JP5829936B2 - Solid oxide fuel cell system and method for operating solid oxide fuel cell system - Google Patents

Description

  The present invention relates to a solid oxide fuel cell system, and more particularly to a system capable of performing deterioration suppression control when a fuel cell stack (an assembly of fuel cells) is deteriorated, and an operation method at the time of deterioration.

  A solid oxide fuel cell system (hereinafter referred to as an “SOFC system”) generally includes a reformer that reforms a hydrocarbon-based fuel to produce a hydrogen-rich reformed fuel, and a reformer from the reformer. A fuel cell stack, which is an assembly of a plurality of solid oxide fuel cells that generate electricity by an electrochemical reaction between a solid fuel and air, and the reformer and the fuel cell stack. And a module case that burns excess reformed fuel to maintain the reformer and the fuel cell stack at a high temperature. These are the main parts of the system and are collectively called hot modules.

  The SOFC system is based on continuous operation at a high temperature, but if the fuel cell stack (assembly of fuel cell) deteriorates due to long-term use, not only will the power generation capacity decrease, but the internal resistance will increase, resulting in Joule heat. As a result, the temperature of the fuel cell stack rises excessively. An excessive temperature increase accelerates the deterioration of the fuel cell stack. Accordingly, there is a demand for suppressing deterioration of the fuel cell stack.

  The technique described in Patent Document 1 is a correction that reduces the rated output power in the subsequent operation so that the fuel supply amount is decreased when it is determined that the fuel cell stack has deteriorated (at the time of the first deterioration determination). When it is determined that the fuel cell stack has deteriorated after the first deterioration determination (second deterioration determination), the rated output power in the subsequent operation is further reduced so that the fuel supply amount is further reduced. Is corrected with a reduction range larger than that at the time of the first deterioration determination.

  According to this, since the rated output power is reduced at the time of the first deterioration determination with a reduction width smaller than that at the time of the second deterioration determination, sufficient output power is obtained while suppressing the deterioration of the fuel cell stack. be able to. That is, sufficient output is obtained in the early stage when the deterioration of the fuel cell stack is not progressing much, and when the deterioration progresses, the burden on the fuel cell stack is greatly reduced, so that the deterioration of the fuel cell stack is sufficiently suppressed. be able to.

JP2011-102111A

  However, the technique described in Patent Document 1 reduces the cell temperature of the fuel cell stack and temporarily suppresses deterioration by reducing the rated output power so that the fuel supply amount is reduced when the battery deteriorates. However, it is not possible to sufficiently suppress deterioration because the cooling effect is insufficient only by reducing the rated output power. For this reason, the cell temperature rise of the fuel cell stack and the reduction of the rated output power are frequently repeated, and the rated output power may be greatly reduced.

  Further, in the practical fuel cell system, the allowable reduction in the rated output power is about 15%, so there is a limit to repeatedly reducing the rated output power.

  In the present invention, in view of such a situation, when the cell temperature of the fuel cell stack (synonymous with the stack temperature) is excessively increased due to deterioration or the like, cooling is performed by accurately controlling the fuel utilization rate and the air utilization rate. Thus, it is an object to prevent deterioration from being accelerated.

In order to solve the above problems, the present invention sets the fuel usage rate and the air usage rate according to the target generated power, and sets the fuel usage rate and the air usage rate small when the target generated power is low. As the generated power rises, the fuel utilization rate and air utilization rate are set to be large, while the cell temperature of the fuel cell stack is detected, and when this exceeds the first predetermined temperature for deterioration determination, deterioration suppression is suppressed. Therefore, the fuel utilization rate is increased as compared with the normal time, and at the same time, the air utilization rate is corrected to be decreased. Based on the target generated power, the fuel utilization rate, and the air utilization rate, the fuel supply amount to the reformer and the air supply amount to the fuel cell stack are calculated and controlled.

  According to the present invention, when the cell temperature of the fuel cell stack exceeds the first predetermined temperature for deterioration determination, the fuel utilization rate is increased, and at the same time, the air utilization rate is decreased. By simultaneously increasing the amount, it is possible to obtain an overall and large cooling effect, suppress a temperature rise, suppress further progression of deterioration, that is, avoid deterioration acceleration.

