SOLIDIFYING METALS OR METALLOIDS FROM A LIQUID CATHODE DURING MOLTEN OXIDE ELECTROLYSIS

Abstract

A method and system for precipitating a solid using molten oxide electrolysis are presented. Using an electrical current for electrolysis in a first vessel, an oxide material is heated to form a liquid cathode. The first vessel also includes a corresponding anode. A portion of the liquid cathode is received into a second vessel that is separated from the first vessel by a conduit. The portion of the liquid cathode is allowed to cool. Precipitate of the cooled liquid cathode may then be collected in the second vessel. The precipitate may be a metal or metalloid, such as silicon. The method and system allow for continuous processing for production of a precipitate material, in contrast to batch processing of other methods or systems. For example, precipitate may be harvested from the second vessel while electrolysis is continuously performed in the first vessel.

Claims

1. A method for precipitating a solid using molten oxide electrolysis, the method comprising: via an electrical current, producing electrolysis in a first vessel containing a melted oxide material that includes a liquid cathode; receiving a portion of the liquid cathode into a second vessel that is separated from the first vessel via a conduit, which conveys the portion of the liquid cathode from the first vessel; allowing the portion of the liquid cathode to cool; and collecting a precipitate of the cooled liquid cathode in the second vessel.

2. The method of claim 1, wherein the precipitate of the cooled liquid cathode is a metal or metalloid.

3. The method of claim 2, wherein the metalloid is silicon.

4. The method of claim 1, wherein the oxide material is a mixture of two or more metallic oxides.

5. The method of claim 1, wherein allowing the portion of the liquid cathode to cool comprises at least partially controlling heat transfer of the flow of the portion of the liquid cathode in the conduit or the second vessel.

6. The method of claim 1, further comprising controlling the temperature of the portion of the liquid cathode in the second vessel to produce a vertical thermal gradient.

7. The method of claim 1, wherein collecting the precipitate of the cooled liquid cathode in the second vessel is performed while simultaneously performing the electrolysis in a first vessel.

8. The method of claim 1, wherein collecting the precipitate of the cooled liquid cathode comprises collecting the precipitate on a seed crystal.

9. The method of claim 1, wherein collecting the precipitate of the cooled liquid cathode in the second vessel is performed without removing the liquid cathode that is in the first vessel.

10. The method of claim 1, wherein the liquid cathode, based on density of the liquid cathode compared to density of the oxide material, collects at a bottom region of the first vessel and in contact with a cathodic electrode of the electrolysis.

11. The method of claim 1, further comprising collecting oxygen gas from the first vessel while simultaneously collecting the precipitate in the second vessel.

12. A molten oxide electrolysis (MOE) system comprising: a first vessel that includes i) an anode and ii) a cathodic electrode in a bottom region of the first vessel, wherein the cathodic electrode is configured to be in electrical communication with an oxide material in the first vessel, the anode and the cathodic electrode are configured to provide an electrical current therebetween for a process of electrolysis of the oxide material, and the process of electrolysis of the oxide material produces a liquid cathode; and a second vessel that is separated from the first vessel by a conduit for carrying a portion of the liquid cathode from the first vessel to the second vessel, the second vessel including a precipitating surface configured to be immersed in the portion of the liquid cathode and to collect a precipitate of the cooled liquid cathode.

13. The MOE system of claim 12, wherein the precipitate of the cooled liquid cathode is a metal or metalloid.

14. The MOE system of claim 12, wherein the oxide material is derived from lunar regolith.

15. The MOE system of claim 12, further comprising a temperature controller to control the temperature of the portion of the liquid cathode that is in the second vessel or the conduit.

16. The MOE system of claim 15, wherein the temperature controller is configured to control the temperature of the portion of the liquid cathode in the second vessel to produce a vertical thermal gradient.

17. The MOE system of claim 16, further comprising a seed holder configured to raise or lower the precipitating surface based, at least in part, on the vertical thermal gradient.

18. The MOE system of claim 12, further comprising a system controller to enable the MOE system to collect the precipitate of the cooled liquid cathode in the second vessel while simultaneously performing the electrolysis in a first vessel.

19. The MOE system of claim 18, wherein the system controller further enables the MOE system to collect the precipitate of the cooled liquid cathode in the second vessel without removing the liquid cathode that is in the first vessel.

