JP2004047175A - Fuel cell stack and its operating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evenly quickly raise a temperature of a whole of a fuel cell stack to an operating temperature. <P>SOLUTION: The fuel cell stack 40 has a first unit cell 5a and a second unit cell 5b. Prior to steady operation, mixed gas of gaseous hydrogen and air is supplied to each cathode side electrode 3a of the first and second unit cells 5a and 5b. In a first oxygen-containing gas passage 52a of a first cathode side electrode side separator 48a composing the first unit cell 5a, the mixed gas flows toward a second oxygen-containing gas outlet passage 19b provided in a left end side from a second oxygen-containing inlet passage 18b provided in a right end side of the first cathode side electrode side separator 48a. In a second oxygen-containing gas passage 52b of a second cathode side electrode side separator 48b composing the second unit cell 5b, the mixed gas flows toward a first oxygen-containing gas outlet passage 19a provided in a right end side from a first oxygen-containing gas inlet passage 18a provided in a left end side of the second cathode side electrode side separator 48b. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell stack and a method of operating the fuel cell stack, and more particularly, to a fuel cell stack and a method of operating the fuel cell stack that can be heated to a steady operating temperature substantially uniformly and quickly with a simple configuration.
[0002]
[Prior art]
FIG. 7 shows a schematic overall perspective view of a general fuel cell stack 1. The fuel cell stack 1 includes a predetermined number of unit cells 5 each having a joined body 4 formed by interposing an electrolyte layer (not shown) between an anode 2 and a cathode 3 in an arrow A direction. It has a stacked body 6 that is stacked and configured by being electrically connected to each other in series.
[0003]
The joined body 4 is housed and held in the opening of the frame-shaped seal member 7. Further, the anode-side electrode 2 and the cathode-side electrode 3 constituting the joined body 4 are accommodated in openings of the gaskets 8 and 9, respectively.
[0004]
The unit cell 5 has the joined body 4 and the anode-side electrode-side separator 10 and the cathode-side electrode-side separator 11 that sandwich the joined body 4. Among them, a fuel gas flow path 12 for supplying / discharging a hydrogen-containing gas to / from the anode-side electrode 2 is provided on a contact surface of the anode-side electrode-side separator 10 with the anode-side electrode 2. Similarly, an oxygen-containing gas flow path 13 for supplying and discharging an oxygen-containing gas to and from the cathode-side electrode 3 is provided on a surface of the cathode-side electrode-side separator 11 that is in contact with the cathode-side electrode 3. The fuel gas flow path 12 and the oxygen-containing gas flow path 13 are formed so as to meander two and a half times inside the separators 10 and 11 from being introduced into each of the separators 10 and being discharged.
[0005]
In the laminate 6, a cooling plate 14 is interposed between the unit cells 5. Each cooling plate 14 has a cooling water channel 15 provided on a contact surface with the cathode-side electrode-side separator 11.
[0006]
Further, a fuel gas inlet passage 16 for supplying a fuel gas is provided at the lower left end of the fuel cell stack 1 in FIG. 7, and an unreacted fuel gas is discharged at a diagonal position thereof. The fuel gas outlet passage 17 is provided. Similarly, an oxygen-containing gas inlet passage 18 for supplying an oxygen-containing gas is provided at the lower right end, and an oxygen-containing gas outlet for discharging unreacted oxygen-containing gas is provided at a diagonal position. A passage 19 is provided. Of course, the fuel gas inlet passage 16 and the fuel gas outlet passage 17 are in communication with the fuel gas passage 12, and the oxygen-containing gas inlet passage 18 and the oxygen-containing gas outlet passage 19 are in communication with the oxygen-containing gas passage 13. .
[0007]
A cooling water inlet passage 20 is formed between the fuel gas inlet passage 16 and the oxygen-containing gas outlet passage 19, and a cooling water passage is provided between the oxygen-containing gas inlet passage 18 and the fuel gas outlet passage 17. An outlet passage 21 is formed. The cooling water inlet passage 20 and the cooling water outlet passage 21 communicate with the cooling water passage 15.
[0008]
As shown in FIG. 7, the current collecting electrodes 22 and 23 are electrically connected to the unit cells located at both ends of the unit cell 5 configured as described above. Further, end plates 24 and 25 are arranged outside the current collecting electrodes 22 and 23 via an insulating sheet (not shown) for preventing leakage.
