JPS5986162A - Fuel battery system and operating method therefor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a fuel cell system.

Fuel cell systems such as fuel cell lightning plants that generate electrical power typically have integrated circuits arranged one on top of the other and electrically connected in series to form a stack. Contains a number of fuel cells. A fuel cell system may include any number of stacks. A reactant gas manifold is used to convey reactant gases to the fuel cell and to receive reactant flow reactant gases from the fuel cell. These manifolds are tightly attached to the sides of the stack, and compressible sealing material or gaskets are placed around the surfaces of the stack and around the edges of the manifolds to prevent leakage of reactant gases from the stack. is located between. US time 6'f which has the same ownership as the application
No. 4.345. '009 details +! Figures 1 and 2 of 1
The figure shows a stack of phosphorus 1lff salt-electric Pyi' fuel cells with an outer reactant gas manifold f1 on the side.

The ability to reliably seal the edges of the manifold to the surfaces of the stack is related to several factors, including the reactant gas pressure, operating temperature, and the type of electrolyte used within the fuel cell. This is used for sealing and 1q
Limit the materials used. There are also limitations as to the amount of force that can be used to press the outer manifold against the stack surface.

Molten carbonate electrolyte fuel cells operate at temperatures on the order of 649°C and reaction gas pressures on the order of 9.9 bar or higher. If operating at a pressure higher than atmospheric pressure, the stack will be under pressure.

placed in a container. In order to prevent the increase of flammable gas in the pressure vessel surrounding the stack and maintain high efficiency, it is necessary to completely prevent the reaction gas from escaping from the manifold under these rows. But this is very rotational.

One object of the present invention is to improve the outer reaction gas manifold.
The goal is to prevent leakage of reactant gas from the fuel cell stack.

According to the present invention, a fuel cell stack having an outer manifold includes a seal between the manifold and the stack and is continuously supplied with an inert gas at a pressure higher than the reactant gas pressure within the stack. Once directed into the vessel, the inert gas within the pressure vessel continuously leaks through the seal and into the reactant gas manifold.

The fuel cell system of the present invention tolerates leaks rather than trying to prevent them.

However, the fuel cell system of the present invention-Jmui,l,! Ensure that leaks are made into the reactant gas manifold and not from the reactor gas manifold. C' Difficulties in forming a reliable seal 1
Make one thing unnecessary.

The present invention uses molten a1 as a carbonate electrolyte fuel? h pond system and J
(It is well suited for use in 'lVj.
iii. It was impossible to form and cover the leaky outer manifold seal.

As used herein, the term "non-ITL gas" does not contain harmful components of I) that would have a harmful effect on the stack components, but does This refers to gases that do not substantially reduce performance. Therefore, for safety purposes, the inert gas may contain substantial amounts of oxidizing or oxidizable components (i.e., 02, CI, Go, CH4, and 1'2) that react at the operating temperature of the fuel cell. This must not be the case, since the combination of these ingredients can cause an explosion. Also, there must be no ingredients present that would accelerate corrosion of the fuel cell or manifold.

In a preferred embodiment, the fuel cells of the stack employ molten carbonate electrolytes, and the reacted fuel gas is exited from the combustion manifold and contains carbon oxides, unreacted hydrogen, and other hydrocarbons. It is burned to remove substantially all of the combustible material. The gas thus combusted, or a portion thereof, is then introduced into the pressure vessel as an inert gas. Test results in fuel cell systems in which stacks of 10 to 20 fuel cells with an active area of 0.09 cm2 have been tested have shown that leakage of inert gas into the stack through the manifold seals is It has been shown that the efficiency of the system can be kept at such a level that the reduction in efficiency can be kept to less than 1/10 of 1%.

The above and other objects, features and advantages of the present invention will become more apparent as the preferred embodiments of the present invention are described in detail in the drawings.

