JPH07302603A - Fuel cell power generating system and its operating method - Google Patents

Abstract

PURPOSE:To provide a fuel cell power generating system with no uneven flow rate distribution and temperature distribution in the direction of cell stacking on partial load operation. CONSTITUTION:A controller 55 operates compressors 304, 306, 308, 324, and pressure control valves 401-406 to control gas pressure so that volume flow rates of a fuel gas and an oxidizing gas in a fuel cell 20 become always constant. The controller 55 also operates a compressor 343 and a pressure control valve 407 to vary the pressure inside a pressure container 21 according to a load. Even on partial load operation, dispersion in performance between cells can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generation system capable of exhibiting uniform cell performance in the stacking direction by adjusting the operating pressure according to the load during partial load power generation, and a method of operating the same.

[0002]

2. Description of the Related Art Fuel cells have been attracting attention due to their high power generation efficiency, cleanliness and the like, and have been continuously developed. A fuel cell is considered to be used in a manner that complements thermal power generation and nuclear power generation, and appropriately changes the amount of power generation to cope with load fluctuations. In order to enable such a usage pattern, it is necessary to be able to sufficiently cope with not only the rated load but also the partial load operation. However, since the fuel cell has a laminated structure, when the partial load operation is performed, the flow rate of the fuel (and oxidant) gas, the temperature distribution, and the heat generation amount become nonuniform in the cell stacking direction. There is a problem that the deterioration of the battery is accelerated. Hereinafter, the details of the problem will be described.

The standard flow rates of the fuel gas and the oxidant gas required for the electrochemical reaction differ depending on the magnitude of the load. In partial load operation, the required standard flow rates of fuel gas and oxidant gas are smaller than in full load. Therefore, when operating at the same pressure at full load as at full load, the actual flow rate of the supply gas decreases. And when this actual flow rate fluctuates,
The flow path resistance flowing through the flow path also changes. Then, this makes the flow rate distribution in the stacking direction non-uniform.

Further, since the fuel gas and the oxidant gas are consumed by the electrochemical reaction, their gas composition changes at the inlet and outlet of the fuel cell. Along with this, naturally, physical properties such as the density and viscosity of the gas also change. Even if such a density difference occurs, the flow rate distribution in the stacking direction should not be non-uniform unless it is affected by gravity (see FIG. 8).
However, in reality, gravity affects the flow rate distribution in the stacking direction of the unit cells to be non-uniform (see FIG. 9). This non-uniformity becomes remarkable as the number of stacked unit cells increases. Such non-uniformity of the flow distribution is particularly remarkable in the fuel gas system.

In order to solve such a problem, various methods for operating a fuel cell under a partial load have been conventionally proposed.

For example, Japanese Patent Laid-Open No. 59-75571 discloses that
There has been proposed an operating method for improving the overall power generation efficiency of a fuel cell power generation system under partial load by making the operating pressure under partial load lower than the operating pressure under full load.

Further, Japanese Patent Application Laid-Open No. 60-10566 proposes an operating method in which the gas pressure is increased / decreased when the load fluctuates to maintain the voltage below a voltage at which deterioration does not occur and to generate electric power.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the fuel cell operating method disclosed in Japanese Patent No. 75571,
Although it is possible to improve the efficiency of the system as a whole, the efficiency of all parts is not always the maximum value. In other words, there was room for further improvement in power generation efficiency (in other words, power generation loss).

In the operating method disclosed in Japanese Patent Application Laid-Open No. 60-10566, the pressure of only the fuel gas and the oxidant gas is increased / decreased and the pressure of the filling gas in the pressure vessel is adjusted according to the increase / decrease of the load. That is not taken into account. for that reason,
In the case of the internal manifold type fuel cell stack, there is a possibility that the seal portion around the cell may be damaged by the pressure difference between the pressure of the filling gas in the pressure vessel and the pressure in the fuel cell stack.

