LU87444A1 - FERROUS FUEL MATERIAL FOR A FUEL CELL ELEMENT AND METHOD OF USING THE SAME - Google Patents

Description

Λ “7 / T. ΙΑ GRAND-DUCHY OF LUXEMBOURG

Patent N ° O ....... · ........... TT .......... J * *, BL 4211

Minister of ........ 31 ....... leverage ....... 198_9 Economy and the Middle Classes T. „,, ^ 3 Intellectual Property Service

...................................-! ip) LUXEMBOURG

Patent Application ..........................................-. .............-.................................... —...................—---------------------------—. .......................... (1) I. Request

Metallurgical Research Center-Centrum voor Research ^ 2) in de Metallurgie, Association non-profit-Vereniging zonder winstoogmerk ........... 277 ........ rue ...... Montoyér ...... I-IÖ'4'Ö -...... BKÖXSEEES ............................ ...............

....Represented by.........;.............. ..FREYLINGER ....... & ...... E ........ MEYERS ....... Ing. „......... cons. in (3) P. î ................ 4.6 .., ......... rue ....... du ..... .Cemetery ....... LUXEMBOURG Mandatories deposit (s) this Thirty-one January one thousand nine hundred eighty nine ^ at ........... f ........ 9. ...... hours, at the Ministry of the Economy and the Middle Classes, in Luxembourg: 1. this request for obtaining a patent of invention concerning: .......... .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .............................................. '(5) "Ferrous combustible material for an element of a fuel cell and ...... its ...... process ...... 3''ûÜlIsationw ............ .................................................. ................................

2. description in language ..... fr.an.Sai se ................................. ............................... of the invention in triplicate; 3. ............... λ ................................ ......... drawing boards, in triplicate; 4. the receipt of the taxes paid to the Luxembourg Registration Office on ...... 31 ........ January i ........ 1.9.8.3 ...; 5. the delegation of power, dated ................ Br.UJie.lles .................... ............-..... on .26 .............. January ....... 198 S ..... ; 6. the successor document (authorization); declares (s) assuming responsibility for this declaration, that the inventor (s) is (are): (6) MGNFGRT ....... Guy ........... ..117, ........ rue-Neuvice ............. 4.32.0 ...... MONTEGNEE ............ .Belgium.................................

claims (s) for the above patent application the priority of one (s) request (s) of (7) ........................ .... invention patent _______________ registered in (8) Belgium .................................. ..............................................

on (9) _____________ February 3, 1988_______________________________ _______ _ under N ° (10) _______________................................. .................................................. .................................................. ............. ..................................... ..................

in the name of (11) ....... Ceu.tr, e ...... de ...... Re cher che s .... Mâ.ta.llur.g.ig; ue.s ............................................... .........................................

elect (elect) domicile for him / her and, if designated, for his / her representative, in Luxembourg_____________________________________________________________________________ 46, rue du Cimetière _ _ ^ request (s) the grant of a patent for the invention for the object described and represented in the above-mentioned annexes, with postponement of this issue to ........................................ .................................................. .................................................. .................................. ............ months. (13)

The depositor / mandate: ............................. ............. ... .................................................. .................................................. ............................. ..................... ...... (14) yf I Π. Depot Minutes

The aforementioned patent application has been filed with the Ministry of the Economy and the Middle Classes, Intellectual Property Service ^ we ^^ chxOTibourg, dated: January 3, 1989 /> ♦ \ \ (.? \ ^ \ Pr. The Minister of Economy and the Middle Classes, S f: 5d / a.

'^' "^^ 0 /" / The head of the service ^! Intellectual property, V * 3s .., - # / 7 / y A 68007_1 ^ 1 '~ _ / / _ EXPLANATIONS RELATING TO THE FORM l'ttETJfî'OT . / (l) if applicable "Request for certificate of addition to the main patent, to main patent application No .... ./f .. .l. / ûu ....... . "- (2) enter the surname, first name, profession, fi. Address of the applicant, when the latter is an individual or company name, legal form, address dirsiège Ucial, when the applicant is a legal person - (3 ) enter rii) 4 γΛ surname, first name, address of the professional representative, industrial property attorney, with special powers, if any, represented by ............ acting quality of representative ”I f U i. / / - (4) date of filing in full - (5) title of the invention - (6) enter the names, first names, addresses of the inventors or the indication" (see ) separate designation (will follow) ”, when the designation is or will be made in a separate document, or the indication" do not not mention ", when the inventor signs or signs a non-mentton document to be attached to a designation 9 1 · BL 4211