In addition, when only reducing the air utilization rate (air increase), in order to obtain a sufficient cooling effect, it is necessary to perform an air increase of a certain degree or more. As a result, in the fuel cell, the air introduction part The side close to is cooled excessively, and heat is generated in the cell. Thus, when heat is unevenly distributed in the cell, expansion may occur in the high temperature portion and shrinkage in the low temperature portion, which may lead to cell cracking.
Therefore, by simultaneously performing fuel reduction and air increase, it is possible to reduce the air increase required when the cell deteriorates, thereby suppressing local overcooling of the cell, expanding the uneven heat in the cell, and its vicious cycle Can be prevented.

Further, when only increasing the fuel utilization rate (fuel reduction), in order to obtain a sufficient temperature decrease, the fuel reduction must be performed to a certain degree or more, and as a result, the air-fuel ratio of the off gas becomes lean. As a result, misfire may occur in the off-gas combustion section, and the heat balance in the hot module may be lost.
Therefore, by simultaneously performing fuel reduction and air increase, fuel loss can be reduced, off-gas misfire can be suppressed, heat balance change and reformer temperature drop can be prevented, and system reliability can be improved. can do.

1 is an overall configuration diagram of a SOFC system showing an embodiment of the present invention. Configuration diagram of the hot module part of the SOFC system The figure which shows the map for setting of fuel utilization rate and air utilization rate Flowchart of determination routine for normal mode and deterioration suppression mode Flow chart of fuel and air control routine according to normal mode and deterioration suppression mode

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is an overall configuration diagram of a SOFC system showing an embodiment of the present invention.
The SOFC system includes a hot module 1 as a main part (power generation unit), a power conditioner (PCS) 15 that extracts the generated power of the hot module 1, and a heat exchanger that collects waste heat from the hot module 1 to obtain hot water. 18, a hot water tank 19 that stores hot water, and a control unit 30 that forms the core of a control device that controls these.

First, the hot module 1 will be described.
The hot module 1 is configured by arranging a reformer 3, a fuel cell stack 4 (an assembly of a plurality of fuel cells 5), and an off-gas combustion unit 6 in a module case 2.

The module case 2 is configured by lining a heat insulating material on the inner surface of a box-shaped outer frame formed of a heat-resistant metal. Further, a feed passage 7 for raw fuel (hydrocarbon fuel or the like), a feed passage 8 for water for steam reforming (reformed water), and a feed passage 9 for cathode air are provided from the outside into the case. ing.
If necessary, the raw fuel supply passage 7 is provided with a desulfurizer 10 for removing sulfur compounds in the raw fuel, and the reforming air supply passage is provided downstream of the raw fuel supply passage 7 in the desulfurizer 10. 11 is connected. Each supply passage 7, 8, 9, 11 is provided with an appropriate supply amount control device (pump and / or flow control valve) 7 p, 8 p, 9 p, 11 p.

  The reformer 3 is configured by filling a chamber in a case formed of a heat-resistant metal with a reforming catalyst, and is connected to supply paths 7 and 8 for raw fuel and reforming water from the outside. . Therefore, the reformer 3 reforms the raw fuel by a steam reforming reaction in the presence of water vapor obtained by vaporizing water to generate hydrogen-rich fuel gas (reformed gas). Instead of the steam reforming reaction, the reformed gas may be generated by a technique known as a hydrogen generation technique such as a partial oxidation reaction or an autothermal reforming reaction, or a combination of these reforming reactions.

  The fuel cell stack 4 is an assembly in which a plurality of solid oxide fuel cells 5 are connected in series. Each cell 5 has a fuel electrode (anode) and an air electrode (cathode) on both sides of the solid oxide electrolyte. The reformed gas is supplied to the fuel electrode through the reformed gas supply passage 12 from the outlet of the reformer 3, and the air electrode is supplied with air through the cathode air supply passage 9 from the outside. The

Therefore, in each fuel cell 5, an electrode reaction of the following formula (1) occurs in the air electrode, and an electrode reaction of the following formula (2) occurs in the fuel electrode to generate power.
Air electrode: 1 / 2O ₂ + 2e ⁻ → O ²⁻ (solid electrolyte) (1)
Fuel electrode: O ²⁻ (solid electrolyte) + H ₂ → H ₂ O + 2e ⁻ (2)

