JPS61101968A - Fuel cell - Google Patents

Abstract

PURPOSE:To suppress reaction gas leak to the utmost for rationalization of insulating construction, reduction of a piping space and improvement of heat recovery efficiency by arranging piping on the side of reaction gas supply and piping on the discharge side coaxially while housing the piping on the supply side inside the piping on the discharge side. CONSTITUTION:A hydrogen gas supply pipe 11 and a hydrogen gas discharge pipe 12 as well as an air supply tube 13 and an air discharge pipe 14 are arranged coaxially respectively from a tank 15 to a reaction gas treatment system. Since the reaction gas supply pipe is housed inside the reaction gas discharge pipe for arranging them coaxially, a pressure difference between the reaction gas supply pipe and the reaction gas discharge pipe is not more than a head pressure difference so that pressure-tight construction of the reaction gas supply pipe requires no consideration. Further, the reaction gas discharge pipe is provided with an insulation material 16 while the reaction gas inside the reaction gas supply pipe is preheated and insulated by the reaction gas so as to be able to perform rationalization of insulating construction, reduction of a piping space and improvement of heat recovery efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a reactant gas supply side and discharge side piping configuration of a fuel cell.

[Technical history of the invention and its problems 1] A fuel cell is a device that directly converts the energy released in the oxidation reaction into electrical energy by oxidizing the chemical energy of fuel through an electrochemical process. Power generation plants using fuel cells are expected to achieve a thermal efficiency of 40 to 50% even on a relatively small scale, far exceeding new thermal power plants. Furthermore, SOX is a pollution factor that has become a major social problem in recent years.

In principle, high energy conversion efficiency can be expected, such as extremely low NOx emissions, no combustion cycle involved in the power generator, no need for cooling water, and low vibration noise, as well as reduced noise and exhaust gas. There are fewer environmental problems,
Furthermore, because it has features such as good responsiveness to load fluctuations, there are expectations and interest in research into its development and practical application.

The problem with the practical application of such fuel cells is that it is difficult to expect a significant increase in the unit capacity of fuel cells due to their structure, workability, and transportation constraints. How to make it compact, minimize installation space, and improve thermal efficiency with a rational heat-insulating structure. Furthermore, since hydrogen gas is used as a fuel, there is a need to consider how to prevent fuel leaks and create an explosion-proof structure, considering the possibility of hydrogen gas leaking and even explosions caused by leaks. This point will be specifically explained below using a conventional fuel cell as an example.

First, a cross-sectional model diagram showing the principle of a fuel cell is shown in FIG. That is, an electrolyte layer 2 impregnated with an electrolyte such as phosphoric acid is interposed between the - set of porous electrodes 1 to form a single conductive layer, and hydrogen gas H and air are applied to both end surfaces of the single conductive layer. Supply A continuously. In this way, reaction products and reaction residues are continuously removed to the outside, so power generation can be continued for a long period of time.

Further, the basic configuration of such a fuel cell is as shown in FIG. 2. That is, a positive electrode 4 and a negative electrode 5 are disposed on both sides of an electrolyte matrix wide 3 to form a rectangular plate-shaped single electrode, and in order to use this single electrode as a power generation device, a large number of single electrodes are are connected in series and stacked, and interconnectors 6 with grooves for supplying gas are provided between these single conductors, and are stacked alternately with the single conductors. There is. This grooved interconnector 6 is provided with a plurality of grooves that open on two opposing side edges, and a hydrogen gas flow path 7 that uses the groove on the - side as a flow path, and a flow path that uses the groove on the other side as a flow path. The air flow paths 8 are arranged in directions perpendicular to each other.

By the way, the fuel cell currently under development is
As shown in FIGS. (a) and (b), a cell stack 9 is constructed by stacking a plurality of single electrodes as described above in a rectangular shape, and reaction gas supply manifolds 10a and 10 are provided on the four circumferential sides of the cell stack 9.
b and reaction scum discharge manifolds 10c and 10d are attached. This V-nifold 10a, 1
0b, 10c.

A hydrogen gas supply pipe 11, a hydrogen gas discharge pipe 12, an air supply pipe 13, and an air discharge pipe 14 are connected to 10d, respectively. Then, hydrogen gas enters the supply side manifold 10a from the fuel processing system through the hydrogen gas supply pipe 11, flows into the groove of one interconnector 6 that is open on one side of the cell stack 9, and flows inside this groove. The hydrogen gas is discharged from the side opposite to one side of the lever to the discharge side manifold 10b and sent to the fuel processing system through the hydrogen gas discharge pipe 12.

In addition, air enters the supply side manifold 10C from the air treatment system through the air supply pipe 13, flows into the groove of one interconnector 6 that is open on one side of the cell stack 9, and flows inside this groove. The air is discharged from the side opposite to this one side into the discharge side manifold 10d and sent through the air discharge pipe 14 to the air treatment system.

In addition, the operating temperature of such a fuel cell is set at around 200°C to increase efficiency, and the hydrogen gas and air are heated by a heater and supplied to the inlet and outlet of the gas inflow into the cell stack. It must be ensured that the temperature does not become uneven.

When putting a large-capacity fuel cell power generation plant into practical use, it is necessary to install dozens or even hundreds of fuel cells.
Needless to say, how to reduce the installation space for the reactant gas supply and exhaust piping will greatly affect the overall cost of the fuel cell itself.

Further, as the capacity of the fuel cell increases, the capacity of the heater for heating the reactant gas increases, which increases equipment cost 1- and requires a longer distance between the fuel cell body and the heater. As a result, the temperature of the reactant gas decreases in the middle of the piping, reducing power generation efficiency, so heat insulators have been used as a countermeasure.

