JP5239174B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell including an upper fuel heat exchanger that can efficiently mix fuel gas and water vapor.

  In recent years, research and development of solid oxide fuel cells having many advantages such as high power generation efficiency and effective use of exhaust heat due to high operating temperature have been promoted as the fuel cells.

  Such a solid oxide fuel cell generally includes a fuel cell stack in which power generation cells and separators are alternately stacked in a housing whose outer periphery is covered with a heat insulating material. As shown in FIG. 5, the power generation cell 11 has a fuel electrode layer 22 formed on one surface of the solid electrolyte layer 21 and an air electrode layer 23 formed on the other surface. A fuel electrode current collector 32 is disposed outside the fuel electrode layer 22, and an air electrode current collector 33 is disposed outside the air electrode layer 23. A channel 12a and an oxidant channel 12b are formed.

  In the solid oxide fuel cell, hydrogen gas moves from the fuel electrode current collector 32 to the fuel electrode layer 22 through the fuel gas channel 12 a formed in the separator 12, and emits electrons in the fuel electrode layer 22. At the same time, the oxygen gas moves from the air electrode current collector 33 through the oxidant flow path 12b to the air electrode layer 23, and further to the solid electrolyte layer 21 in the air electrode layer 23. It becomes. Then, the oxide ions reach the solid electrolyte layer 21, diffuse in the electrolyte layer 21 toward the fuel electrode layer 22, react with hydrogen gas to generate water, and generate the fuel electrode layer 22. To emit electrons. As a result, the solid oxide fuel cell can take out the electrons as an electromotive force and employs a sealless structure. Therefore, the residual gas that has not been used in the power generation reaction described above and the water vapor due to the water are used. Is released to the outside. (For example, patent document 1).

JP 2004-335164 A

  By the way, as shown in FIG. 6, the solid oxide fuel cell includes a plurality of rows of stack units in which fuel cell stacks 13 each including the plurality of power generation cells 11 are stacked in a height direction. By arranging it, further increase in power generation efficiency can be expected. In this case, the solid oxide fuel cell includes a fuel gas supply means 9 for supplying the power generation cell 11 with a reformed fuel gas to hydrogen gas, and an oxidant supply for supplying an oxidant such as oxygen to the power generation cell 11. Means 5 are connected to the fuel cell stack 13 of the stack unit in each row.

  The fuel gas supply means 9 is connected to a water vapor supply pipe 41 for supplying water vapor generated in the water vapor generator 40 at an upstream portion thereof, so as to increase the reforming temperature in order to increase the conversion rate to hydrogen gas. A side fuel heat exchanger 93 is interposed on the side of the fuel cell stack 13, and an upper fuel heat exchanger disposed above the fuel cell stack 13 on the downstream side of the side fuel heat exchanger 93. A device 96 is interposed. A reforming catalyst 92 is built in on the downstream side of the upper fuel heat exchanger 96. The reformer 92 reforms the fuel gas into hydrogen gas by an endothermic reaction with water vapor and distributes and supplies the hydrogen gas to the stack units. It is intervened. On the other hand, the oxidant supply means 5 includes an upper air heat exchanger 50 disposed above the fuel cell stack 13, and a side air heat exchanger 53 provided on the upstream side of the upper air heat exchanger 50. Is intervening.

  In addition, since the solid oxide fuel cell requires a temperature of 400 ° C. to 500 ° C. for the reaction in the power generation cell 11 described above, a heating device 97 such as an electric heater or a burner is disposed around the stack 13. Has been. The heating device 97 indirectly heats the upper fuel heat exchanger 96 and the upper air heat exchanger 50 made of a flat can body by heating the air in the housing 20 at the time of startup and rising as high-temperature heated air. The side fuel heat exchanger 93 and the side air heat exchanger 53 are directly or indirectly heated. As a result, the solid oxide fuel cell has a fuel gas or air heated by the side fuel heat exchanger 93 and the upper fuel heat exchanger 96 or by the side air heat exchanger 53 and the upper air heat exchanger 50. The temperature of the fuel cell stack 13 is increased to the above temperature by raising the temperature, high-temperature heated air in the housing 20, or the like.

