JP2010118178A - Method for controlling fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress degradation of a fuel cell, and to correct an amount of fuel supply following change of power generation output without adversely affecting heat independence. <P>SOLUTION: A method of driving a fuel cell system 10 includes steps of: measuring at least a current output value of a fuel cell stack 28, an A/F value of the fuel cell stack 28, and a temperature of the fuel cell stack 28; and controlling an amount of fuel gas supplied to the fuel cell stack 28 based on at least any of the current output value, the A/F value, or the temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control method for a fuel cell system including a fuel cell stack in which a plurality of fuel cells that generate power by an electrochemical reaction between a fuel gas and an oxidant gas are stacked, and a control device.

  In general, a solid oxide fuel cell (SOFC) uses an oxide ion conductor, for example, stabilized zirconia, as a solid electrolyte, and an electrolyte / electrode in which an anode electrode and a cathode electrode are disposed on both sides of the solid electrolyte. A joined body (hereinafter also referred to as MEA) is sandwiched between separators (bipolar plates). This fuel cell is normally used as a fuel cell stack in which a predetermined number of electrolyte / electrode assemblies and separators are laminated.

  In order to control the operation of this type of fuel cell stack, for example, a fuel cell control method disclosed in Patent Document 1 is known. In this fuel cell control method, in controlling a fuel cell having a fuel cell stack to which a reformed fuel and an oxidant are supplied, at least one of the single cells constituting the fuel cell stack is used as a remaining cell. A single cell for monitoring having a current-voltage characteristic lower than that of the single cell, the voltage of the single cell for monitoring is constant, power generation of the fuel cell stack, and an output current value of the fuel cell stack is detected, A difference between an output current value and a preset set current value is obtained, and the fuel supply amount and / or the oxidant supply amount is changed in accordance with the difference.

  Further, in the fuel cell control method disclosed in the cited document 2, in controlling the fuel cell to which the reformed fuel and the oxidant are supplied, the fuel cell is generated at a constant voltage, and the output of the fuel cell is A current is detected, a difference between the output current value and a preset current value is obtained, and the supply amount of the fuel and / or the supply amount of the oxidant is changed according to the difference.

Japanese Patent Application Laid-Open No. 64-039968 Japanese Unexamined Patent Publication No. 64-039969

  In the above-mentioned Patent Document 1, the supply amount of fuel and oxidant is changed according to the difference between the output current value of the fuel cell stack and the preset current value. However, if the supply amount of fuel or oxidant is changed when the fuel cell is out of the optimal operating range, particularly when the A / F value (described later) is out of the optimal range, the fuel cell may be changed. May deteriorate.

  In Patent Document 2, the amount of fuel and oxidant supplied is changed according to the difference between the output current value of the fuel cell and the preset current value. For this reason, like the above-mentioned Patent Document 1, there is a problem that the fuel cell is likely to be deteriorated if it is out of the optimum operating range of the fuel cell.

  The present invention solves this type of problem, and while suppressing deterioration of the fuel cell, it is possible to satisfactorily correct the fuel supply amount following the change in the power generation output without impairing thermal independence. An object of the present invention is to provide a control method for a fuel cell system.

  The present invention relates to a control method for a fuel cell system including a fuel cell stack in which a plurality of fuel cells that generate power by an electrochemical reaction between a fuel gas and an oxidant gas are stacked, and a control device.

  The control method includes a step of measuring at least a current output value of the fuel cell stack, an A / F value of the fuel cell stack, and a temperature of the fuel cell stack, and at least the current output value, the A / F value, or the And controlling the amount of fuel gas supplied to the fuel cell stack based on one of the temperatures.

  Here, the A / F value is a ratio between the oxidant gas and the fuel gas supplied to the fuel cell, and has a relationship of A / F value = (oxidant gas) / (fuel gas) value.

  The control method according to the present invention includes a first step of setting a target output value of the fuel cell stack or a predetermined range of the target output value, and a second step of measuring a current output value of the fuel cell stack. A third step of measuring the A / F value of the fuel cell stack, a fourth step of measuring the temperature of the fuel cell stack, the target output value or a predetermined range of the target output value, and the current output A fifth step of comparing values, a sixth step of comparing the A / F value with a preset upper or lower limit value of the A / F value, the temperature, and a preset value. A seventh step of comparing the upper limit value or the lower limit value of the temperature; an eighth step of maintaining the amount of the fuel gas supplied to the fuel cell stack; and the fuel gas supplied to the fuel cell stack. A ninth step of reducing the amount of the fuel, and the fuel And a tenth step of increasing the amount of the fuel gas supplied to the pond stack.

  Then, at least one of the eighth step, the ninth step, and the tenth step is performed based on the comparison result of at least the fifth step, the sixth step, or the seventh step.

  Further, in this control method, it is preferable to perform the eighth step when it is determined in the fifth step that the current output value is equal to or within the predetermined range of the target output value. Therefore, since the fuel cell stack maintains the fuel supply amount based on the current output value, it is possible to perform an appropriate operation by causing the current output value to follow the target output value.

  Furthermore, in this control method, it is determined in the fifth step that the current output value exceeds the target output value or exceeds a predetermined range of the target output value, and the A / F value is determined in the sixth step. Is determined to be equal to or lower than the upper limit value of the preset A / F value, and in the seventh step, it is determined that the temperature is equal to or higher than the lower limit value of the preset temperature. It is preferable to perform this process.

  As described above, the fuel supply amount reduction processing is performed based on the current output value, A / F value, and temperature of the fuel cell stack. Therefore, in the anode electrode constituting the fuel cell, it is possible to prevent the anode electrode from being oxidized due to the oxidant gas flowing around due to fuel depletion, and it is possible to prevent the anode electrode from deteriorating. . On the other hand, in the fuel cell stack, carbon deposition due to insufficient heat, a decrease in power generation efficiency, or evaporation and insufficient reforming is suppressed. As a result, the durability and life of the fuel cell system are improved, and there is no risk of impairing heat self-supporting.

  In this control method, in the fifth step, it is determined that the current output value exceeds the target output value or exceeds the predetermined range of the target output value, and in the sixth step, the A / F value is When it is determined that the upper limit value of the preset A / F value is exceeded, the eighth step is preferably performed.