Another problem is that the temperature distribution of the battery body becomes non-uniform during partial load operation. The cause of this is the non-uniformity of the flow rate of the oxidant gas. In a fuel cell, particularly in a molten carbon dioxide fuel cell, the oxidant gas usually also plays a role as a cooling gas for the cell. The non-uniform flow distribution of the oxidant gas means that the cooling capacity is different for each part. In an actual fuel cell, an oxidant gas or the like is supplied from the lower side of the cell stack and discharged from the upper side in many cases. Therefore, the battery stack tends to have a lower temperature during the partial load operation. Further, the filling gas in the pressure vessel moves by thermal convection in the pressure vessel. As a result, a relatively low temperature filling gas tends to accumulate in the lower side of the pressure vessel, and a relatively high temperature filling gas tends to accumulate in the upper side. And
In such a situation, cooling of the lower portion of the battery stack has been further promoted.

It is an object of the present invention to provide a fuel cell power generation system and a method of operating the same, in which a decrease in power generation efficiency in a partial load operation, a non-uniform temperature and the like are suppressed to a minimum.

An object of the present invention is to obtain a cell stacking direction,
It is to provide a fuel cell power generation system and a method of operating the same, in which the flow rate distribution of the fuel gas and the oxidant gas and the temperature distribution are made uniform.

[0013]

A method of operating a fuel cell according to the present invention is designed so that, during partial load operation, the load is changed according to the load.
The operating pressure of the auxiliary system is adjusted so that its efficiency is maximized, and the actual flow rate of the pressure vessel is the same as at full load. Also, the operating pressure is adjusted so that the temperature distribution in the stacking direction in the container does not become larger than that at full load.

More specifically, it is as follows.

As a first aspect of the present invention, in a method of operating a fuel cell power generation system in which a fuel cell is installed in a pressure vessel, a fuel gas and an oxidizer to be supplied to the fuel cell according to the magnitude of load. There is provided a method of operating a fuel cell power generation system, characterized in that the pressure of a gas and a filling gas with which the pressure vessel is filled is changed.

It is preferable that the pressures of the fuel gas and the oxidant gas are changed so as to reduce the fluctuation range of the actual volumetric flow rate of the gas. It is more preferable to change the pressure so that the volumetric flow rate is maintained at a predetermined constant value. The predetermined constant value is preferably a volume flow rate when the fuel cell is fully loaded.

The pressure of the filling gas is changed such that the difference between the pressure of the filling gas and the pressure of the fuel gas and the pressure of the oxidant gas falls within a predetermined range. It is preferable. It is more preferable that the predetermined range is determined based on the mechanical strength of the fuel cell. The pressure of the filling gas may be kept at the lower limit of the predetermined range.

As a second aspect of the present invention, in the method for operating a fuel cell power generation system, the pressures of the fuel gas and the oxidant gas in the fuel cell are supplied, and the fuel gas and the oxidant gas are supplied to the fuel cell. To control these gases independently of the pressure of these gases in the
A method of operating a fuel cell power generation system is provided.

The pressure control is to control the pressures of the fuel gas and the oxidant gas in the fuel cell so that the flow rates of the fuel gas and the oxidant gas become a predetermined constant value. It is preferable.

According to a third aspect of the present invention, 1 or 2
A fuel cell including the above unit cell, supply of fuel gas and oxidant gas to the fuel cell, and / or
Alternatively, an auxiliary device for discharging gas from the fuel cell, and a pressure control means capable of controlling the pressures of the fuel gas and the oxidant gas in the fuel cell independently of the pressure in the auxiliary device. And a fuel cell power generation system.

A pressure vessel is provided, the fuel cell is installed in the pressure vessel, and the pressure control means can control the pressure in the pressure vessel independently of the pressure in the auxiliary equipment. It is preferable that it is

It is more preferable that the pressure control means controls the pressure so that the actual volumetric flow rates of the fuel gas and the oxidant gas are maintained at a certain constant value. The constant value is preferably a volume flow rate of the fuel cell in a full load operation state.

The pressure control means includes a load, pressures of the fuel gas and the oxidant gas supplied to the fuel gas,
Storage means for storing control data indicating the correspondence relationship between the fuel gas and the oxidant gas, the pressure value of the fuel gas and the oxidant gas being associated with the value of the load are obtained by referring to the control data. It is preferable to control the pressures of the fuel gas and the oxidant gas so that

A pressure vessel is provided, the fuel cell is installed in the pressure vessel, the control data further includes a correspondence relationship between the load and the pressure of the filling gas, and the pressure control means. It is preferable that the pressure in the pressure vessel can be controlled independently of the pressure in the auxiliary machine according to the control data.