  In the solid oxide fuel cell, the residual gas and water vapor released after startup are absorbed by the upper fuel heat exchanger 96, the side fuel heat exchanger 93, etc., and the fuel gas and the like are heated. Therefore, the reformer 92 is reformed into hydrogen gas by an endothermic reaction with water vapor, and is supplied to each fuel cell stack 13.

  However, since the upper fuel heat exchanger 96 is made of a flat can body, the fuel or the like is immediately discharged to the reformer 92, the heating time is short, and the fuel gas or the like is effectively produced by the high-temperature heated air or the like in the housing 20. Heating is not possible, and the conversion rate of the fuel gas into hydrogen gas in the reformer 92 is reduced, resulting in a reduction in power generation efficiency.

  Furthermore, since the fuel gas is supplied to the reformer 92 in a state where the fuel gas is not sufficiently mixed with the water vapor, the ratio of the fuel gas and the water vapor changes, and the fuel gas in the reformer 92 changes. Fluctuation occurs in the conversion rate to hydrogen gas, and the supply ratio of hydrogen gas to each stack unit changes. For this reason, since it becomes impossible to control the reaction efficiency of the above-mentioned power generation cells 11 in each fuel cell stack 13, the power generation efficiency of all the fuel cell stacks 13 cannot be maximized, resulting in the power generation efficiency. There was a problem of inviting a decline.

  Therefore, the present invention has an upper fuel heat exchanger that can effectively heat the fuel gas and the like by the high-temperature heated air at the upper part of the housing, and that sufficiently mixes the fuel gas and water vapor. It is an object of the present invention to provide a fuel cell that can prevent a decrease in efficiency.

That is, the present invention described in claim 1 includes a plurality of fuel cell stacks in which power generation cells and separators are alternately stacked in a housing whose outer periphery is covered with a heat insulating material, and fuel in these fuel cell stacks. A fuel gas supply means provided with a reformer for supplying gas by reforming it into hydrogen by an endothermic reaction with water vapor; and interposed between the fuel gas supply means and disposed above the fuel cell stack; A fuel cell in which an upper fuel heat exchanger having a flat can that heats the fuel gas and water vapor by absorbing the heat in the housing and flowing the fuel gas and water vapor therein is housed In the upper fuel heat exchanger, the fuel gas and the water vapor formed on the outer periphery of the can body and supplied from the fuel gas supply means through the supply port formed on the wall surface of the can body. The by Rukoto to pivot in the circumferential direction of the first chamber to the gas mixture in which the fuel gas and the steam are mixed efficiently formed in a central portion of the can body, the fuel gas supplied to the gas mixture a second chamber supplied to the reformer unit is partitioned by the partition member Rutotomoni, in the partition member, the communication port for flowing the mixed gas of the first chamber to the second chamber It is characterized by being formed .

  According to a second aspect of the present invention, there is provided the fuel cell according to the first aspect, wherein the upper fuel heat exchanger is configured such that the can body is formed in a rectangular shape in plan view and the supply to each corner portion. The mouth is formed so as to supply the fuel gas and the water vapor toward the swirl direction, the partition member is formed in the shape of a ceiling tube, and the lower part is formed integrally with the bottom of the can body. The communication port is formed in the ceiling, and the second chamber is formed between the partition member and the bottom of the can body, and faces the communication port in the bottom of the can body. Besides the position, an opening for discharging the mixed gas is formed.

  The invention according to claim 3 is the fuel cell according to claim 2, wherein the fuel gas supply means reforms the fuel gas into hydrogen downstream of the upper fuel heat exchanger, and A reformer that distributes and supplies fuel cells to a plurality of fuel cell stacks is connected, and the reformer is formed with a plurality of discharge ports that supply and distribute, and a supply port that communicates with each of the discharge ports. The upper fuel heat exchanger has a plurality of openings corresponding to the supply ports.