[0009]
One end plate 24 has a fuel gas inlet 26 and a fuel gas outlet 27 communicating with the fuel gas inlet passage 16 and the fuel gas outlet passage 17, respectively, and an oxygen-containing gas inlet passage 18 and an oxygen-containing gas outlet passage 19, respectively. An oxygen-containing gas inlet 28 and an oxygen-containing gas outlet 29 communicating with each other, and a cooling water inlet 30 and a cooling water outlet 31 communicating with the cooling water inlet passage 20 and the cooling water outlet passage 21 are provided, respectively.
[0010]
[Problems to be solved by the invention]
When the electrolyte is, for example, a porous silicon carbide body impregnated with phosphoric acid, the fuel cell stack 1 configured as described above is operated in a steady state after the temperature is raised to 140 ° C. to 190 ° C. That is, first, the temperature of the fuel cell stack 1 is raised to a level exceeding 100 ° C. by a heating means such as a heater (not shown). Thereafter, a fuel gas and an oxidant-containing gas are supplied to the anode 2 and the cathode 3, respectively, to cause an ionization reaction of hydrogen at the anode 2, and oxygen, hydrogen ions, and electrons at the cathode 3. A binding reaction is caused to occur, and the fuel cell stack 1 is heated to 140 ° C. to 190 ° C. by utilizing the reaction heat at this time.
[0011]
However, when the temperature is increased as described above, there is a problem that it takes a long time to reach the operating temperature. That is, since it takes a long time until stable steady operation becomes possible, there is a problem in actual use that the fuel cell stack 1 cannot immediately generate power when it is desired to generate power.
[0012]
As a measure to solve this, it is recalled to use a heater that generates a large amount of heat. However, such a heater is generally large in size, and therefore, causes an increase in the size of the entire fuel cell system, resulting in a problem that energy efficiency per volume and weight is significantly reduced.
[0013]
Therefore, as disclosed in JP-A-63-225577 and U.S. Pat. No. 6,103,410, a fuel gas and an oxygen-containing gas are simultaneously supplied to the cathode 3 and the following reaction formula (A) is obtained. It is also conceivable to employ a method of causing the reaction shown and causing the reaction heat at this time to raise the temperature of the fuel cell stack 1.
[0014]
2H ₂ + O ₂ → 2H ₂ O ... (A)
However, when the fuel gas and the oxygen-containing gas are simultaneously supplied to the cathode 3, the reaction represented by the reaction formula (A) occurs in the vicinity of the inlet of the oxygen-containing gas channel 13 where both gases come into contact with the cathode 3. Actively progresses from. In other words, both gases start to be consumed as soon as they come into contact with the cathode electrode 3. Therefore, in the vicinity of the outlet of the oxygen-containing gas flow path 13, the amount of gas involved in the reaction represented by the reaction formula (A) decreases, and the amount of generated heat decreases. As a result, the temperature of the cathode-side electrode 3 and, consequently, the temperature of the fuel cell stack 1 increases on the inlet side (near the left end side in FIG. 7) of the oxygen-containing gas flow path 13 and on the outlet side of the oxygen-containing gas flow path 13 ( 7 (near the right end side in FIG. 7). For this reason, a temperature distribution occurs in the fuel cell stack 1, and a problem is caused that it takes time to raise the temperature near the right end side where the temperature increase rate is low to the operating temperature.
[0015]
As a result, when the fuel gas and the oxygen-containing gas are simultaneously supplied to the cathode 3 in the fuel cell stack 1 according to the related art, the temperature distribution becomes non-uniform, and it takes a long time to raise the temperature to the operating temperature. There is a problem that it takes.
[0016]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and provides a fuel cell stack and a method of operating the fuel cell stack, which can be uniformly and quickly raised over the whole, and do not increase the size of equipment. The purpose is to provide.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, a fuel cell stack according to the present invention is provided with a joined body formed by sandwiching an electrolyte between an anode and a cathode, and disposed on the anode side of the joined body. A first unit cell including an anode-side electrode-side separator, and a first cathode-side electrode-side separator provided on the cathode-side electrode side of the joined body;
A joined body comprising an electrolyte sandwiched between an anode electrode and a cathode electrode, an anode-side electrode separator provided on the anode-side electrode side of the joined body, and a cathode-side electrode provided on the joined body A second unit cell having a second cathode-side electrode-side separator,
A laminate having the first unit cell and the second unit cell;
With
The first cathode-side electrode-side separator and the second cathode-side electrode-side separator are provided with a first oxygen-containing gas flow path and a second oxygen-containing gas flow path through which an oxygen-containing gas flows, respectively.
