WO2011102290A1

WO2011102290A1 - Fuel cell system

Info

Publication number: WO2011102290A1
Application number: PCT/JP2011/052843
Authority: WO
Inventors: 大塚　俊治; 勝久土屋; 重住　司; 中野　清隆; 大江　俊春; 卓哉松尾
Original assignee: Toto株式会社
Priority date: 2010-02-16
Filing date: 2011-02-10
Publication date: 2011-08-25
Also published as: JP2011170983A

Abstract

Disclosed is a fuel cell system, which uses an SOFC, and which can detect an abnormality of power generation at an early stage. The fuel cell system (1) is provided with: a fuel cell module (2), which has a fuel cell unit (16); a fuel flow quantity adjusting unit (38) and an air flow quantity adjusting unit for power generation (45), which supply the fuel cell module (2) with a reaction gas for power generation; a power generation chamber temperature sensor (142) which measures the module temperature of the fuel cell module (2); and a voltage sensor (118) which measures the open circuit voltage value of the fuel cell module (2). At the start up stage, the module temperature is increased, while supplying the reaction gas to the fuel cell module (2), and the module temperature is increased to a power generation start temperature (T₁). The fuel cell system is provided with a control unit (110) which performs abnormality handling control, wherein it is determined, at the start up stage, that power generation is abnormal in the case where the open circuit voltage value is lower than a reference voltage value previously determined corresponding to the module temperature.

Description

Fuel cell system

The present invention relates to a fuel cell system, and more particularly to a fuel cell system using a solid oxide fuel cell (solid oxide fuel cell).

Conventionally, in the fuel cell system, at the start of the fuel cell, before the generated power is supplied to the load, the measured open circuit voltage (hereinafter also referred to as “OCV”) is compared with a reference value, An OCV determination process for determining whether or not the power generation function of the fuel cell system is normal is performed. In this OCV determination, when the measured OCV is greater than or equal to the reference value, it is determined that the power generation function is normal, and power supply to the load can be started.

Among the fuel cell systems, the polymer electrolyte fuel cell (hereinafter also referred to as “PEFC”) is not so high in power generation efficiency, but the operation temperature is relatively low (about 100 ° C.), and the start-up time and operation stop The time is short. Therefore, in PEFC, when the reaction gas is supplied to the fuel battery cell, the cell voltage immediately rises to a predetermined voltage. For this reason, in the PEFC, the OCV determination is performed immediately after starting the supply of the reaction gas (see Patent Document 1). That is, in the PEFC, the OCV determination is performed at the stage where the startup is almost completed.

JP 2009-110806 A

As described above, since the start-up time is short in PEFC, the OCV determination can be performed early from the start of the start-up, and therefore it is possible to determine the quality of the power generation function at an early stage.
However, among fuel cell systems, solid oxide fuel cells (hereinafter also referred to as “SOFC”) having high power generation efficiency have a high operating temperature (about 700 to 1000 ° C.). Long downtime. Specifically, in SOFC, it takes time (about 1.5 to 2 hours) to increase the temperature of the fuel cell module at startup, and the power generation performance is temperature-dependent. It rises only slowly. Therefore, in the SOFC, it is necessary to perform the OCV determination after waiting for the time required for the temperature to rise after the start of the start.

Thus, in SOFC, it takes a long time to make an OCV determination. Therefore, even if there is an abnormality in the power generation function of the fuel cell system, the power generation abnormality cannot be detected by the OCV determination unless 1.5 to 2 hours have elapsed after the start of startup. For this reason, SOFC has a problem that it is not possible to quickly respond to power generation abnormality. In addition, in SOFC, when a power generation abnormality is detected, it is necessary to lower the temperature of a module or the like that has risen to a high temperature, and it takes a long time to stop the system.

Therefore, an object of the present invention is to provide a fuel cell system capable of detecting power generation abnormality at an early stage in a fuel cell system using SOFC.

In order to solve the above-described problems, the present invention provides a fuel cell module having a solid oxide cell, a reaction gas supply means for supplying a reaction gas for power generation to the fuel cell module, and a module temperature of the fuel cell module. A temperature measuring means for measuring and a voltage measuring means for measuring an open circuit voltage value of the fuel cell module, and at the start-up stage, the reaction gas is supplied to the fuel cell module by the reaction gas supply means to raise the module temperature. The fuel cell system configured to cause the module temperature to reach the power generation start temperature, wherein the voltage measurement means is in the middle of the start-up stage before the fuel cell module temperature reaches the power generation start temperature. Is configured to measure the open circuit voltage value, and the measured open circuit voltage value is less than the power generation start temperature. Generation malfunction and determine if it falls below the reference voltage value have to correspond to the module temperature is predetermined, is characterized by comprising an abnormality handling control means for performing an abnormality handling control.

In the present invention configured as described above, at the start-up stage, before the module temperature reaches the power generation start temperature at which power is generated and power can be supplied to the load, that is, the module temperature rises to the power generation start temperature. In the middle stage, the open circuit voltage value is compared with a reference voltage value determined in advance corresponding to the module temperature, so that a power generation abnormality can be detected at an early stage. Is possible. The present invention has a fuel cell module using a solid oxide fuel cell, and this type of fuel cell module requires a long time to start and stop as described above. Therefore, in the present invention, when a power generation abnormality is detected by determining whether there is a power generation abnormality in the middle of the module temperature reaching a predetermined power generation start temperature, abnormality response control is performed at an early stage. be able to.

In the present invention, the reference voltage value is preferably lower than a normal voltage value that is a normal open circuit voltage value corresponding to the module temperature.
According to the present invention configured as described above, by setting the reference voltage value lower than the open circuit voltage value at the normal time, it is erroneously determined as a power generation abnormality due to variations in the measurement of the open circuit voltage value. Can be prevented.

In the present invention, preferably, the reference voltage value is set to be lower than the normal voltage value as the module temperature is lower.
In general, when the module temperature is low, the temperature variation is large, and the power generation performance of each fuel cell unit tends to be uneven. Therefore, the measured value of the open circuit voltage value tends to vary. In order to deal with such variations in the measured value of the open circuit voltage value, in the present invention having the above configuration, when the module temperature is low as in the initial stage of startup, the reference voltage value is set lower than the normal voltage value. It is set. Thereby, in this invention, the misjudgment resulting from variation can be prevented.

