Systems and methods for iron ore reduction via high-temperature electrical-based heating

Abstract

A heating zone can be generated adjacent to one or more electrode portions by applying one or more electric currents to the one or more electrode portions. A temperature within the heating zone can be at least 800 K. A mixture of iron ore and one or more reducing agents can be provided within the heating zone, such that the iron ore is directly reduced to iron. In some examples, the one or more reducing agents can include biomass particles, and / or the electrode portion(s) can be formed of a carbonized biomass. In some examples, the heating zone is generated by a plasma formed between a facing pair of electrode portions. In other examples, the heating zone is generated by Joule heating of the one or more electrode portions.

Description

[0001] SYSTEMS AND METHODS FOR IRON ORE REDUCTION VIA HIGH-TEMPERATURE EEECTRICAE-BASED HEATING

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS )

[0003] The present application claims the benefit of and priority under 35 U.S.C. § 119(e) to and is a non-provisional of U.S. Provisional Application No. 63 / 515,767, filed July 26, 2023, entitled “Reduction of Iron Ore to Iron using Renewable Carbon Sources and Plasma for Reduced Carbon Emissions,” which is hereby incorporated by reference herein in its entirety.

[0004] FIELD

[0005] The present disclosure relates generally to production of iron from iron ore, and more particularly, to reduction of iron ore to iron via high-temperature electrical-based heating.

[0006] BACKGROUND

[0007] A significant portion of global greenhouse gas emissions, including CO2 emissions, can be attributed to iron and steel production. The prevalent techniques for making iron (e.g., to produce steel) rely on oxidation of fossil fuels (e.g., coke or coal) to provide heat for the endothermic reaction to reduce iron ore to iron, as well as coke as a reducing agent in the reduction reaction. Such heating typically occurs in a blast furnace. For example, solid-gas (ore-CO) reduction in a blast furnace is typically conducted at -600-700 °C with a slow reaction rate, while solid-solid (ore-coke) reduction in a blast furnace is typically conducted at -800- 1200 °C with a limited reaction interface. While biomass has been gasified externally to produce syngas for use as a reducing agent in a blast furnace, such blast furnaces still require fossil fuel for heating. Moreover, using biomass in the blast furnace as a reducing agent instead of coke may be limited by poor reaction kinetics at the operating temperatures available for the blast furnace (e.g., 250-1700 °C). Further increasing the temperature in the blast furnace may not be possible due to lifetime of the refractory lining of the furnace, the maintenance complexity of the furnace, the furnace service life, cost of heating via coke, or other factors. Aspects of the disclosed subject matter may address one or more of the above-noted problems and disadvantages, among other things.

[0008] SUMMARY

[0009] Aspects of the disclosed subject matter provide systems and methods for iron ore reduction via high-temperature electrical-based heating. In some embodiments, heating is provided by applying an electric current to a pair of electrodes to generate a thermal plasma, and iron ore and one or more reducing agents can be heated by the thermal plasma to directly reduce the iron ore to iron. Alternatively, in some embodiments, heating is provided by flowing an electric current through one or more electrodes to cause Joule heating thereof, and iron ore and one or more reducing agents can be heated by the elevated temperature of the electrode(s) to directly reduce the iron to iron. In some aspects, the one or more reducing agents can include or be derived from a biomass (e.g., wood, bamboo, or other plant pieces), and / or portions of the electrodes can include or be formed from a biomass (e.g., carbonized wood, bamboo, or other plant pieces).

[0010] Aspects of the disclosed subject matter can provide a low net carbon emission process for direct reduction of iron ore to produce iron, for example, using renewable carbon sources (e.g., biomass as reducing agent(s) and / or electrode(s)) and electrical-based heating. In some aspects, the disclosed systems and methods can address the main issue of massive carbon dioxide emissions during conventional ironmaking, since renewable carbon sources (e.g., plants) can absorb carbon dioxide during growth. In some aspects, the disclosed systems and methods can significantly lower energy consumption, as compared to conventional ironmaking in blast furnaces, due to the high efficiency of the reduction process, for example, based on the biomassbased reducing agents and / or reducing agents produced during the heating (e.g., activated carbon generated by the thermal plasma). In some aspects, the disclosed systems and methods can provide a more cost-effective and / or environmentally-friendly alternative to conventional ironmaking in blast furnaces.

[0011] In one or more embodiments, a method can comprise generating a heating zone adjacent to one or more electrode portions by applying one or more electric currents to the one or more electrode portions. A temperature within the heating zone can be at least 800 K. The method can further comprise providing a mixture of iron ore and one or more reducing agents within the heating zone for a first time period, such that the iron ore is directly reduced to iron.

[0012] In one or more embodiments, a system for reducing iron ore to iron can comprise one or more reactors, a power supply, and a controller. Each reactor can comprise one or more electrode portions, and the power supply can be electrically connected to the one or more electrode portions. The controller can be operatively coupled to the power supply. The controller can comprise one or more processors and one or more non-transitory computer- readable storage media. The one or more electrode portions can be constructed to generate a heating zone adjacent to the one or more electrode portions when one or more electric currents are applied thereto. The computer-readable storage media can store computer-readable instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents to the one or more electrode portions such that a temperature within the heating zone is at least 800 K. The one or more reactors can be configured such that, when a mixture of iron ore and one or more reducing agents is within the generated heating zone for a first time period, the iron ore in the mixture is directly reduce to iron.

[0013] Any of the various innovations of this disclosure can be used in combination or separately. This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. The foregoing and other objects, features, and advantages of the disclosed technology will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Aspects will hereinafter be described with reference to the accompanying drawings, which have not necessarily been drawn to scale. Where applicable, some elements may be simplified or otherwise not illustrated in order to assist in the illustration and description of underlying features. Throughout the figures, like reference numerals denote like elements.

[0016] FIG. 1 is a simplified schematic diagram of a generalized iron ore reduction system, according to one or more embodiments of the disclosed subject matter.

[0017] FIG. 2 is a simplified process flow diagram for an iron fabrication method, according to one or more embodiments of the disclosed subject matter.

[0018] FIG. 3 depicts a generalized example of a computing environment in which the disclosed technologies may be implemented.

[0019] FIGS. 4A-4C are simplified schematic diagrams illustrating aspects of fabrication of electrodes from biomass, according to one or more embodiments of the disclosed subject matter.

[0020] FIG. 5A is a simplified schematic diagram illustrating a plasma system that compensates for electrode consumption, according to one or more embodiments of the disclosed subject matter.

[0021] FIG. 5B is a simplified schematic diagram illustrating a plasma system having a flow through configuration, according to one or more embodiments of the disclosed subject matter.

[0022] FIG. 5C is a simplified schematic diagram illustrating a plasma system having a pass through configuration for an iron ore sheet, according to one or more embodiments of the disclosed subject matter.

[0023] FIGS. 5D-5E are simplified schematic diagrams illustrating plasma systems having gravity feed configurations, according to one or more embodiments of the disclosed subject matter. FIG. 6A is a simplified schematic diagram illustrating a Joule heating system employing a single electrode in contact with a static reactant mixture, according to one or more embodiments of the disclosed subject matter.

[0024] FIG. 6B is a simplified schematic diagram illustrating a Joule heating system employing a single electrode with a gravity feed configuration, according to one or more embodiments of the disclosed subject matter.

[0025] FIG. 6C is a simplified schematic diagram illustrating a Joule heating system employing a pair of electrodes in contact with a static reactant mixture, according to one or more embodiments of the disclosed subject matter.

[0026] FIG. 6D is a simplified schematic diagram illustrating a Joule heating system employing a pair of electrodes with a flow through configuration, according to one or more embodiments of the disclosed subject matter.

[0027] FIG. 6E is a simplified schematic diagram illustrating a Joule heating system employing a tubular electrode with a gravity feed configuration, according to one or more embodiments of the disclosed subject matter.

[0028] FIG. 6F is a simplified schematic diagram illustrating a Joule heating system employing a plurality of tubular electrodes for parallel processing of reactant mixtures, according to one or more embodiments of the disclosed subject matter.

[0029] FIGS. 7A-7B are photographs of a fabricated experimental setup before and during plasma generation, respectively, employing carbonized wood electrodes.

[0030] FIG. 7C is a graph of measured plasma temperature versus applied current for the fabricated experimental setup of FIGS. 7A-7B.

[0031] FIGS. 8A-8B are photographs of another fabricated experimental setup before and during plasma generation, respectively, for direct reduction of iron ore.

[0032] FIGS. 8C-8D are photographs of iron produced by the fabricated experimental setup of FIGS. 8A-8B.

[0033] FIGS. 9A-9B are scanning electron microscopy (SEM) images of partially-delignified sawdust and iron ore, respectively, prior to mixing and heating via Joule heating electrodes.

[0034] FIG. 9C is an SEM image of the reduced iron produced after heating of the mixture of partially-delignified sawdust and iron ore.

[0035] FIG. 9D is a photograph of iron produced after heating of the mixture of partially- delignified sawdust and iron ore.

[0036] FIG. 9E shows the results of X-ray diffraction analysis (XRD) of the generated iron of FIGS. 9C-9D. FIGS. 10A-10B show the results of XRD of products resulting from heating of a mixture of sawdust and iron ore at a temperature of 1500-1800 K for 10 seconds, and at a temperature of 800-1300 K for 60 seconds, respectively.

[0037] DETAILED DESCRIPTION

[0038] General Considerations

[0039] For purposes of this description, certain aspects, advantages, and novel features of the disclosed subject matter are described herein. The disclosed methods and systems should not be construed as being limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects disclosed herein, alone and in various combinations and sub-combinations with one another. The methods and systems are not limited to any specific aspect or feature or combination thereof, nor do the disclosed aspects require that any one or more specific advantages be present, or problems be solved. The technologies from any aspect or example can be combined with the technologies described in any one or more of the other aspects or examples. In view of the many possible aspects to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated aspects of the disclosure are exemplary only and should not be taken as limiting the scope of the disclosed technology.

[0040] Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth below. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed methods can be used in conjunction with other methods. Additionally, the description sometimes uses terms like “provide” or “achieve” to describe the disclosed methods. These terms are high-level abstractions of the actual operations that are performed. The actual operations that correspond to these terms may vary depending on the particular implementation and are readily discernible by one skilled in the art.

[0041] The disclosure of numerical ranges should be understood as referring to each discrete point within the range, inclusive of endpoints, unless otherwise noted. Unless otherwise indicated, all numbers expressing quantities of components, molecular weights, percentages, temperatures, times, and so forth, as used in the specification or claims are to be understood as being modified by the term “about.” Accordingly, unless otherwise implicitly or explicitly indicated, or unless the context is properly understood by a person skilled in the art to have a more definitive construction, the numerical parameters set forth are approximations that may depend on the desired properties sought and / or limits of detection under standard test conditions / methods, as known to those skilled in the art. When directly and explicitly distinguishing aspects from discussed prior art, the numbers are not approximates unless the word “about,” “substantially,” or “approximately” is recited. Whenever “substantially,” “approximately,” “about,” or similar language is explicitly used in combination with a specific value, variations up to and including 10% of that value are intended, unless explicitly stated otherwise.

[0042] Directions and other relative references may be used to facilitate discussion of the drawings and principles herein but are not intended to be limiting. For example, certain terms may be used such as “inner,” “outer,” “upper,” “lower,” “top,” “bottom,” “interior,” “exterior,” “left,” right,” “front,” “back,” “rear,” and the like. Such terms are used, where applicable, to provide some clarity of description when dealing with relative relationships, particularly with respect to the illustrated aspects. Such terms are not, however, intended to imply absolute relationships, positions, and / or orientations. For example, with respect to an object, an “upper” part can become a “lower” part simply by turning the object over. Nevertheless, it is still the same part, and the object remains the same.

[0043] As used herein, “comprising” means “including,” and the singular forms “a” or “an” or “the” include plural references unless the context clearly dictates otherwise. The term “or” refers to a single element of stated alternative elements or a combination of two or more elements unless the context clearly indicates otherwise.

[0044] Although there are alternatives for various components, parameters, operating conditions, etc. set forth herein, that does not mean that those alternatives are necessarily equivalent and / or perform equally well. Nor does it mean that the alternatives are listed in a preferred order, unless stated otherwise. Unless stated otherwise, any of the groups defined below can be substituted or unsubstituted.

[0045] Unless explained otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one skilled in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, suitable methods and materials are described below. The materials, methods, and examples are illustrative only and not intended to be limiting. Features of the presently disclosed subject matter will be apparent from the following detailed description and the appended claims. Overview of Terms

[0046] The following are provided to facilitate the description of various aspects of the disclosed subject matter and to guide those skilled in the art in the practice of the disclosed subject matter.

