JP2010146747A - Fuel cell system and power generation method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent operation from being disabled and retain power generation performance. <P>SOLUTION: A fuel cell system has a solid-oxide fuel cell 10 that performs power generation by separately bringing two gasses for power generation into flow contact with two poles, a fuel pole and an air pole which are stacked on both sides of an electrolyte film and feeds power to an external load 15 connected with the solid-oxide fuel cell 10. The system is provided with: deterioration prevention determining means 31a for determining whether or not the solid-oxide fuel cell 10 stats to deteriorate on the basis of prevention criterion information for preventing the solid-oxide fuel cell 10 from being deteriorated; and deterioration prevention means 31b for preventing the solid-oxide fuel cell 10 from being deteriorated when the deterioration prevention determining means 31a determine that the solid-oxide fuel cell 10 deteriorates. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system using a solid oxide fuel cell (SOFC) and a power generation method using the same.

  Long life and high efficiency are important issues for practical application of solid oxide fuel cells (SOFC). The general operating temperature of SOFC using yttria-stabilized zirconia electrolyte is 1000 ° C. However, due to this high operating temperature, solid phase reaction between constituent materials has become a problem.

In recent years, as a solution to the above problem, an electrode-supported thin-film electrolyte cell aimed at reducing the operating temperature (600 to 800 ° C.) has attracted attention, and although high output characteristics have been reported, an electrode serving as a support There are few reports on the correlation between microstructure and long-term stability.
Proceedings of the 75th Annual Meeting of the Electrochemical Society of Japan March 2008 1B22, p. 47

  As described in detail in Non-Patent Document 1, the current density when energized under a constant voltage gradually decreases as the energization time elapses. If power generation is further continued, the current density rapidly decreases. The current density does not recover to the state before power generation, and the deterioration phenomenon is considered to be caused by the fuel electrode.

Next, as a continuous endurance experiment under a constant voltage, the current density was recovered by holding for a certain period of time in the open circuit state as a result of observing changes in the current density when repeated energization and holding in the open circuit state There is a phenomenon that.
In addition, the time until the current density at the time of energization decreases again correlates with the holding time in the open circuit state, and such a reversible deterioration phenomenon is caused by Ni in the fuel electrode due to water vapor generated by energization. It is thought to be caused by inactivation and fuel supply interruption.

Based on the above observations, it was predicted that the battery performance was degraded by the water vapor accumulated in the fuel electrode, so an attempt was made to recover the performance by electrolytically operating the battery.
That is, after maintaining a cell that has deteriorated in a constant voltage holding test at a terminal voltage higher than the open circuit voltage for a certain period of time, and observing a change in current density with time under a predetermined constant voltage, the result of the electrolytic operation of the battery is It is thought that this is due to the removal of water vapor that had remained inside.

  Accordingly, the present invention provides a fuel cell system capable of maintaining the power generation performance by preventing the inactivation of the Ni in the fuel electrode and the inoperability of the solid oxide fuel cell due to the inhibition of the fuel supply, and the power generation method using the same The purpose is to provide.

  In order to achieve the above object, a fuel cell system according to the present invention is a solid that performs power generation by separating and flowing two kinds of power generation gas between a fuel electrode and an air electrode stacked on both sides of an electrolyte. Power is supplied to an oxide type fuel cell and an external load connected to the solid oxide type fuel cell, and is based on preventive criterion information for preventing deterioration of the solid oxide type fuel cell. When the solid oxide fuel cell is determined to be deteriorated by the deterioration prevention determination means for determining whether or not the solid oxide fuel cell starts to deteriorate, and the deterioration prevention determination means, the solid oxide fuel cell Degradation prevention means for preventing degradation of the

  A power generation method according to the present invention for achieving the above object is a solid that performs power generation by separating and flowing two kinds of power generation gases from each other on a fuel electrode and an air electrode stacked on both sides of an electrolyte. A fuel cell system having an oxide fuel cell and supplying power to an external load connected to the solid oxide fuel cell is used to prevent deterioration of the solid oxide fuel cell. Therefore, it is determined whether the solid oxide fuel cell starts to deteriorate based on the preventive determination criterion information for the deterioration, and when it is determined that the solid oxide fuel cell is deteriorated, the solid oxide fuel cell is deteriorated. The content is to prevent.

  According to the present invention, it is possible to prevent the solid oxide fuel cell from becoming inoperable due to the inactivation of Ni in the fuel electrode and the inhibition of the fuel supply, and the power generation performance can be maintained.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the fuel cell system according to the first embodiment of the present invention, and FIG. 2 is a block diagram showing the function of a control unit forming a part of the fuel cell system.

  The fuel cell system A1 according to the first embodiment of the present invention is configured to supply power to an external load 15 such as a motor connected to a solid oxide fuel cell (hereinafter simply referred to as “fuel cell”) 10 according to an example. It is the structure of feeding.

  Specifically, in addition to the fuel cell 10 and the external load 15 described above, the first disconnector 20, the feed pump 21 for feeding fuel to the fuel electrode 10 a of the fuel cell 10, and the fuel cell 10 A compressor 22, a voltmeter 23, an ammeter 24, an AC resistance meter 25, a control unit (hereinafter abbreviated as “C / U”) 30 and the like for supplying air to the air electrode 10b of Has been.

  The fuel cell 10 has a case 13 in which a single cell stack in which a plurality of cell units 12 are stacked on each other is accommodated. FIG. 1 shows only one cell unit 12 for the sake of simplicity.

