JPH0935729A - Phosphoric acid fuel cell - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphoric acid fuel cell structure for recovering phosphoric acid scattered during power generation operation.

[0002]

2. Description of the Related Art A phosphoric acid fuel cell is a power generator that supplies hydrogen and oxygen and directly produces electricity by an electrochemical reaction. FIG. 5 is an exploded perspective view showing the basic structure of a unit cell conventionally used for this type of phosphoric acid fuel cell. As shown in the figure, the matrix 3 supporting the phosphoric acid as the electrolyte is flatly oxidized by the oxidant electrode base material 11 made of hydrophilic porous carbon paper and the oxidant electrode catalyst layer 12. It is sandwiched between the agent electrode 1 and a flat plate-shaped fuel electrode 2 formed of a fuel electrode base material 21 made of hydrophilic porous carbon paper and a fuel electrode catalyst layer 22, and an oxidant gas is provided on both main surfaces thereof. Gas flow groove 6 that flows through
Oxidizer pole carbon plate 4 made of porous carbon having
And a fuel electrode carbon plate 5 made of porous carbon having a gas flow groove 9 through which a fuel gas flows, and these are stacked to form a unit cell.

FIG. 6 is a plan view showing the structure of the gas flow groove 6 of the oxidant electrode carbon plate 4 used in the unit cell shown in FIG. 5, which serves as an inlet for a reaction gas, that is, an oxidant gas. A plurality of linear ribs 7 from the side surface to the opposite side surface that serves as the outlet.
By arranging, the linear gas flow grooves 6 are formed between the respective ribs 7. Fuel electrode carbon plate 5
Similarly, a linear gas flow groove 9 is also formed in this. In addition, the oxidizer electrode carbon plate 4 and the fuel electrode carbon plate 5
Not only plays a role of passing the reaction gas through the gas flow groove 6 and the gas flow groove 9 thus formed, but also plays a role of storing phosphoric acid by using porous carbon. It plays the role of collecting phosphoric acid that scatters during power generation.

In the conventional phosphoric acid fuel cell, the unit cells thus formed are stacked to form a fuel cell stack,
A manifold is incorporated into each side surface of the unit cell to supply and discharge an oxidant gas and a fuel gas to cause an electrochemical reaction in each unit cell to generate electricity.

[0005]

When the reaction gas is supplied during the power generation operation as described above, the reaction gas is consumed by the electrochemical reaction, and the reaction product is discharged together with the remaining reaction gas. At this time, part of the phosphoric acid evaporates as the temperature rises, scatters, and is mixed with the reaction product and discharged.

Since the temperature in the central portion of the surface of the unit cell is higher than that in the side edge portion, a large amount of phosphoric acid evaporates in the central portion and passes through the gas flow groove 6 of the oxidizer electrode carbon plate 4, for example. And is led to the downstream side. Since the gas flow groove 6 is formed linearly, the reaction exhaust gas flows smoothly and is taken out to the outside, but a part of the evaporated phosphoric acid has a relatively low temperature on the downstream side. Recondenses at the side edges. Therefore, as the power generation operation continues, phosphoric acid concentrates and accumulates on the downstream side edge portion and fills the pores of the porous carbon forming the oxidizer electrode carbon plate 4 or the fuel electrode carbon plate 5. At the same time, the pores of the porous carbon paper forming the oxidizer electrode base material 11 or the fuel electrode base material 21 are filled.

When the pores continue to be filled in such a concentrated manner, the diffusion of the reaction gas supplied to the oxidant electrode catalyst layer 12 or the fuel electrode catalyst layer 22 through the pores of the porous carbon paper is hindered and corrosion occurs. There is a risk of damage and damage to the battery voltage. Further, since the gas flow groove 6 is formed in a straight line as described above, the reaction exhaust gas smoothly flows and is taken out to the outside, and most of the evaporated phosphoric acid is discharged to the outside. Therefore, phosphoric acid needs to be replenished at short intervals in order to maintain the battery performance, and maintenance is not easy.

