JP5299207B2 - FUEL CELL SYSTEM AND METHOD FOR OPERATING FUEL CELL SYSTEM - Google Patents

Description

  The present invention relates to a fuel cell system including a fuel cell and a method for operating the fuel cell system.

  A fuel cell system including a fuel cell is generally a system that obtains electric energy using hydrogen and oxygen as fuel. Since this fuel cell system is excellent in terms of environment and can realize high energy efficiency, it has been widely developed as a future energy supply system.

  Hydrogen consumed in the fuel cell is generated, for example, in a reformer. In the reformer, hydrogen is generated by a steam reforming reaction between raw fuel such as hydrocarbon and reformed water. Since the steam reforming reaction is a chemical reaction process, the amount of generated hydrogen becomes unstable when the supply amounts of raw fuel and reforming water supplied to the reformer become unstable. Therefore, in the technique of Patent Document 1, a technique for controlling the amount of water supplied for the reformer based on the amount of water supplied detected by the water flow rate detection unit is disclosed.

JP 2008-247688 A

  However, the technique of Patent Document 1 requires a flow meter that detects the water flow rate. For this reason, if an accuracy defect, a failure, or the like occurs in the flow meter, an incorrect amount of water is detected.

  The present invention has been made in view of the above problems, and a fuel cell system capable of optimizing and controlling the supply amounts of raw fuel and reformed water without using a detector such as a flow meter for detecting a water flow rate. And it aims at providing the operating method of a fuel cell system.

  A fuel cell system according to the present invention includes a reformer that generates a fuel gas by a steam reforming reaction, a fuel cell that generates power using an oxidant gas and a fuel gas generated by the reformer, and a fuel cell A combustion chamber that burns fuel off-gas to heat the reformer, a temperature sensor that directly or indirectly detects the temperature of the reformer, and a ratio of the amount of reformed water supplied to the raw fuel to the reformer A control unit that controls the supply amount ratio when the temperature rise detected by the temperature sensor changes from positive to negative when the ratio of the reforming water supply amount to the raw fuel supply amount is increased. Based on the above, the supply amount ratio is controlled. In the fuel cell system according to the present invention, the supply amounts of raw fuel and reforming water can be optimized and controlled without using a detector such as a flow meter for detecting the water flow rate.

  The temperature sensor may be disposed in the combustion chamber. In this case, when the heat capacity of the reformer is larger than the heat capacity of the gas in the combustion chamber, it becomes easy to detect a temperature change.

  The control unit may set the supply amount ratio when the temperature increase detected by the temperature sensor changes from positive to negative when the ratio of the supply amount of reforming water to the supply amount of raw fuel is increased, as the control target value. In this case, it is possible to optimize and control the supply amounts of the raw fuel and reforming water even if variations of each device, aging, etc. occur.

  Even when the control unit increases the ratio of the supply amount of the reforming water to the supply amount of the raw fuel at the time of starting the fuel cell, the control unit obtains the supply amount ratio when the detected temperature rise of the temperature sensor changes from positive to negative. Good. In this case, the ratio of the supply amount of the reforming water to the supply amount of the raw fuel can be optimized every time the fuel cell is started.

  The control unit may obtain a supply amount ratio in a case where the temperature rise detected by the temperature sensor changes from positive to negative by increasing a ratio of the supply amount of the reforming water to the supply amount of the raw fuel in a predetermined time period. . In this case, the ratio of the supply amount of reforming water to the supply amount of raw fuel can be optimized in a predetermined time period.

  Another fuel cell system according to the present invention includes a reformer that generates a fuel gas by a steam reforming reaction, a fuel cell that generates power using an oxidant gas and a fuel gas generated by the reformer, and a fuel cell. A combustion chamber for burning the fuel off-gas in the cell to heat the reformer, a temperature sensor for detecting the temperature in the combustion chamber, and a controller for controlling the ratio of the amount of reformed water supplied to the raw fuel to the reformer; The control unit supplies the water based on the supply amount ratio when the temperature rise detected by the temperature sensor changes from positive to negative when the ratio of the supply amount of the reforming water to the supply amount of the raw fuel is increased. The quantity ratio is controlled. In another fuel cell system according to the present invention, the supply amounts of raw fuel and reforming water can be optimized and controlled without using a detector such as a flow meter for detecting the water flow rate.

