JPH07230817A - Solid polymer electrolyte fuel cell - Google Patents

Abstract

(57) [Abstract] [Purpose] Even if the number of cell stages is increased to increase the output, the generated water in the cells is efficiently discharged to eliminate cells in which the voltage drops, and conditions such as shaking, acceleration, and vibration are eliminated. Enables optimal control even in severe cases. [Structure] A cell C in which an electrolyte membrane 1 is sandwiched between an oxygen electrode 2 and a fuel electrode 3 is partitioned by an oxygen electrode side separator 4a and a fuel electrode side separator 4b to be laminated in multiple stages. Gas passages 5a and 5b are formed in the oxygen electrode 2 and the fuel electrode 3 so that the oxidant gas can supply and discharge the gas passage 5a and the fuel gas can discharge and supply the gas passage 5b, respectively. The separators 4a and 4b are provided with supply and discharge flow passage holes 21, 22 and 23, 24 for the oxidant gas and the fuel gas from the outside separately in the gas passages 5a and 5b,
The generated water can be discharged through the oxidant gas discharge passage hole by the action of the ejector 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid polymer electrolyte fuel cell among fuel cells used in the energy sector for directly converting chemical energy of fuel into electric energy.

[0002]

2. Description of the Related Art A power generation system using a solid polymer electrolyte fuel cell is being developed as a system usable for automobiles, trains, ships, spacecraft, deep sea power generation facilities, ground power generation facilities and the like.

The solid polymer electrolyte fuel cells that have been proposed so far have, as shown in FIGS. 7 to 9, an oxygen membrane 2 and a fuel on both sides of an electrolyte membrane 1 having a platinum electrode catalyst supported on the surface. The cells C, which are sandwiched between both gas diffusion electrodes of the electrode 3, are stacked via the separators 4 to form a stack. Each separator 4 has a gas passage 5 on both front and back surfaces.
To supply and discharge the oxidant gas O ₂ to the oxygen electrode 2 side,
Further, in order to supply and discharge the fuel gas H ₂ to the side of the fuel electrode 3, the flow path holes 6 and 7 for supplying and discharging the oxidant gas are provided in the peripheral portion except the electrode reaction portion in the central portion, and the fuel gas H _2. Gas supply and discharge passage holes 8 and 9 are provided so that the oxidant gas and the fuel gas are distributed in the respective gas passages 5 with the separator 4 interposed therebetween, as shown in FIG. As described above, the stack is held by the end plates 10 and 11, and a predetermined tightening force is applied to the holes 13 provided at the four corners through the tightening bolts 12.

In the conventional solid polymer electrolyte fuel cell,
The gas supplied from the outside may be supplied after being humidified, but there is also one in which a humidifying unit 14 is provided as shown in FIG. 7 so that the gas is humidified before being guided to the laminated portion of the cell C that performs power generation. Further, since the reaction of the fuel cell is an exothermic reaction, as shown in FIG. 7, a cooling unit 15 is provided for every several cells.

The flow of the gas supplied to the fuel electrode 3 side and the oxygen electrode 2 side of each cell C and the flow of the cooling water supplied to the cooling unit 15 are shown in FIGS. 9 (a), 9 (b) and 9 (c). As shown in FIG. 2, both the fuel gas and the oxidant gas are supplied from different inlets of the end plate 10 and are humidified by the humidifying section 14, and then the humidified gas flows through the power generation cell section 16 and then the outlet of the end plate 10. The cooling water is supplied from the inlet of the end plate 10 to cool the power generation cell portion 16 and then discharged to the outside from the outlet of the end plate 10 via the humidifying portion 14. I am doing it.

In the figure, 17 is a center bus (+ pole), 18
Is a rubber pad, and 19 is a perforated fiber support.