The first oxygen-containing gas flow path has a location where a gas flows in a direction opposite to a gas flow direction in the second oxygen-containing gas flow path.
[0018]
With this configuration, when the fuel gas and the oxygen-containing gas are simultaneously supplied to the cathode side electrode prior to the steady operation, for example, the first unit cell starts at the right end and the second unit cell starts at the left end. For example, the temperature rise start point in the first unit cell may be different from the temperature rise start point in the second unit cell. In the case of this example, since the temperature rises from both ends of the fuel cell stack, it is possible to suppress the occurrence of temperature distribution in the fuel cell stack. That is, the temperature can be increased substantially uniformly and quickly.
[0019]
Moreover, in this case, the temperature of the fuel cell stack can be raised without particularly requiring additional equipment such as a large heater or the like, and the entire system can have a simple configuration.
[0020]
In the laminate, it is preferable that the first unit cells and the second unit cells are alternately stacked adjacent to each other. Thereby, heat transfer can be efficiently performed, and the temperature distribution of the fuel cell stack becomes more uniform.
[0021]
To raise the temperature of the first unit cell and the second unit cell from different ends as described above, for example, a gas inlet communicating with the first oxygen-containing gas flow path of the first cathode-side electrode-side separator and A gas outlet and a gas outlet are provided near each of the first end and the second end of the first cathode-side electrode separator, and communicate with the second oxygen-containing gas flow path of the second cathode-side electrode separator. An inlet is provided near each of the first end and the second end of the second cathode-side electrode-side separator, and the first cathode-side separator and the second cathode-side electrode-side separator in the laminate are connected to each other. The end portions and the second end portion may be overlapped via the anode-side electrode-side separator and the joined body.
[0022]
Further, in the method for operating the fuel cell stack according to the present invention, the fuel gas and the oxygen-containing gas are supplied to the cathode electrode prior to power generation, and the hydrogen in the fuel gas and the oxygen-containing gas in the oxygen-containing gas are supplied to the cathode electrode. A method of operating a fuel cell stack, wherein the temperature of the assembly is raised to an operating temperature by reaction heat generated by reacting with oxygen,
A joined body comprising an electrolyte sandwiched between an anode electrode and a cathode electrode, an anode-side electrode separator provided on the anode-side electrode side of the joined body, and a cathode-side electrode provided on the joined body A first unit cell having a first cathode-side electrode-side separator,
A joined body comprising an electrolyte sandwiched between an anode electrode and a cathode electrode, an anode-side electrode separator provided on the anode-side electrode side of the joined body, and a cathode-side electrode provided on the joined body A second unit cell having a second cathode-side electrode-side separator,
Forming a laminate having the first unit cell and the second unit cell,
The first cathode-side electrode-side separator and the second cathode-side electrode-side separator are provided with a first oxygen-containing gas flow path and a second oxygen-containing gas flow path for flowing an oxygen-containing gas, respectively.
When the fuel gas and the oxygen-containing gas are simultaneously supplied to the first oxygen-containing gas flow path and the second oxygen-containing gas flow path, the fuel flows through the first oxygen-containing gas flow path and the second oxygen-containing gas flow path. By making the flow directions of the gas and the oxygen-containing gas different from each other, the temperature rise start point of the first unit cell and the temperature rise start point of the second unit cell are made different.
[0023]
According to the present invention, when the fuel gas and the air are simultaneously supplied to the cathode electrode and the stack is heated by the heat generated by the reaction of the two gases, the temperature rise start point of the first unit cell Since the temperature rise starting point of the second unit cell is different from that of the second unit cell, it is possible to suppress the occurrence of temperature distribution in the stacked body, and it is possible to raise the temperature of the fuel cell stack to a steady operating temperature substantially uniformly and quickly. .
[0024]
Further, it is preferable that a fuel cell and an oxygen-containing gas be supplied to the cathode side electrode after forming a stacked body with the first unit cell and the second unit cell adjacent to each other. This is because heat is efficiently transmitted, so that the occurrence of temperature distribution in the laminate can be further suppressed.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a fuel cell stack and a method of operating the same according to the present invention will be described in detail with reference to the accompanying drawings. The same components as those shown in FIG. 7 are denoted by the same reference numerals, and detailed description thereof may be omitted in some cases.
[0026]
FIG. 1 shows a schematic overall perspective view of the fuel cell stack according to the present embodiment. The fuel cell stack 40 is configured by alternately stacking a predetermined number of first unit cells 5a and second unit cells 5b shown in FIG. 2 in the direction of arrow A, and electrically connecting them in series. It has a laminate 42.