  An operation method of a fuel cell system according to the present invention includes a reformer that generates a fuel gas by a steam reforming reaction, a fuel cell that generates electric power from an oxidant gas and a fuel gas generated by the reformer, and a fuel And a combustion chamber that heats the reformer by burning fuel off-gas of the battery cell, and a temperature detection step for directly or indirectly detecting the temperature of the reformer; A control step of controlling the supply amount ratio based on the supply amount ratio when the temperature increase detected in the temperature detection step changes from positive to negative when the ratio of the reforming water supply to the raw fuel is increased; It is characterized by including. In the operation method of the fuel cell system according to the present invention, the supply amounts of the raw fuel and the reforming water can be optimized and controlled without using a detector such as a flow meter for detecting the water flow rate.

  The temperature detection step may be a step of detecting the temperature in the combustion chamber. In this case, when the heat capacity of the reformer is larger than the heat capacity of the gas in the combustion chamber, it becomes easy to detect a temperature change.

  In the control step, when the ratio of the supply amount of reforming water to the supply amount of raw fuel is increased, the supply amount ratio when the temperature increase detected in the temperature detection step changes from positive to negative is set as the control target value. It may be a step. In this case, it is possible to optimize and control the supply amounts of the raw fuel and reforming water even if variations of each device, aging, etc. occur.

  The control step is to increase the ratio of the supply amount of reforming water to the supply amount of raw fuel at the start of the fuel cell, and the supply amount ratio when the temperature rise detected in the temperature detection step changes from positive to negative It may be a step for obtaining. In this case, the ratio of the supply amount of the reforming water to the supply amount of the raw fuel can be optimized every time the fuel cell is started.

  The control step increases the ratio of the supply amount of the reforming water to the supply amount of the raw fuel at a predetermined time period, and determines the supply amount ratio when the temperature rise detected in the temperature detection step changes from positive to negative. It may be a step of obtaining. In this case, the ratio of the supply amount of reforming water to the supply amount of raw fuel can be optimized in a predetermined time period.

  Another operating method of the fuel cell system according to the present invention includes a reformer that generates a fuel gas by a steam reforming reaction, a fuel cell that generates electric power from the oxidant gas and the fuel gas generated by the reformer, And a combustion chamber for heating the reformer by burning the fuel off-gas of the fuel cell, a temperature detection step for detecting the temperature in the combustion chamber, and reforming of the raw fuel to the reformer And a control step for controlling the supply amount ratio based on the supply amount ratio when the temperature rise detected in the temperature detection step changes from positive to negative when the water supply amount ratio is increased. It is what. In another operation method of the fuel cell system according to the present invention, the supply amounts of the raw fuel and the reformed water can be optimized and controlled without using a detector such as a flow meter for detecting the water flow rate.

  According to the present invention, there are provided a fuel cell system and a fuel cell system operating method capable of optimizing and controlling the supply amounts of raw fuel and reformed water without using a detector such as a flow meter for detecting the water flow rate. can do.

1 is a schematic diagram illustrating an overall configuration of a fuel cell system according to Example 1. FIG. It is a fragmentary perspective view containing the cross section of a fuel cell. It is a perspective view which shows a fuel cell stack apparatus. It is a figure which shows the temperature change of a combustion chamber when supply of reforming water is started and the amount of reforming water supply is kept constant at S / C ratio = 2.5. It is a figure which shows the differential value of the temperature of a combustion chamber when the S / C ratio is made to increase gradually, and the temperature of a combustion chamber. It is a figure which shows an example of the flowchart performed when detecting an optimal S / C ratio. FIG. 3 is a schematic diagram illustrating an overall configuration of a fuel cell system according to Example 2.

  Hereinafter, the best mode for carrying out the present invention will be described.

(Example 1)
FIG. 1 is a schematic diagram illustrating an overall configuration of a fuel cell system 100 according to Example 1. As illustrated in FIG. As shown in FIG. 1, the fuel cell system 100 includes a control unit 10, a raw fuel supply unit 20, a reforming water supply unit 30, an oxidant gas supply unit 40, a reformer 50, a combustion chamber 60, and a fuel cell 70. , A temperature sensor 81, a glow plug 82, and a heat exchanger 90 are provided.