  Thus, the fuel supply amount is maintained based on the current output value and A / F value of the fuel cell stack. Therefore, in the anode electrode, it is possible to prevent the anode electrode from being oxidized by the oxidant gas flowing around due to fuel depletion, and it is possible to prevent the anode electrode from being deteriorated. For this reason, durability and lifetime of the fuel cell system are improved.

  Further, in this control method, in the fifth step, it is determined that the current output value exceeds the target output value or exceeds the predetermined range of the target output value, and in the sixth step, the A / F value is When it is determined that the temperature is equal to or lower than the upper limit value of the preset A / F value and the temperature is determined to be lower than the lower limit value of the preset temperature in the seventh step, It is preferable to perform a process.

  Thus, the fuel supply amount is maintained based on the current output value, A / F value, and temperature of the fuel cell stack. Therefore, in the anode electrode, it is possible to prevent the anode electrode from being oxidized by the oxidant gas flowing around due to fuel depletion, and it is possible to prevent the anode electrode from being deteriorated. On the other hand, in the fuel cell stack, carbon deposition due to insufficient heat, a decrease in power generation efficiency, or evaporation and insufficient reforming is suppressed. As a result, the durability and life of the fuel cell system are improved, and there is no risk of impairing heat self-supporting.

  Furthermore, in this control method, in the fifth step, it is determined that the current output value is less than the target output value or less than a predetermined range of the target output value, and in the sixth step, the A / F value is determined. Is determined to be equal to or higher than the lower limit value of the preset A / F value, and when the temperature is determined to be equal to or lower than the upper limit value of the preset temperature in the seventh step, It is preferable to perform this process.

  As described above, the fuel supply amount increasing process is performed based on the current output value, A / F value, and temperature of the fuel cell stack. For this reason, in the cathode electrode, it is possible to prevent the cathode electrode from being reduced due to the inflow of fuel gas due to the exhaustion of air, and it is possible to prevent the cathode electrode from deteriorating. On the other hand, in the fuel cell stack, excessive heat, reduction in power generation efficiency, or oxidation of the separator, aggregation of the electrolyte / electrode assembly, and deterioration of the reforming catalyst due to high temperature of the separator and the electrolyte / electrode assembly are suppressed. As a result, the durability and life of the fuel cell system are improved, and there is no risk of impairing heat self-supporting.

  In this control method, it is determined in the fifth step that the current output value is less than the target output value or less than a predetermined range of the target output value, and in the sixth step, the A / F value is When it is determined that the value is less than the preset lower limit of the A / F value, the eighth step is preferably performed.

  Thus, the fuel supply amount is maintained based on the current output value and A / F value of the fuel cell stack. Therefore, in the cathode electrode, it is possible to prevent the cathode electrode from being reduced due to the inflow of fuel gas due to the exhaustion of air, and it is possible to prevent the cathode electrode from deteriorating. For this reason, durability and lifetime of the fuel cell system are improved.

  Further, in this control method, it is determined in the fifth step that the current output value is less than the target output value or less than a predetermined range of the target output value, and in the sixth step, the A / F value is When it is determined that the temperature is equal to or higher than the lower limit value of the preset A / F value and the temperature is determined to exceed the upper limit value of the preset temperature in the seventh step, It is preferable to perform this process.

  Thus, the fuel supply amount is maintained based on the current output value, A / F value, and temperature of the fuel cell stack. Thereby, in the cathode electrode, it is possible to prevent the cathode electrode from being reduced by the wraparound of the fuel gas due to the exhaustion of air, and it is possible to prevent the cathode electrode from deteriorating. On the other hand, in the fuel cell stack, excessive heat, reduction in power generation efficiency, or oxidation of the separator, aggregation of the electrolyte / electrode assembly, and deterioration of the reforming catalyst due to high temperature of the separator and the electrolyte / electrode assembly are suppressed. Therefore, the durability and life of the fuel cell system are improved, and there is no risk of impairing heat self-supporting.

  Furthermore, the fuel cell is preferably a solid oxide fuel cell. Therefore, the fuel cell is a high-temperature fuel cell that generates a large amount of heat, and can further improve the durability and life of the fuel cell system.

  The solid oxide fuel cell is preferably a flat plate solid oxide fuel cell in which an electrolyte / electrode assembly is sandwiched between separators. Thereby, it can be applied particularly well to a sealless type fuel cell, and the durability and life of the fuel cell system can be further improved.

  According to the present invention, based on the current output value of the fuel cell stack, the A / F value of the fuel cell stack, and the temperature of the fuel cell stack, control of the fuel supply amount, that is, maintenance of the fuel supply amount, Decrease and increase processing.

  Therefore, in the anode electrode constituting the fuel cell, it is possible to prevent the anode electrode from being oxidized due to the oxidant gas flowing around due to fuel depletion, and it is possible to prevent the anode electrode from deteriorating. .

  Further, in the cathode electrode constituting the fuel cell, it is possible to prevent the cathode electrode from being reduced by the flow of the fuel gas due to the exhaustion of air, and it is possible to prevent the cathode electrode from being deteriorated.

  Further, in the fuel cell stack, carbon deposition due to insufficient heat, a decrease in power generation efficiency, or evaporation and insufficient reforming is suppressed, while surplus heat, a decrease in power generation efficiency or a high temperature of the fuel cell constituent members is suppressed.

  As a result, the durability and life of the fuel cell system are improved, and there is no risk of impairing heat self-supporting.

  FIG. 1 is a schematic configuration diagram illustrating a mechanical circuit of a fuel cell system 10 to which the control method according to the first embodiment of the present invention is applied, and FIG. 2 is a circuit diagram of the fuel cell system 10. is there.

  The fuel cell system 10 is used for various purposes such as in-vehicle use as well as stationary use. The fuel cell system 10 includes a fuel cell module (SOFC module) 12 that generates electric power by an electrochemical reaction between a fuel gas (hydrogen gas) and an oxidant gas (air), and a raw fuel (for example, city gas) in the fuel cell module 12. ) 16, an oxidant gas supply device (including an air pump) 18 for supplying the oxidant gas to the fuel cell module 12, and the fuel cell module 12. A water supply device (including a water pump) 20 that supplies water, a power conversion device 22 that converts DC power generated in the fuel cell module 12 into required specification power, and a power generation amount of the fuel cell module 12 are controlled. And a control device 24.

