Molten Material Flow Control

Some of the key challenges of lunar colonization and other activities on the Moon are the cost and logistics of transporting materials from Earth to the Moon. To overcome this, scientists and engineers have been exploring the concept of in-situ resource utilization (ISRU), which involves using materials found on the moon to build infrastructure, produce materials and fuel, and sustain life.

Molten oxide electrolysis (MOE) is being pursued as a technique for production of various materials (e.g., oxygen, silicon, and metals) for ISRU. MOE is a process that may be used to reduce molten oxides to their metal form using an electric current. For example, MOE may be used as an electrometallurgical technique to produce iron metal in a liquid state from oxide feedstock. Lunar regolith, which may be used as the feedstock for MOE, generally requires high temperatures (e.g., approximately 1900° C.) to keep the regolith molten and flowing. Control valves for routing molten lunar regolith, and the electrolyte resulting from the MOE, must be made of high-temperature tolerant refractory materials or refractory metals and must be able to control the flow of the viscous molten lunar regolith. Such challenges and limitations give rise to a search for improvements to controlling the flow of high-temperature molten material.

This disclosure describes, among other things, a method and system for controlling high-temperature molten material flow. Generally, a liquid flow may be controlled by valves or gates, but a high-temperature molten material may present a number of difficulties for the use of valves or gates. A high-temperature molten material, as applied to methods or systems described herein, is considered to have a temperature greater than about 1000 degrees centigrade. For example, molten lunar regolith may be at a temperature of about 1900 degrees C. At such high temperatures, valves or gates must be made of high temperature tolerant refractory materials or refractory metals and must be able to control the flow of liquid having a relatively high viscosity. Even properly designed valves or gates may face difficulties such as jamming, sticking, or decomposition due to, among other things, inconsistencies in the high-temperature molten material.

Though examples herein may be directed to high-temperature molten material that is molten lunar regolith and electrolyte formed therefrom, claimed subject matter is not limited in this respect. For example, benefits may be realized by using herein-described methods or systems for controlling flows of liquids other than molten lunar regolith or high-temperature molten material.

In some embodiments, a method of controlling the flow of a high-temperature molten material, hereinafter called “molten material”, may include positioning a displacer above or partially immersed in the molten material that is contained in a vessel. As described in detail below, the displacer may be a mass of material that can variably displace the molten material, thereby increasing the height of the top surface of the molten material, when the displacer is immersed in the molten material. The vessel may include an output port at a height that may be at, above, or below the top surface of the molten material, depending on the amount of immersion of the displacer. The method of controlling the flow of the molten material may further include selecting a flow rate for the molten material to flow out of the vessel through the output port and immersing the displacer in the molten material by an amount that is based, at least in part, on the selected flow rate. In some implementations, increasing a depth of immersion of the displacer may increase the flow rate of the molten material through the output port. In some implementations, continuously increasing a depth of immersion of the displacer may maintain a constant flow rate of the molten material through the output port.

In some embodiments, to avoid condensation of molten material on the displacer surface, the displacer may be preheated while it is positioned above the molten material. For example, condensation or buildup of material on the displacer may be substantially avoided by preheating the displacer to a temperature that is about the same as or above the temperature of the molten material.

In some embodiments, the displacer may have a dual function of variable liquid displacement and being an anode for electrolysis of the molten material. For example, a positive electric potential may be applied to the displacer. The electrolysis may be molten oxide electrolysis (MOE) performed on molten lunar regolith as the molten material. As explained below, the MOE process may involve a molten iron cathode at a bottom portion of the vessel.

In some embodiments, a flow system that may be used to perform the method described above may include a vessel configured to contain a molten material, an output port at a particular height in a side of the vessel and configured to convey a portion of the molten material that is at or above the particular height of the output port, a displacer inside the vessel and configured to be immersed at variable depths in the molten material, an actuator to immerse the displacer at the variable depths in the molten material, and an electronic controller to i) receive a signal representative of a selected flow rate for the molten material to flow out of the vessel through the output port and ii) operate the actuator to immerse the displacer in the molten material by an amount that is based, at least in part, on the selected flow rate. The flow system is described in detail below.

are schematic cross-section side views of a high-temperature molten material flow system, according to various embodiments. Both figures illustrate the same system. For illustrative clarity, some features and components of flow systemare illustrated only in.