  The control unit 10 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and the like. The raw fuel supply unit 20 includes a fuel pump for supplying raw fuel such as hydrocarbons to the reformer 50. The reforming water supply unit 30 stores the reforming water tank 31 that stores the reforming water necessary for the steam reforming reaction in the reformer 50, and the reforming water stored in the reforming water tank 31 is supplied to the reformer 50. A reforming water pump 32 and the like for supply are included.

  The oxidant gas supply unit 40 includes an air pump or the like for supplying an oxidant gas such as air to the cathode 71 of the fuel cell 70. The reformer 50 includes a vaporization unit 51 for vaporizing reformed water and a reforming unit 52 for generating fuel gas by a steam reforming reaction. The fuel cell 70 has a structure in which an electrolyte 73 is sandwiched between a cathode 71 and an anode 72. The temperature sensor 81 is a sensor that detects temperature, and is disposed inside the combustion chamber 60. The glow plug 82 is an ignition glow plug for igniting combustible components, and is disposed inside the combustion chamber 60.

  Next, specific configuration examples of the reformer 50, the combustion chamber 60, and the fuel battery cell 70 will be described with reference to FIGS. FIG. 2 is a partial perspective view including a cross section of the fuel battery cell 70. As shown in FIG. 2, the fuel battery cell 70 has an overall shape of a flat plate column. A plurality of fuel gas passages 12 penetrating along the axial direction (longitudinal direction) are formed in the conductive support 11 having gas permeability. A fuel electrode 13, a solid electrolyte 14, and an oxygen electrode 15 are laminated in this order on one plane on the outer peripheral surface of the conductive support 11. On the other plane facing the oxygen electrode 15, an interconnector 17 is provided via a bonding layer 16, and a P-type semiconductor layer 18 for reducing contact resistance is provided thereon. The fuel electrode 13 functions as the anode 72 in FIG. 1, and the oxygen electrode 15 functions as the cathode 71 in FIG.

By supplying the reformed gas containing hydrogen to the fuel gas passage 12, hydrogen is supplied to the fuel electrode 13. On the other hand, oxygen is supplied to the oxygen electrode 15 by supplying an oxidant gas containing oxygen around the fuel cell 70. As a result, the following electrode reactions occur in the oxygen electrode 15 and the fuel electrode 13 to generate power. The power generation reaction is performed at 600 ° C. to 1000 ° C., for example.
Oxygen electrode: 1 / 2O ₂ + 2e ⁻ → O ²⁻ (solid electrolyte)
Fuel electrode: O ²⁻ (solid electrolyte) + H ₂ → H ₂ O + 2e ⁻

The material of the oxygen electrode 15 has oxidation resistance and is porous so that gaseous oxygen can reach the interface with the solid electrolyte 14. The solid electrolyte 14 has a function of moving oxygen ions O ²⁻ from the oxygen electrode 15 to the fuel electrode 13. The solid electrolyte 14 is composed of an oxygen ion conductive oxide. Further, since the solid electrolyte 14 physically separates the fuel gas and the oxidant gas, the solid electrolyte 14 is stable and dense in the oxidizing / reducing atmosphere. The fuel electrode 13 is made of a material that is stable in a reducing atmosphere and has an affinity for hydrogen. The interconnector 17 is provided to electrically connect the fuel cells 70 in series, and is dense to physically separate the fuel gas and the oxidant gas.

For example, the oxygen electrode 15 is formed of a lanthanum cobaltite-based perovskite complex oxide having high conductivity of both electrons and ions. The solid electrolyte 14 is formed of ZrO ₂ (YSZ) containing Y ₂ O ₃ having high ion conductivity. The fuel electrode 13 is formed of a mixture of Ni having high electronic conductivity and ZrO ₂ (YSZ) containing Y ₂ O ₃ . The interconnector 17 is made of LaCrO ₃ or the like that has a high electronic conductivity and in which an alkaline earth oxide is dissolved. These materials are preferably close in thermal expansion coefficient.

  FIG. 3A is a perspective view showing the fuel cell stack device 200. FIG. 3B is a perspective view showing the oxidant gas introduction member 210 of the fuel cell stack apparatus 200 extracted. As shown in FIG. 3A, in the fuel cell stack apparatus 200, two sets of fuel cell stacks 230 (fuel cell 70) are arranged on the manifold 220 so that their stacking directions are substantially parallel to each other. They are arranged in parallel. The fuel cell stack 230 has a structure in which a plurality of solid oxide fuel cells 70 are stacked.