[0027]
The first unit cell 5a has the same configuration as the unit cell 5 in the fuel cell stack 1 according to the related art described above. That is, in the first unit cell 5a, as shown in FIG. 3, which is an enlarged cross-sectional view of a main part of the stack 42 constituting the fuel cell stack 40, the electrolyte layer 44a is formed by the anode electrode 2a and the cathode electrode 3a. The bonded body 4a is provided by being interposed therebetween. As the electrolyte layer 44a, a material in which a concentrated base material (matrix) made of porous silicon carbide is impregnated with concentrated phosphoric acid can be exemplified. However, the present invention is not particularly limited thereto, and a base such as polybenzimidazole can be used. The acidic polymer may be impregnated with concentrated phosphoric acid, or polytetrafluoroethylene sulfonic acid may be impregnated with water.
[0028]
On the other hand, the anode-side electrode 2a and the cathode-side electrode 3a are made of a gas diffusion layer (not shown) made of carbon cloth or the like, and porous carbon particles having a platinum alloy supported on the surface are uniformly formed on the surface of the gas diffusion layer. And an electrode catalyst layer (not shown) laminated on the electrode layer, and are joined to the electrolyte layer 44a such that the electrode catalyst layers face each other via the electrolyte layer 44a.
[0029]
In the joined body 4a, the electrolyte layer 44a is accommodated and held in the opening of the frame-shaped seal member 7. The anode 2a and the cathode 3a are accommodated in openings of the gaskets 8 and 9, respectively.
[0030]
Outside the anode 2a and the cathode 3a, an anode-side separator 46a and a first cathode-side separator 48a made of porous carbon or metal are arranged, respectively.
[0031]
A straight fuel gas flow path 50 or a first oxygen-containing gas flow path is provided on a contact surface of the anode-side electrode-side separator 46a or the first cathode-side electrode-side separator 48a with the anode-side electrode 2a or the cathode-side electrode 3a. 52a are provided respectively.
[0032]
In the second unit cell 5b adjacent to the first unit cell 5a configured as described above, the electrolyte layer 44b configured as described above is interposed between the anode-side electrode 2b and the cathode-side electrode 3b. Is provided. The electrolyte layer 44b, the anode electrode 2b, and the cathode electrode 3b are the same as the electrolyte layer 44a, the anode electrode 2a, and the cathode electrode 3a in the first unit cell 5a. The elements constituting the unit cell 5b are denoted by b instead of a.
[0033]
Also in the second unit cell 5b, the electrolyte layer 44b, the anode electrode 2b, and the cathode electrode 3b are accommodated and held in openings of the frame-shaped seal member 7, the gaskets 8, 9, respectively.
[0034]
An anode-side electrode-side separator 46b and a second cathode-side electrode-side separator 48b made of porous carbon or metal are disposed outside the anode-side electrode 2b and the cathode-side electrode 3b, respectively.
[0035]
Here, as will be understood from FIGS. 2 and 3, the anode-side electrode-side separator 46b of the second unit cell 5b also serves as the first cathode-side electrode-side separator 48a of the first unit cell 5a. That is, in the separator 48a (46b), the first oxygen-containing gas channel 52a is provided on the contact surface of the first unit cell 5a with the cathode electrode 3a, and the anode side of the second unit cell 5b is provided. A fuel gas flow path 50 is provided on the contact surface with the electrode 2b.
[0036]
As shown in FIG. 2, a cooling water inlet passage 20, a fuel gas inlet passage 16, a first oxygen-containing gas inlet passage 18a, and a second oxygen-containing gas outlet passage 19b are provided at the left end of the stacked body 42. I have. On the other hand, a first oxygen-containing gas outlet passage 19a, a second oxygen-containing gas inlet passage 18b, a cooling water outlet passage 21, and a fuel gas outlet passage 17 are provided at the right end of the laminate 42. That is, in the laminated body 42, there are two oxygen-containing gas inlet / outlet passages for flowing the oxygen-containing gas.
[0037]
As can be understood from FIGS. 2 and 4, the first oxygen-containing gas inlet passage 18a and the first oxygen-containing gas outlet passage 19a are provided in the second cathode-side electrode-side separator 48b of the second unit cell 5b. It communicates only with the oxygen-containing gas channel 52b. That is, as described later, the oxygen-containing gas introduced through the first oxygen-containing gas inlet passage 18a flows only through the second oxygen-containing gas flow path 52b of the second cathode-side electrode-side separator 48b, and the first oxygen-containing gas flows through the first oxygen-containing gas flow path 52b. The gas is discharged from the oxygen-containing gas outlet passage 19a.