The pressure control means may include a compressor arranged between the auxiliary machine and the fuel cell.

[0026]

The pressure control means operates the compressor and the like while referring to the control data to change the pressures of the fuel gas, the oxidant gas and the filling gas in accordance with the magnitude of the load. Changing the pressures of the fuel gas and the oxidant gas reduces the fluctuation range of the actual volume flow rate (actual flow rate) of the gas, and changes the volume flow rate to a predetermined constant value (for example, when the fuel cell is fully loaded It is performed so that the volume flow rate value in the applied state is maintained. The pressure of the filling gas is changed such that the difference between the pressure of the filling gas and the pressures of the fuel gas and the oxidant gas is within a predetermined range (for example, a range determined based on mechanical strength). In, keep at the lower limit.

The pressure control of the fuel gas, the oxidant gas and the filling gas is performed independently of the pressure in the auxiliary equipment.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the drawings.

The greatest feature of the fuel cell power generation system of this embodiment is that the actual flow rates of the fuel gas and the oxidant gas are always the same as at full load regardless of the size of the load. To do. Further, the pressure inside the pressure vessel is also changed according to the magnitude of the load. Therefore, in the following description, the characteristic points will be mainly described. In the present specification, the “actual flow rate” means the flow rate (volume) at the actual temperature and pressure at that time. On the other hand, the "standard flow rate" means a volume flow rate (or a gas corresponding to the mass thereof) when converted into a standard state (0 ° C, 1 atm).

The fuel cell power generation system of this embodiment is shown in FIG.
As shown in FIG.
And a gas supply system 3 for supplying gas to the battery stack 20, a gas discharge system 4 for discharging gas, and a control system 5 for controlling the whole. It is configured. Hereinafter, the gas supply system 3 and the gas discharge system 4 may be collectively referred to as “auxiliary equipment” and “auxiliary equipment”.

The battery stack 20, as shown in FIG.
Stacked cell group 11 configured by stacking a plurality of unit batteries 8
And a gas header (for fuel gas and oxidant gas) 12 for supplying and exhausting gas to and from the stacked cell group 11.
It is composed of and.

The unit battery 8 is composed of an electrolyte substrate 81, an anode 82, a cathode 83, a current collector plate 84, and a separator 85.

The anode 82 and the cathode 83 are arranged so as to sandwich the electrolyte substrate 81. Further, a current collector plate 84 and a separator 85 are arranged further outside thereof. On the back surface of the anode 82, a cell flow passage 820 for circulating the fuel gas is provided. On the other hand, on the back surface of the cathode 83, a cell flow channel 83 for circulating an oxidant gas is provided.
0 is provided. The cell channels 820 and 830 are formed by forming a plurality of grooves in parallel with each other in the separator 85 adjacent to the electrodes 82 and 83 (with the current collector plate 84 interposed therebetween). The separator 85 and the electrolyte substrate 1 are each provided with a manifold 86 for passing a fuel gas and an oxidant gas.

The gas header 12a is provided with a fuel gas inlet 13a and an oxidant gas inlet 14a.
On the other hand, the gas header 12b has a fuel gas outlet port 13
b, an oxidant gas outlet 14b is provided. The fuel gas flowing into the inflow port 13a is supplied to the manifold 8
6 to be supplied to each unit battery 8 (cell flow channel 82
0 is passed). And then, again the manifold 8
6 is configured to be discharged from the discharge port 13b to the outside of the battery stack. Similarly for the oxidant gas, the inlet 1
4a, manifold 86, unit battery 8 (cell flow path 83
0), the manifold 86, and the discharge port 14b. It goes without saying that the flow paths for the oxidant gas and the fuel gas are configured independently of each other.

The battery stack 20 is basically
The flow channel shapes and dimensions of the cell flow channels 20, 830, the manifold 86, etc. are determined so that the flow rate distribution in the stacking direction is uniform under the flow conditions at the rated load (full load) and the rated pressure.