The cell unit 12 includes a solid electrolyte cell 11... In which a fuel electrode 10a having Ni and an air electrode 10b are provided on both sides of an electrolyte 10c. The cell unit 12 includes two fuel electrodes 10a and 10b. Power generation is performed by separating and flowing various types of power generation gas from each other.
Two types of power generation gas are, for example, air and hydrocarbon fuel gas.

The first connecting / disconnecting device 20 is, for example, a relay that connects / disconnects the external load 15 to / from the fuel cell 10, and is disposed in the middle of the output terminals 14 a, 14 b of the fuel cell 10 connected to the external load 15.
The first disconnector 20 is connected to an output port of a C / U 30 whose details will be described later, and is connected and disconnected by a disconnection signal output from the C / U 30.

The above-described ammeter 24 for measuring the output current of the fuel cell 10 is provided at one of the output terminals 14a and 14b, and the voltmeter for measuring the output voltage between the output terminals 14a and 14b. 23 and an AC ohm meter 25 are provided.
The ammeter 23, the voltmeter 24, and the AC ohmmeter 25 are connected to the input port side of the C / U 30 so that each acquired measurement value is input.

In the present embodiment, the ammeter 23 and the voltmeter 24 described above are output measuring instruments that measure the output of the fuel cell 10.
The AC resistance meter 25 is an internal resistance measuring instrument for measuring the internal AC resistance of the fuel cell 10.

  As shown in FIG. 2, the C / U 30 includes a central control unit 31 including a CPU (Central Processing Unit), an interface circuit and the like (all not shown), and a memory 32 including a hard disk and a semiconductor memory. is there.

  In the memory 32, in addition to a program for causing the central control unit 31 to perform a required function, preventive determination reference information for preventing the deterioration of the fuel cell 10, and a recovery determination for recovering the already deteriorated fuel cell 10 The reference information, the opening / closing time for opening the first disconnector 20 and the like are stored.

The preventive determination criterion information in the present embodiment is the operating time (operating time) of the fuel cell 10, but the output of the fuel cell 10 acquired by the output measuring instrument such as the ammeter 23 or the voltmeter 24, or the AC resistance The internal resistance of the fuel cell 10 acquired by an internal resistance measuring instrument such as a total of 25 may be used.
“Operating time” is obtained, for example, by measuring in advance the time until deterioration by experiment.

When the voltmeter 24 is used, the lower limit value of the current density under a certain voltage can be applied as the preventive determination reference information.
In the following description, it is assumed that the preventive determination criterion information is the operating time (operating time) of the fuel cell 10. However, a combination of the operating time and the output of the fuel cell 10 and its internal AC resistance is preventive determined. Reference information may be used.
Of course, only the output of the fuel cell 10 or only its internal resistance can be used as the preventive determination criterion information.

In this embodiment, “deterioration” refers to a state in which the output current density under a constant voltage decreases with time and cannot be recovered by normal operation. This is referred to as an “inoperable state”.
“Normal operation” refers to operation with the external load 15 connected to the fuel cell 10.
“Recovery criterion information” is, for example, the lower limit value of the current density under a certain voltage.

By executing the program used in the fuel cell system A1 stored in the memory 32, the C / U 30, and thus the central control unit 31, exhibits the following functions.
(1) A function of determining whether or not the fuel cell 10 starts to deteriorate based on prevention determination reference information for preventing the deterioration of the fuel cell 10. This function is referred to as “deterioration prevention determination means 31a”.
In the present embodiment, the operating time of the fuel cell 10 stored in the memory 32 as described above, and depending on whether or not this operating time has elapsed, the fuel cell 10 and thus the solid electrolyte cell 11 are deteriorated. It is determined whether or not to start.

  In addition, when only the output of the fuel cell 10 or only its internal resistance is used as the preventive judgment reference information, the output is measured via an output measuring instrument such as an ammeter 23 or a voltmeter 24 or an internal resistance measuring instrument such as an AC ohmmeter 25. A function for acquiring the prevention determination reference information, that is, “reference information acquisition means 31d” may be provided.

(2) A function of preventing deterioration of the fuel cell 10 when the deterioration prevention determination means 31a determines that the fuel cell 10 is deteriorated. This function is referred to as “deterioration preventing means 31b”.
In the present embodiment, the first disconnector 20 is used to cut off and open the external load 15 from the fuel cell 10 for a predetermined cut-off time.
Further, in the present embodiment, when it is determined by the following opening time determination means 31 c that the predetermined interruption opening time has elapsed, the external load 15 is connected to the fuel cell 10 by the first disconnector 20. ing.

(3) A function for determining whether or not a predetermined shut-off time has elapsed. This function is referred to as “open time determination means 31c”.
(4) A function of determining whether or not the fuel cell 10 has already deteriorated based on the recovery determination criterion information stored in the memory 32. This function is referred to as “degradation recovery determination means 31d”.
As described above, the criterion information for determining whether or not the deterioration has already occurred is a lower limit value of the current density under a certain voltage, in other words, a predetermined threshold value.

(5) A function of recovering the deterioration of the fuel cell 10 when the deterioration recovery determining means 31d determines that the fuel cell 10 has already deteriorated. This function is referred to as “degradation recovery means 31e”.
In the present embodiment, the first disconnector 20 is used to cut off and open the external load 15 from the fuel cell 10 for a predetermined cut-off time.

This “break open time” is for recovering the deterioration of the fuel cell 10 that has already deteriorated, and is set longer than the break open time by the deterioration preventing means 31b.
Then, when it is determined by the opening time determination means 31 c that the predetermined breaking open time has elapsed, the external load 15 is connected to the fuel cell 10 by the first disconnector 20.

