JP2017162746A - Fuel cell system and method for operating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of improving power generation efficiency of the system with a relatively simple configuration.SOLUTION: A fuel cell system 2 comprises: fuel gas supply means composed of a fuel gas supply source 18, a fuel gas pump 26, and a fuel gas supply line 16; water supply means composed of a water supply source 22, a water pump 34, and a water supply line 20; a reformer 4 for reforming the fuel gas into water vapor; and a fuel battery cell stack 6. A controller 60 includes first fuel utilization setting means for setting a partial load fuel utilization in partial load operation, second fuel utilization setting means for setting a rated load fuel utilization in rated load operation, and rated power generation determining means for determining rated power generation on the basis of power generation current of the fuel battery cell stack. When the fuel battery cell stack enters a rated power generation state, the second fuel utilization setting means sets the rated load fuel utilization on the basis of the rated power generation determination.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system including a fuel cell stack that generates power using fuel gas as fuel, and an operation method thereof.

  In general, a fuel cell system uses a fuel gas supply means for supplying fuel gas, a water supply means for supplying reforming water, and water supplied from the water supply means to steam the fuel gas. A reformer for reforming, a fuel cell stack for generating power by oxidation and reduction of reformed fuel gas and oxidant steam-reformed in the reformer, fuel gas supply means, and water supply means Control means for controlling. In such a fuel cell system (for example, a small fuel cell system for home use), operation control is performed following the power load, and the power generation output of the fuel cell stack is changed according to the magnitude of the power load. In the case of partial load operation, the power generation output of the fuel cell stack is controlled to be a power value obtained by subtracting the power purchase guarantee power from the power load, and this power generation output is controlled by the fuel gas supply means. This is done by controlling the supply flow rate of fuel gas and the supply flow rate of reforming water from the water supply means.

  When controlling the power generation output of the fuel cell stack according to the power load, the fuel gas supply means supplies the fuel gas to a slightly larger amount with a certain margin in preparation for an increase in the power generation output due to an increase in the power load. In other words, the fuel usage rate of the system is controlled so that the fuel usage rate is slightly smaller than the critical fuel usage rate without increasing the fuel usage rate of the system to near the limit. Thus, the occurrence of a shortage of fuel gas due to a sudden increase in generated power is avoided, and damage to the fuel cell stack is prevented in advance.

  However, in such operation, even in rated load operation where the generated power does not increase, fuel gas is supplied to the eyes a little, so the power generation efficiency of the system deteriorates slightly, and the longer the rated power generation state, the higher the power generation efficiency. The bad state continues.

  In order to improve the power generation efficiency of this fuel cell system, for example, one that reuses the reactive fuel gas (including unreacted fuel gas) discharged from the fuel cell stack has been proposed. (For example, refer to Patent Document 1). For example, carbon dioxide contained in the reaction fuel gas discharged from the fuel cell stack is absorbed and removed using an absorbent, and the reaction fuel gas from which carbon dioxide has been removed is recycled and mixed with new fuel gas for power generation. By using it as fuel gas and reusing it in this way, the power generation efficiency of the system is enhanced.

JP 2002-313402 A

  However, the fuel cell system described above requires an absorbent that absorbs carbon dioxide, and it is necessary to provide a recycling flow path for recycling the reaction fuel gas from which carbon dioxide has been absorbed and removed. There are problems such as complexity.

  An object of the present invention is to provide a fuel cell system and a method for operating the fuel cell system that can increase the power generation efficiency of the system with a relatively simple configuration.

The fuel cell system according to claim 1 of the present invention includes a fuel gas supply means for supplying fuel gas, a water supply means for supplying reforming water, and water supplied from the water supply means. A reformer for steam reforming the fuel gas supplied from the fuel gas supply means, and generating power by oxidizing and reducing the reformed fuel gas and the oxidizing material steam reformed by the reformer. A fuel cell stack to be performed, a combustion zone for burning the reaction fuel gas discharged from the fuel cell stack, and a control means for controlling the fuel gas supply means and the water supply means A fuel cell system,
The control means includes first fuel utilization rate setting means for setting a partial load fuel utilization rate in partial load operation based on a relationship between the generated current of the fuel cell stack and a fuel utilization rate, and rated load operation. A second fuel utilization rate setting means for setting a rated load fuel utilization rate, and a rated power generation determination means for determining that the fuel cell stack is in a rated power generation state based on the generated current of the fuel cell stack,
When the fuel cell stack is in a rated power generation state, the second fuel usage rate setting unit sets the rated load fuel usage rate based on the rated power generation determination by the rated power generation determination unit, and the control unit includes the control unit, The fuel gas supply means is controlled so that the rated load fuel utilization rate is larger than the partial load fuel utilization rate.

