JPH0620714A - Fuel cell and electrolyte impregnation treatment method - Google Patents

Abstract

PURPOSE:To effectively remove the residual organic solvent and binder inside an electrolytic substrate at initial temperature rise of a fuel cell. CONSTITUTION:Branch pipes 22 and 23 are provided in the middles of exhaust pipes 18 and 19 for anode gas 12 and cathode gas 13 of a fuel battery, and gas suction mechanisms 26 and 27 for sucking and exhausting gas are provided through valves. Furthermore, a branch pipe 36 is also provided in the middle of a purge gas exhaust pipe 30, a gas suction mechanism 38 for sucking and exhausting gas is added through a valve 37 so as to increase the influence. So, since it is so arranged as to suck and remove the gas inside the exhaust pipe through exhaust pipes, the residual organic solvent generated from an electrolytic substrate and a binder can be removed. As a result, the deterioration of electrolyte accompanying the abnormal heating by an organic solvent or the drop of the battery capacity by the inequality in impregnation can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell, and more particularly to an internal impregnation type fuel cell in which a substrate, which is an electrolyte carrier, is impregnated with an electrolyte at the initial temperature rise of the cell.

[0002]

2. Description of the Related Art As an operating system of a fuel cell, for example, "Energy" Vol. 24, No. 4 (1990), p. 30, FIG. 4, "MW-class MCFC power plant" is known. . According to this example, the anode exhaust gas and the cathode exhaust gas discharged from the fuel cell main body are finally discharged to the outside of the fuel cell power generation system via the steam separator and the turbine, respectively.

In general, a fuel cell has an electrolyte plate impregnated with an electrolyte, and an air-permeable anode electrode and a cathode electrode disposed between them. Anode gas and cathode gas passages are provided outside each of these electrodes. Formed by arranging a separator. A plurality of unit fuel cells thus formed are usually stacked to form a fuel cell stack for use. At the periphery of the fuel cell stack, a manifold for supplying each fuel cell with anode gas and cathode gas supplied from the outside through the lower header, and gas that has passed through the anode gas passage and the cathode gas passage A respective manifold for discharge is provided.
The anode exhaust gas and the cathode exhaust gas are exhausted to the anode gas exhaust pipe and the cathode gas exhaust pipe, respectively, through the respective manifolds and the lower header. The fuel cell stack is used by being housed in a container equipped with a purge gas replenishment mechanism.

By the way, as a method of impregnating an electrolyte plate with an electrolyte, there is known a so-called internal impregnation type which is performed after a fuel cell is assembled. In the case of the internal impregnation type, a fuel cell stack is assembled by using a ceramic-based substrate mixed with a binder and coating a carbonate as an electrolyte on the substrate. Then, the binder is evaporated at the initial stage of temperature rise of the battery, and the voids thus formed are impregnated with carbonate. Therefore, as the binder, a material that melts and evaporates up to about 500 ° C. at which the carbonate melts is used. The initial temperature rise of the battery is performed by heating it to 650 ° C., which is the operating temperature of the battery, by a heater provided in the container.

Here, if the removal of the binder is insufficient, the impregnation of the electrolyte becomes non-uniform and the performance of the battery deteriorates. In addition, the organic solvent used during the formation of the substrate may remain on the substrate even after sintering. If the residual organic solvent is not sufficiently removed, the battery may abnormally generate heat during operation and deteriorate. is there.

However, the removal of the residual organic solvent and the binder is insufficient only by the above-mentioned initial heating, which causes the above-mentioned problems.

Therefore, in order to solve the above problems, an inert gas containing air, carbon dioxide, or the like (hereinafter, referred to as an inert gas or the like) in both lines of the anode gas and the cathode gas at the time of initial temperature rise. The residual organic solvent and the binder are expelled to the exhaust line to be removed. In addition to the normal exhaust line,
Efforts have also been made to squeeze out efficiently by installing a dedicated exhaust line.

[0008]

However, even with the above-mentioned conventional technique, there is a problem that the residual organic solvent and the binder may be insufficiently removed for the reasons described below.