The present invention solves the above-mentioned problems in the prior art, eliminates the risk of damage due to concentrated recondensation of phosphoric acid, has a long phosphoric acid supply interval, and is stable over a long period of time. An object is to provide a phosphoric acid fuel cell capable of power generation operation.

[0009]

In order to achieve the above object, in the present invention, a flat plate-shaped matrix carrying phosphoric acid of an electrolyte is sandwiched between a flat plate-shaped oxidant electrode and a fuel electrode, and It is formed by arranging an oxidant electrode carbon plate having a gas flow passage through which an oxidant gas flows and a fuel electrode carbon plate having a gas flow passage through which a fuel gas flows on both main surfaces. In a phosphoric acid fuel cell equipped with a cell, the gas passages of the oxidizer electrode carbon plate and the fuel electrode carbon plate are linear gas passages formed in the direction from the end face on the gas inlet side toward the end face on the gas outlet side. It is formed by a flow groove and a linear gas communication groove arranged in a direction orthogonal to the gas flow groove so as to commutate the gas flow flowing through the gas flow groove in the orthogonal direction.

Further, the length of the gas flow groove defined by the gas communication groove in the flow direction is shortened from the gas inlet side toward the gas outlet side. Also,
The tabular matrix supporting the phosphoric acid of the electrolyte is formed into a tabular oxidant electrode formed of an oxidant electrode base material and an oxidant electrode catalyst layer made of hydrophilic porous carbon paper, and a hydrophilic porous substrate. Porous material sandwiched between a fuel electrode base material made of high-quality carbon paper and a flat fuel electrode formed by a fuel electrode catalyst layer, and having gas passages for passing an oxidant gas on both main surfaces thereof. In the phosphoric acid fuel cell including a unit cell formed by arranging the oxidizer electrode carbon plate of (1) and a porous fuel electrode carbon plate having a gas passage for flowing a fuel gas, At least one of the material and the fuel electrode base material, or the oxidizer electrode carbon plate and the fuel electrode carbon plate is provided with a water repellent treatment part that is linearly water repellent in a direction orthogonal to the gas flow direction. To do.

Further, the interval between the linear water-repellent treatment parts to be installed is made shorter from the gas inlet side toward the gas outlet side.

[0012]

As described above, the gas passages of the oxidizer electrode carbon plate and the fuel electrode carbon plate are passed through the straight gas passage groove formed in the flow direction of the reaction gas and the gas passage groove. If the gas flow groove is formed by a gas flow groove and a straight gas communication groove arranged in the orthogonal direction so that the gas flow is commutated in the orthogonal direction, the reaction gas stays in the commutation region for a relatively long time. Will be done. Therefore, the phosphoric acid evaporated due to power generation is condensed and recovered not only in the downstream side edge portion but also in the main commutation region.

Further, if the length of the gas flow groove defined by the gas communication groove in the flow direction is shortened from the gas inlet side toward the gas outlet side, the reaction gases are relatively Since the commutation region that stays for a long time will be densely distributed as it goes to the gas outlet side where the phosphoric acid vapor becomes larger, the phosphoric acid evaporated during power generation is dispersed and more effective. Will be condensed and collected.

Further, at least one of the oxidizer electrode base material and the fuel electrode base material, or at least one of the oxidizer electrode carbon plate and the fuel electrode carbon plate is subjected to a linear water repellent treatment in a direction orthogonal to the gas flow direction. If the water repellent treatment part is provided, the movement of the condensed phosphoric acid to the downstream side due to the flow of the reaction gas is suppressed by the water repellent treatment part, so that the concentrated deposition on the downstream part is prevented.