In the present invention, preferably, the abnormality handling control means performs the determination of power generation abnormality a plurality of times in the startup stage.
According to the present invention configured as described above, the power generation abnormality determination process based on the open circuit voltage value and the reference voltage value corresponding to the module temperature is performed a plurality of times in the startup stage, so that it is normal until the middle of the startup stage. However, when a cell abnormality occurs after that, it is possible to prevent erroneous determination as normal in the process up to the middle of the startup stage.

In the present invention, preferably, the abnormality handling control is control that lowers the maximum output power after the start of power generation below a set value.
According to the present invention configured as described above, even when the open circuit voltage value is lower than the reference voltage value, there is a case where power can be generated without problems by reducing the maximum output power from the set value power. Therefore, the operation can be continued with the maximum output voltage lowered.

In the present invention, the abnormality handling control is preferably control for stopping the operation of the fuel cell system.
According to the present invention configured as described above, when the open circuit voltage value is significantly lower than the reference voltage value, it is expected that a serious problem such as film peeling of the air electrode has occurred. It is possible to take various measures such as stopping the operation and suppressing wasteful use of the reaction gas.

In the present invention, preferably, a reference voltage value and a stop reference voltage value lower than the reference voltage value are set corresponding to the module temperature, and the abnormality response control means performs open circuit voltage as abnormality response control. Is lower than the reference voltage value and higher than the stop reference voltage value, the maximum output power after the start of power generation is lowered below the set value, and when the open circuit voltage is lower than the stop reference voltage value, the fuel cell system Stop driving.
According to the present invention configured as described above, the seriousness of malfunction or deterioration is estimated according to the magnitude of the open circuit voltage value, and it is appropriately determined whether to continue operation or stop at low output. It can be carried out.

In the present invention, preferably, the stop reference voltage value is determined to be lower than the reference voltage as the module temperature is lower.
In general, when the module temperature is low, the temperature variation is large, the power generation performance of each fuel cell unit tends to be uneven, and the measured value of the open circuit voltage value tends to vary. In order to deal with such a variation in the measured value of the open circuit voltage value, in the present invention having the above-described configuration, when the module temperature is not so high as in the initial start and middle stages, the stop reference voltage value is compared with the reference voltage value. Is set lower. Thereby, in this invention, the misjudgment resulting from the variation in open circuit voltage value measurement, and an operation stop can be prevented.

According to the fuel cell system of the present invention, power generation abnormality can be detected at an early stage.

1 is an overall configuration diagram showing a solid oxide fuel cell (SOFC) according to an embodiment of the present invention. 1 is a front sectional view showing a solid oxide fuel cell (SOFC) fuel cell module according to an embodiment of the present invention. It is sectional drawing which follows the III-III line of FIG. It is a fragmentary sectional view showing a fuel cell unit of a solid oxide fuel cell (SOFC) according to one embodiment of the present invention. 1 is a perspective view showing a fuel cell stack of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention. 1 is a block diagram illustrating a solid oxide fuel cell (SOFC) according to an embodiment of the present invention. It is a time chart which shows the operation | movement at the time of starting of the solid oxide fuel cell (SOFC) by one Embodiment of this invention. It is a time chart which shows the operation | movement at the time of operation stop of the solid oxide fuel cell (SOFC) by one Embodiment of this invention. It is a time chart explaining the correspondence of module temperature at the time of starting of a solid oxide fuel cell (SOFC) by one embodiment of the present invention, reaction gas supply amount, and OCV. It is a graph which shows the correspondence of the module temperature used by the OCV determination process of the solid oxide fuel cell (SOFC) by one Embodiment of this invention, a reference voltage value, and a stop reference voltage value. It is a flowchart which shows the procedure of the abnormality response control at the time of starting of the solid oxide fuel cell (SOFC) by one Embodiment of this invention.

Next, a solid oxide fuel cell (SOFC) according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram showing a solid oxide fuel cell (SOFC) according to an embodiment of the present invention. As shown in FIG. 1, a solid oxide fuel cell (SOFC) or fuel cell system 1 according to an embodiment of the present invention includes a fuel cell module 2 and an auxiliary unit 4.

The fuel cell module 2 includes a housing 6, and a sealed space 8 is formed inside the housing 6 via a heat insulating material (not shown, but the heat insulating material is not an essential component and may not be necessary). Is formed. In addition, you may make it not provide a heat insulating material. A fuel cell assembly 12 that performs a power generation reaction with fuel gas and an oxidant (air) is disposed in a power generation chamber 10 that is a lower portion of the sealed space 8. The fuel cell assembly 12 includes ten fuel cell stacks 14 (see FIG. 5), and the fuel cell stack 14 includes 16 fuel cell unit 16 (see FIG. 4). Yes. Thus, the fuel cell assembly 12 has 160 fuel cell units 16, and all of these fuel cell units 16 are connected in series.

A combustion chamber 18 is formed above the above-described power generation chamber 10 in the sealed space 8 of the fuel cell module 2. In this combustion chamber 18, the remaining fuel gas that has not been used for the power generation reaction and the remaining oxidant (air) ) And combusted to generate exhaust gas.
Further, a reformer 20 for reforming the fuel gas is disposed above the combustion chamber 18, and the reformer 20 is heated to a temperature at which the reforming reaction can be performed by the combustion heat of the residual gas described above. is doing. Further, an air heat exchanger 22 for receiving combustion heat and heating air is disposed above the reformer 20.

Next, the auxiliary unit 4 stores a pure water tank 26 that stores water from a water supply source 24 such as tap water and uses the filter to obtain pure water, and a water flow rate that adjusts the flow rate of the water supplied from the water storage tank. An adjustment unit 28 (such as a “water pump” driven by a motor) is provided. The auxiliary unit 4 also includes a gas shut-off valve 32 that shuts off the fuel gas supplied from a fuel supply source 30 such as city gas, a desulfurizer 36 for removing sulfur from the fuel gas, and a flow rate of the fuel gas. A fuel flow rate adjusting unit 38 (such as a “fuel pump” driven by a motor) is provided. Further, the auxiliary unit 4 includes an electromagnetic valve 42 that shuts off air that is an oxidant supplied from the air supply source 40, a reforming air flow rate adjusting unit 44 that adjusts the flow rate of air, and a power generation air flow rate adjusting unit. 45 (such as an “air blower” driven by a motor), a first heater 46 for heating the reforming air supplied to the reformer 20, and a second for heating the power generating air supplied to the power generation chamber And a heater 48. The first heater 46 and the second heater 48 are provided in order to efficiently raise the temperature at startup, but may be omitted.