  Further, in the fuel cell system according to claim 2 of the present invention, the control means further sets an S / C setting for setting an S / C of the reformed fuel gas supplied to the fuel cell stack. And the S / C setting means sets the S / C based on an S / C-stack temperature characteristic indicating a relationship between the S / C and the stack temperature of the fuel cell stack, and the fuel cell When the stack is in a rated power generation state, the control means controls the water supply means so as to have a value smaller than the S / C value in the S / C-stack temperature characteristic.

Further, the operation method of the fuel cell system according to claim 3 of the present invention includes a fuel gas supply means for supplying fuel gas, a water supply means for supplying reforming water, and the water supply means. A reformer for steam reforming the fuel gas supplied from the fuel gas supply means using the supplied water, and oxidation of the reformed fuel gas and the oxidizing material steam-reformed by the reformer And a method of operating a fuel cell system comprising: a fuel cell stack that generates power by reduction; and a combustion zone for combusting a reaction fuel gas discharged from the fuel cell stack,
When the fuel cell stack is in a partial load power generation state, the fuel gas supply means is controlled to achieve a partial load fuel usage rate set based on the relationship between the power generation current of the fuel cell stack and the fuel usage rate. In addition, when the fuel cell stack is in the rated power generation state, the fuel gas supply means is controlled so that the rated load fuel usage rate is larger than the partial load fuel usage rate.

  According to the fuel cell system according to claim 1 and the operation method of the fuel cell system according to claim 3, when the fuel cell stack is in the partial load power generation state, the generated current and fuel of the fuel cell stack The fuel gas supply means is controlled so that a partial load fuel utilization rate set based on the relationship with the utilization factor is obtained, and when the fuel cell stack is in the rated power generation state, a value larger than the partial load fuel utilization factor is obtained. Since the fuel gas supply means is controlled to achieve the rated load fuel utilization rate, the power generation efficiency of the system in this rated load operation can be increased.

  In the rated power generation state of the fuel cell stack, it is not operated substantially exceeding the rated power generation. Therefore, it is not necessary to supply the fuel gas to a few more eyes, and in the partial load power generation state It is possible to make the fuel utilization rate (that is, the rated load fuel utilization rate) in the rated power generation state larger than the fuel utilization rate (that is, the partial load fuel utilization rate). From this point of view, when the rated power generation state is reached, the partial load fuel usage rate is changed to the rated load fuel usage rate to increase the fuel usage rate and perform power generation operation. This fuel utilization rate is the ratio of the fuel gas that contributes to power generation in the fuel gas supplied to the fuel cell stack. When this fuel utilization rate increases, more fuel gas is consumed in the power generation reaction, resulting in waste. As a result, the power generation efficiency of the fuel cell stack increases.

  Since the fuel utilization rate is increased in this way in the rated power generation state, it is possible to improve the power generation efficiency of the fuel cell stack, and the effect of improving the power generation efficiency is such that the rated power generation state continues for a long time. growing.

  According to the fuel cell system of claim 2 of the present invention, when the fuel cell stack is in the rated power generation state, the water cell is set to a value smaller than the S / C value in the S / C-stack temperature characteristic. Since the supply means is controlled, the water component (water vapor) delivered to the fuel cell stack is reduced, and the decrease in the stack temperature of the fuel cell stack due to the increased fuel utilization rate is suppressed to the desired stack temperature. Can be maintained.

  S / C is the molar ratio (steam / carbon ratio) between water vapor added during the reaction and carbon contained in the fuel gas (hydrocarbon gas). The amount of water vapor is reduced and the stack temperature of the fuel cell stack rises.