Further, if the interval between the linear water-repellent treatment portions to be installed is shortened from the gas inlet side to the gas outlet side, a larger amount of condensation is generated on the gas outlet side having a lower temperature,
Since the distance traveled to the downstream side by the flow of the recovered phosphoric acid due to the reaction gas is suppressed to a smaller extent, the condensed and recovered phosphoric acid will be dispersed and deposited, and even during long-term operation, it will be transferred to the downstream portion. Concentrated deposition will be prevented.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of an oxidizer electrode carbon plate showing a first embodiment of a phosphoric acid fuel cell of the present invention. In the figure, on the oxidizer electrode carbon plate 4A, from the inlet side (upper end portion in the figure) of the reaction gas, that is, the oxidant gas, to the outlet side (lower end portion in the figure).
Two types of ribs extending in the flow direction toward the flow direction are incorporated, and a rib 7A having a long length on the upstream side and a rib 7B having a relatively short length on the downstream side are spaced from each other in the flow direction. The gas flow grooves 6A and 6B and the gas communication groove 8A are formed by arranging the gas flow grooves 6A and 6B in a direction orthogonal to each other. In this configuration, the reaction gas supplied from the inlet flows through the gas flow groove 6A, is blocked by the upstream end of the rib 7B and commutates, flows through the gas communication groove 8A, and then flows through the gas flow groove 6B. It will be discharged from the outlet. At this time, since the reaction gas stays in the commutation region for a relatively long time,
Evaporated phosphoric acid due to power generation is more effectively condensed and recovered in the main commutation region. Therefore, the evaporated phosphoric acid is recovered not only in the downstream side edge portion where the temperature is the lowest, but also in the main commutation region, so that the rate of scattering and discharging to the outside is reduced, and the downstream side edge portion is reduced. Since the concentration on the area will be alleviated, the risk of damage will be suppressed.

FIG. 2 shows a second embodiment of the phosphoric acid fuel cell of the present invention.
3 is a plan view of an oxidizer electrode base material showing the example of FIG. In the figure, the oxidizer electrode base material 11A is made of polyfluoroethylene in a direction orthogonal to the flow direction of the reaction gas, that is, the oxidant gas from the inlet side (upper end in the figure) toward the outlet side (lower end in the figure). A water repellent treatment part 10 is provided and arranged so that the distance between the book and the water repellent treatment part 10 becomes shorter toward the downstream side. In this configuration, the condensed phosphoric acid becomes difficult to move through the water repellent treatment section 10, so that the condensed phosphoric acid is suppressed from moving to the downstream side due to the flow of the reaction gas, and concentrated deposition on the downstream portion is prevented. It Therefore, the phosphoric acid is dispersed and held, and the concentration on the downstream side edge portion is alleviated, so that the risk of damage is suppressed.

FIG. 3 shows a third embodiment of the phosphoric acid fuel cell of the present invention.
FIG. 3 is a plan view of an oxidizer electrode carbon plate showing the example of FIG. In the figure, on the oxidizer electrode carbon plate 4B, ribs 7C on the upstream side, ribs 7D on the midstream portion, and ribs 7E on the downstream side are arranged at intervals in the flow direction and offset in the direction orthogonal to the flow. As a result, the gas flow grooves 6C, 6D and 6E and the gas communication grooves 8B and 8C are formed. The reaction gas supplied from the inlet flows through the gas flow groove 6C, is blocked by the upstream end of the rib 7D and commutates, flows through the gas communication groove 8B, then flows into the gas flow groove 6D, and further upstream of the rib 7E. The flow is blocked by the end, commutates, passes through the gas communication groove 8C, then flows through the gas communication groove 6E, and is discharged from the outlet. At this time, since the reaction gas stays in the two commutation regions for a relatively long time, the phosphoric acid evaporated with the power generation is
In these commutation regions, they are more effectively condensed and recovered. Further, the oxidizer electrode carbon plate 4B is provided with two water repellent treatment parts 10 made of polyfluoroethylene in a direction orthogonal to the flow direction of the reaction gas. Therefore, the phosphoric acid condensed and recovered in the above-mentioned commutation region is more effectively retained in each section separated by the two water-repellent treatment sections 10, so that the phosphoric acid is effectively treated. It will be dispersed and collected and retained, and stable operation can be achieved over a long period of time.