That is, the structure of the unit fuel cell is such that a separator and an electrolyte plate are alternately laminated to form a fuel stack as described above, and each of the anode gas and the cathode gas formed in the separator is formed. The flow path (particularly, the manifold portion provided so as to connect the unit fuel cells to each other) is sealed from the outside by the peripheral portion of the separator and the laminated portion of the electrolyte plate. In other words, it has a sealing structure that expects a so-called wet seal by molten carbonate. Therefore, the sealing effect is not exhibited at the initial temperature rise below about 500 ° C. at which the carbonate melts,
In order to discharge and remove the residual organic solvent and binder, even if an inert gas or the like is fed into the anode gas flow path and the cathode gas flow path during the initial temperature rise of the fuel cell as described above, the inert gas, etc. from the seal part Will be leaked to the outside. Therefore, the flow rate of the inert gas or the like flowing through the anode gas flow path and the cathode gas flow path inside the battery becomes insufficient,
The removal of the residual organic solvent and binder is insufficient.

Further, if the inert gas obtained by mixing the residual organic solvent and the binder leaks from the seal portion in the air supply side manifold portion, the anode gas flow passage portion, the cathode gas flow passage portion, and the exhaust side manifold portion, during normal operation The purge gas will accumulate in the storage container that is full. In this case, in particular, the organic solvent causes abnormal heat generation when the temperature of the fuel cell rises, and causes a problem of deteriorating the fuel cell from the outside of the fuel cell stack.

The first object of the present invention is to effectively remove the organic solvent and the binder remaining in the electrolyte substrate during the initial temperature rise associated with the electrolyte impregnation treatment of the fuel cell, and to reduce the residual rate. It is an attempt to provide a fuel cell that can be extremely low.

A second object of the present invention is to effectively remove the organic solvent and the binder remaining in the electrolyte substrate during the initial temperature rise in the electrolyte impregnation treatment of the fuel cell, and then impregnate the electrolyte. It is intended to provide an electrolyte impregnation treatment method that can be performed.

[0013]

In order to achieve the above-mentioned first object, the first invention of the present invention is to dispose an anode electrode and a cathode electrode with an electrolyte plate sandwiched therebetween, and further to arrange an anode gas in contact with each electrode. In a fuel cell having a unit fuel cell in which a separator provided with a flow passage and a cathode gas flow passage are arranged outside and a supply pipe and an exhaust pipe for the anode gas and the cathode gas are respectively connected to each flow passage, A gas suction mechanism is branched and provided via a valve in each of the exhaust pipes for cathode gas and cathode gas.

Further, when the fuel cell is installed in a storage container, it is preferable that a gas suction mechanism is branched from the purge gas exhaust pipe of the storage container via a valve.

In order to achieve the above-mentioned second object, a second invention of the present invention is to dispose an anode electrode and a cathode electrode with an electrolyte plate sandwiched between them, and an anode gas channel and a cathode gas channel which are in contact with the respective electrodes. An electrolyte impregnation of a fuel cell having a unit fuel cell configured by arranging separators respectively provided on the outside and communicating a supply pipe and an exhaust pipe for anode gas and cathode gas to the respective flow paths. In the processing method,
The gas inside the unit fuel cell is sucked through the branch pipes provided in the exhaust pipes of the anode gas and the cathode gas respectively, and the organic solvent and the binder remaining on the substrate of the electrolyte plate are removed by the gas suction. And then impregnating with an electrolyte.

When the fuel cell is installed in the storage container, in accordance with the above, it is preferable to suck the gas in the storage container through the branch pipe provided in the exhaust pipe of the purge gas of the fuel cell storage container. .

[0017]

According to the present invention, the above objects are achieved by the following operations. According to the first and second aspects of the present invention, in the initial temperature rising process of the fuel cell, an inert gas containing air or carbon dioxide is supplied to the anode gas line and the cathode gas line and the anode gas is supplied. The gas in the fuel cell is forcibly sucked and discharged by a suction mechanism provided by being branched into an exhaust pipe and a cathode gas exhaust pipe. Thereby, the residual organic solvent and the binder vapor generated from the electrolyte plate are effectively sucked and discharged together with the inert gas and the like fed to both the anode gas and cathode gas lines, and the residual amount can be sufficiently reduced. By performing the electrolyte impregnation operation thereafter, the electrolyte can be uniformly impregnated and abnormal heat generation due to the residual organic solvent can be reduced.

Further, when the temperature is lower than the temperature at which the electrolyte melts, the wet sealing effect does not work, so that the organic solvent and the binder leak from the peripheral portion of the fuel cell stack together with the inert gas into the fuel cell container. The organic solvent and the binder are forcibly sucked and discharged together with the purge gas and the leaking inert gas supplied during the impregnation of the electrolyte by the suction mechanism provided branching to the purge gas exhaust pipe.