1 is a simplified diagram showing one embodiment of a fuel cell system according to the present invention. The block diagram which shows the control system of the fuel cell system of FIG. The flowchart which shows the flow of control by the control system of FIG. The figure which shows the relationship between the electric power generation current in the fuel cell system of FIG. 1, a limit fuel utilization factor, and the control fuel utilization factor. The figure for demonstrating the change of an electric power generation current when it will be in a rated electric power generation state and a fuel utilization rate is raised. The figure for demonstrating the rated electric power generation state when a fuel cell stack deteriorates. The figure which shows the relationship between the fuel usage rate of a fuel cell stack, and stack temperature. The figure which shows the relationship between S / C of the fuel gas supplied to a fuel cell stack, and stack temperature. The figure which shows the relationship between the electric power generation current in the conventional fuel cell system, a limit fuel utilization factor, and the control fuel utilization factor.

  Hereinafter, an embodiment of a fuel cell system and an operation method thereof according to the present invention will be described with reference to the accompanying drawings.

  In FIG. 1, a fuel cell system 2 shown in FIG. 1 uses a hydrocarbon fuel gas, for example, natural gas (city gas) as fuel gas to generate power, and reforms for reforming the fuel gas. , A fuel cell stack 6 that generates power by oxidizing and reducing the fuel gas (reformed fuel gas) reformed in the reformer 4 and air as an oxidant, and the fuel cell stack 6 And air blowing means 8 for feeding to the

  The fuel cell stack 6 is made of, for example, a solid oxide type, and a plurality of fuel cells for generating power by a fuel cell reaction are stacked via a current collecting member. For example, zirconia doped with yttria is used as the solid electrolyte, which includes a solid electrolyte that conducts heat, a fuel electrode provided on one side of the solid electrolyte, and an oxygen electrode provided on the other side of the solid electrolyte.

  The fuel cell introduction side of the fuel cell stack 6 is connected to the reformer 4 via the reformed fuel gas feed line 10, and the reformer 4 is vaporized via the gas / steam feed line 12. The vaporizer 14 is connected to a fuel gas supply source 18 (for example, a buried pipe or a storage tank) for supplying fuel gas via a fuel gas supply line 16 and water. A water supply source 22 (for example, a water tank) is connected via a supply line 20. The reformer 4 includes a reforming catalyst in which ruthenium is supported on alumina, for example, and steam reforms the fuel gas with the reforming catalyst. The vaporizer 14 vaporizes water fed through the water supply line 20 to generate water vapor. Note that the reformer 4 and the vaporizer 14 can be integrally formed.

  In the fuel gas supply line 16, a desulfurizer 24, a fuel gas pump 26, a fuel gas flow rate detection sensor 28, and a shutoff valve 30 are disposed. The desulfurizer 24 removes sulfur components contained in the fuel gas, the fuel gas pump 26 supplies the fuel gas from the fuel gas supply source 18 to the vaporizer 14 through the fuel gas supply line 16, and the fuel gas flow rate detection sensor 28 The flow rate of the fuel gas supplied through the fuel gas supply line 16 is detected, and the shutoff valve 30 opens and closes the fuel gas supply line 16 to supply and stop the fuel gas. In this embodiment, the supply flow rate of the fuel gas supplied through the fuel gas supply line 16 is controlled by controlling the rotational speed of the fuel gas pump 26, and when the rotational speed increases (or decreases), The supply flow rate increases (or decreases), and the fuel gas supply source 18, the fuel gas pump 26, and the fuel gas supply line 16 constitute fuel gas supply means.

  The water supply line 20 is provided with a water pump 34 and a water flow rate detection sensor 35 (water flow rate detection means). The water pump 34 supplies water from the water supply source 22 to the vaporizer 14. The water flow rate detection sensor 35 detects the flow rate of the reforming water supplied through the water supply line 20. In this embodiment, the supply flow rate of the reforming water supplied through the water supply line 20 is controlled by controlling the rotation speed of the water pump 34, and the reforming water is increased when the rotation speed is increased (or decreased). The water supply source 22, the water pump 34, and the water supply line 20 constitute a water supply means.

