JPH07282827A - Normal pressure fuel cell - Google Patents

Abstract

PURPOSE:To suppress gas leak, reduce forced ventilation inside a housing, and enhance reliability by conducting pressure control so as to equalize the pressure in a reaction gas manifold and an exhaust manifold to the atmospheric pressure. CONSTITUTION:The capacity of a blower connected to supply side reaction gas pipelines 4a, 4c is made equivalent to pressure loss produced inside a supply pipe and inside a fuel cell stack. The capacity of a blower installed in exhaust side reaction gas pipelines 4b, 4d is made equivalent to pressure loss produced inside the exhaust pipelines. Pressure control can be made so that the pressure in fuel and air manifolds 3b, 3d becomes almost equal to the atmospheric pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a normal pressure fuel cell in which leak gas from a fuel cell stack is significantly reduced by pressure control.

[0002]

2. Description of the Related Art A fuel cell is a device for directly converting the energy released by an oxidation reaction by oxidizing the chemical energy of the fuel in an electrochemical process into electrical energy. This fuel cell power generation has a thermal efficiency of 40 to 50% even on a relatively small scale, and it is expected that it will far surpass new thermal power generation. In addition, emission of SOx and NOx, which are pollution factors that have become a big social problem in recent years, is extremely small, a large amount of cooling water is not required because a power generation device does not include a combustion cycle, and vibration is small.・ There are few environmental problems such as exhaust gas. Furthermore, it is suitable for cogeneration systems that have good responsiveness to load fluctuations, can theoretically expect high conversion efficiency, and use heat as well as power generation.
Because of such features, there is much interest and interest in the research and development, and practical application is imminent. As this type of fuel cell, for example, the one described in JP-A-60-93765 is known. That is, this battery body
As shown in FIG. 4, a unit cell having a pair of porous electrodes arranged with an electrolyte layer impregnated with the electrolyte sandwiched therebetween, and a coolant is supplied to and discharged from each of the unit cells to cool the battery. A plurality of cooling plates to be stacked are stacked and fixed by tightening means 21 to form a square columnar fuel cell stack 20, and the fuel cell stack 20 and the reaction gas manifold 22 are formed.
Is stored in the cylindrical tank 23. Electric power terminals 24 are provided at both upper and lower ends of the fuel cell stack 20, and are drawn out of the tank 23 via bushings 25. Further, the reaction gas manifold 22 is connected to a supply or discharge pipe 26 of a reaction gas such as air or fuel gas.

In such a conventional fuel cell, since the reaction gas has a high pressure, the tank 23 for accommodating the fuel cell stack 20 is one that can withstand the high pressure. However, recently, the practical application of an atmospheric pressure type fuel cell in which the reaction gas pressure is almost atmospheric pressure has been proposed.

This normal pressure type fuel cell is particularly suitable for on-site use by general consumers because it only requires housing the fuel cell stack in a housing and has a simple structure and system. FIG. 5 shows an example of such an atmospheric pressure fuel cell, in which a housing 30 contains a fuel cell 31 covered with a heat insulating material 32 and a reformer 33 for producing a reaction gas.

[0005]

Conventionally, the high-pressure type is housed in a tank 23 that seals the fuel cell stack 31, and the internal pressure of the tank 23 is controlled to be almost the same as the reaction gas pressure. The amount of leak can be adjusted to be a minimum. However, in the normal pressure type fuel cell as described above, the fuel gas pressure is generally taken into consideration in the pressure loss in the fuel cell stack and the front and rear pipes when pressurized by a blower or the like from the inlet side and sent to the fuel cell stack 31. The pressure inside the reaction gas manifold 22 is higher than the atmospheric pressure (atmospheric pressure) by the pressure loss in the reaction gas discharge side pipe. As a result, originally, the seal between the reaction gas manifold 22 and the fuel cell stack 31 including a large number of stacked parts cannot be completely performed, so that the leak of the fuel gas (generally hydrogen gas) increases and the utilization of the fuel gas is increased. Not only does the rate drop, but it accumulates in the housing 30 and is exposed to danger such as explosion.