  In the manifold 220 in FIG. 3A, a hole communicating with the fuel gas passage 12 of each fuel cell 70 is formed. Thereby, the fuel gas flowing through the manifold 220 flows into the fuel gas passage 12. The reformer 50 is disposed on the opposite side of the manifold 220 of the fuel cell stack 230. For example, the reformer 50 has a structure that extends in the stacking direction of one fuel cell stack 230, is folded at one end, and extends in the stacking direction of the other fuel cell stack 230.

  Further, as shown in FIG. 3B, an oxidant gas introduction member 210 is disposed between the fuel cell stacks 230. The oxidant gas introduction member 210 has a space for the oxidant gas to flow. A hole 211 is formed at the end of the oxidant gas introduction member 210 on the manifold 220 side. Thereby, the oxidant gas flows outside each fuel cell 70. Electric power is generated in the fuel cell 70 when the fuel gas flows through the fuel gas passage 12 of the fuel cell 70 and the oxidant gas flows outside the fuel cell 70.

  The fuel gas (fuel off gas) after being used for power generation in the fuel cell 70 and the oxidant gas (oxidant off gas) after being used for power generation are the ends of the fuel cells 70 opposite to the manifold 220. Join at the part. Since the fuel off-gas contains a combustible material such as unburned hydrogen, the fuel off-gas burns using oxygen contained in the oxidant off-gas. In this example, the combustion chamber 60 refers to a space in which the fuel off-gas burns between the upper end of the fuel cell 70 (fuel cell stack 230) and the reformer 50.

  The upstream side of the reformer 50 functions as the vaporization unit 51, and the downstream side of the reformer 50 functions as the reforming unit 52. As shown in FIG. 3 (c), when raw fuel such as hydrocarbons and reformed water are supplied to the reformer 50, the reforming water evaporates and steam is generated in the vaporization section 51, which is generated. The steam and the raw fuel such as hydrocarbon are mixed. In the reforming unit 52, steam and raw fuel such as hydrocarbons undergo a steam reforming reaction via a catalyst to generate fuel gas.

  Next, the outline of the operation at the time of starting the fuel cell system 100 will be described with reference to FIGS. First, the oxidant gas supply unit 40 supplies oxidant gas necessary for combustion in the combustion chamber 60 to the combustion chamber 60 via the cathode 71 of the fuel cell 70 in accordance with an instruction from the control unit 10. Next, the glow plug 82 heats the ignition heater according to the instruction of the control unit 10.

  After heating the ignition heater, the raw fuel supply unit 20 supplies the raw fuel gas necessary for combustion in the combustion chamber 60 to the combustion chamber 60 via the anode 72 of the fuel cell 70 in accordance with an instruction from the control unit 10. . Thereby, in the vicinity of the ignition heater, the raw fuel gas is burned using oxygen of the oxidant gas. As a result, the flame spreads over the entire combustion chamber 60 with the ignition heater as a base point. The control unit 10 estimates the reforming catalyst temperature of the reforming unit 52 based on the detection result of the temperature sensor 81. After the estimated temperature of the reforming catalyst reaches the steam reforming reaction possible temperature, the reforming water pump 32 starts supplying reforming water according to the instruction of the control unit 10. Thereby, the reforming unit 52 of the reformer 50 generates a fuel gas containing hydrogen from the fuel gas and the reformed water by a reforming reaction using heat generated in the combustion chamber 60. The fuel gas is supplied to the anode 72 of the fuel battery cell 70. Thereby, power generation is started in the fuel cell 70.

  Next, an outline of the operation of the fuel cell system 100 during normal power generation will be described. The raw fuel supply unit 20 supplies a required amount of raw fuel gas to the reformer 50 in accordance with instructions from the control unit 10. The reforming water pump 32 supplies a necessary amount of reforming water to the reformer 50 in accordance with instructions from the control unit 10. The fuel gas generated in the reformer 50 is supplied to the anode 72 of the fuel cell 70.