20. The MOE system of claim 12, wherein the liquid cathode is a liquid metal cathode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The disclosure will be understood more fully from the detailed description given below and from the accompanying figures of embodiments of the disclosure. The figures are used to provide knowledge and understanding of embodiments of the disclosure and do not limit the scope of the disclosure to these specific embodiments. Furthermore, the figures are not necessarily drawn to scale.

[0004] FIG. 1 is a schematic cross-section of a molten oxide electrolysis system, according to some embodiments.

[0005] FIG. 2 is a graph illustrating example temperature profiles of a liquid cathode in a molten oxide electrolysis system, according to some embodiments.

[0006] FIG. 3 is a graph illustrating a vertical thermal gradient of a liquid cathode in a portion of a molten oxide electrolysis system, according to some embodiments.

[0007] FIG. 4 is a schematic cross-section of a molten oxide electrolysis system that includes multiple precipitation vessels, according to some embodiments.

[0008] FIG. 5 is a schematic cross-section of a molten oxide electrolysis system that includes liquid cathode recirculation, according to some embodiments.

[0009] FIG. 6 is a flow diagram of a process of precipitating material from a liquid cathode, according to some embodiments.

DETAILED DESCRIPTION

[0010] This disclosure describes, among other things, a system and a method for precipitating a solid using molten oxide electrolysis. For example, the method may be used to thermally grow a metal or metalloid crystal product from a liquid metal cathode during electrolysis. In particular, a metal or metalloid product may be extracted or separated from a liquid metal cathode that is generated in, and formed by, electrolysis.

[0011] A metal oxide in a vessel may be reduced, using molten oxide electrolysis (MOE), into a relatively heavy liquid metal that sinks toward the bottom of the vessel. At least a portion of this liquid metal may form a liquid metal cathode. In contrast to a heavy liquid metal, some metals reduced by MOE are neutrally buoyant in, or less dense than, their associated molten oxide electrolytes and therefore float in the molten metal oxide.

[0012] In embodiments, a method may involve a first vessel and a second vessel used for an MOE process. The first vessel includes a molten mixture of a metal oxide and a heavier liquid metal cathode, which need not have been formed via electrolysis. The liquid metal cathode comprises a metal or metalloid that is to be subsequently extracted in the second vessel. Due to its relative density, the heavier liquid metal cathode may sink to the bottom of the first vessel. At least a portion of the liquid metal cathode may be collected into the second vessel where precipitation of the metal or metalloid from the liquid metal cathode occurs. Various processes for extracting the precipitated metal or metalloid may then be performed without interrupting the MOE process occurring in the first vessel.

[0013] The above-described process may provide a number of benefits. For example, the process is able to extract metal or metalloid products from a liquid metal cathode by growing crystals of the metal or metalloid product from the liquid metal cathode using a thermal gradient to drive precipitation/crystallization within a relatively cool region (e.g., in the second vessel) of the liquid metal cathode. For another example of a benefit, the liquid metal cathode need not be removed from the MOE system and later reintroduced because precipitation/crystallization of the metal or metalloid product in the second vessel can occur independently of the state or position of the liquid metal cathode in the first vessel. In yet another example of a benefit, some degree of purification may occur during the precipitation/crystallization process, thus providing a route toward achieving a relatively high purity of extracted product. This allows for a nearly pure product to be extracted during molten oxide electrolysis of low density metals.

[0014] Hereinafter, a liquid metal cathode will be referred to generally as a liquid cathode. Though examples herein describe implementations that involve liquid metal cathodes, claimed subject matter is not limited to a liquid cathode that includes metal.

[0015] In some embodiments, an MOE system comprises a first vessel that includes an anode and a cathodic electrode, which may be located at or near the bottom of the first vessel. The anode and cathodic electrode may be part of a single electrical circuit that includes a voltage or current source. Accordingly, a current may flow between the anode and cathodic electrode, creating a voltage difference across molten oxide material that is between the anode and cathodic electrode. Per its location in the first vessel, the cathodic electrode is configured to be in electrical contact with contents at or near the bottom of the first vessel. The electrical current between the anode and cathodic electrode may allow for a process of electrolysis of the oxide material. The electrolysis of the oxide material may lead to either the formation of cathode material or the creation of metal that can dissolve into an already existing liquid cathode, which is in electrical contact with the cathodic electrode. The MOE system may further comprise a second vessel that is separated from the first vessel by a conduit that carries a portion of the liquid cathode from the first vessel to the second vessel. One or both ends of the conduit may include a conduit section that couples the conduit to the first vessel or the second vessel. In some implementations, the conduit may be substantially horizontal and the conduit sections may be substantially vertical. The second vessel may include a precipitating surface therein that is configured to be immersed in the portion of the liquid cathode that flowed through the conduit from the first vessel. In some implementations, the liquid portion of the cathode need not flow through the conduit. For example, if a metal of interest dissolves in the liquid cathode it may diffuse through the liquid in the conduit. The precipitating surface may be configured to collect a precipitate of the liquid cathode, which is cooled relative to the liquid cathode in the first vessel. The precipitate of the cooled liquid cathode may be a metal or metalloid, such as silicon, for example.