In order to prevent this, it is necessary to constantly ventilate the air inside the housing with a ventilation device or the like, but with the increase in size of the equipment, a large ventilation device is also required and this has broken down. There is concern that it may lead to a major accident.
Moreover, although a gas detection device or the like for detecting a gas leak is also added, the gas detection inside the housing is inferior in detection accuracy and it is difficult to specify the leak position. on the other hand,
Since sufficient ventilation is required, the heat released by ventilation reduces the plant efficiency.

Further, as compared with the high-pressure type, the atmospheric pressure type tends to increase the reaction gas flow rate due to the pressure, so that the pipe size becomes large and the entire housing becomes large. An object of the present invention is to significantly suppress the leak gas by controlling the pressure of the leak gas from the seal portion of the reaction gas manifold and the laminated body so that the pressure in the exhaust manifold is the same as the atmospheric pressure, and to suppress the leak gas to a normal casing. When the fuel cell stack is stored inside the body,
It is to provide a compact, normal-pressure fuel cell that is safe, highly reliable, and compact because it requires less forced ventilation inside the housing.

[0008]

To achieve the above object, the present invention provides a unit cell having a pair of porous electrodes sandwiching an electrolyte layer impregnated with an electrolyte, and a predetermined number of unit cells. A plurality of cooling plates for supplying and discharging a refrigerant to cool the cells are stacked inside each cell to form a square columnar fuel cell stack, and the side surface of the stack has a supply reaction gas manifold and Reactor gas exhaust manifolds are arranged respectively, and blower and the like are installed in the supply pipe and exhaust pipe that communicate with the reaction gas manifold so that the exhaust manifold internal pressure becomes the same as the atmospheric pressure. It is characterized in that the pressure is controlled.

[0009]

In the present invention having the above structure,
It is possible to minimize the pressure at the sealing portion between the reaction gas manifold and the fuel cell stack, which has a high possibility of gas leakage. That is, the blower arranged in the supply side reaction gas pipe has a capacity corresponding to the pressure loss generated inside the supply pipe and the fuel cell stack, while the blower arranged in the discharge side reaction gas pipe reduces the pressure loss inside the discharge pipe. It will be possible by setting the capacity.

Further, the pressure inside the discharge side fuel gas (hydrogen) manifold is set to about atmospheric pressure, and each pressure is set so that the pressure inside the discharge side air manifold is equal to or lower than atmospheric pressure. It is possible to prevent damage to the inside of the battery stack by preventing the leakage of the.

[0011]

EXAMPLES Examples of the present invention will be described below. 1 and 2 show an embodiment of the present invention, and FIG. 1 is a front view of a fuel cell stack. FIG. 2 is a plan view of FIG. In this embodiment, the fastening plate 2 is provided on the upper and lower surfaces of the laminated body 1.
Are arranged. Further, the fuel gas (hydrogen) supply / exhaust manifold 3a, the fuel gas exhaust manifold 3 of the laminated body 1
b, an air supply manifold 3c and an air discharge manifold 3d are arranged, and reaction gas pipes 4a, 4b, 4c and 4d are connected to the respective manifolds. In addition, the reaction gas pipes 4a, 4b, 4c, 4d are provided with blowers 5a, 5b, 5
c and 5d are arranged in series. Further, the battery stack, the reaction gas tube 4, the blower 5 and the like having the above-described configuration are entirely housed in a casing 6, and the ventilation device 7 constantly ventilates the air inside the casing.

