JP4705762B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell that generates electricity by reacting a hydrogen-rich fuel gas and an oxidizing gas, and more particularly to a fuel cell that includes a heat exchanger that preheats oxidizing gas with combustion exhaust gas accompanying power generation.

  One typical fuel cell is a solid oxide fuel cell (SOFC). In this fuel cell, there is a disk-shaped solid electrolyte with an electrode in which an anode electrode layer is formed on one surface of a thin and brittle circular solid electrolyte plate made of yttria stabilized zirconia and the like, and a cathode electrode layer is formed on the other surface. Used as a battery cell. Then, hydrogen-rich fuel gas flows from the inner peripheral portion to the outer peripheral portion through the anode side reaction space across the battery cell, and oxidizing gas such as air flows from the inner peripheral portion to the outer peripheral portion through the cathode side reaction space. By doing so, power generation is performed.

  Usually, a cylindrical cell stack in which disk-shaped interconnectors are stacked in the thickness direction is used so that reaction spaces are formed on both sides of the battery cell. The interconnector is made of stainless steel or the like, and is also called a separator because it also serves as a gas separation plate.

  One of the measures for improving the power generation efficiency in such a fuel cell is preheating of oxidizing gas. That is, in the fuel cell, as described above, high-temperature combustion gas is discharged to the outer peripheral side of the cell stack along with power generation in the cylindrical cell stack. By heat exchange between the high-temperature exhaust gas and the oxidizing gas introduced into the cell stack, the oxidizing gas is preheated and supplied to the battery cell. One fuel cell having such a preheating device is described in Patent Document 1.

EP13447529A2 specification

  In the fuel cell described in Patent Document 1, combustion gas flows from the cylindrical cell stack to the outer peripheral side through a horizontal spiral gas flow path formed in a plane perpendicular to the central axis of the cell stack. Discharged. In addition, the oxidizing gas is sent from the outer peripheral side to the central cell stack through another horizontal spiral gas channel formed adjacent to the horizontal spiral gas channel. Preheated by combustion gas.

  The fuel cell is also equipped with a preheating device for the cell stack separately from the oxidizing gas preheating device. That is, in the fuel cell, although the operation temperature differs depending on the type of fuel gas to be used, it is necessary to preheat the cell stack from normal temperature to the operation temperature at the start of operation. This preheating is generally performed by a gas burner provided below the battery cell. That is, the upper cell stack is heated by the gas burner provided below the cell stack, and preheated from the normal temperature to the operating temperature.

  However, when the oxidizing gas is preheated, a gas preheating heat exchanger is provided on the outer peripheral side of the cell stack, while a preheating device for the cell stack is provided below the cell stack. In the preheating device for the cell stack, not only a heating burner but also an exhaust system thereof is necessary, and there is a problem that the fuel cell is greatly increased in size because of the two preheating devices.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel cell capable of suppressing the battery scale as much as possible despite the provision of a preheating device for the cell stack, and further comprising an oxidation gas preheating device.

In order to achieve the above object, a fuel cell according to the present invention includes a cylindrical cell stack formed by stacking disk-shaped battery cells in the central axis direction, and exhaust gas discharged from the cell stack to the outer peripheral side. In order to preheat the oxidant gas, a cylindrical heat exchanger is provided on the outer peripheral side so as to surround the cell stack, and a preheating device is provided below the cell stack . In the heat exchanger, exhaust gas channels and oxidizing gas channels surrounding the cell stack are alternately arranged in the radial direction, and the exhaust gas channel is a vertical channel in a direction parallel to the cell stacking direction in the cell stack. The oxidant gas flow path is formed in a meandering manner from the outer peripheral part to the inner peripheral part in two lateral flow paths parallel to the circumferential direction of the cell stack. It is configured in a horizontal type combined with. Furthermore, the vertical exhaust gas flow path also serves as a flow path for exhaust gas discharged from the preheating device.

