JPS59105272A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To control differential pressure between an oxidizing agent electrode and a fuel electrode by inserting a pressure absorber between a fuel supply passage or discharge passage and an oxidizing agent supply passage or discharge passage and absorbing pressure difference between both passages. CONSTITUTION:A fuel cell 1 is accommodated in a container 5 filled with inactive gas. Oxidizing agent gas and fuel gas are supplied from supply passage 9 and 10 to a oxidizing agent chamber 4a and a fuel chamber 4b and they are discharged from discharge passages 10 and 12. Pressure in each chamber is measured with differential pressure controllers 13 and 14, and controlled with adjust valves 15 and 16 so as to keep specified pressure difference. Moreover, a pressure absorber 17 formed by setting pressure adjusting chambers on both sides of a diaphragm is arranged between the oxidizing agent supply passage 9 and the fuel supply passage 11. Abnormal increase of differential pressure between an oxidizing agent electrode and a fuel electrode is suppressed and generation of crossover in sudden load change at starting is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fuel cell power generation system that can stably control the differential pressure between an oxidizer electrode and a fuel electrode.

[Technical background of the invention]

Figure 1 shows the basic structure of a fuel cell.

The electrolyte matrix 1 is formed by holding a phosphoric acid electrolyte in a layer made of a nonwoven fabric of phenolic fibers or fine particles of silicon carbide. An oxidizer electrode 2a and a fuel electrode 2b are arranged to sandwich the electrolyte matrix 1 from both sides. These two electrodes 2a and 2b are made of carbon vapor or the like as a base material, and have a structure in which a catalyst such as platinum is adhered to the surface in contact with the electrolyte matrix 1, and a waterproof treatment is applied to the back surface. There is. A cell composed of the electrolyte matrix 1, oxidizer electrode 2a, and fuel electrode 2b is called a single cell, and is usually manufactured in an integrated manner.

In order to form a fuel cell stack by stacking these single cells, carbon plates 3a and 3b are arranged so as to sandwich the single cells. The carbon plates 3a and 3b are formed with an oxidizing agent supply passage 4a and a fuel supply passage 4b for supplying an oxidizing agent and fuel to the oxidizing agent electrode 2a and fuel electrode 2b, respectively.

Fuel cell jl (polar reaction is a reaction in the coexistence of fuel gas (or oxidant gas), catalyst, and electrolyte, i.e., an interfacial reaction in the coexistence of three phases of gas, solid, and liquid. In other words, under normal operating conditions) Below,.

H2 in the fuel flow flowing through the fuel supply channel 4b is transferred to the fuel electrode 2.
The ice surface of b becomes l(1, which is the electrolyte matrix 1
1 at the surface of the oxidizer electrode 2a.
H2O (water) is generated by reacting with O- produced from 02 in the oxidizing agent flow flowing through the injection agent supply channel 4a. At this time, electrons (e-) are transferred to the fuel electrode 2b through the external circuit.
to the oxidizer electrode 2a, and in order to maximize the performance of such a fuel cell, the three-phase interface must be maintained and controlled precisely. Controlling the differential pressure between the electrodes and the electrode 2b becomes an extremely important issue. Furthermore, the oxidizer electrode 2a and the fuel Vi, which generally constitute a single pond (5)! , 2b is the force −
Since the electrode is made of extremely brittle and easily damaged material such as Zimbe A, and it is necessary to maintain and control the three-phase interface during the electrode reaction, the pressure difference between the electrodes between the oxidizer electrode 2a and the fuel electrode 2b is Control must be carried out extremely carefully.

When the differential pressure between the two electrodes increases, fuel or oxidant leaks into other flow paths and burns on the surface of the electrode, resulting in crossover, in which the fuel or oxidant is consumed. If this crossover occurs violently, there is a possibility that the electrode itself will burn, so from the viewpoint of maintaining battery performance, the occurrence of crossover must be prevented as much as possible. Even if there is a small amount of crossover, there is a reactant gas that does not harm the cell reaction, so the fuel usage efficiency and oxidant usage efficiency will decrease accordingly, which will reduce the overall efficiency of the fuel cell. also decreases. Therefore, in fuel cells, it is necessary to improve the overall efficiency by preventing this crossover as much as possible and increasing the efficiency of fuel use and oxidizer use.