  The fuel cell module 12 includes a solid oxide fuel cell stack 28 in which a plurality of solid oxide fuel cells 26 are stacked in the vertical direction. As shown in FIGS. 3 and 4, the fuel cell 26 is provided with a cathode electrode 32 and an anode electrode 34 on both surfaces of an electrolyte (electrolyte plate) 30 made of an oxide ion conductor such as stabilized zirconia, for example. The electrolyte-electrode assembly (MEA) 36 is provided. The electrolyte / electrode assembly 36 is formed in a disc shape, and a barrier layer (not shown) is provided at least on the outer peripheral end surface portion to prevent the oxidant gas and fuel gas from entering and discharging. Yes.

  In the fuel cell 26, four electrolyte / electrode assemblies 36 are arranged concentrically between the separators 38 around the fuel gas supply communication hole 40 that is the center of the separator 38. For example, the separator 38 is composed of a single metal plate, a carbon plate, or the like that is composed of a sheet metal such as a stainless alloy.

  The separator 38 has a fuel gas supply part 42 that forms a fuel gas supply communication hole 40 in the center. A relatively large-diameter clamping portion 46 is integrally formed through four first bridge portions 44 that are radially spaced apart from the fuel gas supply portion 42 by equal angular intervals (90 ° intervals). Provided.

  Each clamping part 46 is set to a disk shape having substantially the same dimensions as the electrolyte / electrode assembly 36 and is configured to be separated from each other. A fuel gas supply hole 48 for supplying fuel gas is set in the sandwiching portion 46, for example, at a position eccentric to the upstream of the oxidant gas flow direction with respect to the center of the sandwiching portion 46 or the center.

  A fuel gas passage 50 for supplying fuel gas along the electrode surface of the anode electrode 34 is formed in the surface 45a of each clamping portion 46 that contacts the anode electrode 34. In the surface 45a, the fuel gas discharge passage 52 for discharging the fuel gas used through the fuel gas passage 50 and the anode electrode 34 are contacted, and the fuel gas is supplied from the fuel gas supply hole 48 to the fuel gas discharge passage 48. An arcuate wall portion 54 for forming a bypass is provided at 52 to prevent the flow from flowing in a straight line.

  The surface 45 a is provided with an outer peripheral circumferential protrusion 56 that protrudes toward the fuel gas passage 50 and contacts the outer peripheral edge of the anode electrode 34, and a plurality of protrusions 58 that contact the anode electrode 34.

  The surface 45b that contacts the cathode electrode 32 of each clamping part 46 is formed in a substantially flat surface, and a disk-shaped plate 60 is formed on the surface 45b by, for example, brazing, diffusion bonding, laser welding, or the like. It is fixed. The plate 60 is provided with a plurality of protrusions 62 by pressing or the like. An oxidant gas passage 64 for supplying an oxidant gas along the electrode surface of the cathode electrode 32 is formed by the protrusion 62 on the surface 45b side of the sandwiching part 46, and the protrusion 62 has a current collector. Parts.

  A passage member 70 is fixed to the surface of the separator 38 facing the cathode electrode 32 by, for example, brazing, diffusion bonding, laser welding, or the like. The passage member 70 is configured in a flat plate shape, and includes a fuel gas supply portion 72 that forms the fuel gas supply communication hole 40 in the center portion.

  Four second bridge portions 74 extend radially from the fuel gas supply portion 72, and each second bridge portion 74 extends from the first bridge portion 44 of the separator 38 to the surface 45 b of the sandwiching portion 46. 48 is fixed over.

  A fuel gas supply passage 76 that communicates from the fuel gas supply communication hole 40 to the fuel gas supply hole 48 is formed in the second bridge portion 74 from the fuel gas supply portion 72. The fuel gas supply passage 76 is formed by etching or pressing, for example.

  The oxidant gas passage 64 communicates with an oxidant gas supply communication hole 78 that supplies oxidant gas in the direction of arrow B from between the inner peripheral end of the electrolyte / electrode assembly 36 and the inner peripheral end of the sandwiching portion 46. To do. The oxidant gas supply communication hole 78 is located between the inner side of each clamping part 46 and the first bridge part 44 and extends in the stacking direction (arrow A direction).

  As shown in FIG. 5, an insulating seal 80 for sealing the fuel gas supply communication hole 40 is provided between the separators 38. The insulating seal 80 has a function of sealing the fuel gas supply communication hole 40 against the electrolyte / electrode assembly 36. In the fuel cell 26, an exhaust gas passage 82 is formed outside the clamping portion 46.

  As shown in FIG. 1, on the upper end side (or lower end side in the stacking direction) of the fuel cell stack 28, a heat exchanger 86 that heats the oxidant gas before being supplied to the fuel cell stack 28, and the raw fuel In order to generate a mixed fuel of water and water vapor, an evaporator 88 that evaporates water and a reformer 90 that reforms the mixed fuel to generate a reformed gas are disposed.

  On the lower end side (or upper end side in the stacking direction) of the fuel cell stack 28, a load is applied to apply a tightening load along the stacking direction (arrow A direction) to the fuel cells 26 constituting the fuel cell stack 28. A mechanism 92 is disposed (see FIG. 2).

The reformer 90 removes higher hydrocarbons (C ₂₊ ) such as ethane (C ₂ H ₆ ), propane (C ₃ H ₆ ) and butane (C ₄ H ₁₀ ) contained in city gas (raw fuel). , A pre-reformer for steam reforming to a fuel gas mainly containing methane (CH ₄ ), hydrogen, and CO, and is set to an operating temperature of several hundred degrees Celsius.

  The operating temperature of the fuel cell 26 is as high as several hundred degrees C. In the electrolyte / electrode assembly 36, methane in the fuel gas is reformed to obtain hydrogen and CO, and this hydrogen and CO are supplied to the anode electrode. Is done.

  The heat exchanger 86 includes an exhaust gas passage 94 for flowing a used reaction gas (hereinafter also referred to as exhaust gas) discharged from the fuel cell stack 28, and an air for flowing air to be heated in a counterflow with the exhaust gas. And a passage 96. The upstream side of the air passage 96 communicates with the air supply pipe 98, and the downstream side of the air passage 96 communicates with the oxidant gas supply communication hole 78 of the fuel cell stack 28.