[0007]

However, since the above-mentioned conventional solid polymer electrolyte fuel cell has a very large current density, it has the possibility of being reduced in size and weight, but in order to increase the output. Requires higher voltage.
For this, the number of cells must be increased,
Since the voltage per cell stage is 0.7 to 0.8 V, the length of the power generation cell section 16 shown in FIGS. 9A, 9B, and 9C tends to be long. When the length of the power generation cell portion 16 becomes long, gas supply / discharge is performed as shown in FIGS. 8 (a) and 8 (b), and oxidant gas supply / discharge flow passage holes 6 and 7 and fuel gas supply / discharge flow are provided. Due to the configuration having only the passage holes 8 and 9, it becomes difficult to properly supply gas to each cell and discharge the remaining gas, and to discharge water generated on the oxygen electrode 2 side appropriately, and to improve the characteristics of the cell. In addition to the possibility of deterioration, it may be difficult to perform uniform cooling, and the cell characteristics may deteriorate due to uneven temperature distribution. Especially, if the generated water is not efficiently discharged,
The concentration overvoltage, that is, the supply and removal of the reactants and reaction products at the electrode is not smoothly performed and the reaction of the electrode is disturbed, increases, and the cell voltage decreases. In addition, when applied to an automobile, a ship, or the like having severe shaking, acceleration, inclination, etc., the distribution of the generated water may differ from cell to cell, and the generated water may stay in some cells. In such a case, the voltage of the cell in which the generated water is retained is lowered, and the gas flow is impeded by the retained generated water, so that the output distribution in the stack may be non-uniform.

In view of the above, the present invention provides a gas or moisture supply or gas supply when the number of cell stages is increased to obtain a large output, or when the conditions such as shaking, acceleration and inclination of a car or a ship are severe.
It is intended to appropriately discharge the generated water and to easily maintain the temperature of the entire cell to be uniform so as to improve the characteristics of the cell.

[0009]

In order to solve the above-mentioned problems, the present invention has a method in which a polymer electrolyte membrane having a platinum electrode catalyst supported on the surface thereof is sandwiched by both gas diffusion electrodes of an oxygen electrode and a fuel electrode. The oxidant gas is supplied to the side and the fuel gas is supplied to and discharged from the fuel electrode side, and the cells are stacked in multiple layers via separators, and a cooling unit is provided for every several cells to form a stack. In the polymer electrolyte fuel cell, the oxygen electrode side separator and the fuel electrode side separator of the cell are provided with a supply port and a discharge port for supplying and discharging an oxidant gas and a fuel gas from the outside, respectively, and an electrode part. And the separator on the oxygen electrode side is provided with a supply port and a discharge port for supplying and discharging cooling water for cell cooling.

Further, a line with a flow rate control valve is connected to the oxidant gas outlet provided on the oxygen electrode side separator of each cell, an ejector is attached to the line, and the flow rate control valve is connected to the cell voltage detection value. Alternatively, it is adjusted by the controller based on the detected water level of the produced water in the cell, and the produced water in the cell is discharged by passing the compressed air through the ejector, or it is provided in the fuel electrode side separator of each cell. A hydrogen cylinder or a reformer is connected to the line connected to the fuel gas supply port, and the flow rate control valve provided on the line is adjusted by the controller based on the detected value of the cell voltage.
It may be possible to supply fuel.

Furthermore, the flow rate control valve may be adjusted by a controller that uses shaking, acceleration, inclination, vibration, and the voltage of each cell as a control signal to perform optimum control of all cells constituting the stack. Good.

[0012]

[Function] When the generated water accumulates and the flow of gas is obstructed, the voltage of the cell decreases, so the voltage of the cell is detected or the water level of the generated water in the cell is detected to generate it. By positively discharging the water, the generated water can be efficiently discharged, and it is possible to prevent a voltage drop and an uneven output distribution. Further, the temperature of the cell can be controlled by the cooling water supplied from the outside of the cell, and if the inert gas is supplied at a high pressure to the flow path of the cooling water, leakage of the oxidant gas and the fuel gas from the cell is prevented. It becomes possible to prevent it.

