JP2008287959A - Indirect internal reform type high-temperature type fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an indirect internal reform type high-temperature type fuel cell capable of evaporating water by effectively utilizing heat of a high-temperature type fuel cell while preventing the temperature of a reformer from being dropped by the water evaporation. <P>SOLUTION: This indirect internal reform type high-temperature type fuel cell includes: a water evaporator evaporating water; the reformer producing a hydrogen-containing gas from a hydrocarbon-based fuel by utilizing a steam reform reaction; the high-temperature type fuel cell generating power by using the hydrogen-containing gas; and a housing which houses the water evaporator, the reformer and the high-temperature fuel cell; and is structured such that the high-temperature type fuel cell has a flame formation part capable of forming flames by burning an anode off-gas of the high-temperature type fuel cell, the reformer is arranged at a position facing the flame reformer, and the water evaporator is arranged at a position facing a part of the high-temperature type fuel cell other than the flame formation part. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  A solid oxide fuel cell (Solid Oxide Fuel Cell, hereinafter referred to as SOFC in some cases) usually contains a hydrogen-containing gas generated by reforming a hydrocarbon fuel such as kerosene or city gas in a reformer ( Reformed gas) is supplied. In the SOFC, the reformed gas and air are reacted electrochemically to generate electricity. 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 reforming, but steam reforming is often performed mainly because of the high hydrogen concentration in the resulting reformed gas. Steam reforming is a reaction that involves a very large endotherm, and the reaction temperature is relatively high at about 550 ° C. to 750 ° C., which requires a high temperature heat source. For this reason, 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. In particular, in an indirect internal reforming SOFC, combustible anode off-gas (gas discharged from the SOFC anode) is combusted in an indirect internal reforming SOFC container (module container), and this combustion heat is used as a heat source. As described above, the reformer is heated (Patent Document 1).

  For this reason, an internal reforming module is known in which a reformer is installed in the vicinity of the SOFC and the reformer is heated mainly using radiant heat from the SOFC as a heat source.

  In order to perform the steam reforming reaction, it is necessary to supply steam to the reformer. For this purpose, a water vaporizer that vaporizes water (liquid) to generate steam is used.

Patent Document 2 discloses a reformer structure in which a water vaporization unit is joined to a side of the reforming unit far from the fuel cell. Water is vaporized using the conduction heat from the reforming section heated by the radiant heat from the fuel cell.
JP 2004-319420 A JP 2006-19084 A

  However, the latent heat of vaporization of water is large, and a large endotherm is generated in the water vaporization section. Therefore, as in Patent Document 2, when water is vaporized using the conduction heat from the reforming unit, the temperature of the reforming unit is lowered, and the reforming reaction may not proceed well. Increasing the amount of the reforming catalyst to prevent this leads to an increase in the size and cost of the reformer.

  An object of the present invention is to provide an indirect internal reforming high-temperature type capable of vaporizing water by effectively utilizing the heat of a high-temperature fuel cell while preventing the temperature of the reformer from decreasing due to water vaporization. It is to provide a fuel cell.

  The present invention provides the following indirect internal reforming high temperature fuel cell.

1) a water vaporizer that vaporizes water;
A reformer that produces a hydrogen-containing gas from a hydrocarbon-based fuel using a steam reforming reaction;
A high-temperature fuel cell that generates electricity using the hydrogen-containing gas;
A housing for housing the water vaporizer, the reformer, and the high-temperature fuel cell;
The high-temperature fuel cell has a flame forming section capable of forming a flame by burning the anode off-gas of the high-temperature fuel cell,
The reformer is disposed at a position facing the flame forming section;
An indirect internal reforming high temperature fuel cell in which the water vaporizer is disposed at a position facing a portion other than the flame forming portion of the high temperature fuel cell.

  2) The indirect internal reforming high temperature fuel cell according to 1), wherein a heat insulating material is disposed between the water vaporizer and the high temperature fuel cell.

  3) The indirect internal reforming high temperature fuel cell according to 1) or 2), wherein the water vaporizer has a folded flow path in which a flow path of water is folded.

  4) The indirect internal reforming high temperature fuel cell according to 1) or 2), wherein the water vaporizer has a spiral water flow path.

  5) The indirect internal reforming high temperature fuel cell according to any one of 1) to 4), wherein at least a part of the water vaporizer is filled with particles.