FIG. 4 shows the fourth embodiment of the phosphoric acid fuel cell of the present invention.
FIG. 3 is a plan view of an oxidizer electrode carbon plate showing the example of FIG. In the figure, on the oxidizer electrode carbon plate 4C, ribs 7F arranged in the longitudinal direction of the flow direction of the reaction gas and ribs 7G arranged in the longitudinal direction of the direction orthogonal to the flow direction of the reaction gas are dispersed. The reaction gas flows between the gas communication groove and the gas communication groove formed by these ribs. Similar to the embodiment of FIG. 3, the reaction gas stays for a relatively long time when flowing through the gas communication groove, and the phosphoric acid evaporated due to the power generation is more effectively condensed in these commutation regions, Will be collected. Further, the oxidizer electrode carbon plate 4C is provided with a water repellent treatment portion 10 in a direction orthogonal to the flow direction of the reaction gas, and the phosphoric acid condensed and recovered in the commutation region is treated more effectively. Since it is separately held in both sections separated by the section 10, the phosphoric acid is effectively dispersed and collected and held, and stable operation can be performed for a long period of time.

In each of the above-mentioned first, third and fourth embodiments, the oxidizer electrode carbon plate is shown as an example, but the fuel electrode carbon plate is not limited to the oxidizer electrode carbon plate. It is clear that the same effect can be obtained even if the same means is applied to the fuel electrode base material instead of the oxidizer electrode base material of the second embodiment. It is obvious that the same effect can be obtained even if the measures are taken.

[0021]

As described above, according to the present invention, as described above, the gas passages of the oxidizer electrode carbon plate and the fuel electrode carbon plate that constitute the unit cell of the phosphoric acid fuel cell are connected to the reaction gas. A straight gas flow groove formed in the flow direction of
Since the gas flow through the gas flow groove was formed by the gas flow groove and the linear gas communication groove arranged in the orthogonal direction so as to divert the flow of the gas in the orthogonal direction, it evaporated due to power generation. Phosphoric acid will also be condensed and collected in this commutation area, and since it will not be concentrated and condensed only on the downstream side edge, there is a risk of damage due to concentrated recondensation of phosphoric acid. Thus, a phosphoric acid fuel cell that does not have a long supply interval of phosphoric acid and can stably perform power generation for a long time can be obtained.

Further, if the length of the straight gas flow groove defined by the straight gas communication groove in the flow direction becomes shorter from the gas inlet side toward the gas outlet side. , The commutation region in which the reaction gas stays for a relatively long time is densely arranged as it goes to the gas outlet side where the phosphoric acid vapor becomes larger, so the phosphoric acid vapor evaporated with the power generation is It is more effective because it is dispersed and condensed and recovered more effectively.

Further, at least one of the oxidizer electrode base material and the fuel electrode base material, or at least one of the oxidizer electrode carbon plate and the fuel electrode carbon plate is subjected to a linear water repellent treatment in a direction orthogonal to the gas flow direction. If the water repellent treatment unit is provided, the movement of the condensed phosphoric acid to the downstream side due to the flow of the reaction gas is suppressed by the water repellent treatment unit, so that concentrated deposition on the downstream portion is prevented and the reaction gas It is possible to obtain a phosphoric acid fuel cell capable of stable power generation operation for a long period of time without the risk of damage due to the inhibition of diffusion of hydrogen.

Further, if the interval between the linear water-repellent treatment portions to be installed is shortened from the gas inlet side toward the gas outlet side, a larger amount of condensation occurs on the gas outlet side having a lower temperature,
Since the distance traveled to the downstream side by the flow of the recovered phosphoric acid due to the reaction gas is suppressed to a smaller extent, the condensed and recovered phosphoric acid will be dispersed and deposited, and even during long-term operation, it will be transferred to the downstream portion. Since concentrated deposition is prevented, there is no risk of damage due to inhibition of reaction gas diffusion, the phosphoric acid replenishment interval is long, and a phosphoric acid fuel cell capable of stable power generation operation for a long period of time can be obtained. It will be.

