JP7176964B2 - Solid oxide fuel cell system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a solid oxide fuel cell system having a cell stack that generates power by oxidation and reduction of a reformed fuel gas obtained by reforming a raw fuel and air as an oxidant gas.

2. Description of the Related Art Conventionally, solid oxide fuel cell systems in which a solid oxide cell stack using a solid electrolyte as a membrane that conducts oxide ions is housed in a container have been known. In this solid oxide fuel cell system, the cell stack is configured by stacking a plurality of fuel cells, and a fuel electrode for oxidizing fuel gas is provided on one side of the solid electrolyte in each fuel cell, An oxygen electrode for reducing oxygen in the air (oxidant gas) is provided on the other side. The operating temperature of this fuel cell is relatively high, about 700 to 900°C. Electricity is generated by causing an electrochemical reaction.

A solid oxide fuel cell system suitable for home use includes a reformer for steam reforming the raw fuel gas, a reformed fuel gas reformed by the reformer and an oxidant gas (air an air supply means for supplying air as an oxidant gas to the oxygen electrode (air electrode) side of the cell stack, and raw fuel gas to the reformer. and a fuel gas supply means for supplying the cell stack and the reformer are housed in a high-temperature space that is maintained at a high temperature (see, for example, Patent Document 1).

In this solid oxide fuel cell system, an offgas combustion zone is provided as an offgas combustion section above the cell stack, and a reformer is arranged above the offgas combustion zone. The reformed fuel gas from the reformer is supplied to the fuel electrode side of the cell stack, the air from the air supply means is supplied to the air electrode side of the cell stack, and the electrochemical reaction in the cell stack generates electricity. is done. The fuel off-gas from the fuel electrode side of the cell stack (that is, anode off-gas) and the air off-gas from the air electrode side (that is, cathode off-gas) are led to the off-gas combustion zone and burned, and the combustion heat is used to create a high temperature space. is maintained at a high temperature, and the reformer and the like are heated.

As a solid oxide fuel cell system, instead of providing an offgas combustion area on the upper side of the cell stack, a system including an offgas combustor as an offgas combustion unit has also been proposed (see, for example, Patent Document 2). In this solid oxide fuel cell system, fuel off-gas (anode off-gas) from the fuel electrode side of the cell stack is supplied to the combustor through the fuel off-gas supply channel, and air off-gas from the air electrode side of the cell stack is supplied to the combustor. (Cathode off-gas) is fed to the combustor through the air off-gas feeding channel, where the fuel off-gas is combusted by the air off-gas, and the combustion heat is used to keep the high-temperature space at a high temperature, The reformer and the like are heated.

Such a solid oxide fuel cell system can be operated with high power generation efficiency, but in order to operate with high efficiency, it is necessary to operate at a high fuel utilization rate. The power generation efficiency of the cell stack is roughly proportional to the product of the average power generation voltage of the fuel cells and the fuel utilization rate. H ₂ ) is consumed and water (H ₂ O) is produced.

In general, the fuel electrode of a solid oxide fuel cell uses a cermet (a mixture of metallic nickel and ceramics) in which metallic nickel particles are present together with ceramic particles. As the hydrogen to water ratio (H ₂ /H ₂ O) decreases, the metallic nickel particles will begin to oxidize. When the metal nickel particles on the fuel electrode side of the fuel cell are oxidized, their electrical resistance increases, so that no power is generated in the vicinity of the fuel electrode side exit of the fuel cell, and nickel on the fuel electrode side of the fuel cell gradually decreases. The area where particles are oxidized expands, and the area where power generation is difficult expands. Throughout this specification, "fuel utilization rate" means that the raw fuel gas supplied through the fuel gas supply passage contributes to power generation in the cell stack (that is, it is consumed by the cell stack for power generation). Percentage.

In addition, the fuel electrode oxidized in this way is reduced under other conditions during power generation (partial load operation state, start state, stop state, etc.) and returns to the nickel state, and the nickel particles are repeatedly oxidized and reduced. However, if the number of repetitions increases, there is a risk that the material on the fuel electrode side of the fuel cell will undergo dimensional changes. If the material on the fuel electrode side undergoes a dimensional change, cracks will occur in the solid electrolyte that is joined to the fuel electrode. For this reason, it is necessary to increase the fuel utilization rate of the solid oxide fuel cell system in order to increase the power generation efficiency of the system, but if it is too high, the cell stack may be damaged.

In such a solid oxide fuel cell system, the fuel off-gas (anode off-gas) from the fuel electrode side of the cell stack is burned by the air off-gas (cathode off-gas) from the air electrode side in the off-gas fuel section. However, if the fuel utilization rate is increased, the combustion in the off-gas combustion section becomes leaner, resulting in poor combustion, partial misfires, and even misfires. If such combustion failure or partial misfire occurs, the ambient temperature of the cell stack will drop, resulting in power generation failure in the worst case.

JP-A-2005-285340 Japanese Unexamined Patent Application Publication No. 2008-21596

In such a solid oxide fuel cell system, it is necessary to increase the fuel utilization rate in order to operate with improved power generation efficiency. It is necessary to stabilize the supply flow rate of raw fuel gas.

In the solid oxide fuel cell system, a low-pressure fuel gas pump is used as fuel gas supply means, and a diaphragm type fuel gas pump is used as the fuel gas pump. A pulsation occurs in the gas.

In addition, the fuel gas supply passage for supplying the raw fuel gas includes a pressure regulator for adjusting the pressure of the raw fuel gas to be supplied, an electromagnetic valve for stopping the supply of the raw fuel gas, and a A check valve or the like for preventing backflow is incorporated, and a vaporizer for vaporizing the reforming water is incorporated on the upstream side of the cell stack. Springs are incorporated in these pressure control valves, solenoid valves, check valves, etc. This spring causes pulsation of the raw fuel gas, and in the vaporizer, the volume expansion when vaporizing and generating steam is the cause. It causes pulsation of fuel gas.

For this reason, if pulsation occurs in the raw fuel gas, it becomes impossible to accurately measure the supply flow rate. However, if this pulsation increases and hunting occurs in the fuel flow rate, the fuel gas flow rate sensor (fuel gas flow meter) is used to accurately measure the fuel flow rate. Therefore, the supply flow rate of the raw fuel gas may drop significantly below the fuel flow rate command value. In particular, when operating with a high fuel utilization rate, if the supply flow rate of the raw fuel gas drops significantly, the fuel utilization rate rises significantly, which causes fatal damage to the cell stack. may receive This fuel flow rate hunting is caused by a complex combination of the above conditions, and it is difficult to completely eliminate such conditions.

For this reason, conventionally, the fuel flow rate hunting is dealt with as follows. In general, when fuel flow rate hunting occurs, the absolute moving average of the flow rate difference between the fuel flow rate command value and the measured value of the fuel gas flow rate sensor increases. When the value exceeds the value, an error determination is performed assuming that the supply flow rate of the raw fuel gas cannot be properly controlled, and the system error stop processing is performed based on this error determination.