  INDUSTRIAL APPLICABILITY According to the present invention, an indirect internal reforming high-temperature fuel cell that can vaporize water by effectively using the heat of the high-temperature fuel cell while preventing the temperature of the reformer from being lowered due to water vaporization. Is provided.

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

  FIG. 1 is a side sectional view schematically showing one embodiment of an indirect internal reforming high temperature fuel cell of the present invention. Here, SOFC is adopted as the high-temperature fuel cell.

  This indirect internal reforming SOFC includes a water vaporizer 1 for vaporizing water, a reformer 2 for producing a hydrogen-containing gas (reformed gas) from a hydrocarbon fuel using a steam reforming reaction, It has SOFC3 that generates electricity using the hydrogen-containing gas obtained by the quality device. The indirect internal reforming SOFC has a housing (hereinafter, referred to as a module container in some cases) 4 that houses the water vaporizer 1, the reformer 2, and the SOFC 3.

  Here, the water vaporizer, the reformer, the SOFC, and the module container have a rectangular parallelepiped shape. Kerosene is used as the hydrocarbon fuel.

  The SOFC has a flame forming portion 3a capable of forming a flame 5 by burning anode off gas (gas discharged from the anode). Here, the flame forming portion is one side surface having the anode outlet of the SOFC.

  The reformer 2 is disposed at a position facing the flame forming portion 3a. That is, the reformer is disposed at a position facing the one side surface.

  The water vaporizer 1 is disposed at a position facing a portion of the SOFC 3 other than the flame forming portion 3a. Here, the water vaporizer is arranged at a position facing the bottom surface of the SOFC (which may be a side surface other than the one side surface or the top surface).

  Water is vaporized by the water vaporizer 1 to become water vapor, and the water vapor is supplied to the reformer 2 via the preheater 6. On the other hand, kerosene is supplied from the preheating tube 7 to the reformer 2. The preheater also has a rectangular parallelepiped shape, and the water vaporizer 1 and the reformer 2 are connected in an L shape via the preheater 6 and integrated. A preheating tube 7 passes through the preheater 6. An opening 9 is provided in the wall separating the water vaporizer and the preheater, and steam is supplied to the preheater from this opening. An opening 10 is also provided in the wall separating the preheater and the reformer, steam is supplied to the reformer from this opening, and the preheating pipe 7 passes through the opening in the reformer 2 (reforming catalyst layer). 2a does not exist). When kerosene passes through the preheating tube 7, it is preheated by the sensible heat of water vapor. The preheating tube may be supplied with kerosene in liquid form, may be vaporized in advance and supplied with vaporized kerosene, or may be supplied in a gas-liquid mixed phase. When part or all of the kerosene is liquid, the kerosene droplets are ejected from the outlet of the preheating tube, and the droplets can be vaporized while mixing with the water vapor flow.

  A mixed gas of steam and vaporized kerosene is supplied to the reforming catalyst layer 2a, where it is reformed by a steam reforming reaction, and the reformed gas is supplied from the reformer 2 to the anode of the SOFC 3. The steam reforming reaction may be accompanied by a partial oxidation reaction. In this case, an oxygen-containing gas such as air necessary for the partial oxidation reaction is appropriately supplied to the reformer (not shown). Although not shown, air is supplied to the cathode, and power generation is performed by the SOFC. In the flame forming unit 5, combustible components in the anode off gas are burned by oxygen in the cathode off gas, and a flame 5 is formed. The combustion gas is discharged from a discharge port (not shown) provided in the module container 4.

  By disposing the reformer at a position facing the flame forming portion, the reformer is efficiently heated not only by the radiant heat from the SOFC but also by the radiant heat from the flame 5.

  On the other hand, the water vaporizer may be at a lower temperature than the reformer. For this reason, a water vaporizer can be heated by the radiant heat from SOFC by arrange | positioning a water vaporizer in the position facing parts other than the flame formation part of SOFC.

  When water is heated suddenly by the radiant heat of SOFC, evaporation vibration occurs, and as a result, the electrical output of SOFC may fluctuate. In order to suppress this, it is preferable to arrange the heat insulating material 8 between the water vaporizer 1 and the SOFC 3. That is, the water vaporizer can face the SOFC with the heat insulating material interposed therebetween. As the heat insulating material, a known heat insulating material that can withstand the use environment can be appropriately used.