[0038]
As is similarly understood from FIGS. 2 and 5, the second oxygen-containing gas inlet passage 18b and the second oxygen-containing gas outlet passage 19b are provided in the first cathode-side electrode-side separator 48a constituting the first unit cell 5a. It communicates only with the first oxygen-containing gas channel 52a. Therefore, the oxygen-containing gas introduced through the second oxygen-containing gas inlet passage 18b flows only through the first oxygen-containing gas flow passage 52a of the first cathode-side electrode-side separator 48a, and the second oxygen-containing gas outlet passage. It is discharged from 19b.
[0039]
The cooling plate 54 is in contact with the smooth surface of the second cathode-side electrode-side separator 48b (see FIGS. 2 and 3). The cooling plate 54 is provided with a cooling water passage 56, and the cooling water passage 56 communicates with the cooling water inlet passage 20 and the cooling water outlet passage 21 (see FIG. 2). Note that a seal member 58 is interposed between the second cathode-side electrode-side separator 48b and the cooling plate 54.
[0040]
The stacked body 42 is configured by repeatedly stacking the above-described first unit cell 5a, second unit cell 5b, and cooling plate 54 in this order. Then, the current collecting electrodes 22 and 23 are electrically connected to both ends of the laminated body 42, respectively, and outside the current collecting electrodes 22 and 23 via an insulating sheet (not shown) for preventing leakage. End plates 60 and 25 are arranged.
[0041]
At the left end of one end plate 60, a cooling water inlet 30, a fuel gas inlet 26, a first oxygen-containing gas inlet 28a, and a second oxygen-containing gas outlet 29b are provided in this order from below. . On the other hand, at the right end, a first oxygen-containing gas outlet 29a, a second oxygen-containing gas inlet 28b, a cooling water outlet 31, and a fuel gas outlet 27 are provided in this order from below. Of course, the cooling water inlet 30, the fuel gas inlet 26, the first oxygen-containing gas inlet 28a, the second oxygen-containing gas outlet 29b, the first oxygen-containing gas outlet 29a, the second oxygen-containing gas inlet 28b, The cooling water outlet 31 and the fuel gas outlet 27 are provided with a cooling water inlet passage 20, a fuel gas inlet passage 16, a first oxygen-containing gas inlet passage 18a, a second oxygen-containing gas outlet passage 19b, and a first oxygen-containing gas outlet passage. 19a, the second oxygen-containing gas inlet passage 18b, the cooling water outlet passage 21, and the fuel gas outlet passage 17 respectively.
[0042]
In the fuel cell stack 40, a tie rod (not shown) passed through a through hole 62 extending from one end plate 60 to the other end plate 25 through the stacked body 42 and the upper end face and the lower end face of the stacked body 42. The end plates 60 and 25, the laminate 42, and the like are fastened and held in the direction of arrow A by another tie rod (not shown) inserted into the recess 64.
[0043]
FIG. 6 shows a schematic configuration diagram of a fuel cell system 70 in which the fuel cell stack 40 having the above configuration is incorporated. As shown in FIG. 6, a hydrogen gas supply path 72 and a hydrogen gas discharge path 74 for supplying and discharging hydrogen gas as a fuel gas, and air as an oxygen-containing gas are supplied to the fuel cell stack 40. The air supply path 76 for discharge and the main air discharge path 78 and the branch air discharge path 80 are connected. Further, a load such as a motor (not shown) is connected to the current collecting electrodes 22 and 23 constituting the fuel cell stack 40.
[0044]
The hydrogen gas supply path 72 includes a high-pressure hydrogen storage source 82 for supplying hydrogen gas at a high pressure, an electromagnetic valve 84a, a pressure reducing valve 86a, a hydrogen gas flow controller 88a, a shutoff valve 90a, and a check valve. The 92a and the three-way valve 94a are arranged in this order from the upstream side. One air supply path 76 has a compressor 95 for supplying air, a gas mixer 96 and a flashback preventer 98a are interposed, and the supply path 76 has a first supply path 76a and a second supply path 76a. 2 is configured similarly to the hydrogen gas supply path 72 except that it is branched to the supply path 76b. Therefore, the same components are denoted by the same reference numerals, and b is substituted for a. In addition, the detailed description is omitted.
