Thermal electrolytic production may utilize heat pipes. A heat pipe is a component of a reflux evaporator with an extremely high effective thermal conductivity. Heat pipes are evacuated vessels, typically circular in cross section, which are back-filled with metal fluid. The reflux evaporator may be a passive system, with no moving parts, used to transfer heat from a heat source to a heat sink or an isothermal surface with minimal temperature gradients.
Heat pipes operate using evaporation and condensation of the heat pipe liquid metal. Specifically, as heat is input at the evaporator, the heat pipe liquid metal vaporizes, creating a pressure gradient in the heat pipe. This forces the vapor of the heat pipe liquid metal to flow along the heat pipe to the cooler section where it condenses, giving up the latent heat of the heat pipe liquid metal from vaporization. The heat pipe liquid metal is then returned to the evaporator by capillary forces in the porous wick structure or by gravity. For heat pipes used in elevated locations, such as towers, the heat pipe liquid metal has to work against gravity. For example, suppose that an evaporator is on top of the tower and that the condenser is located a hundred meters below on the ground. For the heat pipes to function, large amounts of the heat pipe liquid metal must climb the hundred meters using capillary pumping, which is unviable. Accordingly, the applications of heat pipes may make the conventional use of capillary pumping and gravity refluxing unviable.
This brief description is provided to introduce a selection of concepts in a simplified form that are described below in the detailed description. This brief description is not intended to be an extensive overview of the claimed subject matter, identify key factors or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
As discussed above, relying on capillary pumping and gravity refluxing to return the heat pipe liquid metal to the evaporator may be unviable. It is unviable because the capillary pumping pressure must overcome three basic pressure drops within the heat pipe: vapor pressure drop, liquid pressure drop, and gravitational force pressure drops. If the evaporator is located above the condenser, the heat pipe liquid metal may not be able to overcome these three pressure drops.
For a heat pipe to transfer heat, the heat pipe liquid metal vaporizes and travels to the condenser, where it is condensed and turned back to a saturated metal fluid. In one embodiment, the condensed metal fluid is returned to the evaporator using a wick structure exerting a capillary action on the liquid phase of the metal fluid. The wick structure of the heat pipe may be finer. The finer the pore radius of a wick structure, the better the heat pipe can operate despite gravity. Still, based on the vertical distance between the evaporator and the condenser, a fine enough wick structure may not be physically possible. Accordingly, heat pipes may not be able to operate against gravity.
Described herein are examples of systems, methods, and other embodiments associated with active reflux evaporators. The systems, methods, and other embodiments described herein actively pump metal fluids from the condenser (e.g., the thermal load, electrolytic cell) up the tower to the evaporator. By using active reflux evaporators returning fluid metal to an evaporator is no longer subject to the restraints of gravity. Accordingly, evaporators can be used in applications in which the evaporator is vertically separated from the condenser. For example, a solar tower may be specifically suited for isothermal applications such as supplemental heating for electrolytic cells. In one embodiment, a solar tower having an active reflux evaporator may be used in conjunction with an electrolytic cell for solar thermal electrolytic production such as generating a metal from a metal ore.
The following description and drawings set forth certain illustrative aspects and implementations. These are indicative of but a few of the various ways in which one or more aspects may be employed. Other aspects, advantages, or novel features of the disclosure will become apparent from the following detailed description when considered in conjunction with the drawings.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various systems, methods, and other embodiments of the disclosure. Illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. In some examples one element may be designed as multiple elements or multiple elements may be designed as one element. In some examples, an element shown as an internal component of another element may be implemented as an external component and vice versa.
Embodiments or examples illustrated in the drawings are disclosed below using specific language. It will nevertheless be understood that the embodiments or examples are not intended to be limiting. Any alterations and modifications in the disclosed embodiments and any further applications of the principles disclosed in this document are contemplated as would normally occur to one of ordinary skill in the pertinent art. Described herein are examples of systems, methods, and other embodiments associated with thermal electrolytic production.
Heat pipes have high heat flux capabilities, operate isothermally and are capable of operating at temperatures up to 1100° C. Therefore, heat pipes are well suited for transferring heat to wide range of high-temperature applications, such as supplemental heating for electrolytic cells. Conventional liquid metal heat pipes operate by delivering the heat to a load by condensing the metals using gravity refluxing and/or capillary forces in a wick to return the condensed liquid metal back to the evaporator. However, these forces are typically insufficient to return the metals over vertical distances. For example, capillary pumping large amounts of a heat pipe liquid metal up towers over 100 meters high is not viable.
As discussed above, for an evaporator on top of a tower and a condenser on the ground, the heat pipe liquid metal return has to work against gravity and capillary pumping large amounts of a heat pipe liquid metal up towers over 100 meters high is not viable. Actively pumping the heat pipe liquid metal from the condenser up the tower to the evaporator is potentially a way to overcome this shortcoming.
