JP2018181455A - Solid oxide fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell system capable of confirming existence of detection error of fuel gas supply flow rate while a cell stack is generating power.SOLUTION: A solid oxide fuel cell system includes a cell stack, an air blower 26, a fuel gas blower 16, fuel gas flow measurement means 17 for measuring fuel gas flow, temperature detection means 54 for detecting the temperature of the cell stack, and a controller 52 performing operation control of the fuel gas blower 16 and the air blower 26. The controller 52 includes fuel utilization rate setting means 64 for setting utilization rate of fuel gas, air utilization rate setting means 66 for setting utilization rate of air consumed in power generation of the cell stack, and flow error determination means 68 for determining existence of detection error of the fuel gas flow measurement means 17 by the fuel utilization rate and the temperature of the cell stack.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a solid oxide fuel cell system that generates electric power by oxidation and reduction of a reformed fuel gas and an oxidant gas obtained by reforming a fuel gas.

  As a fuel cell system, a solid oxide fuel cell (SOFC) provided with a cell stack in which solid oxide fuel cells are stacked is put to practical use (see, for example, Patent Document 1). In this solid oxide fuel cell, a fuel electrode for oxidizing a reformed fuel gas (also referred to as “fuel gas”) is disposed on one side of a solid electrolyte conducting oxygen ions, and an oxidant gas (on the other side). For example, an oxygen electrode for reducing oxygen in the air is provided, and generally, yttria-doped zirconia is used as a material of a solid electrolyte.

  In the solid oxide cell stack, power generation is performed at high temperature of 700 to 1000 ° C. by electrochemical reaction of hydrogen in the fuel gas, carbon monoxide, hydrocarbons and oxygen in the oxidant gas. Solid oxide fuel cell systems have been developed as promising power generation technologies because they can generate power with particularly high power generation efficiency compared to other fuel cell systems and gas engines.

  The solid oxide fuel cell system has a high operating temperature of the cell stack, so fuel gas not consumed by the cell stack (does not contribute to power generation), in other words reformed fuel gas flowing out from the fuel electrode side of the cell stack Gas) and an oxidant gas (air) flowing out from the oxygen electrode side of the cell stack are burned in the combustion space on the discharge side of the cell stack, and the heat of combustion obtained by this combustion vaporizes the reforming water And a reformer for steam reforming the fuel gas are configured to be heated.

  In this known solid oxide fuel cell system, a vaporizer and a reformer are disposed above the combustion space. The vaporization reaction carried out by the vaporizer and the reforming reaction carried out by the reformer are both endothermic reactions, therefore the heat generated by the combustion of the combustion space is taken away by these endothermic reactions and after the heat is taken away The combustion exhaust gas is discharged to the outside.

  The proportion of fuel gas consumed by the cell stack of such a solid oxide fuel cell system (ie, fuel gas that contributes to power generation) is indicated by the fuel utilization rate. To be precise, the fuel utilization rate refers to the ratio of the consumption rate of fuel valence electrons by power generation to the supply rate of fuel gas valence electrons proportional to the flow rate of the fuel gas.

Also, the power generation efficiency of the solid oxide fuel system is generally determined by the following equation (1),
Power generation efficiency = coefficient × cell stack voltage × fuel utilization factor × auxiliary device efficiency × inverter efficiency. Here, the coefficient is a coefficient determined by the number of valence electrons and the amount of heat of the fuel gas, and auxiliary equipment efficiency is the DC power output from the cell stack, various blowers operated by this DC power, etc. It is the ratio to the net DC output after subtracting the DC loss consumed by the auxiliaries to drive the inside of the fuel cell system, and the inverter efficiency means the conversion from the net DC output to the AC output. It is conversion efficiency.

  As understood from the above-mentioned equation (1) of the power generation efficiency, it can be seen that the power generation efficiency becomes higher as the fuel utilization rate is higher, if the output voltage of the cell stack (fuel cell) is the same. However, when the fuel utilization rate is increased, the excess fuel gas not used for power generation in the cell stack is reduced, the heat of combustion in the combustion space is reduced, and the temperature of the cell stack is lowered, thereby The internal resistance of the stack is increased to cause a decrease in the generated voltage of the cell stack. Therefore, the power generation efficiency of the cell stack reaches a plateau even if the fuel utilization rate is simply increased. In addition, if the fuel utilization rate is extremely high, combustion in the combustion space can not be maintained partially normal, which may cause a significant temperature drop. In this case, a large change occurs in the vaporization state in the vaporizer, S / C (water vapor / carbon ratio) also becomes unstable, and as a result, the solid oxide fuel cell system enters an immediate failure mode. The possibility is high.

  On the other hand, as well as the fuel utilization factor, there is an oxidant utilization factor (air utilization factor when the oxidizing gas is air) as an important control parameter when operating the solid oxide fuel cell system. The air utilization rate is the ratio of oxygen used for power generation to the total amount of oxygen supplied to the cell stack. The control range of the flow rate of the oxidant gas (for example, air) and the air utilization factor are set in order to keep the operating temperature of the cell stack within the appropriate range. That is, if the flow rate of the oxidant gas is small, the cooling action by the oxidant gas is reduced and the temperature of the cell stack is raised, whereby the output voltage of the cell stack is increased, which is advantageous for obtaining high power generation efficiency. However, considering the heat resistance of the cell stack, it can not be made lower than a predetermined flow rate. Also, if it is desired to cool the cell stack to offset the temperature rise due to the aged deterioration of the cell stack, the flow rate of the oxidant gas set initially is increased more than the supply flow rate of the oxidant gas (that is, the air utilization rate is decreased). The cell stack temperature may be kept within an appropriate range.

  In such a solid oxide fuel cell system, the fuel utilization factor of the fuel gas and the oxidant utilization factor of the oxidant gas (in the case of air, the air utilization factor) are taken into consideration during the power generation while taking into consideration the above. The supply of the fuel gas and the oxidant gas is controlled so as to be set and set to the fuel utilization factor and the oxidant utilization factor.

  One of the representative methods of controlling the supply of fuel gas and oxidant gas is a method based on the current value (output value) of the power generation output of the cell stack, in which the current value of the power generation output is determined, The fuel utilization factor of the fuel gas and the oxidant utilization factor of the oxidant gas (for example, air) are determined so as to obtain the current value, and the flow rate and oxidation of the fuel gas are such that the fuel utilization factor and the oxidant utilization factor are obtained. The flow rate of the material gas is calculated, and the fuel gas blower and the oxidant gas blower (air blower) are controlled so as to achieve the calculated flow rate. The operation by such a control method becomes a utilization factor priority operation controlled based on the fuel utilization factor and the oxidant utilization factor, the temperature of the cell stack (operating temperature) is the change of the outside air temperature, the detection of the fuel gas flow rate measuring means It fluctuates due to an error, and further, an increase in Joule heat due to aging of the cell stack.

  Another one of the representative methods is a method based on the temperature of the cell stack or its vicinity (so-called operating temperature), in which the temperature of the cell stack (operating temperature) and the fuel utilization rate of the fuel gas, for example Is determined, and the oxidant utilization factor (eg, air utilization factor) of the oxidant gas (eg, air) is variably set to achieve this temperature, and the fuel is brought to the target temperature by setting the cell stack temperature to the target temperature. The gas blower and the oxidant gas blower (air blower) are controlled. The operation by such a control method is a temperature priority operation controlled based on the temperature of the cell stack. For example, in order to offset the temperature rise due to the aging of the cell stack, the supply flow rate of the oxidant gas (eg, air) Control to increase and fall within the desired temperature range is this method of operation.

JP, 2006-19084, A

  In the operation of this solid oxide fuel cell system, the fuel utilization factor of the fuel gas is the ratio of the consumption speed of the fuel valence electrons by the power generation to the supply speed of the fuel gas valence electrons, which is on the fuel cell system The current value drawn from the cell stack and the supply flow rate of the fuel gas recognized by the fuel cell system are determined, and the supply flow rate of the fuel gas is measured by the fuel gas flow measurement means (for example, The measurement accuracy of the fuel gas flow rate measuring sensor is a problem, and the supply flow rate of the fuel gas may not be the intended flow rate due to the detection error of the fuel gas flow rate measuring means. Although this detection error, that is, the deviation from the actual supply flow rate can be measured by a separate flow meter installed outside the fuel cell system, a flow measurement sensor (fuel gas flow measurement sensor that measures the flow) As for the oxidant gas flow rate measurement sensor, generally, about ± 3% of the measured value is often used, and in the fuel cell system, this flow rate measurement sensor (fuel gas flow rate measurement sensor, oxidant gas) It is difficult to grasp the flow rate error of the flow rate measurement sensor).

  To explain this specifically, there is a detection error in the measurement value of the fuel gas flow measurement sensor used in the solid oxide fuel cell system, and the fuel gas flow measurement sensor has a value smaller than the actual supply flow value. If it is shown (in other words, there is a detection error on the negative side), more fuel gas is supplied than the supply flow rate recognized by this fuel cell system (ie, the measurement value of the fuel gas flow measurement sensor). There is a control error in the direction of flowing more fuel gas. For example, even if the fuel cell system sets the upper limit fuel utilization rate to, for example, 80.5%, the control error in the direction in which more fuel gas flows due to the detection error on the negative side of the fuel gas flow measurement sensor described above Due to this control error, the actual fuel utilization rate may be, for example, about 79%, and the power generation efficiency of the fuel cell system may not reach the intended target level.

  The object of the present invention is to provide a solid oxide fuel cell system capable of confirming the presence or absence of a detection error of a fuel gas supply flow rate which becomes a problem particularly when setting a high fuel utilization rate during power generation of a cell stack. It is to be.