Next, a hot water production apparatus 50 to which exhaust gas is supplied is connected to the fuel cell module 2. The hot water production apparatus 50 is supplied with tap water from the water supply source 24, and the tap water is heated by the heat of the exhaust gas and supplied to a hot water storage tank of an external hot water heater (not shown).
The fuel cell module 2 is provided with a control box 52 for controlling the amount of fuel gas supplied and the like.
Furthermore, the fuel cell module 2 is connected to an inverter 54 that is a power extraction unit (power conversion unit) for supplying the power generated by the fuel cell module to the outside.

Next, the internal structure of a solid oxide fuel cell (SOFC) fuel cell module according to an embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a side sectional view showing a solid oxide fuel cell (SOFC) fuel cell module according to an embodiment of the present invention, and FIG. 3 is a sectional view taken along line III-III in FIG.
As shown in FIGS. 2 and 3, in the sealed space 8 in the housing 6 of the fuel cell module 2, as described above, the fuel cell assembly 12, the reformer 20, and the air heat exchange are sequentially performed from below. A vessel 22 is arranged.

The reformer 20 is provided with a pure water introduction pipe 60 for introducing pure water and a reformed gas introduction pipe 62 for introducing reformed fuel gas and reforming air to the upstream end side thereof. In addition, in the reformer 20, an evaporation unit 20a and a reforming unit 20b are formed sequentially from the upstream side, and the evaporation unit 20a and the reforming unit 20b are filled with a reforming catalyst. The fuel gas and air mixed with the steam (pure water) introduced into the reformer 20 are reformed by the reforming catalyst filled in the reformer 20. As the reforming catalyst, a catalyst obtained by imparting nickel to the alumina sphere surface or a catalyst obtained by imparting ruthenium to the alumina sphere surface is appropriately used.

A fuel gas supply pipe 64 is connected to the downstream end side of the reformer 20, and the fuel gas supply pipe 64 extends downward and further in an manifold 66 formed below the fuel cell assembly 12. It extends horizontally. A plurality of fuel supply holes 64 b are formed in the lower surface of the horizontal portion 64 a of the fuel gas supply pipe 64, and the reformed fuel gas is supplied into the manifold 66 from the fuel supply holes 64 b.

A lower support plate 68 having a through hole for supporting the fuel cell stack 14 described above is attached above the manifold 66, and the fuel gas in the manifold 66 flows into the fuel cell unit 16. Supplied.

Next, an air heat exchanger 22 is provided above the reformer 20. The air heat exchanger 22 includes an air aggregation chamber 70 on the upstream side and two air distribution chambers 72 on the downstream side. The air aggregation chamber 70 and the air distribution chamber 72 include six air flow path tubes 74. Connected by. Here, as shown in FIG. 3, three air flow path pipes 74 form a set (74a, 74b, 74c, 74d, 74e, 74f), and the air in the air collecting chamber 70 is in each set. It flows into each air distribution chamber 72 from the air flow path pipe 74.

The air flowing through the six air flow path pipes 74 of the air heat exchanger 22 is preheated by exhaust gas that burns and rises in the combustion chamber 18.
An air introduction pipe 76 is connected to each of the air distribution chambers 72, the air introduction pipe 76 extends downward, and the lower end side communicates with the lower space of the power generation chamber 10, and the air that has been preheated in the power generation chamber 10. Is introduced.

Next, an exhaust gas chamber 78 is formed below the manifold 66. Further, as shown in FIG. 3, an exhaust gas passage 80 extending in the vertical direction is formed inside the front surface 6 a and the rear surface 6 b which are surfaces along the longitudinal direction of the housing 6, and the upper end of the exhaust gas chamber passage 80 is formed. The side communicates with the space in which the air heat exchanger 22 is disposed, and the lower end side communicates with the exhaust gas chamber 78. Further, an exhaust gas discharge pipe 82 is connected to substantially the center of the lower surface of the exhaust gas chamber 78, and the downstream end of the exhaust gas discharge pipe 82 is connected to the above-described hot water producing apparatus 50 shown in FIG.
As shown in FIG. 2, an ignition device 83 for starting combustion of fuel gas and air is provided in the combustion chamber 18.

Next, the fuel cell unit 16 will be described with reference to FIG. FIG. 4 is a partial cross-sectional view showing a fuel cell unit of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 4, the fuel cell unit 16 includes a fuel cell 84 and inner electrode terminals 86 respectively connected to the vertical ends of the fuel cell 84.
The fuel cell 84 is a tubular structure extending in the vertical direction, and includes a cylindrical inner electrode layer 90 that forms a fuel gas flow path 88 therein, a cylindrical outer electrode layer 92, an inner electrode layer 90, and an outer side. An electrolyte layer 94 is provided between the electrode layer 92 and the electrode layer 92. The inner electrode layer 90 is a fuel electrode through which fuel gas passes and becomes a (−) electrode, while the outer electrode layer 92 is an air electrode in contact with air and becomes a (+) electrode.

Since the inner electrode terminals 86 attached to the upper end side and the lower end side of the fuel cell 16 have the same structure, the inner electrode terminal 86 attached to the upper end side will be specifically described here. The upper portion 90 a of the inner electrode layer 90 includes an outer peripheral surface 90 b and an upper end surface 90 c exposed to the electrolyte layer 94 and the outer electrode layer 92. The inner electrode terminal 86 is connected to the outer peripheral surface 90b of the inner electrode layer 90 through a conductive sealing material 96, and is further in direct contact with the upper end surface 90c of the inner electrode layer 90, thereby Electrically connected. A fuel gas passage 98 communicating with the fuel gas passage 88 of the inner electrode layer 90 is formed at the center of the inner electrode terminal 86.

