JP5307592B2 - Operation method of indirect internal reforming type solid oxide fuel cell system - Google Patents

Description

  The present invention relates to an indirect internal reforming solid oxide fuel cell system including an indirect internal reforming solid oxide fuel cell having a reformer in the vicinity of the fuel cell.

  Solid oxide fuel cells (Solid Oxide Fuel Cells; hereinafter referred to as SOFC in some cases) are usually generated by reforming hydrocarbon fuels (reforming raw materials) such as kerosene and city gas in a reformer. The hydrogen-containing gas (reformed gas) is supplied. In SOFC, power is generated by electrochemically reacting the reformed gas and air. The SOFC is usually operated at a high temperature of about 550 ° C to 1000 ° C.

  Various reactions such as steam reforming and partial oxidation reforming are used for the reforming. Both require a certain temperature or higher. Therefore, an indirect internal reforming SOFC has been developed in which a reformer is installed in the vicinity of the SOFC (a position that receives heat radiation from the SOFC), and the reformer is heated by radiant heat from the SOFC (see Patent Document 1). ). Further, in the indirect internal reforming SOFC, combustible anode off-gas (gas discharged from the SOFC anode) is combusted in the indirect internal reforming SOFC casing (module container), and this combustion heat is burned. A reformer is heated as a heat source (see Patent Document 2).

JP 2002-358997 A JP 2004-319420 A

  Thus, in the indirect internal reforming SOFC, the reformer is heated using the SOFC as a heat source.

  However, since the heat of the SOFC cannot be expected at the time of starting the indirect internal reforming SOFC, it is required to raise the temperature of the catalyst to a temperature at which the reforming catalyst exhibits activity by means other than the SOFC. In order to raise the temperature of the reformer, a reforming reaction with heat generation such as a partial oxidation reforming reaction or an autothermal reforming reaction is performed in the reformer, the reformed gas is supplied to the SOFC, and the anode off-gas is combusted. It is possible. However, the reformed gas generated by the partial oxidation reforming reaction or the autothermal reforming reaction includes non-combustion components having a large heat capacity such as nitrogen, carbon dioxide, and steam. For this reason, even if the reformed gas is burned in the combustion region, a desired temperature may not be obtained, or combustion may not be maintained in the combustion region.

Further, when the indirect internal reforming SOFC is stopped, in order to suppress the oxidative deterioration of the SOFC, the SOFC temperature is lowered while the reducing gas (reformed gas containing hydrogen) is supplied to the SOFC until the SOFC reaches a predetermined temperature. It is desirable. At this time, in order to generate a reformed gas that does not contain unreformed fuel, it is desired to maintain a predetermined amount of heat supply to the reformer. On the other hand, in order to effectively cool the SOFC, it is desired to reduce the supply amount of the reformed gas that becomes a relatively high temperature. That is, it is desired to reliably reform while reducing the amount of the reformed gas. In such a case, there is a possibility that heating of the reformer cannot be performed satisfactorily.
Thus, in an excessive state such as when the indirect internal reforming SOFC is started and stopped, the reformer is insufficiently heated, and as a result, the reformer cannot be heated well. There are cases where reliable reforming cannot be performed.

An object of the present invention, during startup, even more during stop, is that it is possible to prevent insufficient heating of the reformer provide easy indirect internal reforming SOFC system operating method.

The present invention, a method of operating a next indirect internal reforming SOFC system is provided.