The solid oxide fuel cell system according to claim 1 of the present invention comprises a cell stack formed by stacking solid oxide fuel cells that generate electricity by reacting a fuel gas and an oxidant gas, and an oxidant gas. The oxidant gas supply means for feeding to the oxygen electrode side of the cell stack, the fuel gas supply means for feeding fuel gas to the fuel electrode side of the cell stack, and the cell stack from the fuel gas supply means Fuel gas flow rate measuring means for measuring the flow rate of the fuel gas supplied to the fuel electrode side of the fuel cell, temperature detection means for detecting the temperature of the cell stack, the fuel gas supply means, and the oxidant gas A solid oxide fuel cell system comprising: a controller for controlling operation of the supply means;
The controller sets fuel utilization factor setting means for setting the utilization factor of the fuel gas consumed in the power generation in the cell stack, and sets the utilization factor of the oxidant gas consumed in the power generation in the cell stack An oxidant utilization factor setting unit for determining the flow rate error of the fuel gas flow rate measuring unit;
In the rated power generation state of the cell stack, the controller performs the utilization value priority operation giving priority to the fuel utilization factor and the oxidant utilization factor, and in the utilization value priority operation, the fuel utilization factor setting unit is the first While the fuel utilization rate is set, the oxidant utilization rate setting means sets the first oxidant utilization rate, and then the controller performs the utilization rate increase operation in which the fuel utilization rate is increased, and the utilization rate rises. In operation, the oxidant utilization factor setting means maintains the first oxidant utilization factor, and the fuel utilization factor setting means sets a second fuel utilization factor higher than the first fuel utilization factor. The temperature detection means detects a first temperature state of the cell stack in the utilization factor priority operation and a second temperature state of the cell stack in the utilization factor rising operation, and the flow rate error The means determines the presence or absence of a detection error of the fuel gas flow rate measuring means based on the first detected temperature in the first temperature state and the second detected temperature in the second temperature state of the cell stack. .

  Further, in the solid oxide fuel cell system according to claim 2 of the present invention, the flow rate error determination means is a calculation temperature difference between the first detection temperature and the second detection temperature of the temperature detection means and a reference temperature The fuel gas flow rate measuring unit determines that there is a plus side error when the calculated temperature difference is smaller than the reference temperature difference, and the fuel utilization setting unit determines the second fuel utilization ratio. It is characterized in that a third fuel utilization factor higher than that is set.

  Further, in the solid oxide fuel cell system according to claim 3 of the present invention, when the flow rate error determining means determines that the fuel gas flow rate measuring means has a plus side error, the controller determines that the second side has a positive side error. The increase utilization factor calculation means for calculating the increase utilization factor to be further raised from the fuel utilization factor, the increase utilization factor calculation means is configured to increase the increase factor based on a comparison temperature difference between the calculation temperature difference and the reference temperature difference. A utilization factor is calculated, and the fuel utilization factor setting means sets the third fuel utilization factor in which the rising utilization factor is added to the second fuel utilization factor.

The solid oxide fuel cell system according to claim 4 of the present invention is a cell stack in which solid oxide fuel cells that generate electricity by reacting a fuel gas and an oxidant gas are stacked, and an oxidant From the fuel gas supply means, an oxidant gas supply means for supplying a gas to the oxygen electrode side of the cell stack, a fuel gas supply means for supplying a fuel gas to the fuel electrode side of the cell stack, and Fuel gas flow rate measuring means for measuring the flow rate of fuel gas supplied to the fuel electrode side of the cell stack, and oxidant gas supplied from the oxidant gas supply means to the oxygen electrode side of the cell stack Oxidant gas flow rate measuring means for measuring the flow rate, temperature detection means for detecting the temperature of the cell stack, operation control of the fuel gas supply means and the oxidant gas supply means And controller because, a solid oxide fuel cell system equipped with,
The controller sets fuel utilization factor setting means for setting the utilization factor of the fuel gas consumed in the power generation in the cell stack, and sets the utilization factor of the oxidant gas consumed in the power generation in the cell stack An oxidant utilization factor setting unit for determining the flow rate error of the fuel gas flow rate measuring unit;
In the rated power generation state of the cell stack, the controller performs the utilization value priority operation giving priority to the fuel utilization factor and the oxidant utilization factor, and in the utilization value priority operation, the fuel utilization factor setting unit is the first While setting the fuel utilization factor, the oxidant utilization factor setting means sets the first oxidant utilization factor, and then the controller performs a temperature priority operation so that the temperature detected by the temperature sensing means becomes the target temperature. In the temperature priority operation, the fuel utilization setting means sets the second fuel utilization higher than the first fuel utilization, and the oxidant gas supply means detects the temperature detected by the temperature detection means. Is controlled to become the target temperature, and then the flow rate error determination means measures the fuel gas flow rate based on the second oxidant utilization factor in the temperature priority operation And judging the presence or absence of detection error.

  In the solid oxide fuel cell system according to claim 5 of the present invention, the controller includes an oxidant utilization factor computing means for computing the oxidant utilization factor, and the oxidant utilization factor computing means The second oxidant utilization rate is calculated based on the supply flow rate of the oxidant gas in the temperature priority operation, and the flow rate error determination means uses the second oxidant utilization rate and the reference oxidant in the temperature priority operation. The fuel gas flow rate measuring means determines that there is a plus-side error when the second oxidant utilization rate is smaller than the reference oxidant utilization rate, and the fuel utilization rate setting means A third fuel utilization rate higher than the second fuel utilization rate is set.

  Further, in the solid oxide fuel cell system according to claim 6 of the present invention, the controller further raises the second fuel utilization rate when the flow rate error determination means determines that there is a plus side error. The rising utilization factor computing means includes a rising utilization factor computing means for computing the rising utilization factor, and the rising utilization factor computing means compares the second oxidizing material utilization factor with the reference oxidizing material utilization factor. A utilization factor is calculated, and the fuel utilization factor setting means is set to the third fuel utilization factor obtained by adding the rising utilization factor to the second fuel utilization factor.

The solid oxide fuel cell system according to claim 7 of the present invention is a cell stack in which solid oxide fuel cells that generate electricity by reacting a fuel gas and an oxidant gas are stacked, and an oxidant From the fuel gas supply means, an oxidant gas supply means for supplying a gas to the oxygen electrode side of the cell stack, a fuel gas supply means for supplying a fuel gas to the fuel electrode side of the cell stack, and Fuel gas flow rate measuring means for measuring the flow rate of fuel gas supplied to the fuel electrode side of the cell stack, and oxidant gas supplied from the oxidant gas supply means to the oxygen electrode side of the cell stack Oxidant gas flow rate measuring means for measuring the flow rate, temperature detection means for detecting the temperature of the cell stack, operation control of the fuel gas supply means and the oxidant gas supply means And controller because, a solid oxide fuel cell system equipped with,
The controller sets fuel utilization factor setting means for setting the utilization factor of the fuel gas consumed in the power generation in the cell stack, and sets the utilization factor of the oxidant gas consumed in the power generation in the cell stack An oxidant utilization factor setting unit for determining the flow rate error of the fuel gas flow rate measuring unit;
In the rated power generation state of the cell stack, the controller performs the utilization value priority operation giving priority to the fuel utilization factor and the oxidant utilization factor, and in the utilization value priority operation, the fuel utilization factor setting unit is the first While setting the fuel utilization factor, the oxidant utilization factor setting means sets the first oxidant utilization factor, and then the controller gives priority to the first temperature so that the temperature detected by the temperature detector becomes the target temperature. In operation, in the first temperature priority operation, the fuel utilization setting means sets the first fuel utilization, and the oxidant gas supply means detects that the temperature detected by the temperature detection means is the target temperature After that, the controller performs the second temperature priority operation, and in the second temperature priority operation, the fuel utilization factor setting unit performs the first fuel priority operation. The second fuel utilization rate higher than the usage rate is set, and the oxidant gas supply means is controlled so that the temperature detected by the temperature detection means becomes the target temperature, and the flow rate error determination means It is characterized in that the presence or absence of a detection error of the fuel gas flow rate measuring means is determined based on the second oxidant utilization rate in the first temperature priority operation and the third oxidant utilization rate in the second temperature priority operation.

  In the solid oxide fuel cell system according to claim 8 of the present invention, the controller includes an oxidant utilization factor computing means for computing the oxidant utilization factor, and the oxidant utilization factor computing means The second oxidant utilization rate is calculated based on the supply flow rate of the oxidant gas in the first temperature priority operation, and the third oxidant based on the supply flow rate of the oxidant gas in the second temperature priority operation The utilization rate is calculated, and the flow rate error determination means compares the calculated oxidized material utilization difference between the second oxidized material utilization rate and the third oxidized material utilization rate with the reference oxidized material utilization rate difference, and calculates the calculated oxidation When the material utilization difference is smaller than the reference oxidant utilization difference, the fuel gas flow rate measuring means determines that there is a plus error, and the fuel utilization setting means is higher than the second fuel utilization. Set the 3rd fuel utilization rate Characterized in that it.

  Furthermore, in the solid oxide fuel cell system according to claim 9 of the present invention, when the flow rate error determining means determines that the fuel gas flow rate measuring means has a plus side error, the controller determines that the second side has a positive side error. The rising utilization factor computing means includes a rising utilization factor computing means for computing the rising utilization factor to be further elevated from the fuel utilization factor, wherein the rising utilization factor computing means compares the calculated oxidizing material utilization difference with the reference oxidizing material utilization difference. The rising utilization rate is calculated based on the material utilization difference, and the fuel utilization setting means sets the third fuel utilization rate obtained by adding the rising utilization rate to the second fuel utilization rate. Do.

  According to the solid oxide fuel cell system according to claim 1 of the present invention, a controller for controlling the fuel cell system comprises: fuel utilization factor setting means for setting the utilization factor of the fuel gas; Oxidizer utilization factor setting means (for example, air utilization factor setting means) for setting the utilization factor of gas (for example, air), and flow rate error judgment means for judging presence or absence of detection error of fuel gas flow measurement means In the rated power generation state of the cell stack, the utilization value priority operation giving priority to the fuel utilization factor and the oxidant utilization factor is performed. In this utilization factor priority operation, the first fuel utilization factor (for example, 78 % And the first oxidant utilization rate (for example, 38%) are set, and then the utilization factor increasing operation for raising the fuel utilization factor is performed. In this utilization factor raising operation, the first oxidant utilization factor ( 38 ) Is the second fuel utilization rate in a state of being maintained (e.g., 80%) is set. Thus, when switching the operating state, by keeping the oxidant utilization factor (air utilization factor) constant, it is possible to focus on the temperature state of the cell stack and catch its change state. The change can be used to check whether there is a detection error of the fuel gas flow rate measuring means.

