System And Method For Extracting Oxygen From Powdered Metal Oxides

Abstract

A system for extracting oxygen from powdered metal oxides, the system comprising a container comprising an electrolyte in the form of meltable or molten salt, at least one cathode, at least one anode, a power supply, and a conducting structure, wherein the cathode is shaped as a receptacle having a porous shell, which has an upper opening, the cathode being arranged in the electrolyte with the opening protruding over the electrolyte, wherein the conducting structure comprises a plurality of conducting elements and gaps between the conducting elements, wherein the power supply is connectable to the at least one cathode and the at least one anode to selectively apply an electric potential across the cathode and the anode, wherein the conducting structure is insertable into the cathode, such that the conducting elements reach into an inner space of the cathode, wherein the conducting structure is electrically connectable to the cathode, and wherein the system is adapted for reducing at least one respective metallic species of at least one metal oxide of feedstock inside the shell of the cathode with inserted conducting structure by applying the electric potential, wherein the potential is greater than the dissociation potential of the at least one metal oxide.

Claims

1. A system for extracting oxygen from powdered metal oxides, the system comprising: a container comprising an electrolyte, at least one cathode, at least one anode, a power supply, and a conducting structure, wherein the cathode is shaped as a receptacle having a porous shell, which has an upper opening, the cathode being arranged in the electrolyte with the opening protruding over the electrolyte, wherein the conducting structure comprises a plurality of conducting elements and gaps between the conducting elements, wherein the power supply is connectable to the at least one cathode and the at least one anode to selectively apply an electric potential across the cathode and the anode, wherein the conducting structure is insertable into the cathode, such that the conducting elements reach into a receiving space of the cathode, wherein the conducting structure is electrically connectable to the cathode, and wherein the system is adapted for reducing at least one respective metallic species of at least one metal oxide of feedstock inside the shell of the cathode with inserted conducting structure by applying the electric potential, wherein the potential is greater than the dissociation potential of the at least one metal oxide.

2. The system of claim 1, wherein the conducting structure comprises a wire mesh.

3. The system of claim 1, wherein the conducting structure comprises a plurality of pins arranged at a distance to each other.

4. The system of claim 1, wherein the electrolyte comprises a meltable or molten salt.

5. The system of claim 4, wherein the electrolyte comprises a halide salt.

6. The system of claim 1, wherein the anode comprises at least one selective oxygen pump.

7. The system of claim 6, wherein the oxygen pump comprises yttria-stabilized zirconia.

8. The system of claim 1, further comprising a cover, which is designed for covering a top opening of the container, thereby enclosing a seal with the top opening.

9. Method for extracting oxygen from powdered metal oxides through an electrolysis cell comprising a container, at least one cathode shaped as a receptacle having a porous shell with an upper opening, and at least one anode, the method comprising: providing an oxygen ion conducting electrolyte powder into the container, such that the electrolyte surrounds the shell of the cathode at least partially, inserting a conducting structure having a plurality of conducting elements and gaps between the conducting elements into the cathode, such that the conducting elements reach into a receiving space of the cathode, electrically connecting the conducting structure to the cathode, providing a feedstock comprising at least one metal oxide in powdered form into the upper opening of the at least one cathode, and applying an electric potential across the cathode and the anode, the cathode being in communication with the electrolyte and the anode being in communication with the electrolyte and the feedstock, such that at least one respective metallic species of the at least one metal oxide is reduced at the cathode and oxygen is oxidized at the anode to form molecular oxygen, wherein the potential across the cathode and the anode is greater than the dissociation potential of the at least one metal oxide.

10. The method of claim 9, wherein the feedstock comprises at least one of a group of materials or a chemical compound comprising at least one of the group of materials, the group consisting of: iron, titanium, regolith.

11. The method of claim 9, wherein the electrolyte comprises a meltable or molten salt, in particular a halide salt.

12. The method of claim 9, wherein the anode comprises at least one selective oxygen pump, in particular yttria-stabilized zirconia

13. The method of claim 9, wherein the electrolysis cell is operated at a temperature greater than about 500° C.

14. The method of claim 9, wherein the electrolysis cell is operated at a temperature in the range of about 500° C. to about 1400° C.

15. The method of claim 9, further comprising collecting molecular oxygen at the anode.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0037] In the following, the attached drawings are used to illustrate exemplary embodiments in more detail. The illustrations are schematic and not to scale. Identical reference numerals refer to identical or similar elements. They show:

[0038] FIG. 1 a simplified schematic view of the system in an embodiment of the system,

[0039] FIG. 2 a simplified schematic view of the system in another embodiment of the system, and

[0040] FIG. 3 a method in a block-oriented, schematic view.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0041] FIG. 1 shows a system 2 for extracting oxygen from powdered metal oxides in a schematic view. The system 2 comprises a container 4, in which an electrolyte 6 in the form of a molten salt is provided. The molten salt may be any suitable molten salt used for electrolytic reduction. For example, the salt may be a halide salt, a suitable mixture of calcium fluoride, magnesium fluoride, and yttrium fluoride, or a calcium chloride salt comprising a portion of calcium oxide.