The invention! It! As a typical example, consider a fuel cell system as shown in FIG. In this system, the fuel cell stack is made up of several stages of fuel cell manifolds that are stacked and electrically connected in series. Each of the fuel cells consists of a molten carbonate J placed between pairs of electrodes.
iContains electrolytes/v. The next 1 key fuel cell is a gas impermeable, 9 electrically conductive fuel cell. The structure of such a fuel cell is well known to those skilled in the art and represents some of the novelty of the hot light.
There is. A gas space 15 is thereby defined between the stack 10 and the container 14 surrounding it.

Each of the four stack sides 16.18.2'O and 22 each have a reactant gas manifold 24.26.28.30 attached by means not shown. These manifolds are described in U.S. Pat. No. 4,245.
Stack 10 in the manner shown in Book No. 009
The method of attaching the 72 small lead to the side of the stack is part of the present invention. Katana Sugugu 1 to Seal 29 are stack 10
side 1G, each of 18.20.22 and its respective manifold 24.26.28.30 peripheral flange 31
It's sandwiched between the two. Seal 29
is not airtight. The seal may be, for example, a laminate fiber seal that is porous and compressible and is virtually inert to molten carbonates of the type commonly used as fuel cell electrolytes.

Manifold 24 is a fuel gas inlet manifold that is supplied with a hydrogen-enriched gas stream via pipe 32 .

Manifold 24 conveys fuel gas to fuel cell stack 1-2. Fuel gas passes across the stack and through the fuel cells and is received at fuel gas outlet 28. Reacted fuel gas (fuel gas with most of the hydrogen reacted) leaves manifold 28 via tube 34 . The manifold 26 is a Roman manifold containing A oxidant gas. The manifold receives oxidant gas through conduit 36 and conveys it to fuel cell 12, 5; Oxidant gas passes through the fuel cell stack in a direction perpendicular to the direction of fuel gas passage across the stack and is received by oxidant gas outlet C manifold 30. Gas is transferred to the reacted oxidane 1 through conduit 3
8 and leave manifold 26.

Simplified fuel electric i1 in Figure 1! A carbon-containing raw material in a liquid or gaseous hydrocarbon system is supplied by means not shown, and the fuel cell stack is applied to an operating pressure of <2°. (Fuel cell stacks can operate at atmospheric pressure, but they can operate at pressures higher than atmospheric pressure.) This fuel is introduced into a fuel conditioning device, such as steam reformer 40, along with steam at the same pressure. In reformer 40, hydrogen is reformed by reaction of steam and carbon-containing feedstock in the presence of a suitable catalyst, such as nickel supported on ceramic. The hydrogen-rich reformed fuel is approximately 50% hydrogen, 10% CO, 10% CO2, and 30% H20 by volume. This reformed fuel is supplied from the steam reformer 40 through the conduit 32 to the fuel gas-filled Romanibold 24 of the stack 10.

The reaction bay fuel gas leaving the fuel gas outlet manifold 28 through conduit 34 contains carbon dioxide, unreacted hydrogen, carbon dioxide, and water vapor. This gas stream 1J is passed through a condenser 44, with water being removed via conduit 4G. This water is converted into steam in the boiler 48, and this steam is conveyed from the boiler to the steam reformer v340 via the S pipes 5,0.

Compressed air from a compressor 54 driven by a turbine 56 is supplied via conduit 36 to the oxidant gas manifold 26 of the stack 10, which is the A1 cidant gas that supplies the fuel cell stack 12. As is well known to those skilled in the art, it takes 1 minute for the fuel cell stack reaction in a molten carbonate electrolyte fuel cell to run efficiently: It! air contains carbon monoxide. Therefore, the CO2 part of the reacted fuel gas output needs to be added to the air introduced into the stack.
Towards the end, C must be removed. Thus, the now relatively dry reaction fuel gas is conveyed from the condenser 44 to the burner 42.
: Air is also supplied to the burner /I2/\ through the conduit 58.