  For example, when the fuel gas flow rate measuring means indicates a value smaller than the actual supply flow rate value and there is an error on the negative side of the fuel gas flow rate measuring means, control of flowing the fuel gas more than the actual measured value An error occurs, and the temperature of the cell stack rises as compared with the case where there is no control error, and the degree of the measurement error can be known by observing the degree of this temperature state.

  Further, according to the solid oxide fuel cell system according to claim 2 of the present invention, the calculated temperature difference between the first detection temperature and the second detection temperature of the temperature detection means is compared with the reference temperature difference, and this calculated temperature If the difference is smaller than the reference temperature difference, the flow rate error determining means may expand the detection error on the plus side to the fuel gas flow rate measuring means in the process of transitioning from the first fuel utilization to the second fuel utilization. It will be judged. Then, when the detection error on the positive side is expanded, the fuel gas is supplied more than the measured flow rate value, and hence the third fuel utilization rate higher than the second fuel utilization rate as the fuel utilization rate of the fuel gas The power generation efficiency of the fuel cell system can be enhanced by setting the third fuel utilization rate.

  Further, according to the solid oxide fuel cell system according to claim 3 of the present invention, the rising utilization factor calculation means calculates the rising utilization factor based on the comparison temperature difference between the above-mentioned calculated temperature difference and the reference temperature difference. Since the fuel utilization factor setting means sets the third fuel utilization factor, which is obtained by adding the rising utilization factor to the second fuel utilization factor, as the fuel utilization factor, the third fuel utilization factor corresponds to that of the fuel gas flow rate measuring means. It can be made a value according to the degree of detection error.

  Further, according to the solid oxide fuel cell system according to claim 4 of the present invention, a controller for controlling the fuel cell system comprises: fuel utilization factor setting means for setting the utilization factor of the fuel gas; An oxidant utilization factor setting unit (for example, an air utilization factor setting unit) for setting the utilization factor of an oxidant gas (for example, air), and a flow rate error for judging the presence or absence of a detection error of the fuel gas flow rate measuring unit In the rated power generation state of the cell stack including the determination means, the utilization value priority operation giving priority to the fuel utilization factor and the oxidant utilization factor (for example, air utilization factor) is performed, and in this utilization factor priority operation, (1) A fuel utilization rate (for example, 78%) and a first oxidant utilization rate (for example, 38%) are set, and then a temperature priority operation is performed to maintain the cell stack temperature at the target temperature. In addition, a second fuel utilization factor (for example, 80%) higher than the first fuel utilization factor (for example, 78%) is set, and the detection temperature of the temperature detection means is a target temperature (for example, 743.degree. C.) The oxidant gas supply means is controlled so that When switching the operation in this way, attention is paid to the oxidant utilization factor in the temperature priority operation, and the second oxidant utilization factor in the temperature priority operation is captured to utilize the second air utilization factor as a fuel gas. It is possible to check the presence or absence of a detection error of the flow rate measuring means.

  For example, if the fuel gas flow rate measuring means indicates a value smaller than the actual supply flow rate value and there is a detection error on the negative side of the measured flow rate of the fuel gas, a control error may be caused to flow more fuel gas. As a result, the temperature of the cell stack tends to rise, and the amount of oxidant gas supplied increases to maintain the target temperature (this means that the availability of oxidant decreases), and this oxidant The degree of measurement error can be known by looking at the decrease in utilization rate.

  Further, according to the solid oxide fuel cell system according to claim 5 of the present invention, the oxidant utilization factor computing means computes the second oxidant utilization factor based on the flow rate of oxidant gas in the temperature priority operation. Then, the second oxidant utilization factor (second air utilization factor) and the reference oxidant utilization factor (reference air material utilization factor) in this temperature priority operation are compared, and the second oxidant utilization factor and the reference oxidant are compared. There is no detection error when the utilization factor is equal, but if the second oxidant utilization factor is smaller than the reference oxidant utilization factor, it is assumed that the fuel gas is supplied more than the measured flow rate, and the flow rate error judging means It is determined that the gas flow rate measurement means has a plus side error, and based on this determination, a third fuel utilization factor higher than the second fuel utilization factor is set.

  Further, according to the solid oxide fuel cell system according to claim 6 of the present invention, the rising utilization factor calculation means comprises the above-mentioned second oxidant utilization factor (for example, second air utilization factor) and reference oxidant The rising utilization rate is calculated based on the difference in the utilization rate of the oxidant with the utilization rate (for example, the reference air utilization rate), and the fuel utilization rate setting means adds the rising utilization rate to the second fuel utilization rate. Since the utilization factor is set as the fuel utilization factor, the third fuel utilization factor can also be set to a value according to the degree of detection error of the fuel gas flow rate measuring means.

  Further, according to the solid oxide fuel cell system according to claim 7 of the present invention, a controller for controlling the fuel cell system comprises: fuel utilization factor setting means for setting the utilization factor of the fuel gas; An oxidant utilization factor setting unit (for example, an air utilization factor setting unit) for setting the utilization factor of an oxidant gas (for example, air), and a flow rate error for judging the presence or absence of a detection error of the fuel gas flow rate measuring unit In the rated power generation state of the cell stack including the judging means, the utilization value priority operation giving priority to the fuel utilization factor and the oxidant utilization factor is performed, and in this utilization factor priority operation, the first fuel utilization factor (for example, 78%) and the first oxidant utilization rate (for example, 38%) are set, and then the first temperature priority operation is performed so that the temperature of the cell stack becomes the target temperature. In this first temperature priority operation, The oxidant gas supply means is controlled so that the temperature of the cell stack becomes the target temperature (for example, 743 ° C.) while maintaining the fuel utilization rate (for example, 78%), and thereafter, in the second temperature priority operation And a second fuel utilization (for example, 80%) higher than the first fuel utilization (for example, 78%) is set, and the temperature of the cell stack becomes the target temperature (for example, 743.degree. C.) An oxidant gas supply means is controlled. When switching the operation in this manner, attention is focused on the fluctuation of the oxidant utilization factor between the second oxidant utilization factor in the first temperature priority operation and the third oxidant utilization factor in the second temperature priority operation, and this oxidant utilization By detecting the change state of the rate, it is possible to check whether there is a detection error of the fuel gas flow rate measuring means.

  Further, according to the solid oxide fuel cell system according to claim 8 of the present invention, the oxidant utilization factor computing means is configured to use the second oxidant utilization factor based on the flow rate of oxidant gas in the first temperature priority operation. And the third oxidation utilization rate is calculated based on the flow rate of the oxidant gas in the second temperature priority operation. Then, the flow rate error determination means compares the calculated oxidizing material utilization difference between the second oxidizing material utilization factor and the third oxidizing material utilization factor with the reference oxidizing material utilization difference, and the calculated oxidizing material utilization factor difference is the reference oxidation. If the fuel gas is supplied more than the measured flow rate value when the difference is smaller than the material utilization rate difference, the flow rate error determining means determines that the fuel gas flow rate measuring means has a plus error, and the second fuel utilization rate is determined. A high third fuel utilization is also set.

  Furthermore, according to the solid oxide fuel cell system according to claim 9 of the present invention, the increased utilization factor calculation means compares the above-mentioned difference in the utilization factor of the calculated oxidant with the difference in utilization factor of the reference oxidant. The rising utilization rate is calculated based on the rate difference, and the fuel utilization rate setting means sets the third fuel utilization rate obtained by adding the rising utilization rate to the second fuel utilization rate, and the third fuel utilization rate is And a value corresponding to the degree of detection error of the fuel gas flow rate measuring means.

1 is a simplified cross-sectional view showing a first embodiment of a solid oxide fuel cell system according to the present invention. FIG. 2 is a block diagram showing a control system of the solid oxide fuel cell system of FIG. 1; The figure which shows the relationship between the electric power output of a cell stack, and a fuel utilization factor when there is a detection error in fuel-gas flow measurement means. The flowchart which shows the flow of the flow volume error check driving | operation by the control system of FIG. FIG. 5 is a block diagram showing a control system in a second embodiment of the solid oxide fuel cell system according to the present invention. The flowchart which shows the flow of the flow volume error check operation by the control system of FIG. FIG. 7 is a block diagram showing a control system in a third embodiment of the solid oxide fuel cell system according to the present invention. FIG. 8 is a flowchart showing the flow of a flow rate error check operation by the control system of FIG. 7;

  Hereinafter, embodiments of a solid oxide fuel cell system according to the present invention will be described with reference to the attached drawings. First, a solid oxide fuel cell system according to a first embodiment will be described with reference to FIGS. 1 to 4.

  In FIG. 1, the illustrated solid oxide fuel cell system 2 is steam-reformed by a reformer 4 for reforming fuel gas (eg, natural gas, city gas, etc.) and the reformer 4. And a cell stack 6 for generating electricity by oxidation and reduction of air as a fuel gas (also referred to as "reformed fuel gas") and an oxidant gas.

  The cell stack 6 is configured by stacking a plurality of fuel cells (not shown), and each fuel cell includes a solid electrolyte conducting oxygen ions, a fuel electrode provided on one side of the solid electrolyte, and a solid An oxygen electrode is provided on the other side of the electrolyte, and zirconia doped with yttria, for example, is used as a solid electrolyte.

  The introduction side of the fuel electrode side 8 of the cell stack 6 is connected to a reformer 4 via a reformed fuel gas feed line 10, and the reformer 4 feeds fuel gas via a fuel gas feed line 12. It is connected to a fuel gas supply source 14 (for example, a buried pipe, a fuel gas tank, etc.) for supply. The fuel gas supply line 12 is provided with a fuel gas blower 16 for supplying a fuel gas, and a fuel gas flow rate measuring means 17 (for example, a fuel gas flow rate measuring sensor) is provided downstream of the fuel gas blower 16. It is done. The fuel gas blower 16 supplies the fuel gas from the fuel gas supply source 14 to the reformer 4, and when the rotation speed increases (or decreases), the supply flow rate of the fuel gas supplied through the fuel gas supply line 12 increases ( Alternatively, the fuel gas flow rate measuring means 17 measures the supply flow rate of the fuel gas supplied through the fuel gas supply line 12. The fuel gas supply source 14, the fuel gas supply line 12, and the fuel gas blower 16 constitute a fuel gas supply means for supplying a fuel gas.