FIG. 2 is a block diagram schematically showing a conventional fuel cell power generation system equipped with an interelectrode differential pressure control device.

A fuel cell 9 having a laminated structure 479 as described in FIG. 1 is housed in the fuel cell container 5, and the enclosure is filled with an inert gas 8. Oxidizing agent supply channel 4a
Oxidizing gas is supplied to the oxidizing agent supply passage 9 and is discharged to the oxidizing agent discharge passage 1o.

Fuel gas is supplied to the fuel supply passage 4b from the fuel supply passage 11 and is discharged to the fuel discharge passage 12. The inert gas 8 in the fuel cell storage container 5 is supplied from the inert gas supply channel 6, and normally an inert gas such as argon or nitrogen is used. Inside the oxidant supply channel 4a! The pressure of the oxidizing gas to be agitated is measured by the differential pressure controller 13 based on the pressure of the inert gas 8. Similarly, fuel supply channel 4b
The internal pressure is also determined by the differential pressure controller 14 with reference to the inert gas 8.
61 is determined by Differential pressure controllers 13 and 14 control the oxidant discharge path 1o to control a preset pressure difference.

Pressure regulating valves 15 and 16 provided in the fuel supply path 11
is under control.

As mentioned above, the basics of pressure control in fuel cells is how to maintain and control the three-phase interface in a precise manner, but from a macroscopic perspective, fuel gas or oxidant gas is The goal is to prevent the water from penetrating through the water and leaking into other channels.

[Problems in the Background Art] In a fuel cell power generation system equipped with an interelectrode pressure differential control device as shown in Fig. 2, very good controllability can be obtained when the system is operated steadily. It will be done. However, when starting up the system, suddenly changing the load, or stopping the system, especially when the speed of change is fast, such as when suddenly changing the load or stopping the system suddenly, interelectrode differential pressure control cannot keep up and the maximum A pressure difference exceeding the permissible pressure difference value may occur between the poles. Therefore, in order to perform an operation that does not generate a pressure difference exceeding the maximum allowable pressure difference value, it is necessary to limit the rate of change within a range in which controllability can be maintained.

What particularly limits this control speed is the delay in the response of the pressure J1 regulating valves 15 and 16. Therefore, when there is a rapid change in the flow rate of the oxidizing agent or fuel flowing through the supply channel or the discharge channel for some reason, the conventional interelectrode differential pressure control device cannot fully perform its function. First, it has the disadvantage that the aforementioned crossover occurs.

[Purpose of the invention]

The purpose of the present invention is to prevent the occurrence of sudden changes in the flow rate of the oxidizing agent or fuel flowing through the supply flow path or the discharge flow path.
Prevents pressure difference between fuel electrode and oxidizer electrode,
An object of the present invention is to provide a fuel cell power generation system that can prevent the occurrence of cross-overs as much as possible.

In order to achieve the above object, the present invention includes a supply channel that supplies fuel and an oxidant to the fuel electrode and oxidizer electrode of a fuel cell, respectively, and a discharge channel that discharges the fuel and oxidizer from the fuel cell. In a fuel cell power generation system comprising: a fuel cell that is inserted between the fuel supply channel or discharge channel and the oxidizer supply channel or discharge channel, and absorbs the pressure difference between the two channels; It is characterized by being equipped with a pressure buffer.

[Embodiments of the invention]

The present invention will be described in detail below based on examples. Third
Figures (A), (B), (C), and (D) are configuration diagrams showing embodiments of the present invention, respectively. In the following drawings, the same parts as shown in FIGS. 1 and 2 are designated by the same reference numerals, and their explanations will be omitted.

In the case of FIG. 3(A), a pressure buffer 17 is inserted between the oxidizer supply channel 9 and the fuel supply channel 11 to absorb the pressure difference between the two channels. Although the specific configuration of the pressure buffer 17 will be described later, the oxidizing agent and fuel flowing through the oxidizing agent/supply channel 9 and the fuel supply channel 11 are not mixed in the pressure buffer 17, and the system A pressure buffer 17 is installed to absorb the pressure difference that occurs between the two.
works.

In the embodiment shown in FIG. 3(B), a pressure buffer 17 is inserted between the fuel supply channel 11 and the oxidant discharge channel 10.