When a high-concentration fuel gas is supplied from the outside to the fuel electrode side of the cell where the voltage has dropped, the amount of fuel gas in the cell where the concentration has dropped can be adjusted, and fluctuations, accelerations, inclinations, and vibrations can be achieved. By adjusting the amount of gas and cooling water on the outlet side for each cell or cell group of all cells of the stack based on the command from the controller based on the voltage of each cell,
The cell performance and the characteristics of the entire stack can be controlled to be the best.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 5 are all examples of the present invention, and the power generation cell section 16 is similar to the conventional system shown in FIG.
And has a humidifying section 14 and a cooling section 15 and is laminated horizontally,
In the configuration in which the gas is distributed to the power generation cell unit 16 after being discharged through the humidifying unit 14 and discharged, the electrolyte membrane 1
Is the same size as the oxygen electrode 2 and the fuel electrode 3 serving as gas diffusion electrodes, and these electrodes are made of metal and the gas passages are formed by directly providing irregularities on the electrodes.

That is, a solid polymer electrolyte membrane 1 having a platinum electrode catalyst supported on the surface is sandwiched between an oxygen electrode 2 and a fuel electrode 3 having the same size, and the back surface of the oxygen electrode 2 is uneven in multiple rows. In addition to forming the gas passages 5a, a plurality of rows of concavities and convexities extending in the direction orthogonal to the gas passages 5a are formed on the back surface side of the fuel electrode 3 to form the gas passages 5b, and the oxidizing gas on the oxygen electrode 2 side. One cell C for supplying and discharging O ₂ and the fuel gas H ₂ to and from the fuel electrode 3 side is provided with an oxygen electrode side separator 4a and a fuel electrode side separator 4b each having a concave portion at the center of one surface. And the peripheral portions of the separators 4a and 4b are sealed by interposing an insulating and sealing material between them and the gas passages 5a and 5b formed in the electrodes 2 and 3 are formed in the separators 4a and 4b. Header parts 20 at the positions of both ends of a, 20b and 20c, 20d are formed respectively, and the oxygen electrode side separator 4a is provided with a supply flow passage hole 21 and a discharge flow passage hole 22 capable of supplying and discharging the oxidant gas from the outside to the header portions 20a and 20b. In addition to being provided as shown in (a), the fuel electrode side separator 4b is provided with a supply flow path hole 23 and a discharge flow path hole 24 capable of supplying and discharging the fuel gas from the outside to the header portions 20c and 20d in FIG. Provide as shown.

Further, in the separators 4a and 4b which hold the one cell C, a plurality of flow passage holes 6 for supplying the oxidizing gas are provided.
And a discharge flow path hole 7 are provided so as to penetrate in the stacking direction, and a plurality of fuel gas supply flow path holes 8 and a discharge flow path hole 9 are provided so as to penetrate in the stacking direction. In the separator 4a, the oxidant gas supply / discharge passage holes 6, 7 communicate with the header portions 20a, 20b, and in the fuel electrode side separator 4b, the fuel gas supply / discharge passage holes 8, 9 are formed in the header portion. It is designed to communicate with 20c and 20d.

Further, the oxygen electrode side separator 4a and the fuel electrode side separator 4b are provided with cooling water passage holes 25 penetrating therethrough in the stacking direction and cooling water passage holes 26 for cell cooling.

27 is an oxidizing gas supply port, 28 is an oxidizing gas discharge port, 29 is a fuel gas supply port, 30 is a fuel gas discharge port, 31 is a cooling water supply port, and 32 is a cooling port. The same outlets as those of FIGS. 7 to 9 which are water outlets are denoted by the same reference numerals.

The solid polymer electrolyte fuel cell of the present invention comprises:
The cells having the above-mentioned configuration are stacked in a lateral direction in multiple stages to form a stack.
By using 8, it is possible to positively eliminate the generated water for each cell, or to shake, accelerate, tilt, vibrate, such as a car or a ship, for each cell or cell group.
It is possible to control gas or water by the cell voltage or the like, or to adjust the amount of fuel gas by using the fuel gas supply port 29 to each cell, or for each cell, It is possible to control the fuel gas for each cell group or for the entire stack.