  In addition, the introduction side of the oxygen electrode side 18 of the cell stack 6 is an air preheater 22 for preheating air as an oxidant gas through an air delivery line 20 (functioning as an oxidant gas delivery line). The air preheater 22 is connected to the oxidant blower as an oxidant blower via an air supply line 24 (functions as an oxidant supply line), and is connected to the oxidant gas residual heater. An air flow rate measuring means 27 (functioning as an oxidant gas flow rate measuring means) for measuring the flow rate of air as an oxidant gas is disposed in the line 20, and the air flow rate measurement means 27 is an air supply line 20. Measure the supply flow rate of air supplied through the As the rotation speed of the air blower 26 increases (or decreases), the amount of air supplied through the air supply line 24 increases (or decreases), and the air supply line 24 and the air blower 26 function as oxidant gas. The air supply means (which functions as an oxidant gas supply means) for supplying air is configured.

  A combustion space 28 is provided on the outflow side of the fuel electrode side 8 and the oxygen electrode side 18 of the cell stack 6, and the fuel gas (also referred to as “reaction fuel gas”) flowing out from the fuel electrode side 8 The discharged air (oxidizer gas) is supplied to the combustion space 28 and burned. The combustion space 28 is connected to an air preheater 22 via a combustion exhaust gas line 30, and a combustion exhaust gas discharge line 32 is connected to the air preheater 22.

  In this embodiment, the cell stack 6, the reformer 4 and the air regenerator 22 are accommodated in the battery housing 34. A heat insulating material is disposed on the inner surface or outer surface of the battery housing 34 or both surfaces thereof, and defines a high temperature space 36 in which the battery housing 34 is kept at a high temperature. The cell stack 6, the reformer 4 and the air regenerator 22 is accommodated in the high temperature space 36 and kept in a high temperature state.

  In the solid oxide fuel cell system 2, a water supply source 40 (for example, a pure water tank etc.) is connected to the reformer 4 via a water supply line 38, and the water pump 42 is connected to the water supply line 38. It is arranged. When the rotation speed of the water pump 42 is increased (or decreased), the supply amount of reforming water supplied through the water supply line 38 is increased (or decreased), and the water supply line 38 and the water pump 42 Water supply means for supplying water. In this embodiment, water from the water supply source 40 is supplied, but instead of such a configuration, the water vapor contained in the combustion exhaust gas is condensed and recovered, and the recovered condensed water is reformed It can also be configured to be supplied to the vessel 4 and used as reforming water.

  The operation of the solid oxide fuel cell system 2 is performed as follows. The fuel gas from the fuel gas supply source 14 is supplied to the reformer 4 through the fuel gas supply line 12, and the reforming water from the water supply source 40 is supplied to the reformer 4 through the water supply line 38. In the reformer 4, the fuel gas is steam-reformed with water (steam), and the steam-reformed fuel gas (reformed fuel gas) passes through the reformed fuel gas feed line 10 on the fuel electrode side of the cell stack 6. It is sent to eight. Also, the air from the air blower 26 is supplied to the air preheater 22 through the air supply line 24, and after being heat-exchanged with the combustion exhaust gas in the air preheater 22, the air supply line is supplied. 20 is fed to the oxygen electrode side 18 of the cell stack 6.

  The fuel electrode side 8 of the cell stack 6 oxidizes the reformed fuel gas, and the oxygen electrode side 18 reduces oxygen in the air, and the electrochemical reaction is caused by the oxidation of the fuel electrode side 8 and the reduction of the oxygen electrode side 18 Power is generated. The reaction fuel gas from the fuel electrode side 8 and the air from the oxygen electrode side 18 flow out to the combustion space 28, and the oxygen in the air is used to burn the reaction fuel gas (including the excess fuel gas). The heat of combustion heats the cell stack 6, the reformer 4 and the air preheater 22.

  The combustion exhaust gas from the combustion space 28 is fed to the air preheater 22 through the combustion exhaust gas line 30, and is utilized for heat exchange with the air from the air blower 26 in the air preheater 22, and the combustion exhaust gas discharge line 32. Discharged to the outside through the

  In addition, a hot water storage apparatus provided with a hot water storage tank for storing the waste heat of combustion exhaust gas as hot water is provided, and heat exchange is performed with the combustion exhaust gas flowing through the combustion exhaust gas discharge line 32 in relation to this hot water storage apparatus. A heat exchanger may be disposed in the combustion exhaust gas discharge line 32, and the hot water heated by heat exchange in the heat exchanger may be stored in the hot water storage tank of the hot water storage device.

  The solid oxide fuel cell system 2 is controlled by a control system shown in FIG. Referring to FIG. 2 together with FIG. 1, the solid oxide fuel cell system 2 includes a controller 52 for controlling the operation of the solid oxide fuel cell system 2. The controller 52 is composed of, for example, a microprocessor. Measurement signals from the fuel gas flow rate measuring hand 17 (fuel gas flow rate measuring sensor) and the air flow rate measuring means 27 (air flow rate measuring sensor) as oxidant gas flow rate measuring means are supplied to the controller 52.

  Further, a temperature detection means 54 (temperature sensor) for detecting a temperature of the cell stack 6 or its vicinity (so-called operating temperature of the cell stack 6) is provided, and a detection signal from the temperature detection means 54 is supplied to the controller 52. It is sent. Furthermore, an inverter 56 for converting DC power to AC power is provided on a power generation output line (not shown) of cell stack 6, and the power generated by cell stack 6 is converted to AC power by this inverter 56. And then delivered to a power load (not shown). A power generation output detection means 58 for detecting the power generation output of the cell stack 6 is provided in association with the inverter 56, and a detection signal from the power generation output detection means 56 is also sent to the controller 52.

  The controller 52 includes a control means 60, a temperature difference calculation means 62, a fuel utilization factor setting means 64, an air utilization factor setting means 66 (functioning as an oxidant utilization factor setting means), a flow rate error judging means 68, a timer means 70 and Memory means 72 are included. The control means 60 controls the operation of the fuel gas blower 16, the air blower 26 (oxidizer gas blower), the water pump 42 and the inverter 56 as required. Further, the temperature difference calculating means 62 calculates the temperature difference between the first temperature state when operating with the first fuel utilization rate described later and the second temperature state when operating with the second fuel utilization rate. The fuel utilization setting means 64 sets the fuel utilization as described later, and the air utilization setting means 66 (functions as an oxidant utilization setting means) sets the air utilization (oxidant utilization) as described later. The flow rate error determining means 68 determines that there is a detection error in the fuel gas flow rate measuring means 54 as described later.

  Further, the timer means 70 sets a first setting time (for example, set to about 10 to 30 minutes) until the utilization factor priority operation to be described later becomes stable and a second setting time until the utilization factor rising operation becomes stable. (For example, it is set to about 1 to 3 hours) etc. Furthermore, the memory means 72 includes a power generation output-Uf map indicating the relationship between the power generation output of the cell stack 6 and the fuel utilization rate (also expressed as "Uf"), the power generation output of the cell stack 6 and the air utilization rate ("Ua" Power generation output-Ua map showing the relationship with “1”, the first setting time, the second setting time, and the second fuel utilization factor and fuel gas flow rate measuring means 54 set in the utilization factor rising operation have a detection error The third fuel utilization factor and the like which are set when the judgment is made are registered.

  In the solid oxide fuel cell system 2, the flow rate error of the fuel gas flow rate measuring means 17 is checked as follows. Mainly referring to FIGS. 2 and 4, this flow rate error check is performed in a stable operating state where the power generation output of the cell stack 6 is stable. When the power generation output of the cell stack 6 reaches the rated output (for example, 700 W), the process proceeds from step S1 to step S2, and the utilization factor priority operation with constant fuel utilization factor (Uf) and air utilization factor (Ua) is performed. . That is, when the detected output of the power generation output detection means 58 becomes the rated output, the fuel utilization factor setting means 64 determines the fuel utilization rate corresponding to the rated output based on the power generation output-Uf map registered in the memory means 72, The air utilization factor setting means 66 is set to the fuel utilization factor (for example, 78%), the air utilization factor corresponding to the rated output based on the power generation output-Ua map registered in the memory means 72, that is, the first air utilization factor A utilization factor priority operation is performed in which (for example, 38%) is set and the first fuel utilization factor and the first air utilization factor are held constant, and in such utilization factor priority operation, the control means 60 The fuel gas blower 16 is controlled to have the first fuel utilization rate, and the air blower 26 is controlled to have the first air utilization rate.

  When the utilization value priority operation continues for the first set time (for example, 10 minutes), the process proceeds from step SS3 to step S4, the temperature detection means 54 detects the temperature of the cell stack 6, and this detection signal is sent to the controller 52. And the detected temperature (T1) is stored in the memory means 72.

  Thus, after detecting the temperature state of the cell stack 6 in the utilization factor priority operation, the fuel utilization factor setting unit 64 sets a second fuel utilization factor (for example, 80%) higher than the first fuel utilization factor. (Step S5), the utilization factor increasing operation is performed by the increased second fuel utilization factor. Note that, in the utilization factor increasing operation, the air utilization factor is set to the first air utilization factor (for example, 38%) in the utilization factor priority operation, and the control means 60 causes the fuel to be the second fuel utilization factor. The gas blower 16 is controlled, and the air blower 26 is controlled to achieve the first air utilization factor.

  Then, the utilization factor increasing operation is continuously performed for a second predetermined time (for example, 2 hours), and when the operating state is stabilized, the process proceeds from step S5 to step S6 to step S7, and the temperature detecting means 54 The temperature of the cell stack 6 is detected, and the detected temperature (T2) is stored in the memory means 72.