[0016] In some implementations, the oxide material may be derived from lunar regolith. In some implementations, the MOE system may further comprise a temperature controller to control the temperature of the portion of the liquid cathode that is in the second vessel and/or the conduit. Moreover, the temperature controller may be configured to control the temperature of the portion of the liquid cathode in the second vessel to produce a vertical thermal gradient in a region around the precipitating surface. Such a vertical thermal gradient may be controlled (e.g., temperature as a function of vertical location in the second vessel) to adjust a rate of precipitation of a solid from the liquid cathode.

[0017] In some implementations, the MOE system may further comprise a seed holder in or above the second vessel and configured to raise or lower the precipitating surface based, at least in part, on the vertical thermal gradient. For example, the seed holder may receive instructions from a system controller to raise or lower based on a vertical thermal gradient that is measured by temperature sensors that provide thermal data about the second vessel to the system controller. The system controller may also, or instead, enable the MOE system, which may comprise a combination of electrical and mechanical components, to collect the precipitate of the cooled liquid cathode in the second vessel while simultaneously performing the electrolysis in the first vessel. In some implementations, the system controller may further enable the MOE system to collect the precipitate of the cooled liquid cathode in the second vessel without removing (e.g., or interrupting an electrolysis process of) the liquid cathode that is in the first vessel.

[0018] In some embodiments, a method for precipitating a solid using MOE includes performing electrolysis in a first vessel and, if a liquid cathode is not already present, heating an oxide material in the first vessel to allow for the creation of a liquid cathode. The method continues by subsequently receiving a portion of the liquid cathode into a second vessel that is separated from the first vessel by a conduit. The oxide material may be a mixture of two or more metallic oxides. As mentioned above, the conduit is configured to convey the portion of the liquid cathode from the first vessel to the second vessel. The liquid cathode, based on its density compared to the overall density of the oxide material, may generally collect at a bottom region of the first vessel so as to be in contact with a cathodic electrode of the electrolysis.

[0019] The method may further include allowing the portion of the liquid cathode to cool, as described below. A process of allowing the portion of the liquid cathode to cool may include at least partially controlling heat transfer of the flow of the portion of the liquid cathode in the conduit or the second vessel. Such control may be performed by controlling flow rate of the liquid cathode or controlling thermal insulation (e.g., quantity and location) applied to walls of the conduit or the second vessel, just to name a few examples. Moreover, the method may further include controlling the temperature of the portion of the liquid cathode that is in the second vessel to produce a vertical thermal gradient, as described below.

[0020] The method may continue with collecting a precipitate of the cooled liquid cathode in the second vessel. The precipitate of the cooled liquid cathode may be a metal or metalloid. A seed crystal may be used to collect the precipitate in a crystalline form. For example, a silicon ingot may be formed by precipitating silicon out of the liquid cathode onto a seed crystal. Meanwhile, in the first vessel, the electrolysis of the MOE process may continue to produce a supersaturated liquid metal solution in the oxide material, thereby causing the metal or metalloid product (which may, but need not, be in crystal form) to precipitate (or crystallize) out of solution. For the method, a liquid cathode may be selected so that the precipitated solid state metal or metalloid product (formerly a part of the liquid cathode) is insoluble in the liquid cathode solution (e.g., once it precipitates, it cannot return back to solution).

[0021] As mentioned above, the method may allow for an ability to collect precipitate of the cooled liquid cathode in the second vessel while simultaneously performing electrolysis in the first vessel. The method may also allow for an ability to collect the precipitate of the cooled liquid cathode in the second vessel without removing the liquid cathode that is in the first vessel. In some implementations, oxygen gas from the first vessel may be collected while simultaneously collecting the precipitate in the second vessel. For example, the method for precipitating a solid using MOE may allow for the production of oxygen gas.