  The off-gas combustion unit 6 is provided in the module case 2 and combusts surplus reformed gas in the fuel cell stack 4 in the presence of surplus air, and the reformer 3 and the fuel cell stack 4 are caused by the combustion heat. Maintain high temperature. Therefore, the inside of the module case 2 becomes a high temperature of, for example, about 600 to 1000 ° C. due to power generation in the fuel cell stack 4 and combustion of excess reformed gas. The high-temperature exhaust gas generated by the combustion in the module case 2 is discharged out of the module case 2, but the waste heat is used as described later.

  FIG. 2 is a configuration diagram showing a more practical example of the hot module 1. In this example, the reformer 3 is disposed in the upper part of the module case 2, the manifold 13 described later is disposed in the lower part, and the fuel cell stack 4 (an assembly of fuel cells) is disposed therebetween. .

  The manifold 13 also serves as a support for the fuel cell stack 4 and distributes the reformed gas supplied from the reformer 3 through the reformed gas supply passage 12 to each fuel cell of the fuel cell stack 4.

  Each fuel cell of the fuel cell stack 4 is, for example, a fuel electrode support type fuel cell, and a fuel electrode layer, a solid electrolyte layer, and an air electrode layer are formed on the outer surface of a porous cell support 5s extending in the vertical direction. (Not shown) are laminated in this order.

  The cell support 5s is provided with a gas flow path (not shown) along the extending direction therein, and the lower end thereof is connected to the manifold 13. The upper end of the gas flow path opens toward the case wall of the reformer 3, and constitutes the off-gas combustion unit 6.

  Therefore, the reformed gas supplied to the manifold 13 is distributed to the fuel cells constituting the fuel cell stack 4 and flows (increases) through the gas flow paths formed inside each cell support 5s. In this process, hydrogen in the reformed gas permeates through the porous layer of the cell support 5s and reaches the fuel electrode layer. On the other hand, air (oxygen-containing gas) is introduced into the module case 2 from the cathode air supply passage 9 and supplied to the outside of the fuel cells constituting the fuel cell stack 4. Reach the layer. Thereby, in each fuel cell, electric power is generated by an electrochemical reaction between hydrogen in the reformed gas and oxygen in the air.

  Of the reformed gas flowing through the gas flow path of the cell support 5s, the reformed gas that has not been used for the electrode reaction is caused to flow into the module case 2 from the upper end of the cell support 5s, and burned simultaneously with the outflow. It is done. An appropriate ignition device (not shown) is disposed in the module case 2 (off-gas combustion unit 6). Moreover, the air which was not used for the electrode reaction among the air introduced in the module case 2 is utilized for combustion. Exhaust gas generated by combustion in the module case 2 is discharged out of the module case 2 through the exhaust passage 14.

  Although the fuel cell of the fuel cell stack 4 has been described as a fuel electrode-supported fuel cell, an air-electrode-supported fuel cell (an air electrode layer, solid on the outer surface of the porous cell support 5s). An electrolyte layer and a fuel electrode layer may be laminated in this order). In this case, the module case 2 is filled with the reformed gas from the reformer 3, and air is supplied to the gas flow path of the cell support 5s via the manifold 13.

Returning to FIG. 1, the description will be continued.
The power conditioner (PCS) 15 takes out the DC power generated in the fuel cell stack 4 of the hot module 1 and includes an inverter to convert the DC power into AC power to load the household load (electric equipment). 16 is supplied. When the power generated by the fuel cell stack 4 is less than the demand power of the domestic load 16, the system power from the system power supply 17 is supplied to the domestic load 16 as a shortage.

  The heat exchanger 18 collects waste heat of the hot module 1 (heat of exhaust gas including heat generated in the fuel cell stack 4) to obtain hot water. The hot water tank 19 is configured to store the hot water obtained by the heat exchanger 18 and to supply the hot water to the hot water supply load.

