Abstract
A method and system for carrying out non-thermal plasma direct reduction of ore ultrafines into resource material are described. In particular, the present invention is directed to a method for direct reduction of ultrafines using an integrated system including an ultrafines source and a non-thermal plasma source. The method includes delivering ultrafines to a reduction reaction zone; and applying, within the reduction reaction zone, a non-thermal plasma to the ultrafines.
Claims
1. A method for direct reduction of ultrafines using an integrated system including an ultrafines source and a non-thermal plasma source, the method comprising: delivering ultrafines to a reduction reaction zone; and applying, within the reduction reaction zone, a non-thermal plasma to the ultrafines.
2. The method of claim 1, further comprising: performing a cyclonic or fluidized separation operation on an feedstock to obtain the ultrafines.
3. The method of claim 2, wherein the cyclonic or fluidized separation operation is carried out by a series of separator chambers providing successively smaller particles to a next chamber of the series.
4. The method of claim 3, wherein a portion of the ultrafines subjected to the non-thermal plasma are converted to a resource material.
5. The method of claim 1, wherein the ultrafines feedstock is an ore comprising resource material particles and gangue particles wherein the resource material particles are beneficiated after passage through the reduction reaction zone for separation from gangue particles.
6. The method of claim 1, wherein the resource material is directed into a subsequent additive manufacturing process.
7. The method of claim 1, wherein the resource material is derived from a mined ore.
8. The method of claim 7, wherein the mined ore is one or more mined ore taken from the group consisting of: iron, rare earths and critical minerals.
9. The method of claim 1, wherein the resource material is derived from a processed metal.
10. The method of claim 9, wherein the processed metal is one or more processed metal taken from the group consisting of: aluminum, niobium, and hafnium.
11. An integrated system for performing direct reduction of ultrafines, the system comprising: an ultrafines source; and a non-thermal plasma source, wherein the integrated system is configured to carry out performing direct reduction of ultrafines by: delivering ultrafines to a reduction reaction zone; and applying, within the reduction reaction zone, a non-thermal plasma to the ultrafines.
12. The system of claim 11, wherein the direct reduction of ultrafines is carried out by: performing a cyclonic or fluidized separation operation on an feedstock to obtain the ultrafines.
13. The system of claim 12, wherein the cyclonic or fluidized separation operation is carried out by a series of separator chambers providing successively smaller particles to a next chamber of the series.
14. The system of claim 11, wherein a portion of the ultrafines subjected to the non-thermal plasma are converted to a resource material.
15. The system of claim 11, wherein a resource material is beneficiated from gangue material by combination of non-thermal plasma and cyclonic or fluidized separation based on mass and density change to the ultrafines particles during performing the direct reduction.
16. The system of claim 11, wherein the resource material is directed into a subsequent additive manufacturing process.
17. The system of claim 11, wherein the resource material is derived from a mined ore.
18. The system of claim 7, wherein the mined ore is one or more mined ore taken from the group consisting of: iron, rare earths and critical minerals.
19. The system of claim 11, wherein the resource material is derived from a processed metal.
20. The system of claim 9, wherein the processed metal is one or more processed metal taken from the group consisting of: aluminum, niobium, and hafnium.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] While the appended claims set forth the aspects of the present invention with particularity, the invention and its advantages are best understood from the following detailed description taken in conjunction with the accompanying drawings, of which:
[0009] FIG. 1 is a schematic diagram illustratively depicting an exemplary system for processing iron ore ultrafines using cold plasma jets to perform non-thermal direct reduction of the ultrafines in accordance with the disclosure;
[0010] FIG. 2 is a schematic block diagram including additional functional units added in additional subsystems for the process with a particle feed system, gas injection, separators, a filtration unit and process flow for multiple stages in accordance with the disclosure;
[0011] FIGS. 3-5 are schematic depictions of known systems/methods showing fluidized bed processing
[0012] FIG. 6 graphically depicts an exemplary particle size distribution for iron ore ultrafines ground down to <250 m in accordance with the disclosure;
[0013] FIGS. 7A and 7B illustratively depict a cyclonic separator in accordance with the disclosure;
[0014] FIG. 8 depicts prior art showing/summarizing particle separation efficiency based on centrifugal force and pressure gradients formed in a cyclone vortex separator;
[0015] FIGS. 9A, 9B and 9C illustratively depict cascaded cyclonic separator units arranged to progressively separate and sort ultrafines by particle size in accordance with the disclosure;
[0016] FIG. 10A known stages of fluidization of ultrafines;
[0017] FIG. 10B shows known fluidization of ultrafines in known riser reactors;
[0018] FIG. 10C shows a prior art circulating fluidized bed with solid extraction arrangement;
[0019] FIG. 11 illustratively depicts a generic coaxial microwave cold plasma generator with gas flow down the center in accordance with the disclosure;
[0020] FIG. 12 illustratively depicts a coaxial cable attachment configured to launch the electromagnetic wave into the plasma applicator in a compact form factor in accordance with the disclosure;
[0021] FIGS. 13A and 13B illustratively depict examples application arrangements of a coaxial cold plasma jet in accordance with the disclosure;
[0022] FIGS. 14A and 14B illustratively depict an example of how multiple microwave cold plasma jet sources may be used on (positioned within) a flow channel, flow riser or conveyance to subject particles to the plasma environment in accordance with the disclosure;
[0023] FIGS. 15A, 15B and 15C illustratively depicts exemplary integrations of a cold plasma source with a cyclone separator in accordance with the disclosure;