[0022] In some implementations, oxide material used in the method may be derived from lunar regolith. For example, iron oxide may be in lunar regolith, or in minerals found on off-Earth locations and/or objects in the Solar System, such as asteroids, moons, minor-planets, and planets, among other objects. Of course, iron oxide is also present on Earth, and methods described herein may be performed on Earth, the moon, or other bodies listed above, and claimed subject matter is not limited in this respect.

[0023] FIG. 1 is a schematic cross-section of an MOE system 100, according to some embodiments. Various portions of the system, as illustrated, are not necessarily to scale. The MOE system generally comprises electrical and mechanical components that are interfaced with one another in various configurations. The MOE system may further comprise one or more computer processors configured to execute computer-readable instructions, which may be directed to controlling at least some of the electrical and mechanical components.

[0024] MOE system 100 may include a first vessel 102 (e.g., an electrolysis vessel), an anode 104 protruding into the first vessel from above, and a cathodic electrode 106, which may be located at or near the bottom 107 of the first vessel. The cathodic electrode is configured to be in electrical contact with a lower portion of contents, such as a liquid cathode 108, contained in first vessel 102. The anode and cathodic electrode may be part of a single electrical electrolysis circuit that includes a voltage or current source (not illustrated). Accordingly, a current may flow between the anode and cathodic electrode, creating a voltage difference across molten oxide material 110 that is between the anode and cathodic electrode. For example, in some implementations, a generic composition of oxides may be: SiO2+Al2O3+MgO+FeO+CaO with trace alkali oxides and halides. The electrical current between the anode and cathodic electrode may allow for a process of electrolysis of oxide material 110. Distances between the anode and cathodic electrode may be varied to adjust voltage and/or current of the electrolysis circuit. Such variation may be useful to account for varying resistivity of molten oxide material 110 and liquid cathode 108, for example. As explained above, the electrolysis of molten oxide material 110 may produce liquid cathode 108, which, in embodiments described herein, is denser than the surrounding molten oxide material. Accordingly, the liquid cathode will sink toward the bottom of first vessel 102 and thus be in electrical contact with cathodic electrode 106.

[0025] MOE system 100 may further comprise a second vessel 112 (e.g., a precipitation vessel), that is separated from first vessel 102 by a conduit 114 that carries a portion 116 of the liquid cathode from the first vessel to the second vessel. The conduit may be a tube, pipe, channel, or connecting chamber, just to name a few examples. One end of conduit 114 may include a conduit section 118 that couples the conduit to the first vessel at an interface 120, and the other end of conduit 114 may include a conduit section 122 that couples the conduit to the second vessel at an interface 124. In some implementations, conduit 114 may be substantially horizontal and conduit sections 118 and 122 may be substantially vertical.

[0026] During operation of MOE system 100, portion 116 of liquid cathode in conduit 114 may flow into second vessel 112, at least partially filling the vessel with a second portion 126 of liquid cathode. Liquid cathode 108 in first vessel 102, portion 116 of the liquid cathode in conduit 114, and second portion 126 of the liquid cathode are, except for possible temperature differences and chemical concentrations, the same or similar. Examples herein are described using these names of the portions of the liquid cathode merely to identify their respective general locations in system 100.

[0027] A precipitating surface 128 may be attached to a seed holder 130 with a seed crystal that can be raised and lowed, as indicated by arrow 132, into second vessel 112. The seed crystal may comprise the solute material in the second vessel. In some implementations, silicon may be precipitated using a silicon seed, wherein silicon may be induced to precipitate on the seed by a temperature gradient. The seed also adds the benefit of helping to grow a single crystal. For example, seed holder 130 may be configured to immerse precipitating surface 128 in and out of second portion 126 of liquid cathode, which is cooler than other portions of the liquid cathode in system 100, as explained below. Precipitating surface 128 may be configured to collect a precipitate of second portion 126 of the cooled liquid cathode. The precipitate of the cooled liquid cathode may be a metal or metalloid, such as silicon, for example.

[0028] In some implementations, seed holder 130 may be electrically insulated or isolated because liquid cathode 126 is electrically conductive. Accordingly, a process of electrolysis in first vessel 102 may generally electrify liquid cathode 126 in the second vessel. Thus, seed holder 130 may be made of an insulative material so that it will not convey electrical current to other parts of system 100. In other implementations, seed holder 130 may be electrically conductive to provide an electrical contact for the process of electrolysis.