  Specifically, the heat exchanger 18 is disposed on the power generation unit side and is connected to the hot water storage tank 19 on the hot water supply unit side and circulation passages 20a and 20b. The circulation passage 20a is drawn out from the bottom of the hot water tank 19 and connected to the inlet side of the heat exchanger 18, and a circulation pump 21 is interposed in the middle. The circulation passage 20 b is piped so as to return from the outlet side of the heat exchanger 18 to the upper part of the hot water tank 19.

Accordingly, when the circulation pump 21 is driven, relatively low-temperature water existing near the bottom of the hot water storage tank 19 is supplied to the heat exchanger 18 through the circulation passage 20a, and the heat exchanger 18 wastes heat from the hot module 1. Heat exchange with (heat of exhaust gas) is performed. As a result, the exhaust gas is cooled and the water is heated to obtain hot water. The hot water obtained in the heat exchanger 18 is returned to the upper part of the hot water tank 19 through the circulation passage 20b. Such circulation is repeated and hot water is stored in the hot water tank 19.
The hot water tank 19 is provided with a hot water supply passage 22 for extracting hot water from the upper portion thereof, and a water supply passage 23 for supplying tap water to the bottom portion thereof.

  The control unit 30 controls the power generated by the fuel cell stack 4 and the operation of the circulation pump 21 and is constituted by a microcomputer and includes a CPU, a ROM, a RAM, an input / output interface, and the like. A control device is configured including the control unit 30 and various sensors and control devices connected to the input side and the output side thereof.

  When controlling the generated power of the fuel cell stack 4, the control unit 30 sets the target generated power of the fuel cell stack 4 within the range of the rated output power (maximum generated power) according to the demand power of the household load 16. To do. In other words, the target generated power is set to the maximum power that can be generated within the range of the demand power according to the demand power.

  The control unit 30 controls the power conditioner 15 based on the set target generated power. Specifically, the current taken out from the fuel cell stack 4 is set and controlled based on the target generated power of the fuel cell stack 4. More specifically, the target generated power of the fuel cell stack 4 is divided by the output voltage (instantaneous value) of the fuel cell stack 4, a target current is set, and the current extracted from the fuel cell stack 4 is controlled according to the target current. .

  The control unit 30 also supplies the raw fuel, reformed water to the reformer 7 via the supply amount control devices 7p, 8p, 11p based on the set target generated power (so as to obtain the target generated power). The supply amount of reforming air is controlled to control the supply amount of reformed gas (anode gas) to the fuel cell stack 4, and the air to the fuel cell stack 4 is supplied via the supply amount control device 9p. (Cathode gas) supply amount is controlled. That is, the generated power of the fuel cell stack 4 is controlled mainly by controlling the fuel supply amount to the reformer 7 and the air supply amount to the fuel cell stack 4.

Further, when the fuel and air supply amounts are controlled in accordance with the target generated power of the fuel cell stack 4, the fuel utilization rate Uf and the air utilization rate Ua are controlled to desired values.
The fuel utilization rate Uf refers to the proportion (%) of the fuel used for power generation out of the fuel supplied to the reformer 3. Therefore, if the amount of fuel required to obtain the target generated power is Gf, the amount of fuel supplied to the reformer 3 is Gf × 100 / Uf. Therefore, an increase in the fuel utilization rate Uf means a fuel decrease, and a decrease in the fuel utilization rate Uf means an increase in fuel.
The air utilization rate Ua refers to the proportion (%) of air used for power generation in the air supplied to the fuel cell stack 4. Therefore, if the amount of air necessary to obtain the target generated power is Ga, the amount of air supplied to the fuel cell stack 4 is Ga × 100 / Ua. Therefore, an increase in the air utilization rate Ua means a decrease in air, and a decrease in the air utilization rate Ua means an increase in air.

FIG. 3 is a characteristic diagram (setting map) of the fuel usage rate Uf and the air usage rate Ua, showing changes in the fuel usage rate Uf and the air usage rate Ua with respect to changes in the target generated power, as well as the fuel usage rate Uf and the air. The relationship with the utilization factor Ua is shown.
The fuel utilization rate Uf and the air utilization rate Ua are cooperatively controlled according to a prescribed profile (FIG. 3).