Claim to the priority of the patent application filed in Belgium on February 3, 1988 No 08800128 Descriptive memorandum filed in support of a patent application for invention: "Ferrous combustible material for an element of a fuel cell and its process of use "

Metallurgical Research Center Centrum voor Research in de Metallurgie

Non-profit association Vereniging zonder winstoogmerk 47, rue Montoyer 1040 BRUXELLES Belgium - 1 -

J

Ferrous combustible material for an element of a fuel cell and its method of use.

The present invention relates to a ferrous combustible material for an element of a fuel cell, as well as its method of use.

A fuel cell is an electric generator of a particular type, in which the production of electric current is carried out from chemical reactions involving the consumption of a material serving as fuel. The principle of such batteries has been known for a long time. Among the numerous developments to which this principle has given rise, the so-called "redox" fuel cell has proved to be particularly advantageous, because of the possibility of using inert electrodes, which generally avoids the use of expensive and expensive catalysts. whose lifespan is limited. In this type of cell, the electric current is produced by reduction reactions on the one hand and oxidation reactions on the other hand, in which is engaged at least one metal having several different electronic states.

The overall cost of a fuel cell depends in particular on the metal on which the operation of the cell is based. In this respect, an iron redox fuel cell is really attractive, because of the low cost of the reagents used.

- 2 -,,>

In the present application, a "fuel redox cell" is a fuel cell in which the iron is used at least in the anode compartment.

5 An iron redox battery consists of two compartments separated by a cation-type ion exchange membrane. In one of the compartments, which constitutes the cathode of the cell, a reaction of reduction of Fe into Fe takes place, while the other compartment, or anode, is the seat of an oxidation reaction of Fe ++ in +++ 10 Fe. The two compartments are connected to an external use circuit, which is thus traversed by an electric current as long as the two reactions can take place in the cell. In order to ensure the continuation of these reactions and therefore the persistence of the electric current, it is necessary to regenerate the solutions used as the reactive substances are consumed.

In this type of fuel cell, this regeneration is generally carried out purely by chemical means, in reactors 20 distinct from the cell itself.

It is common practice to regenerate the cathode solution using oxygen; this operation can be carried out under satisfactory economic conditions.

25

With regard to the regeneration of the anode solution, it is known to carry out this operation using hydrogen or carbon. However, the reduction reaction of Fe +++ by hydrogen is slow, due to the high potential of the Fe / Fe couple; it therefore requires the use of a catalyst, which increases the cost. Furthermore, carbon regeneration requires that the operation takes place at 150 - 200eC, and therefore under pressure, which is not favorable from an economic point of view.

The present invention provides a novel combustible material which overcomes the aforementioned drawbacks by ensuring rapid and economical regeneration of the anode solution of an iron fuel cell. It also relates to a method of using this combustible material, to a fuel cell using this material as well as to the applications of such a fuel cell.

5

According to the present invention, a combustible material for an iron redox element of a fuel cell is characterized in that it consists, at least in part, of an iron foil.

For the purposes of the present invention, the term “iron foil” is intended to mean a thin sheet of iron, preferably less than 100 μm thick, produced by any suitable means such as rolling or electroplating, and found in any form such as roll, flat or crumpled sheet, waste, scraps, etc.

15

According to a particular variant, the foil is coated with a layer of a hygroscopic substance, such as a gelatin; this substance can constitute a kind of sponge intended to serve as a reservoir for the solution to be regenerated; it also ensures a separation of the coils 20 of the foil and therefore good contact with the solution, in the case where the foil is in the form of a roll.

According to another variant of the invention, the foil is pierced with holes and it is wound in a roll, preferably compact, in such a way that at least part of these holes communicate from one turn to the other.