  The operation of the fuel cell system A1 according to the first embodiment configured as described above will be described with reference to FIGS. FIG. 3 is a flowchart showing a preventive operation in the fuel cell system A1, and FIG. 4 is a flowchart showing a recovery operation in the fuel cell system A1.

  The power generation method using the fuel cell system A1 described above determines whether or not the fuel cell 10 starts to deteriorate based on the preventive determination criterion information for preventing the fuel cell 10 from deteriorating, and the fuel cell 10 Is determined to prevent deterioration of the fuel cell 10, the details of which are as follows.

First, the prevention operation will be described with reference to FIG.
<Preventive action>
Step 1 (abbreviated as “S1” in the figure. The same applies hereinafter): The normal operation is performed and the process proceeds to Step 2.

Step 2: It is determined whether or not a preventive operation is to be executed.
For example, it is determined whether or not the preventive operation is to be executed by measuring the time at which deterioration starts in advance and storing it in the memory 32 of the C / U 30 and comparing the deterioration time with the actual operation time. I do.
Further, for example, in the second round, it may be determined whether or not the preventive operation is to be performed based on the disconnection / opening time by the first disconnector 20 performed in Step 4.

  Step 3: The preventive operation of the fuel cell 10 is executed. Specifically, by opening the first disconnector 20, the external load 15 is disconnected from the fuel cell 10, in other words, the output terminals 14 a and 14 b of the fuel cell 10 are opened. The fuel electrode 10a is reduced. Thereby, it is possible to prevent the fuel cell 10 from becoming inoperable.

Step 4: It is determined whether or not the preventive operation is finished. For example, a predetermined shut-off time is set in the memory 32, and it is determined whether or not the shut-off time has elapsed. Here, if the time has not elapsed, the process returns to step 3, and if the time has elapsed, the process proceeds to step 5.
The shut-off time is the execution time of the preventive operation.

The optimum shut-off time is the relationship between the shut-off time and the time until the operating efficiency of a constant output deteriorates by performing normal operation using another fuel cell 10 that has been prevented by varying the shut-off time. It can be grasped by examining.
Step 5: Return to the normal operation of Step 1.

Next, the recovery operation will be described with reference to FIG.
<Recovery action>
Step 1 (abbreviated as “S1” in the figure. The same applies hereinafter): The normal operation is performed and the process proceeds to Step 2.

Step 2: It is determined whether or not the recovery operation is to be executed.
Specifically, it is determined whether or not the current density actually output from the output terminals 14a and 14b of the fuel cell 10 is smaller than a lower limit value of a preset current density, and is determined to be smaller than the lower limit value. If so, the process proceeds to step 3; otherwise, the process returns to step 1.

Step 3: The recovery operation of the fuel cell 10 is executed.
Specifically, by opening the first disconnector 20, the external load 15 is disconnected from the fuel cell 10, in other words, the output terminals 14 a and 14 b of the fuel cell 10 are opened. The fuel electrode 10a is reduced.
As a result, the fuel cell 10 that has become inoperable can be recovered to be operable.

Step 4: Determine whether to end the recovery operation.
For example, a cutoff opening time for recovery is set in the memory 32, and it is determined whether or not the cutoff opening time has elapsed. Here, if the time has not elapsed, the process returns to step 3, and if the time has elapsed, the process proceeds to step 5.
Step 5: Return to the normal power generation operation of Step 1.

  By executing the above steps, even if the fuel cell 10 has deteriorated for some reason, it can be recovered.

Next, a fuel cell system according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a block diagram showing a configuration of the fuel cell system according to the second embodiment, and FIG. 6 is a block diagram showing functions of a controller unit forming a part of the fuel cell system according to the second embodiment. is there.
In addition, about the thing equivalent to what was demonstrated in embodiment mentioned above, the code | symbol same as them is attached | subjected and description is abbreviate | omitted.

  In addition to the configuration of the fuel cell system A1 described above, the fuel cell system A2 according to the second embodiment includes a battery 40 that is a power source, a DC / DC converter 41, a second disconnector 42, an inverter 43, and a third power source. The disconnector 44 is provided.

  The battery 40 supplies power for reduction for reducing the fuel electrode 10 a of the fuel cell 10, and also supplies power for driving to the external load 15 via the inverter 43. is there.

The DC / DC converter 41 is for performing voltage conversion for the inverter 43 or the fuel cell 10.
The inverter 43 is for converting the DC power output from the fuel cell 10 into AC, and for converting the DC power supplied from the battery 40 into AC and supplying power to the external load 15.
In FIG. 5, an AC motor 15 connected as the external load 15 is shown.

The second connecting / disconnecting device 42 is interposed between the DC / DC converter 41 and the fuel cell 10 and is connected to the output port side of the C / U 30 so as to be connected / disconnected.
The third disconnector 44 is interposed between the DC / DC converter 41 and the inverter 43, and is connected to the output port side of the C / U 30 in the same manner as the second disconnector 42. It is supposed to work.

  The C / U 30 realizes each means of the fuel cell system A1 by executing the program used for the fuel cell system A2 stored in the memory 32. In the present embodiment, however, the above-described deterioration of the function is performed. Instead of the preventive means, a deterioration preventive means that exhibits the following functions is provided.

(7) When it is determined by the deterioration prevention determination means 31a that the fuel cell 10 is deteriorated, the external load 15 is disconnected from the fuel cell 10 through the first connecting / disconnecting portion 20 for the cutoff opening time, and the second The function of connecting the battery 40 to the fuel cell 10 via the disconnector 42. This is referred to as “deterioration preventing means 31f”.
As a result, a reduction current is applied to the fuel electrode 10 to prevent the start of deterioration.

