JP2008084683A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell capable of supplying gas nearly homogeneously to respective power generating elements of a cell stack. <P>SOLUTION: In the fuel cell, the power generating elements in which a fuel side electrode 66 is formed on one side of a solid electrolyte 68 while an oxygen side electrode 70 is formed on the other side of it are laminated in a plurality of number. The fuel cell includes the cell stack 60 in which the plurality of power generating elements are electrically connected, a manifold 58 to supply a gas to the plurality of power generating elements via a gas passage 74, and a gas supplying tube 80 installed at one end of the manifold 58. The fuel cell supplies the gas supplied to the manifold 58 by the gas supplying tube 80, respectively, to the power generating element via the gas passage 74. A cross sectional area of the gas passage 74 at the center part of a power generating element laminating direction of the cell stack 60 is larger than that of the gas passage 74 in the gas supplying tube 80 side of the cell stack 60. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides a fuel comprising: a cell stack formed by stacking a plurality of power generation elements; a manifold that supplies gas to the plurality of power generation elements via gas passages; and a gas supply pipe provided at one end of the manifold. It relates to batteries.

  In recent years, various types of fuel cells such as solid polymer, phosphoric acid, molten carbonate, and solid electrolyte have been proposed as next-generation energy. In particular, solid oxide fuel cells have advantages such as high operating temperature, high power generation efficiency, and use of exhaust heat, and research and development are being promoted.

For example, as described in Patent Document 1 below, a fuel cell includes a cell stack in which a plurality of fuel cell cells are stacked in a storage container, a manifold provided with the cell stack, and one end of the manifold. A gas supply pipe provided in the section is known. In such a fuel cell, the gas supplied to the manifold by the gas supply pipe is supplied to the power generation unit of the fuel cell via a gas passage communicating with the manifold.
JP 2005-285340 A

  When generating electricity with the above-described fuel cell, a phenomenon occurs in which the central portion of the cell stack in the stacking direction of the fuel cell becomes higher in temperature than both sides of the cell stack. This is a phenomenon that occurs when Joule heat and reaction heat are generated in a fuel cell by causing a current to flow through the fuel cell and the heat stays at the center in the stacking direction of the fuel cell. Therefore, during fuel cell operation, a temperature distribution occurs in which the temperature of the cell stack is high at the center in the stacking direction of the fuel cells and the temperature is low at both sides of the cell stack.

  In such a fuel cell, the gas in the gas passage expands in the fuel cell at the central portion in the stacking direction, thereby increasing the pressure loss in the gas passage of the fuel cell at the central portion in the stacking direction, thereby increasing the fuel utilization rate. When the height is increased, so-called fuel depletion may occur in the fuel cell at the center in the stacking direction.

  Even if fuel depletion does not occur, the amount of gas supplied to the fuel cells in the central portion in the stacking direction is reduced, the power generation performance of the fuel cells in the central portion in the stacking direction is reduced, and the power generation amount of the fuel cell as a whole is also reduced. There was a problem.

  Such a problem is remarkable in a fuel cell of 10 KW or less, particularly a fuel cell used for home use. In other words, since fuel cells used in homes are required to be small and highly efficient, the distance between the fuel cells is short and the density of the fuel cells is high, so temperature distribution tends to occur in the cell stack, The pressure loss in the gas passage of the fuel cell in the center in the stacking direction tends to increase.

  An object of this invention is to provide the fuel cell which can supply gas almost uniformly to the electric power generation element of a cell stack.

  A fuel cell according to the present invention includes a cell stack in which a plurality of power generation elements each having a fuel side electrode formed on one side and an oxygen side electrode formed on the other side of the solid electrolyte are electrically connected. And a manifold that supplies gas to the plurality of power generation elements via gas passages, and a gas supply pipe provided at one end of the manifold, and gas supplied to the manifold by the gas supply pipe Is supplied to the power generation element via the gas passage, and the cross-sectional area of the gas passage at the central portion of the cell stack in the power generation element stacking direction is the gas passage on the gas supply pipe side of the cell stack. It is characterized by being larger than the cross-sectional area.

  When the gas passages for supplying gas to the power generation element have the same cross-sectional area, the power generation element has a power generation reaction heat or Joule heat so that the temperature of the power generation element at the center in the power generation element stacking direction As a result, the pressure loss in the gas passage at the central portion in the stacking direction of the power generation elements increases due to gas expansion, and the gas supply to the power generation elements compared to the power supply elements on the gas supply pipe side that supplies gas to the manifold However, in the present invention, the cross-sectional area of the gas passage at the central portion of the cell stack in the stacking direction is determined by the gas supply of the cell stack. Since the cross-sectional area of the gas passage on the tube side is larger, even if the temperature of the power generation element at the center of the power generation element stacking direction becomes higher, the power generation element stacking direction The pressure loss difference between the gas passage for supplying gas to the power generation element on the central part and the gas supply pipe side can be reduced, and the amount of gas supplied to the power generation element on the power generation element laminating direction and the power supply element on the gas supply pipe side can be reduced. Can be uniform.