The distribution of the liquid metal is driven by thermal energy derived from solar flux received at the opening 230. The opening 230 may include optics to focus the solar flux. For example, the case of solar input with tower-based optics, the reactor matches the concentrated solar flux delivered to the electrochemical reaction rate. In order to match the concentrated solar flux to the demand for thermal energy at an electrolytic cell.
In one embodiment, the thermal energy may be derived from alternative sources such as natural gas, hybrid of solar and natural gas, general combustion of fossil fuels, etc., or a combination thereof. The thermal energy supplies all non-electrical energy necessary to drive the reaction with respect to
The condenser system 120 includes a thermal load 270. In one embodiment, the thermal load 270 is an array of isothermal loads. In one embodiment, the thermal load 270 is an electrolytic cell. The thermal load 270 causes the evaporated liquid metal to condense into a liquid metal.
The condenser system 120 also includes a liquid pump assembly 280. The liquid pump assembly 280 returns the liquid metal through the return 250 to the distributor pump assembly 260 described above with respect to
The ability of heat pipes, including the piping 240 and the return 250 discussed above with respect to
The electrolytic cell 500 includes an anode 510 and cathode 520. In one embodiment, the anode 510 is carbon. The cathode 520 may be steel or molybdenum. The electrolytic cell 500 may further include a molten salt electrolyte, such as a fluoride-based molten salt electrolyte or an eutectic mixture including magnesium fluoride (MgF2), calcium fluoride (CaF2), and barium fluoride (BaF2) in various ratios.
Electrolysis separates the metal from the metal ore. In accordance with the example given above, the Mg is separated from the MgO. As described herein, the liquid metal produced from the metal ore is referred to as the produced liquid metal to differentiate the produced liquid metal from the heat pipe liquid metal. The produced metal liquid is formed as a liquid in an electrolyte, such as a molten fluoride salt, at high temperatures (e.g., 1250° C.) as a product of electrolysis. The electrical energy input to the electrolytic process is kept as close to the thermodynamic minimum that nature will allow so that the remainder of the energy required to drive the reaction is supplied as thermal energy. As discussed above with respect to
The produced liquid metal forms at the cathode 520 and is directed away from the gaseous products forming at the anode 510 to increase the current efficiency because hydrodynamic forces, including buoyancy, direct the flow of the products (e.g., the produced liquid metal) from the anode 510. Specifically, the produced liquid metal at the cathode 520 is channeled through a shroud 530 such that the metal is isolated from the anode 510. The shroud is configured to separate the anode products to minimize the cell overvoltage for a given desired current level so that the electrical energy input can be kept low, thereby maximizing the opportunity for thermal input. Thus, the shroud the separation process is designed to minimize the interelectrode gap without comprising the current efficiency because the smaller the interelectrode gap the lower the overvoltage.
The shroud 530 is constructed to surround the cathode 520. The size, shape, and materials of the shroud 530 are selected to maximize high current efficiency at a low voltage or overvoltage. To this end, the structure of the shroud 530 is selected such that the electrical energy input is substantially the difference in free energy between the products and the reactants, ΔG. In one embodiment, the outside of the shroud 530 is constructed from a non-conducting oxidized material and the interior houses the cathode 520. In one embodiment, the shroud 530 has solid walls. In another embodiment, the shroud 530 may surround all or a portion of the cathode 520 to improve the current flow about the cathode 520. In another embodiment, the shroud 530 is permeable. For example, the shroud 530 may be constructed from a mesh or material having flow holes. The shroud 530 may be constructed of a metal (e.g., steel, molybdenum), ceramics, polymer, wire, etc, or combination thereof.
The metal is less dense than the electrolyte and therefore rises in the shroud 530. The shroud 530 allows the metal that forms at the cathode 520 to rise to the top of an electrolyte, isolated from gas products, such as CO2/CO, forming at the anode 510 prevents the metal from recombining with the gas product and thus compromising the current efficiency of the cell. By isolating the metal from the anode product, the shroud 530 enables high current efficiency without an excessive overvoltage penalty. Accordingly, industrially relevant current densities are attained while most of the charge transfer goes to producing recoverable metal.
In one embodiment, the metal is Mg. The Mg liquid floats on top of the electrolyte within the shroud 530. For example, the cathode 520 and shroud 530 may for a compartment that allows for the removal of the Mg from the electrolytic cell 500. In one embodiment, the liquid Mg is channeled out of this compartment and recovered as a liquid metal outside of the electrolytic cell 500. In another embodiment, a flow of a gas, such as Ar, passes through this compartment thereby vaporizing the metal and directing the Ar/Mg gas mixture outside the electrolytic cell 500 where Mg is condensed and the Ar is recycled back to the electrolytic cell 500, which is known as flash vaporization.
When the metal rises within the shroud 530 to the top of the electrolyte in the electrolytic cell 500, the metal is then vaporized in an inert gas stream. The inert gas stream is provided through inlet 540 and exits the electrolytic cell 500 at outlet 550. For example, the inert gas may be argon or other inert gas. The metal is condensed downstream of the electrolytic cell 500. The metal condenses first to a liquid and then to a solid. The inert gas may be recycled back to the electrolytic cell 500. Gases, such as carbon dioxide (CO2) and/or carbon monoxide (CO) mixtures, resulting from electrolysis form at the anode 510. The gases rise and exit the electrolytic cell 500 through the outlet 550. The cell 500 may be placed in a container 560 having a graphite liner 570.