As indicated above, the iron foil is used, in accordance with the invention, to ensure the regeneration of the anode solution in an iron fuel cell of the redox type.

30

As is known, this regeneration consists of a reduction in +++ ++

Fe, produced in the anode compartment of the battery, into Fe which is then reintroduced into this anode compartment.

According to another aspect of the invention, a method of using iron foil in an iron redox fuel cell is characterized in that, * * - 4 - that a portion of the anodic solution of said is taken. cell, in that one puts this portion of solution in contact with said combustible material, in that one dissolves said combustible material in said portion of solution, in that one regenerates said portion of solution by reducing at least a portion of the ferric ions which it contains and in that said portion of regenerated solution is reintroduced into the fuel cell.

These operations are preferably carried out continuously, by circulating the solution successively through the anode compartment of the fuel cell and the regeneration reactor containing the iron foil.

According to the invention, the iron foil is dissolved in the solution to be regenerated, by effecting the reduction of the ferric ions in the solution by means of iron from faith 1, the excess ferrous ions are precipitated and eliminated said precipitate, in order to maintain the desired concentration of ferrous ions in the solution.

The precipitate thus recovered can, in turn, be used to manufacture the foil again, for example by electrolytic means.

In the context of the present process, solutions containing any iron salt may be used, provided that this salt is soluble in water.

However, it has proved particularly advantageous to use solutions of iron chlorides.

These chlorides indeed have a very high solubility and they therefore make it possible to use very concentrated solutions. In addition, the chlorine ions have a overriding effect which leads to an acceleration of corrosion, that is to say of the dissolution of the iron foil.

- 5 -

The solutions can also contain one or more inert salts, in particular NaCl. Such an addition, limited for example to 1% by weight, has the effect of reducing the internal resistance of the cell and of increasing the electric power supplied by the cell.

5

A further aspect of the invention relates to a fuel cell for implementing the above method.

In a known manner, such a cell comprises a cathode compartment, a circuit for regenerating the cathode solution, an anode compartment and a circuit for regenerating the anode solution. According to the invention, such a cell is further characterized in that the regeneration circuit of the anode solution comprises a reactor which contains a combustible material constituted at least in part by an iron foil.

According to an advantageous variant, this circuit also includes a device for adjusting the iron content of the anode solution. This device is preferably an apparatus for precipitating excess dental iron.

The various aspects of the invention will be seen more clearly and the invention will be able to be implemented more easily if reference is made to the more detailed description which follows. This description relates to a concrete embodiment of the invention, given by way of example; it is illustrated by the appended drawings, in which FIG. 1 recalls the principle of a redox fuel cell; and FIG. 2 represents a fuel cell in which the regeneration of the anode solution is ensured by the iron foil, in accordance with the present invention.

Figures 1 and 2 are of course only schematic representations, which include only the elements directly necessary for understanding the invention. Identical or analogous elements are designated by the same reference numerals in the two figures. Finally, the directions of circulation of fluids such as' '*' 1 - 6 - solutions, gases or electric current, as well as the directions of the various chemical reactions, are indicated by the arrows.

FIG. 1 shows the diagram of a redox fuel cell 5 of known type, the operation of which is based on the reactions of oxidation and reduction of iron.

The cell essentially consists of a cathode compartment 1, which contains a solution rich in Fe +++ ions, and an anode compartment 10 2, which contains a solution rich in Fe ++ ions. These two compartments are separated by a cation-exchange ion membrane 3. Such a membrane allows only X anions to pass; it prevents mixing of the solutions contained in compartments 1 and 2.

15

The electrodes 4, 5 which only serve as current collectors, are made of a material which is a good conductor of electricity, generally made of graphite. It is preferable to use a graphite felt or a metallic foam in order to increase the reaction surface and thus the power of the cell. These electrodes are connected to an external circuit of use symbolized by a lamp 6..

During the discharge of such a cell, the Fe +++ of cathode compartment 1 is reduced according to the reaction: +++ - ++ 25 Fe + e —Fe (1) while the Fe of anode compartment 2 is oxidized according to the reaction: _ ++ +++ -

Fe —► Fe + e (2).