  Further, in the fuel cell of the present invention, the cross-sectional area of the gas passage at the end portion in the gas supply direction by the gas supply pipe is smaller than the cross-sectional area of the gas passage at the central portion of the cell stack in the power generation element stacking direction. It is characterized by being larger than the cross-sectional area of the gas passage on the gas supply pipe side. In such a fuel cell, the pressure loss difference of the gas passage in the whole cell stack can be reduced, and gas can be supplied to each power generating element of the cell stack almost uniformly.

  A fuel cell according to the present invention includes a cell stack in which a plurality of power generation elements each having a fuel side electrode formed on one side and an oxygen side electrode formed on the other side of the solid electrolyte are electrically connected. And a manifold that supplies gas to the plurality of power generation elements via gas passages, and a gas supply pipe provided at one end of the manifold, and gas supplied to the manifold by the gas supply pipe Is supplied to the power generation element via a gas passage communicating with the manifold, and the length of the gas passage in the central portion of the cell stack in the power generation element stacking direction is the gas supply pipe of the cell stack. It is characterized by being shorter than the length of the gas passage on the side.

  In such a fuel cell, since the gas passage length in the central portion of the cell stack in the power generation element stacking direction is shorter than the length of the gas passage on the gas supply pipe side of the manifold, the temperature of the power generation element in the central portion in the stacking direction is high. Even in this case, it is possible to reduce the pressure loss difference between the gas passage supplying gas to the power generation element on the gas supply pipe side and the power generation element stacking direction center. The amount of gas supplied to the element can be made substantially uniform.

  Further, in the fuel cell of the present invention, the length of the gas passage at the gas supply direction end portion of the gas supply pipe is longer than the length of the gas passage at the central portion of the cell stack in the power generation element stacking direction. It is characterized by being shorter than the length of the gas passage on the gas supply pipe side. In such a fuel cell, the pressure loss difference of the gas passage in the whole cell stack can be reduced, and gas can be supplied to each power generating element of the cell stack almost uniformly.

  The fuel cell of the present invention is characterized in that the amount of power generation is 10 KW or less. The fuel cell of the present invention is used for home use. In such a fuel cell, it is necessary to arrange a large number of power generation elements without gaps in order to obtain a small amount of electricity and a large amount of power generation. In particular, the central portion of the power generation elements in the stacking direction tends to be hotter than both sides. The fuel cell of the invention can be used effectively.

  The fuel cell of the present invention reduces the difference in pressure loss between the gas passage supplying gas to the power generation element on the gas supply pipe side and the power generation element stack direction central portion even if the temperature of the power generation element in the center portion in the stacking direction becomes high. Therefore, the amount of gas supplied to the central portion in the power generation element stacking direction and the power generation element on the gas supply pipe side can be made substantially uniform.

  Hereinafter, the fuel cell of the present invention will be described with reference to FIGS. The illustrated fuel cell includes a housing 2 having a substantially rectangular parallelepiped shape. The outer surface of the six wall surfaces of the housing 2 is a heat insulating wall (heat insulating member) formed of an appropriate heat insulating material, that is, the upper heat insulating wall 4, the lower heat insulating wall 6, the right heat insulating wall 8, the left heat insulating wall 9, and the front A heat insulating wall (not shown) and a rear heat insulating wall (not shown) are disposed. A power generation / combustion chamber 12 is defined in the housing 2.

  The front heat insulation wall and / or the rear heat insulation wall are detachably or detachably mounted, and the power generation / combustion chamber 12 can be accessed by detaching or opening the front heat insulation wall and / or the rear heat insulation wall. If desired, an outer wall, which may be made of a metal plate, can be disposed on the outer surface of each heat insulating wall.

  An air chamber (oxygen-containing gas chamber) 16 is disposed at the upper end in the housing 2. The air chamber 16 is defined in a rectangular parallelepiped case 17 having a relatively small vertical dimension. The air chamber 16 communicates with the upper ends of a number of air supply pipes (oxygen-containing gas supply means) 22a for sending air (oxygen-containing gas) toward the power generation / combustion chamber. The shape of the air supply pipe 22aa may be a cylinder or a hollow plate structure. 1 and 2, a cylindrical air supply pipe 22aa is shown. The air supply pipe 22a is disposed between the cell stacks described later, and has an opening at the lower end portion of the cell, and air is ejected from the opening portion. The air supply pipe 22aa is preferably made of a material having high heat resistance such as ceramics.