Although not shown in FIG. 2, the battery stack 2
The surface pressure applied to 0 is adjusted by the stack tightening bellows 22.

In the present specification, the "flow channel" is a concept that includes both the cell flow channel 830 and the manifold 86 for the oxidant gas for the oxidant gas. Regarding the fuel gas, the concept includes both the cell flow path 820 and the fuel gas manifold 86.

The gas supply system 3 includes a fuel gas supply system 30, an oxidant gas supply system 32, and a pressure vessel filling gas supply system 34.
It ’s parting.

The fuel gas supply system 30 is for supplying fuel gas to the cell stack 20. In the present embodiment, as the fuel gas, hydrogen gas is used directly, or a reformed city gas can be used. The fuel gas supply system 30 includes a hydrogen loader 301 and a flow rate controller 3
03, reformer 305, steam generator 307, preheater 309
Is equipped with. The flow rate controller 303 is for adjusting the standard flow rates of hydrogen and carbon dioxide according to an instruction from the control unit 55. Reformer 305, steam generator 307
Since these are already well known, the description is omitted.

The fuel gas supply system 30 of this embodiment further includes a flow rate controller 303, a reformer 305, and a steam generator 30.
7. Compressors 304, 306, and 308 are provided on the rear side of each and the front side of the preheater 309. By means of the compressors 304, 306, 308 and the pressure control valves 401-403 described later, during this period (compressors 304, 30
6, 308 and the pressure control valves 401 to 403), the pressure of the fuel gas is set to the front and rear portions (compressors 304, 306,
The pressure is configured to be adjustable independently of the pressure of the upstream side of 308 and the downstream side of the pressure adjusting valves 401 to 403. On the other hand, the pressures in the reformer 305 and the steam generator 307 are adjustable by themselves. The compressor 304 and the like operate according to an instruction from the control unit 55.

The oxidant gas supply system 32 is for supplying an oxidant gas (air in this embodiment) to the battery stack 20. The oxidant gas supply system 32 is used for the air compressor 3
21, a carbon dioxide gas tank 322, a flow rate controller 323, and a preheater 324 are provided. The flow rate controller 323 is the controller 5
It is for adjusting the standard flow rates of air and carbon dioxide gas according to the instructions from 5. Since the preheater 324 and the like are already well known, detailed description thereof will be omitted.

The oxidizing gas supply system 32 of this embodiment further includes a compressor 324 between the flow rate controller 323 and the preheater 325. By means of the compressor 324 and pressure control valves 404 to 406 which will be described later, during this period (compressor 3
24 and the pressure control valves 404 to 406) independently of the pressure of the oxidant gas from the pressure of the front and rear portions thereof (the upstream side of the compressor 324 and the downstream side of the pressure control valves 404 to 406). It is configured to be adjustable. The compressor 324 and the like operate according to an instruction from the control unit 55.

The pressure vessel filling gas supply system 34 is for filling the pressure vessel 21 with gas (in this embodiment, nitrogen gas). Considering the heat resistant temperatures of the respective parts arranged in the pressure vessel 21, the nitrogen gas filled in the pressure vessel 21 is kept at a temperature lower than that of the battery stack 20.

The pressure vessel filling gas supply system 34 comprises a nitrogen tank 341 and a flow rate controller 342. In the present specification, the term "pressure in the pressure vessel 21" means the pressure of the nitrogen gas filled in the pressure vessel 21 (fuel gas and oxidant gas supplied to the cell stack 20. Pressure is not included).

The pressure vessel filling gas supply system 34 of this embodiment
Is further provided on the downstream side of the flow rate controller 342 in the compressor 3
It is equipped with 43. By the compressor 343 and a pressure control valve 407 described later, the pressure during this period (between the compressor 343 and the pressure control valve 407) can be adjusted. The compressor 343 and the like operate according to an instruction from the control unit 55. Further, the pressure vessel filling gas supply system 34
Is also supplied to the stack tightening bellows 22 and is also used for adjusting the surface pressure applied to the battery stack 20. The pressure applied by the stack tightening bellows 22 is adjustable by a compressor 343 and a pressure adjusting valve 408.