After the work of discharging and removing the organic solvent and the binder is completed, the valves provided on the upstream side of the suction mechanisms for the anode gas exhaust pipe, the cathode gas exhaust pipe, and the purge gas exhaust pipe are used respectively. The gas suction mechanism is closed, each exhaust valve is opened, and normal exhaust operation is started.

[0020]

Embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a diagram schematically showing the basic structure around the fuel cell of the present invention. The fuel cell stack 2 provided in the fuel cell storage container 1 includes an electrolyte plate 5 having an air permeable anode electrode 3 and a cathode electrode 4 on one side each on the outside, and the anode electrode 3 and the cathode. It is formed by stacking a separator 8 including an anode gas flow channel 6 and a cathode gas flow channel 7 provided in the center of both surfaces so as to be in contact with the electrodes 4, respectively. Then, an upper header 9 and a lower header 10 are arranged at both upper and lower ends of the stack, and a manifold is provided at a peripheral portion 11 of the fuel cell stack 2 so as to communicate with each header. An anode gas air supply pipe 14 and a cathode gas air supply pipe 15 for introducing the anode gas 12 and the cathode gas 13 from the outside into the lower header 10 are provided in the anode gas flow passage 6 and the cathode gas flow passage 7 by the manifold, respectively. It is in communication. Further, another manifold provided in the peripheral portion 11 is arranged so that the anode exhaust gas 16 and the cathode exhaust gas 17 are respectively discharged from the gas flow path to the lower header 10
Through the anode gas exhaust pipe 18 and the cathode gas exhaust pipe 1
It is in communication with 9. Exhaust valves 20 and 21 are provided on the anode gas exhaust pipe 18 and the cathode gas exhaust pipe 19, respectively.
Is attached. Branch pipes 22 and 23 are provided between the exhaust valve and the fuel cell. This is a gas suction mechanism 26 through the forced exhaust valves 24 and 25, respectively.
And 27 are connected so that the gas can be discharged to the outside of the system. The purge gas 28 supplied from a purge gas supply mechanism (not shown) is introduced into the fuel cell storage container 1 through the purge gas supply pipe 29, and the purge gas exhaust pipe 30
Is released to the outside of the system via the exhaust valve 31.

Here, the structure of the fuel cell stack 2 is shown in FIG.
Will be described. From the outside of the fuel cell stack, the laminated structure of the electrolyte plate 5 and the separator 8 can be seen, and the anode gas flow channel 6 can be seen at the top of the section. An anode gas supply pipe 14 for introducing the anode gas 12 and a cathode gas supply pipe 15 for introducing the cathode gas 13 are attached to the lower header 10, respectively. Further, an anode gas exhaust pipe 18 for discharging the anode exhaust gas 16
A cathode gas exhaust pipe 19 for exhausting the cathode exhaust gas 17 is also attached to the lower header 10.
An anode gas manifold 32 and a cathode gas manifold 3 that communicate with the respective gas supply / exhaust pipes in the lower header 10 at the peripheral portion 11 of the fuel cell stack.
3, an anode exhaust gas manifold 34, and a cathode exhaust gas manifold 35 are provided. Each manifold communicates with the anode gas flow channel 6 or the cathode gas flow channel 7, respectively. Due to the structure, the anode gas flow channel 6 and the cathode gas flow channel 7 are substantially orthogonal to each other.

Here, the operation will be described focusing on the electrolyte impregnation process performed in this embodiment.

In the case of a molten carbonate fuel cell, the temperature is kept at about 650 ° C. during normal operation, the hydrogen-rich fuel gas is used as the anode gas, and the oxidant gas containing a large amount of carbon dioxide is used as the cathode gas. used. Nitrogen gas is used as the purge gas. During operation, the carbonate applied to the substrate of the electrolyte plate 5 and the impregnated carbonate melt to fill the gap between the electrolyte plate and the separator and exert a wet sealing effect. However, at the time of initial temperature rise and startup, the sealing effect is not exerted up to about 500 ° C. at which the carbonate melts.

