Patent Application
20070141430
Embodiments of the invention relate to a gas scrubber for use in a fuel cell or battery. Particularly, embodiments relate to gas scrubber for use in a rechargeable fuel cell or metal/air battery.
A fuel cell may convert the chemical energy of a fuel directly into electricity without any intermediate thermal or mechanical processes. Energy may be released when a fuel reacts chemically with oxygen in the air. A fuel cell may convert hydrogen and oxygen into water. The conversion reaction occurs electrochemically and the energy may be released as a combination of electrical energy and heat. The electrical energy can do useful work directly, while the heat may be dispersed.
Fuel cell vehicles may operate with hydrogen stored onboard the vehicles, and may produce little or no conventional undesirable by-products. The byproducts may include water and heat. Systems that rely on a reformer on board to convert a liquid fuel to hydrogen may produce small amounts of emissions, depending on the choice of fuel. Fuel cells may not require recharging, as an empty fuel canister could be replaced with a new, full fuel canister.
Metal/air batteries may be compact and relatively inexpensive. Metal/air cells include a cathode that uses oxygen as an oxidant and a solid fuel anode. The metal/air cells differ from fuel cells in that the anode may be consumed during operation. Metal/air batteries may be anode-limited cells having a high energy density. For example, metal/air batteries have been used in hearing aids and in marine applications.
Alkaline fuel cells, rechargeable fuel cells and metal/air batteries can be sensitive to carbon dioxide in the air due to the use of base electrolytes. The interaction of base electrolyte, and/or the electrodes with carbon dioxide, may cause formation of unwanted byproducts that may interfere with the operation and life of the cell. Currently available carbon dioxide scrubbers may require maintenance and may rely on limited or expendable materials/mechanisms to remove the carbon dioxide.
It may be desirable to have a fuel cell and/or a metal/air battery having differing characteristics or properties than those currently available.
The embodiments of the invention relate a galvanic cell utilizing a gas scrubber. The galvanic cell may include a galvanic cell unit and a gas scrubber comprising an active material layer, a resistance coil in contact with the active material layer, a first shutter positioned between the active material layer and ambient air, and a second shutter positioned between the galvanic cell unit and the active material layer.
Further, embodiments of the invention relate to a gas scrubber comprising an active material layer, a resistance coil in contact with the active material layer, a first shutter positioned between the active material layer and ambient air, a galvanic cell unit, and a second shutter positioned between the galvanic cell unit and the active material layer.
Embodiments of the invention relate to a method of making a galvanic cell. The method may include forming a galvanic cell unit, and forming a gas scrubber, including coupling an active material layer to a resistance coil, positioning a first shutter between the active material layer and ambient air, and positioning a second shutter between the galvanic cell unit and the active material layer.
In addition, embodiments of the invention relate to a method of making a gas scrubber. The method may include forming an active material layer, forming a resistance coil, coupling the resistance coil to the active material layer, forming a first shutter, positioning the first shutter between the active material layer and ambient air, forming a galvanic cell unit, forming a second shutter, and positioning the second shutter between the galvanic cell unit and the active material layer.
Embodiments of the invention also relate to a method of scrubbing. The method may include opening both shutters sufficient to allow ambient air or oxygen to diffuse and come in contact with an active material layer. Sorption of the carbon dioxide, with the active material located within the active material layer, allows the substantially pure air or oxygen to diffuse and come in contact with a galvanic cell unit. The active material layer can be thermally regenerated by closing the second shutter and heating the active material layer through resistive heat or other heat generating methods.
Embodiments of the invention may be understood by referring to the following description and accompanying drawings that illustrate such embodiments. In the drawings:
Embodiments of the invention may relate to a gas scrubber for use in a fuel cell or battery. In one embodiment, a gas scrubber for use in a rechargeable fuel cell or metal/air battery is provided.
References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one of ordinary skill in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term such as “about” is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value.
As used herein, the term membrane refers to a selective barrier that permits passage of hydroxide ions generated at the cathode through the membrane to the anode for oxidation of hydrogen at the anode to form water and heat. The terms anode and anodic electrode refer to an electrode that may be fabricated from metal hydride materials such as LaNi5 and TiNi types of alloys. The terms cathode and cathodic electrode refer to an electrode that may be fabricated from metal or metal oxides and may include a catalyst. At the cathode or cathodic electrode, oxygen from air is reduced by free electrons from the usable electric current, generated at the anode, that combine with water, to form hydroxide ions and heat. The cathode in the fuel cell embodiments described herein, is, for some embodiments, graphite, and carbon-based materials. Suitable fuels cell may include a rechargeable fuel cell, an alkaline fuel cell, or a metal/air battery.