The gas exhaust system 4 is for exhausting the fuel gas and the oxidant gas after the reaction in the cell stack 20. Further, it is for discharging the nitrogen gas with which the pressure vessel 21 is filled, if necessary.
Each part of the gas exhaust system 4 is provided with heat exchangers 411, 414, buffer tanks 412, 415, water sealers 413, 416, and pressure control valves 401 to 408, which operate according to instructions from the controller 55. There is. Since all of these are well known, their detailed description will be omitted. As described above, the pressure control valves 401 to 408 operate in cooperation with the compressors 304, 306, 308, 324, 343 to control the pressure of fuel gas and the like.

The control system 5 includes an input section 50, sensors P1 and P1.
It is configured to include P2, P3, P4 and a control unit 55.

The input section 50 is for receiving inputs of various operating conditions (for example, load values).

The sensors P1 to P4 are for detecting the pressure in each part of the fuel cell power generation system. The sensor P1 is for detecting the pressure of the nitrogen gas in the pressure vessel 21. The sensor P2 is for detecting the differential pressure between the pressure inside the pressure vessel 21 and the pressure of the oxidizing gas. The sensor P3 is for detecting the differential pressure between the pressure inside the pressure vessel 21 and the pressure of the fuel gas.
The sensor P4 is for detecting the differential pressure between the pressure of the pressure vessel 21 and the pressure in the stack fastening bellows 22.

The control unit 55 is for controlling the operation of each of the above units in accordance with the operating conditions input from the input unit 50. The control unit 55 controls the standard flow rate of fuel gas and the like, the cell stack 20, and the steam generator 3 at each load value.
07, the pressure value in each of the reformer 305, and the like,
It is provided in advance as control data 550. The control unit 55
The compressors 304, 30 according to the control data 550.
6,308,324,343, pressure regulating valve, etc. 401-4
It controls 07. The actual control unit 55 includes a microprocessor, a semiconductor memory, a storage device, and various programs and data stored in the memory.

Details of the control data 550 will be described.

Control data 550 for the inside of the cell stack 20 (and the fuel gas and oxidant gas supplied thereto).
Is shown in FIG. The control data 550 defines the standard flow rate and pressure at each load. The pressure is set so that the actual flow rates of the fuel gas and the oxidant gas are kept constant regardless of the magnitude of the load (see FIG. 4). That is, when the load is large and the amount of gas required for the electrochemical reaction (standard flow rate) is large, the pressure of the supply gas is increased to prevent the actual flow rate from increasing. On the contrary, when the load is small and the required gas amount (standard flow rate) is small, the pressure is lowered to prevent the actual flow rate from decreasing. The significance of keeping the actual flow rate of the fuel gas constant has already been described in the problem to be solved.

The higher the pressure in the cell stack 20, the higher the efficiency of the fuel cell. Therefore, the pressure is set to be as high as possible within the range allowed by the strength of the battery stack 20.

Although the oxidant gas and the fuel gas are explained without distinction here, in reality, the oxidant gas, the fuel gas,
Dedicated control data 550 is prepared for each.

The control data 550 regarding the pressure inside the pressure vessel 21 will be described with reference to FIG.

In the case of the internal manifold type fuel cell, if the pressure difference between the pressure of the fuel / oxidant gas supplied to the cell stack 20 and the pressure of the nitrogen gas filled in the pressure vessel 21 becomes too large, the electrolyte There is a possibility that the wet seal portion around the substrate 81 may be damaged and further gas leak may occur. On the other hand, heat transfer from the battery stack 20 or the like to the surroundings (in this case, nitrogen gas in the pressure vessel 21) fluctuates depending on the pressure of the gas surrounding the battery stack 20. If the pressure inside the pressure vessel 21 is high,
The heat conduction is good, and it is easily affected by the temperature distribution of nitrogen gas. In order to eliminate the influence of the temperature distribution caused by the convection of nitrogen gas, it is preferable to reduce the pressure in the pressure vessel 21 as much as possible. In consideration of the contradictory circumstances as described above, in the present embodiment, the control data 550 for the pressure vessel 21 is set such that when the load is large, the pressure inside the pressure vessel 21 is increased and when the load is reduced, the pressure inside the pressure vessel 21 is increased. Is set to lower. Further, the absolute magnitude of the pressure is set as low as possible within the range where the above-mentioned problems such as gas leak do not occur. Note that FIG.
The "supply gas pressure" shown on the abscissa is a pressure value determined in consideration of both the pressure of the fuel gas and the pressure of the oxidant gas (for example, as an average value of both). Also,
From the viewpoint of mechanical strength such as prevention of gas leak in the battery stack, the range permitted as the pressure of the filling gas is indicated by diagonal lines.

