JPH09223505A - Phosphoric acid type fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphoric, acid type fuel cell by which the local gas concentration of a prescribed position of a fuel cell laminated body can be measured and which has a cooling plate having no possibility of corrosion by phosphoric acid and by which the scattered phosphoric acid can be automatically recovered and which can be stably used over a long period of time. SOLUTION: A joining body of cooling pipes 5A arranged in parallel to each other and header pipes 6A joined to its both ends by adjusting upper surfaces, is embedded in a cooling base board 4A, and a cooling plate 3A whose upper surface is smooth and in which embedded parts of the header pipes 6A project downward, is constituted, and through holes 9A in which tubes to gather gas in a fuel cell laminated body are arranged in side surfaces of the embedded parts of the header pipes 6A, and the embedded parts of the header pipes 6A are incorporated so as to project from side surfaces of the fuel cell laminated body. Carbon porous plates 7A are arranged on upper surfaces of the embedded parts of the header pipes 6A, and carbon fiber 8A is incorporated between them and a reservoir plate of lower unit cells.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a cooling plate used by being incorporated in a fuel cell stack of a phosphoric acid fuel cell, and in particular, it enables measurement of in-plane gas concentration distribution, and scattered phosphoric acid. Related to the structure that enables repair of

[0002]

2. Description of the Related Art FIG. 5 is an exploded perspective view schematically showing a basic structure of a fuel cell stack of a phosphoric acid fuel cell which has been conventionally used. The matrix 11 carrying the phosphoric acid of the electrolyte is sandwiched between the fuel electrode composed of the fuel electrode catalyst layer 12 and the fuel electrode base material 14, and the air electrode composed of the air electrode catalyst layer 13 and the air electrode base material 15, and further replenished. The unit cell 1 is configured by stacking reservoir plates 16 that hold phosphoric acid for use in the process. Each of the fuel electrode base material 14 and the air electrode base material 15 has a ribbed structure, and the fuel gas and the air flow into the formed grooves, respectively. The fuel cell stack 2 is configured by stacking the single cells 1 thus configured with the separator 10 interposed therebetween, and inserting the cooling plate 3 every time several layers are stacked.

The cooling plate 3 has a set of header pipes 6 at both ends.
The plurality of metal cooling pipes 5 connected in parallel and connected to each other are connected to the fuel electrode base material 14, the air electrode base material 15, the reservoir plate 16 and the separator 10 and are made of carbon. It is embedded and configured inside. During steady operation of the phosphoric acid fuel cell, a coolant such as cooling water is passed through the cooling pipe 5 from the outside to be used for removing heat generated by power generation.
It is used to raise the temperature to the start-up temperature by passing hot water through it. Since the refrigerant or the hot water flowing through the plurality of cooling pipes 5 collectively flows through the header pipe 6, the cross-sectional area of the flow path is made larger than that of the cooling pipe 5 to reduce the pressure loss.

FIG. 6 is a perspective view showing the structure of a fuel cell body incorporating the above-mentioned fuel cell stack, with a part thereof exploded. As shown in the figure, the fuel cell stack is formed by inserting the cooling substrate 4 in which the cooling pipes 5 having the header pipes 6 connected to both ends are inserted every time a plurality of unit cells are stacked. The collector plates 24 are arranged on both ends of 2 ,
Further, a tightening plate is arranged and pressed and held by a tightening bolt. An inlet-side manifold 21 and an outlet-side manifold 22 are installed on the side surfaces of the fuel cell stack 2 so as to face each other. The fuel gas supplied from one of the inlet side manifolds 21 is distributed to the gas flow grooves of the fuel electrode and flows therethrough, and then collected in the outlet side manifolds 22 on the opposite side faces, to the outside through the outlet connecting pipe 23. Is discharged. Further, the air supplied from the other inlet side manifold 21 is distributed through the gas flow grooves of the air electrode and flows therethrough, and the outlet side manifold 2 on the opposite side surface.
After being collected in 2, it is discharged to the outside through the outlet connecting pipe 23.

A gas sampling port 25 is provided in each of the two outlet connection pipes 23, and a sample gas for measuring the concentration of the fuel gas consumed in the fuel electrode or the air consumed in the air electrode. Used to collect.