  Further, the external load 15 is disconnected from the fuel cell 10 through the first connection / disconnection portion 20 for the disconnection / release time, and the battery 40 is connected to the fuel cell 10 through the second connection / disconnection device 42. Therefore, the time required for reduction can be shortened.

  Since the operation of the fuel cell system A2 according to the second embodiment having the above-described configuration is the same as that described in FIGS. 3 and 4 except for Step 3, refer to FIGS. Step 3 in the prevention operation and the recovery operation will be described.

First, the prevention operation will be described with reference to FIG.
<Preventive action>
In step 1, normal operation is performed and the process proceeds to step 2. In step 2, it is determined whether or not the preventive operation is to be performed, and then the process proceeds to step 3.

Step 3: The preventive operation of the fuel cell 10 is executed.
In the present embodiment, the external load 15 is disconnected from the fuel cell 10 via the first connecting / disconnecting portion 20 for the disconnection opening time, and the battery 40 is connected to the fuel cell 10 via the second connecting / disconnecting device 42. Connect to.
As a result, the output terminals 14a and 14b of the fuel cell 10 are in an open circuit state, and the reduction current from the battery 40 is supplied to the fuel electrode 10a, so that the fuel electrode 10a can be reduced more quickly. .

More specifically, the first disconnector 20 is opened, the second disconnector 42 is closed, and the third disconnector 44 is opened.
At this time, the DC / DC converter 41 is controlled to increase the voltage between the output terminals 14 a and 14 b of the fuel cell 10. As a result, a reduction current is passed through the fuel electrode 10a.
Then, the process proceeds to step 4 and subsequent steps to perform the same processing.

Next, the recovery operation will be described with reference to FIG.
<Recovery action>
In step 1, a normal power generation operation is performed and the process proceeds to step 2. In step 2, it is determined whether or not a preventive operation is to be performed, and the process proceeds to step 3.

Step 3: The recovery operation of the fuel cell 10 is executed.
Specifically, the external load 15 is disconnected from the fuel cell 10 through the first connecting / disconnecting portion 20 for the disconnection opening time, and the battery 40 is connected to the fuel cell 10 through the second connecting / disconnecting device 42. Connecting. Thereby, the fuel cell 10 is in an open circuit state, the fuel electrode 10a is reduced, and a reduction current is also supplied from the battery 40 to promote reduction of the fuel electrode 10a.

Specifically, the first disconnector 20 is driven to open, the second disconnector 42 is closed, and the third disconnector 44 is driven to open.
Further, the DC / DC converter 41 is controlled to increase the voltage between the output terminals 14 a and 14 b of the fuel cell 10. As a result, a reduction current is passed through the fuel electrode 10a.
Thereafter, the process proceeds to step 4 to perform the same processing.

Next, a fuel cell system according to a third embodiment will be described with reference to FIGS.
That is, the fuel cell system A3 according to the third embodiment is the same as the hardware configuration of the fuel cell system A2 according to the second embodiment described above, but the functions of the C / U 30 are different. .

  The C / U 30 realizes each unit of the fuel cell system A1 by executing the program used for the fuel cell system A3 stored in the memory 32. In the present embodiment, the C / U 30 has the above-described functions. Instead of the deterioration prevention means, a deterioration prevention means and a deterioration recovery means that exhibit the following functions are provided.

(8) When it is determined by the deterioration prevention determination means 31a that the fuel cell 10 is deteriorated, the external load 15 is connected to the fuel cell 10 via the first disconnector 20 and the second disconnector 42 is connected. A function of connecting the battery 40 to the fuel cell 10 via This is referred to as “deterioration preventing means 31 g”.
Specifically, the first breaker 20 is driven to open, the second breaker 42 is closed, and the third breaker 44 is closed.
By closing the third connecting / disconnecting device 44, the battery 40 is connected to the motor 15 via the inverter 43, and the rotation of the motor 15 can be continued while preventing the fuel cell 10 from deteriorating. it can.

Further, the DC / DC converter 41 is controlled to increase the voltage between the output terminals 14 a and 14 b of the fuel cell 10. Thereby, a reduction current is passed through the fuel electrode 10a.
Then, the process proceeds to step 4 and subsequent steps to perform the same processing.
As a result, a reduction current is applied to the fuel electrode 10 to prevent the start of deterioration.

(9) A function of connecting the external load 15 to the fuel cell 10 via the first disconnector 20 and connecting the battery 10 to the fuel cell 40 via the second disconnector. This function is referred to as “deterioration recovery means 31h”.
Specifically, the deterioration prevention means 31g, and the prevention operation and the recovery operation are the same as those described in the fuel system A2, and therefore, the description thereof is omitted here.

  Next, a fuel cell system according to a fourth embodiment employing a fuel cell according to another example will be described with reference to FIGS. FIG. 7 is a block diagram illustrating a configuration of a fuel cell according to another example, and FIG. 8 is a block diagram illustrating functions of a control unit that forms part of the fuel cell system according to the fourth embodiment.

  The fuel cell system A4 according to the fourth embodiment described below has the same configuration as that described in the first embodiment except for the configuration of the fuel cell. In the present embodiment, a fuel cell according to another example will be mainly described.

  A fuel cell 10A according to another example includes a fuel pump 50, 51, 52, a fuel evaporator 50, a cell stack 53, a stack heating heat exchanger 54, a circulation blower 55 as a feeder, a branch valve 56, a mixer 57, a fuel The reformer 58, the reformer superheat heat exchanger 70, the combustors 59 and 60, the cathode air heater 61, the air blowers 62 to 64 and 69, the shutoff valves 65 and 66, the concentration sensors 67 and 68, and the like. Configured.

