JP2011210648A - Indirect interior reforming type solid oxide fuel cell system and operation method for the same - Google Patents

Abstract

An indirect internal reforming solid oxide fuel cell system capable of improving start-up reliability and safety and an operation method thereof.
An indirect internal reforming SOFC system 10 includes a reformer 1 having a reforming catalyst layer that generates a reformed gas using a hydrocarbon-based fuel, and a reformed gas obtained by the reformer 1. SOFC 3 that generates electricity using, combustion region 4 that combusts anode off gas discharged from SOFC 3, and reformer 1, SOFC 3, and housing 7 that accommodates combustion region 4, and is generated in combustion region 4 The reformer 1 is disposed at a position where the combustion heat can be received. This indirect internal reforming SOFC system 10 includes a reforming catalyst layer post-stage heater 2 for heating the reforming catalyst layer post-stage 11x, a temperature detection means 5 for detecting the temperature of the reforming catalyst layer post-stage 11x, and a temperature detection means 5 Heater control means 6 for controlling the operation of the reforming catalyst layer latter stage heater 2 based on the temperature detected in step (b).
[Selection] Figure 2

Description

  The present invention relates to an indirect internal reforming solid oxide fuel cell system having a reformer in the vicinity of a fuel cell, and an operation method thereof.

  Normally, solid oxide fuel cells (Solid Oxide Fuel Cells: hereinafter referred to as “SOFC”) are generated by reforming hydrocarbon fuels (reforming raw materials) such as kerosene and city gas with a reformer. The hydrogen-containing gas (reformed gas) is supplied. The SOFC generates electricity by electrochemically reacting the reformed gas and air. Such 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. In any of these cases, a temperature above a certain level is required. Therefore, in the SOFC system, a reformer is installed in the vicinity of the SOFC (a position where heat radiation from the SOFC is received), and the SOFC system is modified by radiant heat from the SOFC. An indirect internal reforming type that heats the mass device has been developed (see, for example, Patent Document 1).

  In an indirect internal reforming SOFC system, combustible anode off-gas (gas discharged from the SOFC anode) is combusted in a casing (module container), and the reformer is heated using this combustion heat as a heat source. (For example, see Patent Document 2). In some cases, the ignition reliability is improved by providing an ignition heater in the combustion region between the SOFC and the reformer and energizing it constantly (see, for example, Patent Document 3).

JP 2002-358997 A JP 2004-319420 A Japanese Patent Laid-Open No. 2008-243592

  FIG. 1 is a graph showing the temperature dependence of the reformed gas equilibrium composition. As shown in FIG. 1, the hydrogen concentration in the reformed gas greatly depends on the reforming temperature. When the reforming temperature is low, the hydrogen concentration is low, and the hydrogen concentration increases greatly as the reforming temperature increases.

  In this respect, when the indirect internal reforming SOFC system is started, the reformer temperature is low and the reforming reaction is insufficient, and the hydrogen concentration of the reformed gas equilibrium composition is low as described above. It may be difficult to supply enough anode off-gas to the combustion zone to continue combustion, and misfires may often occur in the combustion zone. If there is a misfire, there is no heat source to heat the module, so the SOFC cannot be heated up to the predetermined temperature at which power generation starts, and the carbon monoxide in the misfired anode off-gas is not burned in the combustion region but remains as carbon monoxide outside the device. There is a risk of being discharged. Therefore, the indirect internal reforming SOFC system is required to continue the combustion in the combustion region at the time of start-up, and to improve the start-up reliability and safety.

  Then, this invention makes it a subject to provide the indirect internal reforming type solid oxide fuel cell system which can improve starting reliability and safety | security, and its operating method.