[0047] Thermal Plasma'. A three-dimensional volume of electrons, ions, and / or excited molecules created and / or maintained by application of an electric field between electrodes. In some embodiments, the plasma can be generated via application of a direct current (DC) voltage, an alternating current (AC) voltage (e.g., radio frequency (RF), for example, in a range of 3 kHz to 300 GHz), or other waveform (e.g., pulsed voltage waveform) between the electrodes. In some embodiments, the temperature of the generated plasma is at least 1,000 K (e.g., in a range of 1,000-10,000 K, inclusive, such as 3,000-8,000 K, inclusive).

[0048] Biomass: A portion (e.g., a cut portion, via mechanical means or otherwise) of any photosynthetic eukaryote of the kingdom Plantae in its native state as grown. In some embodiments, the biomass comprises wood (e.g., hardwood or softwood), bamboo (e.g., any of Bambusoideae, such as but not limited to Moso, Phyllostachys vivax, Phyllostachys viridis, Phyllostachys bambusoides, Phyllostachys nigra, Guadua angustifolia, Bambusa emeiensis, Arundinaria gigantea, Chusquea culeou, and Bambusa vulgaris Villala), reed (e.g., any of common reed (Phragmites australis), giant reed (Arundo donax), Burma reed (Neyraudia reynaudiana). reed canary-grass (Phalaris arundinacea), reed sweet-grass (Glyceria maxima), small-reed (Calamagrostis species), paper reed (Cyperus papyrus), bur-reed (Sparganium species), reed-mace (Typha species), cape thatching reed (Elegia tectorum), and thatching reed (Thamnochortus insignis)), hemp (Cannabis sativa), or grass (e.g., a species selected from the Poales order or the Poaceae family). For example, the natural wood can be any type of hardwood (e.g., having a native lignin content in a range of 18-25 wt%) or softwood (e.g., having a native lignin content in a range of 25-35 wt%), such as, but not limited to, basswood, oak, poplar, ash, alder, aspen, balsa wood, beech, birch, cherry, butternut, chestnut, cocobolo, elm, hickory, maple, oak, padauk, plum, walnut, willow, yellow poplar, bald cypress, cedar, cypress, douglas fir, fir, hemlock, larch, pine, redwood, spruce, tamarackjuniper, and yew. Alternatively, in some embodiments, the biomass can be and / or comprise any type of plant having fibers composed of lignin and cellulose. For example, the biomass can be bagasse (e.g., formed from processed remains of sugarcane or sorghum stalks), straw (e.g., formed from processed remains of cereal plants, such as rice, wheat, millet, or maize), or cork (e.g., formed from the bark of the cork oak tree (Quercus suber)). Alternatively, in some embodiments, the biomass can be a waste product, such as wood waste (e.g., cork, wood chips, wood shavings, sawdust, etc.) or agricultural waste (e.g., hemp, flax, cereal straws, cereal husks, etc.), or a recycled material (e.g., paper, newspaper, cardboard, textile, etc.). In some embodiments, the biomass may be partially delignified, for example, using chemical processes described in U.S. Publication No. 2020 / 0223091, published July 16, 2020, and entitled “Strong and Tough Structural Wood Materials, and Methods for Fabricating and Use Thereof,” and U.S. Publication No. 2024 / 0083067, published March 14, 2024, and entitled “Waste-Free Processing for Lignin Modification of Fibrous Plant Materials, and Lignin-modified Fibrous Plant Materials,” which chemical processes are incorporated by reference herein.

[0049] Introduction

[0050] Disclosed herein are systems and methods for direct reduction of iron ore to iron via high-temperature electrical-based heating of the iron ore with one or more reducing agents. In some aspects, the electrical-based heating can allow the iron ore reduction to be powered using clean energy sources, such as solar and wind, rather than the fossil fuels required in conventional techniques. In some aspects, the systems and methods can employ renewable carbon sources, such as biomass, for example, as a reducing agent (or precursor thereto) and / or an electrode for the electrical-based heating (e.g., carbonized electrodes for generating a thermal plasma or for Joule heating). In some aspects, the higher efficiencies and / or temperatures (e.g., > 800 K, such as 3000-8000 K, inclusive, for plasma heating or > 2000 K for Joule heating) offered by the disclosed systems and methods can result in rapid reduction of iron ore to iron in seconds or minutes (e.g., < 5 minutes, such as 10-90 seconds, inclusive), as opposed to the hours required for iron ore reduction in conventional blast furnaces.

[0051] For example, FIG. 1 shows aspects of an iron ore reduction system 100. In the illustrated example, iron ore reduction system 100 includes a reactor 102, an electrical power supply 108, and a controller 110. The reactor 102 can include one or more electrodes (or electrode portions), to which one or more electric currents can be supplied from the electrical power supply 108 to generate a high temperature within a heating zone 104 adjacent to the electrode(s). Controller 110 can control operation of the electrical power supply 108, for example, timing, application, and / or magnitude of the voltage, current, or electrical power suppled to the electrode(s), which in turn may control characteristics of the heating zone 104 (e.g., on / off, temperature, etc.). In the illustrated example, controller 110 and the electrical power supply 108 may be considered part of a unitary system, for example, different modules of a control system 106. Alternatively, controller 110 and electrical power supply 108 could be separate devices that independently operate and / or communicate with each other. Iron ore 112 (e.g., particles) can be provided to the heating zone 104 within reactor 102 to undergo reduction to iron 116. In some embodiments, the iron ore 112 can be placed in the reactor 102 prior to any heating of the heating zone 104 (e.g., prior to application of electric current to electrode(s) of the reactor). The transition of the heating zone 104 to the desired elevated temperature for the reduction reaction can occur rapidly, for example, at a rate of at least 102K / s (e.g., > 103K / s). At the completion of the reduction reaction (e.g., < 5 minutes), heating can be terminated (e.g., by reducing or removing the applied voltage), and the produced iron can be removed from the heating zone 104. Alternatively, in some embodiments, the iron ore 112 can be flowed into and / or through the heating zone 104 during active heating (e.g., while electric current is applied to electrode(s) of the reactor). In such embodiments, the transit time through the heating zone 104 can be controlled and / or designed (e.g., based on length of the heating zone and / or flow rate) based on the time for completion of the reduction reaction (e.g., < 5 minutes), such that the material (e.g., some, most, or substantially all particles) exiting the heating zone 104 has been converted to iron 116.

[0052] One or more reducing agents 114 (e.g., particles) can be provided to heating zone 104 with the iron ore 112 to facilitate the reduction. In some embodiments, the reducing agent(s) 114 is formed of or comprises carbon. For example, iron ore 112 (mainly composed of Fe2O3 and / or Fe3O4) and the reducing agent(s) 114 can react to produce iron 116 by exposure to high temperature in the heating zone 104 based upon, but not limited to, the following reactions:

[0053] In some embodiments, the reducing agent(s) 114 can be, or be derived from, biomass. For example, the reducing agent can be in the form of plant material particles, such as sawdust. Alternatively or additionally, in some embodiments, the biomass can serve as precursor for reducing agent(s) to be formed within the heating zone 104. For example, exposure to high temperatures within the heating zone can quickly carbonize the biomass into activated carbon particles and / or gasify the biomass into syngas (e.g., with CO and H2), which carbon particles and syngas can function as the reducing agents 114.

[0054] In some embodiments, the reducing agent(s) 114 (or precursors thereto) are mixed with the iron ore 112 prior to heating zone 104. For example, the reducing agent(s) 114 and the iron ore 112 can both be in the form of particles having a size less than or equal to 1 mm, and the particles be combined together in a loose, but substantially uniformly dispersed mixture. In some embodiments, the reducing agent(s) 114 and the iron ore 112 can be mixed and ground together, for example, to reduce particle sizes thereof to less than or equal to 0.1 mm. Alternatively or additionally, in some embodiments, the reducing agent(s) 114 and the iron ore 112 can be combined together into a contiguous structure (e.g., sheet or brick) that is then provided to the heating zone (e.g., via conveyor or other translation means). Alternatively, in some embodiments, the reducing agent(s) 114 can be provided to the heating zone 104 via a separate feed stream, such that physical mixing with the iron ore 112 occurs situ within the heating zone 104.

[0055] Alternatively, in some embodiments, one, some, or all of the reducing agent(s) 114 can be provided to the heating zone 104 and / or generated within the heating zone 104, without prior physical mixing of solid particles with the iron ore 112. In some embodiments, the reducing agent(s) 114 can comprise a reducing gas (e.g., syngas, hydrogen gas, ammonia, etc.) supplied to the heating zone 104, for example, as a separate feed stream or as a carrier gas for the iron ore 112. Alternatively or additionally, in some embodiments, the reducing agent(s) 114 can comprise carbon generated within the heating zone 104 by the high-temperature operation of the electrode(s), for example, activated carbon resulting from consumption of carbon-based electrodes (e.g., carbonized biomass).

[0056] In some embodiments, the output from the reactor 102 may be primarily iron 116 or iron-based, for example, with substantially all of the reducing agent(s) 114 consumed by the reduction reaction. Alternatively, in some embodiments, other particles and / or gases may be output from the reactor 102 along with the iron 116. For example, the output gases may include, but are not limited to, CO, CO2, and H2O (e.g., when hydrogen gas is added to heating zone). In some embodiments, the output gases may be collected from the reactor for capture and / or separate use. In some embodiments, the reduction of the iron ore 112 to iron 116 in the heating zone 104 may be such that a majority (> 50%), most (> 75%), or substantially all (> 90%) of the iron 116 output from the reactor 102 is in the form of a-Fe (e.g., having a body-centered cubic (BCC) crystal structure and being ferromagnetic below 1044 K).

[0057] In some embodiments, the reactor 102 comprises a plasma heating configuration 120a, where a voltage is applied between a pair of opposing electrodes 122, 124 so as to form a thermal plasma in the gap between the facing surfaces of the electrodes 122, 124 to function as the heating zone 104a. Once the thermal plasma is formed, electric current 126 flows between the electrodes 122, 124 via the plasma in the gap. Although the plasma is shown as being generated between the electrodes 122, 124 in the illustrated example, it may also be formed in or extend to a region outside the gap between electrodes (e.g., via application of an appropriate magnetic field), and iron ore 112 and / or reducing agents 114 may be provided to (e.g., flowed through) this region rather than within the gap between electrodes 122, 124. In some embodiments, aspects of the plasma heating configuration 120a can be similar to systems and / or methods disclosed in International Application No. PCT / US23 / 34378, filed October 3, 2023 and entitled “Volumetric Plasmas, and Systems and Methods for Generation and Use Thereof,” which systems and methods are hereby incorporated by reference herein. For example, in some embodiments, the thermal plasma can be generated at a low breakdown voltage (e.g., < 100 V, such as 10-80 V, inclusive) and can reach ultrahigh temperatures (e.g., up to 10000 K, such as 3000-8000 K, inclusive) at low current (e.g., < 50 A, such as 15-45 A, inclusive) and / or current density (e.g., 3-9 A / cm2, inclusive). In some embodiments, the characteristics of the thermal plasma (e.g., temperature, distribution, size, and / or location of the heating zone 104a, etc.) can be adjusted by controlling the gap (e.g., changing size of the gap, with smaller gaps corresponding to higher temperatures) and flow (e.g., particle and / or gas flows) between the electrodes 122, 124, selecting or altering the gas pressure between the electrodes (e.g., with higher pressures corresponding to higher temperatures), varying applied electrical power (e.g., with higher powers corresponding to higher temperatures), applying an external magnetic field, etc. In some embodiments, the thermal plasma can exhibit high temperatures (e.g., > 1000 K, for example, 1000-10000 K) over relatively large areas (e.g., > 1 cm2).

[0058] In some embodiments, the plasma heating configuration 120a is performed in an atmosphere of inert gas (e.g., noble gas, such as argon) between the electrodes 122, 124. Alternatively or additionally, in some embodiments, the plasma heating configuration is performed in an atmosphere comprising nitrogen, in addition to or in place of the inert gas, for example to allow for higher temperatures of the thermal plasma. Alternatively or additionally, in some embodiments, the plasma heating configuration 120a is performed in an atmosphere comprising hydrogen or a reducing gas between the electrodes 122, 124. For example, the atmosphere for plasma heating can comprise a noble gas, nitrogen, hydrogen, syngas, ammonia, or mixtures thereof (e.g., N-Ar, H-Ar, N-H, etc.).