[Brief description of drawings]

FIG. 1 is a plan view of an oxidizer electrode carbon plate showing a first embodiment of a phosphoric acid fuel cell of the present invention.

FIG. 2 is a plan view of an oxidizer electrode base material showing a second embodiment of the phosphoric acid fuel cell of the present invention.

FIG. 3 is a plan view of an oxidizer electrode carbon plate showing a phosphoric acid fuel cell according to a third embodiment of the present invention.

FIG. 4 is a plan view of an oxidizer electrode carbon plate showing a phosphoric acid fuel cell according to a fourth embodiment of the present invention.

FIG. 5 is an exploded perspective view showing a basic configuration of a unit cell that has been conventionally used for this type of phosphoric acid fuel cell.

6 is a plan view showing a configuration of a gas flow groove 6 of an oxidizer electrode carbon plate 4 used in the unit cell shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 oxidizer electrode 11, 11A oxidizer electrode base material 12 oxidizer electrode catalyst layer 2 fuel electrode 21 fuel electrode base material 22 fuel electrode catalyst layer 3 matrix 4, 4A oxidizer electrode carbon plate 4B, 4C oxidizer electrode carbon plate 5 Fuel electrode Carbon plate 6,6A Gas flow groove 6B, 6C Gas flow groove 6D, 6E Gas flow groove 7,7A Rib 7B, 7C Rib 7D, 7E Rib 7F, 7G Rib 8,8A Gas communication groove 8B, 8C Gas communication groove 9 Gas flow groove 10 Water repellent treatment part

Claims (4)

[Claims] 1. A flat plate-shaped matrix that supports phosphoric acid as an electrolyte is sandwiched between a flat plate-shaped oxidant electrode and a fuel electrode, and a gas passage for passing an oxidant gas is provided on both main surfaces thereof. A phosphoric acid fuel cell comprising a single cell formed by arranging an oxidizer electrode carbon plate and a fuel electrode carbon plate having a gas flow passage through which a fuel gas flows. The gas flow path of the carbon plate is a straight gas flow groove formed in the direction from the gas inlet side end surface toward the gas outlet side end surface, and the gas flow through the gas flow groove is orthogonal to the gas flow groove. A phosphoric acid fuel cell, wherein the phosphoric acid fuel cell is formed by a gas communication groove and a straight gas communication groove arranged in a direction orthogonal to the gas communication groove so as to be commutated to. 2. The phosphoric acid fuel cell according to claim 1, wherein the length of the gas flow groove defined by the gas communication groove in the flow direction becomes shorter from the gas inlet side toward the gas outlet side. A phosphoric acid fuel cell characterized by being formed as described above. 3. A flat plate-shaped oxidant electrode formed by a oxidant electrode base material and a oxidant electrode catalyst layer made of hydrophilic porous carbon paper, and having a flat plate-shaped matrix supporting phosphoric acid as an electrolyte. , A gas electrode that is sandwiched between a fuel electrode base material made of hydrophilic porous carbon paper and a fuel electrode catalyst layer formed of a fuel electrode catalyst layer, and has an oxidant gas flow to both main surfaces thereof. In a phosphoric acid fuel cell including a unit cell formed by arranging a porous oxidizer electrode carbon plate having a passage and a porous fuel electrode carbon plate having a gas flow passage through which a fuel gas flows , At least one of the oxidizer electrode base material and the fuel electrode base material, or the oxidizer electrode carbon plate and the fuel electrode carbon plate are linearly water repellent in a direction orthogonal to the gas flow direction. Characterized by comprising a section Phosphoric acid fuel cell. 4. The phosphoric acid fuel cell according to claim 3, wherein the interval between the linear water repellent treatment parts to be installed is formed so as to become shorter from the gas inlet side toward the gas outlet side. And a phosphoric acid fuel cell.