The fuel pump 51 supplies fuel necessary for power generation of the fuel cell 10A to the fuel evaporator 50. A feed pipe 51a is connected between the fuel pump 51 and the fuel evaporator 50. Yes.
The fuel pump 51 is connected to the output port side of the C / U 30 and is appropriately driven.

The fuel evaporator 50 vaporizes the fuel fed by the fuel pump 51, and a feed pipe 50 a is connected between the fuel evaporator 50 and the mixer 57.
The mixer 57 has a function of selectively switching raw fuel, exhaust fuel gas or air supplied from the fuel evaporator 50, the branch valve 56 and the air blower 69. The fuel reformer 58, air blower 69 and the branch valve 56 are connected with feed pipes 57a, 69a and 56a, respectively.

  The fuel reformer 58 reforms the vaporized raw fuel into a hydrogen-rich fuel gas, and a supply pipe 58a is connected between the fuel reformer 58 and the fuel cell 10, and the fuel gas is supplied to the fuel reformer 58. The fuel is supplied to the fuel electrode 10a.

The concentration sensor 67 is for measuring carbon monoxide of the fuel gas flowing through the feed pipe 58a, and the concentration sensor 68 is for measuring each concentration of the oxygen.
These concentration sensors 67 and 68 acquire connection reference information when the external load 15 is reconnected to the fuel cell 10 after the external load 15 is cut off and opened from the fuel cell 10, for example.
The deterioration prevention means and the deterioration recovery means can connect the external load 15 to the fuel cell 10 via the first disconnector 20 based on the connection reference information.

A feed pipe 55a is connected between the fuel electrode 10a and the branch valve 56, and a circulation blower for circulating the exhaust gas discharged from the fuel electrode 10a in the middle of the feed pipe 55a. 55 is disposed.
The air blower 69, the branch valve 56, the circulation blower 55, and the shutoff valve 66 are connected to the output port side of the C / U 30 and are appropriately driven.

The air blower 62 supplies air necessary for power generation of the fuel cell 10 to the cathode air heater 61, and a supply pipe 62 a is connected between the air blower 62 and the cathode air heater 61. Has been.
The air blower 62 is connected to the output port side of the C / U 30 and is appropriately driven.

The cathode air heater 61 heats the air supplied to the cell stack 53, and a supply pipe 61a is connected between the cathode air heater 61 and the fuel electrode 10a.
Further, a feed pipe 50 b is connected between the fuel electrode 10 a and the above-described fuel evaporator 50, and air discharged from the fuel electrode 10 a is sent to the fuel evaporator 50, and is supplied from the air blower 62. Heat exchange with the supplied air can be performed.

The combustor 59 burns fuel and air fed by the fuel pump 52 and the air blower 63, and a feed pipe 59 a is interposed between the combustor 59 and the stack heating heat exchanger 54. It is connected.
In this embodiment, the combustor 59 is a heating source of the stack heating heat exchanger 54 that is a cell heater.

  The stack heating heat exchanger 54 is disposed in close contact with the cell stack 53, and heats the cell stack 53 with the heated gas sent from the combustor 59 and performs heat exchange.

  A feed pipe 54 a is connected between the stack heating heat exchanger 54 and the cathode air heater 61 described above, and the heated gas discharged from the stack heating heat exchanger 54 is supplied to the cathode air heater 61. To exchange heat with the air supplied to the air electrode 10b.

The combustor 60 burns fuel and air fed by the fuel pump 53 and the air blower 64, and a feed pipe 60a is connected between the combustor 60 and the above-described branch valve 56. Has been. A shutoff valve 65 is disposed in the middle of the feed pipe 60a.
The fuel pumps 52 and 53, the air blowers 63 and 64, and the shutoff valves 65 and 69 are also connected to the output port side of the C / U 30 and are appropriately driven.

  The reformer heating heat exchanger 70 is disposed in close contact with the fuel reformer 58, and a feed pipe 60b is connected to the combustor 60, and is discharged from the fuel electrode 10a and combusted. Heat exchange is performed between the exhaust gas heated by 60 and the fuel gas reformed by the fuel reformer 58.

A feed pipe 70 a is connected between the reformer heating heat exchanger 70 and the feed pipe 61 a, and exhaust gas discharged from the reformer heating heat exchanger 70 is sent to the cathode air heater 61. I am trying to pay. Thereby, the heat exchange in the cathode air heater 61 can be performed more efficiently.
In the present embodiment, the combustor 60 is a heating source of the reformer heating heat exchanger 70 that is a fuel reformer.

  The C / U 30 realizes each means of the fuel cell system A1 by executing a program used in the fuel cell system A3 stored in the memory 30, and has the following functions.

(9) A function of heating the stack heating heat exchanger 54 by the combustor 59 when the deterioration prevention means 31b prevents the fuel cell 10 from being deteriorated. This function is referred to as “cell heating means 31i”.
Specifically, the stack heating heat exchanger 54 is heated by the combustor 59 when the external load 15 is disconnected from the fuel cell 10 via the first disconnector 20.

  Thereby, the temperature drop of the cell stack 53 can be prevented and kept in the operating temperature band when the external load 15 is disconnected and opened from the fuel cell 10 via the first disconnector 20, so that the fuel cell 10 The restartability can be improved.