1) a reformer having a reforming catalyst layer for producing reformed gas from a hydrocarbon-based fuel;
A solid oxide fuel cell which generates electric power using the reformed gas obtained in the reformer,
An electrical heater for heating the reforming catalyst layer, and the electric heater including a plurality of resistors that can be energized independently,
A plurality of temperature detecting means for detecting the temperatures of a plurality of different locations of the reforming catalyst layer,
On the basis of the temperature detected by the detection means temperature, a heater control means capable of selectively energizing the arbitrary location and number of resistors of the plurality of resistors, said plurality of resistors Heater control means capable of variably controlling the energization amount to each of the
A combustion region for burning anode off-gas discharged from the solid oxide fuel cell;
A housing for housing the reformer, the solid oxide fuel cell and the combustion region;
I have a,
The reformer is disposed at a position where heat can be received from the solid oxide fuel cell, and is disposed at a position where heat from combustion generated in the combustion region can be received.
A method for operating an indirect internal reforming solid oxide fuel cell system, comprising:
The reforming catalyst layer is capable of self-thermal reforming hydrocarbon fuel,
When starting up an indirect internal reforming solid oxide fuel cell system,
A step of detecting the temperature state of the reforming catalyst layer and selectively heating a portion having a relatively low temperature due to insufficient heating, based on the temperature detected by the temperature detection unit using the heater control unit. A heat assist step for compensating for the heat shortage of the reforming catalyst layer by selecting and energizing one or more of the plurality of resistors, and
a) When the temperature of the reforming catalyst layer becomes equal to or higher than the self-thermal reforming reaction start temperature of the hydrocarbon fuel, the hydrocarbon fuel is self-heat reformed by the reformer, and the resulting reformed gas is Introducing into the solid oxide fuel cell and combusting anode off gas in the combustion region;
The heat assist step is performed in step a.
A method for operating an indirect internal reforming solid oxide fuel cell system.

2 ) The reforming catalyst layer is capable of partial oxidation reforming of hydrocarbon fuel,
Prior to step a,
b) When the temperature of the reforming catalyst layer becomes equal to or higher than the partial oxidation reforming reaction start temperature of the hydrocarbon fuel, the hydrocarbon fuel is partially oxidized and reformed by the reformer, and the resulting reformed gas is Introducing into the solid oxide fuel cell and combusting anode off gas in the combustion region;
In step b, the heat assist step is performed.
1 ) The method described.

3 ) The reforming catalyst layer is capable of steam reforming the hydrocarbon fuel,
After step a,
c) When the temperature of the reforming catalyst layer becomes equal to or higher than the steam reforming reaction start temperature of the hydrocarbon fuel, the reforming device steam reforms the hydrocarbon fuel and converts the resulting reformed gas into the solid fuel. Introducing into the oxide fuel cell and burning the anode off gas in the combustion region;
In step c, the heat assist step is performed.
2 ) The method described.

4) indirect internal reforming-type solid oxide fuel cell system when stopping,
i) Stop the power generation of the solid oxide fuel cell and reduce the flow rate of the hydrocarbon-based fuel supplied to the reformer to supply a relatively small flow rate of hydrocarbon-based fuel to the reformer. , have to reduce the firing rate of the anode off-gas in the solid oxide fuel cell for supplying the reformed gas amount was reduced by the combustion region, step of cooling the solid oxide fuel cell and,
ii) after the solid oxide fuel cell is lowered to a temperature that does not require the reformed gas, comprising the step of stopping the supply of the hydrocarbon-based fuel supplied to the reformer in this order,
The heat assist step is performed in step i.
The method according to any one of 1) to 3) .

The present invention, during startup, even more during stop, easy indirect internal reforming SOFC system method of operation to prevent insufficient heating of the reformer is provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the outline | summary about one form of the indirect internal reforming type solid oxide fuel cell system of this invention. It is the schematic diagram which showed the reformer part of the system shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

[Indirect internal reforming SOFC]
FIG. 1 schematically shows an embodiment of the indirect internal reforming SOFC system of the present invention. FIG. 2 schematically shows the reformer part of the system.

  The indirect internal reforming SOFC has a reformer 2 that produces reformed gas from hydrocarbon fuel. The reformer 2 includes a reforming catalyst layer 3 therein. The indirect internal reforming SOFC has a SOFC 1 that generates power using the reformed gas obtained in the reformer 2, and has a combustion region 9 in which anode off-gas discharged from the SOFC 1 is burned. The reformer 2 is disposed at a position where heat can be received from the SOFC. The indirect internal reforming SOFC has a housing 10 that houses the reformer, the SOFC, and the combustion region. The reformer is arranged at a position where it can receive the combustion heat generated in the combustion region.