  In the fuel cell of the present invention, the exhaust gas preheating heat exchanger that surrounds the cell stack includes a vertical exhaust gas passage and a horizontal oxidizing gas passage. In particular, since the exhaust gas flow path is configured in a vertical shape in which the vertical flow paths are combined in a meandering manner from the inner peripheral portion to the outer peripheral portion, the exhaust gas of the preheating device installed below the cell stack is It can be efficiently discharged outside through the exhaust gas passage. That is, the vertical exhaust gas flow path in the exhaust gas preheating heat exchanger can also serve as the exhaust gas flow path in the cell preheating device, and the exhaust gas flow path in the cell preheating device is no longer required. It becomes possible.

  In addition, since the oxidizing gas flow path is configured in a horizontal shape in which two lateral flow paths parallel to the circumferential direction of the cell stack are serpentinely combined from the outer peripheral part to the inner peripheral part, the exhaust gas flow path and the oxidizing gas flow path Interference between the U-turn portions is eliminated, and the heat exchanger can be reduced in size.

  In order to increase the exhaust efficiency of the exhaust gas discharged from the cell preheating device, in the exhaust gas preheating heat exchanger, it is desired to form the vertical channel on the innermost peripheral side of the vertical exhaust gas channel upward. .

  In addition, for adjusting the temperature of the cell stack, a jacket for cooling the cell stack can be provided inside the exhaust gas preheating heat exchanger, and the catalyst can be used for exhaust gas preheating in order to heat the exhaust gas purification catalyst. It can also be incorporated into a longitudinal channel in the heat exchanger. By incorporating the catalyst, a dedicated heating device for heating the exhaust gas purification catalyst becomes unnecessary, and the fuel cell can be further miniaturized.

  The fuel cell of the present invention has an exhaust gas flow path of a heat exchanger provided on the outer peripheral side so as to surround the cell stack so as to preheat the oxidizing gas by the exhaust gas discharged from the cell stack to the outer peripheral side. The vertical flow path in the direction parallel to the cell stacking direction is a vertical type in which the inner circumferential portion is combined with the outer peripheral portion in a meandering manner, and the oxidizing gas flow path is a two-way horizontal flow path parallel to the circumferential direction of the cell stack. Can be efficiently discharged to the outside through the vertical exhaust gas flow path by using a horizontal type that is combined in a meandering manner from the outer periphery to the inner periphery. it can. That is, the vertical exhaust gas passage in the exhaust gas preheating heat exchanger can also serve as the exhaust gas passage in the cell preheating device. Thereby, although it is the structure provided with the preheating apparatus with respect to a cell stack and also the preheating apparatus of oxidizing gas, it can suppress a battery scale as much as possible.

  Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view of a fuel cell showing an embodiment of the present invention, and FIG. 2 is a transverse sectional view of the fuel cell.

  The fuel cell according to the present embodiment is provided on the outside of a cylindrical cell stack 10, a cylindrical cell container 20 that accommodates the cylindrical cell stack 10, a preheating device 30 provided below the cell container 20, and the cell container 20. And an annular heat exchanger 40. The heat exchanger 40 is a preheating device for air supplied to the cell stack 10.

  The cell stack 10 is a solid electrolyte type in which a circular electrode-attached solid electrolyte plate is sandwiched between each of a plurality of disk-shaped interconnectors as battery cells. The cell stack 10 is supplied with air as an oxidizing gas from above through the air supply pipe 11. Also, a hydrocarbon fuel gas such as city gas is supplied from above through a fuel pipe (not shown) around the center.

  The fuel gas supplied into the cell stack 10 after the partial oxidation reforming or steam reforming flows through the reaction space on the anode side formed on the one surface side of the battery cell from the inner periphery to the outer periphery. Moreover, the air supplied into the cell after preheating by the heat exchanger 40 circulates from the inner peripheral portion to the outer peripheral portion in the cathode-side reaction space formed on the other surface side of the battery cell. As a result, power is generated in the cell stack 10, and as a result, the combustion gas is discharged from the cell stack 10 to the outer peripheral side.

  The cell container 20 is a cylindrical hermetic container whose upper and lower surfaces are closed, and is fixed on a cylindrical base 21. The cell container 20 is made of a heat-resistant metal such as stainless steel that can withstand high-temperature combustion exhaust gas. A plurality of gas discharge holes 22, 22,... Are provided at predetermined intervals in the circumferential direction at the lowermost portion of the cell container 20, more specifically at the lowermost portion of the cylindrical body.

