amount and the like, and the supply amount is obtained. Further, the supply amount of the oxidizing air is calculated so that the carbon monoxide is not more than a predetermined amount, and the air pump 63 is driven so as to be the supply amount. The cathode air pump 68 is driven so as to calculate a supply amount of cathode air suitable for reacting with the reformed gas supplied from the reformer 20 and to obtain the supply amount. Then, the control device 30 stops the fuel cell system when there is an operation stop instruction such as pressing a stop switch (steps 130 and 132).

  In step 132, the control device 30 performs a system stop process. At this time, a purge process is performed on the fuel electrode side of the fuel cell 10 to reduce the hydrogen concentration to zero. As this purge process, a method of expelling the fuel gas with a purge gas such as an inert gas, air or combustion exhaust gas, a method of reducing the hydrogen concentration by sending an air to oxidize, and applying a voltage to the fuel cell 10 while circulating water vapor There is a method of transporting the hydrogen of the fuel electrode 11 to the oxidant electrode 12 to reduce the hydrogen concentration. In any method, the fuel electrode 11 stops the system with residual gas having a low hydrogen concentration remaining.

  As is clear from the above description, in the present embodiment, when the warm-up mode is shifted to the power generation mode, the first predetermined time T1 is set from the time point (time t4) when the first flow path L1 is in the communication state. Until the elapsed time (time t5), residual gas remaining in the first flow path L1 during the stop process passes through the second flow path L2 from the CO selective oxidation unit 24 (reforming unit 21). Since it is supplied to the combustion part 25 together with the supplied fuel gas, it is possible to prevent the combustion part 25 from misfiring due to fluctuations in the combustion state due to the dilution of the combustible gas by the residual gas as in the prior art. it can.

  In addition, the fuel cell 10 is set between the time when the hydrogen utilization rate setting means (step 120) sets the first flow path L1 in the communication state (time t4) until the second predetermined time T2 elapses (time t6). The hydrogen utilization rate representing the ratio of the amount of hydrogen consumed in the fuel cell 10 to the amount of hydrogen in the fuel gas supplied to the fuel cell 10 is set to a first set value, and thereafter the hydrogen utilization rate is greater than the first set value. The reforming fuel supply amount deriving means (steps 122 and 124) is set to the second set value, and based on the power generation output of the fuel cell 10 and the hydrogen utilization rate set by the hydrogen utilization rate setting means (step 120). The amount of reforming fuel supplied to the reforming unit 21 is derived, and the reforming fuel supply control means (step 126) is derived by the reforming fuel supply amount deriving means (steps 122 and 124). Changed to be supply amount To control the use fuel pump 45. As a result, the amount of reforming fuel supplied is increased by setting the hydrogen utilization rate lower than that in the power generation mode until the second predetermined time T2 elapses from the time when the first flow path L1 is in the communication state. Therefore, it is possible to prevent the combustion unit 25 from being misfired by increasing the supply amount of the combustible gas supplied to the combustion unit 25.

  Further, the target combustion state setting means sets the target temperature that is the target combustion state of the combustion section 25 to the first target temperature that is the first target combustion state until the warm-up of the reformer 20 is completed (step 210). ) After the warm-up of the reformer 20 is completed, the target temperature of the combustion unit 25 is set to the second target temperature that is the second target combustion state that is on the misfire state side from the first target temperature (step 106). The combustion fuel supply control means (step 214) adjusts the combustion state of the combustion section 25 so as to achieve the target combustion state set by the target combustion state setting means by feedback controlling the combustion fuel pump 48, Control is performed so that the rotational speed of the combustion fuel pump 48 does not become lower than the lower limit rotational speed (minimum rotational speed). Thereby, when shifting from the warm-up mode to the power generation mode, the combustion state 25 is prevented from changing and the combustion unit 25 is misfired without causing a decrease in robustness and a decrease in inheritance of control at the time of switching. be able to.