  A heat exchanger 24 having a flat plate shape as a whole is disposed on both sides of the housing 2, more specifically, inside the right heat insulating wall 8 and inside the left heat insulating wall 9. Each of the heat exchangers 24 is constituted by a case 26 having a hollow flat plate shape extending substantially vertically.

  A partition plate 28 located in the middle in the lateral direction is disposed in the case 26, and the inside of the case 26 is partitioned into a discharge path 30 positioned on the inner side and an inflow path 32 positioned on the outer side. Three partition walls 34 and 36 are arranged in the discharge path 30 at intervals in the vertical direction. More specifically, in the discharge passage 30, the front edge is located rearwardly away from the front wall (not shown) of the case 26, but the rear edge is the rear wall (not shown) of the case 26. And a partition wall 36 whose front edge is connected to the front wall of the case 26 but whose rear edge is spaced forward from the rear wall of the case 26. Are alternately arranged, and thus the combustion gas discharge passage 30 is zigzag-shaped. If desired, a form other than the zigzag flow path may be used.

  Similarly, the three partition walls 38 and 40, that is, the front edges thereof are also spaced apart from the front wall (not shown) of the case 26 in the inflow path 32 with a space in the vertical direction. The rear wall is connected to the rear wall (not shown) of the case 26, and the front edge of the partition wall 38 is connected to the front wall of the case 26. The partition walls 40 spaced apart from the front are alternately arranged, and thus the inflow passage 32 is also zigzag-shaped. If desired, a form other than the zigzag flow path may be used.

  A discharge opening 42 is formed at the upper end of the inner wall of the case 26, and the discharge path 30 is communicated with the power generation / combustion chamber 12 through the discharge opening 42. In the illustrated embodiment, heat storage walls (heat shielding members) made of a heat storage material are arranged on the power generation / combustion chamber 12 side of the heat exchanger 24, that is, on the fuel cell side and above and below the fuel cell. Has been. That is, the right heat storage wall 44a, the left heat storage wall 44b, the front heat storage wall (not shown), the rear heat storage wall (not shown), the lower heat storage wall 44e, and the upper heat insulation wall 44f are arranged so as to surround the cell assembly. ing. An opening 45 is formed in the upper part of the right heat storage wall 44 a and the left heat storage wall 44 b so as to be located at substantially the same height as the lower edge of the discharge opening 42, and the discharge opening 42 generates power through the opening 45. -It is connected to the combustion chamber 12.

  An inflow opening 48 is formed on the outer side of the upper wall of the case 26, and the inflow path 32 is communicated with the air chamber (oxygen-containing gas chamber) 16 through the inflow opening 48. The heat exchanger 24 and the inflow opening 48 constitute a gas supply channel. A double cylinder 50 (only the upper end portion is shown in FIG. 1) extending in the vertical direction is disposed behind each of the inflow passages 32. The double cylinder 50 is an outer cylinder member. 52 and an inner cylindrical member 54. The lower end of the discharge path 30 is connected to the lower end of the discharge path defined between the outer cylinder member 52 and the inner cylinder member 54, and the lower end of the inflow path 32 is defined in the inner cylinder member 54. Connected to the inflow channel.

  Four power generation units 56a, 56b, 56c and 56d are arranged in the lower part of the above-described power generation / combustion chamber. The power generation units 56a, 56b, 56c and 56d are respectively positioned between the air supply pipes 22a described above. In other words, the air supply pipe 22a is disposed between the power generation units 56a, 56b, 56c and 56d.

  That is, a plurality of fuel cells 62 are arranged in a line to form cell stacks 60a, 60b, 60c and 60d, and the plurality of cell stacks 60a, 60b, 60c and 60d are arranged in a matrix. So that the air is supplied through the air supply pipe 22a between the cell stacks 60a, 60b, 60c, and 60d. It is configured.

  The fuel cell 62 is provided with a fuel gas passage 74 penetrating in the length direction, and the fuel cell 62 is provided upright on the upper surface of the fuel manifold 58a, as will be described later. .

  The connection structure of the air supply pipe 22a will be described in detail. As shown in FIG. 2B, one end of the air supply pipe 22a is fixed to the plate-like body 17a in a state where the air supply pipes 22a are arranged in a row. A plurality of pipe assemblies 18 are produced, and slits 17c are formed in the cell stack side wall 17b of the case 17 constituting the air chamber 16 in portions located in the space between the cell stacks. The air supply pipes 22a of the body 18 are respectively inserted, and the plate-like body 17a of the pipe assembly 18 is in contact with and fixed to the upper surface of the cell stack wall 17b.