  The preheating device 30 includes a cylindrical cover 31 provided around the gantry 21 that supports the cell container 20. The cover 31 forms an annular preheating chamber 32 between the inner base 21 and the cover 31. The preheating chamber 32 communicates with the upper heat exchanger 40, and an annular ring burner 33 is provided inside the preheating chamber 32 so as to surround the gantry 21. The ring burner 33 mainly heats the outer peripheral surface of the cell container 20 at the start of operation, and preheats the battery cells 10 in the container from normal temperature to the operating temperature. 34 is a fuel supply pipe for supplying fuel to the ring burner 33, 35 is an ignition flag, and 36 is a flame detection plug.

  The heat exchanger 40 is a thick cylindrical body surrounding the cell container 20, and has an annular jacket 41 in contact with the outer peripheral surface of the cell container 20 at the innermost peripheral part. On the outside of the jacket 41, a plurality of annular exhaust gas passages 42, 42,... Whose diameter increases stepwise is formed concentrically with a predetermined gap. Further, a plurality of annular oxidizing gas passages 43, 43,..., Whose diameter increases stepwise, are formed between the adjacent exhaust gas passages 42,.

  Here, the heat exchanger 40 has a configuration in which the exhaust gas passages 42, 42,..., And the oxidizing gas passages 43, 43,. That is, the exhaust gas passages 42, 42,... And the oxidizing gas passages 43, 43,... Have a structure in which an annular one is divided into two in the circumferential direction.

  In one semicircle portion of the heat exchanger 40, as shown in FIG. 1, among the plurality of arc-shaped exhaust gas channels 42, 42,..., The innermost exhaust gas channel 42 located outside the jacket 41 is , An upward flow path for flowing the exhaust gas from the bottom to the top, and the lower end portion of the exhaust gas in the cell container 20 via a plurality of gas discharge holes 22, 22. It communicates with the lower preheating chamber 32.

  The second exhaust gas flow channel 42 from the inside is a downward flow channel through which the exhaust gas flows from the top to the bottom, and the upper ends of the first exhaust gas flow channel 42 communicate with each other. Similarly, the upward channel and the downward channel are alternately arranged, and the lower ends and the upper ends are alternately communicated. As a result, the plurality of exhaust gas flow paths 42, 42,... In one semicircular portion are combined in a meandering manner from the inner peripheral portion to the outer peripheral portion in the vertical direction in the direction parallel to the cell stacking direction in the cell stack 10. It is a vertical type.

  The outermost exhaust gas flow path 42 is an upward flow path, and exhaust gas is discharged to the outside from an exhaust pipe 44 attached to the upper surface of the outer peripheral portion of the heat exchanger 40 via a header portion (not shown). . A wide exhaust gas flow channel 42 is formed in the radial intermediate portion of the heat exchanger 40. An exhaust gas purification catalyst 50 is disposed in the exhaust gas passage 42.

  In the other semicircular part of the heat exchanger 40, as in the case of the one semicircular part, the plurality of arc-shaped exhaust gas flow paths 42, 42,... Are upward flow paths in a direction parallel to the cell stacking direction in the cell stack 10. The exhaust gas purification catalyst 50 is disposed in the intermediate exhaust gas flow channel 42. The exhaust gas purification catalyst 50 is disposed in the middle exhaust gas flow channel 42 in a meandering manner.

  On the other hand, as shown in FIG. 2, the oxidizing gas channels 43, 43... Have an oxidizing gas in the outermost arc-shaped oxidizing gas channel 43 in one semicircular portion of the heat exchanger 40. The air that is is circulated to one side in the circumferential direction. Air is introduced into the oxidant gas channel 43 from the air introduction pipe 46 attached to the upper surface of the outer periphery of the heat exchanger 40 via the header 47.