According to the invention described in any one of claims 1 to 3, the fuel gas and the water vapor are supplied to the first chamber and swirled and mixed in the circumferential direction. Thus, the gas mixture can be made into a mixed gas, and the fuel gas and water vapor can be heated by the high-temperature heated air in the housing during the swirl mixing. Next, the mixed gas flowing in from the communication port of the partition wall member can be supplied to the fuel cell stack through the fuel gas supply means by the internal pressure of the second chamber.
As a result, since the fuel gas and water vapor are sufficiently mixed, there is no fluctuation in the conversion rate of the fuel gas in the reformer, and in addition, the fuel gas is improved by sufficient heating time during swirl mixing. Since the material temperature can be increased and a sufficiently high conversion rate can be obtained, the power generation efficiency can be increased.

  In particular, according to the second aspect of the present invention, the supply port is formed at each corner of the upper fuel heat exchanger so that the fuel gas and the water vapor are supplied in the swirling direction. The fuel gas and water vapor can be mixed efficiently without disturbing the flow. In addition, the communication port is formed in the ceiling portion of the celestial tubular partition member, and the lower portion of the partition member is integrally provided with the bottom portion of the can body, so that the fuel gas or the like is sufficiently circumferentially provided in the first chamber. Only when swirled and mixed to form a mixed gas flows to the ceiling in the center in the plane direction, it flows into the second chamber from the communication port. Fuel gas etc. can be heated. For this reason, the fluctuation | variation of a conversion rate can be prevented more reliably and the raise of a conversion rate can be promoted.

  Further, the upper fuel heat exchanger mixes and heats the fuel gas and the like so that the change in the conversion rate of the fuel gas in the reformer is prevented and a sufficiently high conversion rate is obtained as described above. The reformer connected downstream as in the invention described in claim 3 reforms the fuel gas into hydrogen and has a plurality of discharge ports for distribution and supply to the plurality of fuel cell stacks. Even when each of the supply ports connected to the outlet has a plurality of openings of the upper fuel heat exchanger corresponding to each supply port, hydrogen is uniformly supplied to each fuel cell stack, The power generation efficiency of the battery stack can be maximized. For this reason, the electromotive force obtained from each fuel cell stack can be increased as a whole by increasing the supply amount of fuel gas, increasing the heating temperature, or the like.

  Next, the best embodiment of the solid oxide fuel cell including the upper fuel heat exchanger according to the present invention will be described with reference to FIGS. In addition, about the same thing as the above-mentioned general fuel cell, description is abbreviate | omitted by using the same code | symbol.

  In the solid oxide fuel cell according to the present embodiment, a housing 20 containing a power generation element such as a fuel cell stack 13 is provided in an external can body 2 having a rectangular shape in plan view with an open bottom. A heat insulating member (heat insulating material) 10 is interposed between 20 and the outer can body 2.

  The fuel cell stack 13 constitutes a stack unit by stacking a plurality of stages (four stages in the present embodiment) in the height direction with the mount 18 interposed therebetween, and the stack unit is The fuel cell stacks 13 are arranged in two rows in the center in the housing 20 in a plan view, and the fuel cell stacks 13 are arranged at desired positions along the side wall surfaces of the housing 20 at the center of the fuel cell stack 13 in the height direction. The four heating devices 7 are heated.

  The solid electrolyte layer 21 constituting the power generation cell 11 of the fuel cell stack 13 is made of stabilized zirconia (YSZ) or the like to which yttria is added, and the fuel electrode layer 22 is made of a metal such as Ni or a cermet such as Ni-YSZ. The air electrode layer 23 is made of LaMnO 3, LaCoO 3 or the like, the fuel electrode current collector 32 is made of a sponge-like porous sintered metal plate such as Ni, and the air electrode current collector 33 is made of a sponge such as Ag. The separator 12 is made of stainless steel or the like.

  The fuel gas supply means 4 for supplying the fuel gas to the power generation cell 11 as hydrogen gas is provided with a fuel gas supply pipe 49 for introducing the fuel gas upstream thereof, and the fuel gas supply pipe 49 The outer side of the housing 20 is disposed in the housing 20 and is branched into four branches. The fuel gas supply pipe 49 is joined to a water vapor supply pipe 41 for supplying water vapor to each branch pipe, and a side fuel heat exchanger 43 disposed in the housing 20 at the downstream end thereof. Is connected.