FIG. 1 shows an embodiment in which the produced water is positively removed for each cell. A discharge line 34 having a flow rate control valve 33 in the middle is connected to the oxidant gas discharge port 28. Then, the ejector 35 is attached to the tip of the ejector 35, and the air compressed by the compressor 36 is supplied to the ejector 35.
The generated water is positively discharged from the oxygen electrode 2 side by the suction action generated by passing the air through the ejector 35, and the air that has driven the ejector 35 is oxidant gas after the moisture is removed by the moisture separator 37. Cell C to be supplied directly to the cell C, or to be released to the atmosphere,
The flow rate control valve 33 is operated by the controller 38 on the basis of the detected voltage value e of each cell and the detected water level f of each cell, and is adjusted by a command from the controller 38.

Therefore, when trying to eliminate the water generated on the oxygen electrode 2 side, the cell voltage and the water level of each cell are monitored, and the cause of the cell whose voltage has dropped extremely is controlled by the controller. When the cause is that the generated water is not removed well and the water level is above a certain level, the discharge port 28 of the oxidant gas of the cell is communicated. Flow control valve 33
Is opened and compressed air is supplied to the ejector 35 to pass therethrough, thereby driving the ejector 35 and discharging the produced water. As a result, the generated water in the cell is satisfactorily discharged, so that the situation where the flow of gas is obstructed by the generated water is avoided, and the fuel utilization rate and oxidant utilization rate in the cell can be increased. .

Next, when performing optimum control of all cells forming one stack, the controller 38 sends the control signals as shaking a, acceleration b, inclination c, vibration d, voltage detection value e for each cell, Etc. are input, and the discharge amount of gas or water is controlled by a command from the controller 38 using feedforward control or various optimum control methods. In this case, it is difficult to control the stack as a whole, but gas or water is controlled for each cell as shown in FIG. 3A, or some cells are grouped as shown in FIG. By doing so, optimum control of the entire stack can be performed.

FIG. 4 shows an example in which the amount of hydrogen as a fuel gas can be adjusted for each cell. Hydrogen is supplied to the fuel electrode 3 side through a line 39 at the fuel gas supply port 29 of each cell. The cylinder 40 or the reformer 41 is connected, the detected value e of the voltage for each cell is input to the controller 38 to monitor the voltage for each cell, and the flow rate control valve 43 is opened for the cell where the voltage has dropped to open the fuel, That is, the gas from which CO has been removed by the CO removal device 42 is selectively supplied from the hydrogen gas from the hydrogen cylinder 40 or the reformed gas from the reformer 41 to increase the fuel concentration.

When the fluctuation range and fluctuation speed of the load for power use are large, there may be a large difference in fuel temperature between the cells near the end plate 10 and the cells far from the end plate 10 shown in FIG. By selectively supplying a high-concentration fuel to a cell in which the fuel concentration is low and the voltage is low, the load response can be improved. At this time, it is possible to keep the moisture content in the cell optimal by combining the water discharge method shown in FIG. 1, and the platinum catalyst supported on the solid polymer electrolyte membrane 1 is poisoned by CO. However, if O ₂ gas is supplied instead of the hydrogen gas from the hydrogen cylinder 40 supplied from the fuel gas supply port 29 or the reformed gas from the reformer 41, CO ₂ can be obtained. As a result, cells poisoned by CO can be rapidly recovered. In FIG. 4, if a humidifier 44 is provided in the middle of the line 39 connected to the fuel gas supply port 29, it becomes possible to humidify and supply hydrogen gas or reformed gas, and adjust the moisture content in the cell. be able to.

As shown in FIG. 4, the supply amount of the fuel gas supplied from the outside to the fuel electrode side of each cell is used as a control signal for fluctuation a,
It can be optimally controlled by signals such as acceleration b, inclination c, vibration d, and cell voltage detection value e. FIG. 5 shows an example thereof, and in this case, for each cell as shown in (a),
Control can be performed for each cell group as in (b) or for the entire stack as in (c).

Next, FIG. 6 shows another embodiment of the present invention. In the above embodiment, the oxygen electrode 2 and the fuel electrode 3 are made of metal and the unevenness for directly forming the gas passage is formed on the metal. Instead, a single porous plate made of carbon or the like is used, and the work of directly providing the concavities and convexities that directly form the gas passages becomes difficult. Is formed, and the other structure is the same as that of the above-mentioned embodiment.