[0006]

As described above, in the conventional phosphoric acid fuel cell, the sample gas is sampled and measured using the gas sampling port 25 provided in the outlet connecting pipe 23, and the fuel cell stack is prepared. The method of evaluating the consumption state of fuel gas and air in the body 2 or the leakage state of gas between both electrodes is adopted, and a cooling plate 3 incorporated in the fuel cell stack 2 is provided with a metal header at both ends. The metal cooling pipe 5 connected to the pipe 6 is embedded in the carbon cooling substrate 4.

However, in the above-mentioned sample gas sampling method, since the gas that flows through the fuel cell stack 2 and is discharged collectively is evaluated, the average behavior of the entire fuel cell stack 2 is evaluated. It will be evaluated. Therefore,
There is a drawback that the detailed behavior of each single cell or a group of single cells between each cooling plate cannot be evaluated, and even if a local defect occurs, it cannot be detected.

Further, in the structure of the cooling plate 3 as described above, the cooling pipe 5 and the header pipe 6 exposed from the cooling substrate 4 are arranged in the inlet side manifold 21 or the outlet side manifold 22, so that an electrochemical reaction occurs. A phenomenon occurs in which phosphoric acid that has evaporated and scattered along with the generated water is cooled and condensed in the outlet side manifold 22 and adheres to the cooling pipe 5 or the header pipe 6. Since these pipes are formed of metal pipes having good thermal conductivity, if phosphoric acid adheres to them, they will be corroded and eroded to cause leakage of cooling water. Therefore, in order to prevent this, a method of coating the metal pipe exposed from the cooling substrate 4 with a fluororesin is generally used, but since the coating is a thin film, pinholes and peeling due to friction occur. It is easy and may cause local corrosion of the metal pipe.

As a method for avoiding such corrosion due to phosphoric acid, there is a method in which the cooling pipe and the header pipe are all embedded in the cooling substrate. In this method, it is necessary to embed a header pipe made of a thick metal tube so as to avoid an increase in the thickness of the cooling substrates in the stacking direction. FIG. 7 shows a Japanese Patent Application No. 7-1
FIG. 9 is a basic configuration diagram of a cooling plate of a fuel cell stack of a phosphoric acid fuel cell disclosed in Japanese Patent No. 91387, (a) is a perspective view showing connections of internal pipes, and (b) is a stack with unit cells. It is a perspective view which expands and shows the principal part of a cooling plate. As shown in Fig. 7 (a), the header pipe 6A is formed of a metal pipe having a rectangular cross section, and the upper surface is aligned with the side surface of the header pipe 6A.
Are joined. The header pipe 6A is selected as having a flow passage cross-sectional area larger than that of the cooling pipe 5A so as to suppress the pressure loss to a predetermined value or less. The cooling plate 3A formed by embedding the joined body of the cooling pipe 5A and the header pipe 6A in the cooling substrate 4A is formed such that the thickness of the portion where the cooling pipe 5A is embedded is smaller than the thickness of the portion where the header pipe 6A is embedded. Further, the upper surface is made smooth and the portion in which the header pipe 6A is embedded is formed so as to project downward. Therefore, as shown in FIG. 7 (b), the thickness in the stacking direction of the fuel cell stack formed by alternately stacking the plurality of unit cells 1 is equal to the fuel cell stack using the cooling plate 3 of FIG. It is suppressed to the same level as. In the structure shown in FIG. 7 (a), a carbon porous plate 7A having hydrophilicity to phosphoric acid is arranged on the upper surface of the portion of the cooling plate 3A in which the header pipe 6A is embedded, Further, the carbon porous plate 7A and a group of unit cells below the porous plate 7A adjacent to the porous carbon plate 7A
1 , a cooling substrate 4
A carbon fiber 8A having hydrophilicity with respect to phosphoric acid is disposed so as to penetrate the communication hole provided in A. Therefore, the phosphoric acid evaporated and scattered and released from the fuel cell stack adheres to the carbon porous plate 7A and is returned to the single cell 1 through the carbon fiber 8A. You will be able to drive without replenishing.

