System and method for processing sulfides

Abstract

According to an example aspect, there is provided a system for processing sulfides comprising: a first chamber configured to generate, preheat, premelt, and / or melt a sulfide; and a second chamber configured to thermally decompose at least part of the sulfide to generate a sulfur containing gas.

Description

SYSTEM AND METHOD FOR PROCESSING SULFIDESFIELD

[0001] The present teachings relate generally to a system and method for processing materials and, more particularly, to thermal decomposition, reduction, and processing of sulfides.BACKGROUND AND OBJECTS

[0002] Metal production from either ores or recycled scrap typically requires a series of energy intensive processing steps to generate a metal product at commercial purity from crude feedstocks. In both native mineral bodies and in consumer, industrial, or manufacturing waste, target metals are normally diluted. As a result, they must first be enriched prior to processing them into finished metallic materials.

[0003] Extraction of metals from mined materials generally begins with a series of comminution and physical beneficiation steps to concentrate target feedstock minerals from bulk ores, using a series of operations including, for example, crushing, grinding, sieving, classification, flotation, dense media separation, gravimetric separation, magnetic separation, and / or electrostatic separation. Similar physical separation methods may also be employed to isolate relevant scrap metal feedstocks from waste for subsequent metal remanufacturing.

[0004] After a target metal or mineral compound has been at least partially enriched, it generally goes through a series of steps including, for example, smelting, reduction, and / or refining operations to produce a final metal or alloy product.

[0005] Smelting is the process of treating a feedstock material with chemical and heating agents to extract a target element from a mixed metal compound, such as a mineral. Through the smelting process, a desired element of the feedstock is generally sequestered in a molten target alloy, oxide slag, sulfide matte, or arsenide / antimonide speiss phase, while impurities are removed through exhaust gas or other immiscible molten alloys, slags, mattes, or speiss phases. This process usually involves employing heat generated from smelting reactions or utilizing supplemental heating to melt the feedstock so that distinct immiscible product phases can be separated from one another via density.

[0006] Excess process heat can be utilized to melt scrap metals and recycle them for remanufacture. While smelting further enriches and purifies the target metallic component of the mineral feedstock in an alloy, slag, matte, or speiss phase, the target metallic element may still require further treatment through a process called reduction to convert it into a pure metal or alloy product.

[0007] Reduction is the step of converting a feedstock material to a metal product through methods such as thermal decomposition, vacuum decomposition, electrochemical decomposition, or reaction with a chemical reductant called a reducing agent. Reduction can be conducted under a variety of conditions, including through low temperature aqueous methods or high temperature molten methods. Choices for reduction pathway and reducing agent are made based on chemical, engineering, and operational considerations.

[0008] For example, in conventional carbothermic reduction of oxides, a carbon reducing agent (e.g. coal, coke, natural gas, biomass, etc.) is reacted with an oxide feedstock in a furnace to produce a crude metal and an exhaust gas such as carbon monoxide or carbon dioxide. Depending on the target product, different furnaces or reactors may be employed, including but not limited to a blast furnace, shaft furnace, multihearth furnace, kiln, fluidized bed, electric arc furnace, or submerged arc furnace.

[0009] Non-carbon reductants may also be employed, such as metals (e.g. aluminum, magnesium, calcium, silicon, chromium, iron), hydrogen, oxygen, and sulfur. When a metallothermic reductant is employed to reduce a metal oxide, the reductant metal exchanges with the target metal in the oxide phase, producing an alloy of the target metal as well as an oxide or slag containing the reductant metal.

[0010] Reduction of a compound without a reducing agent may be achieved in some instances via thermal decomposition or electrochemical decomposition as a result of the system chemistry. In principle, many types of metal feedstock compounds (e.g. oxide, sulfide, oxysulfide, chalcogenide, phosphate, carbonate, arsenide, halide, etc.) can be reduced to crude metal products through the use of appropriate reductants, processing conditions, and furnace or reactor designs. Once a crude metal product has been reduced, it may require further refining to meet market or subsequent processing specifications.