In the control data 550 of the auxiliary equipment such as the steam generator 307 and the reformer 305, the pressure values are set so that these equipments operate at the highest efficiency. This value is in principle independent of the magnitude of the load on the fuel cell power generation system. However, needless to say, the capacity of these devices is taken into consideration so that the amount of fuel gas required to satisfy the above load can be supplied. This is, no matter how efficient
This is because if the absolute supply of fuel gas is insufficient, it cannot be used as a power generation system. The control data described above shows an example thereof, and the present invention is not limited to this. In this embodiment, each control data 550 is stored as a mathematical expression. However, the form of holding the control data 550 is not limited to this. For example, it may be provided as a map (list) in which the magnitude of the load and each pressure value are directly associated with each other. Further, the relationship between the load and the control parameter value of each compressor or pressure regulating valve may be held.

The control data 550 of this embodiment includes the load and
It was the relationship with the pressure (or the control parameter value for realizing this). However, it may also indicate the relationship between the standard flow rate and the pressure value (or the control parameter value for realizing the pressure). The control data 550 based on either the standard flow rate or the output value may be used. You may decide which type to use according to the type of data input to the input unit 50. If the output value is directly input, the control data 550
Is preferably based on the output value.

Next, the operation will be described.

A signal indicating the magnitude of the required load is input to the input section 50. The control unit 55 obtains a standard gas flow rate that is optimum for the required load magnitude. Then, the pressure required to flow the gas having the standard flow rate is determined without causing a change in the actual flow rate of the gas. The standard flow rate and pressure are determined by referring to the control data 550. Then, the flow rate controllers 303 and 323 and the compressor 30 are caused to flow the fuel gas and the oxidant gas for the standard flow rate at the determined pressure.
4,306,308,324, pressure regulating valves 401-40
6 is activated. Similarly, the pressure inside the pressure vessel 21 and the pressure inside the stack tightening bellows 22 are determined,
The compressor 343 is set to the pressure control valve 40 so that the pressure value is obtained.
Activating 7,408.

For example, when the load becomes large, the standard flow rate becomes large. Therefore, the compressor and the pressure regulating valve are operated to increase the pressures of the fuel gas and the oxidant gas supplied to the cell stack 20 and prevent the actual flow rate from increasing. The pressure increase in this case is performed while maintaining a predetermined differential pressure based on the signals from the sensors P2 and P3. At the same time, the pressure in the pressure vessel 21 is increased while monitoring the pressure based on the signal from the sensor P1. Furthermore, in order to maintain a predetermined battery tightening surface pressure, the pressure in the stack tightening bellows 22 is increased while monitoring the pressure with the sensor P4. Then, after this, the load is increased.

On the contrary, when the instructed load value becomes small, the load is first lowered. The smaller the load, the smaller the standard flow rate required. Therefore, the flow rate controller 30
Activate 3,323 to reduce standard flow to required level. At the same time, the compressors 304, 30
6, 308, 324 and the pressure regulating valves 401 to 406 are operated to reduce the pressures of the fuel gas and the oxidant gas supplied to the cell stack 20 and prevent the actual flow rate from decreasing. The operation in this case is performed while maintaining a predetermined differential pressure based on the signals from the sensors P2 and P3.

Further, while monitoring the pressure based on the signal from the sensor P1, the pressure inside the pressure vessel 21 is also reduced. Further, in order to maintain a predetermined battery tightening surface pressure, the pressure in the stack tightening bellows 22 is lowered while monitoring the pressure with the sensor P4.

FIG. 6 shows the flow rate distribution for each unit battery (cell) when the present invention is applied. As is clear from comparison with the flow rate distribution in the state where the present invention is not applied (FIG. 9), when the present invention is applied, the flow rate distribution is the load (current density in FIGS. 6 and 9). Less affected,
It is more uniform.