Flow systemmay include a vesselconfigured to contain a molten materialand having an output portat a particular height in a side of the vessel. Output portmay be configured to convey a portion of the molten material that is at or above the particular height of the output port, as explained below. A displacermay be inside the vessel and configured to be immersed at variable depths in molten material. An actuatormay be used to immerse displacerat the variable depths in the molten material. In some implementations, vesseland displacermay be made of one or more refractory materials that can withstand refractory temperatures.

An electronic controllermay perform various functions or operations for flow system. The electronic controller may be a computer processor, as described below, for example. Electronic controllermay receive, possibly via a user interface, a signal representative of a selected flow rate for molten materialto flow out of vesselthrough output port. Accordingly, the electronic controller may operate actuatorto immerse displacerin the molten material by an amount that is based, at least in part, on the selected flow rate. For example,illustrates displacerabove and separate from molten materialso that no displacement of the molten material occurs and the top level of the molten material is below a bottom of output portby a distance. In some situations, even if displaceris partially immersed in molten material, a resulting displacement may still be insufficient to raise the top level of the molten material to the height of output port. In any case, these situations and others that result in the top level of the molten material being below the height of output porthave the outcome of zero flow out of vessel. In contrast, as illustrated in, displacermay be immersed into molten materialby an amount that results in the top level of the molten material being above the bottom of output portsuch as by a distance. This situation leads to flow of the molten material out of vesselthrough output port, as indicated by arrow. As explained below, increasing the amount of displaced molten material may result in an increase in flow rate of the molten material through the output port.

As just described above, there may be some situations where the top level of the molten material is below the height of output port, having the outcome of zero molten material flow out of vessel. In some implementations, however, such situations may be utilized to collect oxygen through output port. For example, if flow systeminvolves an MOE process, oxygen may be produced and accumulate above the top surface of molten material(e.g., electrolyte). With the top level of the molten material being below the height of output port, oxygen may flow out of vesselvia the output port. This is described below.

Flow systemmay include a height sensorto measure the height of high-temperature molten materialin vessel. For example height sensormay include an ultrasonic transmitter or laser rangefinder and measure a time-of-flight of an emitted signalthat reflects from the top level of molten material. Electronic controllermay receive height measurements from height sensorperiodically, continuously, or from time to time.

In some embodiments, flow systemmay include a lidthat covers the contents of vessel. The lid may be sealed at the interface with the top of vesselso gases, such as oxygen, may be contained in the vessel above molten material. Lidmay include a pass-through(e.g., a vacuum flange) that allows a shaftto move vertically up and down by actuator, as indicated by arrow, Shaft, being connected to displacer, may impart its vertical motion to varying the amount of immersion of the displacer in molten material.

In some embodiments, to avoid condensation of molten materialon the displacer surface, displacermay be preheated while it is positioned above the molten material. For example, as mentioned above, condensation or buildup of material on the displacer may be substantially avoided by preheating the displacer to a temperature that is about the same as or above the temperature of the molten material. This may be accomplished, for example, by exposing displacerto ambient temperatures that are present above molten material. In some implementations, a top surfaceof displacermay be sloped to allow molten materialto gravity-flow off of the top surface.

is a schematic cross-section side view of high-temperature molten material flow systemwith the position of displacerleading to a relatively low pressure fluid flow through output port, according to some embodiments. In contrast to the situation depicted in, wherein the top level of molten materialis below the height of output portso that there is zero flow into output port, displacermay be immersed into molten materialby an amount that results in the top level of the molten material being above output portby a distance. This situation leads to flow of the molten material out of vesselthrough output port, as indicated by arrow. This is in further contrast to the situation depicted inwherein the top level of the molten material is just above the bottom of output port. The flow inmay be substantially greater than the flow inbecause increasing the amount of displaced molten material may result in an increase in flow rate of the molten material through the output port. An increased flow rate into output portgenerally corresponds to an increase in pressure at the output port. Thus, changing the depth of displacer (e.g., the amount of immersion) may result in changing the pressure at the output port by increasing the height of the top of molten materialabove output port.