(10) A function of heating the reformer heating heat exchanger 70 by the combustor 60 when the deterioration prevention means 31b prevents the fuel cell 10 from deteriorating. This function is referred to as “reformer heating means 31j”.
Thereby, it is possible to prevent the temperature of the fuel reformer 58 from decreasing when the external load 15 is disconnected from the fuel cell 10 via the first disconnector 20, and the restartability of the fuel cell 10 can be prevented. Can be increased.

The operation of the fuel cell system A4 according to the above-described fourth embodiment will be described.
Fuel and air necessary for power generation of the fuel cell 10 are introduced from a fuel pump 51 and an air blower 62, respectively.
<Overview of fuel electrode side passage>
The fuel introduced from the fuel pump 51 is vaporized by the fuel evaporator 50.
The fuel evaporator 50 performs heat exchange between the exhaust gas discharged from the fuel electrode 10a and the fuel through the ball feeding pipe 50b, and raises the temperature of the vaporized raw fuel.

The vaporized raw fuel delivered from the fuel evaporator 50 is mixed with air and the fuel electrode circulation gas by the mixer 57 and introduced into the fuel reformer 58.
At this time, the fuel electrode gas contains water vapor and carbon dioxide generated by power generation. These water vapor, carbon dioxide, and oxygen contained in the air introduced from the air blower 69 are necessary for suppressing carbon deposition in the circulation path including the fuel reformer 58 and the fuel electrode 10a.

In the fuel reformer 58, a partial oxidation reaction (exothermic reaction) with the introduced raw fuel and oxygen, a steam reforming reaction (endothermic reaction) with the fuel and steam, and carbon monoxide and steam generated by these reactions. A shift reaction (exothermic reaction) proceeds.
Then, the reformed gas sent from the fuel reformer 58 is introduced into the fuel electrode 10a.

  Hydrogen and carbon monoxide contained in the fuel introduced into the fuel electrode 10a cause an electrochemical reaction with oxygen ions supplied from the air electrode 10b through the electrolyte membrane 10c, thereby generating water and carbon dioxide, respectively. At the same time, electrons are supplied to the electrode (external circuit side).

And the exhaust gas discharged | emitted via the fuel electrode 10a is pressure | voltage-risen by the circulation blower 55, and a part of this circulates through the said circulation path.
The circulation rate at this time is determined based on the amount of steam and carbon dioxide necessary for suppressing carbon deposition in the fuel reformer 58 and the like.

Excess exhaust gas is introduced into the combustor 60 from the branch valve 56.
The combustor 60 mixes and burns carbon monoxide and hydrogen in the exhaust gas from the fuel electrode 10a with newly introduced air to generate a high-temperature heating gas.
This heated gas is introduced into the reformer heating heat exchanger 70 and used for heating the fuel reformer 58 and the reformed gas.

At this time, the temperature of the fuel reformer 58 needs to be maintained at a predetermined temperature necessary for the reforming reaction.
That is, the temperature of the fuel reformer 58 is determined by the amount of heat introduced from the reformer heating heat exchanger 70, the endothermic reaction heat amount that proceeds in the fuel reformer 58, the exothermic reaction heat amount, and the enthalpy and heat capacity of the inlet gas. .

  When the endothermic reaction amount is large and the temperature of the fuel reformer 58 does not reach a predetermined temperature, additional fuel is introduced into the combustor 60 via the fuel pump 53 to increase the enthalpy of the heated gas. As a result, the amount of heat introduced from the reformer heating heat exchanger 70 increases, and the temperature of the fuel reformer 58 can be maintained at a predetermined temperature.

  The heated gas discharged from the reformer heating heat exchanger 70 is mixed with the stack heating exhaust gas and introduced into the cathode air heater 61. The cathode air heater 61 transfers heat from the mixed gas to the air sent to the air electrode 10b, and raises the temperature of the air.

<Outline of air electrode side passage>
The air introduced from the air blower 62 is heated by the cathode air heater 61 and introduced into the air electrode 10 b of the fuel cell 10. Oxygen contained in the air introduced into the air electrode 10b reacts with electrons at the air electrode 10b to generate oxygen ions. Electrons are supplied from the air electrode 10b via an external load circuit.

Oxygen ions generated at the air electrode 10b are conducted to the fuel electrode 10a through the electrolyte 10c. At this time, the temperature of the cell stack (fuel electrode 10a and air electrode 10b) 53 needs to be maintained at a predetermined temperature required for the fuel cell reaction (anode reaction / cathode reaction). The temperatures of the fuel electrode 10a and the air electrode 10b are determined from the amount of reaction heat (the amount of exhaust heat not extracted as electric power) that travels on each electrode, the enthalpy of the introduced fuel / air gas, and its heat capacity.
At this time, for example, when the reaction efficiency of the fuel cell 10 is high and the temperature of the cell stack 53 does not reach a predetermined temperature, additional fuel and air are introduced into the combustor 59 via the fuel pump 52 and the air blower 63 to increase the temperature. Gas is generated and this hot gas is introduced into the stack heating heat exchanger 54.

  The heat introduced from the stack heating heat exchanger 54 can heat both the fuel electrode / air electrode due to the effect of solid heat conduction in the cell stack 53. Thereby, heat can be supplied to the cell stack 53 and the cell stack 53 can be maintained at a predetermined temperature.

  The heated gas discharged from the stack heating heat exchanger 54 is mixed with the exhaust gas discharged from the fuel reformer 58 and introduced into the cathode air heater 61. The cathode air heater 61 transfers heat from the mixed gas to the cathode air, and raises the temperature of the air sent to the air electrode 10b.

  Next, an operation when power generation by the fuel cell system A4 is terminated will be described with reference to FIG. FIG. 9 is a flowchart showing an operation when power generation by the fuel cell system A4 is terminated.