In the embodiment described above, the actual flow rate flowing through the flow path is constant regardless of the magnitude of the load (the same as at full load).
Kept in. If the actual flow rate is constant, the component ratio of the flow path resistance will be the same as at full load. Therefore, even in the partial load, the non-uniformity of the flow rate distribution of the fuel gas and the oxidant gas in the stacking direction does not increase. Further, since the amount of heat dissipated from the fuel cell body to the gas in the pressure vessel can be suppressed, it becomes possible to suppress cooling of the lower part of the fuel cell,
It is possible to suppress expansion of temperature distribution nonuniformity in the stacking direction at the time of partial load. It is possible to prevent damage to the wet seal portion around the electrolyte substrate and gas leakage. Auxiliaries can be operated under conditions that maximize their efficiency at all times.

The above-described embodiment was basically aimed at dealing with the load fluctuation. However, the present invention is not limited to this, and when the temperature distribution in the battery stack 20 is monitored and the non-uniformity of the temperature distribution becomes large, the same operation as when the load is intentionally small is irrespective of the magnitude of the load at that time. You may make it a state. That is, the pressure in the pressure vessel is reduced. Further, in order to protect the cell stack, the pressures of the fuel gas and the oxidant gas are also lowered in conjunction with this. In the case of performing such control, the control data may be set so that the standard flow rate and the pressure that can be taken for a certain load value have a certain range, as shown in FIG. The control unit controls within the range according to the temperature distribution. By doing so, it becomes possible to more positively control the temperature of the battery stack.

[0067]

As described above, according to the present invention,
While maintaining a good differential pressure between the pressure in the fuel cell body containing the fuel gas and the oxidant gas and the pressure of the gas filled in the pressure vessel, the fuel gas and the oxidant gas supplied to the fuel cell are The actual flow rate can be kept constant. Therefore, the pressure loss in each flow path can be made constant,
The flow rate distribution in the stacking direction can be made uniform.

Furthermore, since the amount of heat dissipated from the battery main body can be controlled, the temperature distribution in the stacking direction in the pressure vessel under partial load can be prevented from becoming larger than that under full load. As a result, variations in performance between cells in the stacking direction can be reduced, and power generation of the fuel cell with uniform performance becomes possible.

Further, since the pressure of the auxiliary machinery outside the pressure vessel can be controlled independently of the fuel cell main body, these auxiliary machinery can always be operated in a highly efficient state.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a fuel cell power generation system that is an embodiment of the present invention.

FIG. 2 is a perspective view showing a structure of a fuel cell stack.

FIG. 3 is a diagram showing an example of control data 550 for fuel gas and oxidant gas.

FIG. 4 is a graph showing the relationship between the actual flow rate and pressure in this example.

FIG. 5: Control data 550 for pressure in the pressure vessel
It is a figure which shows an example.

FIG. 6 is a graph showing how gas is dispersed (flow rate distribution) when the present invention is applied.

FIG. 7 is data showing an example of control data 550.

FIG. 8 is a graph showing gas distribution in the cell stacking direction when it is assumed that there is no influence of gravity.

FIG. 9 is a graph showing a state of gas dispersion (flow rate distribution) when the present invention is not applied.

[Explanation of symbols]

3 ... Gas supply system, 4 ... Gas discharge system, 5 ... Control system, 8 ... Unit battery, 11 ... Stacked cell group, 12 ... Gas header, 13 ...
Inflow port, 14 ... Outflow port, 20 ... Battery stack, 21 ... Pressure vessel, 22 ... Stack fastening bellows, 30 ... Fuel gas supply system, 32 ... Oxidant gas supply system, 34 ... Pressure vessel filling gas supply system, 50 ... Input unit, 55 ... Control unit, 81 ...
Electrolyte substrate, 82 ... Fuel electrode (anode), 83 ... Oxygen electrode (cathode), 84 ... Current collector plate, 85 ... Separator, 86
... Manifold, 87 ... Wet seal, 303 ... Flow controller, 304 ... Compressor, 305 ... Reformer, 306 ... Compressor, 307 ... Steam generator, 308 ... Compressor, 323 ...
Flow rate controller, 324 ... Compressor, 342 ... Flow rate controller, 3
43 ... Compressor, 401 ... Pressure adjusting valve, 402 ... Pressure adjusting valve, 403 ... Pressure adjusting valve, 404 ... Pressure adjusting valve, 405
... Pressure adjusting valve, 406 ... Pressure adjusting valve, 407 ... Pressure adjusting valve, 408 ... Pressure adjusting valve, 550 ... Control data, 820
... cell flow path, 830 ... cell flow path,