  A hydrocarbon fuel is supplied to the reformer 2. At this time, oxygen-containing gas (such as air) and water vapor are also supplied to the reformer as necessary. The reformed gas obtained from the reformer 2 is supplied to the anode of the SOFC 1. The anode off gas discharged from the anode can be combusted in the combustion region.

  An electric heater 4 for heating the reforming catalyst layer 3 is mounted on the reformer 2. The electric heater 4 includes a plurality of resistors. In the figure, nine resistors 4-1 to 4-9 are provided (reference numerals are omitted for the resistors 4-3 to 4-8). The plurality of resistors can be independently energized.

  The electric heater 4 has a mechanism capable of selectively energizing (loading) an arbitrary place and an arbitrary number of resistors among the plurality of resistors. This mechanism can be formed by appropriate wiring. For example, as shown in the figure, this mechanism can be formed by wirings connected to each resistor independently. Heater control means capable of switching to turn on / off energization to such wiring and resistor, or heater control means capable of controlling the energization amount to such wiring and resistor can be used (about the heater control means). Will be described later).

  For example, a resistance wire can be used as the resistor.

  The reformer 2 is provided with a plurality of temperature detecting means (reforming catalyst layer temperature detecting means) 5 for detecting temperatures at different positions of the reforming catalyst layer. In the figure, nine temperature detection means 5-1 to 5-9 are provided (reference numerals are omitted for the temperature detection means 5-3 to 5-8).

  As the temperature detection means, a known temperature sensor such as a thermocouple that can detect the temperature of the reforming catalyst layer can be appropriately used.

  Based on the temperature detected by the temperature detection means, the heater control means 6 can selectively energize any location and number of resistors among the plurality of resistors. That is, the heater control means performs control such that a part or all of the plurality of resistors are selected, the selected resistors are energized, and the unselected resistors are not energized. Thereby, when there is a partial lack of heat in the reforming catalyst layer, a portion where the heat is insufficient can be selectively heated to compensate for the partial lack of heat. That is, even when the reforming catalyst layer is heated by a heat source other than the heater 4, even if the heating is partially insufficient, the portion can be selectively heated to compensate for the insufficient heat. it can.

  The heater control means can simply turn on and off the energization of each resistor, but the ability to variably control the energization can respond to changes in the load amount and disturbance of the reformer, and the power consumption of the heater It is preferable from the viewpoint of reducing the amount.

  Specifically, the detected reforming catalyst layer temperature is sent to the heater control means 6 as a signal. The heater control means 6 uses these signals to control the resistor to be energized and the energization amount among the resistors 4-1 to 4-9 of the electric heater 4 mounted on the reformer 2.

  Hereinafter, supplementing the heat shortage of the reforming catalyst layer in some cases is referred to as “thermal assist”. An electric heater that performs heat assist may be referred to as a heat assist electric heater.

  As the heater control means, known control means used for control in an indirect internal reforming SOFC or SOFC system such as a control computer, a sequencer, and an inverter can be appropriately used.

  As described above, the indirect internal reforming SOFC system according to the present invention is equipped with a heat assist electric heater in the reformer, and this heater includes a group of a plurality of resistors that can be energized independently. can do. Further, the indirect internal reforming SOFC system has a mechanism that can selectively apply a load to any number and number of resistors among the plurality of resistors. Accordingly, it is possible to perform an operation that performs heat assist with a heater that is appropriate and consumes less power while observing the temperature state of the catalyst.

  For example, in starting operation or stopping operation, when the reforming catalyst layer is heated by performing combustion in the reforming catalyst layer, the combustion is completed in the upstream portion of the catalyst layer and the combustion is performed in the downstream portion of the catalyst layer. Sometimes it does n’t happen. In such a case, the upstream part of the catalyst layer where combustion occurs is not subjected to thermal assistance by the electric heater, but the downstream part where combustion does not occur is selectively subjected to thermal assistance by the electric heater, and the starting is started. Or it becomes possible to reduce the heater power consumption at the time of a stop.