[0029] In some implementations, MOE system 100 may further include a temperature controller 134 to control temperatures of various portions of the liquid cathode, such as liquid cathode 108, portion 116, and second portion 126. The temperature controller may operate in combination with thermal insulation and/or air (or other fluid) circulation systems to at least partially maintain temperature and/or cool the liquid cathode in the various parts of system 100. For example, conduit 116 may be covered with thermal insulation or other material to prevent the flow of liquid cathode (e.g., 116) from cooling more than a desired amount. In addition, or instead, conduit 116 may be exposed to a cooling air flow that may be varied by temperature controller 134. In some implementations, locations or distribution of thermal insulation may also be varied by temperature controller 134. First and second vessels may likewise have such insulation or air flow exposure. The temperature controller may be configured to control the temperature of portion 126 of the liquid cathode in second vessel 112 to produce a vertical thermal gradient in a region around precipitating surface 128, as explained below. In some implementations, seed holder 130 may be configured to raise or lower precipitating surface 128 based, at least in part, on the vertical thermal gradient. For example, MOE system 100 may include a system controller 136 that provides instructions to a motion transducer 138 to move the seed holder to raise or lower the precipitating surface based on a thermal gradient that is measured by temperature sensors (not illustrated) that provide thermal data to the system controller.

[0030] In some implementations, system controller 136 may enable the MOE system to collect precipitate accumulated on precipitating surface 128 while simultaneously performing electrolysis in first vessel 102. In this way, the MOE system may allow collection of the precipitate without removing the liquid cathode that is in the first vessel. Thus, MOE system 100 may operate continuously instead of operating in batch processes.

[0031] In some implementations, MOE system 100 may further include a valve 140 and conduit 142 for removing molten oxide material 110 and/or liquid cathode 108. System controller 136 may operate valve 140, for example. In some implementations, oxygen gas may be produced from the electrolysis process performed on first vessel 102. The oxygen gas may be collected via an exit port 144.

[0032] Conduit 114 is labelled in FIG. 1 with A and B, which point to respective portions of the conduit. These points will be referred to in descriptions below of thermal aspects of the liquid cathode. Also, second vessel 112 is labelled in FIG. 1 with C and D, which point to respective heights of the second vessel. These points will also be referred to in descriptions below of thermal aspects of the liquid cathode.

[0033] FIG. 2 is a graph 200 illustrating example temperature profiles of portion 116 of liquid cathode in conduit 114, according to some embodiments. In particular, graph 200 includes plots of relative temperature of the liquid cathode as a function of distance along the conduit. Points A and B are included as example reference points along the length of the conduit. Generally, depending on the environment immediately outside conduit 114, liquid cathode 116 cools as it flows from first vessel 102 to second vessel 112. Such cooling may be slowed by thermal insulation, such as in the form of conduit material (e.g., thickness thereof) or additional insulative material surrounding the conduit. In contrast, such cooling may be increased by providing circulating fluid (e.g., air, gas, water, or other liquid) to at least partially surround and flow around conduit 114. Plot 202 may be an example where cooling is slowed by thermal insulation. Plot 204 may be an example where cooling is increased by providing circulating fluid to the outside of conduit 114. Plot 204 may also be an example where cooling is allowed to occur by virtue of a lack of thermal insulation. Other example plots may illustrate nonlinear cooling, and claimed subject matter is not limited in this respect.

[0034] Rate of cooling of the flow of liquid cathode 116 in conduit 114 may determine the temperature of the liquid cathode as it is introduced into second vessel 112. Consideration of temperatures of the liquid cathode in various parts of MOE system 100 are generally important for solids to precipitate out of the liquid cathode onto precipitating surface 128.

[0035] FIG. 3 is a graph 300 illustrating an example temperature profile of portion 126 of liquid cathode in second vessel 112, according to some embodiments. In particular, graph 300 includes a plot 302 of relative temperature of the liquid cathode as a function of depth of the liquid cathode in second vessel 112. Points C and D are included as example reference points along the height of the second vessel. Generally, depending on the environment immediately outside second vessel, heat of liquid cathode 126 escapes to outside second vessel 112, thus cooling the liquid cathode. Such cooling may be slowed by thermal insulation, such as in the form of second vessel material (e.g., thickness thereof) or additional insulative material surrounding the second vessel. In contrast, such cooling may be increased by providing circulating fluid to at least partially surround and flow around at least portions of second vessel 112. Cooling may be increased for one part of the second vessel while cooling may be decreased in another part of the second vessel. Such a combination of cooling rate modification may allow for controlling the temperature of the liquid cathode to produce a vertical thermal gradient, which may be selected or adjusted to allow for solids to precipitate out of the liquid cathode onto precipitating surface 128. Rate of such precipitation may depend, at least in part, on the position of precipitating surface 128 relative to the vertical thermal gradient. System controller 136, for example, may dynamically control temperature of liquid cathode 126 to match the growth rate of precipitate with the electrolysis rate. As precipitate material, which is still in the liquid cathode solution, becomes increasingly depleted, system controller 136 may adjust the vertical thermal gradient so that the precipitation process moves along the phase diagram of the precipitate.

