JPH08306370A - Laminated phosphoric acid type fuel cell - Google Patents

Abstract

PURPOSE: To avoid the generation of damage in a unit cell by supply of phosphoric acid, and prevent damage to a discharge gas system by phosphoric acid by eliminating need of supplying phosphoric acid for a long period. CONSTITUTION: A first cooling medium flow tube 21 disposed to face a reaction part of a unit cell, and a second cooling medium flow tube 21 disposed to face a discharge part of oxidizer gas in the unit cell are embedded between a pair of cooling base plates 20 for composing a cooling plate. Temperature of cooling medium in the second cooling medium flow tube 22 is set to be lower than temperature of cooling medium in the first cooling medium flow tube 21, temperature at the oxidizer gas discharge part of the unit cell is decreased, and vaporized phosphoric acid is condensed to be collected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stacked phosphoric acid fuel cell formed by stacking single cells having phosphoric acid as an electrolyte to form a semi-block, and then alternately stacking them with cooling plates.

[0002]

2. Description of the Related Art FIG. 2 is an exploded perspective view showing a simplified general structure of a conventional stacked phosphoric acid fuel cell. As shown in the figure, in a conventional stacked phosphoric acid fuel cell, a fuel having an electrolyte matrix 1 carrying phosphoric acid, a fuel catalyst layer 3 on one surface and a fuel gas flow groove 4 on the other surface is used. A single cell 8 formed by being sandwiched between an electrode 2 and an oxidant electrode 5 having an oxidant catalyst layer 6 on one surface and an oxidant gas flow groove 7 on the other surface is laminated with a separator 9 interposed therebetween. By doing so, a semi-block is formed, and the refrigerant flow pipe 1
A fuel cell stack is constructed by alternately stacking the cooling plates 10 in which 1 is embedded. When the fuel gas and the oxidant gas are supplied to the laminated phosphoric acid fuel cell configured as described above and flowed through the fuel gas flow groove 4 and the oxidant gas flow groove 7, respectively, the electrochemical reaction is performed in the single cell 8. A reaction occurs and DC power is obtained, and the heat generated by the reaction is removed by the cooling plate 10.

FIG. 3 is a plan view schematically showing the structure of the conventional cooling plate 10 described above. The cooling plate 10 is configured by embedding a plurality of refrigerant flow pipes 11, one end of which is connected to the refrigerant supply header 12 and the other end of which is connected to the refrigerant discharge header 13, between a set of cooling substrates 14. ing. The refrigerant sent to the refrigerant supply header 12 branches and flows through the plurality of refrigerant flow pipes 11, and is collected and discharged in the refrigerant discharge header 13.

[0004]

When the laminated phosphoric acid fuel cell is put to practical use, it will be used for a long period of 40,000 hours or more. In the conventional configuration, the phosphoric acid carried on the electrolyte matrix 1 is vaporized and scattered during the power generation operation, and is discharged together with the fuel gas or the oxidant gas. Therefore, the phosphoric acid amount is insufficient by 40,000 hours. However, in order to compensate for this, a method of periodically replenishing phosphoric acid from the outside is adopted.

However, since the amount of phosphoric acid that evaporates and scatters depends on the operating temperature and the gas flow rate and differs for each single cell, it is substantially difficult to replenish each single cell with an appropriate amount of phosphoric acid. is there. For this reason, the supply amount of phosphoric acid becomes excessive, and the phosphoric acid overflows into the fuel gas passage groove 4 or the oxidant gas passage groove 7 to hinder the proper passage of the reaction gas. There is a risk of causing fatal damage to the unit cell due to a situation such as a shortage of the replenishment amount, a reaction gas permeation between the fuel electrode 2 and the oxidizer electrode 5, and a reaction occurs inside the electrode. is there.

Further, the vaporized phosphoric acid may be aggregated and adhered to auxiliary pipes such as exhaust pipes for fuel gas or oxidant gas or heat exchangers, which may corrode and damage them to cause troubles. . The present invention has been made in consideration of the above problems, and an object thereof is to avoid damage to a single cell due to replenishment of phosphoric acid for a long period of time as unnecessary, and to exhaust gas due to phosphoric acid. An object of the present invention is to provide a laminated phosphoric acid fuel cell with less damage to the system.

[0007]

In order to achieve the above object, in the present invention, phosphoric acid is provided between a fuel electrode having a fuel gas passage groove and an oxidant electrode having an oxidant gas passage groove. To form a semi-block by stacking a plurality of single cells sandwiching an electrolyte layer carrying the semi-block, and alternately laminating the semi-block and a cooling plate in which a refrigerant flow pipe is embedded in a rectangular cooling substrate. In the laminated phosphoric acid fuel cell to be formed, the refrigerant flow pipe of the cooling plate and the refrigerant flow pipe of the first cooling system arranged facing the cell reaction part of the semi-block, and the fuel gas of the semi-block And a temperature lower than the temperature of the refrigerant flowing through the refrigerant flow pipe of the first cooling system, and the refrigerant flow pipe of the second cooling system arranged facing the discharge portion of the oxidant gas. It is assumed that the refrigerant having the temperature is made to flow through the refrigerant flow pipe of the second cooling system.