  The air supply pipe 22a has a ring-shaped cross section, is cylindrical, supplies air from the top to the bottom inside the air supply pipe 22a, and supplies fuel gas from the bottom to the top inside the fuel cell 62. Is done.

  3 and 4 together with FIGS. 1 and 2, the power generation unit 56a includes a rectangular parallelepiped fuel manifold 58a extending in the front-rear direction (direction perpendicular to the paper surface in FIG. 1).

  A cell stack 60a is provided on the upper surface of the fuel manifold 58a that defines the fuel gas chamber. The cell stack 60a is configured by arranging a plurality of upright cells 62 that are elongated in the vertical direction in the longitudinal direction (that is, the front-rear direction) of the fuel manifold 58a. As clearly shown in FIG. 5, each of the hollow flat cells 62 includes an electrode support substrate 64, a fuel electrode layer 66 as an inner electrode layer, a solid electrolyte layer 68, an oxygen electrode layer 70 as an outer electrode layer, and an interface. The connector 72 is configured.

  The electrode support substrate 64 is a columnar plate-like piece that is elongated in the vertical direction, and the cross-sectional shape thereof has both flat surfaces and both sides of a semicircular shape. The electrode support substrate 64 is formed with a plurality (six in the illustrated example) of fuel gas passages 74 penetrating the electrode support substrate 64 in the vertical direction. Each of the fuel cells 62 is joined to the upper wall of the fuel manifold 58a by, for example, a ceramic adhesive having excellent heat resistance.

  On the upper wall of the fuel manifold 58a, a plurality of slits (not shown) extending in the left-right direction are formed at intervals in a direction perpendicular to the paper surface in FIG. A fuel gas passage 74 is communicated with the fuel gas chamber according to each of the slits.

  The interconnector 72 is disposed on one side of the electrode support substrate 64 (upper surface in the cell stack 60a in FIG. 5). The fuel electrode layer 66 is disposed on the other surface (the lower surface in the cell stack 60a of FIG. 5) and both side surfaces of the electrode support substrate 64, and both ends thereof are joined to both ends of the interconnector 72. The solid electrolyte layer 68 is disposed so as to cover the entire fuel electrode layer 66, and both ends thereof are joined to both ends of the interconnector 72. The oxygen electrode layer 70 is disposed on the main part of the solid electrolyte layer 68, that is, on the portion covering the other surface of the electrode support substrate 64, and is positioned to face the interconnector 72 with the electrode support substrate 64 interposed therebetween. .

  A fuel electrode layer 66 is formed on one side of the solid electrolyte layer 68, and an oxygen electrode layer 70 is formed on the other side, whereby one side of the electrode support substrate 64 (the lower surface in the cell stack 60a in FIG. 5). ) On which the fuel electrode layer 66 and the oxygen electrode layer 70 are superimposed on the solid electrolyte layer 68 is disposed. In other words, a plurality of power generating elements are stacked via the electrode support substrate 64, the interconnector 72, and the current collecting member 76, and the adjacent power generating elements are the electrode support substrate 64, the interconnector 72, and the current collecting member 76. Are connected in series electrically to form a cell stack 60a.

  A current collecting member 76 is disposed between adjacent cells 62 in the cell stack 60a, and connects the interconnector 72 of one cell 62 and the oxygen electrode layer 70 of the other cell 62. Current collecting members 76 are disposed on both ends of the cell stack 60a, that is, on one side and the other side of the cell 62 positioned at the upper end and the lower end in FIG. Electric power extraction means (not shown) is connected to the current collecting members 76 located at both ends of the cell stack 60a. The electric power extraction means is the front heat insulating wall, the rear heat insulating wall, or the lower heat insulating material 6 of the housing 2. And extends outside the housing 2. If desired, the cell stacks 60a, 60b, 60c and 60d are connected in series with each other by appropriate connection means instead of disposing the power extraction means in each of the cell stacks 60a, 60b, 60c and 60d. Common power extraction means may be provided for the cell stacks 60a, 60b, 60c and 60d.

  More specifically about the cell 62, the electrode support substrate 64 is gas permeable to allow fuel gas to permeate to the anode layer 66, and is also conductive to collect current through the interconnector 72. Can be formed from a porous conductive ceramic (or cermet) that satisfies such requirements.

  In order to manufacture the cell 62 by co-firing with the fuel electrode layer 66 and / or the solid electrolyte layer 68, it is preferable to form the electrode support substrate 64 from the iron group metal component and the specific rare earth oxide. In order to provide the required gas permeability, it is preferred that the open porosity is in the range of 30% or more, in particular 35 to 50%, and the conductivity is also 300 S / cm or more, in particular 440 S / cm or more. Is preferred.