[0024] FIGS. 16A, 16B and 16C illustratively depict a different approach where no gas is injected through the cold plasma jet applicator in accordance with the disclosure;
[0025] FIG. 17 illustratively depicts an example of clustering multiple in-line plasma jet sources with different particle feeds to obtain plasma chemistry effects and create a larger plasma effect zone in accordance with the disclosure;
[0026] FIG. 18 summarizes and illustratively depicts the plasma-material interactions and surface chemistry reactions during non-thermal plasma direct reduction of iron ore ultrafines in accordance with the disclosure;
[0027] FIG. 19 illustratively depicts successive reactions going from magnetite to hematite to wustite and hydroxide and ultimately to pure iron in accordance with the disclosure;
[0028] FIGS. 20A, 20B, 20C and 20D illustratively depict how the ultrafine particle will be immersed in plasma and acquire surface charge as well as depict a generic particle of material subject to the non-thermal plasma environment for the reduction and removal of surface oxide and intra-grain oxide in accordance with the disclosure;
[0029] FIG. 21 illustratively depicts the surface rate kinetics and plasma chemistry in accordance with the current disclosure;
[0030] FIG. 22 illustratively depicts the concept for two equivalent particles that were separated in the fluidized bed or cyclone separator;
[0031] FIG. 23 provides a generic depiction of a fluidized bed with a microwave plasma jet source integrated with, assisting with, or located aside the fluidization in accordance with the disclosure;
[0032] FIG. 24 further expands on FIG. 23 by showing a fluidized bed with exit ports for lighter or reduced material (top exit) versus the heavier or gangue material (bottom exit) in accordance with the disclosure;
[0033] FIG. 25 further expands on the fluidization bed approach with changing particle density and fluidization parameters for pneumatic lifting or separation in accordance with the disclosure;
[0034] FIG. 26 illustratively depicts another fluidized riser with integrated microwave plasma unit treating particles in accordance with the disclosure;
[0035] FIG. 27 is a schematic depiction of a complete system including the fluidized bed arrangement depicted in FIG. 26 in accordance with the disclosure;
[0036] FIGS. 28A and 28B illustratively depict Gibbs free energy for H2 to react with FeOx and a depiction of the Gibbs free energy for atomic hydrogen reaction at room temperature through several hundred C in accordance with the disclosure;
[0037] FIGS. 29A and 29B illustratively depict another system processing embodiment employing a vibrating table or cascading table in accordance with the disclosure;
[0038] FIG. 30 illustratively depicts a known rotary kiln for processing;
[0039] FIGS. 31 and 32 illustratively depict embodiments where one or more microwave cold plasma applicators is inserted into the rotary kiln for application of non-thermal plasma onto the iron ore in accordance with the disclosure;
[0040] FIGS. 33A, 33B, 33C and 33D provide detail on a distributed coaxial microwave source fashioned as a surface wave launcher;
[0041] FIGS. 34A, 34B, and 34C illustratively depict the plasma region axially and in cross-section;
[0042] FIG. 35 illustratively depicts a radial waveguide version of the microwave plasma applicator for a rotary kiln in accordance with the disclosure;
[0043] FIGS. 36A and 36B are microwave sources for cold plasma jets similar to FIG. 16B, and are integrated with a rotary kiln with sliding metal contacts for electromagnetic hermiticity.
[0044] FIGS. 37A and 37B illustratively depict electric field and electromagnetic energy can radiate into an internal region using a slotted waveguide approach in accordance with the disclosure;
[0045] FIG. 38 illustratively depicts a generic reactor model showing process inputs and process outputs for CO2 cracking, methane pyrolysis, ammonia production or NO production, iron reduction, rare earth mineral reduction, and other mineral oxide reduction, including powder materials used in additive manufacturing in accordance with the disclosure;
[0046] FIG. 39 illustratively depicts a particular application of the current disclosure wherein a feedstock stream is non-thermal direct reduced by a cold plasma jet on a path from a nozzle to a target additive part in an additive manufacturing arrangement in accordance with the disclosure; and
[0047] FIG. 40 illustratively depicts another particular application of the current disclosure wherein a feedstock stream is non-thermal direct reduced by a cold plasma jet on a path from a nozzle to a sputtering target in an additive manufacturing arrangement in accordance with the disclosure.
DETAILED DESCRIPTION OF THE DRAWINGS
[0048] Using hydrogen plasma directly in a fluidized bed has the potential to: (1) provide a direct means to introduce highly-reactive hydrogen (i.e. monoatomic (H.Math.), ionic (H+) and vibrationally-excited H.sub.2(v) species), (2) provide a means of sprouting through pulsed gas injection, (3) enable highly-reactive hydrogen mixing of the ore with high area solid-gas contact, and (4) utilize plasma waste energy as process heat for energy efficiency.
[0049] The system and method disclosed herein has a potential for carrying out a fluidized cold plasma reduction process that may be performed on mine output to produce high-quality iron Fe for direct shipment to EAF and BOFs around the world. The system and method facilitate carrying out reduction on lower quality ores, while reducing energy inputs, removing carbon from the process, and switching to H.sub.2 or NH.sub.3 renewable feedstocks.
[0050] Furthermore, the system and method disclosed herein may be generalized for plasma reduction or oxidation of other fluidized particles for chemical reaction, separation or beneficiation. For example, the system and method described herein may be used for the hydrogen-plasma reduction of other ultrafines of ores, including rare-earth oxides and other critical minerals used in industry, e.g. neodymium, praseodymium, dysprosium, etc.
[0051] Moreover, the system and method described herein may be used for reduction and oxygen removal from ultrafine and fine powders used for 3D additive manufacturing, e.g., laser sintering and e-beam melting, production of composite materials and specialty physical vapor deposition targets, e.g., specialty sputtering targets, and refining of feedstocks for magnet production applications.