However, since the number of home fuel cell systems installed is large, if this error stop occurs frequently, the number of dispatches for maintenance and inspection by the manufacturer (or the seller) will increase, and economic efficiency will deteriorate. Therefore, when fuel flow rate hunting occurs, instead of making an error stop on the safe side to protect the cell stack, if the fuel flow rate hunting is not remarkable, it is operated so that fuel shortage does not occur without making an error judgment. is desired.

SUMMARY OF THE INVENTION An object of the present invention is to provide a solid oxide fuel cell system capable of reducing the frequency of system error shutdowns while sufficiently suppressing the occurrence of cell stack damage caused by fuel flow rate hunting.

A solid oxide fuel cell system according to claim 1 of the present invention comprises: a reformer for steam reforming raw fuel gas; a vaporizer for generating steam used for steam reforming; a cell stack for generating electricity by oxidation and reduction of the reformed fuel gas reformed in the reformer and oxygen in the air; fuel gas supply means for supplying the raw fuel gas to the reformer; and the cell stack air supply means for supplying air to the cell stack; fuel gas flow rate measurement means for measuring the flow rate of the raw fuel gas supplied by the fuel gas supply means; and fuel off-gas and air off-gas after the power generation reaction in the cell stack. A solid oxide fuel cell system comprising an off-gas combustion unit for burning and a controller for controlling the operation of the fuel gas supply means and the air supply means,
The controller includes flow rate difference computing means for computing the flow rate difference between the fuel flow rate command value and the measured flow rate of the fuel gas flow rate measuring means, and an absolute value moving average of the flow rate difference computed by the flow rate difference computing means. value moving average calculation means; moving average comparison means for comparing the absolute value moving average value S calculated by the absolute value moving average calculation means with the caution judgment value K and the error judgment value E; and error stop signal generation means for generating an error stop signal for performing error stop processing,
When the absolute value moving average value S exceeds the error determination flow rate value E (E<S), the error stop signal generating means generates the error stop signal, and the error stop processing is performed based on the error stop signal. Further, when the absolute value moving average value S exceeds the warning determination value K and is equal to or less than the error determination value (K<S≤E), the warning driving signal generating means generates the warning driving signal, The caution driving is performed based on the caution driving signal.

Further, in the solid oxide fuel cell system according to claim 2 of the present invention, the offgas combustion section is an offgas combustion zone from which fuel offgas and air offgas are led out from the cell stack. is combusted in the offgas combustion zone.

Further, in the solid oxide fuel cell system according to claim 3 of the present invention, temperature detection means for detecting a temperature related to the cell stack is provided, and the temperature detection means detects the temperature of the offgas combustion zone. Combustion zone temperature detection means for detection, exhaust combustion part temperature detection means for detecting the temperature of the exhaust combustion part that burns the discharged fuel off-gas, and cell stack temperature detection means for detecting the temperature of the cell stack wherein the controller further includes partial misfire determination means for determining the occurrence of a partial misfire in the offgas combustion zone,
The partial misfire determination means determines whether the detected temperature T1 of the combustion zone temperature detection means is lower than a first partial misfire determination temperature value TB1 (T1<TB1), and the detection of the exhaust combustion part temperature detection means. Based on whether the temperature T2 exceeds the second partial misfire determination temperature value TB2 (TB2<T2), and whether the detected temperature T3 of the cell stack temperature detecting means is lower than the third partial misfire determination temperature value TB3 (T3 <TB3) is used to determine partial misfire.

Further, in the solid oxide fuel cell system according to claim 4 of the present invention, the temperature detection means includes the combustion zone temperature detection means, the exhaust combustion part temperature detection means, and the cell stack temperature detection means, The partial misfire determination means is configured so that the detected temperature T1 of the combustion zone temperature detection means is lower than the first partial misfire determination temperature value TB1 (T1<TB1), and the detected temperature T2 of the exhaust combustion portion temperature detection means Three conditions that the second partial misfire determination temperature value TB2 is exceeded (TB2<T2) and the detection temperature T3 of the cell stack temperature detection means is lower than the third partial misfire determination temperature value TB3 (T3<TB3) Partial misfire determination is performed when any one of the conditions is satisfied, any two conditions are satisfied, or all three conditions are satisfied.

Further, in the solid oxide fuel cell system according to claim 5 of the present invention, the controller further comprises a fuel gas increase correction setting for increasing the supply flow rate of the raw fuel gas supplied to the cell stack. means for increasing and correcting a supply flow rate of the raw fuel gas supplied to the cell stack when the partial misfire determination means determines a partial misfire during the warning operation. characterized by

According to the solid oxide fuel cell system according to claim 1 of the present invention, the controller for controlling the operation of the fuel gas supply means and the air supply means comprises the flow rate difference calculation means, the absolute value moving average calculation means, and the moving average calculation means. The flow rate difference calculation means calculates the flow rate difference between the fuel flow rate command value and the measured flow rate of the fuel gas flow rate measurement means, and the absolute value moving average calculation means calculates the flow rate difference calculated by the flow rate difference calculation means. Since the absolute value moving average is calculated, when fuel flow rate hunting occurs, this flow rate difference occurs. The moving average for about a second) also increases, and by using the absolute value moving average of this flow rate difference, it is possible to investigate the occurrence of fuel flow rate hunting.

Then, the moving average comparing means compares the absolute value moving average value S of the flow rate difference calculated by the absolute value moving average calculating means with the warning judgment value K and the error judgment value E, and this absolute value moving average value S is When the error determination flow rate value E is exceeded (E<S), the error stop signal generating means generates an error stop signal and error stop processing is performed, so damage to the cell stack due to fuel shortage caused by fuel flow rate hunting can be prevented. can be suppressed. Further, when the absolute value moving average value S exceeds the warning determination value K and is equal to or less than the error determination value (K<S≤E), the warning driving signal generating means generates a warning driving signal. Since the warning operation is carried out based on this, it is possible to monitor the state of occurrence of fuel hunting in this warning operation, and to suppress the adverse effect of the fuel flow rate hunting to a minimum.

Further, according to the solid oxide fuel cell system of claim 2 of the present invention, since the offgas combustion section is the offgas combustion zone from which the fuel offgas and air offgas are led out from the cell stack, this offgas combustion zone The fuel off-gas from the cell stack can be combusted by the air off-gas at .

Further, according to the solid oxide fuel cell system according to claim 3 of the present invention, the temperature detection means for detecting the temperature related to the cell stack includes a combustion zone temperature detection means for detecting the temperature of the offgas combustion zone. means, at least one of exhaust combustion part temperature detection means for detecting the temperature of the exhaust combustion part that burns the discharged fuel off-gas, and cell stack temperature detection means for detecting the temperature of the cell stack. The combustion state of the fuel off-gas in the off-gas combustion section can be detected using this temperature detection means. Further, the partial misfire determination means determines whether or not the detected temperature T1 of the combustion zone temperature detection means is lower than the first partial misfire determination temperature value TB1 (T1<TB1). Based on whether T2 exceeds the second partial misfire determination temperature value TB2 (TB2<T2), and for the cell stack temperature detection means, whether the detection temperature T3 is lower than the third partial misfire determination temperature value TB3 (T3<TB3 ), it is possible to detect the occurrence of a partial misfire in the offgas combustion section.