[Hydrocarbon fuel]
As the hydrocarbon-based fuel, as a reformed gas raw material, a compound known from the field of SOFC, containing carbon and hydrogen (may contain other elements such as oxygen) or a mixture thereof, or a mixture thereof may be used as appropriate. And compounds having carbon and hydrogen in the molecule such as hydrocarbons and alcohols can be used. For example, hydrocarbon fuels such as methane, ethane, propane, butane, natural gas, LPG (liquefied petroleum gas), city gas, gasoline, naphtha, kerosene, light oil, etc., alcohols such as methanol and ethanol, ethers such as dimethyl ether, etc. is there.

  Of these, kerosene and LPG are preferred because they are readily available. Moreover, since it can be stored independently, it is useful in an area where the city gas line is not widespread. Furthermore, SOFC power generators using kerosene or LPG are useful as emergency power supplies. In particular, kerosene is preferable because it is easy to handle.

  The hydrocarbon fuel used as the reforming raw material can be supplied to the reformer after being desulfurized as necessary. When the hydrocarbon fuel is a liquid, it can be appropriately vaporized and then supplied to the reformer.

[Reformer]
The reformer produces a reformed gas containing hydrogen from a hydrocarbon fuel.

  In the reformer, any of steam reforming, partial oxidation reforming, and autothermal reforming accompanied by partial oxidation reaction in the steam reforming reaction may be performed.

  The reformer is appropriately equipped with a steam reforming catalyst having steam reforming ability, a partial oxidation reforming catalyst having partial oxidation reforming ability, and a self-thermal reforming catalyst having both partial oxidation reforming ability and steam reforming ability. Can be used.

  As the structure of the reformer, a structure known as a reformer can be appropriately adopted. For example, it is possible to have a structure having a region for accommodating the reforming catalyst in a sealable container and having an inlet for fluid necessary for reforming and an outlet for reforming gas.

  The material of the reformer can be appropriately selected and adopted from materials known as reformers in consideration of resistance in the use environment.

  The shape of the reformer can be an appropriate shape such as a rectangular parallelepiped or a circular tube.

  Supply hydrocarbon-based fuel (pre-vaporized if necessary), water vapor, and oxygen-containing gas such as air, if necessary, individually or appropriately mixed to the reformer (reforming catalyst layer) can do. The reformed gas is supplied to the anode of the SOFC.

  The reformed gas obtained from the reformer is supplied to the anode of the SOFC. On the other hand, an oxygen-containing gas such as air is supplied to the cathode of the SOFC. During power generation, the SOFC generates heat with power generation, and the heat is transmitted from the SOFC to the reformer by radiant heat transfer or the like. Thus, the SOFC exhaust heat is used to heat the reformer. Gas exchange and the like are appropriately performed using piping or the like.

[SOFC]
As the SOFC, a known SOFC can be appropriately selected and employed. In the SOFC, oxygen ion conductive ceramics or proton ion conductive ceramics are generally used as an electrolyte.

  The SOFC may be a single cell, but in practice, a stack in which a plurality of single cells are arranged (in the case of a cylindrical type, sometimes referred to as a bundle, but the stack in this specification includes a bundle) is preferable. Used. In this case, one or more stacks may be used.

  The shape of the SOFC is not limited to the cubic stack, and an appropriate shape can be adopted.

[Case]
As the casing (module container), an appropriate container capable of accommodating the SOFC, the reformer, and the combustion region can be used. As the material, for example, an appropriate material having resistance to the environment to be used, such as stainless steel, can be used. The container is appropriately provided with a connection port for gas exchange and the like.

  The module container is preferably airtight so that the interior of the module container does not communicate with the outside (atmosphere).

(Combustion area)
The combustion region is a region where the anode off gas discharged from the anode of the SOFC can be combusted. For example, the anode outlet can be opened in the housing, and the space near the anode outlet can be used as a combustion region. This combustion can be performed using, for example, a cathode off gas as the oxygen-containing gas. For this purpose, the cathode outlet can be opened in the housing.

  In order to burn the anode off gas, ignition means such as an igniter can be appropriately used.

[Arrangement of reformer]
In the indirect internal reforming SOFC, the reformer is disposed at a position where heat can be received from the SOFC. For this reason, the reformer can be disposed at a position that receives heat radiation from the SOFC, but it is preferable from the viewpoint of thermal energy loss to place the reformer at a position that receives the most heat radiation.