[0052] Examples include preparation of niobium and hafnium refractory alloys for powder bed fusion, or reduction of native oxides on aluminum powders for laser sintering. Non-thermal plasma interactions at the surface and H radical recombination can remove oxygen leading to purer material for additive manufacturing leading to improved properties compared with bulk properties. This is evident in preparation of powder materials for hot isostatic pressing into composite material blocks for target materials used in physical vapor deposition systems-such as sputtering targets for Starfire Industries IMPULSE HiPIMS systems. Such sputtering targets are often created with unique elemental mixtures comprising various ultrafine powders pressed into a block. With ultrafine particle sizes that are often in the 1-50 micron range, the surface area-to-volume ratio can be high, leading to native surface oxide contamination.
[0053] In yet another example, the aforementioned RADION system is used to reduce surface oxides and remove oxygen contamination by directly treating particles in-flight and then directing the treated particles to a subsequent production process.
[0054] The disclosed system and method use electricity to generate cold plasmas to generate vibrationally-excited hydrogen, radicals and ions at low temperatures. The described PURE-Fe approach is not hydrogen plasma smelting (H.sub.2-assisted molten oxide electrolysis) or arc-like treatment (gliding arc or focused RF/MW) where gas temperatures exceeding >2000 C. vaporize everything. The described method/approach instead minimizes energy inputs by creating cold plasmas that are non-thermal, i.e. high energy electrons that can excite and break bonds but low heat energy for atoms. With this process, solid phase is maintained for the ultra-fine iron ore for fluid transport and minimal agglomeration.
[0055] The system and method include a low-temperature, direct-reduction process for ultra-fine iron ore that combines operation of a fluidized bed cyclone with a solid-state microwave-powered non-thermal hydrogen plasma jet to eliminate metallurgical coke and replace blast furnace production with a carbon-free alterative reductant-namely hydrogen plasma.
[0056] The disclosed system and method may be used to take in ore material feedstock, comprising a mixture of a valuable resource (e.g. iron, neodymium, etc.) and gangue particle (e.g. silica, feldspar, etc.), convert the feedstock into ultrafines for fluidization, and perform reduction and beneficiation for resource material recovery.
[0057] The system and method incorporate the following features/objectives: [0058] 1. Carrying out a reduction process using non-thermal (cold) plasma treatment with low energy. [0059] 2. Utilizing plasma-enhanced fluidized bed and/or cyclonic separators for ultrafine transport, reduction, beneficiation and gangue removal. [0060] 3. Providing an iron ore reduction process that is scalable to industrial use
[0061] The disclosed system and method have the potential to: [0062] achieve a zero carbon process; [0063] eliminate steps in iron making, i.e. pelletizing, shipping Fe.sub.2O.sub.3, heat energy; [0064] require less energy per kg processed; [0065] integrate beneficiation & reduction in one process; [0066] increase diversity of usable iron ore feedstock, including low-grade ores; [0067] recover most iron in feedstock and reducing tailings; [0068] facilitate automatic separation of gangue for recovery at point of iron reduction; [0069] reduce the size and resources needed to build and operate an iron ore reduction facility; and [0070] integrate directly with EAF and BOF steel mills
[0071] Turning to FIG. 1, a solid-state microwave-powered non-thermal (cold) plasma jet may be used to carry out direct hydrogen reduction of iron ore pellets for the steel industry. For example, a hydrogen reactor vessel incorporating such non-thermal plasma jet is used to perform non-thermal plasma reduction of sintered iron oxide pucks/discs achieving 100 m reductionalong regions where plasma penetrates grain boundaries and diffuses by channeling reductionin over a few minutes exposure at 50 W power injection. The AG for atomic hydrogen on iron oxides (FeO, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4) is highly negative due to aggressive free radical attack-compared with traditional DRI H.sub.2 processes where process temperatures exceeding 1200 C. are required. Use of active hydrogen radical species enables low temperature processing with Fe-conversion (<400 C.) eliminating wstite formation and its sticky agglomerating effects.
[0072] A solid-state microwave-powered non-thermal (cold) plasma jet is well-suited for carrying out direct reduction using a fluidized bed reactor approach. The system exhibits the following characteristics: on-axis zonal gas flow, microwave delivery at the point of injection, high electrical energy coupling efficiency and control over the electron-energy distribution function to optimize plasma properties, and an ability to pneumatically transport a charge out of the zone. The non-thermal electron energy distribution facilitates efficient plasma chemistry at much lower temperatures for net energy savings. The process, by way of example, is carried out by use of small-diameter ultrafine fluidized transport through a localized microwave cold plasma for direct reduction.
[0073] By way of a specific production process, a reduction process is carried out on 20 m nominal diameter ultrafines to provide high-grade iron. Currently, iron ore is ground down into ultrafines to better separate gangue from iron ore to improve extraction. However, large quantities of iron are not recovered due to limitations in magnetic separation or floatation beneficiation. For each ton of iron ore recovered, between 5-6 tons of tailings with a considerable amount of iron is left unrecovered.
[0074] The size distribution of targeted ultrafines are suitable for fluidization and gas-phase transport for injection into a non-thermal (cold) hydrogen plasma region. The system and associated process described herein has the potential to form Fe briquettes at a mine (vs. Fe.sub.2O.sub.3 taconite pellets) for shipment to electric arc furnaces or incorporated directly into an Electric Arc Furnace or Basic Oxygen Furnace for on demand production.