[0059] Alternatively, in some embodiments, the reactor 102 comprises a Joule heating configuration, for example, a symmetric Joule heating configuration 120b, where a voltage is applied across separate electrodes 128a, 128b so as to induce a respective electric current 130a, 130b to flow therethrough (e.g., in a plane substantially perpendicular to a direction of a gap between the electrodes 128a, 128b), thereby causing the temperatures of the electrodes 128a, 128b to increase due to Joule heating. Iron ore and reducing agent(s) can be provided to the heating zone 104b formed by the gap between electrodes 128a, 128b so as to be heated by the elevated temperature electrodes 128a, 128b. In some embodiments, the iron ore and / or reducing agent(s) can be in direct contact with one or both of the electrodes 128a, 128b, such that the iron ore and / or reducing agent(s) are conductively heated by the respective electrode 128a, 128b. Alternatively, in some embodiments, the iron ore and / or reducing agents are spaced from one or both of the electrodes 128a, 128b (e.g., in a flow through configuration), such that the iron ore and / or reducing agent(s) are radiatively heated by the respective electrode 128a, 128b. In either case, the applied currents 130a, 130b only flow through the respective electrodes 128a, 128b, without passing through the heating zone 104b and material therein.

[0060] Alternatively, in some embodiments, the reactor 102 comprises an asymmetric Joule heating configuration 120c, where a voltage is applied across a single electrode 132 so as to include an electric current 134 to flow therethrough, thereby causing the temperature of the electrode 132 to increase due to Joule heating. Iron ore and reducing agent(s) can be provided to the heating zone 104c formed adjacent to the electrode 132, as to be heated by the elevated temperature electrode 132. In some embodiments, the iron ore and / or reducing agent(s) can be in direct contact with and conductively heated by electrode 132. Alternatively, in some embodiments, the iron ore and / or reducing agent(s) can be spaced from and radiatively heated by electrode 132. In either case, the applied current 134 only flows through the electrode 132 without passing into the heating zone 104c and material therein.

[0061] In some embodiments, aspects of the symmetric Joule heating configuration 120b and / or the asymmetric Joule heating configuration 120c can be similar to systems and / or methods disclosed in U.S. Publication No. 2018 / 0369771, published December 27, 2018, and entitled “Nanoparticles, and Systems and Methods for Synthesizing Nanoparticles through Thermal Shock,” U.S. Publication No. 2019 / 0161840, published May 30, 2019, and entitled “Thermal Shock Synthesis of Multielement Nanoparticles,” and U.S. Publication No. 2022 / 0219986, published July 14, 2022, and entitled “High Temperature Sintering Systems and Methods,” which systems and methods are hereby incorporated by reference herein. In some embodiments, the Joule heating configurations 120b, 120c are performed in an atmosphere of inert gas (e.g., noble gas, such as argon). Alternatively or additionally, in some embodiments, the Joule heating configuration can be performed with a reducing agent flowing into and / or through the heating zone, for example, syngas and / or carbon monoxide.

[0062] In some embodiments, the Joule heated electrode (and / or material in the heating zone) can reach high temperatures (e.g., > 800 K) at relatively low voltage (e.g., < 50 V, such as 5-50 V, inclusive) and / or relatively low current (e.g., < 50 A, such as 5-50 A, inclusive). For example, the temperature of the heating zone can be adjusted by controlling the electrical power (e.g., current) applied to the electrodes (with higher powers corresponding to higher temperatures). In some embodiments, when the iron ore and / or reducing agent(s) are in direct contact with at least one electrode (or portion thereof), the temperature can be controlled to be, for example, 800-1300 K, inclusive, and a duration of high temperature exposure can be, for example, 30-90 s, inclusive. Alternatively, in some embodiments, when the iron ore and / or reducing agent(s) are spaced from each electrode, the temperature can be controlled to be, for example, at least 2000 K, and a duration of the high temperature exposure can be, for example, at least 10 s (e.g., 60-300 s, inclusive).

[0063] Iron Ore Reduction Methods

[0064] FIG. 2 illustrates aspects of a method 200 for iron ore reduction via high-temperature electrical-based heating. The method 200 can initiate at process block 202, where one or more electrodes can be provided. In some embodiments, the provision of process block 202 can include arranging electrodes (or portions thereof) in a desired heating configuration, e.g., for providing a heating zone within one or more reactors. In some embodiments, when heating via a thermal plasma is desired, a pair of opposing electrodes (or portions thereof) can be arranged with facing portions spaced apart from each other by a gap, and the heating zone can be formed between the facing portions, for example, similar to the plasma heating configuration 120a of FIG. 1. Alternatively, in some embodiments, when heating via symmetric Joule heating is desired, a pair of electrode portions (or opposing electrodes) can be arranged with facing surfaces spaced apart from each other by a gap, and the heating zone can be formed between the facing surfaces, for example, similar to the symmetric Joule heating configuration 120b of FIG. 1. Alternatively, in some embodiments, when heating via asymmetric Joule heating is desired, a single electrode (or portion thereof) can be arranged such that the heating zone is adjacent to the single electrode, for example, similar to the asymmetric Joule heating configuration 120c of FIG. 1

[0065] Alternatively or additionally, in some embodiments, the provision of process block 202 can include fabricating the one or more electrodes (or portions thereof adjacent to and / or facing the heating zone). In some embodiments, the electrode(s) can comprise and / or be formed of biomass. For example, the electrode(s) can be formed by subjecting a piece of biomass (e.g., wood, bamboo, plant husk, etc.) to carbonization (e.g., heating in a furnace in a noble gas atmosphere for - 2 hours at a temperature of 800-1100 °C, inclusive). Alternatively, in some embodiments, the electrode(s) can be formed by compressing together multiple particles of the same or different biomass (e.g., sawdust, bamboo, plant husk, etc.) to form a contiguous structure, and then subjecting the continuous structure to carbonization. In some embodiments, the biomass, or structure formed therefrom, can be subjected to roughening after carbonization. Alternatively, the biomass, or structure formed therefrom can be subjected to roughening prior to carbonization, which roughened surface may be retained, at least in part, after the carbonization. For example, the roughened surface of the resulting carbonized biomass electrode can assist in plasma formation for the plasma heating configurations.

[0066] The method 200 can proceed to process block 204, where one or more reducing agents can be provided. In some embodiments, the reducing agent(s) can comprise and / or be derived from biomass. For example, in some embodiments, the reducing agent(s) can be sawdust. Alternatively or additionally, in some embodiments, the reducing agent(s) can be or comprise a reducing gas, such as but not limited to hydrogen, syngas, carbon monoxide, or ammonia. In some embodiments, the biomass for the reducing agent(s) can be processed for size, morphology, and / or composition. For example, in some embodiments, a particle size of the biomass can be reduced via grinding, milling, crushing, ultrasonic processing, and / or pressure- induced homogenization.

[0067] Alternatively or additionally, in some embodiments, the biomass for the reducing agent(s) can have at least some lignin removed therefrom (partial delignification), for example, removing 5-15 wt% of the native lignin (e.g., such that the partially-delignified biomass has a lignin content less than 20 wt%). In some embodiments, the partial delignification can provide a more porous structure for the resulting biomass. The increased porosity of the partially- delignified biomass can provide a higher surface area for interaction with the iron ore and / or allow for easier absorption or entanglement with the iron ore. Moreover, the partial delignification can expose more cellulose fibrils and microfibers of the biomass, which improves accessibility of the iron ore thereto and can thereby increase efficiency of the reduction reaction. Alternatively or additionally, in some embodiments, the partial delignification process can help remove undesirable components remaining in the biomass, such as trace amounts of pectin, wood ash, oil components (e.g., fatty acid), etc., which could otherwise compromise reduction reaction efficiency and / or result in undesirable byproducts.

[0068] Alternatively or additionally, in some embodiments, the provision of process block 204 can include providing precursors to one or more reducing agents, for example, when biomass provided to the heating zone of a reactor is converted by the high temperature therein to activated carbon and / or syngas, which in turn acts as a reducing agent for the reduction of the iron ore. Alternatively or additionally, in some embodiments, the provision of process block 204 can include generating one or more reducing agents within the heating zone during process block 208, for example, where activated carbon generated by consumption of carbon-based electrodes (e.g., carbonized biomass) to generate the high temperature in the heating zone acts as a reducing agent for the reduction of the iron ore.

[0069] The method 200 can proceed to process block 206, where the iron ore can be combined with the reducing agent(s). In some embodiments, the combining of process block 206 can occur within the heating zone, for example, where the iron ore and reducing agent(s) are separately supplied to the heating zone, where the reducing agent(s) are generated from precursors within the heating zone, or where the reducing agent(s) are emitted by the electrodes in generating the high temperature. Alternatively or additionally, in some embodiments, the combining of process block 206 can occur prior to the heating zone, for example, by physically mixing together particles of iron ore and reducing agent(s). In some embodiments, the mixing can include grinding (e.g., ball milling) the particles to have a reduced size (e.g., < 1 mm, such as < 0.1 mm). Alternatively or additionally, in some embodiments, the combining of process block 206 can include forming the mixture of iron ore and reducing agent particles into a contiguous structure, for example, by compressing into a sheet or brick.

[0070] The method 200 can proceed to process block 208, where the iron ore and reducing agent(s) can be subjected to heating in a heating zone. In some embodiments, the heating zone can be adjacent to one or more electrode portions in a reactor, for example, between a facing pair of electrode surfaces. For example, the heating of process block 208 can be at a temperature of at least 800 K, which can be generated by applying one or more electric currents to the one or more electrode portions. In some embodiments, the duration of the heating of process block 208 can be controlled based on a speed of the reactants (e.g., iron ore) and / or products (e.g., iron) moving through the heating zone (e.g., based on carrier gas flow rate, gravity feed, conveyor speed, etc.). Alternatively or additionally, the duration of the heating can be controlled based on activation of the electrodes (e.g., electric current control).

[0071] In some embodiments, biomass can be provided with the iron ore to the heating zone and subjected to heating in process block 208. As noted above, the biomass can be quickly converted by the high temperature to syngas (e.g., mainly CO and H2) and / or activated carbon particles, for example, during an initial part of the heating of process block 208. The syngas and / or activated carbon particles can then be uses as a reductant for rapid and highly efficient reduction of the iron ore for the remainder of the heating of process block 208. Activated carbon from the electrodes, for example, vaporized by the high temperature and / or plasma generation, can function as a further reductant during the heating of process block 208. When the biomass includes hydrogen (e.g., as with sawdust), the hydrogen can be combined with oxygen to form water vapor, which may be further advantageous for the reduction reaction. Thus, in some embodiments, iron ore can be directly reduced to iron by the heating of process block 208 in minutes (e.g., < 5 minutes) or even seconds (e.g., 10-90 seconds), as compared to hours for conventional processes in blast furnaces.

[0072] In some embodiments, when the heating zone is generated using a plasma heating configuration (e.g., 120a in FIG. 1), the heating of process block 208 may be at a temperature of 3000-8000 K for a duration of less than 5 minutes. Alternatively, in some embodiments, when the heating zone is generated using a Joule heating configuration and the heating of the iron ore and / or reducing agent(s) is primarily via conduction, the heating of process block 208 may be at a temperature of 800-1300 K for a duration of 30-90 seconds. Alternatively, in some embodiments, when the heating zone is generated using a Joule heating configuration and the heating of the iron ore and / or reducing agent(s) is primarily via radiation, the heating of process block 208 may be at a temperature of at least 2000 K for a duration of at least 10 seconds.

[0073] In some embodiments, during the heating of process block 208, the processing environments (e.g., heating zone) and / or chambers (e.g., reactor) may remain stationary or substantially stationary. Alternatively or additionally, in some embodiments, during the heating of process block 208, the reactants (e.g., iron ore and / or reacting agent(s)) and / or products (e.g., iron) may remain stationary or substantially stationary. In some embodiments, the temperature of the heating zone can be adjusted, for example, during the heating of process block 208 and / or when transitioning between different phases or types of processing during or after process block 208. Alternatively or additionally, in some embodiments, the heating zone can be at a uniform (or substantially uniform) high temperature for part of process block 208, and then the heating can be altered such that the heating zone moves to a different uniform (or substantially uniform) high temperature for another part of process block 208. In some embodiments, the heating zone may be controlled and / or maintained during process block 208 at one or more ultrahigh temperatures (e.g., at different times and / or different locations within the reactor). In some embodiments, temperatures outside the reactor may remain unaffected (or substantially unaffected) by the heating during process block 208, for example, such that a safe temperature (e.g., room temperature) is exhibited by one or more external surfaces of the reactor.

[0074] The method 200 can proceed to optional process block 210, where the iron resulting from process block 208 can be separated from other products. In some embodiments, a majority (> 50%), most (> 75%), or substantially all (> 90%) of the iron output from the reactor is in the form of a-Fe, and the separation of process block 208 can be performed, for example, using a magnet. The method 200 can proceed to process block 212, where the iron is used or prepared for use. In some embodiments, the iron can be alloyed to make steel, for example, using known processes.