Therefore, if the cooling plate 3A as shown in FIG. 7 is used, there is no fear of corrosion damage to the metal tube due to phosphoric acid as in the configuration example of FIG. 5, and operation can be performed for a long time without replenishing phosphoric acid. Become. However, even in this configuration, since the gas discharged through the fuel cell stack in a batch is collected and the average behavior of the entire body is evaluated, it is necessary to evaluate the average behavior of each unit cell or each cooling plate. Even if a small behavior such as a single cell group cannot be evaluated and a local malfunction occurs,
The problem is that it cannot detect it.

The present invention has been made in consideration of the problems of the prior art as described above, and an object thereof is to enable local measurement of gas concentration at a predetermined position of a fuel cell stack and to measure phosphorus content. Another object of the present invention is to provide a phosphoric acid fuel cell that includes a cooling plate that is free from the risk of acid corrosion, and that scatters phosphoric acid automatically, so that it can be used stably for a long period of time.

[0012]

In order to achieve the above object, in the present invention, (1) a single cell that holds phosphoric acid in a matrix is laminated,
In a phosphoric acid fuel cell using a fuel cell stack formed by inserting a cooling plate, the cooling plate is composed of a plurality of cooling pipes arranged in parallel and a set of header pipes connected to both ends of the cooling pipe. The cooling substrate made of a material is embedded inside, and the thickness of the portion where the cooling pipe is embedded is thinner than the thickness of the portion where the header pipe is embedded. The portion where the header pipe is embedded is the side surface of the fuel cell stack. At least one of the above cooling plates has a through hole for airtightly arranging a tube for collecting gas in the fuel cell stack in at least one of the cooling plates in which the header pipe is embedded. It shall be equipped with at least one.

(2) Further, the cooling plate of the phosphoric acid fuel cell of the above (1) is formed so that the upper surface is smooth and the portion in which the header pipe is embedded projects downward, and the header pipe of the cooling plate is formed. A porous carbon plate hydrophilic to phosphoric acid is placed on the upper surface of the embedded part, and a carbon hydrophilic plate to the phosphoric acid is placed between the porous carbon plate and the lower unit cell group in the vicinity. The fibers will be arranged.

(3) Alternatively, the cooling plate of the phosphoric acid fuel cell according to the above (1) is formed so that the lower surface is smooth and the portion where the header pipe is embedded protrudes upward, and the header pipe of the cooling plate is formed. A porous carbon plate hydrophilic to phosphoric acid is placed on the upper surface of the embedded cooling pipe adjacent to the embedded part, and between this carbon porous plate and the lower unit cell group adjacent to it. Carbon fibers hydrophilic to phosphoric acid are to be arranged.

(4) Furthermore, the phosphoric acid having the cooling plate according to the above (2) or (3), wherein the single cell of the fuel cell stack has a reservoir plate made of a porous carbon material for replenishing phosphoric acid. In the type fuel cell, the connection position of the carbon fiber with the single cell group is on the side surface of the reservoir plate. According to the above (1), since the metal cooling pipe and the header pipe are embedded inside the cooling substrate made of the carbon material, corrosion due to phosphoric acid is avoided. Further, since the portion of the cooling substrate in which the header pipe is embedded is arranged so as to project to the side surface of the fuel cell stack, and the thickness of the portion in which the cooling pipe is embedded is formed thin, the thickness in the stacking direction of the fuel cell stack Is suppressed to an appropriate amount. Furthermore,
By locally arranging the tube through the through hole provided in the cooling substrate in the portion where the header pipe is embedded and collecting the gas of the fuel cell stack, the local distribution of gas concentration can be measured.

Further, according to the above (2) or (3), phosphoric acid which is evaporated and scattered during the power generation operation and released to the outside of the fuel cell stack adheres to the carbon porous plate, Since it is condensed and sent to the lower unit cell through the carbon fiber, phosphoric acid is circulated, collected and used, and can be used stably for a long period of time. Further, in the case of the above (4), the phosphoric acid adhered to and condensed on the carbon porous plate is accurately sent to the single cell.

