JP2010225284A - Operation method of indirect interior reforming type solid oxide fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation method of an indirect interior reforming type SOFC system capable of preventing lack of heating of a reformer at the time of power generation and standby of power generation. <P>SOLUTION: The operation method of the indirect interior reforming type SOFC system at the time of power generation or standby of power generation, includes a reformer equipped with a reforming catalyst layer, an SOFC, an electric heater heating the reforming catalyst layer and containing a plurality of resistors capable of conducting independently, a plurality of temperature detecting means for detecting a temperature of a plurality of sites having a different phase of the reforming catalyst layer respectively, and a heater control means capable of selectively conducting an arbitrary site and the number of resistors among the plurality of the resistors based on the temperature detected by the temperature detecting means, and the reformer is arranged at a position capable of receiving heat from the SOFC. Furthermore, the operation method includes a heat assist process compensating lack of heat of the reforming catalyst layer by conducting at least one or more resistors selected from the plurality of resistors, with the use of the heater control means, and based on the temperature detected by the temperature detecting means. <P>COPYRIGHT: (C)2011,JPO&INPIT

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 generated. 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.

  In an indirect internal reforming SOFC, heat required for reforming can be provided by exhaust heat of SOFC during power generation such as rated operation or partial load operation or during power generation standby. However, there is a possibility that the reforming heat is insufficient due to load fluctuations, disturbances, and the like. In this case, the reforming becomes insufficient, and the SOFC downstream of the reformer may be adversely affected. In particular, when higher-order hydrocarbons such as kerosene are used, if unreformed higher-order hydrocarbons flow out of the reformer, the operating temperature of SOFC is usually as high as 550 to 1000 ° C. May deteriorate. In such a case, it is desirable to make use of heating means such as an electric heater to assist the reformer with heat, that is, to supplement the heat of the reformer by assisting heating of the reformer. It is.

  The time of standby for power generation means that the indirect internal reforming SOFC system has completed the start-up process, and the temperature of the SOFC detected by the SOFC temperature detection means 8 is a temperature at which power generation is possible by the power generation control means (not shown). Although it is judged, it represents a state where power is not transmitted to the outside of the indirect internal reforming SOFC system. It does not matter whether the power consumed by the indirect internal reforming SOFC system at this time is generated by the SOFC.

  During power generation, the indirect internal reforming SOFC system completes the start-up process, and the temperature of the SOFC detected by the SOFC temperature detection means 8 is the temperature at which the SOFC can generate power by the power generation control means (not shown). This represents a state where power is transmitted to the outside of the indirect internal reforming SOFC system. It does not matter whether the power consumed by the indirect internal reforming SOFC system at this time is generated by the SOFC.

  In addition, as the system operation becomes longer, the catalyst activity deteriorates, so the reformer temperature distribution changes. For example, in the case of a steam reforming reaction having an endothermic reaction, it is known that the endothermic point shifts to the downstream side of the reformer as the system operation becomes longer. Even during such long-term operation, the heat assist using heating means such as an electric heater mounted on the reformer can avoid the adverse effects due to insufficient reforming, making the indirect internal SOFC system more effective. It becomes possible to operate stably and for a long time. When performing heat assist of the reformer, the location where the heat assist is required and the amount of heat required vary depending on the operation time and the operation state.

  An object of the present invention is to provide a method of operating an indirect internal reforming SOFC system that can easily prevent insufficient reformer heating during power generation and power generation standby.

  The present invention provides the following indirect internal reforming SOFC system and its operation method.

1) a reformer having a reforming catalyst layer for producing reformed gas from a hydrocarbon-based fuel;
A solid oxide fuel cell that generates power using the reformed gas obtained by the reformer;
An electric heater for heating the reforming catalyst layer, 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,
Heater control means capable of selectively energizing any number and number of resistors among the plurality of resistors based on the temperature detected by the temperature detecting means;
Have
The reformer is disposed at a position where heat can be received from the solid oxide fuel cell;
An indirect internal reforming type solid oxide fuel cell system operation method during power generation or during power generation standby,
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. Of an indirect internal reforming type solid oxide fuel cell system having a heat assist process to compensate for the above.

2) The heater control means can variably control the energization amount to each of the plurality of resistors.
The method according to 1), wherein, in the thermal assist step, the energization amount is variably controlled when one or more of the plurality of resistors are selected and energized.