[0075] The method 200 can proceed to decision block 214, where it is determined if the electrodes (or portions thereof) used for the heating in process block 208 have degraded. In some embodiments, surfaces of the electrodes may erode over time due to the generated plasma and / or carbon vaporization at the generated high temperatures. The degree of degradation can be assessed by monitoring aspects of the heating of process block 208 (e.g., plasma characteristics, measured temperature versus applied current, etc.), and / or by measuring the electrodes after the heating of process block 208 (e.g., with the electrodes de-energized and / or at a safe temperature).

[0076] If there is no or negligible degradation, the method 200 can return to process block 204, for example, to repeat the reduction with a next batch of reactants (e.g., iron ore and / or reducing agent(s)). If the degradation is within a predetermined range and the reactor is configured with movable electrodes, the method 200 can proceed from decision block 214 to process block 218, where one or both electrodes (or portions thereof) can be moved (e.g., via one or more translation devices) toward the other to compensate for the degradation, for example, return a size of the gap between electrodes to its original value prior to any degradation. In some embodiments, the adjustment of process block 218 can occur after the heating of process block 208 (e.g., after the electrodes have been de-energized and / or the heating zone has cooled to a safe temperature). After the adjustment, the method can return to process block 204, for example, to repeat the reduction with a next batch of reactants. Alternatively, in some embodiments, the adjustment of process block 218 can occur during process block 208, for example, to dynamically adjust the size of the gap between electrodes during the heating and / or while reactants are within the heating zone.

[0077] If the degradation is outside of a predetermined range, or if the degradation is within the predetermined range but the reactor lacks movable electrodes, the method 200 can proceed from decision block 214 to process block 216, where one or more of the electrodes (or degraded portions thereof) can be removed. The method 200 can then return to process block 202, where new electrodes (or electrode portions) may be provided, and the process repeated for a next batch of reactants.

[0078] Although some of blocks 202-218 of method 200 have been described as being performed once, in some embodiments, multiple repetitions of a particular process block may be employed before proceeding to the next decision block or process block. In addition, although blocks 202-218 of method 200 have been separately illustrated and described, in some embodiments, process blocks may be combined and performed together (simultaneously or sequentially). Moreover, although FIG. 2 illustrates a particular order for blocks 202-218, embodiments of the disclosed subject matter are not limited thereto. Indeed, in certain embodiments, the blocks may occur in a different order than illustrated or simultaneously with other blocks. In some embodiments, method 200 may comprise only some of blocks 202-218 of FIG. 2.

[0079] Computer Implementation Examples

[0080] FIG. 3 depicts a generalized example of a suitable computing environment 331 in which the described innovations may be implemented, such as but not limited to method 200, control system 106, power supply 108, and / or controller 110. The computing environment 331 is not intended to suggest any limitation as to scope of use or functionality, as the innovations may be implemented in diverse general-purpose or special-purpose computing systems. For example, the computing environment 331 can be any of a variety of computing devices (e.g., desktop computer, laptop computer, server computer, tablet computer, etc.).

[0081] With reference to FIG. 3, the computing environment 331 includes one or more processing units 335, 337 and memory 339, 341. In FIG. 3, this basic configuration 351 is included within a dashed line. The processing units 335, 337 execute computer-executable instructions. A processing unit can be a central processing unit (CPU), processor in an application-specific integrated circuit (ASIC), or any other type of processor (e.g., hardware processors, graphics processing units (GPUs), virtual processors, etc.). In a multi-processing system, multiple processing units execute computer-executable instructions to increase processing power. For example, FIG. 3 shows a central processing unit 335 as well as a graphics processing unit or co-processing unit 337. The tangible memory 339, 341 may be volatile memory (e.g., registers, cache, RAM), non-volatile memory (e.g., ROM, EEPROM, flash memory, etc.), or some combination of the two, accessible by the processing unit(s). The memory 339, 341 stores software 333 implementing one or more innovations described herein, in the form of computer-executable instructions suitable for execution by the processing unit(s).

[0082] A computing system may have additional features. For example, the computing environment 331 includes storage 361, one or more input devices 371, one or more output devices 381, and one or more communication connections 391. An interconnection mechanism (not shown) such as a bus, controller, or network interconnects the components of the computing environment 331. Typically, operating system software (not shown) provides an operating environment for other software executing in the computing environment 331, and coordinates activities of the components of the computing environment 331.

[0083] The tangible storage 361 may be removable or non-removable, and includes magnetic disks, magnetic tapes or cassettes, CD-ROMs, DVDs, or any other medium which can be used to store information in a non-transitory way, and which can be accessed within the computing environment 331. The storage 361 can store instructions for the software 333 implementing one or more innovations described herein.

[0084] The input device(s) 371 may be a touch input device such as a keyboard, mouse, pen, or trackball, a voice input device, a scanning device, or another device that provides input to the computing environment 331. The output device(s) 381 may be a display, printer, speaker, CD- writer, or another device that provides output from computing environment 331.

[0085] The communication connection(s) 391 enable communication over a communication medium to another computing entity. The communication medium conveys information such as computer-executable instructions, audio or video input or output, or other data in a modulated data signal. A modulated data signal is a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media can use an electrical, optical, radio-frequency (RF), or another carrier.

[0086] Any of the disclosed methods can be implemented as computer-executable instructions stored on one or more computer-readable storage media (e.g., one or more optical media discs, volatile memory components (such as DRAM or SRAM), or non-volatile memory components (such as flash memory or hard drives)) and executed on a computer (e.g., any commercially available computer, including smart phones or other mobile devices that include computing hardware). The term computer-readable storage media does not include communication connections, such as signals and carrier waves. Any of the computer-executable instructions for implementing the disclosed techniques as well as any data created and used during implementation of the disclosed embodiments can be stored on one or more computer-readable storage media. The computer-executable instructions can be part of, for example, a dedicated software application or a software application that is accessed or downloaded via a web browser or other software application (such as a remote computing application). Such software can be executed, for example, on a single local computer (e.g., any suitable commercially available computer) or in a network environment (e.g., via the Internet, a wide-area network, a local-area network, a client-server network (such as a cloud computing network), or any other such network) using one or more network computers.

[0087] For clarity, only certain selected aspects of the software-based implementations are described. Other details that are well known in the art are omitted. For example, it should be understood that the disclosed technology is not limited to any specific computer language or program. For instance, aspects of the disclosed technology can be implemented by software written in C++, Java™, Python®, and / or any other suitable computer language. Likewise, the disclosed technology is not limited to any particular computer or type of hardware. Certain details of suitable computers and hardware are well known and need not be set forth in detail in this disclosure.

[0088] It should also be well understood that any functionality described herein can be performed, at least in part, by one or more hardware logic components, instead of software. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs), Program- specific Integrated Circuits (ASICs), Program- specific Standard Products (ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), etc.

[0089] Furthermore, any of the software-based embodiments (comprising, for example, computer-executable instructions for causing a computer to perform any of the disclosed methods) can be uploaded, downloaded, or remotely accessed through a suitable communication means. Such suitable communication means include, for example, the Internet, the World Wide Web, an intranet, software applications, cable (including fiber optic cable), magnetic communications, electromagnetic communications (including RF, microwave, and infrared communications), electronic communications, or other such communication means. In any of the above-described examples and embodiments, provision of a request (e.g., data request), indication (e.g., data signal), instruction (e.g., control signal), or any other communication between systems, components, devices, etc. can be by generation and transmission of an appropriate electrical signal by wired or wireless connections.

[0090] Fabrication of Biomass Electrodes

[0091] FIG. 4A illustrates aspects of fabrication 400 of an electrode for electrical-based heating in an iron ore reduction reactor from a piece 402 of biomass. In some embodiments, the biomass piece 402 can be and / or comprise a piece of plant material, such as wood or bamboo. Prior to processing, the biomass piece 402 can be cut to have a desired size for a particular electrode application (e.g., taking into account shrinkage after the carbonization process) and optionally dried (e.g., in an air furnace at 260 °C for 2 hours) to remove, or at least reduce residual moisture in the biomass piece 402 prior to carbonization. Prior to carbonization, the biomass piece 402 can be secured within a thermal restraint fixture 404 (e.g., a pair of graphite weight loading pads), for example, maintain the shape of the piece and / or facilitate uniform heating during the carbonization process. The assembly of fixture 404 and biomass piece 402 can be loaded into a furnace 406 (e.g., argon-protected furnace), where the biomass piece 402 can be subjected to heating in an oxygen-free (or at least limited oxygen) atmosphere to carbonize the biomass piece. Alternatively, in some embodiments, the biomass piece 402 can be provided to the furnace 406 without any fixture 404, for example, where the heating rate of the carbonization is carefully controlled. The biomass piece 402 (with or without fixture 404) can be heated in the furnace 406, for example, at a heating rate -100 °C / hour to a maximum temperature of 800-1100 °C, which maximum temperature can be maintained for -2 hours. The resulting carbonized biomass 408 can have a resistivity of 1-10 Q-cm, inclusive. In some embodiments, the carbonized biomass 408 can be used as an electrode in either plasma heating configurations or Joule heating configurations.

[0092] FIG. 4B illustrates aspects of fabrication 410 of another electrode for electrical-based heating in an iron ore reduction reactor from a plurality of biomass particles 414. In some embodiments, the biomass particles 414 can comprise or be derived from plant material, for example, sawdust, bamboo pieces, plant husks, etc. In some embodiments, the biomass particles 414 can be or can be derived from the same type of plant material (e.g., same species of wood). Alternatively, in some embodiments, the biomass particles 414 can be or can be derived from different types of plant materials (e.g., different species of wood, combinations of different plants, etc.). In the illustrated example, the biomass particles 414 can initially be provided as a loose agglomeration 412, which can be compacted to form a contiguous sheet or block 416. The compacted block 416 can then be loaded into a furnace 406 (e.g., with or without thermal restraint fixture), where the block 416 can be subjected to heating to carbonize the compacted block in a manner similar to that described above for FIG. 4A. The resulting carbonized block 418 can be used as an electrode in either plasma heating configurations or Joule heating configurations.

[0093] In some embodiments, the surface of the electrode can be roughened prior to or after carbonization, for example, to facilitate ignition and / or spread of the thermal plasma when used as an electrode in a plasma heating configuration. For example, FIG. 4C illustrates aspects of fabrication 420 of a biomass-based electrode with surface roughening. In some embodiments, a biomass piece 422 is initially provided, which piece 422 can be either a solid piece of biomass (e.g., similar to piece 402 in FIG. 4A) or a compacted block of biomass particles (e.g., similar to block 416 in FIG. 4B). At least one surface 426, which is designed to face an opposing electrode in the plasma heating setup, can be subjected to roughening, thereby forming a roughened piece 424. For example, the roughening can be provided by cutting, abrading, scratching, sanding, grinding, sandblasting, etching, laser ablation, wire brushing, or any other means for roughening of surface 426. In some embodiments, the surface 426 after the roughening can have an average roughness (Ra) of at least 10 pm, for example, greater than or equal to 100 pm. Alternatively or additionally, the surface 426 after the roughening can comprise peaks having a height of at least 100 pm and / or troughs having a depth of at least 100 pm (e.g., as measured by a profilometer). The roughened piece 424 can then be loaded into a furnace 406 (e.g., with or without thermal restraint fixture), where the piece 42 can be subjected to heating to carbonize the roughened piece 424 in a manner similar to that described above for FIG. 4A. The resulting carbonized piece 428 can retain the roughened surface 430 after carbonization, for example, with the shape and / or roughness of surface 430 after carbonization being substantially the same as that of surface 426 prior to carbonization.

[0094] Plasma Heating Configurations

[0095] FIG. 5A illustrates aspects of operation of a plasma heating configuration with gap adjustment. At a first time 500, opposing electrodes 502, 504 can be spaced apart by a gap between facing surfaces 512, 514 of thickness, gl. A plasma 506 can be generated between the facing surfaces 512, 514 of the opposing electrodes 502, 504, and the heating zone 508 for iron ore reduction can thus be formed within the gap. Over time, however, the electrodes (or surface portions thereof) may be slowly consumed or degraded by the plasma operation, such that a size of the degraded electrodes 502’, 504’ is less and / or a thickness of the gap increases, e.g., such that new facing surfaces 522, 524 provide a gap with a larger thickness, g2, as shown at second time 520. This change in gap thickness can alter the characteristics of the plasma (e.g., lower temperature and / or intensity) and / or require changes in applied power to maintain the same plasma characteristics. In some embodiments, one or both of the electrodes (or portions thereof) can be moved toward the other to compensate for the degradation and corresponding change in gap thickness, for example, to move the new facing surfaces 522, 524 back to the location of original facing surfaces 512, 514 and thereby recover the original gap thickness, gl, as shown at third time 530.