Further, according to the solid oxide fuel cell system according to claim 4 of the present invention, the temperature detection means includes combustion zone temperature detection means, exhaust combustion part temperature detection means, and cell stack temperature detection means, and partial misfire is detected. The determination means determines that the detection temperature T1 of the combustion zone temperature detection means is lower than the first partial misfire determination temperature value TB1 (T1<TB1), and the detection temperature T2 of the exhaust combustion temperature detection means is lower than the second partial misfire determination temperature value TB2. (TB2<T2), and the detection temperature T3 of the cell stack temperature detection means is lower than the third partial misfire determination temperature value TB3 (T3<TB3). or when all three conditions are satisfied, the detection temperatures T1, T2, T1, T2, Occurrence of a partial misfire in the offgas combustion zone can be reliably detected based on T3.

Furthermore, according to the solid oxide fuel cell system according to claim 5 of the present invention, when the partial misfire determination means determines a partial misfire during caution operation, the fuel gas increase correction setting means supplies fuel gas to the cell stack. Since the supply flow rate of the raw fuel gas supplied to the cell stack is increased, the supply flow rate of the raw fuel gas supplied to the cell stack is increased. can be kept to a minimum.

BRIEF DESCRIPTION OF THE DRAWINGS The whole view which shows simply the whole 1st Embodiment of the solid oxide fuel cell system according to this invention. FIG. 2 is a block diagram schematically showing a control system of the solid oxide fuel cell system of FIG. 1; FIG. 3 is a flow chart showing the flow of control of the system by the control system of FIG. 2; FIG. FIG. 2 is a block diagram schematically showing a control system of a second embodiment of the solid oxide fuel cell system according to the invention; FIG. 5 is a flow chart showing part of the flow of control by the control system in FIG. 4 ; FIG.

An embodiment of a solid oxide fuel cell system according to the present invention will be described below with reference to the accompanying drawings. First, referring to FIG. 1, the solid oxide fuel cell system of the first embodiment will be described.

In FIG. 1, the illustrated solid oxide fuel cell system 2 consumes raw fuel gas (for example, city gas, LP gas, etc.) to generate power. and a solid oxide cell stack 6 for generating electricity by oxidation and reduction of the reformed fuel gas reformed by the reformer 4 and air as an oxidant.

The cell stack 6 is configured by stacking a plurality of solid oxide fuel cells 8 for generating power through a fuel cell reaction via current collecting members. A fuel electrode 12 is provided on one side of an electrolyte 10, and an air electrode 14 is provided on the other side of the solid electrolyte. As the solid electrolyte 10, yttria-doped zirconia is used.

The fuel electrode 12 side of the cell stack 6 is connected to the reformer 4 through a reformed fuel gas feed passage 16. In this embodiment, the reformer 4 is a vaporizer for vaporizing reforming water. 18 and integrally configured. The vaporizer 18 is configured separately from the reformer 4, and the vapor vaporized by the vaporizer 18 is fed to the reformer 4 through a vapor feed passage (not shown). may

The vaporizer 18 is connected to a fuel gas supply source (not shown) for supplying raw fuel gas through a fuel gas supply channel 20 (consisting of, for example, an embedded pipe or a storage tank), and Raw fuel gas from a gas supply source is supplied to the vaporizer 18 through a fuel gas supply passage 20 . The fuel gas supply passage 20 may be connected to the reformer 4 to directly supply the raw fuel gas from the fuel gas supply source to the reformer 4 .

In addition, the vaporizer 18 is connected to a water supply source (not shown) (consisting of, for example, a water tank, a water recovery tank, etc.) through a water supply channel 22, and reforming from the water supply source is performed. Service water is supplied to the vaporizer 18 through the water supply channel 22 . A reforming catalyst is housed in the reformer 4. For example, a reforming catalyst in which ruthenium is supported on alumina is used. It is steam reformed by steam.

The fuel gas supply passage 20 includes, in order from the carburetor 18 toward the upstream side, a desulfurizer 24, a throttle member 26, a fuel gas pump 28 (constituting fuel gas supply means), a zero governor 30 as a pressure regulating member, and fuel gas. A flow rate sensor 32 (constituting fuel gas flow rate measuring means) and a cutoff valve 34 are provided. The desulfurizer 24 removes the sulfur component contained in the raw fuel gas (the sulfur component in the odorant), and the fuel gas pump 28 pressurizes the raw fuel gas flowing through the fuel gas supply passage 20 to the vaporizer 18. supply.

In addition, the zero governor 30 adjusts the raw fuel gas supplied from a fuel gas supply source (not shown) through the fuel gas supply passage 14 to a predetermined pressure (near atmospheric pressure), and the fuel gas flow rate sensor 32 detects the fuel gas The flow rate of the raw fuel gas supplied through the supply channel 14 is measured, and when the shutoff valve 32 is closed, it shuts off the fuel gas supply channel 20 to stop the supply of fuel gas. A throttle member 26 located downstream of the fuel gas pump 28 is provided for stabilizing the flow rate of the raw fuel gas flowing through the fuel gas supply passage 14, and a capillary tube, for example, is used as the throttle member 26. Further, the fuel gas flow rate sensor 32 can be composed of, for example, a thermal flow rate sensor.

Further, a water pump 36 is provided in the water supply channel 22, and the water pump 36 supplies reforming water from a water supply source (not shown) through the water supply channel 22 to the vaporizer 18. . When the raw fuel gas can be stably supplied, the throttle member 26 may be omitted, or a throttle member or a buffer tank may be provided upstream of the zero governor 30. .

The air electrode 14 side of the cell stack 6 is connected through an air supply passage 38 to an air blower 40 as air supply means. ) are provided. The air blower 40 supplies air as an oxidant through the air supply channel 38 to the air electrode 14 side of the cell stack 6 , and the air flow rate sensor 42 measures the flow rate of the air flowing through the air supply channel 38 .

In this embodiment, the rotation control of the fuel gas pump 28 (and water pump 36, air blower 40) is controlled by the duty ratio of the drive current (so-called drive duty ratio). (and water pump 36, air blower 40) increases, the supply flow rate of raw fuel gas (and reforming water, air) increases, while the driving duty ratio decreases, fuel gas pump 28 (and water pump 36) , the rotation speed of the air blower 40) becomes small, and the supply flow rate of the raw fuel gas (and reforming water and air) is small. be.

An offgas combustion zone 44 (constituting an offgas combustion section) is arranged above the cell stack 6 , and the reformer 4 and the vaporizer 18 are arranged above this offgas combustion zone 44 . The fuel off-gas (that is, anode off-gas) led out from the fuel electrode 12 side of the cell stack 6 flows into this off-gas combustion zone 44, and the air off-gas (that is, cathode off-gas) led out from the air electrode 14 side of the cell stack 6 ) also flows into this offgas combustion zone 44, where fuel offgas (containing fuel gas) from the fuel electrode 12 side of the cell stack 6 is converted into air offgas (oxygen gas) from the air electrode 14 side. ), and the carburetor 12 and the reformer 4 are heated using the combustion heat of this fuel off-gas.