  The evaporator 88 is provided with a raw fuel passage 100 and a water passage 102. The raw fuel passage 100 is connected to the raw fuel supply device 16, and the water passage 102 is connected to the water supply device 20. The oxidant gas supply device 18 is connected to the air supply pipe 98.

  The raw fuel supply device 16, the oxidant gas supply device 18, and the water supply device 20 are controlled by a control device 24, and a detector 106 that detects fuel gas is electrically connected to the control device 24. . For example, a commercial power source 108 (or a load, a secondary battery, or the like) is connected to the power conversion device 22 (see FIG. 2).

  As shown in FIGS. 1 and 2, the fuel cell system 10 includes a temperature sensor 110 that detects the temperature of the fuel cell stack 28, and the flow rate of raw fuel (fuel gas) supplied from the raw fuel supply device 16 to the evaporator 88. And a second flow rate sensor 112b for detecting the flow rate of air (oxidant gas) supplied from the oxidant gas supply device 18 to the heat exchanger 86. The temperature sensor 110, the first flow sensor 112a, and the second flow sensor 112b are connected to the control device 24.

  The operation of the fuel cell system 10 configured as described above will be described below.

As shown in FIGS. 1 and 2, under the driving action of the raw fuel supply device 16, for example, city gas (CH ₄ , C ₂ H ₆ , C ₃ H ₈ , C ₄ H ₁₀₎ is provided in the raw fuel passage 100. And other raw fuel is supplied. On the other hand, under the driving action of the water supply device 20, water is supplied to the water passage 102, and oxidant gas is supplied to the air supply pipe 98 via the oxidant gas supply device 18, for example, air Is supplied.

In the evaporator 88, steam is mixed with the raw fuel to obtain a mixed fuel, and this mixed fuel is supplied to the reformer 90. The mixed fuel is steam reformed in the reformer 90, and C ₂₊ hydrocarbons are removed (reformed) to obtain a reformed gas mainly composed of methane. This reformed gas is supplied to the fuel gas supply communication hole 40 of the fuel cell stack 28.

  On the other hand, when the air supplied from the air supply pipe 98 to the heat exchanger 86 moves along the air passage 96 of the heat exchanger 86, the air is heated between the exhaust gas that moves along the exhaust gas passage 94, which will be described later. Exchange is performed and preheated to the desired temperature. The air heated by the heat exchanger 86 is supplied to the oxidant gas supply communication hole 78 of the fuel cell stack 28.

  As shown in FIG. 5, the fuel gas moves in the fuel gas supply passage 76 provided in each fuel cell 26 while moving in the stacking direction (arrow A direction) along the fuel gas supply communication hole 40 of the fuel cell stack 28. Along the surface direction of the separator 38.

  The fuel gas is introduced into the fuel gas passage 50 from the fuel gas supply passage 76 through the fuel gas supply hole 48 formed in the clamping portion 46. The fuel gas supply hole 48 is set at a substantially central position of the anode electrode 34 of each electrolyte / electrode assembly 36. Therefore, the fuel gas is supplied from the fuel gas supply hole 48 to the approximate center of the anode electrode 34, and then moves along the fuel gas passage 50 toward the outer periphery of the anode electrode 34.

  On the other hand, the air supplied to the oxidant gas supply communication hole 78 flows in the direction of arrow B from between the inner peripheral end portion of the electrolyte / electrode assembly 36 and the inner peripheral end portion of the sandwiching portion 46, and the oxidant gas. It is sent to the passage 64. In the oxidant gas passage 64, air flows from the inner peripheral end portion (center portion of the separator 38) side of the cathode electrode 32 of the electrolyte / electrode assembly 36 toward the outer peripheral end portion (outer peripheral end portion side of the separator 38). To flow.

  Therefore, in the electrolyte / electrode assembly 36, the fuel gas is supplied from the center side of the electrode surface of the anode electrode 34 toward the peripheral end side, and in one direction (arrow B direction) of the electrode surface of the cathode electrode 32. Air is supplied in the direction. At that time, oxide ions move through the electrolyte 30 to the anode electrode 34, and power is generated by a chemical reaction.

  The exhaust gas mainly containing air after the power generation reaction discharged to the outer peripheral portion of each electrolyte / electrode assembly 36 is discharged from the fuel cell stack 28 through the exhaust gas passage 94 as an off gas.

  Next, the control method according to the first embodiment will be described below.

  First, the control method of the present invention includes a step of measuring at least a current output value of the fuel cell stack 28, an A / F value of the fuel cell stack 28, and a temperature of the fuel cell stack 28, and at least the current output value, Controlling the amount of fuel gas supplied to the fuel cell stack 28 based on either the A / F value or the temperature.

  Here, the current output value of the fuel cell stack 28 is detected from voltage × current. As will be described later, the target output value to be compared with the current output value is a fixed value, for example, when the target output value is set to the demand output value 1 kW, etc. Including the case where the output value is set within 950 W ± 5%. As a result, the current output value (902.5 W to 997.5 W) does not exceed the demand output value (1 kW) and can prevent reverse power flow.

  The A / F value is a ratio of the oxidant gas and the fuel gas supplied to the fuel cell stack 28, and A / F value = (oxidant gas) / (fuel gas) value. The range of the upper limit value and the lower limit value of the A / F value is set, for example, in the range of 3 to 30, the flow rate of the oxidant gas is detected by the second flow rate sensor 112b, and the flow rate of the fuel gas is 1 is detected by the flow sensor 112a.

  The range of the upper limit value and the lower limit value of the temperature of the fuel cell stack 28 is set to a range of 650 ° C. to 800 ° C., for example. The temperature of the fuel cell stack 28 is detected via the temperature sensor 110.

  Next, the control method according to the first embodiment measures a first step of setting a target output value of the fuel cell stack 28 or a predetermined range of the target output value, and a current output value of the fuel cell stack 28. A second step, a third step of measuring the A / F value of the fuel cell stack 28, a fourth step of measuring the temperature of the fuel cell stack 28, and the target output value or the target output value. A fifth step of comparing the predetermined range with the current output value, a sixth step of comparing the A / F value with an upper limit value or a lower limit value of the preset A / F value, A seventh step of comparing the temperature with a preset upper limit or lower limit of the temperature; an eighth step of maintaining the amount of fuel gas supplied to the fuel cell stack 28; and the fuel cell. Reduce the amount of fuel gas supplied to the stack 28 It has a ninth step of, a tenth step of increasing the amount of the fuel gas supplied to the fuel cell stack 28.