[0017]

FIG. 1 is a basic configuration diagram of a cooling plate showing a first embodiment of a phosphoric acid fuel cell of the present invention, (a) is a perspective view showing the connection of internal pipes, FIG. 3B is an enlarged perspective view showing a main part of a cooling plate laminated with a single cell. In the structure of the present embodiment, as in the conventional cooling plate shown in FIG. 7, the upper surface is aligned with the side surface of the header pipe 6A formed of a metal pipe having a rectangular cross section with a relatively large flow passage cross-sectional area. The cooling pipe 5A is joined together and embedded in the cooling substrate 4A to form the cooling plate 3A . Therefore, corrosion of the cooling pipe 5A and the header pipe 6A due to phosphoric acid is avoided. Further, the thickness of the portion of the cooling plate 3A in which the cooling pipe 5A is embedded is made smaller than the thickness of the portion in which the header pipe 6A is embedded, and the upper surface is made smooth so that the portion in which the header pipe 6A is embedded protrudes downward. ing. Therefore, the thickness in the stacking direction of the fuel cell stack formed by alternately stacking the plurality of unit cells 1 is suppressed to an appropriate amount. As shown in FIG. 1 (a), like the conventional example of FIG. 7, a carbon porous plate 7A having hydrophilicity to phosphoric acid is formed on the upper surface of the portion of the cooling plate 3A in which the header pipe 6A is embedded. Further, the carbon porous plate 7A and the reservoir plate (not shown) of the lower group of single cells 1 adjacent to the carbon porous plate 7A penetrate through the communication holes provided in the cooling substrate 4A. A carbon fiber 8A having hydrophilicity to phosphoric acid is provided. Therefore, about 2
The phosphoric acid evaporated and scattered inside the unit cell 1 at 00 ° C and released from the side surface of the fuel cell stack exchanges heat with the protruding portion of the cooling plate 3A cooled with cooling water at 160 to 170 ° C. It is cooled by cooling, condensed and held by the carbon porous plate 7A, and further sent through the carbon fiber 8A to the reservoir plate of the single cell 1 for recovery. FIG. 4 is a characteristic diagram showing the ratio of the phosphoric acid evaporated and scattered at a predetermined temperature to be condensed and trapped by cooling. As can be seen from the characteristic curve indicated by A in the figure, the phosphoric acid evaporated and scattered from the single cell 1 at 200 ° C condenses almost 90% when it sufficiently exchanges heat with the protruding part of the cooling plate 3A at 170 ° C. Will be done. Therefore, it can be operated for a long period of time without replenishing phosphoric acid.

The difference from the conventional example of FIG. 7 of the structure of this embodiment, among the cooling plate 3A to be inserted into the fuel cell stack, the cooling plates 3A disposed in a predetermined position, buried header pipe 6A The part is connected to a tube for collecting the gas of each part of the fuel cell stack to measure the local gas concentration,
It is provided with a through hole 9A which is airtightly arranged. The through hole 9A is arranged on the cooling substrate 4A of the cooling plate 3A while avoiding the embedded portions of the cooling pipe 5A and the header pipe 6A, and can collect local gas discharged from the stack end surface of the fuel cell stack. Is led to. Therefore, a local gas concentration can be measured by connecting a gas sampling tube to the through hole and taking it out to the outside.

FIG. 2 is a schematic diagram showing the basic structure of a fuel cell body incorporating the fuel cell stack having the cooling plate of the structure shown in FIG. 1 and the basic structure of the gas concentration measuring apparatus for the fuel cell stack. . Current collector plates 24 are arranged at both ends of a fuel cell stack 2 formed by incorporating a cooling plate 3A having a gas sampling tube 30 inserted into a through hole, and further tightening plates are arranged and pressed and held by tightening bolts. Has been done. An inlet-side manifold 21 and an outlet-side manifold 22 are installed on the side surface of the fuel cell stack 2 so as to face each other, and are supplied from the inlet-side manifold 21, and are supplied from the inlet-side manifold 21 and are connected to the gas passage groove of the fuel electrode or the gas of the air electrode. The fuel gas and the air that have been distributed and flowed through the flow channels are collected in the outlet side manifold 22 on the opposite side surfaces, and then discharged to the outside through the outlet connection pipe 23. The other end of the gas sampling tube 30 inserted into the through hole of the cooling plate 3A is connected to a gas flow path switching device 31 arranged outside through a port provided in the outlet side manifold 22, and the gas flow path switching is performed. Bowl 3
The local gas discharged from the stacking end surface of the fuel cell stack at the position communicating with the gas sampling tube 30 selected in 1 is sucked by the pump 32 and sent to the gas concentration analyzer 33 for concentration analysis. It Therefore, in the phosphoric acid fuel cell of this configuration, unlike the conventional configuration shown in FIG. 6, it is possible to sample the local gas in each part of the fuel cell stack and measure its concentration. If a local defect occurs inside the battery stack, the defect can be easily detected by the change in the concentration distribution.