[0045]
Note that a shutoff valve 102 and a check valve 104 are installed in the air supply pipe 100 that bridges the three-way valve 94a and the three-way valve 94b. A check valve 98b is interposed between the check valve 104 and the three-way valve 94b.
[0046]
The fuel cell system 70 thus configured is operated as follows.
[0047]
First, the three-way valves 94a and 94b are operated so that hydrogen gas and air are introduced only into the cathode-side electrodes 3a and 3b, and in this state, supply of a predetermined flow rate of hydrogen gas and air is started. At this time, excess air is supplied to keep the proportion of hydrogen gas out of the explosion range for safety.
[0048]
The supplied hydrogen gas and air are mixed by a gas mixer 96 to become a mixed gas, and are branched into a first supply path 76a and a second supply path 76b substantially equally.
[0049]
The mixed gas in the first supply path 76a passes through the first oxygen-containing gas inlet 28a (see FIG. 1) of the fuel cell stack 40, and then flows through the first oxygen-containing gas inlet passage 18a (see FIG. 2). It reaches the second oxygen-containing gas channel 52b in the second cathode-side electrode-side separator 48b of the two unit cell 5b. Then, the hydrogen gas and the air in the mixed gas in contact with the electrode catalyst layer in the cathode-side electrode 3b of the second unit cell 5b cause the reaction represented by the reaction formula (A). Due to the heat generated thereby, the temperature of the cathode-side electrode 3b and thus the temperature of the second unit cell 5b rises from the first oxygen-containing gas inlet passage 18a side (the left end side in FIGS. 1 and 2). On the other hand, in the vicinity of the outlet of the first oxygen-containing gas flow channel 52a (on the right end side), the amount of gas involved in the reaction represented by the reaction formula (A) decreases, and the amount of generated heat decreases. That is, the rate of temperature rise is small on the right end side of the second unit cell 5b.
[0050]
On the other hand, the mixed gas in the second supply path 76b passes through the second oxygen-containing gas inlet 28b (see FIG. 1) and the second oxygen-containing gas inlet passage 18b (see FIG. 2), and then flows into the first unit cell. It reaches the first oxygen-containing gas flow path 52a of the first cathode-side electrode-side separator 48a constituting 5a. Then, the hydrogen gas and the air in the mixed gas in contact with the electrode catalyst layer in the cathode electrode 3a of the first unit cell 5a also react as shown in the reaction formula (A). As a result, the temperature of the cathode-side electrode 3a and thus the temperature of the first unit cell 5a rises from the second oxygen-containing gas inlet passage 18b side (the right end side in FIGS. 1 and 2). On the other hand, in the vicinity of the outlet of the second oxygen-containing gas flow path 52b (on the left end side), the rate of temperature rise is also small because the generated heat is small.
[0051]
That is, in the present embodiment, in the first unit cell 5a, the temperature rise starts from the right end side, and the temperature decreases toward the left end side which is the flow direction of the mixed gas. In the second unit cell 5b, the temperature starts rising from the left end side, and decreases toward the right end side, which is the flow direction of the mixed gas.
[0052]
The right end, which is the high temperature part of the first unit cell 5a, and the left end, which is the low temperature part of the second unit cell 5b, are stacked, and the left end, which is the low temperature part of the first unit cell 5a, and the second unit The right end side, which is the high temperature part of the cell 5b, is stacked. For this reason, as for the laminated body 42, the respective heating rates at both ends are substantially equal. In other words, the temperature rising start position of the first unit cell 5a and the temperature rising start position of the second unit cell 5b are different from each other, and the temperature rising start positions are not overlapped with each other, so that the stacked body 42 Can be raised substantially uniformly and quickly over the whole.
[0053]
Moreover, in this case, since the first unit cells 5a and the second unit cells 5b are alternately stacked so as to be adjacent to each other, heat is efficiently transmitted. Therefore, it is possible to further suppress the occurrence of the temperature distribution in the stacked body 42.
[0054]
Further, since the temperature of the stacked body 42 is raised by using the heat of reaction between the hydrogen gas and the air, a large-sized heater or the like is not particularly required. Therefore, the temperature of the fuel cell system 70 can be raised to the operating temperature with a simple and economical configuration.
[0055]
Note that H generated at the cathode-side electrode 3a of the first unit cell 5a. ₂ After passing through the branch air discharge path 80, O is generated at the cathode electrode 3b of the second unit cell 5b in the main air discharge path 78. ₂ Merges with O and is discharged out of the system.