  As described above, when the temperature state of the cell stack 6 in the utilization factor priority operation and the temperature state of the cell stack 6 in the utilization factor rising operation are detected, the temperature difference calculating means 62 determines the temperature of these temperature states in step S8. A difference, that is, a temperature difference (ΔT) between the detected temperature (T1) in the utilization priority operation and the detected temperature (T2) in the utilization value increase operation is calculated (ΔT = T1-T2). When switching from the utilization factor priority operation to the utilization factor rising operation, the air utilization factor is maintained at the first air utilization factor (for example, 38%), and the fuel utilization factor is for the first fuel utilization factor (for example, 78) As the fuel utilization rate rises to a second fuel utilization rate (for example, 80%), the consumption amount of fuel gas contributing to power generation in the cell stack 6 increases, and accordingly, the fuel in the combustion space 28 downstream of the cell stack 6 The amount of fuel gas consumed is reduced, and the temperature of the cell stack 6 is lowered somewhat (for example, lowered to about 743.degree. C. to about 740.degree. C.).

  Here, the detection error of the fuel gas flow rate measuring means 17 will be described. Generally, the fuel gas flow rate measuring means 17 used in such a solid oxide fuel cell system 2 has a detection error, for example, ± 3 Percent tolerances have been adopted. If there is no detection error in the fuel gas flow rate measuring means 17, the measured value of the fuel gas flow rate measuring means 17 becomes the actual supplied flow rate of the fuel gas, and in this case the relationship between the power output of the cell stack 6 and the fuel utilization rate As shown by a solid line A in FIG. 3, the fuel gas blower 16 is controlled so as to obtain the fuel utilization factor indicated by the solid line.

  However, if the fuel gas flow rate measuring means 17 indicates a value smaller than the actual supply flow rate value, and there is a detection error of, for example, -3%, in actuality, + 3% more fuel gas is supplied than this measured value. Control error occurs on the positive side, so the actual fuel utilization in this case is lower than the set fuel utilization (ie, the fuel utilization indicated by the solid line A), and The relationship between the output and the fuel utilization rate is as shown by a broken line B in FIG. On the other hand, when the fuel gas flow rate measuring means 17 indicates a value larger than the actual supply flow rate value, for example, if there is a + 3% detection error, fuel gas is actually supplied -3% less than this measured value. As the control error on the negative side occurs, the actual fuel utilization factor in this case is higher than the set fuel utilization factor (ie, the fuel utilization factor indicated by the solid line A), and the power output of the cell stack 6 and the fuel The relationship with the utilization rate is as shown by a dashed-dotted line C in FIG.

  The detection error of the fuel gas flow rate measuring means 17 also appears in the calculated temperature difference (ΔT) between the first detection temperature (T1) in the utilization factor priority operation and the second detection temperature (T2) in the utilization factor rising operation. In the first embodiment, the detection error of the fuel gas flow rate measuring means 17 is checked paying attention to the calculated temperature difference (ΔT) of the detected temperatures (T1, T2). That is, when the fuel gas flow rate measuring means 17 has no detection error, the temperature decrease width of the cell stack 6 is, for example, about 3 ° C. as described above. On the other hand, when there is a control error on the positive side (in other words, an error on the increase side) due to a detection error of the fuel gas flow rate measuring means 17, the calculated temperature difference (ΔT) (ie, the temperature decrease width) of this detected temperature is It becomes small compared with the case where there is no detection error.

  Further explaining, in the process of switching from the utilization factor priority operation to the utilization factor increasing operation (for example, an operation for increasing the fuel utilization factor by 2.0 points), the fuel gas flow rate measuring means 17 detects an error, particularly an error to the negative side. As the fuel gas flows more, the temperature decrease width becomes smaller than expected, and a new detection error of 2%, for example, occurs on the minus side in the measurement value. The difference (ΔT) (that is, the temperature decrease width) is, for example, about 0.8 ° C., which is smaller than about 3 ° C. of the temperature decrease width when there is no detection error.

  Because of this, after calculating the calculated temperature difference (ΔT) of the detected temperature, it is determined in step S9 whether the calculated temperature difference (ΔT) (temperature drop width) of the detected temperature is smaller than the reference temperature difference Ru. The reference temperature difference is set to, for example, about 3.1.degree. C. of the temperature decrease width in the case where there is no detection error. That is, the flow rate error determination means 68 compares the calculated temperature difference (ΔT) of the detected temperature with the reference temperature difference (for example, 3 ° C.), and the calculated temperature difference (ΔT) is smaller than the reference temperature difference Sometimes there is a deviation on the positive side between the measurement value of the fuel gas flow rate measurement means 17 and the actual flow rate of fuel gas, and in such a case, the flow rate error determination means 68 determines that the fuel gas flow rate measurement means 17 is positive. It is determined that there is a control error (step S10).

  If the flow rate error judging means 68 judges in this way, the fuel utilization factor setting means 64 sets the third fuel utilization factor (for example, 82%) as the fuel utilization factor (step S11) to further enhance the power generation efficiency of the system. Can. If the calculated temperature difference (ΔT) of the detected temperature is equal to or higher than the reference temperature, there is no detection error in the fuel gas flow rate measuring means 17 or the negative control error even if it exists (in other words, the shortage Because of the side error, the fuel utilization is maintained as it is.

  In the first embodiment, if there is a control error on the positive side of the fuel gas flow rate measuring means 17, the fuel utilization rate is raised to the third fuel utilization rate (for example, 82%). For the above, according to the detection error of the plus side of the fuel gas flow rate measuring means 17, it may be configured as follows. That is, even if the controller 52 includes a rising utilization rate calculating means (not shown) for calculating the rising utilization rate, the rising utilization rate calculating means may calculate the rising utilization rate to be raised from the second fuel utilization rate. Good.

  The rising utilization rate calculating means includes the temperature of the cell stack 6 in the utilization rate priority operation (the first detection temperature (T1) of the temperature detecting means 54) and the temperature of the cell stack 6 in the rising utilization rate operation (the first of the temperature detecting means 54). 2 Calculate the temperature difference between the calculated temperature difference (ΔT) of the detected temperature (T2) and the reference temperature difference, that is, the comparison temperature difference (ΔTH), and increase the utilization factor based on the value of this comparison temperature difference (ΔTS) Calculate When the comparison temperature difference (ΔTS) is large (or small), there is a large (or small) deviation between the measurement value of the fuel gas flow rate measuring means 17 and the actual flow rate of fuel gas. The value of the rising utilization factor calculated by the means also becomes large (or small).

The rising utilization rate by the rising utilization rate calculation means is, for example, the equation (2),
Rising utilization rate = α × comparison temperature difference (ΔTS)
It can be calculated using Here, α is a coefficient, and the coefficient α is a value derived experimentally. The degree of measurement error of the fuel gas flow rate measuring means 54 is taken into consideration by calculating the rising utilization rate in this way and adding the rising utilization rate to the second fuel utilization rate to calculate the third fuel utilization rate. The fuel utilization to be increased, ie the third fuel utilization, can be set.

  For example, the calculated temperature difference (ΔT) between the first detection temperature (T1) of the temperature detection means 54 in the utilization factor priority operation and the second detection temperature (T2) of the temperature detection means 54 in the rising utilization factor operation is fuel gas For example, when there is no change in detection error in the flow rate measuring means 54, it is 3.1 ° C., which matches the reference temperature difference (for example, 3.1 ° C.), and the comparison temperature difference (ΔTH) becomes zero. On the other hand, when the calculated temperature difference (ΔT) is, for example, 0.8 ° C. as described above, the comparative temperature difference (ΔTH) is 2.3 ° C., and the rising utilization factor calculating means calculates the above equation (2). Use 81, add 2.3 of this comparison temperature difference (ΔTH) to a coefficient (for example, 0.65), and add 1.5 points of this integration result to the second fuel utilization rate (for example, 80%) 81 .5% is set as the third fuel utilization rate.

  Next, with reference to FIGS. 5 and 6, a second embodiment of the solid oxide fuel cell system according to the present invention will be described. In the first embodiment described above, the fuel gas flow rate measuring means is utilized by utilizing the temperature difference between the first temperature state of the cell stack 6 in the utilization factor priority operation and the second temperature state of the cell stack 6 in the rising utilization factor operation. Although the measurement error is determined, in the second embodiment, the temperature priority operation is performed after the utilization value priority operation is performed, and the fuel gas flow rate measuring unit is performed using the air utilization ratio in the temperature priority operation. The determination of the measurement error of In the following embodiments, elements substantially the same as those in the first embodiment described above are denoted by the same reference numerals, and descriptions thereof will be omitted.

  5 and 6, in this second embodiment, the controller 52A includes air in addition to the fuel utilization setting means 64, the air utilization setting means 64, the flow rate error determination means 68A, the timer means 70A and the memory means 72A. The fuel utilization factor setting means 64 sets the fuel utilization factor as described above, and the air utilization factor setting means 66 includes the utilization factor calculation means 76 (which functions as an oxidant utilization factor calculation means). The air utilization factor calculation means 76 calculates the air utilization factor (second air utilization factor) based on the flow rate of air, and the flow rate error determination means 68A calculates the fuel gas flow rate as described later. It is determined whether or not there is a detection error of the measuring means 17. Further, the timer means 70A has a first setting time (for example, set to about 10 to 30 minutes) until the rated operation state is stabilized and a second setting time (for example, 1 to 10) for the temperature priority operation to be stabilized. (Set to about 3 hours) Furthermore, in the memory means 72A, a power generation output-Uf map showing the relationship between the power generation output of the cell stack 6 (see FIG. 1) and the fuel utilization rate, and a power generation showing the relationship between the power generation output of the cell stack 6 and the air utilization rate Power-Ua map, first set time, second set time, target temperature of cell stack set in temperature priority operation (for example, set to about 750 ° C.), second fuel set in this temperature priority operation The utilization factor (for example, 80%), the reference air utilization factor (reference oxidant utilization factor) serving as the judgment standard for detection error with the fuel gas flow rate measuring means 54, and the third fuel utilization set when the detection error occurs A rate (for example, 82%) is registered. The other configuration (the other configuration including the basic configuration of the solid oxide fuel cell system) in the second embodiment is the same as that of the first embodiment described above.