  In order to reduce evaporation vibration, the water vaporizer preferably has a folded flow path in which the water flow path is folded or a spiral water flow path. Here, the flat plate 1a is arranged inside the water vaporizer, and thereby the flow path is folded back from a portion having a low temperature far from the SOFC to a portion having a high temperature close to the SOFC. Thus, the water vaporizer 1 has a folded channel having a rectangular cross section.

  Water can be heated gently by the heat insulating material and the folded channel. In order to reduce evaporation vibration, it is also preferable that at least a part of the water vaporizer is filled with particles.

  FIG. 2 shows another example of the indirect internal reforming SOFC. Unlike the example shown in FIG. 1, this example does not have the preheater 7. Further, the water vaporizer 1 and the reformer 2 are not integrated and are provided apart from each other. Kerosene is supplied after being vaporized in advance.

  Although the water vaporizer, the reformer, the SOFC, and the preheater have a rectangular parallelepiped shape in the examples shown in FIGS. 1 and 2, this is not restrictive.

  FIG. 3 shows another example of the indirect internal reforming SOFC. In the example shown in FIGS. 1 and 2, the reformer is opposed to the entire flame forming unit. However, in this example, the reformer 2 is opposed to a part of the flame forming unit 3a. ing. The heat insulating material 8 is also provided on the surface of the water vaporizer 1 that does not face the SOFC.

  FIG. 4 shows another example of the indirect internal reforming SOFC. In this example, a part of the reformer 2 faces the flame forming part 3a. Further, another part of the reformer faces a part other than the SOFC flame forming part.

  FIG. 5 shows another example of the indirect internal reforming SOFC. In this example, two SOFCs 3 are provided. And the reformer 2 is distribute | arranged to the position facing a part of flame formation part 3a of each SOFC. Further, the water vaporizer 1 has a part thereof facing a portion other than the two SOFC 3 flame forming portions 3a, and has a spiral channel whose cross section (cross section perpendicular to the flow of water) is circular. is doing. As a result, water is supplied from a portion having a low temperature far from the SOFC toward a portion having a high temperature close to the SOFC. The heat insulating material 8 is also provided on the surface of the water vaporizer 1 that does not face the SOFC.

  FIG. 6 shows another example of the indirect internal reforming SOFC. Similar to the example shown in FIG. 5, two SOFCs 3 are provided in this example. However, in the example shown in FIG. 5, there are flame forming portions inside and outside each SOFC. However, in this example, there are flame forming portions only inside each SOFC. The reformer 2 is arranged at a position facing the flame forming portions 3a of the two SOFCs 3. Further, the water vaporizer 1 is arranged around the two SOFCs 3 (positions facing portions other than the flame forming portion 3a). The water vaporizer 1 has a double spiral channel. Water flows through the outer spiral channel upward, and then flows downward through the inner channel and is supplied to the reformer 2. As a result, water is supplied from a portion having a low temperature far from the SOFC toward a portion having a high temperature close to the SOFC.

[Water vaporizer]
As the water vaporizer, a known structure and material capable of vaporizing water can be appropriately employed. As described above, it is preferable that the water vaporizer has a folded flow path in which the flow path of water is folded, or a spiral flow path. The structure of the water vaporizer having the folded flow path is not limited to the above-described example, and a structure in which the tube is folded may be employed. The structure of the water vaporizer having a spiral channel is not limited to the above-described example, and a structure in which the spiral channel is formed by a flat plate can also be adopted. Further, in any case of the folded flow path and the spiral flow path, the structure is not limited to the above example, and a structure having a plurality of flow paths in parallel can also be adopted.

  Moreover, it is preferable that at least a part of the water vaporizer is filled with particles. The particles for this purpose can be appropriately selected from materials that can withstand temperature and atmosphere, and examples thereof include ceramics such as alumina and silica, and metals such as stainless steel. As the shape of the grains, an appropriate shape such as a sphere, a cylinder, a wedge, a rectangular parallelepiped or the like can be adopted.

[Hydrocarbon fuel]
The hydrocarbon-based fuel is appropriately selected from compounds or mixtures thereof containing carbon and hydrogen (may contain other elements such as oxygen) known in the field of high-temperature fuel cells as a reformed gas raw material. 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 areas where city gas lines are not widespread. Furthermore, a high-temperature fuel cell using kerosene or LPG is useful as an emergency power source. In particular, kerosene is preferable because it is easy to handle.