[0096] In the illustrated example, the first electrode 502 is mounted on and / or supported by a first translation stage 510a having a motor, and the second electrode 504 is mounted on and / or supported by a second translation stage 510b having a motor. The first and second translation stages 510a, 510b can be configured to move the first and second electrodes toward or away from each other, so as to change a size of the gap therebetween. Other configurations for the first and second translation stages are also possible according to one or more contemplated embodiments, for example, having a translation stage for one of the electrodes while the other remains in a fixed location, mounting both electrodes on a common translation stage, using a translation stage that does not employ a motor, or any other means for varying the size of the gap between the electrodes.

[0097] In some embodiments, the electrode movement can be performed continuously, for example, at a rate substantially corresponding to that at which the electrodes (or portions thereof) are consumed so as to maintain the gap thickness at a substantially constant thickness. Alternatively, in some embodiments, the electrode movement can be performed periodically, for example, when a gap thickness exceeds a predetermined threshold and / or when plasma characteristics are outside a predetermined range. For example, the electrode movement may occur during plasma generation for iron ore reduction heating and based on detecting a condition or state of the electrodes during the plasma generation. Alternatively or additionally, the electrode movement may occur at a time when plasma generation and / or iron ore processing has been paused, for example, based on detecting a condition or state of the electrodes during the processing. Alternatively or additionally, the electrode movement may occur in response to detecting a condition or state of the electrodes outside of processing, for example, measuring gap thickness and / or electrode widths during a pause in processing or downtime between iron ore batches.

[0098] FIG. 5B illustrates aspects of a plasma heating configuration 540 with flow-through reactants. In the illustrated example, a mixture 550 of iron ore particles 112 and reducing agent(s) 114 (e.g., biomass particles) is conveyed through the heating zone 548 formed between electrodes 542, 544, where the plasma 546 generated therein subjects the mixture 550 to a high temperature (e.g., 3000-8000 K). The mixture 550 can be carried into and through the heating zone 548 between the electrodes 542, 544, and / or the products (e.g., iron 116) can be carried from the heating zone 548 by a carrier gas flow, for example, an inert gas, nitrogen, and / or a reducing gas (e.g., syngas, hydrogen, ammonia, etc.) The reaction temperature can be adjusted via the electric current applied to electrodes 542, 544, the gap distance between the electrodes 542, 544, and / or gas pressure within the heating zone 548. A duration of the heating can be determined by residence time of the reactants within the heating zone, for example, based on a length of the heating zone and / or generated plasma, and a speed of the reactants (e.g., determined by carrier gas flow rate).

[0099] In the illustrated example of FIG. 5B, the orientation of the heating zone 548, the flow of reactants (and / or carrier gas) into the heating zone, the flow within the heating zone, and the flow of products from the heating zone is substantially horizontal. However, embodiments of the disclosed subject matter are not limited thereto. Rather, in some embodiments, the orientation of the heating zone and / or one or more of the flows can be vertical (e.g., aligned with respect to the direction of gravity), horizontal (e.g., perpendicular to the direction of gravity), or a direction between horizontal and vertical.

[0100] FIG. 5C illustrates aspects of a plasma heating configuration 560 for processing a contiguous reactant structure. In the illustrated example, a mixture of iron ore particles 112 and reducing agent(s) 114 (e.g., biomass particles) are formed (e.g., compacted or compressed) into a contiguous reactant structure 562 (e.g., a continuous sheet), for example, to ensure that the iron ore and reducing agent particles are well mixed before heating by the plasma 546. In some embodiments, the contiguous reactant structure 562 can be fed into the heating zone 548 with active plasma generation therein, for example, via a conveyor or other translation mechanism. In some embodiments, similar to the operation of FIG. 5B, a duration of the heating can be determined by residence time of the structure 562 within the heating zone 548, for example, based on length of the heating zone and / or generated plasma, and a speed of the reactants. Alternatively, in some embodiments, the structure 562 can be substantially stationary within heating zone 548 during the processing, for example, by placing the structure 562 within the heating zone 548 prior to plasma generation, initiating and maintaining the plasma to provide a desired duration of heating at a maximum temperature, and then ceasing the plasma and removing the product structure 564 from the heating zone 548. For example, the transition to / from the maximum temperature may be at a rate of at least 102K / s. In either case, the heating by the plasma within the heating zone 548 can be effective to directly reduce the iron ore 112 in the contiguous structure 562 to iron 116 in the product structure 564. In some embodiments, the output structure 564 may retain the same shape and contiguous nature as the reactant structure 562. Alternatively, the output structure 564 may instead be an aggregate or loose agglomeration of iron particles 116.

[0101] In the illustrated example of FIG. 5C, the orientation of the heating zone 548, the movement of reactant structure 562 into the heating zone, the positioning of reactant structure 562 within the heating zone, and the movement of product structure 564 from the heating zone is substantially horizontal. However, embodiments of the disclosed subject matter are not limited thereto. Rather, in some embodiments, the orientation of the heating zone, one or more of the movements, and / or the positioning can be vertical (e.g., aligned with respect to the direction of gravity), horizontal (e.g., perpendicular to the direction of gravity), or a direction between horizontal and vertical.

[0102] In the illustrated example of FIG. 5B, a carrier gas is used to convey the reactants through the heating zone between electrodes and the plasma therein. However, other means for conveying the reactants are also possible according to one or more contemplated embodiments. In some embodiments, in addition to or in place of the carrier gas flow, gravity can be used to convey the reactants (e.g., iron and / or reducing agent(s)) through the heating zone, for example, by orienting the thickness direction of the gap at a non-zero angle with respect to gravity. For example, FIG. 5D illustrates a gravity-feed plasma heating configuration 570 for heating a mixture of iron ore 112 and reducing agent(s) 114 to directly reduce the iron ore into iron 116. Gravity can be used to move the reactants 112, 114 into and through the heating zone 548 and the plasma 546 generated therein, and / or to remove iron products 116 from the heating zone 548. In some embodiments, a collection member 572 (e.g., crucible) can be provided at a lower end of the heating zone 548 to collect the produced iron 116. In some embodiments, similar to the operation of FIG. 5B, a duration of the heating can be determined by residence time of the reactants within the heating zone 548, for example, based on a vertical length of the heating zone and / or generated plasma, and a speed / acceleration of the reactants (e.g., induced by gravity).

[0103] In the illustrated example of FIG. 5D, the heating zone 548 extends substantially parallel to the direction of gravity; however, in some embodiments, the lateral extension of the gap between electrodes may be at an angle with respect to gravity, in addition to or in place of a carrier gas flow. For example, FIG. 5E illustrates an inclined gravity-feed plasma heating configuration 580. In the illustrated example, a mixture 582 of iron ore 112 and reducing agent(s) 114 can be provided on a static inclined support member 584, and gravity causes the mixture to move (e.g., roll and / or slide) down the support member 584 into the heating zone 598 of a reactor stage 590. In the illustrated example, the plasma 596 within heating zone 598 is generated using a fixed electrode 592 and a facing part 594 of the inclined support member 584. In some embodiments, similar to the operation of FIG. 5B, a duration of the heating can be determined by residence time of the reactants within the heating zone 598, for example, based on a length of the heating zone and / or generated plasma, and a speed / acceleration of the reactants (e.g., induced by gravity and influenced by friction and / or other surface characteristics of the inclined support member).

[0104] Joule Heating Configurations

[0105] FIG. 6A illustrates aspects of an asymmetric Joule heating configuration 600. In the illustrated example, a mixture 602 of iron ore particles 112 and reducing agent(s) 114 (e.g., biomass particles) is provided within heating zone 608 adjacent to an electrode 604. An electric current 606 can be passed through the electrode 604 (or portion thereof) to induce Joule heating therein, which Joule heating thereby heats the mixture 602 within heating zone 608. In some embodiments, the mixture 602 can be fed into the heating zone 608 prior to and / or during the Joule heating, for example, via a conveyor or other translation mechanism. In some embodiments, a duration of the heating of the mixture can be determined by residence time of the iron ore 112 and / or reducing agent(s) 114 within the heating zone 608, for example, based on length of the heating zone 608 and a speed of the reactants. Alternatively, in some embodiments, the mixture 602 can be substantially stationary within heating zone 608 while electrode 604 is Joule heated, for example, by placing the mixture 602 within the heating zone 608 prior to Joule heating, providing electric current 606 to the electrode 604 (or portion thereof) to provide a desired duration of heating at a maximum temperature, and then ceasing the electric current 606 and removing the generated iron 116 from the heating zone 608. For example, the transition to / from the maximum temperature may be at a rate of at least 102K / s. In either case, the heating within the heating zone 608 can be effective to directly reduce the iron ore 112 to iron 116.

[0106] Other means for conveying reactants through the heating zone of an asymmetric Joule heating configuration are also possible according one or more contemplated embodiments. For example, FIG. 6B illustrates an inclined gravity-feed asymmetric Joule heating configuration 610. In the illustrated example, a mixture 612 of iron ore 112 and reducing agent(s) 114 can be provided on a static inclined support member 620, and gravity causes the mixture to move (e.g., roll and / or slide) down the support member 620 into the heating zone 618. In the illustrated example, heating of the heating zone 618 is provided by passing a current 616 through electrode portion 614 of the inclined support member 620. In some embodiments, similar to the operation of FIG. 6B, a duration of the heating can be determined by residence time of the reactants within the heating zone 618, for example, based on a length of the heating zone and a kinematics of the reactants (e.g., induced by gravity and influenced by friction and / or other surface characteristics of the inclined support member).

[0107] FIG. 6C illustrates aspects of a symmetric Joule heating configuration 630. In the illustrated example, a mixture 628 of iron ore particles 112 and reducing agent(s) 114 (e.g., biomass particles) is provided within heating zone 632 formed between a pair of opposing electrodes 624a, 624b. Independent electric currents 626a, 626b can be passed through respective electrodes 624a, 624b (or portions thereof) to induce Joule heating therein, which Joule heating thereby heats the heating zone 632 and reactant mixture 628 therein. The mixture 628 can be substantially stationary within heating zone 632 while electrodes 624a, 624b are Joule heated, for example, by placing the mixture 628 within the heating zone 632 prior to Joule heating, providing electric currents 626a, 626b to electrode 624a, 624b (or portion thereof) to provide a desired duration of heating at a maximum temperature, and then ceasing the electric currents 626a, 626b and removing the generated iron 116 from the heating zone 632. For example, the transition to / from the maximum temperature may be at a rate of at least 102K / s. The heating within the heating zone 632 can be effective to directly reduce the iron ore 112 to iron 116. In some embodiments, the mixture 628 can be in direct contact with one or both of the electrodes 624a, 624b, such that heating of the mixture 628 is primarily through conduction. Alternatively, in some embodiments, the mixture 628 can be spaced from both of the electrodes 624a, 624b, such that heating of the mixture 628 is primarily through radiation.

[0108] In the illustrated example of FIG. 6C, the mixture is stationary within the heating zone during the Joule heating of the electrodes. However, the mixture can instead be conveyed through the heating zone while the electrode are Joule heated. For example, FIG. 6D illustrates aspects of a symmetric Joule heating configuration 640, where a mixture 642 of iron ore particles 112 and reducing agent(s) 114 can be conveyed through the heating zone 632 during the Joule heating, and / or the direct reduced iron 116 can be carried from the heating zone 632 by a carrier gas flow, for example, an inert gas and / or reducing gas. In some embodiments, a duration of the heating of the mixture 642 can be determined by residence time of the iron ore 112 and / or reducing agent(s) 114 within the heating zone 632, for example, based on length of the heating zone 632 and a speed of the reactants.

[0109] In the illustrated example of FIG. 6C, the orientation of the heating zone 632 and the positioning of mixture 628 within the heating zone is substantially horizontal. However, embodiments of the disclosed subject matter are not limited thereto. Rather, in some embodiments, the orientation of the heating zone, movement into and / or out of the heating zone, and / or the positioning can be vertical (e.g., aligned with respect to the direction of gravity), horizontal (e.g., perpendicular to the direction of gravity), or a direction between horizontal and vertical.

[0110] In the illustrated examples of FIG. 6C-6D, a pair of opposed electrodes is used to provide the symmetric Joule heating configuration. However, a symmetric heating configuration can also be provided by use of a single electrode, for example, by use of a tubular electrode. For example, FIG. 6E illustrates a gravity-feed symmetric Joule heating configuration 650 employing a single tubular electrode 654 for heating a mixture of iron ore 112 and reducing agent(s) 114 to directly reduce the iron ore into iron 116. In the illustrated example, the mixture of iron ore 112 and reducing agent 114 is feed through the heating zone 658 via gravity; however, in some embodiments, the mixture can be fed to and / or through the heating zone 658 via a carrier gas flow (in addition to or in place of gravity feed).