The inner electrode layer 90 includes, for example, a mixture of Ni and zirconia doped with at least one selected from rare earth elements such as Ca, Y, and Sc, and Ni and ceria doped with at least one selected from rare earth elements. The mixture is formed of at least one of Ni and a mixture of lanthanum garade doped with at least one selected from Sr, Mg, Co, Fe, and Cu.

The electrolyte layer 94 includes, for example, zirconia doped with at least one selected from rare earth elements such as Y and Sc, ceria doped with at least one selected from rare earth elements, lanthanum gallate doped with at least one selected from Sr and Mg, Formed from at least one of the following.

The outer electrode layer 92 includes, for example, lanthanum manganite doped with at least one selected from Sr and Ca, lanthanum ferrite doped with at least one selected from Sr, Co, Ni and Cu, Sr, Fe, Ni and Cu. It is formed from at least one of lanthanum cobaltite doped with at least one selected from the group consisting of silver and silver.

Next, the fuel cell stack 14 will be described with reference to FIG. FIG. 5 is a perspective view showing a fuel cell stack of a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 5, the fuel cell stack 14 includes 16 fuel cell units 16, and the lower end side and the upper end side of these fuel cell units 16 are a ceramic lower support plate 68 and an upper side, respectively. It is supported by the support plate 100. The lower support plate 68 and the upper support plate 100 are formed with through

holes

68a and 100a through which the inner electrode terminal 86 can pass.

Furthermore, a current collector 102 and an external terminal 104 are attached to the fuel cell unit 16. The current collector 102 includes a fuel electrode connection portion 102a that is electrically connected to an inner electrode terminal 86 attached to the inner electrode layer 90 that is a fuel electrode, and an entire outer peripheral surface of the outer electrode layer 92 that is an air electrode. And an air electrode connecting portion 102b electrically connected to each other. The air electrode connecting portion 102b is formed of a vertical portion 102c extending in the vertical direction on the surface of the outer electrode layer 92 and a plurality of horizontal portions 102d extending in a horizontal direction along the surface of the outer electrode layer 92 from the vertical portion 102c. Has been. The fuel electrode connection portion 102a is linearly directed obliquely upward or obliquely downward from the vertical portion 102c of the air electrode connection portion 102b toward the inner electrode terminal 86 positioned in the vertical direction of the fuel cell unit 16. It extends.

Further, the inner electrode terminals 86 at the upper end and the lower end of the two fuel cell units 16 located at the ends of the fuel cell stack 14 (the far left side and the near side in FIG. 5) are external terminals, respectively. 104 is connected. These external terminals 104 are connected to the external terminals 104 (not shown) of the fuel cell unit 16 at the end of the adjacent fuel cell stack 14, and as described above, the 160 fuel cell units 16 Everything is connected in series.

Next, sensors and the like attached to the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIG. FIG. 6 is a block diagram illustrating a solid oxide fuel cell (SOFC) according to an embodiment of the present invention.
As shown in FIG. 6, the solid oxide fuel cell 1 includes a control unit 110, and the control unit 110 includes operation buttons such as “ON” and “OFF” for operation by the user. A device 112, a display device 114 for displaying various data such as a power generation output value (wattage), and a notification device 116 for issuing an alarm (warning) in an abnormal state are connected. The notification device 116 may be connected to a remote management center and notify the management center of an abnormal state.

Next, signals from various sensors described below are input to the control unit 110.
First, the voltage sensor 118 measures the voltage across both ends of a series connection composed of 160 fuel cell units 16. The voltage sensor 118 can measure an open circuit voltage (OCV) to be supplied to a load (inverter 54) and a voltage in a load state.
The combustible gas detection sensor 120 is for detecting a gas leak, and is attached to the fuel cell module 2 and the auxiliary unit 4.
The CO detection sensor 122 detects whether or not CO in the exhaust gas originally discharged to the outside through the exhaust gas passage 80 or the like leaks to an external housing (not shown) that covers the fuel cell module 2 and the auxiliary unit 4. Is to do.
The hot water storage state detection sensor 124 is for detecting the temperature and amount of hot water in a water heater (not shown).

The power state detection sensor 126 is for detecting the current and voltage of the inverter 54 and the distribution board (not shown).
The power generation air flow rate detection sensor 128 is for detecting the flow rate of power generation air supplied to the power generation chamber 10.
The reforming air flow sensor 130 is for detecting the flow rate of the reforming air supplied to the reformer 20.
The fuel flow sensor 132 is for detecting the flow rate of the fuel gas supplied to the reformer 20.

The water flow rate sensor 134 is for detecting the flow rate of pure water (steam) supplied to the reformer 20.
The water level sensor 136 is for detecting the water level of the pure water tank 26.
The pressure sensor 138 is for detecting the pressure on the upstream side outside the reformer 20.
The exhaust temperature sensor 140 is for detecting the temperature of the exhaust gas flowing into the hot water production apparatus 50.

As shown in FIG. 3, the power generation chamber temperature sensor 142 is provided on the front side and the back side in the vicinity of the fuel cell assembly 12, and detects the temperature in the vicinity of the fuel cell stack 14 to thereby detect the fuel cell stack. 14 (ie, the fuel cell 84 itself) is estimated.
The combustion chamber temperature sensor 144 is for detecting the temperature of the combustion chamber 18.
The exhaust gas chamber temperature sensor 146 is for detecting the temperature of the exhaust gas in the exhaust gas chamber 78.
The reformer temperature sensor 148 is for detecting the temperature of the reformer 20, and calculates the temperature of the reformer 20 from the inlet temperature and the outlet temperature of the reformer 20.
The outside air temperature sensor 150 is for detecting the temperature of the outside air when the solid oxide fuel cell (SOFC) is disposed outdoors. Further, a sensor for measuring the humidity or the like of the outside air may be provided.

Signals from these sensors are sent to the control unit 110, and the control unit 110, based on data based on these signals, the water flow rate adjustment unit 28, the fuel flow rate adjustment unit 38, the reforming air flow rate adjustment unit 44, A control signal is sent to the power generation air flow rate adjusting unit 45 to control each flow rate in these units.
Further, the control unit 110 sends a control signal to the inverter 54 to control the power supply amount.