The fuel cell of this embodiment is an internal impregnation type in which an electrolyte plate is impregnated with an electrolyte at the initial stage of operation of the cell. As the electrolyte plate 5, a ceramic-based substrate mixed with a binder is used, and a carbonate is applied thereto. Assemble the fuel cell stack. Then, in the initial stage of the temperature rise of the battery, the heater (not shown) provided in the storage container is heated to evaporate the binder, and the voids formed thereby are impregnated with carbonate. As a binder, the carbonate melts about 5
Materials that melt and evaporate up to 00 ° C. are used. The initial temperature rise of the battery is performed by heating it to 650 ° C., which is the operating temperature of the battery, by a heater provided in the container.

Since the binder and the residual organic solvent of the electrolyte plate 5 are removed during the initial temperature rising process of the battery, the anode gas air supply pipe 14 and the cathode gas air supply pipe 15 contain a large amount of air and carbon dioxide at the time of the initial temperature rise. An inert gas is supplied to expel the evaporated binder and residual organic solvent. At that time, the exhaust valve 20 for the anode gas exhaust pipe and the exhaust valve 21 for the cathode gas exhaust pipe are closed, the valve 24 for the anode gas forced exhaust and the valve 25 for the cathode gas forced exhaust are opened, and the respective gas suction mechanisms 26 and 27.
The fuel cell temperature raising work is performed while using the. The carbonate substrate is impregnated with carbonate at a time when the carbonate has sufficiently melted from about 500 ° C. at which the carbonate starts to melt to about 650 ° C., which is a predetermined operating temperature, and the substrate is replaced with an electrolyte plate. Convert to 5.

The principle is to remove the organic solvent and the binder by about 500 ° C. at which the carbonate starts to melt. However, when the carbonate melts, it is not perfect, but the wet sealing effect at the periphery of the fuel cell stack acts. Come to do. As a result, the efficiency of removing the residual organic solvent and the residual binder increases from the beginning of the melting of the carbonate until the impregnation. In particular, the effect of removing the organic solvent and the binder is greatly enhanced by performing suction and exhaust. The lower the residual ratio of the organic solvent is, the less the deterioration of the fuel cell is, and the lower the residual ratio of the binder is, the less the non-uniformity of the electrolyte due to the uneven distribution and the better the performance of the fuel cell.

After the impregnation work is completed, the exhaust valves 20 and 21 are opened and the forced exhaust valve 24 is opened.
And close 25. After that, work to put the fuel cell into operation will be carried out.

It should be noted that the forced exhaust systems 22, 24, 26 and 23, 25, 27 do not have to be permanent facilities, and the forced exhaust valves 24 and 25 can always be connected to the fuel exhaust valves 24 and 25 at any point. While the battery is not operating, the branch pipe 22
It is also possible to remove it from a suitable place of 23 and 23 and put it on the lid.

Next, another embodiment according to the present invention will be described. In this embodiment, a purge gas exhaust pipe suction system shown by a dotted line in the drawing is added to the device of the embodiment shown in FIG. A branch pipe 36 is provided midway between the exhaust valve 31 provided at the tip of the purge gas exhaust pipe 30 and the fuel cell storage container 1, and is connected to the gas suction mechanism 38 via the forced exhaust valve 37. Thereby, the gas in the fuel cell storage container 1 can be sucked and exhausted.

In order to prevent abnormal combustion even when the hydrogen-rich fuel gas leaks during normal fuel cell operation, nitrogen gas is purged into the fuel cell housing container 1 with the purge gas air supply pipe 2
9 and the purge gas is exhausted from the exhaust pipe 30.

At the initial temperature rise of the fuel cell, the carbonate impregnation work is carried out according to the procedure described in the first embodiment.
At that time, the organic solvent and the binder leak from the fuel cell stack into the fuel cell container 1 together with the inert gas containing a large amount of air and carbon dioxide. Further, the organic solvent and the binder are released from the outer wall of the fuel cell stack. In order to discharge and remove the organic solvent and binder remaining in the fuel cell storage container 1, the purge gas exhaust pipe suction system is continuously operated during the carbonate impregnation operation. Since hydrogen gas is not used during the carbonate impregnation operation, it is no problem to supply an inert gas containing a large amount of air or carbon dioxide from the purge gas supply pipe 29.

By forcibly exhausting using the purge gas exhaust pipe suction system, an extremely large amount of gas can be suctioned and exhausted as compared with the purge gas circulation amount during normal operation. Therefore, the organic solvent and binder leaked into the fuel cell container 1 can be promptly discharged. As a result, the adverse effect of the residual organic solvent, that is, abnormal heating from the outside of the fuel cell stack can be avoided, and deterioration of the fuel cell can be reduced. In addition, the provision of the gas suction mechanism helps prevent the purge gas exhaust line from becoming large.