Step 1 (abbreviated as “S1” in the figure. The same applies hereinafter): The system proceeds to Step 2 in response to a system termination command.
Step 2: The preventive operation of the fuel cell 10 is executed and the process proceeds to Step 3.
Specifically, the breaker 50 is opened. The shutoff valves 65 and 66 shown in FIG. 7 are closed to close the fuel flow path. At the same time, the circulation blower 55 is operated to circulate the reducing gas to the fuel electrode 10a. As a result, the fuel electrode 10a is reduced.

Step 3: Determine the end of the preventive operation. For example, by referring to the shut-off time stored in the memory 32, it is determined whether or not the time has elapsed. If the shut-off time has been exceeded, the process proceeds to step 4; otherwise, the process returns to step 2.
Step 4: Normal stop control is performed.

  Next, another example of the fuel cell will be described with reference to FIG. FIG. 10A is a block diagram showing a configuration in which two fuel stacks are arranged in parallel, and FIG. 10B is a block diagram showing a configuration in which two fuel stacks are connected in series.

  The fuel cell 10B according to the first other example is one in which two cell stacks 80, 81 are connected in parallel via a relay box 82 that selectively switches, and the fuel cell 10B is connected to the fuel cell system A2, 3 is assumed.

  In this configuration, the deterioration prevention determination unit 31a determines whether one of the fuel cells 80, 81 starts to deteriorate based on the deterioration prevention determination reference information stored in the memory 32, and prevents deterioration. The means 31b prevents the deterioration of the fuel cell 80 (81) determined by the deterioration prevention determination means 31a.

Specifically, the fuel cell 80 (81) to be prevented from being deteriorated is connected to the battery 40 via the disconnector 42. Thus, a reduction current is applied to the fuel electrode 10a of the fuel cell 80 (81) to prevent it.
When it is determined that all the fuel cells are deteriorated, all the fuel cells are connected to the battery 40.

  Further, the deterioration recovery determination means 31d determines whether any of the fuel cells has already deteriorated based on the recovery determination reference information stored in the memory 32, and the deterioration recovery means 31e The deterioration of the fuel cell 80 (81) determined to have already deteriorated by the means 31d is recovered.

  A fuel cell 10C according to a second other example is obtained by connecting two cell stacks 84 and 85 in series via a changeover switch 86, and this fuel cell 10C is used in fuel cell systems A2 and A3. Is assumed.

  In the case of this configuration, the deterioration prevention determination unit 31d determines whether any of the cell stacks 84 and 85 starts to deteriorate based on the deterioration determination reference information stored in the memory 32, and the deterioration prevention unit 31b. Prevents deterioration of the fuel cell 84 (85) determined by the deterioration prevention determination means 31a.

Specifically, for example, when the deterioration of the fuel cell stack 85 is prevented, the cell stack 84 is disconnected by the changeover switch 686. In order to prevent the cell stack 84 from being deteriorated, the cell stack 85 is separated by the changeover switch 86.
As a result, a reduction current is applied to the fuel electrode (not shown) of the cell stack 84 (85) to prevent it.

Further, the deterioration recovery determining means 31d determines whether any of the cell stacks 84 (85) has already deteriorated based on the recovery determination reference information stored in the memory 32, and the deterioration recovery means 31 Then, the deterioration of the cell stack 84 (85) determined to be already deteriorated by the deterioration recovery means 31e is recovered.
In this example, a configuration in which two cell stacks are provided has been described. However, the present invention is not limited to two, and may be applied to three or more.

The present invention is not limited to the above-described embodiments, and the following modifications can be made.
Although described in detail above, in any case, each configuration described in each of the above embodiments is not limited to being applied only to each of the above embodiments, and the configuration described in one embodiment is not limited to other embodiments. It can be applied mutatis mutandis or applied to the form, and can be arbitrarily combined.

-In embodiment mentioned above, although what comprised the heating source of a cell heater and the heating source of the reformer heater was illustrated separately, while making them into the same heating source, cell heating A diversion channel for diverting the heating gas may be provided between the heater and the reformer heater.
Moreover, it is not restricted to heating gas, A cell heater and a reformer heater may be made into an electric heater, and a battery may be employ | adopted as a heating source.

1 is a block diagram showing a configuration of a fuel cell system according to a first embodiment of the present invention. It is a block diagram which shows the function of the control unit which makes a part of fuel cell system same as the above. It is a flowchart which shows the prevention operation | movement in a fuel cell system same as the above. It is a flowchart which shows recovery operation | movement in a fuel cell system same as the above. It is a block diagram which shows the structure of the fuel cell system which concerns on 2nd embodiment of this invention. It is a block diagram which shows the function which the controller unit of a fuel cell system same as the above has. It is a block diagram which shows the structure of the fuel cell which concerns on another example. It is a block diagram which shows the function which the control unit which makes a part of fuel cell system which concerns on 4th embodiment has. It is a flowchart which shows operation | movement when complete | finishing the electric power generation by a fuel cell system same as the above. (A) is a block diagram showing a configuration in which two fuel stacks are arranged in parallel, and (B) is a block diagram showing a configuration in which two fuel stacks are connected in series.