[0111] Facing inner surfaces of the electrode tube 654 bound and / or define a cylindrical heating zone 658 within the electrode tube. Current 656 can travel through the wall of the tubular electrode 654 (or portion thereof) along an axial direction, for example, by making electrical connections at opposite axial ends of the electrode tube, which current 656 can induce Joule heating of the electrode tube, which in turn heats the heating zone 658 and reactants therein. In the illustrated example, gravity can be used to move the reactants 112, 114 into and through the heating zone 658 during Joule heating, and / or to remove iron products 116 from the heating zone 658. In some embodiments, a collection member 652 (e.g., crucible) can be provided at a lower end of the heating zone 658 to collect the produced iron 116. In some embodiments, similar to the operation of FIG. 6D, a duration of the heating can be determined by residence time of the reactants within the heating zone 658, for example, based on a vertical length of the heating zone and a speed / acceleration of the reactants (e.g., induced by gravity).

[0112] Although only a single electrode tube is illustrated in FIG. 6E, multiple electrode tubes can operate in series (e.g., to provide different temperature profiles) and / or in parallel (e.g., to increase processing capacity), according to one or more contemplated embodiments. For example, FIG. 6F illustrates an example of a Joule heating system 660 employing an array of tubular electrodes 664 operating in parallel. The reactant mixture 672 can be provided to the array of tubular electrodes 664, each of which is Joule heated by a respective electric current 666 traveling axially through the wall of the respective tube 664. The reactant mixture 672 traveling within the internal heating zone 668 of the Joule-heated electrode 664 can be heated (e.g., via radiation), for example, to a temperature of at least 2000 K, so as to induce direct reduction of the iron ore in the reactant mixture 672 to iron 674. The generated iron can be removed as a product flow 674 from an output end of each tubular electrode 664. In some embodiments, the reactant mixture 672 and / or iron product 674 can be fed to, through, and / or from the respective heating zone via gravity and / or a carrier gas flow.

[0113] In the illustrated example, the tubular electrodes 664 are supported within respective receptacles 662 within a furnace body 670. In some embodiments, the furnace body 670 can include features that releasably retain the electrode tube 664 within the respective receptacle 662. In some embodiments, the furnace body 670 can include electrical connections for providing the electric currents 666 to the tubular electrodes 664. For example, the furnace body 670 can be formed of an electrically insulating (and optionally thermally insulating) material, and / or the electrodes 664 can be formed of carbonized biomass. Because the high temperature operation may degrade and / or consume the electrodes 664 over time, the furnace body 670 can be configured to allow the degraded tubular electrode 664 to be removed from its respective receptacle 662 and for a new tubular electrode 664 to be inserted into the empty receptacle 662 as a replacement.

[0114] In the illustrated examples of FIG. 6E-6F, the orientation of the heating zone (e.g., heating zone 658 or heating zone 668), the flow of reactants into the heating zone, the flow within the heating zone, and the flow of products from the heating zone is substantially vertical. However, embodiments of the disclosed subject matter are not limited thereto. Rather, in some embodiments, the orientation of the heating zone, flow into the heating zone, flow through the heating zone, and / or flow from the heating zone can be vertical (e.g., aligned with respect to the direction of gravity), horizontal (e.g., perpendicular to the direction of gravity), or a direction between horizontal and vertical.

[0115] Fabricated. Examples and. Experimental Results

[0116] EXAMPLE 1: CARBONIZED BIOMASS ELECTRODES

[0117] Solid wood was cut into test specimens with dimensions of 15 mm x 30 mm x 67 mm. The test specimens were then conditioned in an air furnace at 260 °C for 2 hours to reduce the moisture content of the wood. The wood was then carbonized in an argon-protected furnace. Each specimen was carbonized between 8-mm thick graphite weight loading pads to obtain a uniform specimen temperature and carbonized electrode. The carbonization parameters were as follows: rate of temperature rise 100 °C / h, carbonization temperature between 800 and 1100 °C, and maximum temperature maintained for 2 hours.

[0118] The resistivity of the resulting carbonized electrodes was 1-10 Q-cm. After carbonization, there is significant shrinkage of the electrodes, but the electrodes retain their integrity and flatness, which are suitable for use in plasma heating or Joule heating configurations. In particular, FIG. 7A shows a proof-of-concept setup using the carbonized wood electrodes for plasma processing. The ignited plasma between the carbonized electrodes is shown in FIG. 7B. The plasma temperature was determined using Rayleigh thermometry - a linear technique in which the Rayleigh scattering signal is proportional to the total number density of the molecules in the plasma and inversely proportional to the temperature. As shown in FIG. 7C, as the increased current from 15 A to 45 A (corresponding to a current density of 3 A / cm2to 9 A / cm2), the plasma temperature increased from -4200 K to -7700 K. In some cases, electrodes of different sizes from those tested may result in different plasma temperatures for the same current input.

[0119] EXAMPLE 2: PLASMA HEATING

[0120] FIG. 8A shows an experimental setup for iron ore reduction via plasma heating. In this example, mixed iron oxide and carbon particles were filled in a carbon crucible 802, which is placed between two carbonized electrodes. The carbonized electrodes were energized to generate a plasma that heated the mixture within the crucible, thereby generating melting iron 804, as shown in FIG. 8B. Upon cooling, the directly reduced iron was removed from the crucible, as shown in FIG. 8C. These balls comprise metallic iron (non-oxide iron), as confirmed by the magnetic test of FIG. 8D. In particular, the iron ball 806 is highly magnetic and is readily attracted to vertically-mounted magnet 808. Moreover, the iron ball exhibit a metallic color, while the original iron oxide powder is red and non-magnetic, thus providing further confirmation of the effective reduction of iron ore to iron.

[0121] EXAMPLE 3: JOULE HEATING

[0122] In this example, ultrahigh temperature synthesis sintering is used for production of iron. Iron ore was mixed with partially delignified sawdust via 4 hours of ball-milling. The resulting mixture was then placed between and in direct contact with a pair of carbon-based electrodes (e.g., carbon felt). Using a programmable power supply, the temperature of the electrodes was quickly increased to initiate the reduction reaction between iron ore and sawdust, thereby producing pure iron between the electrodes. FIGS. 9A-9B show the microstructures of the partially delignified sawdust and iron ore, respectively, prior to the reduction reaction via Joule heating. FIG. 9C shows the microstructure of the pure iron product resulting from the reduction reaction. No fiber structure was observed in the micro structure of the iron product, thereby confirming complete decomposition of the sawdust as the reducing agent. The product is in the form of black powder and can be attracted by a NdFeB magnet, as shown in FIG. 9D. Moreover, X-ray diffraction confirms that the reduced product is pure a-Fe BCC phase (JCPDS: 06-0696), as shown in FIG. 9E.

[0123] The partially delignified sawdust serves as a source of carbon and hydrogen in the iron ore reduction reaction and thus acts as a reducing agent. The reaction is influenced by the mass ratio between the sawdust and iron ore as well as the reaction temperature. For example, at relatively high reducing temperatures and shorter reaction times (1500-1800 K, 10s), no pure a- Fe was detected. Increasing the amount of partially delignified sawdust would be expected to increase a-Fe product, as shown in FIG. 10A. However, even though the amount of FeO decreased (as indicated by the relative intensity of the peak ratio in the dashed frame), it was always detected with the presence of y-Fe. In contrast, at relatively lower reducing temperatures and longer reaction times (800-1300 K, 60s), pure a-Fe was obtained with increasing the amount of sawdust, as shown in FIG. 10B. It is noted that the Joule heating configurations employed in the experiments underlying FIGS. 10A-10B were symmetric heating configurations with direct contact between the reactants and the electrodes (e.g., primarily conduction heating). However, it is expected that Joule heating configurations that have reactants spaced from the electrodes (e.g., employing radiation heating) will require higher temperatures (e.g., > 2000 K) and / or different durations to generate a pure a-Fe product.

[0124] Additional Examples of the Disclosed Technology

[0125] In view of the above-described implementations of the disclosed subject matter, this application discloses the additional examples in the clauses enumerated below. It should be noted that one feature of a clause in isolation, or more than one feature of the clause taken in combination, and, optionally, in combination with one or more features of one or more further clauses are further examples also falling within the disclosure of this application.

[0126] Clause 1. A method comprising: generating a heating zone adjacent to one or more electrode portions by applying one or more electric currents to the one or more electrode portions, a temperature within the heating zone being at least 800 K; and providing a mixture of iron ore and one or more reducing agents within the heating zone for a first time period, such that the iron ore is directly reduced to iron.

[0127] Clause 2. The method of any clause or example herein, in particular, Clause 1, wherein the one or more reducing agents comprises biomass.

[0128] Clause 3. The method of any clause or example herein, in particular, Clause 2, wherein the biomass comprises or is derived from plant material.

[0129] Clause 4. The method of any clause or example herein, in particular, any one of Clauses 2- 3, wherein the biomass comprises sawdust.

[0130] Clause 5. The method of any clause or example herein, in particular, Clause 4, wherein the sawdust is at least partially delignified.

[0131] Clause 6. The method of any clause or example herein, in particular, any one of Clauses 1- 5, wherein the mixture is formed by mixing together the iron ore and at least one of the one or more reducing agents prior to the heating zone.

[0132] Clause 7. The method of any clause or example herein, in particular, any one of Clauses 1-

[0133] 5, wherein the mixture is formed by disposing the iron ore and at least one of the one or more reducing agents together in the heating zone.

[0134] Clause 8. The method of any clause or example herein, in particular, any one of Clauses 1-

[0135] 6, wherein the mixture is formed by grinding together the iron ore and at least one of the one or more reducing agents. Clause 9. The method of any clause or example herein, in particular, any one of Clauses 1- 8, wherein the one or more electrode portions comprise carbonized biomass.

[0136] Clause 10. The method of any clause or example herein, in particular, Clause 9, wherein the biomass comprises or is derived from plant material.

[0137] Clause 11. The method of any clause or example herein, in particular, any one of Clauses 9-

[0138] 10, wherein: (i) the carbonized biomass is formed from a solid piece of wood or bamboo, or (ii) the carbonized biomass is formed from compacted particles of wood, bamboo, and / or other plant materials.

[0139] Clause 12. The method of any clause or example herein, in particular, any one of Clauses 9-

[0140] 11, further comprising, prior to the generating the heating zone, carbonizing the biomass to form the one or more electrode portions.

[0141] Clause 13. The method of any clause or example herein, in particular, any one of Clauses 1-

[0142] 12, further comprising, prior to the generating, roughening one or more surfaces of the one or more electrode portions.

[0143] Clause 14. The method of any clause or example herein, in particular, any one of Clauses 1-

[0144] 13, wherein the providing comprises flowing the iron ore and at least one of the one or more reducing agents through the heating zone, and the first time period is set at least in part based on the flowing.

[0145] Clause 15. The method of any clause or example herein, in particular, Clause 14, wherein the flowing is at least partly driven by gravity.

[0146] Clause 16. The method of any clause or example herein, in particular, any one of Clauses 1- 15, wherein: the one or more electrode portions are a pair of facing portions of opposing electrodes, and the heating zone is formed between the pair of facing portions.

[0147] Clause 17. The method of any clause or example herein, in particular, Clause 16, wherein the one or more applied electric currents flow between the opposing electrodes so as to provide a thermal plasma within the heating zone.

[0148] Clause 18. The method of any clause or example herein, in particular, any one of Clauses 1- 17, wherein an atmosphere within the heating zone comprises an inert gas, nitrogen, a reduction gas, or any combination of the foregoing.

[0149] Clause 19. The method of any clause or example herein, in particular, any one of Clauses 16-18, wherein: during the generating, at least part of the facing portions are consumed by the plasma, and the method further comprises, during or after the first time period, moving one or both of the opposing electrodes toward the other so as to at least partly compensate for the consumed part.

[0150] Clause 20. The method of any clause or example herein, in particular, any one of Clauses

[0151] 16-19, wherein: the facing portions of the opposing electrodes comprise or are formed of carbon, and at least one of the one or more reducing agents comprises carbon released from the facing portions by the plasma during the generating.

[0152] Clause 21. The method of any clause or example herein, in particular, any one of Clauses

[0153] 17-20, wherein: a temperature of the plasma within the heating zone is less than or equal to 10,000 K; a voltage applied between the opposing electrodes is less than or equal to 100 V; each of the one or more electric currents applied to the opposing electrodes is less than or equal to 50 A; a current density applied to the opposing electrodes is less than or equal to 10 A / cm2; or any combination of the above.