In FIG. 3, Δ is a characteristic at normal time (normal mode), and when the target generated power is low, the fuel utilization rate Uf and the air utilization rate Ua are set small, and the fuel utilization rate increases as the target generated power increases. Uf and air utilization rate Ua are set large.
For example, the fuel usage rate Uf in the normal mode is set to be larger as the target generated power becomes larger in accordance with the target generated power.

The air utilization rate Ua in the normal mode is set differently depending on whether the fuel utilization rate Uf is a predetermined value (for example, 50%) or less and a predetermined value or more.
(1) When Uf ≦ predetermined value Ua = A1 × Uf
However, A1 is a predetermined coefficient (for example, 0.5 to 1.0).
(2) When Uf> predetermined value Ua is constant at the upper limit regardless of Uf.

On the other hand, □ in FIG. 3 is a characteristic at the time of deterioration (deterioration suppression mode). With the same target generated power, the control point is moved diagonally to the lower right, and the fuel utilization rate is increased compared to the normal time. At the same time, increase the air utilization rate.
For example, the fuel utilization rate Uf in the deterioration suppression mode is increased by 1 to 8 points at each output relative to the normal mode. However, in the region where Uf is low (region where the output is small), adjustment is made to reduce the increase.

  The air utilization rate Ua in the deterioration suppression mode is decreased by 1 to 10 points at each output with respect to the normal mode. However, in a region where Ua is low, adjustment is made so that Ua does not become a negative value.

For detecting the deterioration of the fuel cell stack 4 (an assembly of fuel cells), a cell temperature sensor 31 (see FIG. 2) is used as a temperature detection unit for detecting the cell temperature of the fuel cell stack 4, and the cell temperature is deteriorated. When the first predetermined temperature T1 for determination is exceeded, the mode is shifted to the deterioration suppression mode.
The cell temperature sensor 31 may be attached to the cell support 5s so as to detect the temperature of the representative point (the temperature of the highest temperature part or the average temperature part). Also, a plurality of them may be provided to calculate the average value. When a plurality of cells are provided, they may be attached to different cell supports 5s, but may be provided at different positions in the extending direction of the cell supports 5s.

FIG. 4 is a flowchart of a routine for determining the normal mode and the deterioration suppression mode executed by the control unit 30.
In S1, the normal mode is set as the initial setting.
During the normal mode setting, the cell temperature detected by the cell temperature sensor 31 is read in S2, and the cell temperature is compared with a first predetermined temperature T1 (for example, 750 ° C.) for deterioration determination.
As a result of the comparison, when the cell temperature ≦ T1, the normal mode of S1 is continued.

On the other hand, when the cell temperature> T1, the fuel cell is regarded as being deteriorated, and the process proceeds to S3 to shift to the deterioration suppressing mode.
When the mode is shifted to the degradation suppression mode, it is determined in S4 whether or not a predetermined time (for example, 30 minutes) has elapsed since the transition, and the degradation suppression mode of S3 is continued at least until the predetermined time has elapsed.

If the predetermined time has elapsed after the transition to the deterioration suppression mode, the process proceeds to S5, the cell temperature detected by the cell temperature sensor 31 is read, and the cell temperature is compared with the second predetermined temperature T2. The second predetermined temperature T2 is a threshold value for determining whether or not the temperature has risen from an excessive temperature rise state, and is set to T2 <T1, or T2 ≦ T1, preferably about 10 ° C. lower than T1. The
As a result of the comparison, when the cell temperature ≧ T2, the deterioration suppression mode of S3 is continued.
On the other hand, if the cell temperature is less than T2, it is considered that the cell has been cooled, and the process returns to S1 to return to the normal mode.

FIG. 5 is a flowchart of a fuel and air control routine corresponding to the normal mode and the deterioration suppression mode.
In S11, the target generated power Wg is calculated. Specifically, the target generated power Wg is set to the maximum power that can be generated within the range of the demand power according to the demand power of the household load 16. That is, if demand power <rated output power, the target generated power Wg = demand power is set, and if demand power> rated output power, the target generated power Wg = rated output power is set.
In S12, as a result of the flow of FIG. 4, it is determined whether the mode is the normal mode or the deterioration suppression mode.