Burner and A xicun 1 ~ gas person 1° 1 mark small route 26
The air provided to the steam reformer /'/'IO is at the same pressure as the fuel entering the IO, so the Her force difference across each fuel cell stack 12 is minimal. The pressure in burner 42 (only differs due to the unavoidable pressure drop in the system)
1J of air is introduced into the burner 42 so that the output from the burner 42 contains essentially only carbon dioxide, nitrogen and small amounts of water, hydrogen, carbon oxides and other combustible materials! Preferably, the amount is just sufficient to ensure completely complete combustion.

After the oxidant passes through the fuel cell stack, the hot reacted oxidant gas from the output Romanibold 30 is passed through a heat exchanger 62 to provide heat to the boiler 48 . The reacted oxidant gas stream, which still contains a significant amount of energy, may then be used to energize turbine 56.

In accordance with the invention, a small amount of the burner discharge from the conductor 60 is directed into a conduit 64 and is slightly pressurized by suitable means such as a blower 66. This gas, raised to a pressure slightly higher than the pressure of the reaction gas supplied to the stack 10, is conveyed into the gas space 15 of the pressure vessel 14 and continues through the seal 29 into the reaction manifold. will be leaked.

As mentioned above, the burner effluent contains essentially only carbon dioxide, nitrogen and a small amount of water vapor. Of course, nitrogen
It is completely non-reactive and corrosive within the stack 10. Leakage of carbon dioxide into the manifold is, of course, also harmless. Why 4 d, carbon dioxide is 7J:1-methane 1
It is a necessary component of hydrogen gas, and is also a by-product of the fuel cell reaction on the fuel gas side of the fuel cell.
42 b.s.t. If the emissions contain hydrogen in excess of the permissible limit, or combustible substances or water in excess of the permissible limit, separate additions should be made to further reduce the amount of these components. A typical burner and/or condenser may be incorporated into conduit 64. Pressure capacity 4. The inert gas introduced into the vessel is approximately 1.0
% oxygen, up to about 2.0% hydrogen, and up to about 1.0% methane.

The limiting factor is system efficiency, and J
It's not about Lum.

Figure 2 shows a stack of 525 fuel cells, each approximately 1.44m1! A molten Fl having an active area of
The effect of inert gas leakage into the stack manifold on the overall efficiency of an I;A acid-fired single cell power plant is graphically illustrated. The manifold leakage is shown in the graph in m3 per stack and per hour. 0.0911 each
By scaling up the leakage rates that actually occurred in tests of 13 stacks of 20 fuel cell stacks, a much larger stack of 525 fuel cell stacks would have a leakage rate of about 6.5 mm per hour. It is determined that IW will leak at a leak rate of 94 m'. As can be seen from the graph, at a leakage rate of 6.94 m1/h, power generation plan 1
efficiency decrease of ~1% (compared to the case without delamination) 1 /
10 J: Rimo is small. Efficiency losses associated with leakage rates three or four times this leakage rate may also be tolerated. One of the reasons for such a small efficiency loss is that most of the inert sludge used for pressurization, and therefore also its Nerki-containing material, is not lost to the system. In one test of the present invention, a stack of 20 square molten carbonate electrolyte fuel cells, each 30.5c+nx30.5cm, was housed in an N4 pressure vessel.

A stainless steel reaction gas manifold was attached to each of the four sides of the stack. A 0.254 cm thick zirconia fiber sprue was used as a seal between the side of the stack and the outer edge of the manifold. Reaction gas was fed to the manifold at a pressure of 9.8 bar. Inert gases of nitrogen and carbon dioxide with the same ratio of nitrogen and carbon dioxide were used to stain the burner exhaust gas. This gas is higher than the pressure horn of the reaction gas 2.5/
I-・7.62 cmH2O pressure was supplied into the pressure vessel, and the fuel cell was operated at a constant richness of approximately 649°0.
0 (゛0When moving, the inert gas has a pressure 'f'f
'＋? 'r/)''-, > Approximately 0 in the reaction gas manifold
．． It was measured that a leakage rate of 51 m1/l+ occurred at 1 degree. This is (i, '/!Irn3/11
This corresponds to a reaction waste flow into the 7-nifold of fuel and 12.1 m'/h oxidant. When used as part of a power plant, power generation plan 1 - low overall efficiency due to inert gas leaking into the reactor manifold at a rate of 1 - i = <, to, 1% or less .