[0154] Clause 22. The method of any clause or example herein, in particular, any one of Clauses 17-21, wherein: a temperature of the plasma within the heating zone is 3000-8000 K, inclusive; a voltage applied between the opposing electrodes is 10-80 V, inclusive; each of the one or more electric currents applied to the opposing electrodes is 15-45 A, inclusive; a current density applied to opposing electrodes is 3-9 A / cm2, inclusive; or any combination of the above.

[0155] Clause 23. The method of any clause or example herein, in particular, any one of Clauses 17-22, wherein a duration of the first time period is less than or equal to 5 minutes.

[0156] Clause 24. The method of any clause or example herein, in particular, any one of Clauses 1- 16, wherein: the one or more applied electric currents are a pair of electric currents, each being applied to a respective one of the opposing electrodes such that the electric current flows through and causes Joule heating of the respective electrode without passing through the heating zone.

[0157] Clause 25. The method of any clause or example herein, in particular, any one of Clauses 1- 15, wherein: the one or more electrode portions are facing portions of a first electrode, the heating zone is formed between the facing portions of the first electrode, and the one or more applied electric currents is a single electric current applied to the first electrode such that the single electric current flows through and causes Joule heating of the first electrode without passing through the heating zone.

[0158] Clause 26. The method of any clause or example herein, in particular, Clause 25, wherein: the first electrode has a shape of a tube, the facing portions are opposing inner wall portions of the tube, the heating zone is formed within an interior of the tube, and the single electric current flows along a length of the tube.

[0159] Clause 27. The method of any clause or example herein, in particular, any one of Clauses 1- 15, wherein: the one or more electrode portions is a single surface portion of a first electrode, the heating zone is formed adjacent to the single surface portion, and the one or more applied electric currents is a single electric current applied to the first electrode such that the single electric current flows through and causes Joule heating of the first electrode without passing through the heating zone.

[0160] Clause 28. The method of any clause or example herein, in particular, any one of Clauses 24-27, wherein: during the generating, the mixture is in direct contact with at least one of the one or more electrode portions, a temperature of the one or more electrode portions is 800-1300 K, inclusive, and a duration of the first period is 30-90 seconds, inclusive.

[0161] Clause 29. The method of any clause or example herein, in particular, any one of Clauses 24-27, wherein: during the generating, the mixture is spaced from each of the one or more electrode portions, a temperature of the one or more electrode portions is greater than or equal to 2000 K, and a duration of the first period is at least 10 seconds.

[0162] Clause 30. The method of any clause or example herein, in particular, Clause 29, wherein the duration of the first period is at least 60 seconds.

[0163] Clause 31. The method of any clause or example herein, in particular, any one of Clauses 24-30, wherein: (i) a voltage applied to each electrode is less than or equal to 100 V, (ii) each electric current is less than or equal to 100 A, or both of the foregoing.

[0164] Clause 32. The method of any clause or example herein, in particular, any one of Clauses 24-31, wherein: (i) a voltage applied to each electrode is 5-50 V, inclusive, (ii) each electric current is 5-50 A, inclusive, or both of the foregoing.

[0165] Clause 33. The method of any clause or example herein, in particular, any one of Clauses 1- 36, wherein an atmosphere within the heating zone comprises syngas and / or carbon dioxide. Clause 34. The method of any clause or example herein, in particular, any one of Clauses 24-33, wherein each electrode comprises or is formed of carbonized biomass.

[0166] Clause 35. The method of any clause or example herein, in particular, any one of Clauses 1-

[0167] 34, wherein the temperature within the heating zone varies during at least part of the first time period.

[0168] Clause 36. The method of any clause or example herein, in particular, any one of Clauses 1-

[0169] 35, wherein a particle size of the iron ore, the one or more reducing agents, or both is less than or equal to 1 mm.

[0170] Clause 37. The method of any clause or example herein, in particular, any one of Clauses 1-

[0171] 36, wherein at least one of the one or more reducing agents comprises syngas formed by in situ gasification of biomass provided to the heating zone during the first time period.

[0172] Clause 38. The method of any clause or example herein, in particular, any one of Clauses 1-

[0173] 37, further comprising, after the providing: replacing the one or more electrode portions with a new set of one or more electrode portions; repeating the generating with the new set of one or more electrode portions; and providing another mixture of iron ore and one or more reducing agents within the heating zone produced by the repeating, such that the iron ore of the another mixture is directly reduced to iron.

[0174] Clause 39. The method of any clause or example herein, in particular, any one of Clauses 1-

[0175] 38, further comprising alloying the iron to form steel.

[0176] Clause 40. A system for performing the method of any clause or example herein, in particular, any one of Clauses 1-39.

[0177] Clause 41. A system for reducing iron ore to iron, the system comprising: one or more reactors, each reactor comprising one or more electrode portions; a power supply electrically connected to the one or more electrode portions; and a controller operatively coupled to the power supply, the controller comprising one or more processors and one or more non-transitory computer-readable storage media, wherein the one or more electrode portions are constructed to generate a heating zone adjacent to the one or more electrode portions when one or more electric currents are applied to the one or more electrode portions, the computer-readable storage media store computer-readable instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents to the one or more electrode portions such that a temperature within the heating zone is at least 800 K, and the one or more reactors are configured such that, when a mixture of iron ore and one or more reducing agents is within the generated heating zone for a first time period, the iron ore in the mixture is directly reduced to iron.

[0178] Clause 42. The system of any clause or example herein, in particular, any one of Clauses 40-

[0179] 41, wherein the one or more reactors is a plurality of reactors operating in parallel, each reactor being configured to generated its own heating zone.

[0180] Clause 43. The system of any clause or example herein, in particular, any one of Clauses 40-

[0181] 42, wherein one, some, or each of the one or more electrode portions comprises carbonized biomass.

[0182] Clause 44. The system of any clause or example herein, in particular, Clause 43, wherein the biomass comprises or is derived from plant material.

[0183] Clause 45. The system of any clause or example herein, in particular, any one of Clauses 43-

[0184] 44, wherein the carbonized biomass is formed from a solid piece of wood or bamboo, or the carbonized biomass is formed from compacted particles of wood, bamboo, and / or other plant materials.

[0185] Clause 46. The system of any clause or example herein, in particular, any one of Clauses 40-

[0186] 45, wherein, for each reactor, the heating zone generated by the one or more electrode portions is arranged such that the iron ore is moved through the heating zone by gravity.

[0187] Clause 47. The system of any clause or example herein, in particular, any one of Clauses 40- 45, wherein, for each reactor, the one or more electrode portions are a pair of facing portions of opposing electrodes, and the heating zone is formed between the pair of facing portions.

[0188] Clause 48. The system of any clause or example herein, in particular, Clause 47, wherein, for each reactor, the one or more electrode portions are configured such that the one or more applied electric currents flow between the opposing electrodes so as to provide a thermal plasma within the heating zone.

[0189] Clause 49. The system of any clause or example herein, in particular, any one of Clauses 40- 48, further comprising a gas source coupled to the one or more reactors and configured to supply an inert gas, nitrogen, a reduction gas, or any combination of the foregoing to the respective heating zone.

[0190] Clause 50. The system of any clause or example herein, in particular, any one of Clauses 40-

[0191] 49, wherein, for each reactor, the one or more electrode portions are configured to be at least partly consumed by the plasma.

[0192] Clause 51. The system of any clause or example herein, in particular, any one of Clauses 47-

[0193] 50, wherein each reactor further comprises one or more translation devices configured to move one or both of the opposing electrodes toward the other.

[0194] Clause 52. The system of any clause or example herein, in particular, Clause 51, wherein the controller is operatively coupled to the one or more translations devices, and the computer- readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to move, via the one or more translation devices, one or both of the opposing electrodes toward the other so as to at least partly compensate from the consumed part.

[0195] Clause 53. The system of any clause or example herein, in particular, any one of Clauses 48-

[0196] 52, wherein, for each reactor: the facing portions of the opposing electrodes comprise or are formed of carbon, and the facing portions are configured to release carbon during the plasma, the released carbon acting as at least one of the one or more reducing agents.

[0197] Clause 54. The system of any clause or example herein, in particular, any one of Clauses 48-

[0198] 53, wherein the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents such that: a temperature of the plasma within the heating zone is less than or equal to 10,000 K; a voltage applied between the opposing electrodes is less than or equal to 100 V; each of the one or more electric currents applied to the opposing electrodes is less than or equal to 50 A; a current density applied to the opposing electrodes is less than or equal to 10 A / cm2; or any combination of the above.

[0199] Clause 55. The system of any clause or example herein, in particular, any one of Clauses 48-

[0200] 54, wherein the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents such that: a temperature of the plasma within the heating zone is 3000-8000 K, inclusive; a voltage applied between the opposing electrodes is 10-80 V, inclusive; each of the one or more electric currents applied to the opposing electrodes is 15-45 A, inclusive; a current density applied to the opposing electrodes is 3-9 A / cm2, inclusive; or any combination of the above.

[0201] Clause 56. The system of any clause or example herein, in particular, any one of Clauses 48- 55, wherein a duration of the first time period is less than or equal to 5 minutes.

[0202] Clause 57. The system of any clause or example herein, in particular, Clause 47, wherein, for each reactor, the one or more electrode portions are configured such that the one or more electric currents are a pair of electric currents, each being applied to a respective one of the opposing electrodes, and the electric current flows through and causes Joule heating of the respective electrode without passing through the heating zone.

[0203] Clause 58. The system of any clause or example herein, in particular, any one of Clauses 40- 46, wherein, for each reactor: the one or more electrode portions are facing portions of a first electrode; the heating zone is formed between the facing portions of the first electrode; and the first electrode is configured such that the one or more applied electric currents is a single electric current applied to the first electrode, the single electric current flowing through and causing Joule heating of the first electrode without passing through the heating zone.

[0204] Clause 59. The system of any clause or example herein, in particular, Clause 58, wherein the first electrode has a shape of a tube, the facing portions are opposing inner wall portions of the tube, the heating zone is formed within an interior of the tube, and the single electric current flows along a length of the tube.

[0205] Clause 60. The system of any clause or example herein, in particular, Clause 59, wherein a diameter of each tube is less than or equal to 5.1 cm or in a range of 2.5-5.1 cm, inclusive.

[0206] Clause 61. The system of any clause or example herein, in particular, any one of Clauses 40- 46, wherein, for each reactor: the one or more electrode portions is a single surface portion of a first electrode; the heating zone is formed adjacent to the single surface portion; and the first electrode is configured such that the one or more applied electric currents is a single electric current applied to the first electrode, the single electric current flowing through and causing Joule heating of the first electrode without passing through the heating zone.

[0207] Clause 62. The system of any clause or example herein, in particular, any one of Clauses 57- 61, wherein: the reactor is configured such that the mixture is in direct contact with at least one of the one or more electrode portions within the generated heating zone; and the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents such that a temperature of the one or more electrode portions is 800-1300 K, inclusive, and a duration of the first period is 30-90 seconds, inclusive.

[0208] Clause 63. The system of any clause or example herein, in particular, any one of Clauses 57- 61, wherein: the reactor is configured such that the mixture is spaced from each of the one or more electrode portions within the generated heating zone; and the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents such that a temperature of the one or more electrode portions is greater than or equal to 2000 K and a duration of the first period is at least 10 seconds.

[0209] Clause 64. The system of any clause or example herein, in particular, Clause 63, wherein the duration of the first period is at least 60 seconds.

[0210] Clause 65. The system of any clause or example herein, in particular, any one of Clauses 57-

[0211] 64, wherein the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents such that a voltage applied to each electrode is less than or equal to 100 V and / or each electric current is less than or equal to 100 A.

[0212] Clause 66. The system of any clause or example herein, in particular, any one of Clauses 57-

[0213] 65, wherein the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents such that a voltage applied to each electrode is 5- 50 V, inclusive, and / or each electric current is 5-50 A, inclusive. Clause 67. The system of any clause or example herein, in particular, any one of Clauses 40-

[0214] 66, wherein each electrode comprises or is formed of carbonized biomass.

[0215] Clause 68. The system of any clause or example herein, in particular, any one of Clauses 40-

[0216] 67, further comprising a furnace body in which the one or more reactors are disposed, the one or more reactors being constructed for removal from and replacement within the furnace body.

[0217] Clause 69. The system of any clause or example herein, in particular, any one of Clauses 40-

[0218] 68, wherein the power supply is configured to provide each electric current as AC or DC current.