  The oxidant gas supply unit 40 supplies a necessary amount of oxidant gas to the cathode 71 of the fuel cell 70 in accordance with instructions from the control unit 10. Thereby, power generation is continued in the fuel cell 70. The oxidant off-gas discharged from the cathode 71 and the fuel off-gas discharged from the anode 72 flow into the combustion chamber 60. In the combustion chamber 60, the fuel off-gas burns with oxygen in the oxidant off-gas. The heat obtained by the combustion is given to the reformer 50 and the fuel cell 70. Thus, in the fuel cell system 100, combustible components such as hydrogen and carbon monoxide contained in the fuel off-gas can be burned in the combustion chamber 60.

  The heat exchanger 90 exchanges heat between the exhaust gas discharged from the combustion chamber 60 and tap water flowing in the heat exchanger 90. Condensed water obtained from the exhaust gas by heat exchange is stored in the reformed water tank 31. The temperature sensor 81 detects the temperature inside the combustion chamber 60 and gives the result to the control unit 10. The control unit 10 controls at least one of the raw fuel supply unit 20, the reforming water supply unit 30, and the oxidant gas supply unit 40 according to the result of the temperature sensor 81.

  Here, the amount of reforming water supplied to the reforming section 52 will be described. When the supply amount of the reforming water to the reforming unit 52 becomes too small, the amount of carbon in the raw fuel becomes excessive with respect to the water vapor. In this case, carbon is easily deposited in the reforming part 52. Thereby, the reforming function of the reforming unit 52 is deteriorated. On the other hand, if the amount of reforming water supplied to the reforming section 52 becomes excessive, the amount of water vapor becomes excessive with respect to the amount of carbon in the raw fuel. In this case, the temperature of the reforming unit 52 decreases. Thereby, the reforming efficiency is lowered. From the above, there is an appropriate range for the amount of reforming water supplied to the reforming section 52, and the reforming efficiency in the reforming section 52 is reduced by controlling the amount of reforming water supplied within that range. Can be suppressed. An appropriate amount of reforming water can be obtained from the temperature in the reformer 50. The temperature in the reformer 50 can be indirectly obtained from the temperature of the combustion chamber 60, for example.

  However, the temperature of the combustion chamber 60 is determined by a plurality of factors. For example, the temperature of the combustion chamber 60 is the amount of latent heat of vaporization in the vaporizing section 51 of reformed water, the amount of endothermic reaction heat by steam reforming in the reforming section 52, the amount of combustion heat of the fuel off-gas in the combustion chamber 60, and the combustion efficiency in the combustion chamber 60. Factors such as the amount of heat supplied to the fuel cell 70 and the amount of heat radiated to the outside of the fuel cell system 100 are determined in a superimposed manner. Therefore, it is difficult to detect from the temperature change in the combustion chamber 60 that the amount of reforming water supplied to the reformer 50 is too small or excessive.

  FIG. 4 is a diagram showing a temperature change of the combustion chamber 60 when supply of the reforming water is started and the reforming water supply amount is kept constant at S / C ratio = 2.5. In FIG. 4, the horizontal axis indicates the time elapsed after the start of combustion in the combustion chamber 60, and the vertical axis indicates the temperature inside the combustion chamber 60. The S / C ratio “S” indicates the number of moles of reforming water supplied by the reforming water pump 32, and “C” indicates the number of moles of carbon in the raw fuel supplied by the raw fuel supply unit 20. Indicates.

  As shown in FIG. 4, the temperature of the combustion chamber 60 increases with the start of combustion. However, when the supply of the reforming water is started, the temperature of the combustion chamber 60 temporarily decreases and then increases. Since the factors of this temperature change are diverse as described above, it is difficult to detect whether the reforming water supply amount is too small or excessive from the temperature change of FIG.

  Therefore, in this example, after the reforming water supply by the reforming water pump 32 is started, the S / C ratio is gradually increased to separate the factors of the temperature change. Specifically, by gradually increasing the S / C ratio, it is possible to suppress a rapid increase in the latent heat of vaporization of reformed water and the endothermic heat of the steam reforming reaction. The S / C ratio can be calculated from the control value for the reforming water pump 32 and the control value for the raw fuel supply unit 20.

  FIG. 5 is a diagram showing the differential value of the temperature of the combustion chamber 60 and the temperature of the combustion chamber 60 when the S / C ratio is gradually increased. In FIG. 5, the horizontal axis indicates time, the left vertical axis indicates the temperature of the combustion chamber 60, and the right vertical axis indicates the differential value of the S / C ratio and the temperature of the combustion chamber 60. In FIG. 5, the increase rate of the S / C ratio is set to 0.25 [S / C] / 60 seconds as an example.