Combustion exhaust gas combusted in the offgas combustion zone 44 is discharged to the atmosphere through an exhaust gas discharge passage 46 . The exhaust gas discharge passage 46 is provided with an exhaust combustion unit 48 as an off-gas combustion unit. Although not shown, the exhaust combustion unit 48 burns fuel off-gas (fuel gas contained in the combustion exhaust gas). A combustion catalyst is provided for promoting the Accordingly, the combustion exhaust gas discharged through the exhaust gas discharge passage 46 is combusted in the discharge combustion section 48, and the combustion exhaust gas in which the fuel gas components are completely combusted is discharged into the atmosphere.

In this embodiment, a heat exchanger 50 (air heat exchanger) is provided in relation to this exhaust gas discharge passage 46 . The heat exchanger 50 exchanges heat between the combustion exhaust gas flowing through the exhaust gas discharge passage 46 and the air flowing through the air supply passage 38 , and the air heated by this heat exchange is the air in the cell stack 6 . It is fed to the pole 14 side.

In this embodiment, reformer 4 , cell stack 6 , vaporizer 18 and heat exchanger 50 are housed in high temperature housing 52 . The high-temperature housing 52 is made of metal (for example, stainless steel), and its inner surface is covered with a heat-insulating member to define a high-temperature space 54 therein, which contains the reformer 4, the cell stack 6, the vaporizer 18, and the high-temperature space 54. The heat exchanger 50 is kept hot in the hot space 54 .

The solid oxide fuel cell system 2 is further configured such that part of the reformed fuel gas supplied from the reformer 4 to the cell stack 6 flows through the fuel gas supply channel 20 . A return flow path 56 is provided by branching from the reformed fuel gas supply flow path 16, and the downstream side of the return flow path 56 is the fuel gas supply flow path 20 (specifically, the location of the zero governor 30 and the fuel gas pump). 28). The return channel 56 is led out of the high temperature housing 52 and connected to the fuel gas supply channel 20, and a drain separator 58 is provided in the return channel 56 (specifically, a portion outside the high temperature housing 52). It is

With this configuration, part of the reformed fuel gas flowing through the reformed fuel gas supply channel 38 flows through the return channel 56 to the fuel gas supply channel 20 and through the return channel 56. During this time, it is cooled by the atmosphere, and the water vapor contained in the reformed fuel gas is condensed by the cooling. The generated condensed water is removed by the drain separator 58 , and the reformed fuel gas from which the condensed water has been removed is returned to the fuel gas supply channel 20 and mixed with the raw fuel gas flowing through the fuel gas supply channel 20 . Although the condensed water removed by the drain separator 58 may be discharged to the outside, it is recovered in a water recovery tank (not shown), and the recovered condensed water is used as reforming water. may

Next, the power generation operation of this solid oxide fuel cell system 2 will be described. During power generation operation, raw fuel gas from a fuel gas supply source (not shown) is supplied by the fuel gas pump 28 through the fuel gas supply passage 20, and the raw fuel gas thus supplied is supplied in the manner described above. The reformed fuel gas recycled through the return passage 56 is mixed, the mixed mixed fuel gas is sent to the fuel gas pump 28, and the mixed fuel gas pressurized by the fuel gas pump 28 is desulfurized through the fuel gas supply passage 20. is fed to vessel 24.

In the desulfurizer 24, the sulfur component contained in the mixed fuel gas is removed by the desulfurizing agent. Since the mixed fuel gas to be desulfurized contains hydrogen (in other words, it contains the reformed fuel gas), the desulfurizing agent stably exerts an excellent desulfurization effect and removes the sulfur contained in the mixed fuel gas. It is possible to remove the residual sulfur component as desired.

The raw fuel gas (mixed fuel gas) desulfurized by the desulfurizer 24 is supplied to the vaporizer 18 through the fuel gas supply passage 20 . The vaporizer 18 is also supplied with reforming water through a water supply passage 22, vaporized by the vaporizer 18 into steam, and the generated steam and raw fuel gas (mixed fuel gas) are mixed. It is sent to the reformer 4 .

In the reformer 4 , the raw fuel gas (mixed fuel gas) is steam-reformed by steam, and the steam-reformed raw fuel gas passes through the reformed fuel gas feed passage 16 to the fuel electrode 12 side of the cell stack 6 . , and part of the reformed fuel gas flowing through the reformed fuel gas supply channel 16 is recycled to the fuel gas supply channel 20 through the return channel 56 . Also, air is supplied through an air supply channel 38 to the air electrode 14 side of the cell stack 6 .

In the cell stack 6, power is generated by oxidation and reduction of the reformed fuel gas flowing on the fuel electrode 12 side and the air (oxygen in the air) flowing on the air electrode 14 side. Although not shown, the AC power is converted into AC power through a power conditioner and supplied to a household demand end.

The fuel off-gas (containing fuel gas) from the fuel electrode 12 of the cell stack 6 and the air off-gas from the air electrode 14 side flow into the off-gas combustion zone 44, where the fuel off-gas is converted by the air off-gas. Combusted, the combustion exhaust gases from the offgas combustion zone 44 are discharged to the atmosphere through exhaust gas discharge passages 46 .

During the power generation operation, in the heat exchanger 50, heat is exchanged between the combustion exhaust gas flowing through the exhaust gas discharge passage 46 and the air flowing through the air supply passage 38, and the heat is heated by this heat exchange. Air is fed to the cathode 14 side of the cell stack 6 .

In the solid oxide fuel cell system of the first embodiment, the combustion exhaust gas from the offgas combustion area 44 is discharged as it is through the exhaust gas discharge passage 46. A heat recovery heat exchanger (not shown) is provided, and a hot water storage device is provided in relation to this heat recovery heat exchanger. and water from the hot water storage device, and by this heat exchange, exhaust heat of the combustion exhaust gas may be recovered and stored as hot water in the hot water storage device.

Further, in the first embodiment, the fuel off-gas from the fuel electrode 12 of the cell stack 6 and the air off-gas from the air electrode 14 are burned in the off-gas combustion zone 44 above the cell stack 6. Instead of such a configuration, an offgas combustor (not shown) is provided as an offgas combustion unit, and the fuel offgas from the fuel electrode 12 side of the cell stack 6 is passed through a fuel offgas feed passage (not shown) to the offgas combustor. , the air off-gas from the air electrode 14 side is fed to the off-gas combustor through an air off-gas feeding passage (not shown), and the fuel off-gas is combusted by the air off-gas in this off-gas combustor. You may do so.

Further, in the first embodiment, part of the reformed fuel gas supplied to the cell stack 6 is returned to the fuel gas supply channel 20 through the return channel 56, but this configuration is not necessarily required. Instead, the return flow path 56 may be omitted.