  In order to solve the above problems, an indirect internal reforming solid oxide fuel cell system according to the present invention includes a reformer having a reforming catalyst layer that generates a reformed gas using a hydrocarbon-based fuel, and a reformer. A solid oxide fuel cell that generates electricity using the reformed gas obtained from the reformer, a combustion region for burning anode off-gas discharged from the solid oxide fuel cell, the reformer, the solid oxide fuel cell, and An indirect internal reforming solid oxide fuel cell system comprising a housing for housing a combustion region, and having a reformer disposed at a position capable of receiving combustion heat generated in the combustion region. Electric heater for heating the latter stage of the catalyst catalyst layer, temperature detecting means for detecting the temperature of the latter stage of the reforming catalyst layer, and heater control means for controlling the operation of the electric heater based on the temperature detected by the temperature detecting means And.

  In the present invention, since the operation of the electric heater is controlled based on the temperature at the subsequent stage of the reforming catalyst layer at the time of start-up, for example, when the temperature at the latter stage of the reforming catalyst layer is low, the electric heater is controlled to improve the operation. The temperature of the latter stage of the catalyst catalyst layer can be raised. Thereby, at the time of start-up, activation of the autothermal reforming reaction and steam reforming reaction and increase of the hydrogen concentration of the reformed gas equilibrium composition can be achieved, and misfire can be prevented and combustion can be continued reliably. In particular, when the temperature at the rear stage of the reforming catalyst layer is increased, the hydrogen concentration of the equilibrium composition can be further increased, and the frequent occurrence of misfires can be suppressed. Therefore, according to the present invention, start-up reliability and safety can be improved.

  Here, the heater control means may be configured to be able to variably control the energization amount to the electric heater.

  The indirect internal reforming solid oxide fuel cell system operating method according to the present invention includes a heater control unit that energizes an electric heater based on a temperature detected by a temperature detection unit, thereby providing a reforming catalyst. It includes the step of controlling the temperature of the layer.

  Even in the present invention, at the time of start-up, misfire can be prevented, combustion can be continued reliably, and frequent occurrence of misfire can be suppressed, so that start-up reliability and safety can be improved.

  According to the present invention, it is possible to improve start-up reliability and safety.

It is a graph which shows the temperature dependence of the reformed gas equilibrium composition in a reforming catalyst layer. 1 is a schematic diagram showing an outline of an indirect internal reforming solid oxide fuel cell system according to an embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

[Indirect internal reforming SOFC system]
FIG. 2 is a schematic diagram showing an overview of an indirect internal reforming solid oxide fuel cell system according to an embodiment of the present invention. As shown in FIG. 2, the indirect internal reforming solid oxide fuel cell system (hereinafter referred to as “indirect internal reforming SOFC system”) 10 of the present embodiment includes a reformer 1, SOFC 3, combustion region 4. And a housing 7.

  The reformer 1 generates reformed gas from hydrocarbon fuel and has a reforming catalyst layer 11 therein. The reformer 1 is arranged at a position where heat can be received from the SOFC 3. The reformer 1 here is arranged at a position where it can receive the combustion heat generated in the combustion region 4. The reformer 1 is supplied with a hydrocarbon-based fuel, and an oxygen-containing gas such as air and water vapor are also supplied to the reformer 1 as necessary. The reformed gas obtained from the reformer 1 is supplied to the anode of the SOFC 3.

  The SOFC 3 generates power using the reformed gas obtained from the reformer 1. The combustion region 4 is a region where the anode off gas discharged from the anode of the SOFC 3 is combusted. In other words, the anode off-gas discharged from the anode is combustible in the combustion region 4. The casing 7 is a module container that houses the reformer 1, the SOFC 3, and the combustion region 4.

  The indirect internal reforming SOFC system 10 further includes a reforming catalyst layer post-stage heater 2, a temperature detection unit 5, and a heater control unit 6. The reforming catalyst layer post-stage heater 2 heats the rear half of the reforming catalyst layer 11 filled in the reformer 1, that is, the reforming catalyst layer post-stage 11x constituting the vicinity of the outlet of the reformer 1.