  As shown in FIG. 5, when the S / C ratio is too small and the steam reforming reaction proceeds in a state where the reforming water is insufficient, the latent heat of vaporization of the reforming water and the endothermic heat of the steam reforming reaction are small. On the other hand, since the amount of combustion heat of the fuel off gas increases, the temperature of the combustion chamber 60 rises.

  When the S / C ratio increases, the amount of latent heat of vaporization of reformed water and the amount of endothermic heat of the steam reforming reaction increase. Antagonize. Thereby, the temperature rise of the combustion chamber 60 stops. In this state, the supply amount of the reforming water to the reforming unit 52 is neither too small nor excessive. Thereby, carbon deposition in the reforming part 52 can be suppressed. In addition, control with less heat loss is realized.

  When the S / C ratio is further increased, the endothermic heat amount of the steam reforming reaction and the latent heat of vaporization of the reformed water are increased as compared with the combustion heat amount of the fuel offgas. Thereby, the temperature of the combustion chamber 60 falls. Thereafter, when the S / C ratio is converged by an appropriate amount, the temperature of the combustion chamber 60 rises again to an antagonistic point between the combustion heat amount and the heat radiation amount in the combustion chamber 60.

  In this example, when the S / C ratio is gradually increased, the S / C ratio when the temperature rise of the combustion chamber 60 changes from positive to negative is set as the optimal S / C ratio, and the optimal S / C ratio is controlled. By controlling the reforming water supply amount and the raw fuel gas supply amount as the target values, it is possible to suppress carbon deposition in the reforming section 52 and to realize control with less heat loss. As described above, the supply amounts of the raw fuel and the reforming water can be optimized and controlled without using a detector such as a flow meter for detecting the water flow rate.

  Note that the value obtained as the optimum S / C ratio may vary from the optimum value. For example, when the raw fuel gas distribution change, the oxidant gas distribution change, the reforming water distribution change, the reforming catalyst performance deterioration, the variation of various devices, the secular change, etc. occur in the fuel cell system 100, the optimum S / C The value obtained as the ratio may vary from the optimum value. However, when the S / C ratio is gradually increased, the optimum value is updated by acquiring again the S / C ratio when the temperature increase of the combustion chamber 60 changes from positive to negative as the optimum S / C ratio. be able to.

  For example, by detecting the optimum S / C ratio when the fuel cell system 100 is activated, the S / C ratio can be optimized every time the fuel cell system 100 is activated. Further, even after startup, the S / C ratio is gradually increased from a low value at a predetermined time period to detect the optimum S / C ratio, so that the S / C regardless of the secular change of various devices of the fuel cell system 100. The C ratio can be optimized.

  In addition, it becomes easy to detect the optimal S / C ratio by using the temperature differential value of the combustion chamber 60. Specifically, the S / C ratio when the temperature differential value of the combustion chamber 60 changes from positive to negative can be detected as the optimum S / C ratio. In addition, carbon may be temporarily deposited in the process of gradually increasing the S / C ratio, but after obtaining the optimum S / C ratio, the reforming water is supplied in a state where the reforming catalyst is not deactivated. By doing so, the deposited carbon can be oxidized.

  FIG. 6 is a diagram illustrating an example of a flowchart executed when the optimum S / C ratio is detected when the fuel cell 70 is activated. As shown in FIG. 6, first, the control unit 10 causes the oxidant gas so that the oxidant gas necessary for combustion in the combustion chamber 60 is supplied to the combustion chamber 60 via the cathode 71 of the fuel cell 70. The supply unit 40 is controlled (step S1). Next, the control unit 10 controls the glow plug 82 so that the ignition heater of the glow plug 82 is heated (step S2).

  After heating the ignition heater, the control unit 10 controls the raw fuel supply unit 20 so that the raw fuel gas necessary for combustion in the combustion chamber 60 is supplied to the combustion chamber 60 via the anode 72 of the fuel cell 70. Control (step S3). Thereby, in the vicinity of the ignition heater, the raw fuel gas is burned using oxygen of the oxidant gas. As a result, the flame spreads over the entire combustion chamber 60 with the ignition heater as a base point.