Although the present invention has been described in terms of its preferred embodiments, it should be understood by those skilled in the art that various changes and omissions may be made in the form and details of (within the scope of the present invention).
1! It will be understood.

[Brief explanation of drawings]

Figure 1 is a partial block diagram and partial schematic diagram of a fuel cell system by Akira Thu J5. Figure 2 is a graph showing the effect of manifold leakage on the efficiency of a fuel cell system. Yes. 10...Fuel cell stack, 12...Fuel cell, 1
4... Pressure-tight container, 15... Gas space, 16-22.
...Stack side, 24.26.28.30...Reaction gas manifold, 29...Seal, 32-38...
conduit. 40... Steam reformer, 42... Burner, 44...
・Condenser, 4G... Conduit, 48... Boiler, 50.
... Conduit, 54 ... Honey compressor, 56 ... Turbine,
58.60... Conduit. 62...Heat exchanger, 64...Conduit, 66...Blower special '1 Applicant: United Chiknoroses
Corporation

Claims (3)

[Claims] (1) A fuel cell system comprising: a fuel cell stack including a plurality of fuel cells; an outer reaction gas manifold means attached to the stack; and a gas seal disposed between the gas manifold and the stack. and means for conveying a fuel cell reactant gas into the manifold means at a first pressure, surrounding the stack and the manifold means and defining a gas space therebetween. a pressure vessel, the pressure vessel comprising: a source of inert gas; and means for conveying a second pressure of inert gas from the source to the space within the pressure vessel; 3, through which the gas sealing means passes! l! constructed and arranged to permit positive gas leakage, whereby inert gas continuously leaks from the gas space through the gas sealing means into the reaction gas manifold means. fuel cell system. (2) a fuel cell system comprising: a fuel cell stack including a plurality of fuel cells each containing a molten carbonate electrolyte; and a fuel gas inlet manifold attached to the stack for conveying fuel to the fuel cells. a fuel gas outlet manifold for receiving reactant stream fuel from the fuel cell; an oxidant gas inlet manifold for transporting oxidant to the fuel cell; and an oxidant gas inlet manifold for receiving reacted oxidant from the fuel cell. an outer reactant gas manifold including an outlet manifold;
gas seal means disposed between the gas manifold means and the stack; and gas seal means disposed between the gas manifold means and the stack; and a gas seal means disposed between the gas manifold means and the stack; and means for conveying at least a portion of the reacted fuel gas to the combustion output manifold. a pressurized canister surrounding said stack and manifold means and defining a gas space therebetween; and burner means for directing at least a portion of the waste fuel gas to said fuel to produce an inert scum. means for conveying at least a portion of the inert gas from the burner means at a second pressure higher than the first pressure to the burner means; means for conveying the gas into the gas space, said gas sealing means being constructed and arranged to permit continuous gas leakage therethrough; A fuel cell system characterized in that there is continuous leakage from the gas space in the pressure horn vessel through the gas sealing means to the fuel r1 and oxidant inlet and outlet manifolds. (3) a fuel cell stack containing a plurality of fuel cells and a side wall of the stack for transporting fuel and oxidant reaction scum to the stack's fuel cells and for receiving reacted fuel and oxidant reaction scum from the stack's combustion cells; including attached fuel and oxidant reactant gas inlet and outlet manifolds, the reactants within the manifold and the stack being at a first pressure, and the stack being within a pressure vessel defining a gas space surrounding it. The method of operating the fuel cell system arranged therein includes the steps of: continuously supplying inert gas into the gas space at a second pressure higher than the first pressure; and inert gas into the gas space. A method for operating a fuel cell system, comprising the steps of: continuously leaking a reaction gas from a reactant gas into a manifold;