  In the solid oxide fuel cell system according to the second embodiment, the flow rate error of the fuel gas flow rate measuring means 17 is checked as follows. This flow rate error check is performed in an operating state in which the power generation output of the cell stack 6 is stable. When the power generation output of the cell stack 6 reaches the rated output (for example, 700 W), the process proceeds from step S21 to step S2, and the fuel utilization factor (Uf) is made the first fuel utilization factor (for example, 78%). If a utilization factor priority operation is performed with Ua) maintained at the first air utilization factor (for example, 38%) and this utilization factor priority operation continues for the first set time (for example, 10 minutes), step SS23 to step Proceeding to S24, the temperature priority operation is performed. The contents of execution from step S21 to step S23 are the same as the contents of execution from step S1 to step S4 described above.

  In step S24, the control means 60 switches to a temperature priority operation in which the temperature of the cell stack 6 is controlled to a target temperature (for example, 750 ° C.), and controls the air blower 26 to achieve this target temperature. Also, the fuel utilization setting means 64 sets a second fuel utilization (for example, 80%) higher than the first fuel utilization (for example, 78%), and the control means 60 performs the second fuel utilization. The fuel gas blower 16 is controlled so that

  Then, such a temperature priority operation is continuously performed for a second predetermined time (for example, 2 hours), and when this operation state is stabilized, the process proceeds from step S25 to step S26, and the air flow rate at this time is measured. The utilization factor computing means 76 computes the second air utilization factor based on the measured air flow rate, and the second air utilization factor is stored in the memory means 72A. In the temperature priority operation, since the cell stack 6 is in the rated operation state, the air utilization rate can be calculated from the air flow rate.

  Thus, when the second air utilization factor is calculated based on the air flow rate in the temperature priority operation, it is determined in step S27 whether the second air utilization factor is smaller than the reference air utilization factor. When switching from the utilization factor priority operation to the temperature priority operation, the fuel utilization factor rises to the second fuel utilization factor, so the consumption of fuel gas that contributes to power generation in the cell stack 6 increases, and hence the cell stack 6 The temperature of the cell stack 6 tends to decrease because the amount of fuel gas to be fueled in the combustion space on the downstream side of the fuel cell is reduced, but the temperature priority operation is performed. The supply flow rate of the oxidant gas is reduced.

  At this time, the detection error of the fuel gas flow rate measuring means 17 also appears in the second air utilization rate in the temperature priority operation, and in the second embodiment, the fuel gas flow rate measuring means focusing on the second air utilization rate 17 detection errors are checked. That is, when the fuel gas flow rate measuring means 17 has no detection error, the fuel utilization rate is raised from the first fuel utilization rate to the second fuel utilization rate, and the temperature of the cell stack 6 is controlled to become the target temperature. The air utilization rate is, for example, about 46%. On the other hand, when the fuel gas flow rate measuring means 17 has a detection error, in particular, an error on the positive side, the second air utilization factor is smaller than that in the case where there is no detection error.

  More specifically, if there is a detection error in the fuel gas flow rate measuring means 17 when the utilization value priority operation is switched to the temperature priority operation, in particular if there is an error on the positive side, more fuel gas flows, The decrease width decreases, so the amount of air squeezed at this time may be small, and the second air utilization factor is smaller than in the case where there is no measurement error, for example, in the fuel gas flow rate measuring means 17 If there is a% detection error, this second air utilization factor will be about 41.5%.

  Because of this, after the air flow rate is measured in the temperature priority operation, it is determined in step S27 whether the second air utilization factor is smaller than the reference air utilization factor. The reference air utilization factor is set to, for example, about 46% of the second air utilization factor when there is no detection error.

  In this case, the flow rate error judging means 68A compares the second air utilization factor with the reference air utilization factor (for example, 46%), and when the second air utilization factor is smaller than the reference air utilization factor, the fuel gas flow rate In this case, the flow rate error determination means 68A determines that the fuel gas flow rate measurement means 17 has an error on the positive side, in the positive side. (Step S28).

  If the flow rate error determination means 68A determines as such, the fuel utilization rate setting means 64 sets the third fuel utilization rate (for example, 82%) as the fuel utilization rate (step S29), and thus the fuel gas flow rate measurement means 17 By raising the fuel utilization rate to the third fuel utilization rate by the measurement error on the positive side, it is possible to further enhance the power generation efficiency without causing a shortage of fuel supply and the like. If the second air utilization factor is equal to or higher than the reference air utilization factor, there is no detection error in the fuel gas flow rate measuring means 17, or if there is a detection error on the negative side (in other words Because of the error, the fuel utilization is maintained as it is.

  In the second embodiment, if there is a measurement error on the positive side of the fuel gas flow rate measuring means 17, the fuel utilization rate is raised to the third fuel utilization rate (for example, 82%). As in the first embodiment, in accordance with the measurement error on the positive side of the fuel gas flow rate measuring unit 17, the third fuel utilization factor may be set by computing the rising utilization factor.

  Also in this case, the controller 52A includes the rising utilization factor calculating means (not shown), and the rising utilization factor calculating means determines the difference in air utilization factor between the second air utilization factor and the reference air utilization factor in the temperature priority operation An oxidizing material utilization difference), that is, a comparison air utilization difference (comparing oxidation material utilization difference) is calculated, and a rising utilization ratio is calculated based on the value of the comparison air utilization difference. If the comparison air utilization rate difference is large (or small), there is a large (or small) deviation between the measurement value of the fuel gas flow rate measuring means 17 and the actual flow rate of fuel gas The value of the rising utilization factor calculated by is also large (or small).

In this case, the rising utilization rate by the rising utilization rate calculation means is, for example, the equation (3),
It can be calculated using the rising utilization factor = α × the comparison air utilization factor difference. Here, α is a coefficient, and the coefficient α is a value derived experimentally.

  For example, when the reference air utilization rate is 46%, the second air utilization rate is, for example, 41.5%, and the comparison air utilization rate difference between the second air utilization rate and the reference air utilization rate is 4 The rising utilization factor calculation means calculates a point of, for example, 1.6 points by adding 4.5 of this comparison air utilization difference to a coefficient (for example, 0.35) using the above equation (3). As the third fuel utilization factor, 81.6% obtained by adding the rising utilization factor (for example, 1.6%) to the second fuel utilization factor (for example, 80%) is set.

  Next, with reference to FIGS. 7 and 8, a third embodiment of the solid oxide fuel cell system according to the present invention will be described. In the second embodiment described above, the temperature priority operation is performed after the utilization value priority operation is performed, and the measurement error of the fuel gas flow rate measurement unit is determined using the air utilization ratio in this temperature priority operation. However, in the third embodiment, the temperature priority operation is performed after the utilization value priority operation is performed, and the fuel gas flow rate measurement is performed using the air utilization ratio difference before and after the fuel utilization ratio is increased in the temperature priority operation. The measurement error of the means is determined.

  7 and 8, in the third embodiment, the controller 52B includes a fuel utilization setting means 64, an air utilization setting means 66, a flow rate error determination means 68B, an air utilization calculation means 76, a timer 70B and In addition to the memory means 72B, an air utilization difference calculation means 84 (functioning as an oxidation material utilization difference calculation means) is provided. The fuel utilization setting means 64 sets the fuel utilization in the same manner as described above, and the air utilization setting means 66 sets the air utilization as described above, and the air utilization calculation means 76 described above Calculate the air utilization rate as you did. In addition, the air utilization factor difference calculation means 84 calculates the utilization factor difference between the second air utilization factor and the third air utilization factor, that is, the calculation air utilization factor difference (calculation oxide material utilization factor difference) as described later. The flow rate error determining means 68B determines the presence or absence of a detection error of the fuel gas flow rate measuring means 17 as described later based on the calculated air utilization factor difference.

  Furthermore, the timer means 70B has a first set time (for example, set to about 10 to 30 minutes) until the rated operation state is stabilized and a second set time for the first and second temperature priority operations to be stabilized. Clock (for example, set to about 1 to 3 hours). Furthermore, in the memory means 72B, a power generation output-Uf map showing the relationship between the power generation output of the cell stack 6 and the fuel utilization rate, a map showing the relationship between the power generation output of the cell stack 6 and the air utilization rate, a first set time , Second set time, target temperature of the cell stack 6 set in the first and second temperature priority operations, second fuel utilization factor set in the second temperature priority operation, detection error in the fuel gas flow rate measuring means 54 A reference air utilization factor, which is a determination criterion of presence, and a third fuel utilization factor which is set when it is determined that a detection error is registered, are registered. The other configuration (the other configuration including the basic configuration of the solid oxide fuel cell system) in the third embodiment is the same as that of the second embodiment described above.

  In the solid oxide fuel cell system of the third embodiment, the flow rate error check of the fuel gas flow rate measuring means 17 is performed as follows. This flow rate error check is performed in the operating state where the power generation output of the cell stack 6 is stable, as described above. When the power generation output of the cell stack 6 reaches the rated output (for example, 700 W), the process proceeds from step S31 to step S32, and the fuel utilization factor (Uf) is made the first fuel utilization factor (for example, 78%). When the utilization factor priority operation is performed with Ua) maintained at the first air utilization factor (for example, 38%) and this utilization factor priority operation continues for the first set time (for example, 10 minutes), step S33 to step S33 are performed. At S34, the first temperature priority operation is performed. The contents of execution from step S31 to step S33 are the same as the contents of execution from step S21 to step S23 described above.

  In step S34, the control means 60 switches to a temperature priority operation in which the temperature of the cell stack 6 is controlled to a target temperature (for example, 750 ° C.), and controls the air blower 26 to achieve this target temperature. At this time, the fuel utilization setting unit 64 sets a first fuel utilization (for example, 78%), and the control unit 60 controls the fuel gas blower 16 so as to achieve the first fuel utilization.

  Then, such a first temperature priority operation is continuously performed for a second predetermined time (for example, 2 hours), and when the operation state is stabilized, the process proceeds from step S35 to step S36, and the air flow rate at this time is measured. The air utilization calculating means 76 calculates the second air utilization based on the measured air flow rate (step S38), and the second air utilization is stored in the memory means 72B.