  In the normal mode, the process proceeds to S13, and the fuel utilization rate Uf and the air utilization rate Ua are set from the target generated power Wg according to the normal mode map, that is, the characteristic at the normal time (characteristic of Δ) in FIG. In this case, when the target generated power is low, the fuel utilization rate Uf and the air utilization rate Ua are set small, and as the target generated power increases, the fuel utilization rate Uf and the air utilization rate Ua are set large. Note that step S13 functions as a utilization rate basic setting unit.

  In the case of the deterioration suppression mode, the process proceeds to S14, and the fuel usage rate Uf and the air usage rate Uf are set from the target generated power Wg according to the map of the deterioration suppression mode, that is, the characteristics at the time of deterioration (characteristic □) in FIG. In this case, the fuel utilization rate Uf is set to be large compared with the normal time, and at the same time, the air utilization rate Ua is set to be small. Note that step S14 functions as a utilization rate basic setting unit and a utilization rate correction unit at the time of deterioration.

  The setting (basic setting and correction) of the fuel utilization rate Uf and the air utilization rate Ua may be performed with reference to a map or may be performed by calculation based on the above-described setting method.

After setting the fuel utilization rate Uf and the air utilization rate Ua in S13 or S14, the process proceeds to S15.
In S15, the fuel supply amount is calculated from the target generated power Wg and the fuel utilization rate Uf. That is, if the amount of fuel necessary to obtain the target generated power Wg is Gf, the fuel supply amount = Gf × 100 / Uf. After the fuel supply amount is calculated, the fuel supply amount control device 7p is controlled based on the calculation.

  In S16, the air supply amount is calculated from the target generated power Wg and the air utilization rate Ua. That is, assuming that the amount of air necessary to obtain the target generated power Wg is Ga, the air supply amount = Ga × 100 / Ua. After the calculation of the air supply amount, the air supply amount control device 9p is controlled based on this. Note that steps S15 and S16 function as a supply amount calculation unit.

  According to the present embodiment, the control device sets the fuel utilization rate and the air utilization rate according to the target generated power, the utilization rate basic setting unit, the temperature detection unit that detects the cell temperature of the fuel cell stack 4, and the cell When the temperature exceeds the first predetermined temperature T1, the utilization rate correction unit increases the fuel utilization rate and reduces the air utilization rate at the same time as normal, and the target generated power, the fuel utilization rate, and the air utilization. And a supply amount calculation unit that calculates a fuel supply amount to the reformer 3 and an air supply amount to the fuel cell stack 4 based on the rate, in particular, the cells of the fuel cell stack 4 When the temperature exceeds the first predetermined temperature T1 for deterioration determination, the fuel utilization rate is increased and at the same time the air utilization rate is decreased. And large To obtain a cooling effect to suppress the temperature rise, the further progress of the deterioration prevention, that is, to avoid accelerated aging.

  In addition, by performing fuel reduction and air increase at the same time, it is possible to reduce the air increase required when the cell deteriorates, thereby suppressing local overcooling of the cell and the difference in thermal expansion due to uneven heat in the cell. It is possible to prevent cell destruction and the like caused by.

  Further, by simultaneously performing the fuel reduction and the air increase, the fuel reduction can be reduced, the change in the air-fuel ratio can be reduced, and the misfire of the off gas can be suppressed. Thereby, the change of the heat balance in the hot module 1 and the temperature fall of the reformer 3 can be prevented, and the reliability of the system can be improved.

  Further, according to the present embodiment, when the target generated power is low, the utilization rate basic setting unit sets the fuel utilization rate and the air utilization rate to be small, and the fuel utilization rate and the air increase as the target generated power increases. By setting the utilization factor large, the fuel utilization factor and the air utilization factor can be appropriately set in relation to the target generated power.

  In addition, according to the present embodiment, the target generated power is set to the maximum power that can be generated within the range of the demand power according to the demand power, so that the operation following the demand power, that is, the load becomes possible. .

  Further, according to the present embodiment, when the cell temperature falls below the second predetermined temperature T2 after the fuel utilization rate and the air utilization rate are corrected, the utilization rate correction unit adjusts the fuel utilization rate and the air utilization rate. In a situation where deterioration acceleration can be avoided by ending the correction and returning to the normal control, the control can be returned to the normal control and suitably controlled according to the prescribed profile.

