Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing nonmetal element
Reexamination Certificate
2000-02-14
2001-07-24
Bell, Bruce F. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing nonmetal element
C205S635000, C205S636000, C204S252000, C204S265000, C204S266000, C204S272000
Reexamination Certificate
active
06264820
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is concerned with improvements in and relating to gas generators, particularly, but not exclusively, for the generation of oxygen.
2. Present State of the Art
Gas generators are used in a wide variety of applications to produce or separate gases for breathing, to provide gases for chemical reactions, to separate chemical compounds into their component parts of for other purposes. Such generators are used by pilots and medical establishments, amongst other users.
Gas generators should ideally provide a high gas flow rate, with maximum efficiency and at as low an operating temperature as possible. Existing technology faces problems in one or more of these areas and the present invention aims to provide an improved gas generator.
BRIEF SUMMARY OF THE INVENTION
According to a first aspect of the invention we provide a gas generator comprising a layer of a first material and provided with a layer of a second material on one surface and a layer of a third material on the other opposing surface, the application of an external potential resulting in a flow of gas from one side of the generator to another.
The flow of gas from one side to the other results in gas being generated or separated to one side of the generator. The flow through the material generally occurs in ionic form with discharge to gas at the exhausting side.
Preferably the first material is an electrolyte material. The first material may be ionically conducting. The first material may comprise zirconia. The first material may be doped with one or more other materials, for instance rare earth metals. The additional material, for instance yttria, may stabilise one or more of the other constituents of the first material. Zirconia doped with yttria forms a particularly preferred form for the first material. The first material may include 3 to 12 mol % and/or % by weight, of a doping agent, with 6 to 10 mol % and/or % by weight being preferred.
The second and third materials may be different or the same. Preferably the second and/or third materials are mixed conductors, most preferably for both electrons and ions of the gas, for instance oxygen. Preferably the second and/or third materials provide the principal electrode function for the generator.
Preferably the second and/or third materials are stable in an oxidising and reducing environment. A material comprising a ceramic oxide is preferred. Preferably the second and/or third materials comprise urania. Doped urania, for instance by one or more rare earth metals, is particularly preferred.
Urania doped with yttria may be provided. The urania may be provided as a solid solution with a further material. The further material may comprise one or more rare earth metals, such as yttria.
The urania may be depleted urania i.e. the U
235
content may be less than for naturally occurring urania.
The second and/or third material may be provided in a layer less than 150 micrometers and more preferably less than 100 micrometers thick.
One or more further layers may be provided on the second and/or third materials. The layer or layers may provide a current collecting and/or current distributing function for the generator.
The material on one of the second or third materials may comprise nickel oxide and/or zirconia. A mixed system, for instance in cermet form, is preferred.
The material on the second and/or third materials may comprise a cobalt and/or manganese oxide and/or oxide and/or perovskite system. Mixed oxide systems, such as lanthanum, strontium, cobalt, iron and manganese oxides are preferred. The material may particularly be formed of lanthanum strontium manganese cobaltite.
The external potential may arise from a chemical or activity difference between the materials adjoining the two sides of the gas generator. The activity or chemical difference may arise from one or more of, a difference in the level and/or temperature and/or state and/or pressure of one or more species and/or different species.
The anode side and cathode side of the generator are preferably electrically connected to one another by a circuit, for instance an external circuit. The circuit may be used to control the flow of electrons and/or ions generated by the external potential and/or may be used to apply the external potential, for instance from a power source.
The external potential may arise from a voltage or electrical potential applied or generated across the generator. The potential may arise from an external power source connected to one or more of the materials forming the gas generator. An electrical circuit connecting anode and cathode sides of the generator may be used.
One or both sides of the generator may be maintained in contact with a given batch of gas and/or vapour. One side may be depleted and the other enhanced in one or more gas levels in such a batch process. Alternatively one or both sides of the generator may be contacted with a changing volume of gas. The gas on one or both sides may periodically or constantly be replaced. In this continuous system the gas level on one side is improved by selective transfer of a component into it, whilst the gas level on the other side is reduced in that component so effectively increasing the level and/or purity of the other component on that side.
Preferably the external potential results in a flow of electrons through the first material. The electrons may flow, for instance via an external circuit, from the second material to the third, or vice versa. The ionic flux in the first material may complete the circuit. This may occur for instance in an activity or a chemical potential driven system. The ions electrons may flow from a layer on the second material via the first and third materials to a layer on the third material, or vice versa. This may occur where an electrical potential is applied across the generator.
Preferably the external potential results in a flow of gas ions through the first material from one side to another preferentially. The gas ions may flow from the second material to the third, or vice versa, via the first material. Preferably the gas ions reform gas molecules on reaching the second or third material. Preferably the gas molecules are exhausted to the volume surrounding the second or third material. Preferably the first material acts as a barrier to other materials, gases, ions in the feed.
The gas ions may be formed by the decomposition of a compound in contact with the second and/or third materials and/or layers present thereon. The compound decomposed may be water. The water may be in gaseous and/or vapour form. The decomposition may occur within the second and/or third layer. Preferably the layers on the second and third materials are different in such a case.
The gas ions may be formed by the decomposition of a gas molecule in contact with the second and/or third materials and/or layers present thereon. The molecule decomposed may be O
2
. The decomposition may occur within the second and/or third layer. Preferably the layers on the second and third materials are the same in such a case.
The gas generated and/or purified and/or increased in concentration is preferably oxygen. The oxygen may be extracted from water. The gas may be extracted and/or purified and/or increased in concentration from air.
The gas generator may be formed of a plurality of generator elements of the type described. The generator elements may be provided in substantially planar form, for instance as a series of planar layers of the various materials. Square, rectangular or elongate elements may be provided.
In an alternative form one side layer may form the inner surface of a cylinder or other element with a central passage, the other layers being provided about the inner layer. In such a case the inner passage forms one side and the outer side the other side of the generator element. The layers may be provided in a concentric manner, for instance to form layers on a right cylinder or non-circular or non-regular cross-sections may be provided.
According to a second aspec
Barnett Stephen Vernon
Brace Christopher William
Ince Andrew Timothy
Lewin Robert Glyn
Middleton Peter Hugh
Bell Bruce F.
British Nuclear Fuels PLC
Workman & Nydegger & Seeley
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