  As described above, when the second air utilization factor is calculated based on the air flow rate in the first temperature priority operation, the process proceeds to step S38, where the controller 52B sets the second temperature priority operation. In the second temperature priority operation, the fuel utilization setting means 64 sets a second fuel utilization (for example, 80%) higher than the first fuel utilization (for example, 78%), and the control means 60 The fuel gas blower 16 is controlled so as to achieve the second fuel utilization rate, and the air blower 26 is controlled so that the temperature of the cell stack 6 (the temperature detected by the temperature detecting means 54) becomes a target temperature.

  Then, such a second temperature priority operation is continuously performed for a second predetermined time (for example, 2 hours), and when the operation state is stabilized, the process proceeds from step S39 to step S40, and the air flow rate at this time is measured. The air utilization factor calculation means 76 calculates the third air utilization factor based on the measured air flow rate (step S41), and the third air utilization factor is stored in the memory means 72B. The time during which the second temperature priority operation is performed may be performed for a third predetermined time (for example, one hour) different from the second predetermined time.

  Thus, when the third air utilization factor in the second temperature priority operation is calculated, the air utilization factor difference calculating means 84 calculates the second air utilization factor in the first temperature priority operation and the third air in the second temperature priority operation. The difference between the air utilization factor and the utilization factor is calculated, and the presence or absence of a detection error of the fuel gas flow rate measuring means 17 is determined based on the calculated air utilization factor difference.

  When switching from the first temperature priority operation to the second temperature priority operation, the fuel utilization rate rises to the second fuel utilization rate, so the consumption amount of fuel gas contributing to power generation in the cell stack 6 increases, and therefore, the cell Although the temperature of the cell stack 6 tends to decrease because the amount of fuel gas fueled in the combustion space on the downstream side of the stack 6 decreases, the temperature drop of the cell stack 6 is suppressed because the temperature priority operation is performed. The flow rate of air (oxidant gas) decreases.

  At this time, the detection error of the fuel gas flow rate measuring means 17 also appears in the air utilization factor difference in the first and second temperature priority operations, and in this third embodiment, the air utilization factor difference (computed air utilization factor difference The detection error of the fuel gas flow rate measuring means 17 is checked paying attention to. That is, when there is no detection error in the fuel gas flow rate measuring means 17, the second air utilization factor in the first temperature priority operation is, for example, about 40%, and the second temperature which raised the fuel utilization factor to the second fuel utilization factor The third air utilization factor in the priority operation is, for example, about 46%, and the air utilization factor difference (calculated air utilization factor difference) is, for example, 6 points. On the other hand, when there is a detection error, particularly an error on the positive side, in the fuel gas flow rate measuring means 17, this air utilization difference is smaller than in the case where there is no detection error and smaller than 6 points.

  To explain further, if there is a detection error in the fuel gas flow rate measuring means 17 when the first temperature priority operation is switched to the second temperature priority operation, in particular if a positive error is present, more fuel gas flows. The decrease in temperature decreases, so the amount of air squeezed may be small at this time, and the air utilization difference is smaller than in the case where there is no measurement error. If a detection error of 2% is present, this third air utilization factor will be about 41.5%.

  Because of this, after the difference between the second air utilization factor and the third air utilization factor is calculated, the air utilization factor difference (computed air utilization factor difference) is calculated as the reference air utilization factor at step S43. It is determined whether it is smaller than the difference. The reference air utilization factor is set to, for example, about 6 points of the air utilization factor difference when there is no detection error.

  In this case, the flow rate error determination means 68B compares the air utilization factor difference (computed air utilization factor difference) with the reference air utilization factor difference (for example, 6 points), and this air utilization factor difference is the reference air utilization factor difference. When it is smaller than the above, there is a plus side deviation between the measurement value of the fuel gas flow rate measurement means 17 and the actual flow rate of fuel gas, and in such a case, the flow rate error determination means 68B It is determined that there is an error on the plus side (step S44).

  If the flow rate error determination means 68B determines as such, the fuel utilization rate setting means 64 sets the third fuel utilization rate (for example, 82%) as the fuel utilization rate (step S45), and thus the fuel gas flow rate measurement means 17 By raising the fuel utilization rate to the third fuel utilization rate by the measurement error on the positive side, it is possible to further enhance the power generation efficiency without causing a shortage of fuel supply and the like. It should be noted that if this air utilization difference is equal to or greater than the reference air utilization difference, there is no detection error in the fuel gas flow rate measuring means 17, or if there is a detection error on the negative side (in other words, Because of the error, the fuel utilization is maintained as it is.

  Also in the third embodiment, similarly to the second embodiment, in accordance with the measurement error on the plus side of the fuel gas flow rate measuring means 17, the rising utilization rate is calculated to set the third fuel utilization rate Also in this case, the controller 52B can include the rising utilization rate calculating means (not shown).

  The rising utilization factor computing means is a difference in the air utilization factor between the air utilization factor difference (calculated air utilization factor difference) and the reference air utilization factor difference in the first and second temperature priority operations, that is, the comparison air utilization factor difference (comparative oxidation factor It is possible to calculate the material utilization rate difference and calculate the rising utilization rate based on the value of the comparison air utilization rate difference.

In this case, the rising utilization rate by the rising utilization rate calculation means is, for example, the equation (4),
It can be calculated using the rising utilization factor = α × the comparison air utilization factor difference. Here, α is a coefficient, and the coefficient α is a value derived experimentally.

  For example, when the reference air utilization difference is 6 points, if the calculated air utilization difference is 1.5 points, the comparison air utilization difference between the reference air utilization difference and the calculated air utilization difference is The rising utilization factor calculation means integrates the comparison air utilization difference of 4.5 to the coefficient (for example, 0.35) using the above equation (4) to obtain, for example, 1.6 points. 81.6% calculated by adding the rising utilization rate (for example, 1.6%) to the second fuel utilization rate (for example, 80%) as the third fuel utilization rate is set.

  Although the various 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 or changes may be made without departing from the scope of the present invention. It is possible.

  In order to confirm the effect of the present invention, the following simulation was performed. First, a control system of the solid oxide fuel cell system according to the first embodiment was simulated, and a system using a cell stack with a rated output of 700 W was assumed in this simulation. 1st fuel utilization factor is set to 78% and 1st air utilization factor to 38% in utilization value priority operation, no measurement error as measurement error of fuel gas flow rate measurement means, plus side 2% with this measurement error, The simulation was performed with a measurement error of 3% on the positive side.

  The simulation results are as shown in Table 1. As understood from the results shown in Table 1, when the fuel utilization rate is raised from the first fuel utilization rate (78%) to the second fuel utilization rate (80%), the temperature of the cell stack is lowered, but the decreasing tendency is The measurement error decreased as much as possible (the temperature difference increased when the measurement error was 3%). Then, the third fuel utilization factor is set according to the magnitude of the measurement error on the plus side, and in the case of the measurement error on the plus side 2%, the third fuel utilization factor is 81.6%, and the plus side 3% In the case of measurement error, the power generation efficiency was calculated when the third fuel utilization factor was set to 82.4% and the power generation operation was calculated, and both were 53.5%, and from the time of operation with the first fuel utilization factor It was also found that 1.1 points will be improved.

次いで、第２の実施形態の固体酸化物形燃料電池システムの制御系によるシミュレーションを、上述したと同様の条件で行った。利用率値優先運転において第１燃料利用率を７８％、第１空気利用率を３８％に設定し、温度優先運転において第２燃料利用率を８０％に設定し、燃料ガス流量計測手段の測定誤差として、測定誤差なし、プラス側２％この測定誤差ありについてシミュレーションを行った。

Next, simulation by the control system of the solid oxide fuel cell system of the second embodiment was performed under the same conditions as described above. Measurement of fuel gas flow rate measurement means, setting 1st fuel utilization to 78% and 1st air utilization to 38% in utilization value priority operation, 2nd fuel utilization to 80% in temperature priority operation As an error, a simulation was carried out with no measurement error, plus 2% with this measurement error.

  The simulation results are as shown in Table 2. As understood from the results shown in Table 2, when the operation is switched from the utilization value priority operation to the temperature priority operation, the air utilization ratio increases, but in the case of a measurement error of 2% on the plus side, up to 41.5% As a result of calculating the power generation efficiency when generating operation with the third fuel utilization set at 82% based on this increase, it is 53.8%, which is more than when operating at the first fuel utilization It turned out that it is improved by 1.4 points.

次に、第３の実施形態の固体酸化物形燃料電池システムの制御系によるシミュレーションを、上述したと同様の条件で行った。利用率値優先運転において第１燃料利用率を７８％、第１空気利用率を３８％に設定し、その後利用率値優先運転から第１温度優先運転に切り替え、この第１温度優先運転において第１燃料利用率を７８％に設定し、その後、第１温度優先運転から第２温度優先運転に切り替え、第２燃料利用率を８０％に設定し、測定誤差なし、プラス側２％この測定誤差ありについてシミュレーションを行った。

Next, simulation by the control system of the solid oxide fuel cell system of the third embodiment was performed under the same conditions as described above. The first fuel utilization factor is set to 78% and the first air utilization factor to 38% in the utilization value priority operation, and then the utilization value priority operation is switched to the first temperature priority operation, and in the first temperature priority operation (1) Set the fuel utilization rate to 78%, then switch from the first temperature priority operation to the second temperature priority operation, set the second fuel utilization rate to 80%, no measurement error, plus 2% measurement error The simulation was done about there.

  The simulation results are as shown in Table 3. As understood from the results shown in Table 3, when the first temperature priority operation is switched to the second temperature priority operation, the air utilization factor rises, and the third air utilization factor is 46% when there is no measurement error. Rises up to 41.5% in the case of a measurement error of 2% on the plus side, and at this time the power generation efficiency when generating operation with the third fuel utilization set at 82.4% is It is calculated that it is 53.8% and it is understood that it is improved by 1.4 points compared with the time of operating at the first fuel utilization rate.

比較のために、従来の条件のシミュレーションも行った。燃料ガス流量測定手段の測定誤差なしの場合は、燃料利用率を７８％及び８０％に設定し、この測定誤差プラス側２％の場合は、燃料利用率を８０％に設定し、またその測定誤差がプラス側３％の場合には、燃料利用率を８０％に設定して行った。

A simulation of conventional conditions was also performed for comparison. If there is no measurement error of the fuel gas flow measurement means, the fuel utilization is set to 78% and 80%, and if this measurement error plus 2%, the fuel utilization is set to 80%, and the measurement When the error was 3% on the plus side, the fuel utilization rate was set to 80%.

