Liquid electrolyte fuel cell

Details Liquid electrolyte fuel cell Liquid electrolyte fuel cell

2000-12-28

2003-07-01

Kalafut, Stephen (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Having earth feature

C429S047000

Reexamination Certificate

active

06586129

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to fuel cells i.e. the devices which transform chemical power to electric power. It may be used as a source of electric power in any branch of industry, mainly in power engineering, mechanical engineering, and etc.
Fuel cells in general include a pair of porous electrodes, cathode and anode, and an ionic conductor, electrolyte, which is the solution of alkali, acid or melt of carbonates placed between the electrodes. Depending on the physical state of the electrolyte, the fuel elements are classified into elements with liquid electrolyte and solid electrolyte. During operation of the fuel cell, gaseous reagents come through porous electrodes: through the anode penetrates fuel and through the cathode penetrates the oxidant. Usually hydrogen (H
2
), and more rarely carbon oxide (CO), methane (CH
4
), and oxygen (O
2
), including oxygen from air as the oxidant, are used as the fuel for the fuel cells.
For example, in the oxygen-hydrogen fuel cell with an alkali electrolyte, the electric oxidation of the hydrogen on the anode occurs:
2H
2
+4OH→4H
2
O+4
e
and electric deoxidization of the oxygen occurs on the cathode:
O
2
+2H
2
O+4
e→
4OH
At the same time, the hydroxide-ions move in the ionic conductor-electrolyte from cathode to anode. The overall reaction is:
2H
2
+O
2
→2H
2
O
As the result of overall reaction, the EDS (electric dynamic power) arises in the external circuit between the cathode and anode, the direct electric current flows, i.e. the direct transformnation of chemical reaction to the electric one takes place (N. V. Korovin “Fuel cells”—Soros's educational magazine, No. 10, 1998, pgs.55-59). Since the described process of chemical energy transformation does not have any intermediate stage of heat generation, the fuel cells are specified with a high value of kpd (efficiency).
It is well-known, for example, the fuel cell consisting of porous matrix impregnated with necessary quantity of liquid electrolyte of electrodes pair: fuel electrode (supplying the hydrogen for the cell) and air electrode (supplying oxygen for the cell) which are located on both sides of the porous matrix (U.S. Pat. No. 5,677,073 MIK H01m27/00). The imperfection of this generator is the complicated and quite expensive cell production. This expense is due to the special materials required for the matrix. The need for special means of permanent control after the quantity of electrolyte decreases during generator operation and the need for special means of integration of elements in batteries.
A cell with the molten carbonates as the electrolyte is known (U.S. Pat. No. 4,554,225 MPK H01m27/00). The electrolyte is made in form of the plate of porous material and consisting molten carbonate at operating temperature. The electrodes cathode and anode are tightly adjacent to the opposite surfaces of the plate with electrolyte and are also made in the form of porous two-layers plates. The layer of electrode adjacent to the electrolyte is of such poor dimension that capillary interaction with the electrolyte takes place. It may be made of fibrous or powdery material. The second layer of the electrode has a different dimension of pores, unsuitable for capillary interaction with the electrolyte, and it is combined with a delivery device for oxidative or fuel gas. Working (fuel and oxidative) gases form on the surfaces of the respective electrodes, jointing to the electrolyte surface through the pores of electrodes and on the jointing surface of electrolyte occur respective chemical reactions of oxidization and deoxidization and it results in a rise of EDS. This fuel cell is the closest analogue of the offered cell and is recognized as a precursor of the invention. The main imperfection of the precursor is its high cost conditional to the complicity of porous elements production—the plates for electrolyte and electrodes. Thus, the unit of power received from such source is quite expensive.
BRIEF SUMMARY OF THE INVENTION
The offered invention solves the problem of fuel element cost on the account of its structure as a whole and its separate parts simplification and, as such, decreasing cost of the unit of power.
The solution for the problem is found by offering a fuel cell consisting of encapsulated molten carbonate, at temperature not lower than the melting temperature, and cathode and anode each connected to the device supplying the working gas: fuel gas to anode and oxidizing gas, and made in the form of impervious shell limiting its internal space filled with the working gas, herewith at least the part of the electrode shell immersed into the molten carbonates contains the catalyst for the chemical reaction of oxidization on the anode and deoxidization on the cathode, and they are provided with openings which dimension is of such value that the gas is kept inside the electrode shell and the molten carbonates are kept outside the mentioned shell for the account of the capillary forces.
The electrodes pairs may be placed in rows both along width and length of the chamber in one common chamber filled with molten carbonates.
In order to intensify the chemical processes occurring in fuel cell, the surfaces of electrodes, at least in the part neighboring the electrolyte, is covered with the layer of catalyst or the electrode in whole is covered with these materials. Since the electrodes operate in chemically corrosive medium, the catalyst is required to be not only highly chemically active but highly chemically stable as well. Lithinated (treated with lithium) nickel oxide is used as the cathode catalyst. Nickel and its alloys melts are used as the anode catalyst.
The shell of each electrode may be produced, for example, of the metal mesh with cell dimension 1-200 micrometers or of the metal wire winded in shape of spiral with the spacing less 200 micrometers. In this case the shell should be immersed in whole into electrolyte and contain the catalyst over all surface.
The electrode shell may be combined as well—partially solid, partially—permeable. In this case only the permeable part of the shell provided with the openings shall be immersed in the electrolyte and contain the respective catalyst.


REFERENCES:
patent: 4548876 (1985-10-01), Bregoli
patent: 4554225 (1985-11-01), Sounai et al.
patent: 4797379 (1989-01-01), Patel et al.
patent: WO 01/95414 (2001-12-01), None

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