  Then, at least any of the eighth step, the ninth step, or the tenth step is performed based on the comparison result of at least the fifth step, the sixth step, or the seventh step.

  Concretely, it demonstrates along the flowchart shown in FIG. 6, and the setting conditions shown in FIG. In the first embodiment, the range of the upper limit value and the lower limit value of the A / F value is set to a range of 10-30.

  In the fuel cell system 10, a target output value (voltage × current) of the fuel cell stack 28 or a predetermined range of the target output value is set (step S1). Next, the process proceeds to step S2, and the output value is adjusted so that the voltage of the fuel cell stack 28 becomes the target voltage.

  The control device 24 measures the current output value from the voltage and current actually output by the fuel cell stack 28 (step S3). Then, it is determined whether or not the current output value is equal to the target output value or within a predetermined range of the target output value (hereinafter also simply referred to as the target output value) (step S4). When it is determined that the current output value is equal to or within the predetermined range of the target output value (YES in step S4), the process proceeds to step S5, and the fuel gas supplied to the fuel cell stack 28 The amount of fuel gas is maintained without correcting the amount. Furthermore, it progresses to step S6 and is repeated until the driving | operation of the fuel cell system 10 is complete | finished.

  If it is determined in step S4 that the current output value is not equal to the target output value or not within the predetermined range of the target output value (NO in step S4), the process proceeds to step S7, where the current output value is the target output value. It is determined whether the output value is exceeded or the target output value is over a predetermined range. If it is determined that the current output value exceeds the target output value or exceeds the predetermined range of the target output value (YES in step S7), the process proceeds to step S8, and the A / F value is set in advance. It is determined whether or not the A / F value is equal to or less than an upper limit (30).

  If it is determined that the A / F value is less than or equal to the preset upper limit of the A / F value (YES in step S8), the process proceeds to step S9, and the temperature of the fuel cell stack 28 is set in advance. It is determined whether the temperature is equal to or higher than a lower limit value (650 ° C.). If it is determined that the temperature of the fuel cell stack 28 is equal to or higher than a preset lower limit value of the temperature (YES in step S9), the process proceeds to step S10 to supply the fuel gas supplied to the fuel cell stack 28. Correction is performed to reduce the amount of.

  On the other hand, if it is determined in step S7 that the current output value is less than the target output value or less than the predetermined range of the target output value (NO in step S7), the process proceeds to step S11, where the A / F value is Then, it is determined whether or not the value is equal to or greater than a preset lower limit (10) of the A / F value. If it is determined that the A / F value is greater than or equal to the preset lower limit of the A / F value (YES in step S11), the process proceeds to step S12, and the temperature of the fuel cell stack 28 is set in advance. It is determined whether or not the temperature is not more than the upper limit value (800 ° C.).

  If it is determined that the temperature of the fuel cell stack 28 is equal to or lower than the preset upper limit value of the temperature (YES in step S12), the process proceeds to step S13, and the fuel gas supplied to the fuel cell stack 28 Corrections are made to increase the amount.

  If it is determined in step S8 that the A / F value exceeds the preset upper limit of the A / F value (NO in step S8), the process proceeds to step S5. If it is determined in step S9 that the temperature of the fuel cell stack 28 is lower than the preset lower limit value of the temperature (NO in step S9), the process proceeds to step S5. Similarly, when it is determined in step S11 that the A / F value is less than the preset lower limit value of the A / F value (NO in step S11), the process proceeds to step S5, and in step S12. If it is determined that the temperature of the fuel cell stack 28 exceeds the preset upper limit value of the temperature (NO in step S12), the process proceeds to step S5.

  In this case, in the first embodiment, the first step of setting the target output value of the fuel cell stack 28 or a predetermined range of the target output value, and the second step of measuring the current output value of the fuel cell stack 28 are performed. A step, a third step of measuring the A / F value of the fuel cell stack 28, a fourth step of measuring the temperature of the fuel cell stack 28, and the target output value or a predetermined range of the target output value A fifth step of comparing the current output value with the current output value, a sixth step of comparing the A / F value with a preset upper or lower limit value of the A / F value, and the temperature A seventh step of comparing the preset upper limit value or lower limit value of the temperature, an eighth step of maintaining the amount of fuel gas supplied to the fuel cell stack 28, and the fuel cell stack 28 Reducing the amount of fuel gas supplied; And step, and a tenth step of increasing the amount of the fuel gas supplied to the fuel cell stack 28. Then, at least one of the eighth step, the ninth step, and the tenth step is performed based on the comparison result of at least the fifth step, the sixth step, or the seventh step.

  For this reason, the fuel cell 26 has a flat plate shape and adopts a sealless structure. Therefore, in the anode electrode 34 constituting the fuel cell 26, the anode electrode 34 is formed by the wrapping of the oxidant gas due to fuel depletion. Oxidation can be prevented, and deterioration of the anode electrode 34 can be reliably prevented.

  Further, in the cathode electrode 32 constituting the fuel cell 26, it is possible to prevent the cathode electrode 32 from being reduced due to the flow of fuel gas due to the exhaustion of air, and to prevent the cathode electrode 32 from being deteriorated satisfactorily. Is possible.

  Furthermore, in the fuel cell stack 28, carbon deposition due to insufficient heat, a decrease in power generation efficiency, or evaporation and insufficient reforming is suppressed, while a surplus heat, a decrease in power generation efficiency or a high temperature of the fuel cell constituent members is suppressed. As a result, the durability and life of the fuel cell system 10 are improved, and there is an effect that there is no possibility of impairing heat self-supporting.

  When it is determined in the fifth step that the current output value of the fuel cell stack 28 is equal to or within the predetermined range of the target output value (YES in step S4), the eighth output A process (step S5) is performed. Accordingly, since the fuel cell stack 28 maintains the fuel supply amount (without fuel correction) based on the current output value, it is possible to perform an appropriate operation by causing the current output value to follow the target output value.

  Furthermore, in the fifth step, it is determined that the current output value exceeds the target output value or exceeds the predetermined range of the target output value (YES in step S7), and A / It is determined that the F value is less than or equal to the upper limit value of the preset A / F value (YES in step S8), and in the seventh step, the temperature is greater than or equal to the lower limit value of the preset temperature. When it is determined that there is (YES in step S9), the ninth step (step S10) is performed.