[0011] Following reduction, excess reductants (e.g. carbon, aluminum, silicon, etc.) or feedstock impurities (e.g. sulfur, silicon, iron, phosphorous, etc.) may still be present inthe crude metal. These impurities may be removed via a variety of processing options, including but not limited to molten state pyrometallurgy with gases, reductants, or slags, molten state electrometallurgy, aqueous electrometallurgy, distillation, and / or controlled solidification.

[0012] One approach to improve the sustainability of metals production is to shift from oxide-based to sulfide-based processing chemistries. Decarbonization of oxide-based processing in metals production is challenging due to the current reliance on carbon as a reductant. Sulfide-based processing however can allow feedstocks to be reduced to metals with lower direct greenhouse gas emissions.

[0013] Sulfidation is a process of converting oxide, sulfate, carbonate, phosphate, selenide, telluride, antimonide, arsenide, or metal alloy feedstocks into sulfides using a sulfur source, such as hydrogen sulfide, carbon disulfide, elemental sulfur, sulfur dioxide, or sulfide ions. For example, the sulfidation may selectively convert an oxide or other material in a feedstock to a sulfide using elemental sulfur, and desulfidation that selectively converts a sulfide in a feedstock to an oxide or other material. The sulfidation may be conducted via solid gas reactions in a roasting environment, as opposed to, for example, direct liquid state sulfidation of an already molten oxide.

[0014] Once a material has been converted to a sulfide, it can be reduced to metal without the use of carbon reductants. For example, sulfides may be reduced via hydrogen, albeit with high gas flowrates, the use of plasma, or complex gas scrubbing and recycling streams to mitigate hydrogen sulfide accumulation. Sulfides may be reduced via molten sulfide electrolysis; however, this approach requires the design of a supporting electrolyte to enable ionic conduction.

[0015] Another approach is to use metallothermic reductants with sulfides. When a metallothermic reductant is employed with oxide feedstocks, the reductant is usually lost in the slag phase produced during the reduction, making it difficult to recover or regenerate the reductant. However, when metallothermic reductants such as aluminum are employed with sulfides, the byproduct aluminum sulfide may be readily recovered. This allows for the reductant to be regenerated for reuse via electrochemical or other methods. For example, a process of aluminothermic reaction of a metal sulfide may be used to produce an alloy product. The process can be used to obtain various metals and alloys such as manganese, molybdenum, titanium, tungsten, chromium, vanadium, niobium, tantalum, and nickel fromtheir respective sulfides. During production of ferroalloys from sulfides with components that have a strong affinity for aluminum or comparable sulfide volatilities with aluminum sulfide, the use of aluminothermic reduction may contaminate the alloy product with excess aluminum.

[0016] Aluminothermic reduction of sulfides may be conducted using an aluminum solvent via reactive vacuum distillation that enables consumed aluminum recovery as distilled aluminum sulfide. This process can be controlled using the aluminum to sulfur ratio in the gas phase and the corresponding competition between sulfide aluminothermic reduction and thermal decomposition. In addition, reactive stripping of impurities from sulfides and metals may use gas phase species in the presence of aluminum sulfide. However, the presence of appreciable aluminum in the system, even at a low aluminum to sulfur ratio in the gas phase, hinders the ability to extract and recovery impurities from alloy products that have an affinity for aluminum in liquid alloys, including silicon and phosphorous. Some sulfides, due to their thermodynamic stability, are amenable to direct thermal decomposition to produce a metal or sulfur depleted matte and sulfur gas without an aluminum sulfide reductant. Thermal decomposition of sulfides in parallel with aluminothermic reduction of sulfides has been observed for ferroalloy production from mixed sulfide precursors. During thermal decomposition of sulfides, volatile species may be generated that react with other components of the system, to enable their removal via reactive stripping. This was previously reported for boron removal during sulfidation of rare earth magnets and subsequent thermal decomposition of iron sulfide. However, gas phase methods of process control for impurity removal via reactive stripping using sulfur compounds beyond control the aluminum to sulfur ratio in the gas phase and the partial pressure of aluminum sulfide have not been explored.