Even in the case of this embodiment, the control can be performed as shown in FIGS. 1 and 3 to 5.

The present invention is not limited to the above-mentioned embodiment, and for example, the case where the gas is supplied from the outside and then humidified before being supplied to the cell has been described as an example, but the external humidifier is used. It was shown that the humidified gas may be supplied to the cell, and the case where the oxidant gas and the fuel gas are made to flow in a cross flow, but the flow directions of the gas are counter flow and parallel flow. The case where the gas passage and the gas supply / discharge channel hole may be provided and the case where the electrolyte membrane 1 has the same size as the gas diffusion electrodes 2 and 3 are shown, but the electrolyte membrane 1 has the same size as the separators 4a and 4b. It is also possible to use the oxygen electrode side separator 4a and the fuel electrode side separator 4b as the separators, and to form the recesses corresponding to the electrodes on the surface side of each of the separators 4a and 4b. A piece of separation A portion for arranging the oxygen electrode 2 and the fuel electrode 3 may be formed in the central portion of both surfaces of the above, or a gas passage may be formed, and a supply port 31, a discharge port 32 for supplying and discharging the cell cooling water, It goes without saying that the cooling water passage hole 26 is provided in the fuel electrode side separator and that various changes can be made without departing from the scope of the present invention.

[0030]

As described above, according to the solid polymer electrolyte fuel cell of the present invention, the electrolyte membrane is sandwiched between the gas diffusion electrodes of both the oxygen electrode and the fuel electrode, and the oxidant gas is supplied to and discharged from the oxygen electrode side. And a structure in which cells for supplying and discharging the fuel gas to and from the fuel electrode side are stacked via a separator to form a stack, and the oxygen electrode is supplied to and discharged from the oxidant gas. In addition to providing a passage hole, it is possible to supply and discharge the oxidant gas from the outside to the oxygen electrode side for each cell, and also to supply and discharge the fuel gas to the fuel electrode from the outside as well. Since a cooling water passage for supplying and discharging cooling water from the outside is provided and the cooling water passage is communicated with the cooling section provided in the stack, the following excellent effects can be obtained. (i) Since the discharge line is connected to the outlet of the oxidant gas provided on the oxygen electrode side to actively discharge the generated water,
It is possible to prevent the situation where the generated water is not discharged well and the concentration overvoltage becomes large to lower the cell voltage, or the generated water obstructs the gas flow to make the output distribution in the stack uneven. (ii) The characteristics of each cell in the stack vary greatly depending on the fuel utilization rate, and if there is uneven fuel concentration in each cell, the load responsiveness will deteriorate, but if the fuel concentration decreases and the voltage drops, On the other hand, since the fuel gas can be supplied from the outside through the fuel gas supply port, the load response can be improved by selectively supplying the high-concentration fuel to the cell whose voltage has dropped. (iii) Since a cooling water supply port and a cooling water supply port are provided in the separator for each cell or group of cells, temperature control can be performed for each cell or group of cells. By flowing an inert gas slightly higher in pressure than the agent gas, not only the cooling of the cell but also the leakage of the fuel gas and the oxidant gas from the cell to the outside can be prevented,
Furthermore, by constantly checking the components of this inert gas, it is possible to detect that the fuel gas and the oxidant gas have leaked from the cell. (iv) The number of cells is increased to obtain a large output, and the gas is controlled for each cell and each cell group in the entire stack, which is effective for improving the characteristics.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, and is a cut side view of one cell showing an example in which generated water is discharged.

FIG. 2 is a cross-sectional view of FIG. 1, in which (a) is a view taken in the direction of arrow A,
(B) is a view on arrow B.

3 shows an example of controlling the amount of gas and generated water on the oxygen electrode side by stacking the cells of FIG. 1 in multiple stages, and (a) is a sectional side view when controlling for each cell. , (B) are cut-away side views in the case where some cells are controlled as a group.