[0008]

As described above, in the first cooling system in which the refrigerant flow pipe embedded in the cooling plate faces the battery reaction section of the semi-block and the discharge section of the fuel gas and the oxidant gas of the semi-block. It is divided into a second cooling system that is arranged facing
If the temperature of the refrigerant flowing in the cooling system of 1 is lower than the temperature of the refrigerant flowing in the first cooling system, the temperature of the gas outlet of each unit cell will be Will be lower than. Therefore, when the phosphoric acid evaporated in the gas inlet part having a relatively high temperature and the cell reaction part reaches the gas outlet part having a relatively low temperature together with the reaction gas, most of them aggregate to form the fuel electrode or the oxidizer electrode. It is collected on the constituent base material and the like, and is supplied to the catalyst layer and the electrolyte layer of each electrode through the gas flow grooves of the base material. That is, with this configuration, the evaporated phosphoric acid is recirculated to the catalyst layer and the electrolyte layer of each electrode again, so that the decrease in the phosphoric acid amount due to the power generation operation is significantly suppressed, and the phosphoric acid is replenished even during long-term operation. There is no need. Also, since the amount of phosphoric acid that evaporates and reaches the reaction gas discharge system is greatly reduced,
Damage to equipment in the exhaust gas system is also suppressed.

[0009]

EXAMPLE FIG. 1 is a schematic view of the basic constitution of a cooling plate showing an example of the laminated phosphoric acid fuel cell of the present invention. This cooling plate has a first refrigerant flow pipe 21 arranged facing the battery reaction part of the semi-block and a second refrigerant flow pipe 22 arranged facing the discharge part of the oxidizing gas of the semi-block. , A set of cooling substrates 2
It is configured to be embedded between 0 and the first refrigerant flow pipe 21.
Is 185 ° C., and the second refrigerant flow pipe 22 is 1
Refrigerant at 50 ° C is being sent. In this configuration, since the temperature of the oxidant gas discharge part is set lower than that of the single cell battery reaction part, the phosphoric acid evaporated to the oxidant gas in the battery reaction part aggregates at the discharge part and becomes the oxidizer. Collected on the base material of the pole,
Reflux to the catalyst layer and the electrolyte layer. Therefore, the decrease in the amount of phosphoric acid is significantly suppressed, and the amount of phosphoric acid that reaches the exhaust system of the reaction gas by evaporation is also significantly reduced.

In the present embodiment, the low temperature refrigerant is supplied to the second refrigerant flow pipe 22 arranged facing the discharge portion of the semi-block oxidant gas. A low-temperature refrigerant may be supplied to the refrigerant flow pipe arranged facing the discharge part of the refrigerant, and the refrigerant flow pipe arranged so as to face both the oxidant gas discharge part and the fuel gas discharge part. The same effect can be obtained by supplying a low temperature refrigerant to the flow tube.

[0011]

As described above, according to the present invention, an electrolyte layer carrying phosphoric acid is sandwiched between a fuel electrode having a fuel gas flow groove and an oxidant electrode having an oxidant gas flow groove. A laminated phosphoric acid type formed by stacking a plurality of single cells formed by forming a semi-block and alternately stacking the semi-block and a cooling plate in which a refrigerant flow pipe is embedded in a rectangular cooling substrate. In the fuel cell, the coolant flow pipe of the cooling plate is arranged so as to face the cell reaction part of the semi-block, and the coolant flow pipe of the first cooling system and the discharge part of the fuel gas and the oxidant gas of the semi-block. And a refrigerant having a temperature lower than the temperature of the refrigerant flowing through the refrigerant flow pipe of the first cooling system. Since it was decided to let the refrigerant flow through the refrigerant flow pipe of the cooling system, the phosphoric acid evaporated in the battery reaction section would become gas. Most of the particles agglomerate at the mouth and are collected on the base material that constitutes the fuel electrode or oxidizer electrode, and then flow back to the catalyst layer and electrolyte layer of each electrode, which damages the single cell even during long-term operation. Therefore, it is possible to obtain a laminated phosphoric acid fuel cell that does not require the supplementation of phosphoric acid that easily causes the above-mentioned phenomenon and has less damage to the exhaust gas system.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a basic configuration of a cooling plate showing an embodiment of a laminated phosphoric acid fuel cell of the present invention.

FIG. 2 is an exploded perspective view showing a simplified general structure of a conventional stacked phosphoric acid fuel cell.

FIG. 3 is a plan view schematically showing the structure of a cooling plate of a conventional laminated phosphoric acid fuel cell.

[Explanation of symbols]

 1 Electrolyte Matrix 2 Fuel Electrode 5 Oxidizer Electrode 8 Single Cell 9 Separator 10 Cooling Plate 11 Refrigerant Flow Pipe 12 Refrigerant Supply Header 13 Refrigerant Discharge Header 14 Cooling Substrate 20 Cooling Substrate 21 First Refrigerant Flowing Pipe 22 Second Refrigerant Flow pipe

Claims (1)

[Claims] 1. A plurality of single cells laminated by sandwiching an electrolyte layer carrying phosphoric acid between a fuel electrode having a fuel gas flow groove and an oxidant electrode having an oxidant gas flow groove. In a laminated phosphoric acid fuel cell in which semi-blocks are formed and cooling plates formed by embedding a refrigerant flow pipe in a rectangular cooling substrate are alternately laminated, a cooling medium for the cooling plates is passed through. A flow pipe has a refrigerant flow pipe of the first cooling system, which faces the battery reaction part of the semi-block, and a second flow pipe, which faces the discharge part of the fuel gas and the oxidant gas of the semi-block. And a refrigerant having a lower temperature than the refrigerant flowing through the refrigerant flow pipe of the first cooling system and flowing through the refrigerant flow pipe of the second cooling system. And a laminated phosphoric acid fuel cell.