The electrolytic cell further includes a connection point 610. The connection point 610 that allows the electrolytic cell 500 to be operably connected to other devices such as a solar tower as described with respect to
At 710, metal ore is provided to an electrolytic cell for electrolysis. Suppose that the metal ore is MgO. The MgO may be provided as a pellet or a powder based on the desired dissolve rate. As described above, the electrolytic cell includes a cathode, an anode, and an electrolyte such as a molten salt electrolyte. The process of electrolysis divides the metal from the metal ore. For example, electrolysis separates Mg from MgO. As discussed above, the metal forms as a liquid at the cathode.
At 720, the metal resulting from the electrolysis of the metal ore is isolated in a shroud at the cathode. The shroud is constructed around the cathode to isolate the metal at the cathode. The shroud may be semi-permeable such that the metal is able to flow inward but not outward. The shroud may be constructed with micro-valves and/or strategically placed holes. In another embodiment, the shroud may be constructed from a metallic or polymer mesh. By isolating the metal from the anode product, the shroud enables high current efficiency without an excessive overvoltage penalty.
At 730, the produced liquid metal is retrieved from a shroud. In one embodiment, the condensed metal may be tapped from the shroud. For example, an outlet may be positioned to allow the condensed metal to flow out of the electrolytic cell. In one embodiment, the metal moves through the shroud based on pressure differentials and is swept into an inert gas stream. In the inert gas stream, the metal is vaporized in a process such as, flash vaporization. When the metal is in the captured in the inert gas stream the metal condenses first into a liquid and then into a solid. At 740, the condensed metal is retrieved from the inert gas stream.
The following includes definitions of selected terms employed herein. The definitions include various examples and/or forms of components that fall within the scope of a term and that may be used for implementation. The examples are not intended to be limiting. Both singular and plural forms of terms may be within the definitions.
References to “one embodiment”, “an embodiment”, “one example”, “an example”, and so on, indicate that the embodiment(s) or example(s) so described may include a particular feature, structure, characteristic, property, element, or limitation, but that not every embodiment or example necessarily includes that particular feature, structure, characteristic, property, element or limitation. Furthermore, repeated use of the phrase “in one embodiment” does not necessarily refer to the same embodiment, though it may.
While for purposes of simplicity of explanation, illustrated methodologies are shown and described as a series of blocks. The methodologies are not limited by the order of the blocks as some blocks can occur in different orders and/or concurrently with other blocks from that shown and described. Moreover, less than all the illustrated blocks may be used to implement an example methodology. Blocks may be combined or separated into multiple components. Furthermore, additional and/or alternative methodologies can employ additional, not illustrated blocks. The methods described herein is limited to statutory subject matter under 35 U.S.C §101.
To the extent that the term “includes” or “including” is employed in the detailed description or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim.
While example systems, methods, and so on have been illustrated by describing examples, and while the examples have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the systems, methods, and so on described herein. Therefore, the disclosure is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims, which satisfy the statutory subject matter requirements of 35 U.S.C. §101.
Various operations of embodiments are provided herein. The order in which one or more or all of the operations are described should not be construed as to imply that these operations are necessarily order dependent. Alternative ordering will be appreciated based on this description. Further, not all operations may necessarily be present in each embodiment provided herein.
As used in this application, “or” is intended to mean an inclusive “or” rather than an exclusive “or”. Further, an inclusive “or” may include any combination thereof (e.g., A, B, or any combination thereof). In addition, “a” and “an” as used in this application are generally construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form. Additionally, at least one of A and B and/or the like generally means A or B or both A and B. Further, to the extent that “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising”.
Further, unless specified otherwise, “first”, “second”, or the like are not intended to imply a temporal aspect, a spatial aspect, an ordering, etc. Rather, such terms are merely used as identifiers, names, etc. for features, elements, items, etc. For example, a first channel and a second channel generally correspond to channel A and channel B or two different or two identical channels or the same channel.
Although the disclosure has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur based on a reading and understanding of this specification and the annexed drawings. The disclosure includes all such modifications and alterations and is limited only by the scope of the following claims.
This application claims the benefit of pending U.S. Provisional Patent application, Ser. No. 62/056,258, entitled Solar Thermal Electrolytic Production of Mg from MgO, filed Sep. 26, 2014, and U.S. Provisional Patent application, Ser. No. 62/111,588, entitled Active Reflux Evaporator associated with Thermal Electrolytic Production of Metal from Metal Ore, filed Feb. 3, 2015, which are hereby incorporated by reference herein.
This invention was made with government support under cooperative agreement DE-AR0000421 awarded by the U.S. Department of Energy through the ARPA-E program. The government has certain rights in the invention.
Number | Date | Country | |
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62056258 | Sep 2014 | US | |
62111588 | Feb 2015 | US |