FIG. 4 is a cut side view showing an example in which high concentration fuel is externally supplied to the fuel electrode side of the cell of FIG.

FIG. 5 shows control of the amount of fuel to the fuel electrode side by stacking cells in multiple stages. (A) is a sectional side view when performing control for each cell, and (b) is some FIG. 3C is a cut side view when the cells are controlled as a group, and FIG. 7C is a cut side view when the entire stack is controlled.

FIG. 6 is a cut side view of one cell showing another embodiment of the present invention.

FIG. 7 is a schematic sectional side view showing an example of a conventional solid polymer electrolyte fuel cell.

FIG. 8 shows the front of the cell in FIG. 7, (a)
Is a diagram showing the oxygen electrode side and the separator, and (B) is a diagram showing the fuel electrode side and the separator.

FIG. 9 shows an example of the flow of each gas and cooling water in the conventional example of FIG. 7, (a) showing the flow of fuel gas,
(B) is a figure which shows the flow of oxidizer gas, (C) is a figure which shows the flow of cooling water.

[Explanation of symbols]

 1 Electrolyte Membrane 2 Oxygen Electrode 3 Fuel Electrode 4a Oxygen Electrode Side Separator 4b Fuel Electrode Side Separator 5a, 5b Gas Passage 15 Cooling Part 21 Oxidizing Gas Supply Flow Path Hole 22 Oxidizing Gas Discharge Flow Path Hole 23 Fuel Gas Supply Flow Path Hole 24 Fuel Gas Discharge Channel Holes 25, 26 Cooling Water Channel Hole 27 Oxidizing Gas Supply Port 28 Oxidizing Gas Discharge Port 29 Fuel Gas Supply Port 30 Fuel Gas Discharge Port 31 Cooling Water Supply Port 32 Cooling Water Discharge port 33 Flow control valve 34 Line (discharge line) 35 Ejector 38 Controller 39 Line 40 Hydrogen cylinder 41 Reformer 43 Flow control valve C cell

Claims (6)

[Claims] 1. A polymer electrolyte membrane having a platinum electrode catalyst supported on its surface is sandwiched by both gas diffusion electrodes of an oxygen electrode and a fuel electrode, an oxidant gas is provided on the oxygen electrode side, and a fuel is provided on the fuel electrode side. In a solid polymer electrolyte fuel cell in which cells each having gas supply and discharge are laminated in multiple layers via a separator, and a cooling unit is provided for every several cells as a stack, a separator on the oxygen electrode side of the cell is provided. And a separator on the fuel electrode side are provided with a supply port and a discharge port for supplying and discharging the oxidant gas and the fuel gas from the outside, respectively, to communicate with the gas passage of the electrode part, and the separator on the oxygen electrode side is connected to the cell. A solid polymer electrolyte fuel cell having a structure provided with a supply port and a discharge port for supplying and discharging cooling water for cooling. 2. A line with a flow rate control valve is connected to an oxidant gas outlet provided in the oxygen electrode side separator of each cell,
An ejector is attached to the line, and the flow control valve is
2. The solid according to claim 1, wherein the controller adjusts based on the detected value of the cell voltage or the detected water level of the produced water in the cell, and the produced water in the cell is discharged by passing compressed air through an ejector. Polymer electrolyte fuel cell. 3. A hydrogen cylinder or a reformer is connected to a line connected to a fuel gas supply port provided in a fuel electrode side separator of each cell, and a flow control valve provided in the line is connected to a cell voltage detection value. Based on the controller,
The solid polymer electrolyte fuel cell according to claim 1, wherein the fuel can be supplied. 4. A flow rate control valve is adjusted by a controller that uses shaking, acceleration, inclination, vibration, and a voltage for each cell as a control signal to perform optimum control of all cells constituting the stack. Solid polymer electrolyte fuel cell. 5. The solid polymer electrolyte fuel cell according to claim 1, wherein the electrode is made of metal to directly form a gas passage. 6. The solid polymer electrolyte fuel cell according to claim 1, wherein the electrode is a single carbon plate and a gas passage is formed in the separator.