[0056]
After the joined bodies 4a and 4b are heated to a predetermined temperature (about 140 to about 190 ° C. in the case of a phosphoric acid fuel cell) as described above, the three-way valves 94a and 94b are operated and the shut-off valve 102 is turned on. It is set so that the supply of hydrogen gas to both the cathode-side electrodes 3a and 3b is stopped and the hydrogen gas is supplied to the fuel gas flow path 50 of the anode-side electrode-side separators 46a and 46b. On the other hand, the supply of air to the first oxygen-containing gas channel 52a and the second oxygen-containing gas channel 52b is continued.
[0057]
Accordingly, electrons are generated at the anode-side electrodes 2a and 2b by a reaction represented by the following reaction formula (B).
[0058]
2H ₂ → 4H ⁺ + 4e ... (B)
The electrons (e) function as electric energy for energizing loads such as motors electrically connected to the current collecting electrodes 22 and 23, and then reach the cathode-side electrodes 3a and 3b, and have the following reaction formula: It participates in the reaction shown in (C).
[0059]
O ₂ + 4H ⁺ + 4e → 2H ₂ O… (C)
Following the generation of power by the fuel cell system 70, the load is energized.
[0060]
During the steady operation, the fuel cell stack 40 is cooled by the cooling water flowing through the cooling water passage 56 of the cooling plate 54.
[0061]
In the above-described embodiment, hydrogen gas is used as the fuel gas. However, the present invention is not limited to this, and any gas containing hydrogen may be used. Similarly, although air is used as the oxygen-containing gas, any gas containing oxygen may be used, and oxygen itself may be used.
[0062]
Further, in this embodiment, the cooling plate 54 is inserted into the laminated body 42, but the laminated body may be configured without inserting the cooling plate 54. In this case, an oxygen-containing gas flow path is provided on a surface of the anode-side electrode-side separator 46a constituting the first unit cell 5a on a surface opposite to the surface provided with the fuel gas flow passage 50, and the second unit cell 5b is formed. The fuel gas channel may be provided on the surface of the second cathode-side electrode-side separator 48b opposite to the surface on which the second oxygen-containing gas channel 52b is provided. That is, the anode-side electrode-side separator 46a forming the first unit cell 5a and the second cathode-side electrode-side separator 48b forming the second unit cell 5b are combined with the anode-side electrode-side separator 46b forming the second unit cell 5b. A similar configuration may be used.
[0063]
Further, the flow paths of the first oxygen-containing gas flow path 52a in the first cathode-side electrode-side separator 48a and the second oxygen-containing gas flow path 52b in the second cathode-side electrode-side separator 48b are both linear. The stack 1 may meander like the oxygen-containing gas channel 13 of the cathode-side electrode-side separator 11. Also in this case, since the first oxygen-containing gas flow path 52a and the second oxygen-containing gas flow path 52b have portions where the flow direction of the mixed gas is opposite, the occurrence of a temperature distribution in the stacked body is suppressed. can do.
[0064]
【The invention's effect】
As described above, according to the present invention, the gas is made to flow such that there are locations in the oxygen-containing gas flow path in the first unit cell and the second unit cell that are opposite to each other. For this reason, when the fuel gas and the air are simultaneously supplied to the cathode side electrode and the stack is heated by the heat generated by the reaction of the two gases, the temperature rise start point of the first unit cell and the second Since the temperature rise starting point of the unit cell is different, it is possible to suppress the occurrence of temperature distribution in the stacked body. For this reason, the effect that the temperature of the fuel cell stack can be substantially uniformly and quickly raised to the steady operation temperature is achieved.
[Brief description of the drawings]
FIG. 1 is a schematic overall perspective view of a fuel cell stack according to the present embodiment.
FIG. 2 is a schematic perspective view of a stack constituting the fuel cell stack of FIG.
FIG. 3 is an enlarged sectional view of a main part of a stack constituting the fuel cell stack of FIG. 1;
FIG. 4 is a schematic overall front view of a second cathode-side electrode-side separator.
FIG. 5 is a schematic overall front view of a first cathode-side electrode-side separator.
6 is a schematic configuration diagram of a fuel cell system in which the fuel cell stack shown in FIG. 1 is incorporated.
FIG. 7 is a schematic overall perspective view of a fuel cell stack according to the related art.