  In the second oxidizing gas flow path 43 from the outside, the oxidizing gas air flows to the other circumferential direction. That is, air passes in the opposite direction to the first oxidizing gas channel 43. For this reason, the first oxidizing gas channel 43 and the second oxidizing gas channel 43 are in communication with each other at one side end. In the same manner, the flow paths having different directions in the circumferential direction are alternately arranged, whereby the plurality of oxidizing gas flow paths 43, 43... In one semicircular portion are parallel to the circumferential direction of the battery cell 10. It is a horizontal type in which two lateral flow paths are combined in a meandering manner from the outer peripheral portion to the inner peripheral portion.

  The innermost oxidizing gas passage 43 has a downstream side end communicating with an air outlet pipe 48 attached to the upper surface of the inner peripheral portion of the heat exchanger 40 via a header portion 49. The air flowing through the oxidant gas channels 43, 43,... Is discharged from the air outlet pipe 48 to the outside.

  Also in the other semicircular part of the heat exchanger 40, the plurality of arc-shaped oxidizing gas flow paths 43, 43,... It is configured as a horizontal type in which the paths are combined in a meandering manner from the outer peripheral portion to the inner peripheral portion.

  Note that cooling air is introduced into an annular jacket 41 provided outside the cell container 20 from an air introduction pipe 45 attached to the upper surface of the inner peripheral portion of the heat exchanger 40. The air flowing through the jacket 41 flows into the innermost exhaust gas flow path 42.

  The exhaust pipe 44 and the air outlet pipe 48 are separately provided in the two semicircular parts of the heat exchanger 40, but the air introduction pipes 45 and 46 are shared by the two semicircular parts of the heat exchanger 40. ing. The air introduction tube 45 is provided on the opposite side across the center of the heat exchanger 40. The air introduction pipe 46 and the air outlet pipes 48, 48 are provided on the same side with respect to the center of the heat exchanger 40.

  Next, the function of the fuel cell of this embodiment will be described.

  When the cell stack 10 is operated, the outer peripheral surface of the cell container 20 is mainly heated by the ring burner 33 in the preheating device 30, and the cell stack 10 in the container is preheated from room temperature to the operating temperature. The combustion exhaust gas generated at this time passes through the exhaust gas passages 42, 42,... In the heat exchanger 40 in order from the inner peripheral portion to the outer peripheral portion and is discharged to the outside.

  Here, the exhaust gas passages 42, 42,... In the heat exchanger 40 are combined in a meandering manner from the inner peripheral portion to the outer peripheral portion of the upward flow passage and the downward flow passage in a direction parallel to the cell stacking direction in the cell stack 10. In particular, the innermost exhaust gas flow path 42 into which the combustion exhaust gas first flows is an upward flow path. For this reason, the combustion exhaust gas accompanying preheating is smoothly discharged from the preheating chamber 32 to the outside through the exhaust gas passages 42, 42,... In the heat exchanger 40.

  That is, the exhaust gas passages 42, 42,... In the heat exchanger 40 are used as exhaust gas passages during preheating. For this reason, the exhaust system for exhaust gas is not required in the preheating device 30, and in this respect, the fuel cell can be reduced in size.

  When the cell stack 10 is preheated, air is also supplied to the cathode side of the battery cell. This air is introduced into the heat exchanger 40 from the air introduction pipe 46, and further passes through the oxidizing gas passages 43, 43,... In the heat exchanger 40 from the outer peripheral portion to the inner peripheral portion, and then the air outlet pipe 48. , 48 are once discharged out of the heat exchanger 40 and then supplied to the cell stack 10 in the cell container 20.

  Here, the oxidizing gas passages 43, 43,... Are located between the exhaust gas passages 42, 42,. Therefore, the air flowing from the outside through the oxidizing gas passages 43, 43,... Is heat-exchanged with the combustion exhaust gas flowing from the inside through the exhaust gas passages 42, 42,. And since this preheated air is supplied to the cell stack 10, the preheating of the cell stack 10 is promoted.

  Here, the oxidizing gas flow paths 43, 43,... In the heat exchanger 40 are different from the vertical exhaust gas flow paths 42, 42,. It is configured in a horizontal shape that is combined in a meandering manner from the outer periphery to the inner periphery. For this reason, there is no interference between the U-turn portions between the two, and as a result, the heat exchanger 40 is also downsized.