Next, the operation at the time of starting by the solid oxide fuel cell (SOFC) according to the present embodiment will be described with reference to FIG. FIG. 7 is a time chart showing the operation at the time of startup of the solid oxide fuel cell (SOFC) according to one embodiment of the present invention.
Initially, in order to warm the fuel cell module 2, the operation is started in a no-load state, that is, in a state where a circuit including the fuel cell module 2 is opened. At this time, since no current flows through the circuit, the fuel cell module 2 does not generate power.

First, reforming air is supplied from the reforming air flow rate adjustment unit 44 to the reformer 20 of the fuel cell module 2 via the first heater 46. At the same time, the power generation air is supplied from the power generation air flow rate adjustment unit 45 to the air heat exchanger 22 of the fuel cell module 2 via the second heater 48, and this power generation air is supplied to the power generation chamber 10 and the combustion chamber. Reach chamber 18.
Immediately after this, the fuel gas is also supplied from the fuel flow rate adjustment unit 38, and the fuel gas mixed with the reforming air passes through the reformer 20, the fuel cell stack 14, and the fuel cell unit 16, and It reaches the combustion chamber 18.

Next, the ignition device 83 is ignited to burn the fuel gas and air (reforming air and power generation air) in the combustion chamber 18. Exhaust gas is generated by the combustion of the fuel gas and air, and the power generation chamber 10 is warmed by the exhaust gas, and when the exhaust gas rises in the sealed space 8 of the fuel cell module 2, The fuel gas containing the reforming air is warmed, and the power generation air in the air heat exchanger 22 is also warmed.

At this time, the fuel gas mixed with the reforming air is supplied to the reformer 20 by the fuel flow rate adjusting unit 38 and the reforming air flow rate adjusting unit 44. The partial oxidation reforming reaction POX shown in FIG. Since the partial oxidation reforming reaction POX is an exothermic reaction, the startability is good. Further, the heated fuel gas is supplied to the lower side of the fuel cell stack 14 through the fuel gas supply pipe 64, whereby the fuel cell stack 14 is heated from below, and the combustion chamber 18 also has the fuel gas and air. The fuel cell stack 14 is also heated from above, and as a result, the fuel cell stack 14 can be heated substantially uniformly in the vertical direction. Even if the partial oxidation reforming reaction POX proceeds, the combustion reaction between the fuel gas and air continues in the combustion chamber 18.

_{_{_{C m H n + xO 2 →}}} aCO 2 + bCO + cH 2 (1)

When the reformer temperature sensor 148 detects that the reformer 20 has reached a predetermined temperature (for example, 600 ° C.) after the partial oxidation reforming reaction POX is started, the water flow rate adjustment unit 28 and the fuel flow rate adjustment unit 38 are detected. The reforming air flow rate adjusting unit 44 supplies the reformer 20 with a gas in which fuel gas, reforming air, and steam are mixed in advance. At this time, in the reformer 20, an autothermal reforming reaction ATR in which the partial oxidation reforming reaction POX described above and a steam reforming reaction SR described later are used proceeds. Since the autothermal reforming reaction ATR is thermally balanced internally, the reaction proceeds in the reformer 20 in a thermally independent state. That is, when oxygen (air) is large, heat generation by the partial oxidation reforming reaction POX is dominant, and when there is much steam, an endothermic reaction by the steam reforming reaction SR is dominant. At this stage, the initial stage of startup has already passed, and the temperature inside the power generation chamber 10 has been raised to a certain temperature. Therefore, even if the endothermic reaction is dominant, no significant temperature drop is caused. Further, the combustion reaction continues in the combustion chamber 18 even while the autothermal reforming reaction ATR is in progress.

When the reformer temperature sensor 146 detects that the reformer 20 has reached a predetermined temperature (for example, 700 ° C.) after the start of the autothermal reforming reaction ATR shown in Formula (2), the reforming air flow rate The supply of reforming air by the adjustment unit 44 is stopped, and the supply of water vapor by the water flow rate adjustment unit 28 is increased. As a result, the reformer 20 is supplied with a gas that does not contain air and contains only fuel gas and water vapor, and the steam reforming reaction SR of formula (3) proceeds in the reformer 20.

_{_{_{C m H n + xO 2 +}}} yH 2 O → aCO 2 + bCO + cH 2 (2)
C _m H _n + xH ₂ O → aCO ₂ + bCO + cH ₂ (3)

Since this steam reforming reaction SR is an endothermic reaction, the reaction proceeds while maintaining a heat balance with the combustion heat from the combustion chamber 18. At this stage, since the fuel cell module 2 is in the final stage of start-up, the power generation chamber 10 is heated to a sufficiently high temperature. Therefore, even if the endothermic reaction proceeds, the power generation chamber 10 is greatly reduced in temperature. There is nothing. Even if the steam reforming reaction SR proceeds, the combustion reaction continues in the combustion chamber 18.

In this way, after the fuel cell module 2 is ignited by the ignition device 83, the partial oxidation reforming reaction POX, the autothermal reforming reaction ATR, and the steam reforming reaction SR proceed in sequence, so that the inside of the power generation chamber 10 The temperature gradually increases. Next, when the temperature in the power generation chamber 10 and the fuel cell 84 reaches a predetermined power generation temperature lower than the rated temperature at which the fuel cell module 2 is stably operated, the circuit including the fuel cell module 2 is closed, and the fuel cell Power generation by the module 2 is started, so that a current flows in the circuit. Due to the power generation of the fuel cell module 2, the fuel cell 84 itself also generates heat, and the temperature of the fuel cell 84 also rises. As a result, the rated temperature at which the fuel cell module 2 is operated becomes, for example, 600 ° C. to 800 ° C.

Thereafter, in order to maintain the rated temperature, fuel gas and air that are larger than the amount of fuel gas and air consumed in the fuel cell 84 are supplied, and combustion in the combustion chamber 18 is continued. During power generation, power generation proceeds in a steam reforming reaction SR with high reforming efficiency.

Next, the operation when the solid oxide fuel cell (SOFC) according to the present embodiment is stopped will be described with reference to FIG. FIG. 8 is a time chart showing the operation when the solid oxide fuel cell (SOFC) according to the present embodiment is stopped.
As shown in FIG. 8, when the operation of the fuel cell module 2 is stopped, first, the fuel flow rate adjustment unit 38 and the water flow rate adjustment unit 28 are operated to supply fuel gas and water vapor to the reformer 20. Reduce the amount.