FIG. 3 shows a second embodiment of the phosphoric acid fuel cell of the present invention.
FIG. 1 is a basic configuration diagram of a cooling plate showing an embodiment of the present invention, (a) is a perspective view showing the connection of internal pipes, (b) is an enlarged perspective view showing a main part of a cooling plate laminated with a single cell. is there. In the configuration of the present embodiment, the cooling pipe 5B is joined by aligning the lower surface with the side surface of the header pipe 6B having a relatively large flow passage cross-sectional area, and embedded in the cooling substrate 4B to form the cooling plate 3B. There is. Therefore, corrosion of the cooling pipe 5B and the header pipe 6B due to phosphoric acid is avoided. Further, the thickness of the portion in which the cooling pipe 5B is embedded is made smaller than the thickness of the portion in which the header pipe 6B is embedded, the lower surface is made smooth, and the portion in which the header pipe 6B is embedded protrudes upward. Further, as shown in FIG. 3 (a), a carbon porous plate 7B having hydrophilicity to phosphoric acid is disposed on the upper surface of the portion where the cooling pipe 5B is embedded and which is close to the portion where the header pipe 6B is embedded. Further, the carbon porous plate 7B and a group of unit cells 1 below the carbon porous plate 7B are provided.
The cooling plate 4B between the reservoir plate and the reservoir plate (not shown).
A carbon fiber 8B having a hydrophilic property with respect to phosphoric acid is disposed so as to penetrate the communication hole provided in. Therefore, the phosphoric acid evaporated and scattered inside the unit cell 1 and released from the side surface of the fuel cell stack is cooled by exchanging heat with the projecting portion of the cooling plate 3B and condensed to form the carbon porous plate 7B. It is held and further sent to the reservoir plate of the single cell 1 through the carbon fiber 8B and collected. Therefore,
It can be operated for a long period of time without replenishing phosphoric acid. Furthermore, in this configuration, among the cooling plates 3B to be inserted into the fuel cell stack, the cooling plate arranged at a predetermined position.
A portion for burying the header pipe 6B of 3B is provided with a through hole 9B for connecting a tube for collecting gas from each part of the fuel cell stack to measure a local gas concentration and for airtightly arranging the tube. ing. Therefore, by incorporating a gas concentration measuring device for a fuel cell stack having a basic structure as shown in FIG. 2, collecting local gas in each part of the fuel cell stack, and measuring the concentration, the fuel cell is measured. It is possible to easily detect a local defect that occurs inside the laminated body.

[0021]

As described above, according to the present invention, (1) stacking single cells holding phosphoric acid in a matrix,
In the phosphoric acid fuel cell using the fuel cell stack formed by inserting the cooling plate, since the cooling plate is configured as described in claim 1, the cooling plate is installed at a predetermined position inside the fuel cell stack. It is possible to measure the local gas concentration, and
A phosphoric acid fuel cell provided with a cooling plate that is free from the risk of corrosion by phosphoric acid can be obtained.

(2) Further, if the cooling plate of the phosphoric acid fuel cell is constructed as described in claim 2 or claim 3, further scattered phosphoric acid is automatically recovered and stable for a long period of time. Thus, a phosphoric acid type fuel cell that can be used after that is obtained. (3) Furthermore, with the construction as described in claim 4, since the scattered phosphoric acid is more accurately and automatically recovered, the phosphoric acid fuel cell can be stably used for a long period of time. Is suitable

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a cooling plate showing a first embodiment of a phosphoric acid fuel cell of the present invention, (a) is a perspective view showing the connection of internal pipes, (b) is a single cell and laminated The perspective view which expands and shows the principal part of the cooled cooling plate.