The fuel electrode layer 66 can be formed of a porous conductive ceramic, for example, ZrO ₂ (referred to as stabilized zirconia) in which a rare earth element is dissolved and Ni and / or NiO.

The solid electrolyte layer 68 has a function as an electrolyte for bridging electrons between electrodes, and at the same time needs to have a gas barrier property in order to prevent leakage between fuel gas and air. In general, it is formed from ZrO ₂ in which ₃ to 15 mol% of a rare earth element is dissolved.

The oxygen electrode layer 70 can be formed of a conductive ceramic made of a so-called ABO ₃ type perovskite oxide. The oxygen electrode layer 70 is required to have gas permeability, and the open porosity is preferably 20% or more, particularly preferably in the range of 30 to 50%.

Although the interconnector 72 can be formed from a conductive ceramic, it needs to have a reduction resistance and an oxidation resistance in order to come into contact with a fuel gas and air that may be hydrogen gas. A perovskite oxide (LaCrO ₃ oxide) is preferably used. The interconnector 72 must be dense in order to prevent leakage of fuel gas passing through the fuel gas passage 74 formed in the electrode support substrate 64 and air flowing outside the electrode support substrate 64, and is 93% or more. In particular, it is desired to have a relative density of 95% or more.

  The current collecting member 76 can be composed of a member having an appropriate shape formed of a metal or alloy having elasticity, or a member obtained by adding a required surface treatment to a felt made of metal fiber or alloy fiber.

  Continuing the description with reference to FIG. 4, the power generation unit 56 a also includes a reforming case 78 a that is preferably a rectangular shape (or a cylindrical shape) that extends elongated in the front-rear direction above the cell stack 60 a. ing. One end, that is, the upper end of the fuel gas supply pipe 80a is connected to the front surface of the reforming case 78a.

  The fuel gas supply pipe 80a extends downward, then curves and extends rearward, and the other end of the fuel gas supply pipe 80a is connected to the front surface (one end) of the fuel manifold 58a. One end of a reformed gas supply pipe 82a is connected to the rear surface of the reforming case 78a. The to-be-reformed gas supply pipe 82 a extends downward from the reforming case, and extends under the housing 2 and out of the housing 2.

  In the fuel cell according to the present invention, as shown in FIG. 6, the cross-sectional area of the fuel gas passage 74 of the fuel cell 62 in the central portion x of the power stacking direction of the cell stack 60a is the fuel gas supply pipe of the cell stack 60a. The cross-sectional area of the fuel gas passage 74 of the fuel cell 62 on the 80a side (the right side in FIG. 6) is made larger. The electrode support substrate 64 is formed with a plurality (six in the illustrated example) of fuel gas passages 74 penetrating through the electrode support substrate 64 in the vertical direction. It is an area.

  In such a fuel cell, the cross-sectional area of the fuel gas passage 74 at the central portion x in the power generation element stacking direction x of the cell stack 60a is larger than the cross-sectional area of the fuel gas passage 74 on the fuel gas supply pipe side of the cell stack 60a. Even if the temperature of the power generation element in the central portion of the power generation element stacking direction x increases, the pressure loss difference between the fuel gas passage 74 that supplies gas to the power generation element on the fuel gas supply pipe 80a side and the central portion of the power generation element stacking direction x is The amount of gas supplied to the power generation element stacking direction x center and the power generation element on the gas supply pipe side can be made substantially uniform.

  Further, as shown in FIG. 6, the cross-sectional area of the fuel gas passage 74 at the end portion in the fuel gas supply direction Y by the fuel gas supply pipe 80a is such that the fuel gas passage 74 is disconnected at the central portion x in the power generation element stacking direction x of the cell stack 60a. It is smaller than the area and larger than the cross-sectional area of the fuel gas passage 74 on the fuel gas supply pipe side of the cell stack 60a. Thereby, the pressure loss difference of the fuel gas passage 74 in the entire cell stack 60a can be reduced, and the fuel gas can be supplied to each power generating element of the cell stack 60a substantially uniformly.

  The to-be-reformed gas supply pipe 82a is connected to a to-be-reformed gas supply source (not shown) which may be a hydrocarbon gas such as city gas, and is connected to the reforming case 78a through the to-be-reformed gas supply pipe 82a. A gas to be reformed is supplied. An appropriate reforming catalyst for reforming the fuel gas into a hydrogen-rich fuel gas is accommodated in the reforming case 78a.

  In the illustrated embodiment, the reforming case 78a is connected to the fuel manifold 58a via the fuel gas supply pipe 80a and is thereby held at a required position. If necessary, the reforming case 78a is shown by a two-dot chain line in FIG. As shown in the drawing, for example, an appropriate support member 84a can be provided between the lower surface of the reformed gas supply pipe 82a and the lower surface or rear surface of the rear end portion of the fuel manifold 58a.