In this solid oxide fuel cell system 2, in order to reduce the frequency of system error stop caused by fuel flow rate hunting of the raw fuel gas flowing through the fuel gas supply channel 20, the system is further configured as follows. there is

2 together with FIG. 1, temperature detection means 62 for detecting the combustion state of the fuel off-gas is provided in relation to the cell stack 6 . In this first embodiment, the temperature detection means 62 is composed of a combustion zone temperature detection sensor 64 (constituting combustion zone temperature detection means) for detecting the temperature of the offgas combustion zone 44. This combustion zone temperature detection sensor 64 is disposed in offgas combustion zone 44 .

A detection signal from the temperature detection means 62 (combustion zone temperature detection sensor 64) is sent to a controller 66 for controlling the system. A detection signal from an air flow rate sensor 42 (air flow rate measuring means) is also sent.

The illustrated controller 66 is composed of, for example, a microprocessor and the like, and includes operation control means 68, fuel utilization rate setting means 70, flow rate difference calculation means 72, absolute value moving average calculation means 74, moving average comparison means 76, warning operation signal. It includes generating means 78 and error stop signal generating means 80 . The operation control means 68 operates and controls the fuel gas pump 28, the air blower 40 and the water pump 36, and uses the flow rate measured by the fuel gas flow rate sensor 32, for example, to control the operation of the fuel gas pump 28 as will be described later.

Further, the fuel utilization factor setting means 70 sets the fuel utilization factor of the raw fuel gas consumed in the cell stack 6 . This fuel utilization rate is the ratio of the raw fuel gas supplied to the cell stack 6 that contributes to power generation in the cell stack 6 (that is, the ratio consumed in the fuel electrode 12), and is the generated current of the cell stack 6. It is a value determined by the fuel flow rate.

Furthermore, the flow rate difference calculation means 72 calculates the flow rate difference between the fuel flow rate command value set based on this fuel utilization rate and the flow rate value measured by the fuel gas flow rate sensor 32, and the absolute value moving average calculation means 74 calculates this An absolute value moving average of the flow rate difference, eg, a moving average over 2 to 10 seconds (eg, 5 seconds) is calculated. When fuel flow rate hunting occurs in the fuel gas flowing through the fuel gas supply passage 20, the flow rate difference between this fuel flow rate command value and the flow rate value measured by the fuel gas flow rate sensor 32 increases. The moving average also increases, and the occurrence of fuel flow rate hunting is detected using the absolute value moving average of this flow rate difference.

Further, the moving average comparing means 76 compares the absolute value moving average value S of the flow rate difference calculated by the absolute value moving average calculating means 74 with the warning determination value K and the error determination value E. The error judgment value E is a value for judging that fuel flow rate hunting has occurred and the fuel flow rate sensor 32 cannot measure the fuel flow rate. It is a value for judging that the fuel flow rate can be measured by the fuel gas flow rate sensor 32 but cannot be measured accurately, and is set to a value of about 30 to 60% of the error determination value E, for example.

In this embodiment, when the absolute value moving average value S of the flow rate difference exceeds the error judgment value E (E<S), large fuel flow rate hunting occurs, and an error occurs because the supply flow rate of the raw fuel gas cannot be controlled. A stop signal generating means 80 generates an error stop signal. Further, when the absolute value moving average value S of the flow rate difference is equal to or less than the error determination value E and exceeds the warning determination value K (K<S≦E), a slight fuel flow rate hunting occurs and a large fuel flow rate hunting occurs. The cautionary driving signal generating means 78 generates a cautionary driving signal as it is necessary to monitor whether there is a possibility of becoming.

The controller 66 further includes temperature comparison means 82 , partial misfire determination means 84 , misfire determination means 86 , fuel gas increase correction setting means 88 , timer means 90 and memory means 92 . The temperature comparison means 82 compares the detection temperature value T measured by the combustion zone temperature detection sensor 64 (temperature detection means 62) with the partial misfire determination temperature value TB and the misfire determination temperature value TS. The partial misfire determination temperature value TB is a temperature value at which it is determined that the combustion state of the fuel off-gas in the off-gas combustion region 44 is partially misfired. When it is around 750°C, the partial misfire determination temperature value TB is set to around 670°C, for example. Further, the misfire determination temperature value TS is a temperature value for determining that the combustion state of the fuel off-gas is misfiring, and this misfire determination temperature TS is lower than the partial misfire determination temperature value TB by approximately 20 to 30°C. For example, it is set around 650°C.

Further, the partial misfire determination means 84 determines a partial misfire when the detected temperature value T of the combustion zone temperature detection sensor 62 is lower than the partial misfire determination temperature value TB and equal to or higher than the misfire determination temperature value TS. The determination means 86 determines misfire when the detected temperature value T becomes lower than the misfire determination temperature value TS.

Furthermore, the timer 90 measures time, for example, the moving average time (for example, 5 seconds) when calculating the absolute value moving average of the flow rate difference. In addition, the memory means 92 stores various determination reference values such as a warning determination value K, an error determination value E, a partial misfire determination temperature value TB, and a misfire determination temperature value TS.

Next, mainly with reference to FIGS. 2 and 3, operation of the solid oxide fuel cell system 2 described above will be described. In the operation of the fixed oxide fuel cell system 2, the fuel utilization rate is set by the fuel utilization rate setting means 70 of the controller 66 (step S1), and the cell stack 6 generates power so as to achieve the set fuel utilization rate. Operation is performed (step S2). That is, the operation control means 68 operates the fuel gas pump 28 to control the supply flow rate of the raw fuel gas and operates the air blower 40 to supply air so that the power generation operation is performed at the set fuel utilization rate. The flow rate is controlled and the water pump 36 is operated to control the reforming water supply flow rate.

During this operation, the fuel gas flow rate sensor 32 (fuel gas flow rate measuring means) measures the supply flow rate of the raw fuel gas supplied through the fuel gas supply passage 20 (step S3). is sent to controller 66 . When the measurement signal is sent in this way, the flow rate difference calculation means 72 calculates the flow rate difference between the fuel flow rate command value and the measured flow rate value of the fuel gas flow rate sensor 32 (step S4), and the absolute value moving average calculation means 74 calculates the absolute value moving average value S of the flow rate difference over, for example, 5 seconds (step S5).

When the absolute value moving average value S of the flow rate difference is calculated in this manner, the moving average comparison means 76 compares the absolute value moving average value S of the flow rate difference with the warning determination value K (step S6). If the absolute value moving average value S of the flow rate difference is equal to or less than the alarm judgment value K (S≦K), it is determined that the raw fuel gas supply flow rate is accurately measured and fuel flow rate hunting does not occur, and the step is taken. From S7, the process returns to step S3, and the above-described steps S3 to S7 are repeatedly performed.

If the absolute value moving average value S of the flow rate difference exceeds the caution determination value K (K<S), the process proceeds from step S7 to step S8, and the moving average comparison means 76 next determines the absolute value of the flow rate difference The moving average value S and the error determination value E are compared. If the absolute moving average value S of the flow rate difference exceeds the error judgment value E (E<S), the fuel flow rate hunting occurs greatly and the supply flow rate of the raw fuel gas cannot be measured. Then, the process proceeds from step S9 to step S10. At this time, an error determination is performed based on the comparison result of the moving average comparison means 72, the error stop signal generation means 80 generates an error stop signal based on the error determination, and the solid oxide fuel is generated based on the error stop signal. The error stop processing of the battery system 2 is performed as required.