  The reformer is preferably disposed at a position where it can receive the combustion heat generated in the combustion region. For this purpose, the reformer can be arranged at a position that receives heat radiation from the combustion region. At this time, it is preferable not to arrange a shield between the combustion region and the reformer. That is, it is preferable that the combustion region and the reformer face each other without sandwiching the shield. However, necessary piping and the like are appropriately arranged. It is preferable to arrange the reformer and the combustion region as close as possible.

[Reforming catalyst]
Any of the steam reforming catalyst, the partial oxidation reforming catalyst, and the autothermal reforming catalyst that can be used in the reformer can be a known non-noble metal or noble metal reforming catalyst.

[Other equipment]
Known components of the indirect internal reforming SOFC system can be appropriately provided as necessary. Specific examples include a vaporizer for vaporizing liquid, a pump for pressurizing various fluids, a pressure increasing means such as a compressor and a blower, a valve for adjusting the flow rate of the fluid, or for blocking / switching the flow of the fluid. Such as flow rate control means, flow path blocking / switching means, heat exchanger for heat exchange / recovery, condenser for condensing gas, heating / heat-retaining means for externally heating various devices with steam, etc., hydrocarbon system Fuel (reforming raw materials) and combustion fuel storage means, instrumentation air and electrical systems, control signal systems, control devices, output and power electrical systems, desulfurization to reduce the concentration of sulfur in the fuel Such as a vessel.

[Indirect internal reforming SOFC system operation method]
The operation method of the indirect internal reforming SOFC system of the present invention is a method of starting or stopping the indirect internal reforming SOFC system,
Using the heater control means, based on the temperature detected by the temperature detection means, selecting one or more resistors among the plurality of resistors and energizing them, the reforming catalyst layer lacks heat. A heat assist process to compensate for

[Startup operation of indirect internal reforming SOFC system]
In starting up the indirect internal reforming SOFC system, the reforming catalyst layer is first heated to raise the temperature. A heating means such as an electric heater can be used for this heating. As this electric heater, a start-up heater (not shown) dedicated to start-up or a heat assist electric heater 4 can be used. Moreover, both of these can also be used together. In addition, when the hydrocarbon fuel (reformed raw material) is a gas body, the hydrocarbon fuel (reformed raw material) is supplied to the combustion region 9 via the reformer 2 and the SOFC 1, and the reformed raw material is supplied in the combustion region. The combustion heat can be used for this heating.

  Then, when the reforming catalyst layer can autothermally reform the hydrocarbon-based fuel, step a can be performed. In other words, when the temperature of the reforming catalyst layer reaches a temperature at which self-thermal reforming is possible, the reformer reforms the hydrocarbon-based fuel (reforming raw material) by self-thermal reforming, and converts the resulting reformed gas into SOFC. And the anode off gas is burned in the combustion zone.

  In addition to the hydrocarbon fuel (reforming raw material), water vapor and oxygen-containing gas (air, oxygen gas, etc.) necessary for autothermal reforming are appropriately supplied to the reformer.

  In step a, the reformer 2, particularly the reforming catalyst layer 3, is heated by heat generated by the autothermal reforming reaction and combustion heat generated in the combustion region. At this time, based on the temperature of the reforming catalyst layer detected by the reformer temperature detecting means 5 mounted on the reformer, one or more resistors among the plurality of resistors are selected and energized. Thus, the heat shortage of the reforming catalyst layer is compensated (thermal assist is performed). That is, a portion having a relatively low temperature is selectively heated due to insufficient heating. Specifically, the temperature state of the reforming catalyst layer is detected by the reformer temperature detecting means mounted on the reformer, and the detected reforming catalyst layer temperature is sent to the heater control means 6 as a signal. The heater control means uses these signals to control the output location and the load amount (the resistor to be energized and its energization amount) of the heat assist electric heater 4 mounted on the reformer, so that any reformer can be used. A heat assist process is performed to compensate for the lack of heat at the location.