When the operation of the fuel cell module 2 is stopped, the amount of fuel gas and water vapor supplied to the reformer 20 is decreased, and at the same time, the fuel cell module 2 for generating air by the power generation air flow rate adjustment unit 45 is used. The supply amount to the inside is increased, and the fuel cell assembly 12 and the reformer 20 are cooled by air, and these temperatures are lowered. Thereafter, when the temperature of the reformer 20 decreases to a predetermined temperature, for example, 400 ° C., the supply of fuel gas and steam to the reformer 20 is stopped, and the steam reforming reaction SR of the reformer 20 is ended. . This supply of power generation air continues until the temperature of the reformer 20 decreases to a predetermined temperature, for example, 200 ° C., and when this temperature is reached, the power generation air from the power generation air flow rate adjustment unit 45 is supplied. Stop supplying.

As described above, in the present embodiment, when the operation of the fuel cell module 2 is stopped, the steam reforming reaction SR by the reformer 20 and the cooling by the power generation air are used in combination. The operation of the fuel cell module can be stopped.

Next, with reference to FIGS. 9 to 11, the abnormality determination response control at the time of startup of the solid oxide fuel cell 1 according to the embodiment of the present invention will be described.
In the abnormality determination handling control of the present embodiment, the OCV is measured at least once or more times during the start-up process, not at the stage where the start-up process is almost finished, and the fuel cell module 2 is controlled based on the obtained OCV. This makes it possible to detect power generation abnormality early.

First, based on FIG.9 and FIG.10, the relationship between module temperature and OCV used as the premise of abnormality determination response control is demonstrated.
FIG. 9 schematically shows a time chart of the module temperature (a), the reaction gas supply amount (b), and the OCV (b) at the time of startup. Here, the module temperature is an average temperature of the fuel cell assembly 12 or the fuel cell unit 16, and is actually represented by the power generation chamber temperature detected by the power generation chamber temperature sensor 142. The reactive gas supply amount corresponds to the fuel flow rate detected by the fuel flow rate sensor 132. OCV corresponds to an open circuit voltage value detected by the voltage sensor 118.

As can be seen from FIG. 9, the OCV has a temperature dependence on the module temperature. That is, there is a close relationship in which the OCV rises as the module temperature rises. Specifically, when the module temperature rises to a certain temperature after the start of startup, the OCV starts to rise, and the module temperature is predetermined at the final stage of startup. When the power generation start temperature (for example, 700 ° C.) is reached, the OCV also reaches a predetermined power generation start voltage value (for example, 150 to 160 V). In the present embodiment, when the module temperature reaches the power generation start temperature, power supply is started from the fuel cell module 2 toward the load (for example, an inverter).

As described above, since the PEFC has a short start-up time, it is possible to detect a power generation abnormality at an early stage even if an OCV determination is made at the end of start-up. In addition, in the PEFC, the OCV behavior during startup does not matter, and since the startup time is short, the OCV behavior is not stable, and accurate determination cannot be performed even if OCV determination is performed during startup. For this reason, conventionally, fuel cells, particularly PEFCs with a short start-up time, did not have the idea of detecting a power generation abnormality by OCV determination during start-up.

On the other hand, the present inventor has found that the behavior of the OCV at the time of startup is stable in the solid oxide fuel cell (SOFC), that is, the value of the OCV with respect to the module temperature is very stable at the time of startup. It was found that the variation of the OCV with respect to the module temperature is relatively small. Specifically, in the SOFC, when the reaction gas is supplied to the fuel cell module, the module temperature and the OCV rise in a stable relationship according to the amount of heat supplied by the reaction gas, and reach a stable operation state. . In addition, the SOFC requires about 1.5 to 2 hours to start up, but the variation of the OCV with respect to the module temperature is relatively small during this period.

As a result, in the SOFC, during the start-up, it is determined whether the OCV value has a predetermined relationship with the module temperature, so that the malfunction of the power generation function of the fuel cell module or the degradation of the power generation performance It can be detected early.

FIG. 10 schematically shows changes in the normal voltage value (a), the reference voltage value (b), and the stop reference voltage value (c) with respect to the module temperature. In the present embodiment, the control unit 110 stores each voltage value change shown in FIG. 10 in the memory as reference data.
The normal voltage value (a) is the same for each module temperature under the same conditions when there is no abnormality in the fuel cell unit 16 and the power generation function of the fuel cell module 2 is normal and the power generation performance is not deteriorated. This is a voltage value detected on average.

The reference voltage value (b) is a voltage value (OCV) determined in consideration of individual manufacturing variations of the fuel cell module 2 and the like. As can be seen from FIG. 10, the reference voltage value (b) starts rising at the OCV determinable temperature T ₁ later than the normal voltage value (a), and the normal voltage value (a) at each module temperature. Has a smaller value.
Therefore, if an OCV (normal region) larger than the reference voltage value is detected at each module temperature, it can be determined that the power generation performance of the fuel cell module 2 is in a normal range. In this case, in this embodiment, after the module temperature reaches the power generation start temperature, it is output to the load with the rated output power (for example, 700 W) as the upper limit.

The stop reference voltage value (c) is a voltage value determined in consideration of allowable performance deterioration (minor power generation abnormality) of the fuel cell module 2. The stop reference voltage value (c) has a smaller value than the reference voltage value (b) at each module temperature.
Therefore, if an OCV greater than the stop reference voltage value and less than or equal to the reference voltage value (degradation region) is detected at each module temperature, it can be determined that the power generation performance of the fuel cell module 2 is in the degraded state range. . In this case, the power generation performance of the fuel cell module 2 is deteriorated, but in the present embodiment, power corresponding to the degree of deterioration is supplied to the load.

In the present embodiment, when it is determined that the state is deteriorated, the output power to the load is reduced according to the detected magnitude of the OCV with respect to the normal voltage value as the abnormality handling control process. For example, in a power generation module that can be temperature, normal operation voltage (e.g., V ₀₎ OCV for (e.g., V ₁₎ to calculate the ratio of (V ₁ / V _0), the ratio to the rated output power during normal The output power reduced by multiplying (rated output power × V ₁ / V ₀ ) can be obtained. In this embodiment, the reduced output power is output to the load as the maximum output power.