  Further, when a diaphragm pump is used as the combustion fuel pump 48, the combustion is not performed until the second predetermined time T2 elapses from the time when the lower limit rotation speed setting means sets the first flow path L1 to the communication state. The lower limit rotational speed (minimum rotational speed) of the fuel pump 48 is set to the first rotational speed (step 310), and thereafter, the lower limit rotational speed is set to the second rotational speed smaller than the first rotational speed (step 128). The combustion fuel supply control means (step 214) uses the lower limit rotational speed set by the lower limit rotational speed setting means. Thereby, it is possible to prevent pulsation due to the driving of the diaphragm pump and to control the supply amount of the combustion fuel with high accuracy.

  Further, the communication blocking means is provided in the first flow path L1, and is provided in the first flow path L1 and opens and closes the first flow path L1, and the second reformed gas valve 74 is provided in the second flow path L2. Since the second reformed gas valve 76, which is the second valve for opening and closing the flow path L2, is configured without changing the existing configuration or adding another member, that is, increase in size and height It is possible to prevent the combustion section from misfiring without incurring cost.

  In the above-described embodiment, the communication blocking means includes the first reformed gas valve 74 that is a first valve that is provided in the first flow path L1 and opens and closes the first flow path L1, and the second flow path L2. The second reformed gas valve 76, which is a second valve that is provided on the second passage and opens and closes the second flow path L2, is configured as a three-way valve. In this case, the three-way valve may be provided at the branch point between the reformed gas supply pipe 71 and the bypass pipe 73. This three-way valve connects the CO selective oxidation unit 24 directly to the combustion unit 25 without passing through the fuel cell 10 in the reformer warm-up mode, and the warm-up of the reformer 20 is completed for the first predetermined time T1. In the meantime, the CO selective oxidation unit 24 is directly connected to the combustion unit 25 without passing through the fuel cell 10 and connected to the combustion unit 25 through the fuel cell 10, and after the first predetermined time T1 has elapsed, The CO selective oxidation unit 24 is switched to be connected to the combustion unit 25 via the fuel cell 10.

  In the above-described embodiment, the combustion state is represented by the combustion temperature, but it may be represented by an ionic current instead. In this case, an ionic current detection device that detects the ionic current may be provided in the combustion unit 25.

  In the above-described embodiment, a blower (blower) is employed instead of the pumps such as the reforming fuel pump 43 that is the reforming fuel supply means and the combustion fuel pump 48 that is the combustion fuel supply means. It may be.

  In the above-described embodiment, the combustion fuel pump 48 is a diaphragm pump. However, the combustion fuel pump 48 may be a pump other than this type.

It is a schematic diagram showing an outline of one embodiment of a fuel cell system according to the present invention. It is a block diagram which shows the fuel cell system shown in FIG. It is a map which shows the correlation with the output electric power and reforming fuel supply amount for every hydrogen utilization rate. It is a flowchart of the control program performed with the control apparatus shown in FIG. 3 is a flowchart of a warm-up operation routine that is executed by the control device shown in FIG. 2. 3 is a flowchart of an FC coupling control routine executed by the control device shown in FIG. It is a time chart which shows operation | movement of one Embodiment of the fuel cell system by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 11 ... Fuel electrode, 12 ... Air electrode, 13 ... Inverter, 15 ... Electric power use place, 15a ... Electric power consumption apparatus, 15b ... Electricity meter, 20 ... Reformer, 21 ... Reformer, 21a ... Return path, 21b ... catalyst, 22 ... cooling unit, 23 ... CO shift unit, 23d ... catalyst, 23e ... temperature sensor, 24 ... CO selective oxidation unit, 24a ... catalyst, 24b ... temperature sensor, 25 ... combustion unit, 26 DESCRIPTION OF SYMBOLS ... Evaporation part, 26a ... Temperature sensor, 27 ... Combustion gas flow path, 28 ... Heat insulation part, 30 ... Control apparatus, 41 ... Fuel supply pipe, 42 ... 1st fuel valve, 43 ... Fuel pump, 44 ... Desulfurizer, 45 2nd fuel valve, 47 ... Combustion fuel supply pipe, 48 ... Combustion fuel pump, 51 ... Water supply pipe, 52 ... Water vapor supply pipe, 53 ... Water pump, 54 ... Water valve, 61 ... Oxidation air supply pipe, 62 ... Filter, 63 ... Air , 64 ... Air valve, 65 ... Combustion air supply pipe, 66 ... Combustion air pump, 67 ... Cathode air supply pipe, 68 ... Cathode air pump, 69 ... Cathode air valve, 71 ... Reformed gas supply 72, off gas supply pipe, 73 ... bypass pipe, 74 ... first reformed gas valve, 75 ... off gas valve, 76 ... second reformed gas valve, 77, 78, 79 ... condenser, 81, 82 ... exhaust pipe, 84 ... pipe, 89 ... connecting pipe, 91 ... water supply pipe, 95 ... pure water purifier, Sa ... air supply source, Sf ... fuel supply source, Sw ... reformed water supply source.