  Referring to FIG. 3, the power generation unit 56c is substantially the same as the power generation unit 56a described above, and the power generation units 56b and 56d are disposed in the front-rear direction opposite to the power generation units 56a and 56c. Fuel gas supply pipes (not shown) connecting the quality cases 78b and 78d and the fuel manifolds 58b and 58d are arranged on the rear side, and the reformed gas supply pipes 82b and 82d extend downward from the reforming case. , Extending under the housing 2 and out of the housing 2.

  In the fuel cell as described above, the gas to be reformed is supplied to the reforming cases 78a, 78b, 78c and 78d via the gas to be reformed supply pipes 82a, 82b, 82c and 82d, and the reforming cases 78a and 78b. , 78c and 78d, after being reformed into hydrogen-rich fuel gas, the fuel gas chambers defined in the fuel manifolds 58a, 58b, 58c and 58d are passed through the fuel gas feed pipes 80a, 80b, 80c and 80d. Are supplied in the longitudinal direction (stacking direction of the fuel cells), and then supplied to the power generation elements of the fuel cells 62 through the fuel gas passages 74 of the fuel cells 62 of the cell stacks 60a, 60b, 60c and 60d, respectively. Is done.

In each of the cells 62 of the cell stacks 60a, 60b, 60c and 60d,
1 / 2O ₂ + 2e ⁻ → O ²⁻ (solid electrolyte)
The electrode reaction of
O ²⁻ (solid electrolyte) + H ₂ → H ₂ O + 2e ⁻
The electrode reaction is generated and power is generated.

  Fuel gas and air that have flown upward from the cell stacks 60a, 60b, 60c and 60d without being used for power generation are ignited by an ignition means (not shown) disposed in the power generation / combustion chamber 12 at the time of startup. It is ignited and burned. As is well known, the power generation / combustion chamber 12 has a high temperature of, for example, about 800 ° C. due to power generation in the cell stacks 60a, 60b, 60c and 60d, and also due to combustion of fuel gas and air. The reforming cases 78a, 78b, 78c and 78d are disposed in the power generation / combustion chamber 12, and are positioned immediately above the cell stacks 60a, 60b, 60c and 60d, and are directly heated by the combustion flame. Thus, the high temperature generated in the power generation / combustion chamber 12 is effectively used for reforming the reformed gas.

  The combustion gas generated in the power generation / combustion chamber 12 flows into the discharge passage 30 from the discharge opening 42 formed in the heat exchanger 24, and flows through the discharge passage 30 extending in a zigzag shape. 50 is discharged through a discharge passage defined between the outer cylinder member 52 and the inner cylinder member 54. When the combustion gas flows through the discharge path in the double cylinder 50, air flows through the inflow path in the double cylinder 50, and heat exchange is performed between the combustion gas and air.

  Further, when the combustion gas is caused to flow in the exhaust passage 30 of the heat exchanger 24 in a zigzag manner, the air is caused to flow so as to face the inflow passage 32 of the heat exchanger 24 in a zigzag manner. Thus, heat is effectively exchanged between the combustion gas and air to preheat the air.

  When part or all of the cell stacks 60a, 60b, 60c and 60d deteriorates by performing power generation over a long period of time, the front heat insulation wall or the rear heat insulation wall of the housing 2 is detached or opened, and the power generation unit Part or all of 56a, 56b, 56c and 56d is taken out from the housing 2.

  Then, replace some or all of the power generation units 56a, 56b, 56c and 56d with new ones, or only the cell stacks 60a, 60b, 60c and 60d in some or all of the power generation units 56a, 56b, 56c and 56d. May be replaced with a new one and mounted again at a required position in the housing 2. Even when it is necessary to replace the reforming catalyst accommodated in the reforming cases 78a, 78b, 78c and 78d in some or all of the power generation units 56a, 56b, 56c and 56d, the power generation units 56a, 56b , 56c and 56d are removed from the housing 2, and the reforming cases 78a, 78b, 78c and 78d themselves in the power generation units 56a, 56b, 56c and 56d are replaced with new ones or reforming cases. Only the reforming catalyst in 78a, 78b, 78c and 78d may be replaced with a new one.

  In order to be able to perform the replacement of the reforming catalyst in the reforming cases 78a, 78b, 78c and 78d sufficiently easily, a part of the reforming cases 78a, 78b, 78c and 78d can be opened and closed if desired. It can be put on the door.