However, the present invention is not limited to this, and the output power may be set in stages, such as 600 W, 500 W, and 400 W, depending on the range of the detected OCV value.
The deterioration in the power generation performance of the fuel cell module 2 is, for example, partial peeling of the outer electrode layer 92 of the fuel cell unit 16. Since the power generation area is reduced by such peeling, the output voltage of the fuel cell unit 16 is reduced from the rated voltage (for example, about 1 V). However, even if the output voltage is reduced due to partial peeling, it can be used within the reduced output voltage.

Therefore, in this embodiment, when it is determined that the deterioration (acceptable area) is acceptable according to the detected OCV, the output power is reduced according to the deterioration state or the degree of deterioration, and the use is continued. Is configured to do. Thereby, for example, it is possible to prevent an excessive load from being applied to the normal fuel cell unit 16 in which the above-described peeling or the like has not occurred and the fuel cell unit 16 in which the deterioration has progressed, thereby suppressing reduction in power generation performance. Can prolong the product life.

On the other hand, when an OCV (failure or abnormal region) equal to or lower than the stop reference voltage value is detected at each module temperature, it can be determined that the fuel cell module 2 is in a power generation abnormal state. In this case, as the abnormality handling control process, in the present embodiment, the operation shifts to the stop process.

The malfunction of the power generation system of the fuel cell module 2 is that, for example, a short circuit occurs when the peeled outer electrode layer 92 comes into contact with the adjacent fuel cell unit 16. When a short circuit occurs between the fuel cell units 16, the fuel cell assembly 12 cannot supply a sufficient output voltage. Therefore, in the present embodiment, when it is determined that such a problem has occurred according to the detected OCV, the power supply is stopped.

Table 1 corresponds to FIG. 10, and shows numerical values of voltage values at typical module temperatures. The module temperature of 300 ° C. is a temperature higher than the OCV determination possible temperature T _1. At this time, the normal voltage value (a) is 60 V, the reference voltage value (b) is 10 V, and the voltage difference between them is 50 V. It is. Similarly, at a module temperature of 400 ° C., 500 ° C., 600 ° C., and 700 ° C. (power generation start temperature in the present embodiment), the difference between the two is set to 45V, 30V, 20V, and 10V, respectively. Thus, in this embodiment, the voltage difference between the two is set larger as the module temperature is lower.

This is due to the following reasons. In other words, at the initial stage of start-up when the module temperature is low, the arrangement of the fuel cell units 16 in the power generation chamber 10 (for example, cells near the side walls are easily affected by the surrounding environment) Large temperature unevenness. In addition, the temperature unevenness is large in one fuel cell unit 16. Furthermore, the degree of temperature unevenness also varies depending on environmental conditions such as the outside air temperature at startup. Therefore, in the initial stage of start-up, the temperature unevenness is relatively large throughout the fuel cell assembly 12, and thereby the OCV variation with respect to the module temperature is also relatively large.

On the other hand, when the module temperature is increased, the temperature unevenness is reduced, so that the variation of the OCV with respect to the module temperature is also reduced.
Therefore, since the variation in OCV becomes smaller when the module temperature is higher, in this embodiment, the reference voltage value is set so that the allowable voltage difference between the reference voltage value and the normal voltage value becomes smaller as the module temperature becomes higher. is doing. By setting in this way, it is possible to reduce the possibility of erroneously determining that the power generation performance has deteriorated despite the normal power generation performance.

In Table 1, the voltage difference between the reference voltage value (b) and the stop reference voltage value (c) is 50V and 40V at the module temperatures of 600 ° C. and 700 ° C., respectively. Thus, in this embodiment, the voltage difference between the two is set larger as the module temperature is lower. Further, the voltage difference between the normal voltage value (a) and the stop reference voltage value (c) is 70V and 50V, and the voltage difference between the two is set larger as the module temperature is lower.

As described above, in the present embodiment, if it is determined that there is a malfunction, an operation stop process is performed, and thus power cannot be supplied at all. Accordingly, when the voltage difference between the reference voltage value (b) and the stop reference voltage value (c) is set according to the module temperature in this way, the module temperature is not sufficiently increased (OCV variation). ) Is still in a large state), and it is possible to reduce the possibility that the malfunction is erroneously determined and the operation stop process is performed.

Next, based on FIG. 11, the processing flow of the abnormality determination handling control of this embodiment will be described.
First, when the fuel cell system is started, the control unit 110 measures and acquires the module temperature (step S1).
Next, the control unit 110 determines whether or not the acquired module temperature is equal to or higher than the OCV determination possible temperature T ₁ (step S2).

When the module temperature is not equal to or higher than the OCV determination possible temperature T ₁ (step S2; No), the process of step S1 is repeated.
On the other hand, when the module temperature is equal to or higher than the OCV determination possible temperature T ₁ (step S2; Yes), the control unit 110, based on the data stored in the memory, the reference voltage value and the stop reference corresponding to the acquired module temperature. A voltage value is determined (step S3). Moreover, the control part 110 measures and acquires OCV (step S4).

Next, the control unit 110 compares the acquired OCV with the determined reference voltage value (step S5).
When the OCV is larger than the reference voltage value (step S5; Yes), the power generation performance of the fuel cell module 2 is normal, and the control unit 110 determines that the acquired module temperature can be generated (eg, 700 ° C.). Is determined (step S6).

When the module temperature is equal to or higher than the temperature at which power generation is possible (step S6; Yes), the startup process is normal and there is sufficient power generation performance, so the control unit 110 maximizes the normal rated output power (for example, 700 W). As output power, power supply to the load is started (step S7), and the process is terminated.
On the other hand, if the module temperature is not equal to or higher than the temperature at which power generation is possible (step S6; No), the controller 110 is in the middle of the startup process, so the control unit 110 waits for a predetermined time to elapse (step S8) and repeats the process of step S1. repeat.

In step S5, when the OCV is equal to or lower than the reference voltage value (step S5; No), the power generation performance of the fuel cell module 2 is deteriorated or has a defect in the power generation system. In order to do this, the control unit 110 compares the OCV with the stop reference voltage value (step S9).
When the OCV is larger than the stop reference voltage value (step S9; Yes), the power generation performance of the fuel cell module 2 is deteriorated, but is not in a defective state. It is determined whether or not the temperature reaches a temperature at which power generation is possible (step S10).