Claims (16)

[Claims] 1. A method of operating a fuel cell power generation system in which a fuel cell is installed in a pressure vessel, wherein a fuel gas to be supplied to the fuel cell, an oxidant gas, and the inside of the pressure vessel are provided according to the magnitude of the load. A method of operating a fuel cell power generation system, comprising: changing a pressure of a filling gas to be filled in the fuel cell. 2. The fuel according to claim 1, wherein the changes in the pressures of the fuel gas and the oxidant gas are changed so as to reduce the fluctuation range of the actual volumetric flow rate of the gas. How to operate a battery power generation system. 3. The method for operating a fuel cell power generation system according to claim 2, wherein the pressure is changed so that the volumetric flow rate is maintained at a predetermined constant value. 4. The operation of a fuel cell power generation system according to claim 3, wherein the predetermined constant value is a volume flow rate when the fuel cell is fully loaded. Method. 5. The pressure of the filling gas is changed so that the difference between the pressure of the filling gas and the pressure of the fuel gas and the pressure of the oxidant gas falls within a predetermined range. The method for operating the fuel cell power generation system according to claim 1, wherein 6. The method of operating a fuel cell power generation system according to claim 5, wherein the predetermined range is determined based on the mechanical strength of the fuel cell. 7. The method of operating a fuel cell power generation system according to claim 6, wherein the pressure of the filling gas is maintained at the lower limit of the predetermined range. 8. A method of operating a fuel cell power generation system, wherein the pressures of the fuel gas and the oxidant gas in the fuel cell are set to those in an auxiliary device for supplying the fuel gas and the oxidant gas to the fuel cell. A method of operating a fuel cell power generation system, which is characterized by controlling independently of gas pressure. 9. The pressure control is performed such that the pressure of the fuel gas and the oxidant gas in the fuel cell is controlled by the flow rate of the fuel gas and the oxidant gas,
The method for operating a fuel cell power generation system according to claim 8, characterized in that the fuel cell power generation system has a predetermined constant value. 10. A fuel cell including one or more unit cells, and supplying a fuel gas and an oxidant gas to the fuel cell and / or discharging a gas from the fuel cell. And a pressure control means capable of controlling the pressures of the fuel gas and the oxidant gas in the fuel cell independently of the pressure in the auxiliary cell. system. 11. A pressure vessel is provided, the fuel cell is installed in the pressure vessel, and the pressure control means independently of the pressure in the pressure vessel and the pressure in the auxiliary equipment. It is controllable, The fuel cell power generation system according to claim 10. 12. The pressure control means controls the pressure so that the actual volumetric flow rates of the fuel gas and the oxidant gas are maintained at a certain constant value. Fuel cell power generation system. 13. The fuel cell power generation system according to claim 12, wherein the constant value is a volume flow rate of the fuel cell in a full load operation state. 14. The pressure control means comprises storage means for storing control data indicating a correspondence relationship between a load and pressures of the fuel gas and the oxidant gas supplied to the fuel gas, and the control data is stored in the storage means. With reference to the pressure value of the fuel gas and the oxidant gas, which is associated with the value of the load, the pressure value of the fuel gas and the oxidant gas is controlled so as to be the pressure value. The fuel cell power generation system according to claim 10, wherein 15. A pressure vessel is provided, the fuel cell is installed in the pressure vessel, and the control data further includes a correspondence relationship between the load and the pressure of the filling gas. 15. The fuel cell power generation system according to claim 14, wherein the control means can control the pressure in the pressure vessel independently of the pressure in the auxiliary machine according to the control data. 16. The fuel cell power generation system according to claim 10, wherein the pressure control means includes a compressor arranged between the auxiliary machine and the fuel cell.