  On the other hand, air is supplied to the inflow path 32 of the heat exchanger 24 through the inflow path defined in the inner cylinder member 54 of the double cylinder 50, and is preheated (heated) through the heat exchanger 24. Is temporarily stored in the air chamber 16 and supplied between the cell stacks of the combustion / power generation chamber 12 through the air supply pipe 22a. At this time, the air supply pipe 22 a passes through the combustion gas atmosphere that burns in the vicinity of the fuel gas passage 74 at the upper end of the fuel cell 62 of the cell stack 60. Accordingly, the preheated air in the air chamber 16 is further heated in the combustion region above the cell stack 60, and the air heated to a high temperature is supplied to the cell.

  In particular, in the present invention, a large number of fuel cells 62 are electrically connected by the current collecting member 76. However, in such a fuel cell, the central portion in the power generation element stacking direction is easily heated, and thus the present invention is preferably used. be able to.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to such embodiments, and various modifications and corrections can be made without departing from the scope of the present invention. It goes without saying that this is possible.

  For example, the present invention has been described in relation to a fuel cell assembly having a specific reforming case above the cell stack. However, the present invention can be applied even when the reforming case is not located above the cell stack. I can do it. Moreover, the case where a reforming case is not provided in a housing may be sufficient.

  In the above embodiment, as shown in FIG. 2, a plurality of cylindrical air supply pipes 22a are arranged in a line and arranged between the cell stacks. However, instead of the plurality of cylindrical air supply pipes, Alternatively, a hollow plate-like air supply pipe may be used.

  Furthermore, in the above embodiment, the case where the fuel gas and air react and burn above the fuel battery cell has been described, but the present invention can be applied even when not burning, but in the case of the type to burn, Since the inside of the housing is likely to have a higher temperature, the present invention can be suitably used.

  Moreover, although the said form demonstrated the case where air was supplied toward the downward direction from opening of the lowest end using a cylindrical air supply pipe | tube, air is jetted to the fuel cell arrange | positioned to the side. Therefore, air may be ejected from the side surface of the cylindrical air supply pipe.

  Moreover, although the case where air is supplied from the upper side to the lower side using the air supply pipe has been described in the above embodiment, the present invention may be applied to the case where the air is supplied from the lower side to the upper side.

FIG. 7 shows another embodiment of the fuel cell according to the present invention. In this embodiment, the length of the fuel gas passage 74 at the center of the power stacking direction x of the cell stack 60a is the fuel gas supply of the cell stack 60a. The length of the fuel gas passage 74 on the pipe 80a side is shorter.

  The lengths of the power generating elements of the cell stack 60a are all the same. That is, in the fuel cell 62 at both ends in the power generation element stacking direction x, the oxygen electrode layer 70 is formed at the same height as the fuel cell 62 in the center of the power generation element stacking direction x. The length is formed long, and thus the length of the fuel gas passage 74 is formed long.

  In such a fuel cell, the length of the fuel gas passage 74 at the center of the power generation element stacking direction x of the cell stack 60a is shorter than the length of the fuel gas passage 74 on the fuel gas supply pipe side of the manifold 58a. Even if the temperature of the power generation element at the center of x increases, the pressure loss difference between the power generation element stacking direction x center and the fuel gas passage 74 for supplying gas to the power generation element on the fuel gas supply pipe 80a side can be reduced. In addition, the amount of gas supplied to the power generation element stacking direction x center and the power generation element on the gas supply pipe side can be made substantially uniform.

  Further, the length of the fuel gas passage 74 at the end portion in the fuel gas supply direction Y by the fuel gas supply pipe 80a is longer than the length of the fuel gas passage 74 at the central portion x in the power generation element stacking direction x of the cell stack 60a. By making the length shorter than the length of the fuel gas passage 74 on the fuel gas supply pipe side, the pressure loss difference of the fuel gas passage 74 in the entire cell stack 60a can be reduced, and the gas is supplied to each power generation element of the cell stack 60a. Can be supplied almost uniformly.

  FIG. 8 shows still another embodiment of the fuel cell according to the present invention. In this embodiment, a fuel gas passage 74 is provided at the lower end of the fuel cell 62 separately from the fuel gas passage 74 of the fuel cell 62. The cell fixing cap 90 having the connecting pipe 74a is previously sealed with a sealing material 91, a plurality of these are bundled together, and the cell stack 60a is configured by sealing and fixing to the manifold 58a with the same sealing material. To do. By changing the length of these connecting pipes 74a as shown in FIG. 8 or changing the cross-sectional area as shown in FIG. 9, the same effect as the above-described embodiment can be obtained, and the fuel in the entire cell stack 60a can be obtained. The pressure loss difference in the gas passage 74 can be reduced, and the gas can be supplied almost uniformly to the respective power generation elements of the cell stack 60a.