When the module temperature is not equal to or higher than the temperature at which power generation is possible (step S10; No), although the power generation performance is deteriorated during the startup process, it is not a problem enough to stop the operation. In step S8, the process in step S1 is repeated again after a predetermined time has elapsed.

On the other hand, when the module temperature is equal to or higher than the temperature at which power generation is possible (step S10; Yes), although power generation can be started, the power generation performance has deteriorated, so the control unit 110 outputs maximum power according to the degree of deterioration. After performing the process of reducing power (step S11), power supply to the load is started with the reduced maximum output power as an upper limit (step S12), and the process is terminated.
In the present embodiment, when the OCV is equal to or lower than the reference voltage value and larger than the stop reference voltage value, power generation is performed by reducing the maximum output power. As a simple method, the maximum output current can be reduced.

In step S9, when the OCV is equal to or lower than the stop reference voltage value (step S9; No), since the power generation system of the fuel cell module 2 has a problem, the control unit 110 performs an operation stop process (step S9). S13), the process is terminated.
In this embodiment, when the OCV is equal to or lower than the reference voltage value and the stop reference voltage value at the time of starting, the display device 114 displays the deterioration status and the failure status, and the notification device 116 indicates the deterioration status to the user or the like. And you may comprise so that a malfunction condition may be alert | reported.

As described above, in the present embodiment, during startup, the OCV and the stop reference voltage value are compared to detect a power generation abnormality (such as a malfunction or failure in the power generation system) before the startup process is completed. It is possible to perform abnormality response control (here, operation stop processing) before the start-up process is completed.

Further, in the present embodiment, it is possible to detect and monitor the deterioration of the power generation function not to the extent of stopping the operation by comparing the OCV and the reference voltage value during the start-up. In this embodiment, even if deterioration is detected, the load applied to each cell unit 16 of the fuel cell assembly 12 is reduced by reducing the output power according to the value of the OCV. It becomes possible to extend the life of the battery module 2.

Further, in the present embodiment, during the start-up, the degree of decrease in the power generation function is distinguished by comparing the OCV and the two reference voltage values, and the abnormality response control (maximum output power Reduction, operation stop) can be performed selectively.

Further, in the present embodiment, during the start-up, the power generation abnormality determination is performed a plurality of times by comparing the OCV with the reference voltage value and the stop reference voltage value, thereby shortening the time from occurrence of the power generation abnormality to detection. It is possible to detect power generation abnormality at an early stage.

In the above-described embodiment, the OCV detected at each module temperature during the start-up is the area between lines ab (normal area), the area between lines bc (deterioration area), and line c in FIG. Even if it is detected to pass through only a single region (normal region or degraded region) among lower regions (failure or abnormal regions), a plurality of regions (normal region and degraded region) Even when the module is detected to pass through, the magnitude of the output power depends on which region the OCV belongs to when the module temperature reaches the module temperature at which power generation is possible (steps S6 and S10). Is configured to be determined.

However, the present invention is not limited to this, and it may be configured such that output power that is not reduced is supplied only when the OCV always has a value in the normal region during startup. That is, when it is determined even once that it is in a degraded state during the start-up (step S5; No), the OCV is larger than the reference voltage value when the module temperature reaches the module temperature at which power generation is possible. Alternatively, the output power may be reduced. In this case, the output power can be reduced according to the ratio determined as the degradation region and the degree thereof.

1 Solid electrolyte fuel cell (fuel cell system)
2 Fuel cell module 4 Auxiliary machine unit 10 Power generation chamber 12 Fuel cell assembly 14 Fuel cell stack 16 Fuel cell unit (solid oxide cell)
18 Combustion chamber 20 Reformer 22 Heat exchanger for air 28 Water flow rate adjustment unit (water supply means)
38 Fuel flow rate adjustment unit (reactive gas supply means)
44 reforming air flow rate adjustment unit 45 power generation air flow rate adjustment unit (reactive gas supply means)
54 inverter 83 ignition device 84 fuel cell 110 control unit (abnormality response control means)
118 Voltage sensor (voltage measuring means)
142 Power generation chamber temperature sensor (temperature measuring means)

Claims

A fuel cell module having a solid oxide cell;
Reactive gas supply means for supplying a reactive gas for power generation to the fuel cell module;
Temperature measuring means for measuring the module temperature of the fuel cell module;
Voltage measuring means for measuring an open circuit voltage value of the fuel cell module,
A fuel cell system configured to increase the module temperature while supplying the reaction gas to the fuel cell module by the reaction gas supply means in the start-up stage so that the module temperature reaches a power generation start temperature. ,
In the starting stage, in the middle stage of starting before the fuel cell module temperature reaches the power generation start temperature, the voltage measuring means is configured to measure the open circuit voltage value,
Abnormality in which the measured open circuit voltage value falls below a predetermined reference voltage value corresponding to the module temperature lower than the power generation start temperature, and that power generation abnormality is determined, and abnormality response control is performed. A fuel cell system comprising a corresponding control means.
The fuel cell system according to claim 1, wherein the reference voltage value is lower than a normal voltage value that is a normal open circuit voltage value corresponding to the module temperature.
3. The fuel cell system according to claim 2, wherein the reference voltage value is set to be lower than the normal voltage value as the module temperature is lower.
The fuel cell system according to any one of claims 1 to 3, wherein the abnormality response control means performs the determination of the power generation abnormality a plurality of times in a startup stage.
The fuel cell system according to any one of claims 1 to 4, wherein the abnormality response control is control for lowering a maximum output power after a start of power generation below a set value.
The fuel cell system according to any one of claims 1 to 4, wherein the abnormality response control is control for stopping operation of the fuel cell system.
Corresponding to the module temperature, the reference voltage value and a stop reference voltage value lower than the reference voltage value are set,
When the open circuit voltage is equal to or lower than the reference voltage value and higher than the stop reference voltage value, the abnormality response control means lowers the maximum output power after the start of power generation below a set value as the abnormality response control. The fuel cell system according to any one of claims 1 to 4, wherein when the open circuit voltage is equal to or less than the stop reference voltage value, the operation of the fuel cell system is stopped.
The fuel cell system according to claim 7, wherein the stop reference voltage value is set to be lower than the reference voltage as the module temperature is lower.