FIG. 3 shows the relationship of the pressures of the respective parts in the embodiment having the above-mentioned structure. In FIG. 3, the horizontal axis shows the positional relationship of the reaction gas system, and the vertical axis shows the pressure level. Point A is the most upstream point on the supply side, point B is the manifold position on the supply side,
Point C shows the discharge side manifold position, and point D shows the discharge side most downstream position. Line F shows the fuel gas pressure change and line A shows the air pressure change. The blower connected to the supply side reaction gas pipes 4a, 4c has a capacity corresponding to the pressure loss generated in the supply pipe and the fuel cell stack, while the blower arranged in the discharge side reaction gas pipes 4b, 4d is used for the inside of the discharge pipe. By making the capacity to cover the pressure loss, it becomes possible to control the pressure so that it becomes substantially equal to the atmospheric pressure at the position of each of the fuel / air discharge manifolds 3b, 3d, that is, at the point C. Here, in order to prevent the leakage of the reaction air into the fuel gas, the fuel gas pressure is increased at least in the range from point B to point C. Therefore, P5 can be set to atmospheric pressure (atmospheric pressure). In this case, point C air side manifold pressure P
No. 6 is below atmospheric pressure, but since the atmosphere is air, there is no problem. With such pressure control, if a conventional blower is installed between points A and B, P7 will be atmospheric pressure, and if it is large in 1000 kW class, the system piping will become long and P5 will be about 300 mmAq and P3 will be It will be about 500 mmAq,
The average pressure difference with the atmosphere is about 400 mmAq. In the configuration of the present invention, if the pressure control is performed, P5 is 0 mmAq and P3 is about
The pressure difference with the atmosphere is about 100 mmAq.
It will be about. Therefore, the amount of leak from the manifold is almost halved. As a result, the exhaust volume of the ventilation device 7 arranged in the housing 6 is also halved.

[0013]

As described above, according to the present invention, the leak gas from the seal portion of the reaction gas manifold and the laminated body can be greatly controlled by controlling the pressure in the exhaust manifold to be the same as the atmospheric pressure. When the fuel cell stack is stored inside a normal case by suppressing the leak gas to
It is possible to provide a safe and highly reliable normal-pressure fuel cell that requires less forced ventilation inside the housing.

In the case where the blower is installed only on the supply side, if an attempt is made to reduce the size of the reaction gas piping to make it compact, the pressure at points B and C will increase and the amount of leakage will greatly increase. Although it was a body, in the present invention,
Since the leak amount does not increase even if the reaction gas piping size is reduced, it is possible to provide an overall compact normal pressure fuel cell.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of an atmospheric pressure fuel cell of the present invention.

FIG. 2 is a plan view showing an embodiment of an atmospheric pressure fuel cell of the present invention.

FIG. 3 is a pressure diagram showing the pressure of each part of the atmospheric fuel cell of the present invention.

FIG. 4 is a vertical sectional view showing an example of a conventional high-pressure fuel cell.

FIG. 5 is a partially cutaway perspective view showing the structure of a general atmospheric pressure fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laminated body 2 ... Tightening plate 3a ... Fuel gas supply manifold 4a ... Fuel gas supply pipe 3b ... Fuel gas discharge manifold 4b ... Fuel gas discharge pipe 3c ... Air gas supply manifold 4c ... Air gas supply pipe 3d ... Air gas discharge Manifold 4d ... Air gas exhaust pipe 5a ... Fuel gas supply blower 5b ... Fuel gas exhaust blower 5c ... Air gas supply blower 5d ... Air gas exhaust blower 6 ... Enclosure 7 ... Ventilator 20 ... Laminate 21 ... Tightening means 22 ... Reaction gas manifold 23 ... Tank 24 ... Power terminal 25 ... Bushing 26 ... Reaction gas supply or discharge pipe 30 ... Housing 31 ... Fuel cell stack 32 ... Heat insulation material 33 ... Reformer

Claims (2)

[Claims] 1. A unit cell having a pair of porous electrodes arranged with an electrolyte layer impregnated with an electrolyte sandwiched between the unit cell and a cooling unit for supplying and discharging a refrigerant to cool the battery. A plurality of plates are stacked to form a rectangular columnar fuel cell stack, and a supply reaction gas manifold and a reaction gas discharge manifold are provided on the side surfaces of the stack so that the corner portions of the stack are exposed. A normal pressure type fuel cell, characterized in that each of these gas manifolds is arranged so that the pressure inside the fuel gas discharge manifold is controlled to be the same as the atmospheric pressure. 2. The reaction gas is supplied and discharged by suction or compression with a blower or the like inserted in a connecting pipe communicating with the reaction gas manifold for supply and the reaction gas discharge manifold of the fuel cell stack. A normal pressure fuel cell characterized by the above.