Further, in the case of FIG. 3(C), a pressure buffer 17 is inserted between the oxidizer supply channel 9 and the fuel discharge channel 12, and the third
In the case of Figure (D), a pressure buffer 17 is interposed between the oxidant discharge channel 10 and the fuel discharge channel 12.

In this way, the pressure buffer 17 is inserted between the fuel supply channel or discharge channel and the oxidizer supply channel or discharge channel.

4(A), (B), (C), and (D) are diagrams each showing a specific configuration of the pressure buffer 17. FIG. Figure 4 (A)
In this case, the partition between the fuel and oxidant flow paths is a diaphragm 18 made of rubber, plastic, metal, etc., and the diaphragm 18 is sandwiched between the two τ
(In addition, a pressure adjustment chamber 11 is constructed. Fuel and oxidizer are respectively inflowed into or discharged from this pressure adjustment chamber.

In the case of FIG. 4(B), two partition walls are provided, and an inert gas supply port 22 is provided in the spaced apart cavity of the diaphragms 18 and 19.
The inert gas is introduced from the inert gas outlet and discharged from the inert gas outlet, so that the inert gas is stratified.

In the case of FIG. 4(C), bellows is used as the partition wall. The material of this bellows is similar to the diaphragm.
Rubber, plastic, metal, etc. are used.

FIG. 4(D) has a structure in which a spaced cavity is provided between the bellows and 21, and has almost the same structure as shown in FIG. 4(B).

In this way, a pressure buffer consisting of a diaphragm or bellows as a partition and pressure adjustment chambers provided on both sides of the partition,
When inserted between the oxidizer and fuel supply flow path or discharge flow path, even if a pressure difference occurs between the two flow paths due to a sudden change in flow rate, the partition wall that separates both adjustment chambers will prevent the pressure from changing. By curving from the higher side to the lower pressure side,
Since the pressure difference between both flow paths is absorbed, a pressure difference exceeding an allowable value will not be applied between the oxidizer electrode and the fuel electrode of the fuel cell.

In the embodiment shown in FIG. 3, only one pressure reliever 17 is used, but if necessary, a plurality of pressure relievers 17 may be used as a supply channel or a discharge channel for the oxidizer and fuel. Needless to say, it can be inserted between the two.

〔Effect of the invention〕

As described above in detail based on the embodiments, the present invention provides a pressure buffer that is interposed between the oxidizer and the fuel supply channel or the discharge channel to absorb the pressure difference between the two channels. The provision of the t'iJu converter electrode makes it possible to prevent the situation in which the differential pressure between the electrodes of the fuel cell and the fuel electrode increases abnormally. This has the advantage that the performance of the separate battery can be maintained over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the basic structure of a fuel cell, FIG. 2 is a diagram showing the configuration of a conventional fuel cell power generation system equipped with an interelectrode differential pressure control device, and FIG. 3 (A). (B), (C), and (D) are block diagrams showing embodiments of this invention, and Fig. 4 (A), (B), and (C)
, CD) is a diagram showing the basic structure of a pressure buffer used in the present invention. 9... Oxidizing agent supply flow path, IO... is an auxiliary agent discharge flow path, 11... Fuel supply flow path, 12... Fuel discharge flow path,
17... Pressure buffer, 18... Diaphragm, 19
... diaphragm, ribs... bellows, 21... bellows, sae... inert gas layer. Applicant's agent Kiyosu Inomata 4 1A) 7 (C1 7 Figure (B) 7 (Dl 7)

Claims (1)

[Claims] 1. A fuel cell comprising a supply channel for supplying fuel and an oxidant to a fuel electrode and an oxidizer electrode, respectively, and a discharge channel for discharging the fuel and oxidizer from the fuel cell. In the fuel cell power generation system consisting of
2. The fuel cell power generation system according to claim 1, characterized in that a pressure buffer is provided which is inserted into the flow path and absorbs the pressure difference between the two flow paths. A fuel cell power generation system characterized in that the buffer comprises a partition wall made of a diaphragm or a bellows, and pressure adjustment chambers provided on both sides of the partition wall. 3.% Permissible range The fuel cell power generation system according to claim 2, characterized in that two partition walls are provided spaced apart from each other, and an inert gas is filled in the spaced apart cavity.