  An oxygen electrode introduction side of the fuel cell stack 6 is connected to an air preheater 38 for preheating air (oxidant) via an air supply line 36, and the air preheater 38 is connected to an air supply line. 40 is connected to the air blowing means 8. The blower unit 8 is composed of, for example, a blower blower, and by controlling the rotational speed of the blower blower, the amount of air supplied through the air supply line 40 is controlled, and the rotational speed of the blower blower increases ( Or the air supply flow rate of the air supplied through the air supply line 40 increases (or decreases), and the air supply means 8 (air blower) and the air supply line 40 become the air supply means (oxidant supply means). Configure.

  A combustion zone 44 is provided on each discharge side of the fuel electrode and the oxygen electrode of the fuel cell stack 6, and the reaction fuel gas (including surplus fuel gas) discharged from one end of the fuel cell stack 6. Air (containing oxygen) discharged from the oxygen electrode side is supplied to the combustion zone 44 and burned. The combustion zone 44 is connected to an air preheater 38 via an exhaust gas supply line 46, and exhaust gas flowing through the air preheater 38 is discharged to the atmosphere via an exhaust gas discharge line 48. In the air preheater 38, heat exchange is performed between the air flowing through the air supply line 40 and the exhaust gas flowing through the exhaust gas supply line 46, and the air heated by this heat exchange is the air supply line 36. To the fuel cell stack 6.

  In this embodiment, a stack temperature detection sensor 50 is disposed in association with the fuel cell stack 6, and the stack temperature detection sensor 50 is disposed in the vicinity of the fuel cell stack 6. Detect temperature. In addition, a power generation current detection sensor 52 (see FIG. 2) is disposed in a power output portion (not shown) of the fuel cell stack 6, and the power generation current detection sensor 52 is a power generation current from the fuel cell stack 6. Is detected.

  In this embodiment, the reformer 4, the fuel cell stack 6, the carburetor 14, and the air preheater 38 are accommodated in the battery accommodating housing 54, and the inner surface of the battery accommodating housing 54 is covered with a heat insulating material. Thus, the high temperature chamber 56 is configured, and the reformer 4, the fuel cell stack 6, the vaporizer 14, and the air preheater 38 are kept in a high temperature state in the high temperature chamber 56.

  For example, the fuel cell system 2 operates as follows to generate electric power. Fuel gas (eg, city gas) from the fuel gas supply source 18 is supplied to the vaporizer 14 through the fuel gas supply line 16, and water from the water supply source 22 is supplied to the vaporizer 14 through the water supply line 20. Is done. In the vaporizer 14, water is heated to become steam, and the heated fuel gas and the generated steam are mixed and fed to the reformer 4 via the gas / steam feed line 12.

  In the reformer 4, a steam reforming reaction is performed with the fuel gas and the steam, and the steam-reformed fuel gas (reformed fuel gas) passes through the reformed fuel gas supply line 10 in the fuel cell stack 6. It is fed to the fuel electrode side. The air from the blower 8 is supplied to the air preheater 38 through the air supply line 40, and heat exchange is performed between the air preheater 38 and the exhaust gas flowing from the combustion zone 44 through the exhaust gas supply line 46. After being heated, the air is supplied to the oxygen electrode side of the fuel cell stack 6 through the air supply line 36.

  The fuel electrode side of the fuel cell stack 6 oxidizes the reformed fuel gas, and the oxygen electrode side reduces oxygen in the air, by an electrochemical reaction due to oxidation on the fuel electrode side and reduction on the oxygen electrode side. Power generation is performed. The reaction fuel gas and air discharged from one end of the fuel cell stack 6 are sent to the combustion zone 44 and burned, and the reformer 4 and the vaporizer 14 are heated by using the combustion heat of the reaction fuel gas. Is done. The exhaust gas from the combustion zone 44 is supplied to the air preheater 38 through the exhaust gas supply line 46 and is used for heat exchange with the air supplied from the blowing means 8 in the air preheater 38, and then the exhaust gas. It is discharged to the atmosphere through the discharge line 48.