  The control unit 10 acquires the detection result of the temperature sensor 81, and estimates the reforming catalyst temperature of the reforming unit 52 based on the detection result (step S4). After the estimated temperature of the reforming catalyst reaches the steam reforming reaction possible temperature, the reforming water pump 32 starts supplying reforming water according to the instruction of the control unit 10 (step S5). Thereby, the reforming unit 52 of the reformer 50 generates a fuel gas containing hydrogen from the fuel gas and the reformed water by a reforming reaction using heat generated in the combustion chamber 60. The fuel gas is supplied to the anode 72 of the fuel battery cell 70. Thereby, power generation is started in the fuel cell 70.

  Next, the control unit 10 gradually increases the S / C ratio (step S6). Next, the control unit 10 acquires the detection result of the temperature sensor 81 and determines whether or not the differential value D has changed from positive to negative (step S7). If it is not determined in step S7 that the differential value has changed from positive to negative, the control unit 10 executes step S6 again.

  When it is determined in step S7 that the differential value D has changed from plus to minus, the control unit 10 sets the current S / C ratio to the optimum S / C ratio (step S8). Next, the control unit 10 controls the reforming water pump 32 and the raw fuel supply unit 20 so that the S / C ratio becomes the optimum S / C (step S9). Thereafter, the control unit 10 ends the execution of the flowchart.

  According to the flowchart of FIG. 6, the supply amounts of raw fuel and reformed water can be optimized without using a detector such as a flow meter that detects the water flow rate.

  In the present embodiment, when the S / C ratio is gradually increased, the S / C ratio when the temperature rise of the combustion chamber 60 changes from positive to negative is set as the optimum S / C ratio. I can't. For example, the optimum S / C ratio may be derived based on the S / C ratio when the temperature increase of the combustion chamber 60 changes from positive to negative when the S / C ratio is gradually increased. Specifically, when the S / C ratio is gradually increased, a value obtained by giving a predetermined offset to the S / C ratio when the temperature increase of the combustion chamber 60 changes from positive to negative is the optimum S / C ratio. It is good.

(Example 2)
FIG. 7 is a schematic diagram illustrating an overall configuration of the fuel cell system 100a according to the second example. As shown in FIG. 7, in the fuel cell system 100 a, the temperature sensor 81 is disposed not in the combustion chamber 60 but in the reformer 50. According to this configuration, the temperature sensor 81 can directly detect the temperature in the reformer 50.

  Also in this embodiment, when the S / C ratio is gradually increased, the optimum S / C ratio is obtained based on the S / C ratio when the temperature increase detected by the temperature sensor 81 changes from positive to negative. By controlling the reforming water supply amount and the raw fuel gas supply amount with the optimum S / C ratio as the control target value, it is possible to suppress carbon deposition in the reforming section 52 and realize control with less heat loss. . As described above, the supply amounts of the raw fuel and the reforming water can be optimized and controlled without using a detector such as a flow meter for detecting the water flow rate.

  In addition, since reforming water vaporizes in the vaporization part 51 of the reformer 50, the latent heat of vaporization of reforming water is more likely to affect the vaporization part 51 than the reforming part 52. Therefore, the temperature sensor 81 is preferably disposed in the vaporization unit 51.

  Further, the heat capacity of the reformer 50 is larger than the heat capacity of the gas in the combustion chamber 60. Therefore, the temperature change due to the S / C ratio change is larger in the combustion chamber 60 than in the reformer 50. Therefore, it is easier to detect the temperature change if the temperature in the reformer 50 is indirectly detected through the temperature of the combustion chamber 60 than the temperature in the reformer 50 is directly detected. From the above, it is more preferable to arrange the temperature sensor 81 in the combustion chamber 60.

  Each of the above examples can be applied to any other type of fuel cell such as a solid polymer type, a solid oxide type, or a carbonated molten salt type.