The electron released to electrode 5 by reaction (2) passes through the external circuit and arrives at the other electrode 4 where it constitutes the electron necessary for the progress of reaction (1). The cell thus produces an electric current I usable at a voltage which depends on the relative concentrations of the two components Fe ++ and Fe +++ 35 in each compartment. The conservation of the neutrality of the electric charge requires the passage of an ion current in the solution; this current is produced by the migration of X anions through the exchange membrane 3.

. As the reactions progress, the concentration of 5 Fe ++ increases in compartment 1 and the concentration of Fe +++ increases in compartment 2. When the ratio of the Fe / Fe concentrations is equal in the two compartments, the electrical voltage becomes zero, the reactions stop and the electric current ceases to circulate in the external circuit.

10

To avoid interruption of the current produced by the cell, the solutions used in the cathode and anode compartments are regenerated respectively. These regeneration operations are carried out in reactors separate from the cell proper, respectively in the presence of oxygen in a reactor 7 for the cathode solution and in the presence of hydrogen or carbon in a reactor 8 for the anode solution. Under these conditions, the course of the reactions and the production of electric current continue as long as the regeneration of the solutions is ensured.

20

This description corresponds to the redox fuel cells which are currently well known.

FIG. 2 represents a redox fuel cell in which, according to the invention, iron foil is used to carry out the regeneration of the anodic solution. This cell also includes the known elements that are the cathode 1 and anode 2 compartments separated by an ion exchange membrane 3, as well as the collectors 4, 5 connected to an external circuit 6.

30

The regeneration of the cathode solution is carried out by means of oxygen in a reactor 7; a catalyst is provided here, consisting of platinum on activated carbon, to accelerate the reaction. Without departing from the scope of the invention, the cathode compartment of the fuel cell may contain a salt of a multivalent metal other than iron, or an oxidizing material other than oxygen; we can in particular use materials having an oxidizing effect such as chlorine, certain chlorine compounds (bleach), permanganate, peroxodisulfates, etc. Likewise, this cathode compartment can be that of a conventional battery. Regeneration with oxygen, and in particular with oxygen from the air, is particularly advantageous in the case where the battery is used to ensure the electric propulsion of a vehicle.

The essential characteristic of the invention resides in the fact that the fuel used for the regeneration of the anode solution is iron foil 9.

Under these conditions, the regeneration of the cathode solution is carried out according to the reaction: 15 4 Fe ++ + 02 + 4 H + - 4 Fe +++ + 2 H20 (3) while the regeneration reaction of the anode solution is written: 2 Fe +++ + FeQ —► 3 Fe ++ (4).

The dissolution of faith 1 following reaction (4) enriches the anode solution with ferrous ions, which become surplus compared to ferric ions. The required concentration of ferrous ions is maintained, for example by precipitating the excess by the reaction Fe ++ + 2 H 2 O - ► Fe (0H> 2 {+ 2 H + (5).

In this case, reaction (5) regenerates the acidity (H +) consumed by reaction (3) because H + ions can cross the exchange membrane 3, due to their small dimensions.

30

In FIG. 2, the regeneration circuit for the anode solution comprises a precipitation device 10, where precipitation and removal of excess ferrous ions in the solution is carried out periodically or continuously.

The circulation of the cathode and anode solutions in their respective regeneration circuit is ensured by the pumps 11, 12.

35 "I‘ 1 - 9 -

In addition, the cathode 1 and anode 2 compartments are lined with a conductive material constituted here by carbon felt; they thus form electrodes having a very large specific surface and therefore making it possible to collect currents of high intensity. 5 It is possible, without departing from the scope of the invention, to use electrodes made of various materials having a large specific surface, provided that they are electrically conductive and chemically inert with respect to the solutions used in these compartments . This is particularly the case for carbon or graphite foam, as well as for the foam of certain metals and metal alloys. With this type of electrodes, all of the solution from one compartment is pumped through the pores of the corresponding electrode and therefore does not flow from the collector to the membrane.

The regeneration reactor 8 contains faith 1 of iron 9, here presented in the form of a roll, the turns of which are not tight. This form is particularly interesting because it has a very large contact surface with the solution, which promotes the dissolution of the foil and therefore the regeneration of the solution.