  When the reforming catalyst layer can also partially oxidize and reform the hydrocarbon fuel (reforming raw material), the step b can be performed before the step a. That is, when the temperature of the reforming catalyst layer becomes equal to or higher than the partial oxidation reforming reaction start temperature of the hydrocarbon fuel (reforming raw material), the hydrocarbon fuel (reforming raw material) is partially oxidized and reformed by the reformer. Then, the obtained reformed gas is introduced into the SOFC 1 and the anode off gas is burned in the combustion region 9.

  In general, the partial oxidation reforming reaction starting temperature is lower than the autothermal reforming reaction starting temperature, and the partial oxidation reforming does not involve an endothermic reaction. Therefore, it is preferable.

  In addition to the hydrocarbon fuel (reforming raw material), an oxygen-containing gas (such as air or oxygen gas) necessary for partial oxidation reforming is appropriately supplied to the reformer.

  In step b, the reformer 2, particularly the reforming catalyst layer 3, is heated by heat generated by partial oxidation reforming and combustion heat generated in the combustion region. At this time, a heat assist step is performed in which the temperature state of the reforming catalyst layer is detected by the reformer temperature detecting means 5 mounted on the reformer, and a portion having a relatively low temperature is selectively heated due to insufficient heating. Do. That is, heat assist is also performed in step b. Specifically, the temperature state of the reforming catalyst layer is detected by the reformer temperature detecting means mounted on the reformer, and the detected reforming catalyst layer temperature is sent to the heater control means 6 as a signal. The heater control means uses these signals to control the output location and the load amount (the resistor to be energized and its energization amount) of the heat assist electric heater 4 mounted on the reformer, so that any reformer can be used. A heat assist process is performed to compensate for the lack of heat at the location.

  Since the SOFC is supplied with a relatively high temperature reformed gas, the SOFC is also heated. In addition, the SOFC can be heated by the combustion heat generated in the combustion region.

  When the reforming catalyst layer can also steam reform the hydrocarbon fuel (reforming raw material), step c can be performed after step a. That is, when the temperature of the reforming catalyst layer becomes equal to or higher than the steam reforming reaction start temperature of the hydrocarbon fuel (reforming raw material), the reformed gas obtained by steam reforming the hydrocarbon fuel with the reformer. Is introduced into the solid oxide fuel cell, and the anode off-gas is combusted in the combustion region.

  In addition to the hydrocarbon fuel (reforming raw material), steam necessary for steam reforming is appropriately supplied to the reformer. In step a, autothermal reforming is performed, so that steam and oxygen-containing gas are supplied to the reformer. Therefore, the process a can be shifted to the process c by stopping the supply of the oxygen-containing gas.

  In step c, the reformer 2, particularly the reforming catalyst layer 3 is heated by the combustion heat generated in the combustion region. Since the relatively high temperature reformed gas is supplied to the SOFC 1, the SOFC is also heated. In addition, the SOFC can be heated by the combustion heat generated in the combustion region 9. At this time, a heat assist step is performed in which the temperature state of the reforming catalyst layer is detected by the reformer temperature detecting means 5 mounted on the reformer, and a portion having a relatively low temperature is selectively heated due to insufficient heating. Do. That is, heat assist is also performed in step c. Specifically, the temperature state of the reforming catalyst layer is detected by the reformer temperature detecting means mounted on the reformer, and the detected reforming catalyst layer temperature is sent to the heater control means 6 as a signal. The heater control means uses these signals to control the output location and the load amount (the resistor to be energized and its energization amount) of the heat assist electric heater 4 mounted on the reformer, so that any reformer can be used. A heat assist process is performed to compensate for the lack of heat at the location.

  Steam reforming is a reforming method that easily increases the hydrogen concentration in the reformed gas. Therefore, it is easy to increase the hydrogen concentration in the reformed gas by the step c. On top of this, power generation by SOFC is advantageous in terms of power generation efficiency.