DESCRIPTION OF SYMBOLS 10 Control part 20 Raw fuel supply part 30 Reformed water supply part 31 Reformed water tank 32 Reformed water pump 40 Oxidant gas supply part 50 Reformer 51 Vaporizer 52 Reformer 60 Combustion chamber 70 Fuel cell 71 Cathode 72 Anode 73 Electrolyte 81 Temperature sensor 82 Glow plug 90 Heat exchanger 100 Fuel cell system

Claims (12)

A reformer that generates fuel gas by a steam reforming reaction;
A fuel battery cell that generates electricity with an oxidant gas and the fuel gas generated by the reformer;
A combustion chamber for heating the reformer by burning fuel off-gas of the fuel cell;
A temperature sensor for directly or indirectly detecting the temperature of the reformer;
A control unit that controls the ratio of the supply amount of reforming water to the raw fuel to the reformer,
The control unit is based on the supply amount ratio when the detected temperature rise of the temperature sensor changes from positive to negative when the ratio of the supply amount of the reforming water to the supply amount of the raw fuel is increased. A fuel cell system that controls the supply amount ratio.   The fuel cell system according to claim 1, wherein the temperature sensor is disposed in the combustion chamber.   When the ratio of the reforming water supply amount to the raw fuel supply amount is increased, the control unit determines the supply amount ratio when the temperature increase detected by the temperature sensor changes from positive to negative. The fuel cell system according to claim 1 or 2, wherein   The control unit increases the ratio of the supply amount of the reforming water to the supply amount of the raw fuel when the fuel cell is started up, and the supply when the temperature rise detected by the temperature sensor changes from positive to negative. The fuel cell system according to claim 1, wherein a quantitative ratio is obtained.   The control unit increases the ratio of the supply amount of the reforming water to the supply amount of the raw fuel in a predetermined time period, and the supply amount ratio when the temperature rise detected by the temperature sensor changes from positive to negative. The fuel cell system according to any one of claims 1 to 3, wherein: A reformer that generates fuel gas by a steam reforming reaction;
A fuel battery cell that generates electricity with an oxidant gas and the fuel gas generated by the reformer;
A combustion chamber for heating the reformer by burning fuel off-gas of the fuel cell;
A temperature sensor for detecting the temperature in the combustion chamber;
A control unit that controls the ratio of the supply amount of reforming water to the raw fuel to the reformer,
The control unit is based on the supply amount ratio when the detected temperature rise of the temperature sensor changes from positive to negative when the ratio of the supply amount of the reforming water to the supply amount of the raw fuel is increased. A fuel cell system that controls the supply amount ratio. A reformer that generates fuel gas by a steam reforming reaction; a fuel battery cell that generates electric power using an oxidant gas and the fuel gas generated by the reformer; A fuel cell system comprising: a combustion chamber for heating the reformer;
A temperature detection step for directly or indirectly detecting the temperature of the reformer;
The supply based on the supply amount ratio when the temperature increase detected in the temperature detection step changes from positive to negative when the supply amount ratio of reforming water to raw fuel to the reformer is increased. A control step for controlling the quantity ratio, and a method for operating the fuel cell system.   8. The method of operating a fuel cell system according to claim 7, wherein the temperature detecting step is a step of detecting a temperature in the combustion chamber.   In the control step, when the ratio of the supply amount of the reforming water to the supply amount of the raw fuel is increased, the supply amount ratio when the temperature increase detected in the temperature detection step changes from positive to negative. 9. The method for operating a fuel cell system according to claim 7, wherein the control target value is a step.   In the control step, the ratio of the supply amount of the reforming water to the supply amount of the raw fuel is increased at the start-up of the fuel battery cell, and the temperature rise detected in the temperature detection step is changed from positive to negative. The operation method of the fuel cell system according to claim 7, wherein the supply amount ratio is obtained in a case.   In the control step, the ratio of the supply amount of the reforming water to the supply amount of the raw fuel is increased at a predetermined time period, and the temperature increase detected in the temperature detection step is changed from positive to negative. The method for operating a fuel cell system according to any one of claims 7 to 9, wherein the supply amount ratio is obtained. A reformer that generates fuel gas by a steam reforming reaction; a fuel battery cell that generates electric power using an oxidant gas and the fuel gas generated by the reformer; A fuel cell system comprising: a combustion chamber for heating the reformer;
A temperature detecting step for detecting a temperature in the combustion chamber;
The supply based on the supply amount ratio when the temperature increase detected in the temperature detection step changes from positive to negative when the supply amount ratio of reforming water to raw fuel to the reformer is increased. A control step for controlling the quantity ratio, and a method for operating the fuel cell system.

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