  The temperature detecting means 5 detects the temperature of the reforming catalyst layer rear stage 11x, and is provided in the reformer 1 near the outlet of the reformed gas. As the temperature detection means 5, a known temperature sensor such as a thermocouple can be appropriately used as long as it can detect the temperature of the reforming catalyst layer rear stage 11 x.

  The heater control means 6 controls the operation of the reforming catalyst layer latter stage heater 2 by energizing the reforming catalyst layer latter stage heater 2 based on the temperature detected by the temperature detection means 5. As a result, the temperature of the reforming catalyst layer rear stage 11x is raised, the autothermal reforming reaction, the steam reforming reaction are activated, the hydrogen concentration of the reformed gas equilibrium composition is increased, and the reliability of continued combustion is improved. It is possible.

  In the reforming catalyst layer post-stage heater 2, the temperature of the post-reforming catalyst layer post-stage 11x is preferably 450 ° C. or higher, particularly 500 ° C. or higher. When the temperature of the rear stage 11x of the reforming catalyst layer is lower than 450 ° C., the hydrogen concentration in the equilibrium composition is low, and therefore misfires may frequently occur in the combustion region 4 above the SOFC 3.

  As the reforming catalyst layer post-stage heater 2 here, a rod-shaped heater (for example, a sheath heater) is used. The reforming catalyst layer latter stage heater 2 is installed so that its axial direction is parallel to the flow path of the reformed gas inside the reformer 1. Thus, by installing the reforming catalyst layer rear heater 2 inside the reformer 1, almost all of the heat generated by the reforming catalyst layer rear heater 2 can be given to the reforming catalyst layer 11, resulting in heat loss. Can be reduced. At the same time, since the reforming catalyst layer rear heater 2 is not directly exposed to the flame of the combustion region 4, the excessive temperature rise can be prevented, and the cost and life of the reforming catalyst layer rear heater 2 can be reduced. It becomes.

  Further, the heat generating portion of the reforming catalyst layer latter stage heater 2 is located slightly in front of the reforming gas outlet side end (reforming gas inlet side) in the reformer 1. Thereby, heat transport by the flow of the reformed gas can be suitably used, and the temperature of the reforming catalyst layer rear stage 11x can be increased more efficiently.

  The heater control means 6 performs on / off control of energization to the reforming catalyst layer latter stage heater 2 and enables variable control of the energization amount. In the variable control, specifically, the temperature of the reforming catalyst layer rear stage 11x detected by the temperature detection means 5 is sent as a signal to the heater control means 6, and the heater control means 6 uses this signal. The energization amount of the rear heater 2 of the reforming catalyst layer is controlled. By such variable control, it is possible to respond arbitrarily to changes in the load of the reformer 1 and disturbances, and it is possible to reduce the power consumption of the reforming catalyst layer latter stage heater 2.

  As the heater control means 6, known control means used for control in the SOFC 3 or the indirect internal reforming SOFC system 10 can be appropriately used. Here, a control computer, a sequencer, an inverter, or the like is used as the heater control means 6.

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

  Of these, kerosene and LPG are preferred because they are readily available. Moreover, since kerosene and LPG can be stored independently, they are useful in areas where city gas lines are not widespread. Furthermore, SOFC3 using kerosene or LPG is useful as an emergency power source. In particular, kerosene is more preferable in terms of easy handling.

  The hydrocarbon fuel used as the reforming raw material can be supplied to the reformer 1 after being desulfurized as necessary. Further, when the hydrocarbon fuel is liquid, it can be supplied to the reformer 1 after being appropriately vaporized.

[Reformer]
The reformer 1 generates (produces) a reformed gas containing hydrogen from a hydrocarbon fuel. In the reformer 1, 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 1 includes 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. It can be used as appropriate. As the structure of the reformer 1, 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 1 can be appropriately selected and adopted from materials known as reformers in consideration of resistance in the use environment. The shape of the reformer 1 can be an appropriate shape such as a rectangular parallelepiped shape or a circular tube shape. In the reformer 1 (reformed catalyst layer 11), hydrocarbon-based fuel (which is vaporized in advance if necessary) and water vapor, and further, if necessary, oxygen-containing gas such as air are individually or appropriately mixed. Can be supplied.