[0036] Plot 302 may be an example of such a vertical thermal gradient. For example, the temperature of liquid cathode 126 along the vertical thermal gradient at depth 304 may be substantially ideal for solids to precipitate out of solution (e.g., the liquid cathode). As the concentration (e.g., precipitate concentration) of the metal or metalloid that is to be precipitated out of solution changes, the optimum temperature for precipitation may also change. Accordingly, system controller 136 of the MOE system may adjust the location (e.g., depth) of precipitating surface 128 based on temperature and precipitate concentration, for example. Other example plots may illustrate other linear slopes or nonlinear vertical thermal gradients, and claimed subject matter is not limited in this respect.

[0037] FIG. 4 is a schematic cross-section of an MOE system 400 that includes multiple precipitation vessels 402 and 404, according to some embodiments. MOE system 400 may include an electrolysis vessel 406, which is similar to or the same as first vessel 102 of MOE system 100. An anode 408 may protrude into the electrolysis vessel from above.

[0038] Precipitation vessels 402 and 404 may each be the same as or similar to second vessel 112 and are each separated from electrolysis vessel 406 by a conduit 410 and 412, respectively, that carries portions of liquid cathode from the electrolysis vessel to the precipitation vessels. Other features of MOE system 400 may be the same as or similar to MOE system 100. The principle difference illustrated in the example embodiment of FIG. 4 as compared to the example embodiment of FIG. 1 is the presence of multiple precipitation vessels. Two are illustrated and more may be present in other implementations. As mentioned above, a process performed by an MOE system such as 100 or 400 may provide a number of benefits. For example, the process is able to extract metal or metalloid products from the liquid metal cathode by growing crystals (or other solid formation) on one or more precipitating surfaces, such as 414 and 416. Meanwhile, the liquid metal cathode need not be removed from electrolysis vessel 406 for harvesting the extracted metal or metalloid because precipitation/crystallization of the metal or metalloid product in the precipitation vessels 402 and 404 can occur independently of the state or position of the liquid metal cathode in electrolysis vessel 406. Thus, MOE systems 100 and 400 may operate continuously instead of operating in batch processes. Accordingly, an MOE system, such as 400, may gain additional degrees of efficiency by including two or more precipitation vessels, which may allow for increased production of extracted metal or metalloid products, as compared to a single precipitation vessel, as in the example embodiment of FIG. 1. In some implementations, more than one precipitation vessel may be included in an MOE system for thermal reasons. For example, temperature management of liquid cathode material in an MOE system may be easier with multiple, relatively small precipitation vessels. Claimed subject matter, however, is not limited in this respect.

[0039] FIG. 5 is a schematic cross-section of an MOE system 500 that includes liquid cathode recirculation, according to some embodiments. Similar to or the same as MOE system 100, MOE system 500 includes a first vessel 502, wherein electrolysis may occur, and a second vessel 504, where precipitation may occur. A first portion 506 of a liquid cathode is in first vessel 502, a second portion 508 of the liquid cathode is in a conduit 510 that separates the first and second vessels, and a third portion 512 of the liquid cathode is in second vessel 504. A molten oxide material 514 may also be in first vessel 502, which may include a valve 516 and conduit 518 for removing molten oxide material 514 and/or liquid cathode 506. MOE system 500 may also include a recirculation path 520 and control valve 522. In some implementations, as illustrated, the recirculation path may convey portions of liquid cathode 512 from second vessel 504 to first vessel 502. Control valve 522 may be used to control flow of the recirculating liquid cathode. Though not illustrated, recirculation path 520 and control valve 522 may include thermal insulation to maintain a relatively high temperature of liquid cathode as it flows therethrough. The exit height of recirculation path 520 from second vessel 504 and the entry height into first vessel 502 need not be as illustrated.