  Thus, the fuel supply amount reduction process is performed based on the current output value, A / F value, and temperature of the fuel cell stack 28. Therefore, in the anode electrode 34 constituting the fuel cell 26, the anode electrode 34 can be prevented from being oxidized due to the oxidant gas flowing around due to fuel depletion, and the anode electrode 34 can be prevented from deteriorating. Is possible. On the other hand, in the fuel cell stack 28, carbon deposition due to insufficient heat, a decrease in power generation efficiency, or evaporation and insufficient reforming is suppressed. As a result, the durability and life of the fuel cell system 10 are improved, and there is no risk of impairing heat self-supporting.

  In the fifth step, it is determined that the current output value exceeds the target output value or exceeds the predetermined range of the target output value (YES in step S7), and in the sixth step, A / F When it is determined that the value exceeds the preset upper limit of the A / F value (NO in step S8), the eighth step (step S5) is performed.

  As described above, the fuel supply amount is maintained based on the current output value and the A / F value of the fuel cell stack 28. Therefore, in the anode electrode 34, it is possible to prevent the anode electrode 34 from being oxidized due to the oxidant gas flowing around due to fuel depletion, and it is possible to prevent the anode electrode 34 from being deteriorated. For this reason, the durability and life of the fuel cell system 10 are improved.

  Further, in the fifth step, it is determined that the current output value exceeds the target output value or exceeds the predetermined range of the target output value (YES in step S7), and in the sixth step, A / F It is determined that the value is equal to or lower than the upper limit value of the preset A / F value (YES in step S8), and the temperature is lower than the lower limit value of the preset temperature in the seventh step. Is determined (NO in step S9), the eighth step (step S5) is performed.

  Thus, the fuel supply amount is maintained based on the current output value, A / F value, and temperature of the fuel cell stack 28. Therefore, in the anode electrode 34, it is possible to prevent the anode electrode 34 from being oxidized due to the oxidant gas flowing around due to fuel depletion, and it is possible to prevent the anode electrode 34 from being deteriorated. On the other hand, in the fuel cell stack 28, carbon deposition due to insufficient heat, a decrease in power generation efficiency, or evaporation and insufficient reforming is suppressed. As a result, the durability and life of the fuel cell system 10 are improved, and there is no risk of impairing heat self-supporting.

  Furthermore, in the fifth step, it is determined that the current output value is less than the target output value or less than the predetermined range of the target output value (NO in step S7), and in the sixth step, A / It is determined that the F value is equal to or higher than the lower limit value of the preset A / F value (YES in step S11), and the temperature is equal to or lower than the upper limit value of the preset temperature in the seventh step. When it is determined that there is (YES in step S12), the tenth step (step S13) is performed.

  As described above, the fuel supply amount increasing process is performed based on the current output value, A / F value, and temperature of the fuel cell stack 28. For this reason, the cathode electrode 32 can prevent the cathode electrode 32 from being reduced due to the inflow of fuel gas due to the exhaustion of air, and the cathode electrode 32 can be prevented from deteriorating. On the other hand, in the fuel cell stack 28, excess heat, reduction in power generation efficiency, or oxidation of the separator 38 due to high temperature of the separator 38 and the electrolyte / electrode assembly 36, aggregation of the electrolyte / electrode assembly 36, deterioration of the reforming catalyst. Is suppressed. As a result, the durability and life of the fuel cell system 10 are improved, and there is no risk of impairing heat self-supporting.

  In the fifth step, it is determined that the current output value is less than the target output value or less than the predetermined range of the target output value (NO in step S7), and in the sixth step, A / F When it is determined that the value is less than the preset lower limit of the A / F value (NO in step S11), the eighth step (step S5) is performed.

  As described above, the fuel supply amount is maintained based on the current output value and the A / F value of the fuel cell stack 28. Therefore, the cathode electrode 32 can prevent the cathode electrode 32 from being reduced due to the inflow of fuel gas due to the exhaustion of air, and can prevent the cathode electrode 32 from deteriorating. For this reason, the durability and life of the fuel cell system 10 are improved.

  Further, in the fifth step, it is determined that the current output value is less than the target output value or less than the predetermined range of the target output value (NO in step S7), and in the sixth step, A / F It is determined that the value is equal to or greater than the lower limit value of the preset A / F value (YES in step S11), and in the seventh step, the temperature exceeds the upper limit value of the preset temperature. When it is determined that there is (No in step S12), the eighth step (step S5) is performed.

  Thus, the fuel supply amount is maintained based on the current output value, A / F value, and temperature of the fuel cell stack 28. As a result, the cathode electrode 32 can prevent the cathode electrode 32 from being reduced by the flow of fuel gas due to the exhaustion of air, and the cathode electrode 32 can be prevented from deteriorating. On the other hand, in the fuel cell stack 28, excess heat, reduction in power generation efficiency, or oxidation of the separator 38 due to high temperature of the separator 38 and the electrolyte / electrode assembly 36, aggregation of the electrolyte / electrode assembly 36, deterioration of the reforming catalyst. Is suppressed. Therefore, the durability and life of the fuel cell system 10 are improved, and there is no risk of impairing thermal independence.

  Furthermore, the fuel cell 26 is a solid oxide fuel cell 26. For this reason, the fuel cell 26 is a high-temperature fuel cell that generates a large amount of heat, and can further improve the durability and life of the fuel cell system 10.

  The solid oxide fuel cell 26 is a flat solid oxide fuel cell 26 in which an electrolyte / electrode assembly 36 is sandwiched between separators 38. Accordingly, the fuel cell system 10 can be applied particularly well to the sealless fuel cell 26, and the durability and life of the fuel cell system 10 can be further improved.

  FIG. 8 is an exploded perspective view of the fuel cell 120 constituting the fuel cell system to which the control method according to the second embodiment of the present invention is applied. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the fuel cell 120, a plurality of, for example, two electrolyte / electrode assemblies 36 are sandwiched between the first separator 38a and the second separator 38b. The first separator 38a and the second separator 38b are configured by reversing the same-shaped separator structure by 180 ° from each other.

  The 1st separator 38a has the 1st plate 122a and the 2nd plate 124a which consist of sheet metals, such as stainless steel, for example. The first plate 122a and the second plate 124a are joined to each other by diffusion bonding, laser welding, brazing, or the like.