  The side fuel heat exchanger 43 is disposed along each side of the housing 20, is continuously provided in the fuel gas supply pipe 49, and is vertically disposed in the vicinity of each heating device 7. The pipes 43a are continuously formed in the pipes 43a, and the casing 43b has a rectangular plate-like appearance as viewed from the top along the sides of the housing 20 at the top of the housing 20. Has been. The connecting pipes 44 are connected to the upper parts of the housings 43b, and the connecting pipes 44 are connected to the upper fuel heat exchanger 6 disposed horizontally at the upper part in the housing 20.

  As shown in FIGS. 3 and 4, the upper fuel heat exchanger 6 has a flat can body 60 having a rectangular plate shape in appearance, in which a chamber in which fuel gas or the like flows is formed in an airtight manner. A connecting pipe 44 is connected to each corner of the elongated side wall of the can body 60 so that fuel gas and water vapor can flow in in a clockwise direction.

  In the can body 60, a horizontal rectangular plate constituting the can body 60 is formed between the top plate 60a and the bottom plate 60b so as to be slightly smaller than the top plate 60a and the bottom plate 60b. A partition wall member 63 including a partition wall plate 61 provided and a side plate 62 that protrudes downward from the outer periphery of the partition wall plate 61 and is provided integrally with the bottom plate 60 b is provided.

  Further, the upper fuel heat exchanger 6 has a communication port 61a formed in the central portion of the partition plate 61 and has four pin-shaped strength holding members 64 penetrating the partition plate 61. Both ends of the strength holding member 64 are provided integrally with the top plate 60 a and the bottom plate 60 b, and are disposed at rectangular corners having an outer method that is slightly smaller than the outer periphery of the partition wall member 63.

  Thus, in the upper fuel heat exchanger 6, a first chamber 65 is formed between the partition wall member 63 and the top plate 60a to swirl and mix the fuel gas and water vapor in the circumferential direction to form a mixed gas, The first chamber 65 includes a rectangular annular swirl passage 65a formed in the circumferential direction along the side wall of the can body 60, and the top plate 60a and the partition wall of the can body 60 continuously to the swirl passage 65a. And a flow path 65b formed in a gap with the plate 61.

Further, the upper fuel heat exchanger 6 is isolated from the first chamber 65 inside thereof, and a second chamber 66 for temporarily storing a mixed gas or the like is formed between the partition wall member 63 and the bottom plate 60b. The first chamber 65 and the second chamber 66 are airtightly partitioned by the partition wall member 63. In the second chamber 66, openings 66a to 66d are formed at positions other than the position facing the communication port 61a in the bottom plate 60b, and supply pipes 45a to 45d communicating with the openings 66a to 66d are connected to the second chamber 66, respectively.
As a result, the second chamber 66 discharges the mixed gas or the like through the supply pipes 45a to 45d to the reformer 42 connected to the downstream end of the supply pipes 45a to 45d due to the internal pressure. Yes.

  The reformer 42 has a cross shape having flat box-shaped wing portions 42a, 42b, 42c, and 42d each containing a reforming catalyst between opposing side surfaces of the stack units arranged in two rows. The fuel reformer 30 is disposed from the uppermost fuel cell stack 13 to a position close to the lowermost fuel cell stack 13. The wing portions 42a to 42d are connected to the supply pipes 45a to 45d communicating with the supply ports at the upper end portions, respectively, and the discharge ports communicating with the supply ports are formed at the distal end portions on the housing 20 side. In addition, elongated fuel buffer tanks 47a to 47d disposed in the vertical direction are connected to the respective discharge ports so as to communicate with each other. Thereby, the blade parts 42a to 42d reform the mixed gas supplied from the supply pipes 45a to 45d into hydrogen gas and supply the hydrogen gas to the fuel buffer tanks 47a to 47d. The buffer tanks 47a to 47d are connected to the fuel cell stack 13 via the manifold 48.

  As a result, the fuel gas supply means 4 is arranged on the downstream side of the fuel gas supply pipe 49 in this order from the upstream side to the downstream side, in order, from the side fuel heat exchanger 43, the connecting pipe 44, and the upper fuel heat exchanger 6. The supply pipes 45a to 45d and the reformer 42 are interposed.