[0040] Liquid cathode 512 may become increasingly depleted of precipitate material (e.g., the metal or metalloid to be extracted) as the precipitate is grown onto a precipitating surface 524. Recirculation path 520 may provide a path for the precipitate-depleted liquid cathode to return to first vessel 502, where the reintroduced liquid cathode may be re-heated and further processed. In other implementations, an exit path (not illustrated) may replace recirculation path 520 so that precipitate-depleted liquid cathode is removed from the MOE system. Claimed subject matter is not limited to any particular implementations involving a precipitate-depleted liquid cathode.

[0041] FIG. 6 is a flow diagram of a process 602 of precipitating material, such as a solid metal or metalloid, from a liquid cathode, according to some embodiments. The process may be performed by an operator, which may be a person or persons, a computer processor executing computer-readable code, or a combination thereof. The process may be performed by the operator using MOE system 100, for example.

[0042] At 604, in this embodiment, via an electrical current used for electrolysis in a first vessel, the operator may use system 100 to heat an oxide material. Other methods of heating the oxide material include induction heating and microwave heating using a susceptor material, just to name a few examples. Claimed subject matter is not limited to any particular method of heating the oxide material. Heating the oxide may allow for forming a liquid cathode in the melt but a liquid cathode may be already be present while electrical current (reduction) adds additional material to the cathode. The oxide material may be a mixture of two or more metallic oxides. The liquid cathode, based on its density compared to the overall density of the oxide material, may generally collect at a bottom region of the first vessel so as to be in contact with a cathodic electrode of the electrolysis. At 606, the operator may use system 100 to receive a portion of the liquid cathode into a second vessel that is separated from the first vessel by a conduit, which conveys the portion of the liquid cathode from the first vessel. At 608, the operator may use the system to allow the portion of the liquid cathode to cool. Allowing the portion of the liquid cathode to cool (or performing one or more actions that cause the portion of the liquid cathode to cool) may include at least partially controlling heat transfer of the flow of the portion of the liquid cathode in the conduit and/or the second vessel. Such control may be performed by controlling flow rate of the liquid cathode or distribution of thermal insulation applied to walls of the conduit or the second vessel, just to name a few examples. Moreover, the method may further include controlling the temperature of the portion of the liquid cathode that is in the second vessel to produce a vertical thermal gradient, as described above.

[0043] The electrolysis of the MOE process may lead to supersaturation of a liquid metal solution of the oxide material, thereby causing a metal or metalloid product (which may be in crystal form) to precipitate (or crystallize) out of solution. The liquid cathode solvent material may be chosen so that it is minimally soluble with the reduced solvent in the solid state. When the solute metal/metalloid is precipitated from solution, there may still be some solute dissolved in the solution, but the solution will be supersaturated at that temperature. Accordingly, at 610, the operator may use the system to collect a precipitate of the cooled liquid cathode in the second vessel. A seed crystal or other precipitating surface may be used to collect the precipitate. From time to time, or periodically, the precipitating surface may be removed from the second vessel to harvest the formed solid precipitate. If a general precipitating surface is used, harvesting may involve a process of removing the solid precipitate from the precipitating surface by scraping, chipping, cutting, etc. If a seed crystal is used, harvesting may involve removing a completely formed crystal that started with the seed crystal.

[0044] As explained above, process 602 may allow for an ability to collect precipitate of the cooled liquid cathode in the second vessel while simultaneously performing electrolysis in a first vessel. The method may also allow for an ability to collect the precipitate of the cooled liquid cathode in the second vessel without removing the liquid cathode that is in the first vessel. In an aspect of this process is that the electrolysis may create supersaturation that drives the crystal growth/precipitation process. So it is not just that the electrolysis can happen in parallel but that the electrolysis may provide the nutrient for the crystal growth.

[0045] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the disclosure. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the systems and methods described herein. The foregoing descriptions of specific embodiments or examples are presented by way of examples for purposes of illustration and description. They are not intended to be exhaustive of or to limit this disclosure to the precise forms described. Many modifications and variations are possible in view of the above teachings. The embodiments or examples are shown and described in order to best explain the principles of this disclosure and practical applications, to thereby enable others skilled in the art to best utilize this disclosure and various embodiments or examples with various modifications as are suited to the particular use contemplated. It is intended that the scope of this disclosure be defined by the following claims and their equivalents.