[Stop operation of indirect internal reforming SOFC system]
Next, an operation method at the time of stopping, that is, an operation method at the time of stopping from a state where power generation is performed by the indirect internal reforming SOFC system will be described. When the indirect internal reforming SOFC is stopped, reducing gas (reformed gas containing hydrogen) is supplied to the SOFC until the SOFC reaches a predetermined temperature in order to suppress the oxidative degradation of the SOFC, and the temperature of the SOFC is lowered. At this time, in order to generate reformed gas that does not contain unreformed fuel, it is desired to maintain a predetermined amount of heat supply to the reformer. On the other hand, in order to effectively cool the SOFC, it is necessary to reduce the supply amount of the reformed gas that is relatively high in temperature. That is, when stopping, it is required to reliably reform while reducing the amount of reformed gas. In such a case, there is a possibility that heating of the reformer cannot be performed satisfactorily. For this reason, it is desired to grasp the temperature state of the reforming catalyst layer and efficiently heat the insufficiently heated portion.

In the stop operation, steps i and ii are performed in this order. In step i, the temperature state of the reforming catalyst layer 3 is detected by the reformer temperature detecting means 5 mounted on the reformer 2, and a heat assist step of selectively heating a portion having a relatively low temperature due to insufficient heating. I do.
i) Stop the power generation of the SOFC and reduce the amount of hydrocarbon fuel supplied to the reformer to supply a relatively small flow rate of hydrocarbon fuel to the reformer, and then supply it to the SOFC The process of reducing the amount of reformed gas to reduce the amount of anode off-gas combustion in the combustion region and lowering the temperature of the indirect internal reforming SOFC.
ii) A step of stopping the supply of the hydrocarbon-based fuel supplied to the reformer after the temperature of the SOFC is lowered to a temperature that does not require the reformed gas.

  In step i, SOFC power generation is stopped and the amount of hydrocarbon fuel (reforming raw material) supplied to the reformer is reduced, so that a relatively small flow rate of hydrocarbon fuel is used as the reformer. Supply. That is, a hydrocarbon-based fuel having a flow rate (not zero) smaller than the hydrocarbon-based fuel supply amount to the reformer at the start of the stop operation is supplied to the reformer. As a result, the amount of reformed gas supplied to the SOFC is reduced (not zero), the amount of anode off-gas combustion in the combustion region is reduced (not zero), and the temperature of the indirect internal reforming SOFC is lowered.

  In step i, in order to prevent oxidative degradation of the SOFC, a relatively small flow rate of hydrocarbon-based fuel is supplied to the reformer, and reforming is performed in the reformer so that the reformed gas, which is a reducing gas, is supplied. To manufacture. Then, the temperature of the indirect internal reforming SOFC is lowered while supplying the reformed gas to the SOFC.

  In step i, oxygen-containing gas and water vapor necessary for reforming are supplied as appropriate. Note that an appropriate reforming method can be employed in step i, and any reforming method of steam reforming, autothermal reforming, or partial oxidation reforming may be employed.

  When the temperature of the indirect internal reforming SOFC is lowered, that is, in step i, a heat assist step is performed in which a portion having a relatively low temperature due to insufficient heating is selectively heated. That is, the temperature state of the reforming catalyst layer 3 is detected by the reformer temperature detecting means 5 mounted on the reformer 2, and the detected reforming catalyst layer temperature is sent as a signal to the heater control means 6. The heater control means uses these signals to control the output location and the load amount (the resistor to be energized and its energization amount) of the heat assist electric heater 4 mounted on the reformer, so that any reformer can be used. A heat assist process is implemented to compensate for the lack of heat at the location. Through the heat assist process of the reformer, the reliability of reforming can be improved, and the SOFC can be cooled effectively while maintaining the required heat quantity of the reformer.

  Then, when the temperature of the SOFC is lowered to a temperature that does not require the reformed gas, the supply of the hydrocarbon-based fuel supplied to the reformer is stopped (step ii). At this time, the heater output mounted on the reformer is stopped and the heat assist process is stopped.

  The heater control means 6 appropriately determines the temperature at which the SOFC does not require the reformed gas by the SOFC temperature detection means 8.

  As the temperature detection means, a known temperature sensor such as a thermocouple that can detect the temperature of the reforming catalyst layer can be appropriately used.

  As described above, according to the present invention, it is possible to obtain an indirect internal reforming SOFC system having a mechanism for stably and appropriately maintaining the temperature of the reformer at the time of starting and stopping. Also disclosed are methods for suitably operating it, in particular starting and stopping methods.