Explanation of symbols

10 Solid Oxide Fuel Cell 10c Electrolyte Membrane 10a Fuel Electrode 10b Air Electrode 11 Cell 15 External Load 20 First Disconnector 23-25 Output Measuring Device (Voltmeter, Ammeter, Internal Resistor)
31a Deterioration prevention determination means 31b, 31f, 31g Deterioration prevention means 31c Deterioration recovery determination means 31d, 31e, 31h Deterioration recovery means 31i Cell heating means 31j Reformer heating means 32 Memory 42 Second disconnector 40 Power supply 59, 60 Heating source 70 Reformer heater (reformer heating heat exchanger)
80, 81, 84, 85 Cell stack 84 Cell heater (stack overheat heat exchanger)
A1-A4 Fuel cell system

Claims (16)

A solid oxide fuel cell having a solid oxide fuel cell that generates power by separating and flowing two kinds of power generation gas between a fuel electrode and an air electrode laminated on both sides of an electrolyte. A fuel cell system for supplying power to an external load connected to
Deterioration prevention determination means for determining whether or not the solid oxide fuel cell starts to deteriorate based on prevention determination reference information for preventing deterioration of the solid oxide fuel cell;
A fuel cell system comprising: a deterioration preventing means for preventing deterioration of the solid oxide fuel cell when the deterioration preventing determining means determines that the solid oxide fuel cell is deteriorated. There is a memory that pre-stores preventive criteria information,
2. The fuel cell system according to claim 1, wherein the deterioration prevention determination means determines whether or not the solid oxide fuel cell starts to deteriorate based on the prevention determination reference information stored in the memory. .   The fuel cell system according to claim 2, wherein the preventive determination criterion information is an operation time of the solid oxide fuel cell. An output measuring device for measuring the output of the solid oxide fuel cell is provided,
2. The fuel cell system according to claim 1, wherein the output of the solid oxide fuel cell acquired by the output measuring device is used as preventive determination reference information. An internal resistance measuring device for measuring the internal resistance of the solid oxide fuel cell is provided,
2. The fuel cell system according to claim 1, wherein the internal resistance of the solid oxide fuel cell acquired by the internal resistance measuring device is used as preventive determination reference information. While providing a first disconnector for connecting and disconnecting an external load to the solid oxide fuel cell,
The fuel cell system according to any one of claims 1 to 5, wherein the deterioration preventing means cuts off and opens an external load from the solid oxide fuel cell via the first disconnector. Degradation recovery determination means for determining whether or not the solid oxide fuel cell has already deteriorated based on recovery determination criterion information serving as a reference for recovering the already deteriorated solid oxide fuel cell;
7. A deterioration recovery means for recovering the deterioration of the solid oxide fuel cell when the deterioration recovery determination means determines that the solid oxide fuel cell has already deteriorated. The fuel cell system according to any one of the above. Recovery criteria information is stored in memory,
8. The fuel cell according to claim 7, wherein the deterioration recovery determination means determines whether or not the solid oxide fuel cell has already deteriorated based on the recovery determination reference information stored in the memory. system. A power source for reducing the anode of the solid oxide fuel cell and a second disconnector for connecting and disconnecting the solid oxide fuel cell and the power source are provided.
The deterioration preventing means cuts and opens an external load from the solid oxide fuel cell via the first disconnector and connects the power source to the solid oxide fuel cell via the second disconnector. The fuel cell system according to any one of claims 1 to 8, wherein A power source for reducing the anode of the solid oxide fuel cell and a second disconnector for connecting and disconnecting the solid oxide fuel cell and the power source are provided.
The deterioration prevention means connects an external load to the solid oxide fuel cell via the first disconnector and connects the power source to the solid oxide fuel cell via the second disconnector. The fuel cell system according to claim 1, wherein: The fuel electrode of the solid oxide fuel cell is provided with a feeder for feeding a reducing gas for reducing this,
The deterioration preventing means is characterized in that the external load is cut off from the solid oxide fuel cell via the first disconnector and the reducing gas is supplied to the fuel electrode via the feeder. The fuel cell system according to any one of claims 1 to 6. A solid oxide fuel cell has a cell in which a fuel electrode and an air electrode are stacked on both sides of an electrolyte, and includes a cell heater for heating the cell and a heating source for the cell heater. Provided,
The cell heating means for heating the cell heater by a heating source when the deterioration prevention means prevents the deterioration of the solid oxide fuel cell. 2. The fuel cell system according to item 1. A fuel reformer for reforming the raw fuel to be supplied to the anode of the solid oxide fuel cell is provided, and a reformer heater for heating the fuel reformer, and this A heating source for the reformer heater,
2. The reformer heating means for heating the reformer heater by a heating source when the deterioration prevention means prevents the deterioration of the solid oxide fuel cell. The fuel cell system according to any one of -12. The solid oxide fuel cell has a plurality of cell stacks in which cells on which fuel electrodes and air electrodes are stacked are stacked on both sides of an electrolyte.
The deterioration prevention determination means determines whether any cell stack starts to deteriorate based on the prevention determination reference information,
The fuel cell system according to any one of claims 1 to 13, wherein the deterioration prevention means prevents the deterioration of the cell stack determined by the deterioration prevention determination means. The degradation recovery determination means determines whether any cell stack has already deteriorated based on the recovery criterion information,
The fuel cell system according to any one of claims 1 to 14, wherein the deterioration recovery means recovers the deterioration of the cell stack determined to have already deteriorated by the deterioration recovery determination means. There is a solid oxide fuel cell that generates power by separating and flowing two kinds of power generation gas between a fuel electrode and an air electrode stacked on both sides of an electrolyte, and this solid oxide fuel cell A power generation method using a fuel cell system for supplying power to an external load connected to
Based on the preventive criteria information for preventing the deterioration of the solid oxide fuel cell, it is determined whether or not the solid oxide fuel cell starts to deteriorate, and the solid oxide fuel cell is determined to deteriorate A power generation method using a fuel cell system characterized by preventing deterioration of the solid oxide fuel cell.

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