  The first plate 122a is formed in a substantially flat plate shape, and has a fuel gas supply part 42 in which a fuel gas supply communication hole 40 for supplying fuel gas along the stacking direction (arrow A direction) is formed. First sandwiching portions 46a and 46b are integrally provided via two first bridge portions 44a and 44b extending outward from the fuel gas supply portion 42.

  The first sandwiching portions 46a and 46b are set to have substantially the same dimensions as the electrolyte / electrode assembly 36, and a plurality of protrusions 58a and 46b are formed on the surfaces of the first sandwiching portions 46a and 46b in contact with the anode electrode 34, respectively. 58b is provided. The protrusions 58a and 58b form fuel gas passages 50a and 50b for supplying fuel gas along the electrode surface of the anode electrode 34, and have a current collecting function. Fuel gas supply holes 48a and 48b for supplying fuel gas toward the substantially central portion of the anode electrode 34 are formed in the substantially central portions of the first sandwiching portions 46a and 46b.

  The second plate 124a has a fuel gas supply part 126 in which the fuel gas supply communication hole 40 is formed. First sandwiching portions 130a and 130b are integrally provided via two first bridge portions 128a and 128b extending outward from the fuel gas supply portion 126. A circumferential convex portion 132 that goes around the outer periphery of the second plate 124 a and protrudes toward the first plate 122 a is provided, and the first plate 122 a is joined to the circumferential convex portion 132.

  The surfaces of the fuel gas supply part 126, the first bridge parts 128a and 128b, and the first sandwiching parts 130a and 130b that face the first plate 122a are in contact with the first plate 122a and have a function of preventing crushing against loads in the stacking direction. A plurality of protrusions 134 are formed.

  Fuel gas supply passages 76a and 76b communicating with the fuel gas supply communication hole 40 are formed between the first bridge portions 44a and 128a and between the first bridge portions 44b and 128b. The fuel gas supply passages 76a and 76b communicate with the fuel gas supply holes 48a and 48b via the fuel gas filling chambers 136a and 136b formed between the first holding parts 46a and 130a and between the first holding parts 46b and 130b. To do.

  The second separator 38b is configured in the same shape as the first separator 38a, and includes a first plate 122b and a second plate 124b corresponding to the first plate 122a and the second plate 124a. The first plate 122b and the second plate 124b include oxidant gas supply units 140 and 142 in which oxidant gas supply communication holes 138 for supplying an oxidant gas along the stacking direction are formed.

  The first plate 122b and the second plate 124b are connected to the second sandwiching portions 148a, 148b, and 150a through two second bridge portions 144a, 144b, 146a, and 146b that protrude outward from the oxidizing gas supply portions 140 and 142, respectively. , 150b are integrally provided.

  An oxidant gas passage 64a for supplying an oxidant gas along the electrode surface of the cathode electrode 32 through a plurality of protrusions 58a and 58b is provided on the surface of the second sandwiching part 148a and 148b that contacts the cathode electrode 32. , 64b are formed. Oxidant gas supply holes 152a and 152b for supplying an oxidant gas toward the substantially central part of the cathode electrode 32 are formed in the substantially central parts of the second sandwiching parts 148a and 148b.

  In the second plate 124b, oxidant gas supply passages 154a and 154b communicated with the oxidant gas supply communication hole 138 by joining the first plate 122b are provided between the second bridge portions 144a and 146a and the second bridge. It is formed correspondingly between the portions 144b and 146b.

  In the second sandwiching portions 150a and 150b, oxidant gas filling chambers 156a and 156b communicating with the oxidant gas supply communication hole 138 and the oxidant gas supply passages 154a and 154b are formed.

  As shown in FIG. 10, between each fuel cell 120, a first insulating seal 80a for sealing the fuel gas supply communication hole 40 and a second insulating seal 80b for sealing the oxidant gas supply communication hole 138 are provided. Are provided. A plurality of fuel cells 120 are stacked in the direction of arrow A to form a fuel cell stack 160.

  In the fuel cell stack 160 configured as described above, the fuel gas is supplied to the fuel gas supply communication hole 40 of each fuel cell 120 and the air is supplied to the oxidant gas supply communication hole 138.

  The fuel gas is introduced into the fuel gas supply passages 76a and 76b formed in the first separator 38a constituting each fuel cell 120 while moving in the stacking direction (arrow A direction) (see FIGS. 9 and 10).

  The fuel gas moves between the first bridge portions 44a and 128a and between the first bridge portions 44b and 128b along the fuel gas supply passages 76a and 76b, and is once filled in the fuel gas filling chambers 136a and 136b. Further, the fuel gas is introduced into the fuel gas passages 50a and 50b from the fuel gas supply holes 48a and 48b. At that time, the fuel gas supply holes 48 a and 48 b are set at a substantially central position of the anode electrode 34 of each electrolyte / electrode assembly 36. Therefore, the fuel gas moves from the substantial center of the anode electrode 34 toward the outer peripheral portion of the anode electrode 34 along the fuel gas passages 50a and 50b.

  On the other hand, the air supplied to the oxidant gas supply communication hole 138 moves along the oxidant gas supply passages 154a and 154b formed between the second bridge portions 144a and 146a and between the second bridge portions 144b and 146b. The oxidant gas filling chambers 156a and 156b are once filled. Further, the oxidant gas is introduced into the oxidant gas passages 64a and 64b from the oxidant gas supply holes 152a and 152b.

  The oxidant gas supply holes 152 a and 152 b are set at substantially the center position of the cathode electrode 32 of each electrolyte / electrode assembly 36. Therefore, the oxidant gas moves from the substantially central position of the cathode electrode 32 toward the outer peripheral portion along the oxidant gas passages 64a and 64b.

  As a result, in the electrolyte / electrode assembly 36, fuel gas is supplied from the center side of the electrode surface of the anode electrode 34 toward the peripheral end portion side, and at the peripheral end portion side from the center side of the electrode surface of the cathode electrode 32. Air is supplied toward. At that time, oxide ions move through the electrolyte 30 to the anode electrode 34, and power is generated by a chemical reaction.