In the drawings, like numerals describe substantially similar components throughout the several views. These embodiments are described in sufficient detail to enable one of ordinary skill in the art to practice the invention.
One embodiment of the invention, illustrated generally in
A first shutter support layer 17 provides a first shutter 15 that is adjacent to ambient air 23. The first shutter 15 controls access and flow of air or oxygen into and out of the device. An active material layer 9 is positioned below or underneath the first shutter support layer 17. The active material layer 9 may include an active material that can chemically or physically bind the gas to be isolated, such as carbon dioxide. The active material layer 9 is coupled to a resistance coil 11 that can be thermally or electrically activated to reverse the binding of the target gas, such as the release of bound carbon dioxide. The resistance coil 11 may also be fitted with a temperature control 13. A second shutter support layer 5 may include a second shutter 7, which controls the access and flow of the filtered air or oxygen to a galvanic cell unit 3. Pure oxygen generated during the charging process can help to release the bound carbon dioxide from the active material. Gaskets 25 and through bolts 21 support the components of the device within a housing 19. The positioning and control of the shutters, and the choice or selection of active materials, may allow for management of potentially disrupting target gases. Target gases may include one or more of carbon dioxide, sulfur oxides, or nitrogen oxides. Air or oxygen may be scrubbed of the target gas prior to contact with the electrolyte, and/or the electrodes, of the galvanic cell unit 3. The thermal or electric control of the resistance coil 11 may allow regeneration of the active materials of the active material layer 9. Such control may reduce or eliminate periodic maintenance, such as the replacement and/or replenishment of active materials.
The active material layer 9 may include one or more active materials that are capable of chemically and/or physically binding a target gas. Suitable active materials may include one or more of amines, amidines, or polymers or composites that include such nitrogen-based functionality and the like. Copolymers and blends of the active molecules or polymers can also be utilized in the invention. In one embodiment, the active material may include one or more of an amine, a pyrimidine, or an amide functional group.
Suitable amines may include one or more alkyl ethanolamine. Suitable alkyl ethanolamine may include one or more of triethanolamine (TEA), monoethanolamine (MEA), diethanolamine (DEA), or methyl diethanolamine (MDEA). Other suitable amines may include propanolamines, or other longer chain alkanes having a hydroxyl functionality and an amine functionality. Both primary and secondary amines may be utilized. In one embodiment, the active material may include polyamine functionality. Suitable amines may be commercially obtained at Dow Chemical (Midland, Mich.). Unless specified otherwise, all ingredients are commercially available from such common chemical suppliers as Alpha Aesar, Inc. (Ward Hill, Mass.), Sigma-Aldrich Company (St. Louis, Mo.), and the like.
Suitable amidines may include one or more of 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU), tetrahydropyrimidine (THP), N-methyltetrahydropyrimidine (MTHP), or polystyrene, polymethacrylate, polyacrylate etc., modified by DBU, THP or MTHP for example. In one embodiment, the amidine may include one or more of a bis-amidine, tris-amidine, or tetra-amidine, or a salt of any of these.
In one embodiment, the active polymer may be produced through radical polymerization, cationic polymerization, anionic polymerization, group transfer polymerization, ring-opening polymerization, ring-open metathesis polymerization, coordination polymerization, condensation polymerization, etc. The active polymer may be also produced by modification of a premade polymer structure using suitable active molecules. In one embodiment, the amidine may include a compound having the general formula X—Y(Z)n. In this formula, X is a moiety of:
wherein each R is, independently, H, an optionally substituted alkyl, alkenyl, aryl, alkaryl, or alkenylaryl group, Y is a bond or a linking group, Z is H or a moiety according to Formula I, which may be the same or different than X, and n is an integer from 1 to 3.
Alkyl means an aliphatic hydrocarbon group that may be linear or branched having from 1 to about 15 carbon atoms, in some embodiments 1 to about 10 carbon atoms. Branched means that one or more lower alkyl groups such as methyl, ethyl, or propyl are attached to a linear alkyl chain. Lower alkyl means having 1 to about 6 carbon atoms in the chain, which may be linear or branched. One or more halo atoms, cycloalkyl, or cycloalkenyl groups may be a substitute for the alkyl group.