3) The indirect internal reforming solid oxide fuel cell system comprises:
A combustion region for burning anode off-gas discharged from the solid oxide fuel cell;
A housing that houses the reformer, the solid oxide fuel cell, and the combustion region;
The reformer is disposed at a position capable of receiving combustion heat generated in the combustion region;
The method according to 1) or 2).

  The present invention provides a method for operating an indirect internal reforming SOFC system that can easily prevent insufficient reformer heating during power generation and power generation standby.

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 which can apply 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 an indirect internal reforming SOFC system to which the present invention can be applied. 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 on / off the energization of such wires and resistors, or heater control means capable of controlling the energization amount of such wires and resistors can be used (about 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.

  In an indirect internal reforming SOFC, heat required for reforming can be provided by exhaust heat of the SOFC during power generation such as during rated operation and partial load operation or during power generation standby. However, exhaust heat from the SOFC may decrease due to load fluctuations, disturbances, etc., and the reforming heat may be insufficient. In this case, reforming may be insufficient, and the SOFC downstream of the reformer may be adversely affected. is there. In particular, when using higher order hydrocarbons such as kerosene, if the higher order hydrocarbons are not sufficiently reformed in the reforming process and unreformed higher order hydrocarbons flow out from the reformer outlet, the high temperature hydrocarbons Therefore, the performance of the SOFC in the SOFC deteriorates due to carbon deposition. In such a case, the electric heater 4 mounted on the reformer provides thermal assistance to any part of the reformer to compensate for the heat shortage of the reformer, thereby avoiding adverse effects on the SOFC downstream of the reformer. In addition, stable operation can be continued.

  Further, the reformer temperature distribution changes because the catalytic activity of the reforming catalyst deteriorates with the long-term operation of the system. For example, in the case of steam reforming having an endothermic reaction, it is known that the endothermic point shifts to the rear stage of the reformer as the catalytic activity decreases. Even in the long-term operation of such a system, the heater control means 6 determines the location where the heat assist of the reformer is necessary and the amount of heat based on the signal from the reformer temperature detection means 5, and the heat assist is efficiently performed. By performing, stable operation can be continued.

[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 fuel such as methane, ethane, propane, butane, natural gas, LPG (liquefied petroleum gas), city gas, gasoline, naphtha, kerosene, light oil, etc., alcohol such as methanol and ethanol, ether 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]
It is effective to perform the heat assist process in the reforming catalyst layer during power generation of the indirect internal reforming SOFC. For example, even when there is a load change (when increasing or decreasing the amount of power generated by SOFC) or when there is a disturbance, the reformer catalyst layer can be heated well by performing a heat assist process in the reforming catalyst layer. Can do.

  For example, in order to increase the amount of heat required for the reformer when the load fluctuates, particularly when the load is increased, the following operation may be considered. That is, the amount of reforming material supplied is increased, the amount of reformed gas generated by the reformer is increased, the amount of anode off-gas discharged from the fuel cell is increased, and the amount of heat generated in the combustion region (combustion heat) is reduced. increase. However, in such a method, the amount of heat required in the reformer is insufficient between the time when the reformed fuel is increased and the amount of heat generated in the combustion region increases, and the unreformed reformed fuel is heated to a high temperature. It is supplied to the SOFC in a state, and there is a possibility of having a fatal effect on the SOFC. In order to avoid such a situation, the temperature state of the reforming catalyst layer is detected by the reformer temperature detection means mounted on the reformer when the load fluctuates, and a part having a relatively low temperature due to insufficient heating is selected. It is effective to perform a heat assist step of heating automatically. Specifically, the temperature state of the reforming catalyst layer is detected by the reformer temperature detection means mounted on the reformer, and the detected reforming catalyst layer temperature is sent as a signal to the heater control means. The heater control means uses these signals to control the output location and load amount (a resistor to be energized and its energization amount) of the electric heater for heat assist mounted on the reformer, and to arbitrarily change the reformer A heat assist process is performed to compensate for the lack of heat at the place. By performing the heat assist step of the reforming catalyst layer, the load (SOFC electrical output) can be increased quickly without causing heat shortage of the reformer.

  The heat assist process in the reforming catalyst layer can be stopped at a stage where the amount of heat required for the reformer can be covered by the increased amount of combustion heat of the anode off gas. This process is automatically performed by a reformer temperature detecting means and a heater control means mounted on the reformer.