[High-temperature fuel cell]
The present invention can be suitably applied to an indirect internal reforming high-temperature fuel cell that can heat the reformer by heat radiation from the fuel cell. Examples of the high temperature fuel cell include a molten carbonate fuel cell (MCFC) in addition to SOFC.

  As the SOFC, various known shapes such as a flat plate type and a cylindrical type can be appropriately selected and used. The shape of the SOFC is an appropriate shape such as a rectangular parallelepiped (including cube) stack of flat SOFCs, a cylindrical SOFC stack, a bundle of tubular SOFC cells, or a cylindrical cylindrical SOFC. it can. In the SOFC, oxygen ion conductive ceramics or proton ion conductive ceramics are generally used as an electrolyte.

  The MCFC can be appropriately selected from known MCFCs.

  The SOFC or MCFC may be a single cell, but in practice, a stack or bundle in which a plurality of single cells are arranged is preferably used. In this case, the stack or bundle may be one or plural.

[Reformer]
In the reformer, a reforming catalyst having steam reforming ability can be used. As the reforming catalyst having steam reforming ability, a steam reforming catalyst having steam reforming ability and an autothermal reforming catalyst having both partial oxidation reforming ability and steam reforming ability may be used as appropriate. it can.

  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 high temperature fuel cell.

  Among the indirect internal reforming high temperature fuel cells, the indirect internal reforming SOFC is excellent in that it can increase the thermal efficiency. The indirect internal reforming SOFC includes a reformer that produces a reformed gas containing hydrogen from a hydrocarbon-based fuel using a steam reforming reaction, and the SOFC. In this reformer, a steam reforming reaction can be performed, and autothermal reforming accompanied by a partial oxidation reaction in the steam reforming reaction may be performed. From the viewpoint of power generation efficiency of SOFC, it is preferable that the partial oxidation reaction does not occur. In autothermal reforming, steam reforming is dominant, and therefore the reforming reaction becomes endothermic in overall. Then, heat necessary for the reforming reaction is supplied from the SOFC. The reformer and SOFC are accommodated in one module container and modularized. The reformer is disposed at a position that receives heat radiation from the SOFC. By doing so, the reformer is heated by heat radiation from the SOFC during power generation. In addition, the SOFC can be heated by burning the anode off-gas discharged from the SOFC at the cell outlet.

  In the indirect internal reforming SOFC, the reformer is preferably arranged at a position where direct heat transfer from the SOFC to the outer surface of the reformer is possible. Therefore, it is preferable that a shielding object is not substantially disposed between the reformer and the SOFC, that is, a gap is provided between the reformer and the SOFC. Further, it is preferable to shorten the distance between the reformer and the SOFC as much as possible.

  Each supply gas is appropriately preheated as necessary and then supplied to the reformer or SOFC.

  As the module container, an appropriate container capable of accommodating the SOFC and the reformer 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.

  In particular, when the cell outlet is open in the module container, the module container is preferably airtight so that the inside of the module container and the outside (atmosphere) do not communicate with each other.

[Reforming catalyst]
Any of the steam reforming catalyst and the autothermal reforming catalyst used in the reformer can be a known catalyst. Examples of the steam reforming catalyst include ruthenium-based and nickel-based catalysts, and examples of the autothermal reforming catalyst include rhodium-based catalysts.

  Hereinafter, the conditions of rated operation in the reformer will be described for each of steam reforming and autothermal reforming.

In steam reforming, steam is added to a hydrocarbon fuel such as kerosene. The steam reforming reaction temperature is, for example, 400 ° C to 1000 ° C, preferably 500 ° C to 850 ° C, more preferably 550 ° C to 800 ° C. The amount of steam introduced into the reaction system is defined as the ratio of the number of moles of water molecules to the number of moles of carbon atoms contained in the hydrocarbon fuel (steam / carbon ratio), and this value is preferably 1 to 10, more preferably 1.5-7, more preferably 2-5. When the hydrocarbon fuel is liquid, the space velocity (LHSV) at this time is A / B when the flow rate in the liquid state of the hydrocarbon fuel is A (L / h) and the catalyst layer volume is B (L). This value is preferably set in the range of 0.05 to 20 h ⁻¹ , more preferably 0.1 to 10 h ⁻¹ , and still more preferably 0.2 to 5 h ⁻¹ .