The forced exhaust system 36, 37, 38
Similarly to the case of the first embodiment, it does not have to be a permanent facility and can be removed in the same manner as described above.

[0034]

According to the present invention, it is possible to favorably remove the residual organic solvent and the binder from the electrolyte substrate during the impregnation work of the carbonate as the electrolyte. As a result, abnormal heat generation due to the organic solvent can be prevented. Further, the impregnation of the carbonate into the electrolyte substrate is made uniform, and a high-performance fuel cell can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a basic structure of a first embodiment of a fuel cell according to the present invention, and a system shown by a dotted line in the drawing shows an additional constituent element of the second embodiment.

FIG. 2 is a structural diagram showing a laminated structure of the fuel cell body of FIG.

[Explanation of symbols]

 1 Fuel Cell Storage Container 2 Fuel Cell Stack 3 Anode Electrode 4 Cathode Electrode 5 Electrolyte Plate 6 Anode Gas Flow Path 7 Cathode Gas Flow Path 8 Separator 12 Anode Gas 13 Cathode Gas 14 Anode Gas Air Supply Pipe 15 Cathode Gas Air Supply Pipe 18 Anode Gas Exhaust Pipe 19 Cathode gas exhaust pipe 22 Branch pipe 23 Branch pipe 24 Forced exhaust valve 25 Forced exhaust valve 26 Gas suction mechanism 27 Gas suction mechanism 29 Purge gas supply pipe 30 Purge gas exhaust pipe 31 Exhaust valve 36 Branch pipe 37 Forced exhaust valve 38 Gas suction mechanism

Claims (4)

[Claims] 1. An electrolyte plate is sandwiched between an anode electrode and a cathode electrode, and a separator provided with an anode gas flow path and a cathode gas flow path, which are in contact with the respective electrodes, is arranged outside, and each flow path is provided with the separator. In a fuel cell having a unit fuel cell configured by connecting a supply pipe and an exhaust pipe of anode gas and cathode gas, respectively, a gas suction mechanism is branched through a valve to the exhaust pipe of the anode gas and the cathode gas. A fuel cell characterized by being provided. 2. The gas flow path of the unit fuel cell according to claim 1, wherein each of the gas flow paths is formed in a region excluding a peripheral portion of the separator, and the peripheral portion of the electrolyte plate is in contact with the peripheral portion and laminated. The unit fuel cell is housed in a fuel cell storage container, and a purge gas replenishment mechanism for supplying and discharging purge gas and a purge gas exhaust pipe are provided in the fuel cell storage container, and a gas suction mechanism is branched to the purge gas exhaust pipe via a valve. A fuel cell characterized in that 3. An anode electrode and a cathode electrode are arranged by sandwiching an electrolyte plate, and a separator provided with an anode gas flow channel and a cathode gas flow channel in contact with each electrode is disposed outside, and each of the flow channels is provided with the separator. In an electrolyte impregnation treatment method of a fuel cell having a unit fuel cell constituted by connecting an anode gas and a cathode gas supply pipe and an exhaust pipe, respectively,
The gas inside the unit fuel cell is sucked through the branch pipes provided in the exhaust pipes of the anode gas and the cathode gas respectively, and the organic solvent and the binder remaining on the substrate of the electrolyte plate are removed by the gas suction. A method for impregnating an electrolyte in a fuel cell, comprising impregnating with an electrolyte after that. 4. An electrolyte plate is sandwiched between an anode electrode and a cathode electrode, and a separator provided with an anode gas flow channel and a cathode gas flow channel which are in contact with the respective electrodes is disposed outside, and each of the flow channels is provided with a separator. A unit fuel cell configured by connecting a supply pipe and an exhaust pipe for anode gas and cathode gas, respectively, is installed in a fuel cell storage container provided with a purge gas supply mechanism for supplying and discharging purge gas and a purge gas exhaust pipe. In the method for impregnating electrolyte of a fuel cell, the gas inside the unit fuel cell is sucked through the branch pipes provided in the exhaust pipes of the anode gas and the cathode gas, and the branch pipe provided in the purge gas exhaust pipe. The gas in the fuel cell storage container is sucked through the via, and the organic solvent and binder remaining on the substrate of the electrolyte plate are removed by the gas suction. An electrolyte impregnation treatment method for a fuel cell, which comprises impregnating the electrolyte with an electrolyte.