  The simulation results are as shown in Table 4. It was found that when the measurement error is on the positive side, the power generation efficiency is lower than in the case without the measurement error.

2 solid oxide fuel cell system 6 cell stack 16 fuel gas blower 17 fuel gas flow rate measuring means 26 air blower (oxidant gas blower)
27 Air flow rate measuring means (oxidant gas flow rate measuring means)
52, 52A, 52B controller 62 Temperature difference calculation means 64 Fuel utilization factor setting means 66 Air utilization factor setting means (oxidant material utilization factor setting means)
68, 68A, 68B Flow rate error judging means 76 Air utilization factor computing means 84 Air utilization factor difference computing means (oxidant material utilization factor difference computing means)

Claims (9)

A cell stack in which solid oxide fuel cells for generating electricity by reacting fuel gas and oxidant gas are stacked, and oxidant gas supply means for feeding oxidant gas to the oxygen electrode side of the cell stack A fuel gas supply means for supplying a fuel gas to the fuel electrode side of the cell stack, and a flow rate of the fuel gas supplied from the fuel gas supply means to the fuel electrode side of the cell stack Solid oxide type provided with fuel gas flow rate measuring means, temperature detection means for detecting the temperature of the cell stack, and controller for controlling the operation of the fuel gas supply means and the oxidant gas supply means A fuel cell system,
The controller sets fuel utilization factor setting means for setting the utilization factor of the fuel gas consumed in the power generation in the cell stack, and sets the utilization factor of the oxidant gas consumed in the power generation in the cell stack An oxidant utilization factor setting unit for determining the flow rate error of the fuel gas flow rate measuring unit;
In the rated power generation state of the cell stack, the controller performs the utilization value priority operation giving priority to the fuel utilization factor and the oxidant utilization factor, and in the utilization value priority operation, the fuel utilization factor setting unit is the first While the fuel utilization rate is set, the oxidant utilization rate setting means sets the first oxidant utilization rate, and then the controller performs the utilization rate increase operation in which the fuel utilization rate is increased, and the utilization rate rises. In operation, the oxidant utilization factor setting means maintains the first oxidant utilization factor, and the fuel utilization factor setting means sets a second fuel utilization factor higher than the first fuel utilization factor. The temperature detection means detects a first temperature state of the cell stack in the utilization factor priority operation and a second temperature state of the cell stack in the utilization factor rising operation, and the flow rate error The means determines the presence or absence of a detection error of the fuel gas flow rate measuring means based on the first detected temperature in the first temperature state and the second detected temperature in the second temperature state of the cell stack. Solid oxide fuel cell system.   The flow rate error determination means compares the calculated temperature difference between the first detected temperature and the second detected temperature of the temperature detection means with a reference temperature difference, and when the calculated temperature difference is smaller than the reference temperature difference The fuel gas flow rate measuring means determines that there is a positive side error, and the fuel utilization rate setting means sets a third fuel utilization rate higher than the second fuel utilization rate. Solid oxide fuel cell system as described.   The controller is configured to calculate an increase utilization rate to be further raised from the second fuel utilization rate when the flow rate error determining means determines that the fuel gas flow rate measuring means has a plus side error. And the rising utilization factor calculation means calculates the rising utilization factor based on a comparison temperature difference between the calculated temperature difference and the reference temperature difference, and the fuel utilization factor setting means includes the second fuel utilization factor 3. The solid oxide fuel cell system according to claim 2, wherein the third fuel utilization factor is set by adding the rising utilization factor to. A cell stack in which solid oxide fuel cells for generating electricity by reacting fuel gas and oxidant gas are stacked, and oxidant gas supply means for feeding oxidant gas to the oxygen electrode side of the cell stack A fuel gas supply means for supplying a fuel gas to the fuel electrode side of the cell stack, and a flow rate of the fuel gas supplied from the fuel gas supply means to the fuel electrode side of the cell stack A fuel gas flow rate measuring means, an oxidant gas flow rate measuring means for measuring the flow rate of the oxidant gas supplied from the oxidant gas supply means to the oxygen electrode side of the cell stack, a temperature of the cell stack A solid oxide fuel cell system comprising: temperature detection means for detecting; and a controller for controlling the operation of the fuel gas supply means and the oxidant gas supply means. Te,
The controller sets fuel utilization factor setting means for setting the utilization factor of the fuel gas consumed in the power generation in the cell stack, and sets the utilization factor of the oxidant gas consumed in the power generation in the cell stack An oxidant utilization factor setting unit for determining the flow rate error of the fuel gas flow rate measuring unit;
In the rated power generation state of the cell stack, the controller performs the utilization value priority operation giving priority to the fuel utilization factor and the oxidant utilization factor, and in the utilization value priority operation, the fuel utilization factor setting unit is the first While setting the fuel utilization factor, the oxidant utilization factor setting means sets the first oxidant utilization factor, and then the controller performs a temperature priority operation so that the temperature detected by the temperature sensing means becomes the target temperature. In the temperature priority operation, the fuel utilization setting means sets the second fuel utilization higher than the first fuel utilization, and the oxidant gas supply means detects the temperature detected by the temperature detection means. Is controlled to become the target temperature, and then the flow rate error determination means measures the fuel gas flow rate based on the second oxidant utilization factor in the temperature priority operation Solid oxide fuel cell system, characterized by determining the presence or absence of detection error.   The controller includes an oxidant utilization factor computing unit for computing an oxidant utilization factor, and the oxidant utilization factor computing unit is configured to calculate the second oxidant based on a supply flow rate of oxidant gas in the temperature priority operation. The utilization factor is calculated, the flow rate error judging means compares the second oxidant utilization factor with the reference oxidant utilization factor in the temperature priority operation, and the second oxidant utilization factor is the reference oxidant utilization factor When the fuel gas flow rate measuring unit determines that there is a plus error, the fuel gas flow rate measuring unit sets a third fuel utilization rate higher than the second fuel utilization rate. The solid oxide fuel cell system according to claim 4.   The controller includes an elevated utilization rate calculation means for calculating an elevated utilization rate to be further elevated from the second fuel utilization rate when the flow rate error determination means determines that there is a positive side error, and the elevated utilization rate The computing means computes the rising utilization rate based on the difference between the second oxidant utilization rate and the reference oxidant utilization rate, and the fuel utilization setting means determines the second fuel utilization rate. The solid oxide fuel cell system according to claim 5, wherein the third fuel utilization factor is set by adding the rising utilization factor to the third fuel utilization factor. A cell stack in which solid oxide fuel cells for generating electricity by reacting fuel gas and oxidant gas are stacked, and oxidant gas supply means for feeding oxidant gas to the oxygen electrode side of the cell stack A fuel gas supply means for supplying a fuel gas to the fuel electrode side of the cell stack, and a flow rate of the fuel gas supplied from the fuel gas supply means to the fuel electrode side of the cell stack A fuel gas flow rate measuring means, an oxidant gas flow rate measuring means for measuring the flow rate of the oxidant gas supplied from the oxidant gas supply means to the oxygen electrode side of the cell stack, a temperature of the cell stack A solid oxide fuel cell system comprising: temperature detection means for detecting; and a controller for controlling the operation of the fuel gas supply means and the oxidant gas supply means. Te,
The controller sets fuel utilization factor setting means for setting the utilization factor of the fuel gas consumed in the power generation in the cell stack, and sets the utilization factor of the oxidant gas consumed in the power generation in the cell stack An oxidant utilization factor setting unit for determining the flow rate error of the fuel gas flow rate measuring unit;
In the rated power generation state of the cell stack, the controller performs the utilization value priority operation giving priority to the fuel utilization factor and the oxidant utilization factor, and in the utilization value priority operation, the fuel utilization factor setting unit is the first While setting the fuel utilization factor, the oxidant utilization factor setting means sets the first oxidant utilization factor, and then the controller gives priority to the first temperature so that the temperature detected by the temperature detector becomes the target temperature. In operation, in the first temperature priority operation, the fuel utilization setting means sets the first fuel utilization, and the oxidant gas supply means detects that the temperature detected by the temperature detection means is the target temperature After that, the controller performs the second temperature priority operation, and in the second temperature priority operation, the fuel utilization factor setting unit performs the first fuel priority operation. The second fuel utilization rate higher than the usage rate is set, and the oxidant gas supply means is controlled so that the temperature detected by the temperature detection means becomes the target temperature, and the flow rate error determination means (1) Solid oxide characterized in that the presence or absence of detection error of the fuel gas flow rate measuring means is determined based on the second oxidant utilization factor in the temperature priority operation and the third oxidant utilization factor in the second temperature priority operation. Fuel cell system.   The controller includes an oxidant utilization factor computing unit for computing an oxidant utilization factor, and the oxidant utilization factor computing unit is configured to perform the second operation based on a supply flow rate of oxidant gas in the first temperature priority operation. The oxidant utilization factor is calculated, and the third oxidant utilization factor is computed based on the supply flow rate of the oxidant gas in the second temperature priority operation, and the flow rate error determination means determines the utilization rate of the second oxidant. And comparing the difference between the calculated oxidizing material utilization rate of the third oxidizing material utilization rate and the reference oxidizing material utilization rate difference, and the calculated oxidizing material utilization rate difference is smaller than the reference oxidizing material utilization difference. The solid according to claim 7, wherein the flow rate measuring means is determined to have a positive side error, and the fuel utilization factor setting means sets a third fuel utilization factor higher than the second fuel utilization factor. Oxide fuel cell system . The controller is configured to calculate an increase utilization rate to be further raised from the second fuel utilization rate when the flow rate error determining means determines that the fuel gas flow rate measuring means has a plus side error. And the rising utilization factor computing means calculates the rising utilization factor based on a comparison between the calculated oxidant utilization factor difference and the reference oxidant utilization factor difference based on the oxidant utilization factor difference, and the fuel utilization factor setting. 9. The solid oxide fuel cell system according to claim 8, wherein the means sets the third fuel utilization factor obtained by adding the rising utilization factor to the second fuel utilization factor.

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