[0075] In accordance with the present disclosure and more particularly an exemplary system depicted in FIG. 1, plasma jet applicators are integrated with a fluidized bed/transport system for ultrafines and performs cold plasma-based non-thermal direct reduction on, for example, iron ore ultrafines. A 20 m particle size of ultrafines falls on the Geldart classification table edge for the transition between aeratable and cohesive particles. Since the initial particles will be insulating, in the iron oxide example, operating with the electrons and ions of the microwave plasma will produce a stronger net negative electrical charge on the particles providing them with greater repulsion and agglomeration inhibition. As particles are reduced and become more metallic there may be a reversion. In the presence of a plasma, the surface charging rates and kinetics are dependent on particle flux and secondary electron emission dynamics and will affect all particles, oxide, native oxide or purely metallic.
[0076] A solid-state microwave plasma produces atomic hydrogen at near room temperature through vibrational excitation and energy-efficiency dissociation with minimal gas heatingsuppressing nature to collapse into a filamentary, arc plasma (hot).
[0077] Keeping the plasma region non-thermal (cold) facilitates more efficient use of electrical energy for the direct reduction of iron ore ultrafines.
[0078] Plasma generation may be integrated with induced flow to charge up ultrafines (electron attachment) to mitigate agglomeration while undergoing gas-phase reduction with hydrogen radicals and ions present.
[0079] Since the hydrogen radical reduction process is exothermic on the ultrafines, there is inherent localized heating on the ultra-fine iron ore that enhances diffusion and rapidly increases the rate of the reduction process.
[0080] Instead of heating everything up (e.g. gangue), the disclosed system and method selectively heat the iron ore using radical and ion bombardment to enhance surface reactions and drive the kinetics. Thus, the non-thermal (cold) plasma provides a low-energy DRI alternative with hydrogen radicals vs. H.sub.2 heating everything up to >1200 C. and limited to Saha surface rate kinetics, whisker growth and particle sticking.
[0081] If gas temperature is controlled (<1400 C.) with pulsed microwaves to adjust the electron energy distribution function, ultrafines will not melt or evaporate during the reduction process. This is an important features so as not to compromise the reactor, cause vaporization of the ultrafines and plating of the iron onto the reactor walls, or cause melting, agglomeration and sticking to gangue present in the reactor-which will undue the mechanical separation producing the ultrafines in the first placei.e. re-melting SiO.sub.2 or Al.sub.2O.sub.3 into Fe.
[0082] Maintaining a solid phase during direct reduction is important. During the direct reduction, the cold hydrogen plasma reduction removes oxygen resulting in a significant mass/density change to individual particles of the ultrafines, which allows for efficient vortex creation and/or fluidized bed separation.
[0083] The cyclonic separator may be a single unit with at least 1 plasma jet tangentially injecting ultrafines with gas admixture through a plasma zone to charge, reduce and expose material as it enters or traverses the cyclone. An efficient direct reduction system may be created with multiple tangential plasma jet units for power/throughput introducing material and plasma zones to allow multiple passes for the material to reduce, change density and migrate into the central vortex extraction region. Gangue is not effected and will precipitate out the bottom for collection and resale.
[0084] Cascading cyclonic separators may be used for further refinement and reduction, including an initial separation. Cascading plasma reactors will enable continuous refinement and enrichment with high efficiency.
[0085] A fluidized bed concept can similarly be used where particle size and density change can lead to separation; for example, achieving pneumatic separation in a vertical column fluidized bed reactor once reduction has occurred and the bed separates into two factions. Cascading fluidized beds, tables, etc. can sort and separate materials as well.
[0086] The envisioned direct reduction plasma reactor can reduce, in addition to magnetite (Fe.sub.3O.sub.4, 72.4% Fc), hematite (Fe.sub.2O.sub.3, 69.9% Fe), goethite (FeO(OH), 62.9% Fe), limonite (FeO(OH).Math.n(H.sub.2O), 55% Fe) and siderite (FeCO.sub.3, 48.2% Fe), etc. Mixed elements, such as ankerite (Ca(Mg,Fe)(CO.sub.3).sub.2), will reduce as well. The material type-agnostic cold plasma process enables a diversity of iron ore feedstocks from various geographic locations.
[0087] The product of the disclosed direct reduction system and method is metallic iron particles that are collected, pressed into briquettes, electrically sintered, etc. If the quality of the direct reduction process output is high enough, from complete reduction and separation, then there is potential for direct steel making, e.g feed into an EAF or BOF.
[0088] A conceptual diagram is highlighted, in FIG. 1, showing an integrated plasma and cyclone vortex in-situ separation of gangue from reducible iron ore. The system may be cascaded with M particle sizes and N recovery stages to optimize for iron extraction vs. energy cost.
[0089] The disclosed direct reduction approach overcomes limitations of thermal plasma reactors (high-power microwave, RF and gliding DC arc) where gas-phase temperatures can exceed the melting or vaporization point (>>2000 C.). For those extreme temperature systems, incoming ore particles flash evaporate and gas-phase recombine into nanoparticles with the gangue.
[0090] The disclosed direct reduction approach lowers the input energy cost compared to traditional and hydrogen Direct Reduced Iron (DRI) and HYFOR processes.
[0091] In accordance with the illustrative example of FIG. 1 comprising a plurality of cascading plasma jet-enhanced cyclonic separator units, an input to any given separator unit of the system coaxially feeds particles into a reactor vessel, performs the reduction, creates a mass/density change, and allows for real-time separation. As a result, the cyclonic vortex concept is well-suited for a fluidized approach for down selection.
[0092] The exemplary system includes a fluidized benchtop reactor, an ultrafines particle hopper (for reference diameter materials and iron ore ultrafines with mixed size distribution), a fore pumping and an exhaust pumping system, particle traps with filter media, and a microwave cold plasma jet source. The fluidized transport system can separate a small diameter particle group from a large diameter group.