  The reformed gas obtained from the reformer 1 is supplied to the anode of the SOFC 3. On the other hand, an oxygen-containing gas such as air is supplied to the cathode of the SOFC 3. At the time of power generation, the SOFC 3 generates heat with power generation, and the heat is transmitted from the SOFC 3 to the reformer 1 by radiant heat transfer or the like. Thus, the exhaust heat in the SOFC 3 is used for heating the reformer 1. For gas exchange and the like, piping or the like is used as appropriate.

[SOFC]
As the SOFC 3, a known SOFC can be appropriately employed. In SOFC3, oxygen ion conductive ceramics or proton conductive ceramics are generally used as an electrolyte.

  The SOFC3 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 called a bundle, but the stack here also includes a bundle) is preferable. Used. In this case, one or more stacks may be used. The shape of the SOFC 3 is not limited to a cubic stack, and an appropriate shape can be adopted.

[Case]
As the casing 7, an appropriate container that can accommodate the SOFC 3, the reformer 1, and the combustion region 4 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 casing 7 is appropriately provided with a connection port for gas exchange and the like.

  The casing 7 is preferably airtight so that the interior and the outside (atmosphere) do not communicate with each other.

[Combustion area]
The combustion region 4 is a region where the anode off gas discharged from the anode of the SOFC 3 is combusted as a combustion gas. For example, the anode outlet can be opened to the reformer 1 side in the casing 7 and the space near the anode outlet between the reformer 1 and the SOFC 3 can be used as the combustion region 4. In order to burn the anode off gas, ignition means such as an igniter can be used as appropriate.

[Arrangement of reformer]
In the indirect internal reforming SOFC system 10, the reformer 1 is disposed at a position where heat can be received from the SOFC 3. Here, the housing 7 is provided on the top of the SOFC 3 so as to face the SOFC 3. In particular, the reformer 1 is preferably placed at a position where it receives the most heat radiation of the SOFC 3 from the viewpoint of reducing thermal energy loss. Moreover, it is preferable not to arrange a shield between the combustion region 4 and the reformer 1. That is, it is preferable that the combustion region 4 and the reformer 1 face each other without sandwiching a shielding object. However, necessary piping and the like are appropriately arranged. Furthermore, it is preferable to arrange the reformer 1 and the combustion region 4 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 as the reforming catalyst 11 of the reformer 1 can be a known non-noble metal or noble metal reforming catalyst.

[Other devices]
The components of the indirect internal reforming SOFC system 10 can be appropriately provided as necessary. Specifically, a vaporizer for vaporizing a liquid, a pump for pressurizing various fluids, a pressurizing means such as a compressor, a blower, etc., for adjusting the flow rate of the fluid (or for blocking / switching the fluid flow) ) Flow rate control means such as valves, flow path shutoff / switching means, heat exchangers for heat exchange and heat recovery, condensers for condensing gas, heating / heat retention means for externally heating various devices with steam, etc., carbonization Hydrogen fuel and combustion fuel storage means, instrumentation air and electrical systems, control signal systems, control devices, output and power electrical systems, desulfurizers that reduce the concentration of sulfur in the fuel, etc. Can be mentioned.

  In the indirect internal reforming SOFC system 10 of the present embodiment configured as described above, for example, at the time of start-up, hydrocarbon-based fuel, air, and steam are supplied to the reformer 1, and reforming is performed by the reformer 1. Gas is generated and supplied to the SOFC 3. Then, the anode off gas and air are supplied from the SOFC 3 to the combustion region 4 and burned in the combustion region 4, and the reformer 1 is heated using this combustion heat as a heat source. Thereafter, the exhaust gas in the combustion region 4 is exhausted to the outside.