  The fuel cell system 2 further includes a controller 60 for controlling the operation of the fuel gas pump 28, the water pump 34, and the air blowing means 8. 2, in this embodiment, the controller 60 includes a first fuel utilization rate setting unit 62, a second fuel utilization rate setting unit 64, a rated power generation determination unit 66, an S / C setting unit 68, Operation control means 70 and memory means 72 are provided. The first fuel usage rate setting means 62 sets the fuel usage rate during partial load operation (partial load fuel usage rate) as described later, and the second fuel usage rate setting means 64 sets the fuel usage rate during rated load operation. (Rated load fuel utilization rate) is set as described later, the rated power generation determination means 66 determines rated power generation as described later based on the detection signal from the generated current detection sensor 52, and the S / C setting means 68 S / C is set as will be described later. The operation control means 70 controls the operation of the fuel pump 26, the water pump 34, and the like as will be described later. The memory means 72 serves as a base for setting a power generation current-fuel utilization ratio characteristic map, a fuel utilization ratio at the rated load, and an S / C as a base when setting the fuel utilization ratio during partial load operation. An S / C-stack temperature characteristic map and the like are registered.

  From the fuel gas flow detection sensor 28 (fuel gas flow detection means), the water flow detection sensor 35 (water flow detection means), the stack temperature detection sensor 50 (stack temperature detection means) and the generated current detection sensor 52 (generated current detection means). These detection signals are sent to the controller 60, and based on these detection signals, the controller 60 controls the operation of the fuel gas pump 26, the water pump 34 and the air blowing means 8 as follows.

  Referring mainly to FIGS. 2 and 3, when the fuel cell system 2 is operated for power generation, the fuel cell stack 6 generates power as described above. In this power generation operation, first, partial load operation is performed (step S1), and then the load shifts to rated load operation when the power load increases.

  In this partial load operation, the generated current detection sensor 52 detects the generated current from the fuel cell stack 6 (step S2), and the first fuel utilization rate setting means 62 detects the detection signal of the generated current detection sensor 52. Based on the above, the fuel utilization rate in the partial load operation is set (step S3). A power generation current-fuel utilization rate characteristic map as shown in FIG. 4 is registered in the memory means 72. In this power generation current-fuel utilization ratio characteristic map, the fuel utilization rate increases as the power generation current increases. Thus, the first fuel utilization rate setting means 62 sets the partial load fuel utilization rate using this generated current-fuel utilization rate characteristic map. .

  Therefore, in this partial load operation, the fuel utilization is changed and set as shown by the solid line in FIG. 4 in relation to the generated current of the fuel cell stack 6, and the operation control means 70 is set in this way. Then, the fuel gas pump 26 and the water pump 34 are controlled to achieve the partial load fuel utilization rate, and the power generation operation is performed (at this time, the blowing unit 8 is also controlled so that a necessary amount of air is supplied). In this partial load operation, when an operation for stopping power generation is performed, the process proceeds from step S4 to step S5 through step S6, and the power generation operation is completed.

  In such partial load operation, when the power generation output of the fuel cell stack 6 rises and the detection signal from the power generation current detection sensor 52 reaches the rated power generation current, that is, the rated power generation state is reached, the process proceeds from step S4 to step S7. The rated power generation determination unit 66 determines the rated power generation assuming that the rated power generation state has been reached, and the rated power generation operation is performed based on the determination result (step S8).

  When the operation moves to the rated power generation operation in this way, the generated current detection sensor 52 detects the generated current of the fuel cell stack 6 (step S9), and if the rated power generation state of the fuel cell stack 6 is maintained, the second The fuel usage rate setting means 64 sets the rated load fuel usage rate registered in the memory means 72 (step S10). The rated load fuel utilization rate is set to a value lower by, for example, about 5% than the limit fuel utilization rate, and the operation control means 70 controls the fuel gas pump 26 and the water pump 34 so as to achieve this rated load fuel utilization rate. The power generation operation is performed (at this time, the blowing unit 8 is also controlled so that a necessary amount of air is supplied).

  The setting of the fuel utilization rate in the conventional fuel cell system is performed using the generated current-fuel utilization rate characteristic map shown in FIG. 9, and is 10 to 20% lower than the limit fuel utilization rate even in the rated power generation state ( For example, the power generation operation is performed at a fuel utilization rate of about 75%. On the other hand, the setting of the fuel utilization rate in this embodiment is performed as shown in FIG. 4, and when the fuel cell stack 6 is in the rated power generation state, the rated load fuel utilization rate larger than the conventional fuel utilization rate. (For example, fuel utilization rate: about 80%) is set, and the fuel consumption rate is continuously increased as indicated by “●-●” in FIG. 4 so as to reach this rated load fuel utilization rate. Then, after reaching the rated fuel utilization rate, it is maintained at a value that is, for example, about 5% larger than the rated fuel utilization rate, that is, the fuel utilization rate in the conventional rated power generation state.