However, the piping system is complex and diverse, making installation work difficult and requiring a large space.

Furthermore, it requires a large amount of hydrogen gas as fuel gas,
If hydrogen gas leaks from the fuel gas piping, there is a risk of explosion, and special consideration must be taken to prevent fuel gas leaks.

[Object of the invention] The present invention was proposed in accordance with the above-mentioned requirements, and
The purpose is to provide a highly efficient fuel cell by preventing leakage of reactant gas without complicating the configuration of reactant gas piping, reducing piping space by rationalizing the heat insulation structure, and improving heat recovery efficiency. It is in.

[Summary of the Invention J The fuel cell of the present invention houses a cell stack formed by stacking a plurality of single electrodes in a tank, and stores fuel gas (hydrogen) as a reactive gas in a manifold provided around the four circumferences of the cell stack. and piping for supplying and discharging oxidizing gas (air).The reaction gas supply side piping and the discharge side piping are arranged coaxially, and the high pressure supply side piping is housed within the discharge side piping. This structure makes it possible to suppress leakage of reaction gas from at least the supply side piping to the outside as much as possible, and also to rationalize the storage structure, reduce piping space, and improve heat recovery efficiency.

[Embodiment 1 of the Invention The present invention will be specifically explained below with reference to the embodiment shown in FIGS. 4 and 5. Note that the same members as those of the conventional type shown in FIGS. 1 to 3 are designated by the same reference numerals, and a description thereof will be omitted.

As shown in FIG. 4, reaction gas supply manifolds 10a and 1 are placed around the cell stack housed in the tank 15.
0b and reaction gas discharge manifolds 10c, 10d
is installed. This manifold 10a, 10
A hydrogen gas supply pipe 11, a hydrogen gas discharge pipe 12, an air supply pipe 13, and an air discharge pipe 14 are connected to b, 10c, and 10d, respectively. In this reaction gas supply and discharge pipe, from the tank 15 to the reaction gas processing system, there is a hydrogen gas supply pipe 11, a hydrogen gas discharge pipe 12, and an air supply pipe 13.
and the air supply pipe 14 are arranged coaxially. In order to increase the power generation efficiency of fuel cells, the pressure of the reactant gas is increased to 4 to 8 k.
g/Cll12, but since the reaction gas supply pipe is housed in the reaction gas discharge pipe and arranged coaxially, the pressure difference between the reaction gas supply pipe and the reaction gas discharge pipe is only the head pressure difference, and the reaction gas There is almost no need to consider the pressure-resistant structure of the supply pipe.

In addition, a heat insulator 16 is attached to the reaction gas discharge pipe, but the reaction gas in the reaction gas supply pipe is preheated and kept warm by the reaction gas in the reaction gas discharge pipe, which streamlines the heat insulation structure and reduces piping space. and improve heat recovery efficiency.

Next, FIG. 5 shows an embodiment of a method for coaxially arranging reaction gas supply and discharge pipes. The reaction gas supply pipe is assembled into the reaction gas supply and discharge pipe, and the same flange 17 is welded and attached. The opposing supply and discharge pipes assembled in the same manner are attached with tightening bolts 18.

Although the internal reaction gas supply pipes are simply butted together with a gasket 19 sandwiched between them, the sealing effect is sufficient since there is almost no differential pressure within the reaction gas supply and discharge pipes. However, if the reaction gas discharge pipe is housed in the reaction gas supply pipe for some reason, the sealing effect will be slightly worse when the above structure is used, but when compared with the conventional structure, the same effect as in the present invention can be obtained. be able to.

[Effects of the Invention] As described above, according to the present invention, there is almost no pressure difference between the reaction gas supply pipe and the reaction gas discharge pipe, without complicating the configuration of the reaction gas piping. There is no need to consider the pressure-resistant structure of the supply pipe, leakage of the reaction gas can be prevented, and an explosion-proof structure for the reaction gas can be provided.

Furthermore, the heat retention of at least the reaction gas supply pipe is enhanced by the exhaust gas heat of the reaction gas discharge pipe, so that the heat insulation structure can be rationalized and the piping space can be reduced.

In addition, the reaction gas fed into the cell stack has conventionally been preheated before being supplied, but the exhaust gas heat from the reaction gas exhaust pipe provides a preheating effect, improving heat recovery efficiency and generating power for the fuel cell. Increased efficiency.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional model diagram showing the principle of a fuel cell, Figure 2 is a perspective view showing the basic configuration of a fuel cell, and Figure 3 (a) shows a schematic configuration of a fuel cell currently under development. 3(b) is a longitudinal sectional view thereof, FIG. 4 is a longitudinal sectional view showing one embodiment of the fuel cell of the present invention, and FIG. 5 is an enlarged view of section D in FIG. 4. 9...Cell stack 10a, 10b, 10c, 10d-manifold, 11...Hydrogen gas supply pipe, 12...Hydrogen gas discharge pipe, 13...Air supply pipe, 14...Air discharge pipe, 1
5...Tank

Claims (2)

[Claims] (1) A cell stack consisting of a plurality of stacked electrical conductors is housed in a tank, and piping is connected to the tank for supplying and discharging combustion gas and oxidizing gas from outside the tank. What is claimed is: 1. A fuel cell constructed in this manner, wherein a reactant gas supply side pipe and a discharge side pipe are arranged coaxially. (2) The fuel cell according to claim 1, wherein the supply side pipe is coaxially arranged within the discharge side pipe.