[0093] The process may be carried out on a small reactor design and/or multiplexed for enhanced throughput. Thus, the disclosed system and method provide a new iron-ore direct reduction system and method that utilize activated hydrogen in fluidized beds/cyclonic separators.
[0094] With continued reference to FIG. 1, a system level schematic drawing depicts a system 100 for processing iron ore ultrafines including three distinct separator stages, with each separator stage including a top cyclonic separator unit (e.g., top separator unit 101) and a bottom cyclonic separator unit (e.g., bottom separator unit 103). The top cyclonic separator unit separates unreduced input ultrafines according to size such that particles smaller than a configured size generally rise in the separator and pass through an upper passage (e.g. upper output passage 102), and particles larger than a configured size generally fall in the separator vessel and pass through a plasma jet treatment passage 105 including one or more cold plasma jets installed therein for performing reduction on the ultrafines passing through the passage 105. Plasma-treated output from the passage 105 enters the bottom separator unit 103 wherein reduced iron ultrafines (generally lighter than unprocessed (gangue) material) rise and pass through an upper passage 106 for collection in a reduced iron ultrafines hopper 110. Relatively heavier (gangue) material generally fall from a lower opening in the bottom separator unit 103 to a gangue collection hopper 109. The first separator stage is configured to treat largest size ultrafines, while each subsequent stage treats/produces a progressively smaller ultrafine particle.
[0095] As can be observed from FIG. 1, the first stage treats (via plasma jets in a passage between top and bottom separator units within any given separator stage) input ultrafines of at least 35 microns, the second stage treats ultrafines of at least 25 micro particles, and the third stage treats ultrafines of at least 20 microns.
[0096] Thus, in the illustrative example of FIG. 1, small diameter iron ore particles (ultrafines) are fed into a cascading set of fluid cyclone separators to separate the provided iron ore particles into different sizes and densities. The drop-through ultrafines output from each of top separator units are fed into a non-thermal plasma zone, within a passage between the top and bottom separator units of a given separator stage, to carry out a hydrogen plasma direct reduction of the ultrafines passing through the non-thermal plasma zone. The non-thermal plasma puts charge on the surface of the individual particles, thereby providing a force to separate particles and minimize agglomeration. When iron oxide particles are reduced with hydrogen plasma generated from the input gases (e.g. H2, H2O NH3, CH4, etc.), the particles lose mass from the removal of oxide. This changes the density of the particles and their fluid flow properties enabling efficient extraction of the reduced ultrafines from non-reduced ultrafines using the bottom separator unit. Additionally, non-iron material, such as alumino silicates will remain relatively unaffected by the plasma jets and will separate out. This allows both beneficiation of multiple iron ore types, e.g. hematite, magnetite, goetite, etc., and the direct reduction of iron for sorting. The direct reduced iron (e.g. sponge iron) will be small particles that may be subsequently processed to render the reduced iron in the form of pressed briquettes, rods, balls, etc. Thermal energy is recycled and reused for enhanced energy efficiency.
[0097] Turning to FIG. 2, a block diagram is provided with additional functional units added in additional subsystems for the process with a particle feed system, gas injection, separators, a filtration unit and process flow for multiple stages. Here a magnetic separation stage 202 applies a magnetic field to the gangue falling from a lower (reduced/non-reduced ultrafines) cyclonic separator 201 to catch reduced iron that did not exit the upper passage of the separator units. Additionally, weak B fields may be applied to assist with particle separation in the vortex or fluidized beds.
[0098] FIGS. 3-5, depict known systems/methods showing fluidized bed processing at >650 C or >800 C for H2 reduction for HYFOR (i.e., FIG. 3). For FINMET (i.e., FIG. 4), reduction of iron ore is carried out using cascading high pressure (12 bar) direct reduction with the process occurring at a high temperature. Circored (i.e., FIG. 5) uses fluidized beds at higher pressure with thermal recovery. In contrast, the direct reduction process carried out using plasma jets applied to particular sized ultrafines doe not require the relatively high pressures and/or high temperatures of the known systems depicted in FIGS. 3-5.
[0099] Turning to FIG. 6, a graph depicts an exemplary particle size distribution for iron ore ultrafines ground down to <200 m to better separate gangue from iron ore. The ultrafines have very large surface area to volume ratiomaking them desirable for non-thermal plasma processing.
[0100] FIGS. 7A and 7B illustratively depict a typical cyclone separator used to separate relatively larger particles (falling to the bottom) from relatively small particles (rising to the top) or to separate solids from gases. Internal dimensions of the cyclone separator are designed to achieve a specific separation for a range of input flow, particle sizes, etc. This is well known in the literature.
[0101] FIG. 8 depicts prior art showing/summarizing particle separation efficiency based on centrifugal force and pressure gradients formed in a cyclone vortex separator. Since such devices are not 100% perfect, there will be some escape and particle mixing. This may be overcome, as shown in FIG. 1 described herein above, with cascading units to multiple extraction or refinement efficiencies.
[0102] FIG. 9A illustratively depicts inputting material and progressively separating and sorting ultrafines by particle size.
[0103] FIG. 9B illustratively depicts, with more detail, the cascading separation units/process summarized in FIG. 9A, by showing that particles may be progressively sorted into groups with a nominal density/size profile.
[0104] FIG. 9C illustratively depicts detail on a next cascade for size refinement efficiency. The cascaded separators operate to separate out sizes with a narrow size/density class so that when cold-plasma reduction occurs and there is a mass density size change, the reduced/non-reduced ultrafines will be separable from one another. Gases such as argon may be used and recycled to maintain a consistent air flow.