  On the other hand, the oxidant supply means 5 for supplying oxygen gas to the power generation cell 11 includes an air supply pipe 59 disposed in the housing 20 from the outside of the housing 20, and a downstream portion of the air supply pipe 59. Are branched into four and connected to the side air heat exchanger 53 respectively.

These side air heat exchangers 53 are roughly constituted by pipes arranged vertically along the respective corners of the housing 20 in the vicinity of each heating device 7, and are connected to the upper ends of these pipes, respectively. An upper air heat exchanger 50 is connected via a pipe 51.
The upper air heat exchanger 50 is formed of a flat can body having a rectangular flat plate shape as viewed from the outside, and the downstream side thereof is connected to the fuel cell stack 13 via a buffer tank 52.

  Further, on the outer periphery of the stack unit, which is arranged in two rows in the vertical and horizontal directions, the heat shield plate 8 is laminated at the center in the height direction in the housing 20 along the respective side surfaces of the housing 20 between the heating device 7 and the outer periphery. Six pieces are arranged so as to cover the second and third fuel cell stacks 13 and the lower part of the first fuel cell stack 13 from the top.

  Further, the housing 20 has a thin tube 81 that discharges the remaining gas, water vapor, and the like from the power generation cell 11 to the outside at the center of the housing 20 connected through the heat insulating member 10 and the external can body 2. A very thick exhaust pipe 82 is connected to discharge and discharge the remaining gas, water vapor and the like as a whole.

Next, the operation of the solid oxide fuel cell in the above embodiment will be described.
First, the heating device 7 and the steam generator 40 are operated, and city gas is supplied to the fuel gas supply pipe 49 as fuel gas, and air is supplied to the air supply pipe 59.

  Then, the city gas is supplied through the fuel gas supply pipe 49 together with the steam supplied from the steam supply pipe 41 into the side fuel heat exchanger 43 that is directly and indirectly heated by the heating device 7. The temperature rises while raising the temperature, and is supplied to the upper fuel heat exchanger 6 through the connection pipe 44.

  At that time, the city gas is gradually supplied to the first chamber 65 from each corner of the can body 60, thereby being mixed with water vapor in the swirling flow path 65a to become a mixed gas, and gradually the can body. Since the fluid flows from the outer peripheral side of the 60 toward the inner peripheral side and further toward the flow path 65b, it is sufficiently heated.

  When the mixed gas flows to the central portion of the flow path 65b, the mixed gas gradually flows into the second chamber 66 from the communication port 61a, flows in the chamber 66, and is then discharged from the openings 66a to 66d by the internal pressure. Therefore, it flows equally into the blades 42a to 42d of the reformer 42 through the supply pipes 45a to 45d.

  As a result, the mixed gas has no change in the mixing ratio of the fuel gas and the water vapor, and is sufficiently heated, so that the hydrogen gas has a high conversion rate and a uniform conversion rate in each of the blade portions 42a to 42d of the reformer 42. After being reformed, the fuel buffer tanks 47 a to 47 d are supplied to the fuel cell stacks 13 via the manifolds 48.

  On the other hand, the air is supplied to the side air heat exchanger 53, rises while raising the temperature, and is supplied to the upper air heat exchanger 50 through the connection pipe 51. The temperature is raised while flowing in the upper air heat exchanger 50, and then supplied to each fuel cell stack 13 through the buffer tank 52.

  As a result, each fuel cell stack 13 is heated from the inside by the above-described hydrogen gas and air, and also heated by the heating device 7, and the temperature is raised to 400 ° C. to 500 ° C. It moves from the anode current collector 32 to the anode layer 22 through the fuel gas channel 12a to release electrons, and the oxygen gas passes from the cathode current collector 33 to the inside of the cathode layer 23 through the oxidant channel 12b. While moving toward the solid electrolyte layer 21, it becomes oxide ions and a power generation reaction occurs.

  According to the above-described upper fuel heat exchanger 6 for a solid oxide fuel cell, the partition plate 61 having the communication port 61a formed in the can body 60, and the bottom plate 60b protruding downward from the outer periphery of the partition plate 61 By providing the partition wall member 63 having the side plate 62 provided integrally, the first chamber 65 and the second chamber 66 are hermetically partitioned, so that discharge immediately after the inflow of fuel gas and water vapor is prevented. Thus, the fuel gas or the like can be swirled and mixed, and the fuel gas or the like can be sufficiently heated by heating with high-temperature heated air at the top of the housing during the swirling and mixing.