[0042] A cathode 8, which has a cup shape, comprises a porous shell 10 and an upper opening 12. Inside the shell 10, a receiving space 14 is defined, which holds a feedstock 16 in the form of a metal oxide powder to be reduced. The metal oxide powder may comprise any suitable metal oxide. A number of metal oxides have been reduced using direct electrolytic processes such as the SOM process or FFC process and are known in the prior art, for example, titanium oxide or tantalum oxide.

[0043] An anode 18 is arranged in the electrolyte 16. Both the anode 18 and the cathode 8 are connected to a power supply 20 to apply a potential between the cathode 8 and its associated metal oxide on the one hand and the anode 18 on the other hand. Furthermore, a conducting structure 22 in the form of a wire mesh is inserted into the receiving space 14 of the cathode 8 and is in electrical contact with the cathode 8. The conducting structure 22 is in contact with and surrounded by the feedstock 16. When a potential is applied across the anode 18 and the cathode 8, the conducting structure 22 in addition to the shell 10 acts as a cathode. The active surface of the cathode 8 is thus enlarged. Hence, the surface area where the reduction reaction takes place is enlarged, which results in the reduction of a higher quantity of metal oxide and therefore more oxygen production per time. Furthermore, an average distance between the cathode 8 and the metal-oxide 16 is reduced, which results in a faster reduction process.

[0044] The container 4 comprises a top opening 24 at an upper surface, through which the interior space of the container 4 is accessible. The top opening 24 is coverable by a cover 26. For sealing the interior space, a suitable, chemically resistant seal 28 is arranged between the top opening 24 and the cover 26. The container may comprise any suitable chemically resistant material, such as a stainless steel or a ceramic.

[0045] FIG. 2 shows a modified system 30 for extracting oxygen from powdered metal oxides. Here, instead of a wire mesh, a conducting structure 32 in the form of a plurality of pins is provided, which are attached to a common plate 34. The plate 34 covers the upper opening 12 of the cathode 8 and encloses a conducting seal element 36 with the upper opening 12.

[0046] An anode 38 is provided, which comprises at least one selective oxygen pump 40. The oxygen pump 40 comprises a solid electrolyte membrane, e.g. a zirconium oxide element, which is provided for a selective transfer of oxygen from the receiving area, i.e. outside the anode 38, into a pumping space, i.e. an interior of the anode 38. The zirconium oxide ceramic is stabilized, in particular with other oxides, such as calcium oxide (CaO), magnesium oxide (MgO) and/or yttrium oxide (Y2O3). However, it may comprise any elements which appear useful to a person skilled in the art. For example an element comprising titanium oxide, vanadium oxide, niobium oxide or perovskite, or a combination of the named oxides may be used. The respective oxides may in each case in turn be stabilized by another oxide.

[0047] The anode 38 may comprise liquid silver 39 to serve as a medium to carry out a charge-transfer reaction at the interface between the liquid silver and the membrane. Oxygen, which enters the liquid silver anode through the oxygen-ion-conducting membrane, evolves as oxygen gas, since silver oxide is not stable at the operating temperature. Silver has low vapor pressure, high oxygen solubility and high oxygen diffusivity in this temperature range. Other oxygen-producing anodes 38 may be used if they are stable under the oxidizing conditions of the anode 38.

[0048] FIG. 3 shows a method for extracting oxygen from powdered metal oxides through an electrolysis cell comprising a container, at least one cathode shaped as a receptacle having a porous shell with an upper opening, and at least one anode as described above. The method comprises providing 42 an oxygen ion conducting electrolyte powder into the container, such that the electrolyte surrounds the shell of the cathode at least partially, inserting 44 a conducting structure having a plurality of conducting elements and gaps between the conducting elements into the cathode, such that the conducting elements reach into a receiving space of the cathode, electrically connecting 46 the conducting structure to the cathode, providing 48 a feedstock comprising at least one metal oxide in powdered form into the upper opening of the at least one cathode, and applying 50 an electric potential across the cathode and the anode, the cathode being in communication with the electrolyte and the anode being in communication with the electrolyte and the feedstock, such that at least one respective metallic species of the at least one metal oxide is reduced at the cathode and oxygen is oxidized at the anode to form molecular oxygen. As mentioned above, the potential across the cathode and the anode is greater than the dissociation potential of the at least one metal oxide. The method may further comprise collecting 52 molecular oxygen at the anode.

REFERENCE NUMERALS

[0049] 2 system for extracting oxygen

[0050] 4 container

[0051] 6 electrolyte

[0052] 8 cathode

[0053] 10 porous shell

[0054] 12 upper opening

[0055] 14 receiving space

[0056] 16 feedstock

[0057] 18 anode

[0058] 20 power supply

[0059] 22 conducting structure (wire mesh)

[0060] 24 top opening

[0061] 26 cover

[0062] 28 seal

[0063] 30 system for extracting oxygen

[0064] 32 conducting structure (pins)

[0065] 34 plate

[0066] 36 seal element

[0067] 38 anode

[0068] 39 liquid silver

[0069] 40 oxygen pump

[0070] 42 providing electrolyte powder

[0071] 44 inserting conducting structure

[0072] 46 electrically connecting the conducting structure

[0073] 48 providing feedstock

[0074] 50 applying an electric potential

[0075] 52 collecting molecular oxygen