[Explanation of symbols]
1, 40: fuel cell stack 2, 2a, 2b: anode side electrode
3, 3a, 3b ... cathode side electrode 4, 4a, 4b ... joined body
5, 5a, 5b ... unit cell 6, 42 ... laminate
10, 46a, 46b ... anode side electrode side separator
11, 48a, 48b ... cathode side electrode side separator
12, 50 ... fuel gas flow path 13, 52a, 52b ... oxygen-containing gas flow path
14, 54: cooling plate 15, 56: cooling water passage
16: fuel gas inlet passage 17: fuel gas outlet passage
18, 18a, 18b ... oxygen-containing gas inlet passage
19, 19a, 19b ... oxygen-containing gas outlet passage
20: cooling water inlet passage 21: cooling water outlet passage
26: Fuel gas inlet 27 ... Fuel gas outlet
28, 28a, 28b ... oxygen-containing gas inlet
29, 29a, 29b ... oxygen-containing gas outlet
44a, 44b: electrolyte layer 70: fuel cell system
72: hydrogen gas supply path 74: hydrogen gas discharge path
76, 76a, 76b ... air supply path
78: Main air discharge path 80: Branch air discharge path
82: High pressure hydrogen storage source 95: Compressor
100 ... air pipe

Claims (5)

A joined body comprising an electrolyte sandwiched between an anode electrode and a cathode electrode, an anode-side electrode separator provided on the anode-side electrode side of the joined body, and a cathode-side electrode provided on the joined body A first unit cell having a first cathode-side electrode-side separator,
A joined body comprising an electrolyte sandwiched between an anode electrode and a cathode electrode, an anode-side electrode separator provided on the anode-side electrode side of the joined body, and a cathode-side electrode provided on the joined body A second unit cell having a second cathode-side electrode-side separator,
A laminate having the first unit cell and the second unit cell;
With
The first cathode-side electrode-side separator and the second cathode-side electrode-side separator are provided with a first oxygen-containing gas flow path and a second oxygen-containing gas flow path through which an oxygen-containing gas flows, respectively.
The fuel cell stack according to claim 1, wherein the first oxygen-containing gas flow path has a location where a gas flows in a direction opposite to a gas flow direction in the second oxygen-containing gas flow path. The fuel cell stack according to claim 1, wherein the first unit cells and the second unit cells are alternately stacked adjacent to each other in the stack. 3. The fuel cell stack according to claim 1, wherein a gas inlet and a gas outlet communicating with a first oxygen-containing gas flow path of the first cathode-side electrode-side separator are a first end of the first cathode-side electrode-side separator. 4. And a gas outlet and a gas inlet provided near each of the second end portions and communicating with the second oxygen-containing gas flow path of the second cathode side electrode side separator. A portion and a second end are provided in the vicinity of each of the
In the laminate, the first end portions and the second end portions of the first cathode side electrode side separator and the second cathode side electrode side separator are connected to the anode side electrode side separator and the joined body. A fuel cell stack, wherein the fuel cell stacks overlap each other. Prior to power generation, a fuel gas and an oxygen-containing gas are supplied to a cathode-side electrode, and the bonding by the reaction heat generated by reacting hydrogen in the fuel gas with oxygen in the oxygen-containing gas at the cathode-side electrode. A method of operating a fuel cell stack that heats a body to an operating temperature,
A joined body comprising an electrolyte sandwiched between an anode electrode and a cathode electrode, an anode-side electrode separator provided on the anode-side electrode side of the joined body, and a cathode-side electrode provided on the joined body A first unit cell having a first cathode-side electrode-side separator,
A joined body comprising an electrolyte sandwiched between an anode electrode and a cathode electrode, an anode-side electrode separator provided on the anode-side electrode side of the joined body, and a cathode-side electrode provided on the joined body A second unit cell having a second cathode-side electrode-side separator,
Forming a laminate having the first unit cell and the second unit cell,
The first cathode-side electrode-side separator and the second cathode-side electrode-side separator are provided with a first oxygen-containing gas flow path and a second oxygen-containing gas flow path for flowing an oxygen-containing gas, respectively.
When the fuel gas and the oxygen-containing gas are simultaneously supplied to the first oxygen-containing gas flow path and the second oxygen-containing gas flow path, the fuel flows through the first oxygen-containing gas flow path and the second oxygen-containing gas flow path. An operation of a fuel cell stack, characterized in that the flow directions of a gas and an oxygen-containing gas are made different from each other, so that a temperature rise start point of the first unit cell and a temperature rise start point of the second unit cell are made different. Method. 5. The operating method according to claim 4, wherein the first unit cell and the second unit cell are arranged adjacent to each other to form the stacked body, and then the fuel gas and the oxygen-containing gas are supplied to the cathode side electrode. To operate the fuel cell stack.

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