[0219] Conclusion

[0220] Any of the features illustrated or described herein, for example, with respect to FIGS. 1A-10B and Clauses 1-69, can be combined with any other feature illustrated or described herein, for example, with respect to FIGS. 1A-10B and Clauses 1-69, to provide materials, systems, devices, structures, methods, aspects, or embodiments not otherwise illustrated or specifically described herein. All features described herein are independent of one another and, except where structurally impossible, can be used in combination with any other feature described herein. In view of the many possible aspects to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated features are only examples and should not be taken as limiting the scope of the disclosed technology. Rather, the scope is defined by the following claims. We therefore claim all that comes within the scope and spirit of these claims.

Claims

CLAIMS1. A method comprising: generating a heating zone adjacent to one or more electrode portions by applying one or more electric currents to the one or more electrode portions, a temperature within the heating zone being at least 800 K; and providing a mixture of iron ore and one or more reducing agents within the heating zone for a first time period, such that the iron ore is directly reduced to iron.

2. The method of claim 1, wherein the one or more reducing agents comprises biomass.

3. The method of claim 2, wherein the biomass comprises or is derived from plant material.

4. The method of claim 2, wherein the biomass comprises sawdust.

5. The method of claim 4, wherein the sawdust is at least partially delignified.

6. The method of claim 1, wherein the mixture is formed by mixing together the iron ore and at least one of the one or more reducing agents prior to the heating zone.

7. The method of claim 1, wherein the mixture is formed by disposing the iron ore and at least one of the one or more reducing agents together in the heating zone.

8. The method of claim 1, wherein the mixture is formed by grinding together the iron ore and at least one of the one or more reducing agents.

9. The method of claim 1, wherein the one or more electrode portions comprise carbonized biomass.

10. The method of claim 9, wherein the biomass comprises or is derived from plant material.

11. The method of claim 9, wherein: the carbonized biomass is formed from a solid piece of wood or bamboo; or the carbonized biomass is formed from compacted particles of wood, bamboo, and / or other plant materials.

12. The method of claim 9, further comprising, prior to the generating the heating zone, carbonizing the biomass to form the one or more electrode portions.

13. The method of claim 12, further comprising, prior to the generating, roughening one or more surfaces of the one or more electrode portions.

14. The method of claim 1, wherein the providing comprises flowing the iron ore and at least one of the one or more reducing agents through the heating zone, wherein the first time period is set at least in part based on the flowing.

15. The method of claim 14, wherein the flowing is at least partly driven by gravity.

16. The method of claim 1, wherein the one or more electrode portions are a pair of facing portions of opposing electrodes, and the heating zone is formed between the pair of facing portions.

17. The method of claim 16, wherein the one or more applied electric currents flow between the opposing electrodes so as to provide a thermal plasma within the heating zone.

18. The method of claim 17, wherein an atmosphere within the heating zone comprises an inert gas, nitrogen, a reduction gas, or any combination of the foregoing.

19. The method of claim 17, wherein: during the generating, at least part of the facing portions are consumed by the plasma; and the method further comprises, during or after the first time period, moving one or both of the opposing electrodes toward the other so as to at least partly compensate for the consumed part.

20. The method of claim 17, wherein: the facing portions of the opposing electrodes comprise or are formed of carbon; and at least one of the one or more reducing agents comprises carbon released from the facing portions by the plasma during the generating.

21. The method of claim 17, wherein: a temperature of the plasma within the heating zone is less than or equal to 10,000 K; a voltage applied between the opposing electrodes is less than or equal to 100 V; each of the one or more electric currents applied to the opposing electrodes is less than or equal to 50 A; a current density applied to the opposing electrodes is less than or equal to 10 A / cm2; or any combination of the above.

22. The method of claim 17, wherein: a temperature of the plasma within the heating zone is 3000-8000 K, inclusive; a voltage applied between the opposing electrodes is 10-80 V, inclusive; each of the one or more electric currents applied to the opposing electrodes is 15-45 A, inclusive; a current density applied to opposing electrodes is 3-9 A / cm2, inclusive; or any combination of the above.

23. The method of claim 17, wherein a duration of the first time period is less than or equal to 5 minutes.

24. The method of claim 16, wherein the one or more applied electric currents are a pair of electric currents, each being applied to a respective one of the opposing electrodes such that the electric current flows through and causes Joule heating of the respective electrode without passing through the heating zone.

25. The method of claim 1, wherein: the one or more electrode portions are facing portions of a first electrode; the heating zone is formed between the facing portions of the first electrode; andthe one or more applied electric currents is a single electric current applied to the first electrode such that the single electric current flows through and causes Joule heating of the first electrode without passing through the heating zone.

26. The method of claim 25, wherein the first electrode has a shape of a tube, the facing portions are opposing inner wall portions of the tube, the heating zone is formed within an interior of the tube, and the single electric current flows along a length of the tube.

27. The method of claim 1, wherein: the one or more electrode portions is a single surface portion of a first electrode; the heating zone is formed adjacent to the single surface portion; and the one or more applied electric currents is a single electric current applied to the first electrode such that the single electric current flows through and causes Joule heating of the first electrode without passing through the heating zone.

28. The method of any one of claims 24-27, wherein: during the generating, the mixture is in direct contact with at least one of the one or more electrode portions; a temperature of the one or more electrode portions is 800-1300 K, inclusive; and a duration of the first period is 30-90 seconds, inclusive.

29. The method of any one of claims 24-27, wherein: during the generating, the mixture is spaced from each of the one or more electrode portions; a temperature of the one or more electrode portions is greater than or equal to 2000 K; and a duration of the first period is at least 10 seconds.

30. The method of claim 29, wherein the duration of the first period is at least 60 seconds.

31. The method of any one of claims 24-27, wherein: a voltage applied to each electrode is less than or equal to 100 V; each electric current is less than or equal to 100 A; or both of the above.

32. The method of any one of claims 24-27, wherein: a voltage applied to each electrode is 5-50 V, inclusive; each electric current is 5-50 A, inclusive; or both of the above.

33. The method of any one of claims 24-27, wherein an atmosphere within the heating zone comprises syngas and / or carbon dioxide.

34. The method of any one of claims 24-27, wherein each electrode comprises or is formed of carbonized biomass.

35. The method of claim 1, wherein the temperature within the heating zone varies during at least part of the first time period.

36. The method of claim 1, wherein a particle size of the iron ore, the one or more reducing agents, or both is less than or equal to 1 mm.

37. The method of claim 1, wherein at least one of the one or more reducing agents comprises syngas formed by in situ gasification of biomass provided to the heating zone during the first time period.

38. The method of claim 1, further comprising, after the providing: replacing the one or more electrode portions with a new set of one or more electrode portions; repeating the generating with the new set of one or more electrode portions; and providing another mixture of iron ore and one or more reducing agents within the heating zone produced by the repeating, such that the iron ore of the another mixture is directly reduced to iron.

39. The method of claim 1, further comprising alloying the iron to form steel.

40. A system for performing the method of any one of claims 1-39.

41. A system for reducing iron ore to iron, the system comprising: one or more reactors, each reactor comprising one or more electrode portions; a power supply electrically connected to the one or more electrode portions; and a controller operatively coupled to the power supply, the controller comprising one or more processors and one or more non-transitory computer-readable storage media, wherein the one or more electrode portions are constructed to generate a heating zone adjacent to the one or more electrode portions when one or more electric currents are applied to the one or more electrode portions, the computer-readable storage media store computer-readable instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents to the one or more electrode portions such that a temperature within the heating zone is at least 800 K, and the one or more reactors are configured such that, when a mixture of iron ore and one or more reducing agents is within the generated heating zone for a first time period, the iron ore in the mixture is directly reduced to iron.

42. The system of claim 41, wherein the one or more reactors is a plurality of reactors operating in parallel, each reactor being configured to generated its own heating zone.

43. The system of claim 41, wherein one, some, or each of the one or more electrode portions comprises carbonized biomass.

44. The system of claim 43, wherein the biomass comprises or is derived from plant material.

45. The system of claim 43, wherein: the carbonized biomass is formed from a solid piece of wood or bamboo; or the carbonized biomass is formed from compacted particles of wood, bamboo, and / or other plant materials.

46. The system of claim 41, wherein, for each reactor, the heating zone generated by the one or more electrode portions is arranged such that the iron ore is moved through the heating zone by gravity.

47. The system of claim 41, wherein, for each reactor, the one or more electrode portions are a pair of facing portions of opposing electrodes, and the heating zone is formed between the pair of facing portions.

48. The system of claim 47, wherein, for each reactor, the one or more electrode portions are configured such that the one or more applied electric currents flow between the opposing electrodes so as to provide a thermal plasma within the heating zone.

49. The system of claim 48, further comprising a gas source coupled to the one or more reactors and configured to supply an inert gas, nitrogen, a reduction gas, or any combination of the foregoing to the respective heating zone.

50. The system of claim 48, wherein, for each reactor, the one or more electrode portions are configured to be at least partly consumed by the plasma.

51. The system of any one of claims 48-50, wherein each reactor further comprises one or more translation devices configured to move one or both of the opposing electrodes toward the other.

52. The system of claim 51, wherein the controller is operatively coupled to the one or more translations devices, and the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to move, via the one or more translation devices, one or both of the opposing electrodes toward the other so as to at least partly compensate from the consumed part.

53. The system of claim 48, wherein, for each reactor: the facing portions of the opposing electrodes comprise or are formed of carbon; and the facing portions are configured to release carbon during the plasma, the released carbon acting as at least one of the one or more reducing agents.

54. The system of claim 48, wherein the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents such that: a temperature of the plasma within the heating zone is less than or equal to 10,000 K;a voltage applied between the opposing electrodes is less than or equal to 100 V; each of the one or more electric currents applied to the opposing electrodes is less than or equal to 50 A; a current density applied to the opposing electrodes is less than or equal to 10 A / cm2; or any combination of the above.

55. The system of claim 48, wherein the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents such that: a temperature of the plasma within the heating zone is 3000-8000 K, inclusive; a voltage applied between the opposing electrodes is 10-80 V, inclusive; each of the one or more electric currents applied to the opposing electrodes is 15-45 A, inclusive; a current density applied to the opposing electrodes is 3-9 A / cm2, inclusive; or any combination of the above.

56. The system of claim 48, wherein a duration of the first time period is less than or equal to 5 minutes.

57. The system of claim 47, wherein, for each reactor, the one or more electrode portions are configured such that the one or more electric currents are a pair of electric currents, each being applied to a respective one of the opposing electrodes, and the electric current flows through and causes Joule heating of the respective electrode without passing through the heating zone.

58. The system of claim 41, wherein, for each reactor: the one or more electrode portions are facing portions of a first electrode; the heating zone is formed between the facing portions of the first electrode; and the first electrode is configured such that the one or more applied electric currents is a single electric current applied to the first electrode, the single electric current flowing through and causing Joule heating of the first electrode without passing through the heating zone.

59. The system of claim 58, wherein the first electrode has a shape of a tube, the facing portions are opposing inner wall portions of the tube, the heating zone is formed within an interior of the tube, and the single electric current flows along a length of the tube.

60. The system of claim 59, wherein a diameter of each tube is less than or equal to 5.1 cm or in a range of 2.5-5.1 cm, inclusive.

61. The system of claim 41, wherein, for each reactor: the one or more electrode portions is a single surface portion of a first electrode; the heating zone is formed adjacent to the single surface portion; and the first electrode is configured such that the one or more applied electric currents is a single electric current applied to the first electrode, the single electric current flowing through and causing Joule heating of the first electrode without passing through the heating zone.

62. The system of any one of claims 57-61, wherein: the reactor is configured such that the mixture is in direct contact with at least one of the one or more electrode portions within the generated heating zone; and the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents such that a temperature of the one or more electrode portions is 800-1300 K, inclusive, and a duration of the first period is 30-90 seconds, inclusive.

63. The system of any one of claims 57-61, wherein: the reactor is configured such that the mixture is spaced from each of the one or more electrode portions within the generated heating zone; and the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents such that a temperature of the one or more electrode portions is greater than or equal to 2000 K and a duration of the first period is at least 10 seconds.

64. The system of claim 63, wherein the duration of the first period is at least 60 seconds.

65. The system of any one of claims 57-61, wherein the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents such that a voltage applied to each electrode is less than or equal to 100 V and / or each electric current is less than or equal to 100 A.

66. The system of any one of claims 57-61, wherein the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the one or more processors to apply, via the power supply, the one or more electric currents such that a voltage applied to each electrode is 5-50 V, inclusive, and / or each electric current is 5-50 A, inclusive.

67. The system of any one of claims 57-61, wherein each electrode comprises or is formed of carbonized biomass.

68. The system of claim 41, further comprising a furnace body in which the one or more reactors are disposed, the one or more reactors being constructed for removal from and replacement within the furnace body.

69. The system of claim 41, wherein the power supply is configured to provide each electric current as AC or DC current.

Images