On the other hand, if the moving average value S of the flow rate difference is equal to or less than the error determination value E (S≦E) (that is, the moving average value S of the flow rate difference exceeds the warning determination value K and is equal to or less than the error determination value E). , the process moves from step S9 to step S12. At this time, since it is necessary to monitor whether the fuel flow rate hunting occurs a little and becomes large, a warning judgment is made based on this comparison result. is generated, and the warning operation of the solid oxide fuel cell system 2 is performed based on this warning operation signal. The hunting state of the fuel flow rate is monitored while watching.

When the warning operation is performed, the combustion zone temperature detection sensor 64 (temperature detection means 62) detects the temperature of the offgas combustion zone 44 (step S13), and the detection signal is sent to the controller 66. When the detection signal is sent in this manner, the temperature comparison means 82 compares the temperature value T detected by the combustion zone temperature detection sensor 62 with the partial misfire determination temperature value TB (step S14).

When the detected temperature value T is equal to or higher than the partial misfire determination temperature value TB (TB≤T), the offgas combustion region 44 is maintained at a desired temperature state. It means that the fuel off-gas from the electrode 12 side is properly combusted by the air off-gas from the air electrode 14 side. S15 is repeatedly performed, and this caution driving is continued.

During this warning operation, when the absolute value moving average value S of the flow rate difference becomes equal to or less than the warning judgment value K (S≤K), it is assumed that the fuel flow rate hunting has stopped and the process returns from step S7 to step S3, and the system is put into warning operation. finish.

Further, when the detection temperature value T of the combustion zone temperature detection sensor 64 becomes lower than the partial misfire determination temperature value TB (for example, 670° C.) during this warning operation (T<TB), the process proceeds from step S15 to step S16, and the temperature The comparison means 82 then compares the detected temperature value T of the combustion zone temperature detection sensor 64 with the misfire determination temperature value TS. If the detected temperature value T is lower than the misfire determination temperature value TS (T<TS), the combustion temperature of the offgas combustion region 44 is greatly reduced, and the fuel offgas is considered to be in a misfired state, and steps from step S17 to step S17 are performed. Proceed to S18. At this time, the misfire determination means 86 performs misfire determination based on the comparison result of the temperature comparison means 82, and the misfire stop processing of the solid oxide fuel cell system 2 is performed as required based on this misfire determination (step S19).

On the other hand, the detected temperature value T of the combustion zone temperature detection sensor 64 is equal to or higher than the misfire determination temperature value TS (TS≤T) (that is, the detected temperature value T is lower than the partial misfire temperature value TB and equal to or higher than the misfire determination temperature value TS). ), the combustion temperature of the off-gas combustion zone 44 decreases and the fuel off-gas is in a partial misfire state, and the process proceeds from step S17 to step S20. At this time, the partial misfire judging means 84 makes a partial misfire judgment based on the judgment result, and corrects to increase the amount of fuel gas so as to eliminate the partial misfire state and return to a stable combustion state (step S21).

That is, the fuel gas amount increase correction setting means 88 performs an amount increase correction of the supply flow rate of the raw material gas (this amount increase correction may be performed, for example, by lowering the fuel utilization rate set by the fuel utilization rate setting means. ), thereby increasing the amount of fuel gas passing through the fuel electrode 12 side of the cell stack 6 and flowing into the offgas combustion area 44, returning the combustion of the fuel offgas to a stable state, and then returning to step S13.

By increasing the supply flow rate of the fuel gas when a partial misfire occurs during warning operation in this way, it is possible to suppress partial misfires or misfires due to this fuel flow hunting (in other words, suppress the adverse effects of fuel shortage). This makes it possible to increase the setting value for error determination as compared with the conventional art, and as a result, it is possible to reduce the frequency of system error stop caused by fuel flow rate hunting.

Next, a second embodiment of the solid oxide fuel cell system according to the present invention will be described with reference to FIGS. 4 and 5. FIG. In this second embodiment, the temperature detection means includes, in addition to a combustion zone temperature detection sensor that detects the combustion temperature of the offgas combustion zone, an exhaust combustion part temperature detection sensor that detects the temperature of the exhaust combustion part and a cell stack temperature sensor that detects the temperature of the exhaust combustion part. A partial misfire state and a misfire state of the combustion off-gas are detected based on the temperatures detected by the combustion zone temperature detection sensor, the exhaust combustion part temperature detection sensor and the cell stack temperature detection sensor. is configured as In the second embodiment, members substantially the same as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 4, in the solid oxide fuel cell system of the second embodiment, a combustion zone temperature detection sensor 64, an exhaust combustion section temperature detection sensor 102 and a cell stack temperature detection sensor 104 are used as temperature detection means 62A.

The combustion zone temperature detection sensor 64 is arranged in the offgas combustion zone 44 (see FIG. 1) in the same manner as described above, and detects the combustion temperature in this offgas combustion zone 44 . When the combustion state of the off-gas combustion zone 44 becomes unstable and a partial misfire occurs, the combustion temperature of the off-gas combustion zone 44 decreases. . For this reason, in relation to the combustion zone temperature detection sensor 64, a first partial misfire determination temperature value TB1 (for example, around 670° C.) that serves as a reference for partial misfire determination and a first misfire determination temperature value TB1 that serves as a reference for misfire determination. A judgment temperature value TS1 (for example, around 650° C.) is set.

The exhaust combustion part temperature detection sensor 102 is arranged near the combustion catalyst (not shown) of the exhaust combustion part 48 (see FIG. 1) and detects the combustion temperature in this exhaust combustion part 48 . When the combustion state in the offgas combustion zone 44 becomes unstable and a partial misfire occurs, the fuel offgas is not completely burned in the offgas combustion zone 44, but flows to the exhaust combustion section 48 and is burned. When the combustion temperature in the combustion section 48 rises and this combustion state becomes more unstable and misfire occurs, the amount of fuel off-gas flowing to the exhaust combustion section 48 increases and the combustion temperature further rises. For this reason, in relation to this exhaust combustion section temperature detection sensor 102, a second partial misfire determination temperature value TB2 (for example, around 210° C.) that serves as a reference for partial misfire determination and a second partial misfire determination temperature value TB2 that serves as a reference for misfire determination. A misfire determination temperature value TS2 (for example, around 280° C.) is set.

A cell stack temperature detection sensor 104 is arranged near the cell stack 6 (see FIG. 1) to detect the operating temperature of the cell stack 6 . If the combustion state in the offgas combustion area 44 becomes unstable and a partial misfire occurs, the combustion temperature in the offgas combustion area 44 decreases and the cell stack 6 cannot be maintained at a high temperature. If the operating temperature of is lowered and this combustion condition becomes more unstable and a misfire occurs, the combustion temperature of the off-gas combustion zone 44 is further lowered, thereby further lowering the operating temperature of the cell stack 6 . For this reason, in relation to the cell stack temperature detection sensor 104, a third partial misfire determination temperature value TB3 (for example, around 640° C.) that serves as a reference for partial misfire determination, and a third fire temperature value TB3 that serves as a reference for misfire determination. A judgment temperature value TS3 (for example, around 630° C.) is set. These first to third partial misfire determination temperature values TB1, TB2, TB3 and first to third misfire determination temperature values TS1, TS2, TS3 are registered in the memory means 92A.