  At this time, the temperature of the reforming catalyst layer rear stage 11x is detected by the temperature detecting means 5, and the temperature of the reforming catalyst layer rear stage 11x is monitored. Then, based on the temperature of the reforming catalyst layer rear stage 11x, the reforming catalyst layer rear stage heater 2 is on / off controlled by the heater control means 6, or the energization amount thereof is variably controlled (current value variable control). As a result, when the temperature of the rear stage 11x of the reforming catalyst layer is low at the time of startup, the temperature of the rear stage 11x of the reforming catalyst layer is increased by the reforming catalyst layer rear stage heater 2 and this temperature is maintained at 450 ° C. (450 ° C. or higher) Will be. In other words, the reforming catalyst layer post-stage heater 2 is energized based on the temperature detected by the temperature detecting means 5, and the temperature of the reforming catalyst layer 11 is managed.

  Therefore, in this embodiment, at the time of start-up, activation of the autothermal reforming reaction, steam reforming reaction, and increase of the hydrogen concentration of the reformed gas equilibrium composition are aimed at preventing misfire and continuing combustion reliably. Can do. In particular, when the temperature of the reforming catalyst layer rear stage 11x is increased, the hydrogen concentration of the equilibrium composition can be further increased, and the frequent occurrence of misfires can be suppressed. As a result, it is possible to reliably raise the temperature of the SOFC 3 to a predetermined temperature at which power generation is started, and it is possible to prevent carbon monoxide in the anode off gas from being discharged to the outside as carbon monoxide. Therefore, according to the present embodiment, it is possible to improve start-up reliability and safety.

  If the temperature of the reforming catalyst layer rear stage 11x is 450 ° C. or higher, it is considered that hydrogen for continuation of combustion can be sufficiently supplied. In this embodiment, the temperature of the reforming catalyst layer rear stage 11x is, for example, 450 Although the reforming catalyst layer post-stage heater 2 is controlled so as to be at ° C., it is not limited to this. The temperature of the reforming catalyst layer rear stage 11x as a control target may be set to various temperatures according to at least one of the structure of the reformer 1, the catalyst performance, the raw fuel type, the air-fuel ratio, and the like.

  The preferred embodiments of the present invention have been described above. However, the indirect internal reforming solid oxide fuel cell system and the operation method thereof according to the present invention are not limited to the above embodiments, and are described in each claim. It may be modified without changing the gist, or applied to other things.

  DESCRIPTION OF SYMBOLS 1 ... Reformer, 2 ... Reformation catalyst layer latter stage heater (electric heater), 3 ... SOFC (solid oxide fuel cell), 4 ... Combustion area, 5 ... Temperature detection means, 6 ... Heater control means, 7 ... Housing, 10... Indirect internal reforming SOFC system (indirect internal reforming solid oxide fuel cell system), 11... Reforming catalyst layer, 11x.

Claims (3)

A reformer having a reforming catalyst layer for generating reformed gas using a hydrocarbon-based fuel;
A solid oxide fuel cell that generates power using the reformed gas obtained in the reformer;
A combustion region for burning anode off-gas discharged from the solid oxide fuel cell;
The reformer, the solid oxide fuel cell, and a housing that accommodates the combustion region, and the reformer is disposed at a position capable of receiving combustion heat generated in the combustion region. An indirect internal reforming solid oxide fuel cell system,
An electric heater for heating the latter stage of the reforming catalyst layer;
Temperature detecting means for detecting the temperature of the latter stage of the reforming catalyst layer;
An indirect internal reforming solid oxide fuel cell system, comprising: heater control means for controlling the operation of the electric heater based on the temperature detected by the temperature detection means.   The indirect internal reforming solid oxide fuel cell system according to claim 1, wherein the heater control means is configured to be able to variably control an energization amount to the electric heater. An operation method for starting up the solid oxide fuel cell system according to claim 1 or 2,
Indirect internal reforming comprising the step of managing the temperature of the reforming catalyst layer by energizing the electric heater based on the temperature detected by the temperature detecting means using the heater control means Type solid oxide fuel cell system operation method.

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