[0105] FIG. 10A shows known stages of fluidization of ultrafines-going from bubbling to slugging to turbulent to fast and to pneumatic conveyance. By changing the gas flow properties a given charge of particles may be reacted and then transported away.
[0106] FIG. 10B shows fluidization of ultrafines in a different manner and known riser reactors or fast fluidized bed reactors may be used and then coupled with a cyclone separator for extraction of reduced iron. This is done today, by known systems, at high temperatures and high pressure for the direct reduction of iron.
[0107] FIG. 10C shows prior art circulating fluidized bed with solid extraction arrangement.
[0108] FIG. 11 illustratively depicts a generic coaxial microwave cold plasma generator with gas flow down the center. Microwaves fed in coaxially into a region of cutoff where a high E field is formed to breakdown the plasma into a conductor, and the microwaves drive the plasma jet for performing cold plasma jet generation.
[0109] FIG. 12 illustratively depicts a coaxial cable attachment configured to launch the electromagnetic wave into the plasma applicator in a compact form factor. Note that a gas flow can also be injected into the coaxial space in addition to the centerline.
[0110] FIG. 13A illustratively depicts a first illustrative example application of a coaxial plasma applicator mounted onto a side of a plasma reactor with ultrafine material particles passing by the cold plasma jet. Gas is injected, plasma is formed, and a non-thermal plasma plume interacts with ultra-fine iron ore particles causing plasma chemistry reactions and the reduction of iron (alternatively/additionally processing of other materials). The disclosed direct reduction system and method are not limited to processing ultra-fine iron ore. Other minerals may be reduced, enriched, and transformed into useable form with the plasma source.
[0111] FIG. 13B illustratively depicts another illustrative example where ultrafine iron ore particles or other materials, e.g. rare earth oxides, powders with native oxides, etc, to be processed are injected through a centerline directly through the plasma zone. This is an efficient process since all of the material will pass the plasma region and be subjected to the plasma radicals, ions, electrons, etc. Insertable liners may be used to minimize abrasion. Gas flow may be directly integrated with the flow from an output cyclone or have reactant gas added to the main flow stream.
[0112] For the additive manufacturing embodiment, particles in-flight in FIG. 13B headed for 3D printing (e.g. laser sintering, e-beam melting, isostatic pressing, etc.) pass through the active plasma and radical zone for oxide reduction and surface activation. An example is preparation of niobium and hafnium refractory alloys for powder bed fusion, or the reduction of native oxides on aluminum powders for laser sintering. Non-thermal plasma interactions at the surface and hydrogen radical recombination may be used to remove oxygen leading to purer material for additive manufacturing leading to improved properties compared with bulk properties. This is evident in the preparation of powder materials for hot isostatic pressing into composite material blocks for target materials used in physical vapor deposition systems-such as sputtering targets for Starfire Industries IMPULSE HiPIMS systems. Such sputtering targets are often created with unique elemental mixtures comprising various ultrafine powders pressed into a monoblock. With ultrafine particle sizes that are often in the 1-50 micron range, the surface area-to-volume ratio may be high, leading to native surface oxide contamination. Using the cold plasma jet system to reduce surface oxides and remove oxygen contamination is thus another potential application and/or embodiment for directly treating particles in-flight and then directing the resulting reduced ultrafines to a subsequent production process utilizing the reduced ultrafines.
[0113] FIGS. 14A and 14B illustratively depict an example of how multiple microwave cold plasma jet sources may be used on (positioned within) a flow channel, flow riser or conveyance to subject particles to the plasma environment. Such a process may be coupled with a separator to extract material post reduction and mass change. The design of such a system could use the gas flow injection local for the reactant gas (e.g. H2, NH3, H2O, while the main conveyance gas, e.g. Ar, is unaffected.
[0114] FIG. 15A illustratively depicts an exemplary integration of a plasma source directly at a point of injection into the cyclone separator. In this scenario, the particles are injected onto their trajectories and the plasma effluent will charge up, separate dust and particles and provide a recirculating volume for reactions.
[0115] FIG. 15B illustratively depicts another illustrative example wherein multiple solid-state plasma jet sources are mounted onto a larger cyclone separator for radial tangential injection, and FIG. 15C illustratively depicts multiple levels of injection being used in a single cyclonic separator for increased throughput.
[0116] FIG. 16A illustratively depicts a different approach where no gas is injected through the plasma applicator. Instead, each individual applicator, of a set of applicators, is mounted directly on a wall of a plasma reactor and gas flow inside the reactor creates plasma when microwaves are applied. This is useful for putting MANY small microwave applicators around a larger reactor vessel. A benefit for this approach is that multiple discrete units can create microwave plasma discharges with low effective Townsend coefficients or reduced electron distribution functions.
[0117] The coaxial plasma applicators may be small diameter (e.g., less than 1 inch) to generate broad area plasma regions that are not too hot. The disclosed system and method allows multiple discrete smaller units that can independently control plasma formation, emission and local EEDF for optimal plasma parameters for chemistry, reduction and processing of materials.
[0118] One challenge with >10 KW microwave magnetrons is that power injection is very strong with intense electric fields leading to thermal plasma generation. FIG. 16B illustratively depicts an embodiment where the periphery of a space within the reactor is a continuous waveguide with multiple injection slots for plasma generation. This overcomes the issue of excessive heat generated when using a single high power source; and this process may be used with solid state as well.
[0119] FIG. 16C depicts a similar configuration to FIG. 16A but with small waveguide injection along the periphery of a cyclonic separator reactor chamber. This allows compact cyclone sizes.