is a schematic cross-section side view of high-temperature molten material flow systemwith the position of displacerleading to a relatively high pressure fluid flow through output port, according to some embodiments. As explained above, increasing the amount of displaced molten material may result in an increase in flow rate of the molten material through output port. Comparing with the situation depicted in, displacerinis further immersed in molten materialand the molten material is thus further displaced so as to have its top surface higher above output port, by a distance, resulting in an increased flow rate indicated by arrow(again, in comparison to the situation of).

In some implementations, electronic controllerof flow systemmay increase a depth of immersion of displacerto increase the flow rate of molten materialthrough output portor, on the other hand, decrease a depth of immersion of the displacer to decrease the flow rate of the molten material through the output port. In some implementations, as molten materialis depleted by the gradual outflow of the molten material through the output port, the electronic controller may maintain a constant flow rate (e.g., a constant pressure) by gradually increasing a depth of immersion of displacerso that distance(or) is held constant. Height sensormay provide the height information of molten materialto electronic controllerto allow the electronic controller to operate actuatorfor controlling the depth of immersion of displacer, for example.

is a schematic cross-section side view of a high-temperature molten material flow systemthat may incorporate an MOE process, according to some embodiments. Flow systemmay be the same as or similar to flow system, in some examples, with added features of MOE.

Flow systemmay include a vesselconfigured to contain a molten materialand having an output portat a particular height in a side of the vessel. Output portmay be configured to convey a portion of the molten material that is at or above the particular height of the output port, as explained above for flow system. A displacermay be inside the vessel and configured to be immersed at variable depths in molten material. An actuatormay be used to immerse displacerat the variable depths in the molten material. In some implementations, vesseland displacermay be made of one or more refractory materials that can withstand refractory temperatures.

Flow systemmay include a height sensorto measure the height of high-temperature molten materialin vessel. An electronic controller, similar to or the same as electronic controller, may receive height measurements from height sensorperiodically, continuously, or from time to time. Flow systemmay include a lidthat covers the contents of vessel. The lid may be sealed at the interface with the top of vesselso gases, such as oxygen, may be contained in the vessel above molten material. Lidmay include a pass-through (e.g.,) that allows a shaftconnected to displacerto move vertically up and down by actuator. Similar to shaftof flow system, shaftmay impart its vertical motion to varying the amount of immersion of displacerin molten material.

During a process of MOE, the amount of immersion of displacermay be such that the top level of molten materialis below a bottom of output port, such as by a distance, for example. Electronic controllermay perform various functions or operations for flow systemincluding controlling the MOE process, which may involve applying an electric potentialto displacerso that the displacer acts as an anode of the MOE process. In this case, the electric potential may be positive (e.g., a positive voltage) and applied via an electrode. Counter to this, a negative potential may be applied to an electrodeat or near the bottom of vessel. Electrodemay in turn energize a molten iron cathodeat the bottom of vesselduring the MOE process.

In some implementations, the top level of molten materialmay be below the bottom of output port, as illustrated. In other implementations, however, the top level of the molten material may be above the bottom of the output port. As a result of the MOE process, molten materialmay be electrolyte, which may be iron-depleted and oxygen depleted molten regolith, for example. The MOE process generally pulls iron out of the molten material and accumulates the iron onto molten iron cathode. Also, the MOE process pulls oxygen out of the molten material to the anode (e.g., displacer) and into the spaceabove the top level of molten materialand below lid. Thus, a collection of oxygen gasaccumulates in space, from where it may be harvested for use in some example implementations.