  When the fuel utilization rate is increased in this way, the proportion of the fuel gas supplied from the fuel gas supply means that contributes to power generation in the fuel cell stack 6 increases, and as a result, the power generation efficiency of the fuel cell system can be improved. it can.

  In the partial load operation of the fuel cell stack 6, if the fuel utilization rate is increased in this way, it cannot be handled when the power generation output of the fuel cell stack 6 increases, and there is a possibility that a fuel gas shortage may occur. However, in the rated power generation state, the power generation output does not substantially increase, and it is not necessary to consider such a power generation output increase. Accordingly, there is no inconvenience caused by increasing the fuel utilization rate in this way, and only the merit of improving the power generation efficiency by increasing the fuel utilization rate can be obtained.

  After the rated load fuel utilization rate is set in this way, the S / C setting means 68 changes the S / C of the reformed fuel gas supplied to the fuel cell stack 6 (step S11). In the power generation operation of the fuel cell stack 6, the relationship between the fuel utilization rate and the temperature of the fuel cell stack 6 (stack temperature) changes as shown in the fuel utilization rate-stack temperature characteristic of FIG. When (or becomes smaller), the ratio of the fuel gas that contributes to power generation in the fuel cell stack 6 decreases (or increases) and the stack temperature decreases (or increases). Further, the relationship between the S / C and the stack temperature changes as shown in the S / C-stack temperature characteristic of FIG. 8, and when the S / C increases (or decreases), it is included in the reformed fuel gas. Moisture (water vapor) increases (or decreases), and the stack temperature decreases (or increases).

  The temperature, fuel utilization rate, and S / C of the fuel cell stack 6 are in the relationship shown in FIG. 7 and FIG. 8, and therefore, when the fuel utilization rate is increased as described above in rated load operation, it can be understood from FIG. As described above, when the temperature of the fuel cell stack 6 is lowered, and the stack temperature is lowered in this way, the power generation voltage of the fuel cell stack 6 is generally lowered. In order to maintain the output of the fuel cell stack 6, the generated current increases as indicated by “●-●” in FIG. 5, and the amount of fuel gas supplied increases. As a result, the above-described increase in power generation efficiency is offset and the desired effect cannot be obtained.

  For this reason, when the fuel cell stack 6 is in the rated load operation (that is, in the rated power generation state), the S / C setting unit 68 sets the S / C-S / C setting temperature 68 based on the S / C-stack temperature characteristic shown in FIG. It sets so that it may become a value (for example, 1.5-2.4) smaller than C value (for example, 2.4-3.0). When the fuel utilization rate is increased in the rated load operation as described above, the fuel gas that does not contribute to power generation decreases and the stack temperature tends to decrease. In this way, the S / C value is lowered to the reformed fuel gas. By reducing the water content, the tendency of the stack temperature to decrease can be suppressed, and thereby the decrease in the generated voltage and the increase in the generated current of the fuel cell stack 6 can be suppressed.

  As described above, in the rated load operation, the fuel utilization rate is set to be higher than that in the partial load operation, and accordingly, the S / C value is set to be small. The power generation operation of the battery system 2 is performed. Even in this rated load operation, the generated current of the fuel cell stack 6 is continuously detected by the generated current detection sensor 52 (step S9). When this detected current falls from the rated generated current value, the process returns to step S1. Thus, the partial load operation of the fuel cell system 2 is performed. In this rated load operation, if an operation for stopping power generation is performed, the process proceeds from step S12 to step S13 through step S13, and the power generation operation is terminated.

  The fuel cell system 2 is operated for power generation as described above. When this power generation operation is performed for a long period of time, the deterioration of the fuel cell stack 6 proceeds. As shown in FIG. 6, in the initial installation of the fuel cell system 2 (initial state of start of use), there is no deterioration of the fuel cell stack 6, and as shown by the thick solid line in FIG. When the power generation state is entered, the current value in the rated power generation state increases as it operates for a long time, and the current value gradually increases. As shown by the thin solid line in FIG. 6, the current value is larger than the initial current value. Therefore, the rated power generation state is set, and the rated generation current is described in this specification including the rated equivalent current value in such a rated power generation state.