[0120] FIG. 17 is an example of clustering multiple in-line plasma jet sources with different particle feeds to obtain plasma chemistry effects and create a larger plasma effect zone. Using multiple discrete units resists the formation of a thermal plasma arc.
[0121] FIG. 18 summarizes and illustratively depicts the plasma-material interactions and surface chemistry reactions during non-thermal plasma direct reduction of iron ore ultrafines. In this example, hydrogen gas is excited by the plasma electrons from the microwaves and dissociated into H and H*, as well as forming H.sub.2.sup.+ ions. This may be accomplished by direct electron impact dissociation or vibrationally excited dissociationthe latter taking less total energy to accomplish but requiring a stepwise excitation until overcoming the potential barrier to separate. H species and H.sub.2.sup.+ will land on the surface and attack a surface oxide bond. This is an exothermic reaction and it will release energy that will heat the surface of the ultrafine particle. As successive H species interact with the surface, water will be formed that will evaporate off leaving the reduced material behind. The surface heating from the exothermic reactions will serve to drive oxygen diffusion and removal of water so that the surfaces are open and ready for successful reductions. O diffusion to the surface, creation of porous voids, tunnels and sponge-like network allows H to penetrate along grain boundaries and to transport products.
[0122] A primary use of the above-described systems and direct reduction processes is ore reduction and beneficiation for iron, rare earth oxides, critical minerals, etc. However, a secondary group of applications include surface preparation processes for powders used in 3D printing. For example, the chemical reactions/processes illustratively depicted in FIG. 18 may be generalized for removing native oxides from powders used in additive manufacturing, such as aluminum, niobium and hafnium. Non-thermal plasma interactions at the surface and H radical recombination will remove oxygen leading to purer material for additive manufacturing.
[0123] FIG. 19 illustratively depicts successive reactions going from magnetite to hematite to wustite and hydroxide and ultimately to pure iron. Note that a hydrogen radical H has a very high negative Gibbs free energy so the reaction will take place with earnest. If the reaction products are transported to the surface and the material does not exceed the melting point, the a highly porous sponge iron ultrafine particle will remain. This is very beneficial since the mass of the particle will have decreased with the loss of oxide. Fe2O3.fwdarw.Fe will be a relative mass change of (58*2+16*3=116+48=164 vs. 116nearly a .sup.rd reduction in mass. With the sponge iron particle size remaining the same, the effective density drops 33% and this is what enables mass separation in the cyclone or fluidized bed reactor concepts.
[0124] FIGS. 20A, 20B, 20C and 20D illustratively depict how the ultrafine particle will be immersed in plasma and acquire surface charge. This charge will repel one particle from another and maintain a suspension. This aspect of non-thermal ultrafines direct reduction is helpful to minimize agglomeration. The sequence of FIGS. 20A, 20B, 20C and 20D also shows a generic particle of material, such as aluminum or niobium or neodymium powder, subject to the non-thermal plasma environment for the reduction and removal of surface oxide and intra-grain oxide.
[0125] FIG. 21 further expands on the surface rate kinetics and plasma chemistry described herein above. Because H radicals will exothermically react with surface oxides and release energy, the ultrafine particles will heat up. If the surface heating increases such that conventional H2 reduction reactions are possible, then it is possible to have enhanced reduction from local thermal effects in addition to the non-thermal direct reduction. Under certain conditions with very high H2 ambient pressure, this process could run away leading to melting and vaporization of the ultrafine particle. Therefore adjustment of Ar to H2 flow can minimize or enhance this effect. Note this is not limited to H2, it can also apply to other chemistries and process conditions beyond iron ore.
[0126] Importantly H radicals selectively heat (via exothermic reactions) only the reducible iron oxides vs. other gangue or non-iron materials present in the ultrafines. Meaning that an Fe2O3 particle will reduce and gain thermal energy quickly, whereas a Al2O3 particle will proceed slowly. This means that energy input into the system is selectively targeting the reducible iron only. This improved the overall energy efficiency for the system and allows room temperature iron ore reduction.
[0127] FIG. 22 further expands on the concept for two equivalent particles that were separated in the fluidized bed or cyclone separator. During reduction, the reducible iron particle will lower its density and increase porosity vs. the gangue particles present. The reducible iron ultrafine particle will have a density change and the gangue particle will not. The gangue particle will have some surface heating from H recombination into H2 on the surface whereas the reducible iron oxide ultrafine particle will have OH H2O formation with a much higher reaction rate since the surface density is higher.
[0128] This creates an interesting aspect of the innovation where the separated resource material particles can have significantly higher temperature than the separable gangue particles. This allows superior energy efficiency by efficiently heating the resource material particles vs. other gangue. Controlling the power input by the non-thermal plasma source power onto the ultrafine resource material particles with the exothermic recombination can allow the resource material particle to melt for subsequent agglomeration into a larger-size briquette or sphere with improved surface area to volume ratio.
[0129] FIG. 23 provides a generic depiction of a fluidized bed concept with a microwave plasma jet source integrated with, assisting with or located aside the fluidization. The collection a single cold plasma jet unit or a multiplexed group of many plasma jet units can provide effective plasma zone interaction with the ultrafine particles.
[0130] FIG. 24 further expands on FIG. 23 by showing a fluidized bed with exit ports for lighter or reduced material (top exit) versus the heavier or gangue material (bottom exit) that could be operated in a batch mode or continuous.
[0131] FIG. 25 further expands on the fluidization bed approach with changing particle density and fluidization parameters for pneumatic lifting or separation. A charge of ultra-fine particles of suitable size distribution is loaded into the bed reactor and plasma applied for reducing reactions. Gas flow will impact the fluidization and separation of certain reduced resource material particles vs. gangue and a simple valve or redirector can differentiate between either by mass. It is possible to create a continuous system where heavy material sorts into a first bin/chute and the lighter material into a second bin/chute.