  The present invention can be applied to an indirect internal reforming solid oxide fuel cell system used in, for example, a stationary or moving power generator or a cogeneration system.

DESCRIPTION OF SYMBOLS 1 ... Solid oxide fuel cell 2 ... Reformer 3 ... Reforming catalyst 4 ... Heat heater 5 for heat assist ... Reforming catalyst layer temperature detection means 6 ... Heater control means 7 ... Heater power supply 8 ... SOFC temperature detection means 9 ... combustion region 10 ... casing

Claims (4)

A reformer comprising a reforming catalyst layer for producing a reformed gas from a hydrocarbon-based fuel;
A solid oxide fuel cell which generates electric power using the reformed gas obtained in the reformer,
An electrical heater for heating the reforming catalyst layer, and the electric heater including a plurality of resistors that can be energized independently,
A plurality of temperature detecting means for detecting the temperatures of a plurality of different locations of the reforming catalyst layer,
On the basis of the temperature detected by the detection means temperature, a heater control means capable of selectively energizing the arbitrary location and number of resistors of the plurality of resistors, said plurality of resistors Heater control means capable of variably controlling the energization amount to each of the
A combustion region for burning anode off-gas discharged from the solid oxide fuel cell;
A housing for housing the reformer, the solid oxide fuel cell and the combustion region;
I have a,
The reformer is disposed at a position where heat can be received from the solid oxide fuel cell, and is disposed at a position where heat from combustion generated in the combustion region can be received.
A method for operating an indirect internal reforming solid oxide fuel cell system, comprising:
The reforming catalyst layer is capable of self-thermal reforming hydrocarbon fuel,
When starting up an indirect internal reforming solid oxide fuel cell system,
A step of detecting the temperature state of the reforming catalyst layer and selectively heating a portion having a relatively low temperature due to insufficient heating, based on the temperature detected by the temperature detection unit using the heater control unit. A heat assist step for compensating for the heat shortage of the reforming catalyst layer by selecting and energizing one or more of the plurality of resistors, and
a) When the temperature of the reforming catalyst layer becomes equal to or higher than the self-thermal reforming reaction start temperature of the hydrocarbon fuel, the hydrocarbon fuel is self-heat reformed by the reformer, and the resulting reformed gas is Introducing into the solid oxide fuel cell and combusting anode off gas in the combustion region;
The heat assist step is performed in step a.
A method for operating an indirect internal reforming solid oxide fuel cell system. The reforming catalyst layer is capable of partially oxidizing and reforming a hydrocarbon-based fuel;
Prior to step a,
b) When the temperature of the reforming catalyst layer becomes equal to or higher than the partial oxidation reforming reaction start temperature of the hydrocarbon fuel, the hydrocarbon fuel is partially oxidized and reformed by the reformer, and the resulting reformed gas is Introducing into the solid oxide fuel cell and combusting anode off gas in the combustion region;
The method of claim 1, wherein performing the thermal assist step in step b. The reforming catalyst layer is capable of steam reforming the hydrocarbon-based fuel;
After step a,
c) When the temperature of the reforming catalyst layer becomes equal to or higher than the steam reforming reaction start temperature of the hydrocarbon fuel, the reforming device steam reforms the hydrocarbon fuel and converts the resulting reformed gas into the solid fuel. Introducing into the oxide fuel cell and burning the anode off gas in the combustion region;
The method according to claim 2 , wherein the heat assist step is performed in step c. The indirect internal reforming-type solid oxide fuel cell system when stopping,
i) Stop the power generation of the solid oxide fuel cell and reduce the flow rate of the hydrocarbon-based fuel supplied to the reformer to supply a relatively small flow rate of hydrocarbon-based fuel to the reformer. , have to reduce the firing rate of the anode off-gas in the solid oxide fuel cell for supplying the reformed gas amount was reduced by the combustion region, step of cooling the solid oxide fuel cell and,
ii) after the solid oxide fuel cell is lowered to a temperature that does not require the reformed gas, comprising the step of stopping the supply of the hydrocarbon-based fuel supplied to the reformer in this order,
The heat assist step is performed in step i.
The method according to claim 1 .

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