In the second embodiment, in relation to the configuration described above, the temperature comparison means 82 detects the temperature T1 detected by the combustion zone temperature detection sensor 64 as the first partial misfire determination temperature value TB1 and the first misfire determination temperature value TS1. , the detection temperature T2 of the exhaust combustion part temperature detection sensor 102 is compared with the second partial misfire determination temperature value TS2 and the second misfire determination temperature value TS2, and the detection temperature of the cell stack temperature detection sensor 104 is compared. The temperature T3 is compared with the third partial misfire determination temperature value TB3 and the third misfire determination temperature value TS3. Other configurations of this second embodiment are substantially the same as those of the above-described first embodiment.

Next, with reference to FIG. 5 together with FIG. 4, operation of the solid oxide fuel cell system of the second embodiment will be described. Operation of the solid oxide fuel cell system of the second embodiment differs from that of the first embodiment only in caution operation. is calculated, the absolute value moving average value S of this flow rate difference is calculated, the absolute value moving average value S of the calculated flow rate difference is compared with the warning judgment value K and the error judgment value E, and the absolute value movement of the flow rate difference When the average value S exceeds the warning judgment value K and is equal to or less than the error judgment value (K<S≤E), the warning operation is performed. control to process. This warning driving, which is different from the first embodiment, will be described below.

In this warning operation, operation is performed because it is necessary to monitor whether fuel flow rate hunting occurs a little and increases, and the temperature detection means 62A detects the temperature of a predetermined portion (step S31). That is, the combustion zone temperature detection sensor 64 detects the temperature of the offgas combustion zone 44 (FIG. 1), the exhaust combustion part temperature detection sensor 102 detects the temperature of the exhaust combustion part 48 (FIG. 1), and the cell stack temperature detection sensor A reference numeral 104 detects the temperature of the cell stack 6 (FIG. 1), and detection signals from the combustion zone temperature detection sensor 64, the exhaust combustion part temperature detection sensor 102 and the cell stack temperature detection sensor 104 are sent to the controller 66A.

When these detection signals are sent, the temperature comparing means 82 compares the temperature value T1 detected by the combustion zone temperature detection sensor 62 with the first partial misfire determination temperature value TB1, and the temperature detected by the cell stack temperature detection sensor 104 is compared. The temperature value T3 is compared with the third partial misfire determination temperature value TB3 (step S32). Then, the temperature value T1 detected by the combustion zone temperature detection sensor 62 is lower than the first partial misfire determination temperature value TB1 (T1<TB1), or the temperature value T3 detected by the cell stack temperature detection sensor 104 is the third partial misfire determination temperature. If it is lower than the value TB3 (T3<TB3), the process proceeds from step S33 to step S34, and then the temperature comparison means 82 compares the detected temperature value T1 of the combustion zone temperature detection sensor 62 and the first misfire determination temperature value TS1. Also, the temperature value T3 detected by the cell stack temperature detection sensor 104 is compared with the third misfire determination temperature value TBS.

The detection temperature value T1 of the combustion zone temperature detection sensor 62 is lower than the first misfire determination temperature value TS1 (T1<TS1), or the detection temperature value T3 of the cell stack temperature detection sensor 104 is higher than the third misfire determination temperature value TS3. If it is low (T3<TS3), the process proceeds from step S35 to step S36 assuming that combustion in the offgas combustion zone 44 is in a misfire state. At this time, the misfire determination means 86 performs misfire determination based on the comparison result of the temperature comparison means 82, and based on this misfire determination, the misfire stop processing of the system is performed as required (step S37).

On the other hand, the detected temperature value T1 of the combustion zone temperature detection sensor 64 is equal to or higher than the first misfire determination temperature value TS1 (TS1≤T1) (that is, the detected temperature value T1 is lower than the first partial misfire temperature value TB1 and the first misfire temperature value TB1). and the temperature value T3 detected by the cell stack temperature detection sensor 104 is greater than or equal to the third misfire determination temperature value TS3 (TS3≦T3) (that is, the detected temperature value T3 is the third misfire determination temperature value TS1 or more) is lower than the partial misfire temperature value TB3 and equal to or higher than the third misfire determination temperature value TS3), the combustion temperature of the offgas combustion region 44 decreases and the fuel offgas is in a partial misfire state, and the process proceeds from step S35 to step S38. At this time, the partial misfire determination means 84 makes a partial misfire determination based on this determination result, and corrects the amount of fuel gas to increase so as to eliminate the partial misfire state and return to a stable combustion state (step S39). .

Further, in step S33, the temperature value T1 detected by the combustion zone temperature detection sensor 62 is equal to or higher than the first partial misfire determination temperature value TB1 (TB1≤T), and the temperature value T3 detected by the cell stack temperature detection sensor 104 is the third partial misfire. If it is equal to or higher than the determination temperature value TB3 (TB3≤T3), the process proceeds from step S33 to step S40, and the temperature comparison means 82 compares the detected temperature value T2 of the exhaust combustion section temperature detection sensor 102 with the second partial misfire determination temperature value TB2. compare. Then, when the detected temperature value T2 of the exhaust combustion part temperature detection sensor 102 is equal to or lower than the second partial misfire determination temperature value TB2 (T2≤TB2), it is determined that the combustion in the offgas combustion zone 44 is stable, and step S41 is performed. Returning to the flow for confirming the state of occurrence of fuel flow rate hunting (that is, returning to step S3 in the flowchart of FIG. 3).

Further, when the detected temperature value T2 of the exhaust combustion part temperature detection sensor 102 exceeds the second partial misfire determination temperature value TB2 (TB2<T2), the process proceeds from step S40 to step S42 via step S41. The comparison means 82 compares the detected temperature value T2 of the exhaust combustion part temperature detection sensor 102 with the second misfire determination temperature value TS2. Then, when the detected temperature value T2 of the exhaust combustion part temperature detection sensor 102 is higher than the second misfire determination temperature value TS2 (TS2<T2), it is determined that the combustion in the offgas combustion region 44 is in a misfired state, and steps S43 to S36 are performed. , misfire determination is performed, and misfire stop processing of the solid oxide fuel cell system 2 is performed (step S37).

On the other hand, the detected temperature value T2 of the exhaust combustion part temperature detection sensor 104 is equal to or lower than the second misfire determination temperature value TS2 (T2≦TS2) (that is, the detected temperature value T2 is higher than the second partial misfire temperature value TB2 and TS2), the fuel off-gas in the off-gas combustion area 44 is in a partial misfire state, and the process proceeds from step S43 to step S38 to perform a partial misfire determination. Increase correction is performed (step S39).

Although the embodiments of the solid oxide fuel cell system according to the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and modifications are possible without departing from the scope of the present invention. is.