  In addition, since each connecting pipe 44 is connected to each corner of the side wall of the can body 60 in the swirling direction, the fuel gas and water vapor are efficiently mixed without disturbing the swirling flow of the fuel gas or the like. be able to. Further, since the openings 66a to 66d are formed at positions other than the position facing the communication port 61a in the bottom plate 60b, the fuel gas is temporarily stored in the second chamber 66 as a sufficiently heated mixed gas, and the openings 66a to 66d are caused by internal pressure. 66d can be supplied to the blade portions 42a to 42d of the reformer 42 through the supply pipes 45a to 45d.

  Therefore, the fuel gas can be uniformly reformed to hydrogen gas at a high conversion rate in each of the blade portions 42a to 42d. As a result, a desired amount of hydrogen gas is evenly supplied to each fuel cell stack 13. The power generation efficiency of all the fuel cell stacks 13 can be maximized.

  In addition, this invention is not limited to the above-mentioned embodiment at all, For example, the above-mentioned communicating port 61a may be formed in multiple numbers in the center part of the partition plate 61. FIG.

It is a longitudinal cross-sectional schematic diagram which shows the solid oxide fuel cell which comprises the upper fuel heat exchanger which concerns on this invention. It is the II-II line arrow figure of FIG. It is a partially broken schematic plan view of the upper fuel heat exchanger. It is a partially broken side view of the upper fuel heat exchanger. FIG. 3 is an explanatory diagram of a main part of a fuel cell stack 13. It is a longitudinal cross-sectional schematic diagram which shows a common solid oxide fuel cell.

Explanation of symbols

4 Fuel gas supply means 6 Upper fuel heat exchanger 10 Heat insulation member (heat insulation material)
DESCRIPTION OF SYMBOLS 13 Fuel cell stack 20 Housing 60 Can body 61 Partition member 61a Communication port 65 1st chamber 66 2nd chamber

Claims (3)

A plurality of fuel cell stacks in which power generation cells and separators are alternately stacked in a housing whose outer periphery is covered with a heat insulating material, and the fuel gas in these fuel cell stacks is reformed to hydrogen by an endothermic reaction with water vapor. A fuel gas supply means provided with a reformer to be supplied , and the fuel gas supply means, disposed above the fuel cell stack, and flowing the fuel gas and water vapor therein, An upper fuel heat exchanger having a flat can body that absorbs heat in the housing and heats the fuel gas and water vapor;
In the upper fuel heat exchanger, the fuel gas and the water vapor formed in the outer peripheral portion of the can body and supplied from the fuel gas supply means through the supply port formed on the wall surface of the can body in the circumferential direction. the Rukoto pivoted a first chamber to a gas mixture which the fuel gas and the steam are mixed efficiently formed in a central portion of the can body, the reforming of the fuel gas supply means to the gas mixture Rutotomoni a second chamber for supplying the quality unit is partitioned by a partition member, in the partition member, the communication port for flowing the mixed gas of said first chamber to said second chamber is formed The fuel cell characterized by the above-mentioned. The upper fuel heat exchanger is formed such that the can body is formed in a rectangular shape in plan view, and the supply port supplies the fuel gas and the water vapor to the corners in the turning direction,
The partition member is formed in a cylindrical shape, the lower part is integrally formed with the bottom of the can body, the communication port is formed in the ceiling, and the second chamber is An opening for discharging the mixed gas is formed between the partition wall member and the bottom of the can body and at a position other than the position facing the communication port in the bottom of the can body. 2. The fuel cell according to 1. The fuel gas supply means is connected to a reformer that reforms the fuel gas into hydrogen and distributes and distributes the fuel gas to the plurality of fuel cell stacks downstream of the upper fuel heat exchanger, and the reformer Are formed with a plurality of outlets for distributing and supplying, and a supply port communicating with each of the outlets is formed, and a plurality of openings of the upper fuel heat exchanger are provided corresponding to the respective outlets. The fuel cell according to claim 2, wherein the fuel cell is formed.

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