  The spent fuel gas that has moved through the fuel gas passages 50a and 50b and the spent air that has moved through the oxidant gas passages 64a and 64b are led out to the exhaust gas passage 82 from the outer periphery of each electrolyte / electrode assembly 36, It is mixed in the exhaust gas passage 82 and discharged as a relatively high temperature exhaust gas.

  In the second embodiment, similarly to the first embodiment, the control is performed according to the flowchart shown in FIG. In that case, in 2nd Embodiment, the range of the upper limit of A / F value and a lower limit is set to the range of 3-28. This is because the utilization rate of air is higher than that of the first embodiment. Thereby, the second embodiment can obtain the same effects as those of the first embodiment.

1 is a schematic configuration explanatory diagram showing a mechanical circuit of a fuel cell system to which a control method according to a first embodiment of the present invention is applied. It is a circuit diagram of the fuel cell system. It is a disassembled perspective explanatory drawing of the fuel cell which comprises the said fuel cell system. It is a partially exploded perspective view showing the gas flow state of the fuel cell. 2 is a cross-sectional explanatory view of the fuel cell. FIG. It is a flowchart explaining the said control method. It is explanatory drawing of the various setting conditions in the said control method. It is a disassembled perspective explanatory drawing of the fuel cell which comprises the fuel cell system with which the control method concerning the 2nd Embodiment of this invention is applied. It is a partially exploded perspective view showing the gas flow state of the fuel cell. 2 is a cross-sectional explanatory view of the fuel cell. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 12 ... Fuel cell module 16 ... Raw fuel supply device 18 ... Oxidant gas supply device 20 ... Water supply device 22 ... Power converter 24 ... Control device 26, 120 ... Fuel cell 30 ... Electrolyte 32 ... Cathode electrode 34 ... Anode electrode 36 ... Electrolyte / electrode assembly 38, 38a, 38b ... Separator 40 ... Fuel gas supply communication hole 50, 50a, 50b ... Fuel gas passage 64, 64a, 64b ... Oxidant gas passage 86 ... Heat exchanger 88 ... Evaporator 90 ... Reformer 110 ... Temperature sensors 112a, 112b ... Flow sensor

Claims (11)

A control method for a fuel cell system, comprising: a fuel cell stack in which a plurality of fuel cells that generate power by an electrochemical reaction between a fuel gas and an oxidant gas are stacked; and a control device,
Measuring at least a current output value of the fuel cell stack, an A / F value of the fuel cell stack, and a temperature of the fuel cell stack;
Controlling the amount of the fuel gas supplied to the fuel cell stack based on at least one of the current output value, the A / F value, or the temperature;
A control method for a fuel cell system, comprising: A control method for a fuel cell system, comprising: a fuel cell stack in which a plurality of fuel cells that generate power by an electrochemical reaction between a fuel gas and an oxidant gas are stacked; and a control device,
A first step of setting a target output value of the fuel cell stack or a predetermined range of the target output value;
A second step of measuring a current output value of the fuel cell stack;
A third step of measuring the A / F value of the fuel cell stack;
A fourth step of measuring the temperature of the fuel cell stack;
A fifth step of comparing the target output value or a predetermined range of the target output value with the current output value;
A sixth step of comparing the A / F value with a preset upper limit value or lower limit value of the A / F value;
A seventh step of comparing the temperature with a preset upper limit value or lower limit value of the temperature;
An eighth step of maintaining the amount of the fuel gas supplied to the fuel cell stack;
A ninth step of reducing the amount of the fuel gas supplied to the fuel cell stack;
A tenth step of increasing the amount of the fuel gas supplied to the fuel cell stack;
Have
Based on at least the comparison result of any of the fifth step, the sixth step, and the seventh step, at least one of the eighth step, the ninth step, and the tenth step is performed. A control method for a fuel cell system, comprising:   3. The control method according to claim 2, wherein when it is determined in the fifth step that the current output value is equal to or within a predetermined range of the target output value, the eighth step is performed. A control method for a fuel cell system, comprising: 4. The control method according to claim 2, wherein, in the fifth step, it is determined that the current output value exceeds the target output value or exceeds a predetermined range of the target output value, and
In the sixth step, the A / F value is determined to be less than or equal to a preset upper limit value of the A / F value, and
When it is determined in the seventh step that the temperature is equal to or higher than a preset lower limit value of the temperature,
A control method for a fuel cell system, wherein the ninth step is performed. The control method according to any one of claims 2 to 4, wherein in the fifth step, the current output value is determined to be over the target output value or over a predetermined range of the target output value, and,
In the sixth step, when it is determined that the A / F value exceeds the preset upper limit value of the A / F value,
A control method for a fuel cell system, wherein the eighth step is performed. In the control method according to any one of claims 2 to 5, in the fifth step, it is determined that the current output value exceeds the target output value or exceeds a predetermined range of the target output value. and,
In the sixth step, the A / F value is determined to be less than or equal to a preset upper limit value of the A / F value, and
In the seventh step, when it is determined that the temperature is less than a preset lower limit value of the temperature,
A control method for a fuel cell system, wherein the eighth step is performed. In the control method according to any one of claims 2 to 6, in the fifth step, it is determined that the current output value is less than the target output value or less than a predetermined range of the target output value. and,
In the sixth step, the A / F value is determined to be greater than or equal to a preset lower limit value of the A / F value, and
In the seventh step, when it is determined that the temperature is equal to or lower than a preset upper limit value of the temperature,
A control method for a fuel cell system, wherein the tenth step is performed. In the control method according to any one of claims 2 to 7, in the fifth step, it is determined that the current output value is less than the target output value or less than a predetermined range of the target output value. and,
In the sixth step, when it is determined that the A / F value is less than a preset lower limit value of the A / F value,
A control method for a fuel cell system, wherein the eighth step is performed. The control method according to any one of claims 2 to 8, wherein in the fifth step, the current output value is determined to be less than the target output value or less than a predetermined range of the target output value, and,
In the sixth step, the A / F value is determined to be greater than or equal to a preset lower limit value of the A / F value, and
When it is determined in the seventh step that the temperature exceeds the preset upper limit value of the temperature,
A control method for a fuel cell system, wherein the eighth step is performed.   10. The control method according to claim 1, wherein the fuel cell is a solid oxide fuel cell.   11. The control method according to claim 10, wherein the solid oxide fuel cell is a flat plate solid oxide fuel cell in which an electrolyte / electrode assembly is sandwiched between separators.

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