In situations where the top level of the molten material is below the height of output port, molten material may not flow out of vesselbut oxygen gasmay do so. For example, output portmay lead to an oxygen-collecting portand a separate molten material-collecting port. When the top level of the molten material is above the top of output port, oxygen gasmay not flow out of vesselvia output port(though in some implementations there may be another output path for collecting oxygenfrom vessel) while molten material does so, blocking the oxygen gas from exiting.

During a process of collecting or harvesting molten material, which may be an electrolyte, electronic controllermay, in a continuing fashion, lower displacerso that the top level of the molten material remains above the bottom of output portand flow therethrough is maintained at a constant flow rate. This process may continue until the molten material is depleted, at which point displacermay begin to be partially immersed in molten iron cathode. When this occurs, molten materialflowing into output portmay become iron-rich. This situation may be undesirable for at least two reasons. First, a goal of collecting or harvesting molten materialmay be to acquire iron-depleted electrolyte. Second, it may be undesirable to deplete the mass of molten iron cathode. To avoid iron-rich molten material from exiting vesselvia output port, flow systemmay include a conductivity sensorin output portto measure conductivity or resistivity of molten materialflowing out of vesselthrough the output port. Electronic controllermay receive measurements from the conductivity sensor and control the amount of immersion of displacerbased on the measured conductivity of the molten material flow. For example, the conductivity of the molten material flow may depend, at least in part, on a concentration of iron therein. Thus, an increase in conductivity may indicate that the molten material flow into output portis beginning to include some of molten iron cathode. In some implementations, if the conductivity reaches a predetermined threshold, the electronic controller may decrease the amount of immersion of displacerto stop the flow into output port.

is a flow diagram of a processfor controlling high-temperature molten material flow, 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. For example, the process may be performed by electronic controlleror, at least in part, using flow systemsor. In some implementations, either of these electronic controllers may be a computer processor that includes any type of computing device having one or more processing units operably connected to computer-readable media. The computer-readable media may include two types of computer-readable media, namely computer storage media and communication media. Computer storage media may include volatile and non-volatile machine-readable, removable, and non-removable media implemented in any method or technology for storage of information (in compressed or uncompressed form), such as computer (or other electronic device) readable instructions, data structures, program modules, or other data to perform processes or methods described herein. Communication media may embody computer-readable instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave, or other transmission mechanism.

In some examples, computer-readable media may store instructions executable by electronic controlleror. Computer-readable media may also store instructions executable by an external CPU-based processor, executable by a GPU, and/or executable by an accelerator, such as an FPGA-based accelerator, a DSP-based accelerator, or any internal or external accelerator, just to name a few examples. Executable instructions stored on computer-readable media may include, for example, an operating system and other modules, programs, or applications that may be loadable and executable by electronic controlleror.

Though processmay be performed using other flow systems, for sake of example, processwill be described as being performed on flow system. At, the operator may position displacerabove or partially immersed in molten materialthat is contained in vesselwith an output portabove the molten material. The molten material may be molten lunar regolith, for example. In some flow systems, the displacer and the vessel may be made of refractory materials at least for the reason that the molten material may be at refractory temperatures.

At, the operator may select a flow rate, or one or more flow rates may already be a priori selected for the molten material to flow out of the vessel through the output port. For example, pre-selected flow rates may be established for specific times during process. At, the operator may immerse or further immerse the displacer in the molten material by an amount that is based, at least in part, on the selected flow rate(s). The operator may increase a depth of immersion of the displacer to increase the flow rate of the high-temperature molten material through the output port. Also, the operator may continuously increase a depth of immersion of the displacer to maintain a constant flow rate of the molten material through the output port.

In some implementations, the operator may, while the displacer is positioned above the molten material, preheat the displacer to a temperature that is substantially the same as or above the temperature of the molten material.

In some implementations, while the displacer is partially immersed in the molten material, the operator may apply an electric potential on the displacer to perform electrolysis on the molten material. The electric potential may be a positive potential so that the displacer acts as an anode of the electrolysis, as described above.

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.