  When the cell stack 10 reaches the operating temperature, the reformed fuel gas is supplied to the anode side of the battery cell at a predetermined flow rate. At the same time, a predetermined flow rate of air is supplied as an oxidizing gas to the cathode side of the battery cell. This air is introduced into the heat exchanger 40 from the air introduction pipe 46, and further passes through the oxidizing gas flow paths 43, 43,... The tubes 48 and 48 are once discharged out of the heat exchanger 40 and then supplied to the cell stack 10 in the cell container 20.

  At this time, high-temperature combustion gas is discharged from the cell stack 10 to the outer peripheral side as exhaust gas. This exhaust gas flows from the lower part of the cell container 20 through the gas discharge holes 22, 22. The exhaust gas passes through the exhaust gas passages 42, 42,... In the heat exchanger 40 in order from the inner peripheral part to the outer peripheral part and is discharged from the exhaust pipe 44 to the outside in the same manner as the combustion exhaust gas at the time of preheating. Thus, the air passing through the oxidizing gas flow paths 43, 43,... From the outer peripheral portion to the inner peripheral portion is heated with the exhaust gas. The heated air is once discharged out of the heat exchanger 40 from the air outlet pipe 48 and then supplied to the cell stack 10 in the cell container 20.

  It is well known that the power generation efficiency is increased by such preheating of the oxidizing gas.

  When the temperature of the battery cell 10 rises excessively during power generation, cooling air is introduced from the air introduction tube 45 to the jacket 41 in the heat exchanger 40. Thereby, the cell container 20 is cooled from the outside, and the cell stack 10 in the container is maintained at an appropriate temperature. The air after being used for cooling merges with the exhaust gas and is discharged out of the heat exchanger 10.

  Thus, in the fuel cell of this embodiment, the air as the oxidizing gas is preheated by the high-temperature exhaust gas discharged from the cell stack 10 by the heat exchanger 40 provided on the outer peripheral side of the cell container 20.

  Prior to the start of operation, the cell stack 10 in the cell container 20 is preheated to the operating temperature by the lower preheating device 30, and the combustion exhaust gas passes through the exhaust gas passages 42, 42... In the heat exchanger 40. Discharged outside. For this reason, the preheating device 30 does not require an exhaust system and is miniaturized. Further, since the combustion exhaust gas preheats the air supplied to the cathode during preheating, the preheating efficiency is improved.

  In particular, the exhaust gas flow paths 42, 42,... In the heat exchanger 40 are longitudinally formed by combining an upward flow path and a downward flow path parallel to the stacking direction of the cell stack 10 in a meandering manner from the inner periphery to the outer periphery. Since it is configured in a mold, high exhaust efficiency is ensured for both exhaust gas during operation and exhaust gas during preheating.

  Further, the oxidizing gas flow paths 43, 43,... In the heat exchanger 40 are configured in a horizontal type in which two lateral flow paths parallel to the circumferential direction of the cell stack 10 are serpentinely combined from the outer peripheral portion to the inner peripheral portion. Has been. For this reason, there is no interference between the U-turn portions between the exhaust gas passages 42, 42,... And the oxidizing gas passages 43, 43, etc., and the heat exchanger 40 is also downsized.

  Furthermore, in the fuel cell according to the present embodiment, the catalyst 50 for purifying the exhaust gas is disposed in the middle of the exhaust gas flow paths 42, 42,. Since the exhaust gas temperature is 150 ° C. or higher at this position, the exhaust gas purification catalyst 50 is heated to an appropriate temperature using the exhaust gas. For this reason, an apparatus for heating the catalyst 50 is not necessary, and the battery scale is reduced from this point.

  In this embodiment, the exhaust gas passages 42, 42,... And the oxidizing gas passages 43, 43,... In the heat exchanger 40 have a structure in which an annular one is divided into two in the circumferential direction. The structure may be divided into three or four or more, and may be an annular integral structure.

  FIG. 3 is a longitudinal sectional view of a fuel cell showing another embodiment of the present invention, and FIG. 4 is a transverse sectional view of the fuel cell.