  Furthermore, since the connecting pipe 74a attached to the cell fixing cap can be made of an arbitrary metal member, the connecting pipe 74a in the central portion in the stacking direction x, which is expected to be high in temperature, has a coefficient of thermal expansion. Although it is composed of a large metal member and the temperature is expected to be low at the end portion in the fuel gas supply direction Y, there is a concern of a drop in pressure, so the heat of the connecting pipe 74a at the end portion in the fuel gas supply direction Y The expansion coefficient is made of a metal member having a thermal expansion coefficient smaller than that of the connecting pipe 74a at the center in the stacking direction x and larger than the thermal expansion coefficient of the connecting pipe 74a on the fuel gas supply pipe side, and temperature distribution during power generation It is possible to change the cross-sectional area of the connecting pipe 74a in accordance with the above, so that gas can be supplied to the cell stack 60a even at the time of power generation at a low temperature with little temperature distribution or at the time of startup without power generation. It can be substantially uniformly supplied to the power generation device Les.

  The present invention can also be applied to a flat plate fuel cell in which a plurality of power generating elements each having a fuel-side electrode formed on one side and an oxygen-side electrode formed on the other side are stacked. That is, in the flat plate fuel cell, a plurality of flat power generation elements are stacked, and the central portion in the power generation element stacking direction tends to become high temperature, so that the present invention can be suitably used. For example, a fuel electrode current collecting member that connects the separator and the fuel side electrode, or a gas passage is provided in the separator, and gas is supplied to the central portion of the power generating element through the gas passage. Since flowing toward the part is performed, the present invention can be suitably used.

Sectional drawing which shows suitable embodiment of the fuel cell of this invention. The arrangement | positioning pattern of the air supply pipe | tube seen from the air chamber is shown, (a) is a top view, (b) is a disassembled perspective view. The perspective view which shows the electric power generation unit aggregate | assembly currently used for the fuel cell of FIG. The perspective view which shows the electric power generation unit of FIG. Sectional drawing which shows the cell stack of FIG. The perspective view which shows the form which made the cross-sectional area of the fuel gas channel | path of the power generation element lamination direction center part larger than the fuel gas channel | path of both sides. The perspective view which shows the form which made the length of the fuel gas channel | path of the center part of a power generation element lamination direction longer than the fuel gas channel | path of both sides. (A) is a perspective view which shows the state which provided the fuel gas supply pipe | tube in the lower end part of the fuel cell, (b) is sectional drawing which shows the form which controlled the length of the fuel gas supply pipe | tube. Sectional drawing which shows the form which controlled the cross-sectional area of the fuel gas supply pipe | tube.

Explanation of symbols

58: Manifold 60: Cell stack 66: Fuel side electrode 68: Solid electrolyte 70: Oxygen side electrode 74: Gas passage 80: Gas supply pipe

Claims (4)

A cell stack in which a plurality of power generation elements each having a fuel side electrode formed on one side and an oxygen side electrode formed on the other side of the solid electrolyte are stacked, and the plurality of power generation elements are electrically connected. And a gas supply pipe provided at one end of the manifold, and the gas supplied to the manifold by the gas supply pipe is passed through the gas passage. Each of the fuel cells to be supplied to the power generation element, wherein a cross-sectional area of the gas passage at the central portion of the cell stack in the power generation element stacking direction is larger than a cross-sectional area of the gas passage on the gas supply pipe side of the cell stack. A fuel cell. The cross-sectional area of the gas passage at the gas supply direction end portion of the gas supply pipe is smaller than the cross-sectional area of the gas passage at the central portion of the cell stack in the power generation element stacking direction, and the gas passage on the gas supply pipe side of the cell stack 2. The fuel cell according to claim 1, wherein the fuel cell has a cross-sectional area larger than that of the fuel cell. A cell stack in which a plurality of power generation elements each having a fuel side electrode formed on one side and an oxygen side electrode formed on the other side of the solid electrolyte are stacked, and the plurality of power generation elements are electrically connected. And a gas supply pipe provided at one end of the manifold, and the gas supplied to the manifold through the gas supply pipe is communicated with the manifold. A fuel cell to be supplied to each of the power generation elements via a gas passage, wherein the length of the gas passage at the central portion of the cell stack in the power generation element stacking direction is greater than the length of the gas passage on the gas supply pipe side of the cell stack. A fuel cell characterized by a short length. The length of the gas passage at the gas supply direction end portion by the gas supply pipe is longer than the length of the gas passage at the central portion of the cell stack in the power generation element stacking direction, and the length of the gas passage on the gas supply pipe side of the cell stack. The fuel cell according to claim 3, wherein the fuel cell is shorter.

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