The use of the iron foil to regenerate The anodic solution of such a fuel cell has several advantages.

The very small thickness of the foil makes it possible to have a very large contact surface in a limited volume; reactor 8 can therefore have relatively small dimensions while exhibiting an attractive yield.

The foil may be of poor quality and have defects such as pitting, holes, tears, etc .; it can be in the form of waste, scrap, filings, or others without compromising the yield of regeneration.

The precipitate of Fe (OH ^ collected at 10 can be recycled for the production of foils.

> - 10 -

A fuel cell consuming iron foil in accordance with the present invention can be used in the most diverse applications, such as propulsion of vehicles, lighting or heating of premises, powering of electric motors, etc.

5

It should also be emphasized that the use of the combustible material proposed by the present invention does not cause any pollution of the environment, which is particularly important in the field of vehicle propulsion.

The example which follows shows the advantage of using such a fuel cell for the propulsion of a motor vehicle by means of a 60 kW engine.

15 In the case of an internal combustion engine, consumption at full power would be around 4.8 g / s, taking into account an energy power of 10,000 kcal / kg for petrol as well as a average yield of 30%. This corresponds substantially to a consumption of 13 l of petrol per 100 km, at full power and at high speed.

20

In the case of an electric motor, the efficiency is close to 100%. To achieve the power of 60 kW using 100 1.5 V / 400 A cell elements, the maximum power consumption is 23 g / s of transformed iron in the entire cell. As the regeneration of 2 -J- + 4 * 25 g of Fe requires only 1 g of iron, the consumption of such an engine amounts to 11.6 g / s of foil, i.e. 2.4 times the weight gasoline.

As a result, 78 kg of foil can provide the same autonomy as 33 kg of gasoline. However, the 78 kg of foil only requires a tank of approximately 15 l, while the 33 kg of petrol require a tank of 41 l. The gain in volume is particularly appreciable.

Claims (13)

1. Ferrous combustible material for an element of a fuel cell, characterized in that it is constituted at least in part by url faith l of iron. *> * - 11 - 2. Combustible material according to claim 1, characterized in that the iron foil is coated with a hygroscopic substance. 3. Combustible material according to claim 1 or 2, characterized in that the foil is pierced with holes and in that it is wound in a roll so that at least part of these holes communicate from a turn to the other. 4. Method of using a combustible material according to either of claims 1 to 3 in an iron redox element of a fuel cell, characterized in that a portion of the anode solution of said cell, in that this portion of solution is brought into contact with said combustible material, in that one dissolves said combustible material in said portion of solution, in that one regenerates said portion of 20 solution by reducing at least a portion of the ferric ions it contains and in that said portion of regenerated solution is reintroduced into the fuel cell. 5. Method according to claim 4, characterized in that the content of iron ions in said portion of regenerated anode solution is adjusted. 6. Method according to either of Claims 4 and 5, characterized in that the said anodic solution is an aqueous solution of at least one set of iron such as a sulphate or a chloride. 7. Method according to either of claims 4 to 6, characterized in that said anodic solution contains at least one inert salt, such as NaCl. "Γ - 12 - *," 8. Fuel cell for implementing the method of either of claims 4 to 7, comprising a cathode compartment, a circuit for regenerating the cathode solution, an anode compartment and a circuit for regenerating the anodic solution, characterized in that the regeneration circuit of the anodic solution comprises a reactor which contains a combustible material constituted at least in part by an iron foil. 9. Fuel cell according to claim 8, characterized in that the regeneration circuit of the anodic solution comprises a device for adjusting the iron ion content of said anodic solution. 10. Fuel cell according to either of claims 8 15 and 9, characterized in that the cathode compartment contains a salt of at least one multivalent metal other than iron. 11. Fuel cell according to either of claims 8 to 10, characterized in that the cathode compartment contains a material exerting an oxidizing effect other than oxygen. 12. Fuel cell according to either of claims 8 to 11, characterized in that at least one of the electrodes is made at least partially of a material having a large specific surface, such as a foam. graphite, carbon, metal or metal alloy. 13. Use of a fuel cell according to either of claims 8 to 12, for the supply of an electric motor 30 intended for the propulsion of a vehicle.