Alkenyl means an aliphatic hydrocarbon group containing a carbon-carbon double bond and which may be straight or branched having 2 to about 15 carbon atoms in the chain. Preferred alkenyl groups have 2 to about 10 carbon atoms in the chain, and more preferably 2 to about 6 carbon atoms in the chain. Lower alkenyl means 2 to about 4 carbon atoms in the chain, which may be straight or branched. The alkenyl group may be substituted by one or more halo atoms, cycloalkyl, or cycloalkenyl groups. Cycloalkyl means a non-aromatic mono- or multicyclic ring system of about 3 to about 12 carbon atoms. Exemplary cycloalkyl rings include cyclopentyl, cyclohexyl, and cycloheptyl. The cycloalkyl group may be substituted by one or more halo atoms, methylene, alkyl, cycloalkyl, heterocyclyl, aralkyl, heteroaralkyl, aryl or heteroaryl. Hetero means oxygen, nitrogen, or sulfur in place of one or more carbon atoms. Cycloalkenyl means a non-aromatic monocyclic or multicyclic ring system containing a carbon-carbon double bond and having about 3 to about 10 carbon atoms. The cycloalkenyl group may be substituted by one or more halo atoms, or methylene, alkyl, cycloalkyl, heterocyclyl, aralkyl, heteroaralkyl, aryl, or heteroaryl groups.
Aryl means an aromatic carbocyclic radical containing about 6 to about 12 carbon atoms. Exemplary aryl groups include phenyl or naphthyl optionally substituted with one or more aryl group substituents which may be the same or different, where “aryl group substituent” includes hydrogen, alkyl, cycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, aralkyl, aralkenyl, aralkynyl, heteroaralkyl, heteroaralkenyl, heteroaralkynyl, hydroxy, hydroxyalkyl, alkoxy, aryloxy, aralkoxy, carboxy, acyl, aroyl, halo, nitro, cyano, carboxy, alkoxycarbonyl, aryloxycarbonyl, aralkoxycarbonyl, acylamino, aroylamino, alkylsulfonyl, arylsulfonyl, and other known groups. Alkaryl means an aryl-alkyl-group in which the aryl and alkyl are as previously described. Alkenylaryl means an aryl-alkenyl-group in which the aryl and alkenyl are as previously described.
In the general formula X—Y(Z)n, Y can be a bond or a linking group R′, which may be, or include, a hetero-atom such as oxygen, sulfur, phosphorous, or nitrogen, and the like. The linking group R′ may be an alkyl, alkenyl, aryl, or alkaryl group having from 1 to about 15 carbon atoms, which may be linear or branched, and which may be non-fluorinated, fluorinated, or perfluorinated. n is greater than 1. In one embodiment, the amidine may include one or more carboxylate salts of an amidine, which amidine and/or salt optionally can be fluorinated or perfluorinated.
The carbon dioxide may react with the active materials to form such products as zwitterions adducts and ammonium carbamate, for example. Active materials may be selected based on the ability to physically bind a target gas, which if carbon dioxide may include carbon fiber compounds and their composites. For example, carbon fiber composite molecular sieve (CFCMS) can adsorb carbon dioxide. Other suitable materials for physical binding of a target gas may include carbon nanotubes, buckyballs or fullerenes, porous ceramics, zeolites, and the like.
Such active materials can adsorb carbon dioxide in low temperatures during the discharge process of the galvanic cell unit 3 by either a chemical reaction, physical adsorption or both. The active materials can be regenerated within the active material layer 11 by applying a thermal treatment in the range of greater than about 65 degrees Celsius to the resistance coil during the charge period of the galvanic cell unit 3. In one embodiment, the thermal treatment may be less than about 120 degrees Celsius. Further, the temperature range may be from about 65 degrees Celsius to about 80 degrees Celsius, from about 80 degrees Celsius to about 100 degrees Celsius, from about 100 degrees Celsius to about 110 degrees Celsius, or from about 110 degrees Celsius to about 120 degrees Celsius. Alternatively or additionally, applying a low voltage to the resistance coil may regenerate the active materials.
Referring to
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Referring to
Referring to
(C2H4OH)3N+CO2+H2O(C2H4OH)3NH++HCO3−
The reaction has a theoretical fixing efficiency of 29.5%.
Referring to
Referring to
The embodiments described herein are examples of compositions, structures, systems and methods having elements corresponding to the elements of the invention recited in the claims. This written description may enable one of ordinary skill in the art to make and use embodiments having alternative elements that likewise correspond to the elements of the invention recited in the claims. The scope thus includes compositions, structures, systems and methods that do not differ from the literal language of the claims, and further includes other compositions, structures, systems and methods with insubstantial differences from the literal language of the claims. While only certain features and embodiments have been illustrated and described herein, many modifications and changes may occur to one of ordinary skill in the relevant art. The appended claims are intended to cover all such modifications and changes.