  As mentioned above, although one embodiment of the fuel cell system and the operation method thereof according to the present invention has been described, the present invention is not limited to such an embodiment, and various changes or modifications can be made without departing from the scope of the present invention. Is possible.

  For example, in the above-described embodiment, a water tank or the like is used as the water supply source 22. However, instead of such a configuration, water contained in the exhaust gas discharged through the exhaust gas discharge line 48 is condensed to water. The water recovered in the recovery tank and recovered in the water recovery tank can be used as the reforming water.

  Further, for example, it can be used in combination with a hot water storage device having a hot water storage tank for storing the heat of exhaust gas as hot water. For example, a heat exchanger is provided in the exhaust gas discharge line 48, and heat exchange is performed between the exhaust gas flowing through the exhaust gas discharge line 48 and the water from the hot water storage tank in this heat exchanger. You may make it store the warm water heated in the hot water storage tank.

DESCRIPTION OF SYMBOLS 2 Fuel cell system 4 Reformer 6 Fuel cell stack 8 Blowing means 14 Vaporizer 18 Fuel gas supply source 22 Water supply source 26 Fuel gas pump 28 Fuel gas flow rate detection sensor 34 Water pump 35 Water flow rate detection sensor 44 Combustion zone 50 Stack Temperature detection sensor 52 Generated current detection sensor 60 Controller 62 First fuel utilization rate setting means 64 Second fuel utilization rate setting means 66 Rated power generation determination means 68 S / C setting means 70 Operation control means

Claims (3)

Fuel gas supply means for supplying fuel gas, water supply means for supplying reforming water, and fuel gas supplied from the fuel gas supply means using water supplied from the water supply means A reformer for steam reforming, a fuel cell stack for generating power by oxidation and reduction of reformed fuel gas and oxidant steam reformed by the reformer, and exhausted from the fuel cell stack A fuel cell system comprising: a combustion area for burning the reacted fuel gas; and a control means for controlling the fuel gas supply means and the water supply means,
The control means includes first fuel utilization rate setting means for setting a partial load fuel utilization rate in partial load operation based on a relationship between the generated current of the fuel cell stack and a fuel utilization rate, and rated load operation. A second fuel utilization rate setting means for setting a rated load fuel utilization rate, and a rated power generation determination means for determining the rated power generation based on the generated current of the fuel cell stack,
When the fuel cell stack is in a rated power generation state, the second fuel usage rate setting unit sets the rated load fuel usage rate based on the rated power generation determination by the rated power generation determination unit, and the control unit includes the part A fuel cell system, wherein the fuel gas supply means is controlled so that the rated load fuel utilization rate is larger than a load fuel utilization rate.   The control means further includes S / C setting means for setting S / C of the reformed fuel gas supplied to the fuel cell stack, and the S / C setting means includes S / C and When the S / C is set based on the S / C-stack temperature characteristic indicating the relationship with the stack temperature of the fuel cell stack, and the fuel cell stack is in the rated power generation state, the control means 2. The fuel cell system according to claim 1, wherein the water supply unit is controlled to have a value smaller than an S / C value of a rated power generation state in a C-stack temperature characteristic. Fuel gas supply means for supplying fuel gas, water supply means for supplying reforming water, and fuel gas supplied from the fuel gas supply means using water supplied from the water supply means A reformer for steam reforming, a fuel cell stack for generating power by oxidation and reduction of reformed fuel gas and oxidant steam reformed by the reformer, and exhausted from the fuel cell stack A combustion zone for burning the reacted fuel gas, and a method of operating a fuel cell system comprising:
When performing partial load operation of the fuel cell stack, the fuel gas supply means is controlled so that the partial load fuel utilization is set based on the relationship between the generated current of the fuel cell stack and the fuel utilization, When the fuel cell stack is operated at a rated load, the fuel gas supply means is controlled so that the rated load fuel usage rate is larger than the partial load fuel usage rate. how to drive.

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