  In autothermal reforming, an oxygen-containing gas is added to the hydrocarbon fuel in addition to steam. The oxygen-containing gas may be pure oxygen, but air is preferred because of its availability. An oxygen-containing gas can be added so that the endothermic reaction accompanying the steam reforming reaction is balanced, and a heat generation amount capable of maintaining the temperature of the reforming catalyst layer and SOFC or raising the temperature thereof can be obtained. The addition amount of the oxygen-containing gas is preferably 0.005 to 1, more preferably 0.01 to 0.00 as the ratio of the number of moles of oxygen molecules to the number of moles of carbon atoms contained in the hydrocarbon fuel (oxygen / carbon ratio). 75, more preferably 0.02 to 0.6. The reaction temperature of the autothermal reforming reaction is set, for example, in the range of 400 ° C to 1000 ° C, preferably 450 ° C to 850 ° C, and more preferably 500 ° C to 800 ° C. When the hydrocarbon fuel is liquid, the space velocity (LHSV) at this time is preferably selected in the range of 0.05 to 20, more preferably 0.1 to 10, and further preferably 0.2 to 5. The amount of steam introduced into the reaction system is preferably 1 to 10, more preferably 1.5 to 7, and still more preferably 2 to 5 as a steam / carbon ratio.

[Other equipment]
The indirect internal reforming high-temperature fuel cell of the present invention can be used by appropriately adding known components of the high-temperature fuel cell system as necessary. Specific examples of such components include desulfurizers that reduce the sulfur content in hydrocarbon fuels, vaporizers that vaporize liquids, pumps for pressurizing various fluids, compressors, blowers, etc. Means, a flow rate adjusting means such as a valve for adjusting the flow rate of the fluid, or shutting off / switching the fluid flow, a flow path shutting / switching means, a heat exchanger for performing heat exchange / heat recovery, condensing the gas Condenser / steam, heating / heat-retaining means for external heating of various devices, storage means for hydrocarbon fuels and combustibles, instrumentation air and electrical system, control signal system, control device, output and power For example, the electrical system.

  The indirect internal reforming high-temperature fuel cell of the present invention can be used for, for example, a stationary or moving power generation system and a cogeneration system.

It is a typical sectional side view which shows the example of the indirect internal reforming type | mold high temperature type fuel cell of this invention. It is a typical sectional side view which shows another example of the indirect internal reforming type | mold high temperature type fuel cell of this invention. It is a typical sectional side view which shows another example of the indirect internal reforming type | mold high temperature type fuel cell of this invention. It is a typical sectional side view which shows another example of the indirect internal reforming type | mold high temperature type fuel cell of this invention. It is a typical sectional side view which shows another example of the indirect internal reforming type | mold high temperature type fuel cell of this invention. It is a typical sectional side view which shows another example of the indirect internal reforming type | mold high temperature type fuel cell of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water vaporizer 1a Flat plate 2 Reformer 2a Reforming catalyst layer 3 SOFC
3a SOFC flame formation part 4 Case (module container)
5 Flame 6 Preheater 7 Preheating tube 8 Heat insulating material 9 Opening 10 Opening

Claims (5)

A water vaporizer to vaporize the water;
A reformer that produces a hydrogen-containing gas from a hydrocarbon-based fuel using a steam reforming reaction;
A high-temperature fuel cell that generates electricity using the hydrogen-containing gas;
A housing for housing the water vaporizer, the reformer, and the high-temperature fuel cell;
The high-temperature fuel cell has a flame forming section capable of forming a flame by burning the anode off-gas of the high-temperature fuel cell,
The reformer is disposed at a position facing the flame forming section;
An indirect internal reforming high temperature fuel cell in which the water vaporizer is disposed at a position facing a portion other than the flame forming portion of the high temperature fuel cell.   The indirect internal reforming type high temperature fuel cell according to claim 1, wherein a heat insulating material is disposed between the water vaporizer and the high temperature fuel cell.   The indirect internal reforming high-temperature fuel cell according to claim 1 or 2, wherein the water vaporizer has a folded flow path in which a water flow path is folded.   The indirect internal reforming high temperature fuel cell according to claim 1 or 2, wherein the water vaporizer has a spiral water flow path.   The indirect internal reforming high-temperature fuel cell according to any one of claims 1 to 4, wherein at least a part of the water vaporizer is filled with particles.

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