For example, in the above-described second embodiment, the partial misfire determination means 84 determines whether the detected temperature value T1 of the combustion zone temperature detection sensor 62 (combustion zone temperature detection means) is lower than the first partial misfire determination temperature value TB1, or The temperature value T2 detected by the combustion section temperature detection sensor 102 (exhaust combustion section temperature detection means) exceeds the second partial misfire determination temperature value TB2, or the temperature value detected by the cell stack temperature detection sensor 104 (cell stack temperature detection means). When one of the three conditions of whether T3 is lower than the third partial misfire determination temperature value TB3 is satisfied, it is determined that the combustion in the offgas combustion zone 44 is in a partial misfire state. The partial misfire state may be determined when any two conditions are satisfied, or the partial misfire state may be determined when all of these three conditions are satisfied.

Further, for example, in the second embodiment, the misfire determination means 84 determines whether the detected temperature value T1 of the combustion zone temperature detection sensor 62 (combustion zone temperature detection means) is lower than the first misfire determination temperature value TS1, or the exhaust combustion If the temperature value T2 detected by the part temperature detection sensor 102 (exhaust combustion part temperature detection means) exceeds the second misfire determination temperature value TS2, or if the temperature value T3 detected by the cell stack temperature detection sensor 104 (cell stack temperature detection means) If one of the three conditions of being lower than the third misfire determination temperature value TB3 is satisfied, it is determined that the combustion in the offgas combustion zone 44 is in a misfire state. The misfire condition may be determined when one condition is satisfied, or the misfire condition may be determined when all three conditions are satisfied.

Furthermore, in the first embodiment, the combustion zone temperature detection sensor 64 (combustion zone temperature detection means) is used, and in the second embodiment, the combustion zone temperature detection sensor 64 (combustion zone temperature detection means) and the exhaust combustion part temperature detection sensor are used. 102 (exhaust combustion section temperature detection means) and a cell stack temperature detection sensor 104 (cell stack temperature detection means) are used to detect a partial misfire state and a misfire state of combustion in the offgas combustion section 44. The state and misfire state are detected by using any one or any two of the combustion zone temperature detection sensor 64, the exhaust combustion section temperature detection sensor 102 and the cell stack temperature detection sensor 104. be able to.

2 solid oxide fuel cell system 4 reformer 6 cell stack 8 fuel cell 12 fuel electrode 14 air electrode 18 vaporizer 20 fuel gas supply channel 28 fuel gas pump (fuel gas supply means)
32 fuel gas flow rate sensor (fuel gas flow rate measuring means)
36 water pump 40 air blower 44 offgas combustion zone 48 exhaust combustion section 62 temperature detection means 64 combustion zone temperature detection sensor (combustion zone temperature detection means)
66, 66A Controller 72 Flow rate difference calculation means 74 Absolute value moving average calculation means 76 Moving average comparison means 78 Warning operation signal generation means 80 Error stop signal generation means 82 Temperature comparison means 84 Partial misfire determination means 86 Misfire determination means 88 Fuel gas increase Correction setting means 102 Exhaust combustion part temperature detection sensor (exhaust combustion part temperature detection means)
104 cell stack temperature detection sensor (cell stack temperature detection means)

Claims (5)

A reformer for steam reforming the raw fuel gas, a vaporizer for generating steam used for steam reforming, and a reformed fuel gas reformed by the reformer and oxygen in the air. A cell stack for generating electricity by oxidation and reduction, a fuel gas supply means for supplying raw fuel gas to the reformer, an air supply means for supplying air to the cell stack, and the fuel gas supply means. a fuel gas flow rate measuring means for measuring the flow rate of the raw fuel gas supplied by the cell stack; an off-gas combustion section for burning the fuel off-gas and air off-gas after the power generation reaction in the cell stack; the fuel gas supply means; A solid oxide fuel cell system comprising a controller for controlling the operation of the air supply means,
The controller includes a flow rate difference calculation means for calculating a flow rate difference between the fuel flow rate command value and the measured flow rate value of the fuel gas flow rate measurement means, and an absolute value moving average of the flow rate difference calculated by the flow rate difference calculation means. absolute value moving average calculation means; moving average comparison means for comparing the absolute value moving average value S calculated by the absolute value moving average calculation means with the warning determination value K and the error determination value E; and error stop signal generation means for generating an error stop signal for performing error stop processing,
When the absolute value moving average value S exceeds the error determination flow rate value E (E<S), the error stop signal generating means generates the error stop signal, and the error stop processing is performed based on the error stop signal. Further, when the absolute value moving average value S exceeds the warning determination value K and is equal to or less than the error determination value (K<S≤E), the warning driving signal generating means generates the warning driving signal, A solid oxide fuel cell system, wherein the warning operation is performed based on the warning operation signal. 3. The offgas combustion section is an offgas combustion zone from which the fuel offgas and air offgas from the cell stack are led out, and the fuel offgas from the cell stack is combusted in the offgas combustion zone. 2. The solid oxide fuel cell system according to 1. A temperature sensing means is provided for sensing a temperature associated with the cell stack, the temperature sensing means comprising combustion zone temperature sensing means for sensing the temperature of the off-gas combustion zone, and exhaust combustion for burning the discharged fuel off-gas. at least one of exhaust combustion section temperature sensing means for sensing a temperature of the cell stack and cell stack temperature sensing means for sensing a temperature of the cell stack, the controller further comprising: a partial misfire in the offgas combustion zone; includes partial misfire determination means for determining the occurrence of
The partial misfire determination means determines whether the detected temperature T1 of the combustion zone temperature detection means is lower than a first partial misfire determination temperature value TB1 (T1<TB1), and the detection of the exhaust combustion part temperature detection means. Based on whether the temperature T2 exceeds the second partial misfire determination temperature value TB2 (TB2<T2), and whether the detected temperature T3 of the cell stack temperature detecting means is lower than the third partial misfire determination temperature value TB3 (T3 3. The solid oxide fuel cell system according to claim 2, wherein partial misfire is determined based on <TB3). The temperature detection means includes the combustion zone temperature detection means, the exhaust combustion section temperature detection means, and the cell stack temperature detection means, and the partial misfire determination means detects the temperature T1 detected by the combustion zone temperature detection means. lower than the first partial misfire determination temperature value TB1 (T1<TB1), the detection temperature T2 of the exhaust combustion section temperature detection means exceeds the second partial misfire determination temperature value TB2 (TB2<T2), and the cell stack any one of the three conditions that the detected temperature T3 of the temperature detecting means is lower than the third partial misfire determination temperature value TB3 (T3<TB3), or any two conditions, or 4. The solid oxide fuel cell system according to claim 3, wherein determination of partial misfire is made when all three conditions are satisfied. The controller further includes fuel gas increase correction setting means for increasing the supply flow rate of the raw fuel gas supplied to the cell stack, and the partial misfire determination means determines partial misfire during the warning operation. 4. The solid oxide fuel cell system according to claim 3, wherein said fuel gas amount increase correction setting means increases the supply flow rate of the raw fuel gas supplied to said cell stack.

Images