[0132] Furthermore, the separated resource material particles may be agglomerated into a larger-size briquette or sphere with improved surface area to volume ratio. The hopper or catcher may be insulated and heated to accomplish this.
[0133] FIG. 26 illustratively depicts another fluidized riser with integrated microwave plasma unit treating particles. Controlling the flow can pneumatically transport the ultrafine materials into a diverter for reduced material vs. gangue based on the particle density reduction exhibited by a reduced iron particle.
[0134] FIG. 27 is a complete system including the fluidized bed arrangement depicted in FIG. 26 in an system arrangement similar to FIG. 2 with ultrafine particle injection, separation and injection into fluidized bed non-thermal plasma reactors with separation, gas-particle separation, magnetic separation and secondary recovery, gas extraction and de-water/de-dusting, and fluid transport.
[0135] FIGS. 28A and 28B are diagrams illustratively depicting Gibbs free energy for H2 to react with FeOx and a depiction of the Gibbs free energy for atomic hydrogen reaction at room temperature through several hundred C.
[0136] FIG. 29A illustratively depicts another system processing embodiment employing a vibrating table or cascading table. In such arrangement, a reactor vessel is large and has an elevated inlet with a physical vibration table, or multiple gas injection ports (like an air hockey table), that causes ultrafines to hop, tumble and bounce along the table from one end to the other. Several non-thermal plasma units may be located inside the reactor to provide directed cold plasma jets onto the ultrafine particles.
[0137] FIG. 29B uses the plasma jet units as part of the table to provide flow to assist with the conveyance of the ultrafines from the inlet to the exit.
[0138] FIG. 30 illustratively depicts a known rotary kiln for processing. Here a large ceramic cylinder is elevated at one end, rotated and provides the means for iron ore ultrafines to tumble, roll over, migrate and exit on the other end of the kiln. For the conventional DRI process, the kiln is used with a thermal blanket, insulation and heating to achieve >800 C or high pressure.
[0139] FIG. 31 illustratively depicts an embodiment where one or more microwave cold plasma applicators is inserted into the rotary kiln for application of non-thermal plasma onto the iron ore present.
[0140] FIG. 32 illustratively depicts an alternate version of the rotary kiln of FIG. 31, wherein the plasma source is a long distributed source providing multiple plasma zones for radical, ion and electron generation.
[0141] The plasma applicator may be constructed out of metal and ceramic in a hermetically sealed fashion for high temperature operation inside the kiln.
[0142] FIG. 33A provides detail on such a distributed coaxial microwave source fashioned as a surface wave launcher. Microwave energy is input into one end and energy radiates out of one or more slots to create and sustain plasma.
[0143] FIG. 33B is a traveling wave version with fixturing at both ends.
[0144] FIG. 33C illustratively depicts the static version with a solid center conductor and slotted outer conductor with dielectric medium.
[0145] FIG. 33D illustratively depicts a hollow center conductor with gas flow through a porous dielectric or along a gapped channel in the coaxial transmission line to allow for gas ejection to enhance local plasma chemistry or directed flow.
[0146] FIG. 34A illustratively depicts the plasma region axially, and FIG. 34B illustratively depicts the plasma region in cross section. FIG. 34C illustratively depicts the plasma jet formation with local gas ejection from the plasma applicator. This is especially good for using Ar as the main gas conveyance for iron ore ultrafines and only selective application of H2, NH3 or other material at the plasma point of interest. This minimizes reactant gas use.
[0147] FIG. 35 illustratively depicts a radial waveguide version of the microwave plasma applicator for a rotary kiln. Here the center rotary part can rotate with gaps for slotted waveguide emission into the rotary kiln with plasma zones identified by the location of the slots. FIGS. 36A and 36B are similar to FIG. 16B except it is integrated with the rotary kiln with sliding metal contacts for electromagnetic hermiticity.
[0148] FIGS. 37A and 37B show how electric field and electromagnetic energy can radiate into an internal region using a slotted waveguide approach.
[0149] FIG. 38 illustratively depicts a generic reactor model showing the process inputs and process outputs for CO2 cracking, methane pyrolysis, ammonia production or NO production, iron reduction, rare earth mineral reduction, and other mineral oxide reduction, including powder materials used in additive manufacturing.
[0150] FIG. 39 illustratively depicts a particular application of the current disclosure wherein a feedstock stream 3910 is non-thermal direct reduced by a cold plasma jet 3902 on a path from a nozzle 3901 to a target additive part 3991 in an additive manufacturing arrangement where the reduced feedstock stream 3910 is subsequently heated by a laser 3990 to form the target additive part 3991.
[0151] FIG. 40 illustratively depicts another particular application of the current disclosure wherein a feedstock stream 4010 is non-thermal direct reduced by a cold plasma jet 4002 on a path from a nozzle 4001 to a composite material block (e.g. a sputtering target) 4092 in an additive manufacturing arrangement where the reduced feedstock stream 4010 is subsequently pressed by a former 4093 to form the composite material block (e.g. sputtering target) 4092.
[0152] The invention herein can take small particles of minerals, ores, etc. and then apply plasma chemistry to them using non-thermal plasma to drive certain reactions. The concept may be applied to a range of materials, gases, effluents, etc.
[0153] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
[0154] The use of the terms a and an and the and at least one and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term at least one followed by a list of one or more items (for example, at least one of A and B) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms comprising, having, including, and containing are to be construed as open-ended terms (i.e., meaning including, but not limited to,) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein may be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., such as) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
[0155] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