  The illustrated embodiments are merely examples of the present invention, and the present invention is not limited to those directly described by the described embodiments, and various improvements and modifications made by those skilled in the art within the scope of the claims. Needless to say, it encompasses changes.

DESCRIPTION OF SYMBOLS 1 Hot module 2 Module case 3 Reformer 4 Fuel cell stack 5 Fuel cell 5s Cell support 6 Off-gas combustion part 7 Raw fuel supply passage 7p Supply amount control device 8 Reformed water supply passage 8p Supply amount control device 9 Cathode air supply passage 9p Supply amount control device 10 Desulfurizer 11 Reformation air supply passage 11p Supply amount control device 12 Reformed gas supply passage 13 Manifold 14 Exhaust passage 15 Power conditioner (PCS)
16 Load 17 System power supply 18 Heat exchanger 19 Hot water storage tank 20a, 20b Circulation passage 21 Circulation pump 22 Hot water supply passage 23 Water supply passage 30 Control unit 31 Cell temperature sensor

Claims (5)

A reformer that reforms a hydrocarbon-based fuel to produce a hydrogen-rich reformed fuel, and a plurality of solid oxide fuels that generate electricity by an electrochemical reaction between the reformed fuel from the reformer and air A fuel cell stack as an assembly of battery cells, the reformer and the fuel cell stack are surrounded, and excess reformed fuel in the fuel cell stack is burned therein to burn the reformer and the fuel cell. A solid oxide fuel comprising: a module case for maintaining the stack at a high temperature; and a control device for controlling a fuel supply amount to the reformer and an air supply amount to the fuel cell stack based on a target generated power A battery system,
The controller is
A fuel utilization rate and an air utilization rate are set according to the target generated power. When the target generated power is low, the fuel utilization rate and the air utilization rate are set small. A utilization rate basic setting unit for setting a large rate and air utilization rate ;
A temperature detector for detecting a cell temperature of the fuel cell stack;
When the cell temperature exceeds the first predetermined temperature, a utilization rate correction unit that increases the fuel utilization rate and simultaneously reduces the air utilization rate than when normal,
A supply amount calculation unit that calculates a fuel supply amount to the reformer and an air supply amount to the fuel cell stack based on the target generated power, the fuel utilization rate, and the air utilization rate. A solid oxide fuel cell system. The solid oxide fuel cell system according to claim 1 , wherein the target generated power is set to a maximum power that can be generated within the range of the demand power according to the demand power. When the cell temperature falls below the second predetermined temperature after correcting the fuel usage rate and the air usage rate, the usage rate correction unit ends the correction of the fuel usage rate and the air usage rate, 3. The solid oxide fuel cell system according to claim 1 , wherein the control is returned to control. A reformer that reforms a hydrocarbon-based fuel to produce a hydrogen-rich reformed fuel, and a plurality of solid oxide fuels that generate electricity by an electrochemical reaction between the reformed fuel from the reformer and air A fuel cell stack as an assembly of battery cells, the reformer and the fuel cell stack are surrounded, and excess reformed fuel in the fuel cell stack is burned therein to burn the reformer and the fuel cell. A module case for maintaining the stack at a high temperature, and a method for operating the solid oxide fuel cell system,
A fuel usage rate and an air usage rate are set according to the target generated power, and when the target generated power is low, the fuel usage rate and the air usage rate are set small, and as the target generated power increases, the fuel usage rate And while setting the air utilization rate large ,
When the cell temperature of the fuel cell stack is detected and exceeds the first predetermined temperature, in order to suppress deterioration, the fuel utilization rate is increased and the air utilization rate is decreased at the same time as the normal time. And
Solid oxidation, characterized by calculating and controlling a fuel supply amount to the reformer and an air supply amount to the fuel cell stack based on the target generated power and the fuel utilization rate and air utilization rate Operation method of physical fuel cell system. When the cell temperature falls below a second predetermined temperature after correcting the fuel usage rate and the air usage rate, the correction of the fuel usage rate and the air usage rate is terminated and the control is returned to the normal control. The method for operating the solid oxide fuel cell system according to claim 4 .