Claims (2)

A fuel cell that generates electricity using fuel gas and oxidant gas respectively supplied to the fuel electrode and oxidant electrode;
A reforming section that supplies the reforming fuel and reforming water and reforms the supplied reforming fuel with a reforming catalyst to generate the fuel gas containing hydrogen, and a combustible fuel is supplied. A reformer comprising a combustion section that burns combustible fuel and heats the reforming section with the combustion gas;
A first flow path for supplying the fuel gas generated in the reforming section to the combustion section via a fuel electrode of the fuel cell;
A second flow path for supplying the fuel gas generated in the reforming section to the combustion section by bypassing the fuel electrode of the fuel cell;
Communication blocking means for switching the first and second flow paths to a communication state and a block state, respectively,
The communication interrupting means, said warming up mode reformer to warm up the first and second flow paths respectively blocked state and the communication state, before the subsequent time the Kiaratame reformer warm-up is completed wherein the first flow path and the communicating state, a fuel cell system that the second flow path the cut-off state to the elapse first predetermined time from the time when the first flow path and the communicating state,
Reforming fuel supply means for supplying the reforming fuel to the reforming section;
The ratio of the amount of hydrogen consumed in the fuel cell to the amount of hydrogen in the fuel gas supplied to the fuel cell is determined from the time when the first flow path is in the communication state until the second predetermined time elapses. A hydrogen utilization rate setting means for setting a hydrogen utilization rate to be expressed to a first set value and thereafter setting the hydrogen utilization rate to a second set value larger than the first set value;
Reforming fuel supply amount deriving means for deriving a supply amount of reforming fuel to be supplied to the reforming unit based on the power generation output of the fuel cell and the hydrogen utilization rate set by the hydrogen utilization rate setting means; ,
Reforming fuel supply control means for controlling the reforming fuel supply means so as to be the supply amount derived by the reforming fuel supply amount deriving means;
Combustion fuel supply means for supplying the combustion fuel to the combustion section;
Combustion state detection means for detecting the combustion state of the combustion section;
The target combustion state of the combustion section is set to the first target combustion state until the reformer warm-up is completed, and the target combustion state of the combustion section is set after the warm-up of the reformer is completed. A target combustion state setting means for setting a second target combustion state that is on the misfire state side from the first target combustion state;
The combustion fuel supply means is feedback-controlled to adjust the combustion state of the combustion section so that the target combustion state set by the target combustion state setting means is achieved, and the rotational speed of the combustion fuel supply means is a lower limit. In a fuel cell system comprising a combustion fuel supply control means for controlling so as not to become smaller than the rotational speed,
The combustion fuel supply means is a diaphragm pump,
And,
The lower limit rotational speed of the combustion fuel supply means is set to the first rotational speed from the time when the first flow path is in the communication state until the second predetermined time elapses, and thereafter the lower limit rotational speed is set. Further comprising lower limit rotational speed setting means for setting the number to a second rotational speed smaller than the first rotational speed,
The fuel supply control means for combustion uses a lower limit rotational speed set by the lower limit rotational speed setting means . Oite to claim 1, wherein the communication interrupting means comprises a first valve for opening and closing the same first passage provided in the first flow path, the same second passage provided in the second flow path A fuel cell system comprising: a second valve that opens and closes.

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