  The fuel cell according to the present embodiment includes four cell stacks 10, 10,. The four cell stacks 10, 10,... Are accommodated in the four cell containers 20, 20,. The heat exchanger 40 is shared between the four cell stacks 10, 10... And has an annular shape surrounding the four cell containers 20, 20.

  More specifically, in the heat exchanger 40, the jacket 41, the innermost exhaust gas passage 42, and the oxidizing gas passage 43 independently surround the cell containers 20, 20,. .. And the oxidizing gas passages 43, 43,... Collectively surround the four cell containers 20, 20,. However, functionally, the exhaust gas passages 42, 42,... And the oxidizing gas passages 43, 43,... Shared by the four cell stacks 10, 10,. And it is divided into four in the circumferential direction.

  Although not shown, the four cell stacks 10, 10,... Are independently preheated by a preheating device provided below each of the four cell containers 20, 20,.

  Also in the fuel cell of this embodiment, the heat exchanger 40 preheats the air as the oxidizing gas with the high-temperature exhaust gas discharged from the four battery cells 10, 10.

  Further, since the exhaust gas passages 42, 42,... In the heat exchanger 40 also serve as an exhaust system for the preheating device, the battery scale is reduced. The exhaust gas passages 42, 42,... In the heat exchanger 40 are vertical types in which an upward passage and a downward passage in a direction parallel to the stacking direction of the battery cells 10 are combined in a meandering manner from the inner peripheral portion to the outer peripheral portion. Therefore, exhaust gas emission efficiency is high.

  On the other hand, the oxidizing gas passages 43, 43,... In the heat exchanger 40 are different from the vertical exhaust gas passages 42, 42,. It is a horizontal type combined in a meandering manner from the inner part to the inner peripheral part. For this reason, the heat exchanger 40 also becomes small.

  Furthermore, since the exhaust gas purification catalyst is disposed in the exhaust gas flow path 42 in the heat exchanger 40 and this catalyst is heated using the exhaust gas, the fuel cell is reduced in size from this point.

  Also in this embodiment, the number of divisions of the exhaust gas passages 42, 42... And the oxidizing gas passages 43, 43.

It is a longitudinal cross-sectional view of the fuel cell which shows one Embodiment of this invention. It is a cross-sectional view of the fuel cell. It is a longitudinal cross-sectional view of the fuel cell which shows other embodiment of this invention. It is a cross-sectional view of the fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cell stack 20 Cell container 22 Gas discharge hole 30 Preheating apparatus 32 Preheating chamber 33 Ring burner 40 Heat exchanger 41 Jacket 42 Exhaust gas flow path 43 Oxidation gas flow path 44 Exhaust pipe 45, 46 Air introduction pipe 47, 49 Header part 48 Air Outlet pipe 50 Exhaust gas purification catalyst

Claims (4)

A cylindrical cell stack formed by stacking disk-shaped battery cells in the central axis direction, and surrounding the cell stack in order to preheat the oxidizing gas by the exhaust gas discharged from the cell stack to the outer peripheral side A cylindrical heat exchanger provided on the outer peripheral side thereof, and a preheating device provided below the cell stack, the exhaust gas flow path surrounding the cell stack and the oxidizing gas flow in the heat exchanger The paths are alternately arranged in the radial direction, and the exhaust gas flow path is configured in a vertical type in which the vertical flow paths in a direction parallel to the cell stacking direction in the cell stack are combined in a meandering manner from the inner periphery to the outer periphery. The oxidizing gas flow path is configured in a horizontal shape in which two lateral flow paths parallel to the circumferential direction of the cell stack are serpentinely combined from the outer peripheral portion to the inner peripheral portion, and the vertical exhaust gas flow passage is From preheater Fuel cell, characterized in that also serves as a flow path of the exhaust gas out. 2. The fuel cell according to claim 1 , wherein a vertical channel on the innermost circumferential side of the vertical exhaust gas channel is formed upward to introduce the exhaust gas discharged from the preheating device. The fuel cell according to claim 1 or 2 , further comprising a jacket for cooling the battery cell, further inside the heat exchanger. The fuel cell according to any one of claims 1 to 3, wherein an exhaust gas purifying catalyst is provided in an intermediate portion of the longitudinal channel in the heat exchanger.

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