FIG. 2 is a schematic diagram showing a basic configuration of a fuel cell body incorporating the fuel cell stack including the cooling plate of the first embodiment of FIG. 1 and a basic configuration of a gas concentration measuring device for the fuel cell stack.

FIG. 3 is a basic configuration diagram of a cooling plate showing a second embodiment of the phosphoric acid fuel cell of the present invention, (a) is a perspective view showing the connection of internal pipes, (b) is a single cell and laminated The perspective view which expands and shows the principal part of the cooled cooling plate.

FIG. 4 is a characteristic diagram showing a ratio of evaporated and scattered phosphoric acid condensed and trapped by cooling.

FIG. 5 is an exploded perspective view schematically showing the basic structure of a fuel cell stack of a phosphoric acid fuel cell that has been conventionally used.

FIG. 6 is a perspective view showing a basic structure of a fuel cell body incorporating a fuel cell stack as shown in FIG.

FIG. 7 is a basic configuration diagram of another example of the cooling plate of the conventional phosphoric acid fuel cell, (a) is a perspective view showing the connection of internal pipes,
(b) is an enlarged perspective view showing the main part of the cooling plate laminated with the single cell

[Description of Reference Signs] 1 single cell 2 fuel cell stack 3 cooling plate 3A , 3B cooling plate 4 cooling substrate 4A, 4B cooling substrate 5 cooling pipe 5A, 5B cooling pipe 6 header pipe 6A, 6B header pipe 7A, 7B carbon porous Quality plate 8A, 8B Carbon fiber 9A, 9B Through hole 10 Separator 16 Reservoir plate 21 Inlet side manifold 22 Outlet side manifold 23 Outlet connection pipe 24 Current collector plate 25 Gas sampling port 30 Gas sampling tube 31 Gas flow path switch 32 Pump 33 Gas concentration analyzer

Claims (4)

[Claims] 1. A phosphoric acid fuel cell using a fuel cell stack, which is formed by stacking single cells holding phosphoric acid in a matrix and inserting a cooling plate, wherein a plurality of cooling plates are arranged in parallel. Cooling pipe and a set of header pipes connected to both ends of the cooling pipe are embedded inside a cooling board made of a carbon material, and the thickness of the portion where the cooling pipe is embedded is the thickness of the portion where the header pipe is embedded. In a structure in which the portion where the header pipe is embedded is arranged so as to project to the side surface of the fuel cell stack, the cooling plate has at least one of the above cooling plates, and the fuel cell stack is formed on the cooling substrate where the header pipe is embedded. A phosphoric acid fuel cell, comprising at least one through hole for hermetically disposing a tube for collecting gas in the body. 2. The phosphoric acid fuel cell according to claim 1, wherein the cooling plate is formed so that the upper surface is smooth and the portion where the header pipe is embedded projects downward, and the header pipe of the cooling plate is embedded. A carbon porous plate hydrophilic to phosphoric acid is arranged on the upper surface of the exposed portion, and a carbon fiber hydrophilic to phosphoric acid is provided between the carbon porous plate and the unit cell group in the lower part adjacent to the carbon porous plate. A phosphoric acid fuel cell, characterized in that: 3. The phosphoric acid fuel cell according to claim 1, wherein the cooling plate is formed so that the lower surface is smooth and the portion where the header pipe is embedded protrudes upward, and the header pipe of the cooling plate is embedded. The porous carbon plate hydrophilic to phosphoric acid is placed on the upper surface of the part where the cooling pipe adjacent to the above-mentioned part is embedded. A phosphoric acid fuel cell, in which carbon fibers hydrophilic to an acid are arranged. 4. The phosphoric acid fuel cell according to claim 2 or 3, wherein a single cell of the fuel cell stack comprises a reservoir plate made of a porous carbon material for replenishing phosphoric acid. A phosphoric acid fuel cell, characterized in that the connection position with an adjacent unit cell group is a side surface of the reservoir plate.