  Further, as the catalyst activity deteriorates with the long-term operation of the system, the reformer temperature distribution changes. For example, in the case of steam reforming having an endothermic reaction, it is known that the endothermic point shifts to the rear stage of the reformer as the catalytic activity decreases. In response to this, for example, the amount of reformed fuel supplied is increased, the amount of reformed gas generated by the reformer is increased, the amount of anode off-gas discharged from the fuel cell is increased, and the combustion region is increased. It is conceivable to increase the amount of generated heat (combustion heat). However, since this method raises the temperature of the entire reforming catalyst layer, excessive thermal energy is applied to avoid unreforming in the reforming catalyst layer, which is not preferable from the viewpoint of efficiency.

  Even during the long-term operation of such a system, the temperature state of the reforming catalyst layer is detected by the reformer temperature detecting means mounted on the reformer, and a portion having a relatively low temperature is selectively heated due to insufficient heating. It is effective to perform a heat assist process. Specifically, the temperature state of the reforming catalyst layer is detected by the reformer temperature detection means mounted on the reformer, and the detected reforming catalyst layer temperature is sent as a signal to the heater control means. The heater control means uses these signals to control the output location and load amount (a resistor to be energized and its energization amount) of the electric heater for heat assist mounted on the reformer, and to arbitrarily change the reformer A heat assist process is performed to compensate for the lack of heat at the place. According to such a method, it is possible to carry out a heat assist process according to the catalytic activity of the reforming catalyst layer during long-term operation, and heating of the reforming catalyst layer should be kept to the minimum necessary. Therefore, it is also excellent in terms of thermal efficiency.

  When operating the system, it may be necessary to temporarily stop power transmission outside the system due to a problem on the system side when the load on the customer becomes extremely low or to enter a power generation standby state. . At this time, in order to increase the amount of heat required for the reformer when there is a disturbance, the following operation may be considered. That is, the amount of reforming material supplied is increased, the amount of reformed gas generated by the reformer is increased, the amount of anode off-gas discharged from the fuel cell is increased, and the amount of heat generated in the combustion region (combustion heat) is reduced. increase. However, in such a method, the amount of heat required in the reformer is insufficient between the time when the reformed fuel is increased and the amount of heat generated in the combustion region increases, and the unreformed reformed fuel is heated to a high temperature. It is supplied to the SOFC in a state, and there is a possibility of having a fatal effect on the SOFC. In order to avoid such a situation, when there is a disturbance, the temperature state of the reforming catalyst layer is detected by the reformer temperature detecting means mounted on the reformer, and the temperature is relatively low due to insufficient heating. It is effective to perform a heat assist step of selectively heating the heat. Specifically, the temperature state of the reforming catalyst layer is detected by the reformer temperature detection means mounted on the reformer, and the detected reforming catalyst layer temperature is sent as a signal to the heater control means. The heater control means uses these signals to control the output location and load amount (a resistor to be energized and its energization amount) of the electric heater for heat assist mounted on the reformer, and to arbitrarily change the reformer A heat assist process is performed to compensate for the lack of heat at the place. By performing the heat assisting process of the reforming catalyst layer, the power generation standby state can be stably maintained without causing the reformer to run out of heat.

  As described above, the present invention provides a method for operating an indirect internal reforming SOFC system that can stably and appropriately maintain the temperature of the reformer during power generation and during power generation standby.

  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 layer 4 ... Electric heater 5 for heat assistance ... Reforming catalyst layer temperature detection means 6 ... Heater control means 7 ... Heater power supply 8 ... SOFC temperature detection means 9 ... Combustion region 10 ... Housing

Claims (3)

A reformer comprising a reforming catalyst layer for producing a reformed gas from a hydrocarbon-based fuel;
A solid oxide fuel cell that generates power using the reformed gas obtained by the reformer;
An electric heater for heating the reforming catalyst layer, 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,
Heater control means capable of selectively energizing any number and number of resistors among the plurality of resistors based on the temperature detected by the temperature detecting means;
Have
The reformer is disposed at a position where heat can be received from the solid oxide fuel cell;
An indirect internal reforming type solid oxide fuel cell system operation method during power generation or during power generation standby,
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. Of an indirect internal reforming type solid oxide fuel cell system having a heat assist process to compensate for the above. The heater control means is capable of variably controlling the energization amount to each of the plurality of resistors.
2. The method according to claim 1, wherein, in the heat assist step, the energization amount is variably controlled when one or more of the plurality of resistors are selected and energized. The indirect internal reforming solid oxide fuel cell system is
A combustion region for burning anode off-gas discharged from the solid oxide fuel cell;
A housing that houses the reformer, the solid oxide fuel cell, and the combustion region;
The reformer is disposed at a position capable of receiving combustion heat generated in the combustion region;
The method according to claim 1 or 2.

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