[0017] Direct thermal decomposition of sulfides without aluminothermic reduction to produce metal and elemental sulfur has been demonstrated for a range of metal products, including molybdenum, and tungsten. However, the role of volatized sulfur species to aid in impurity removal, and corresponding process control and reactor design, has not been explored.

[0018] An object of the present invention is thus to mitigate at least some of the above-mentioned problems.SUMMARY

[0019] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0020] According to a first aspect of the present disclosure, there is provided a system for processing materials, comprising:- a first chamber configured to generate, preheat, premelt, and / or melt a sulfide; and - a second chamber configured to thermally decompose at least part of the sulfide to generate a sulfur containing gas.

[0021] Significant benefits are gained with aid of the present method. The present system enables a reduction-refining process for the sulfide to be conducted using thermal decomposition of the sulfide in a chamber for reduction. Direct thermal decomposition of the sulfide may serve as a prereduction and / or the main or primary reduction step in a metal production process.

[0022] In an embodiment, the system includes a first chamber configured to produce, preheat, premelt, and / or melt a sulfide matte, and a second chamber configured to thermally decompose at least a portion of the sulfide matte to produce a sulfur deficient or depleted matte or metal product and a sulfur containing gas.

[0023] In one embodiment, the sulfur containing gas strips or separates at least a portion of a metallic, metalloid, or nonmetallic impurity from the sulfide matte, sulfur depleted matte, or metal product to form a sulfur containing gaseous compound of the impurity. The sulfur containing gas may strip or separate at least a portion of the metallic, metalloid, or nonmetallic impurity in the second chamber.

[0024] In one embodiment, the first and second chambers are positioned inside of the same chamber.

[0025] In one embodiment, following thermal decomposition the sulfur depleted matte or metal product is transferred back to at least one of the first chamber and a third chamber for subsequent processing.

[0026] In one embodiment, the sulfur containing gas strips or separates at least a portion of a metallic, metalloid, or nonmetallic impurity from the sulfide matte, sulfur depleted matte, or metal product to form a volatile sulfur containing impurity compound,and the system includes an additional chamber area adapted to react the volatile sulfur containing impurity compound with a metal to form an alloy of the metal and the impurity and recover at least a portion of the sulfur in the sulfur containing impurity compound in elemental form.

[0027] In one embodiment, at least one of the chambers are in an arc furnace (e.g., an AC arc furnace, a DC arc furnace, or a submerged arc furnace), an induction furnace, an electron beam furnace, a rotary kiln, a shaft furnace, a multihearth furnace, a fluidized bed reactor, a flash smelter, an electroslag remelter, a vacuum arc remelter, or a converter.

[0028] In one embodiment, thermal decomposition of the sulfide matte is conducted as a prereduction treatment for subsequent metallothermic reduction, roasting, hydrogen reduction, or smelting of the sulfur depleted matte or metal product.

[0029] In one embodiment, a ratio of sulfur to silicon sulfide in the gas phase is controlled to strip or separate silicon from the sulfide matte, sulfur depleted matte, or metal product.

[0030] In one embodiment, a ratio of sulfur to phosphorous sulfide in the gas phase is controlled to strip or separate phosphorous from the sulfide matte, sulfur depleted matte, or metal product.

[0031] In one embodiment, a ratio of sulfur to magnesium sulfide in the gas phase is controlled to strip or separate magnesium from the sulfide matte, sulfur depleted matte, or metal product.

[0032] In one embodiment, a ratio of sulfur to calcium sulfide in the gas phase is controlled to strip or separate calcium from the sulfide matte, sulfur depleted matte, or metal product.

[0033] In one embodiment, the sulfide matte contains at least one of iron, nickel, chromium, molybdenum, cobalt, silicon, magnesium, calcium, vanadium, titanium, tungsten, niobium, or tantalum.

[0034] In one embodiment, the sulfur containing gas strips or separates at least a portion of a metallic, metalloid, sulfosalt, or nonmetallic impurity from the sulfide matte, sulfur depleted matte, or metal product to form a volatile sulfur containing impurity compound. The volatile sulfur containing impurity compound contains at least one oflithium, sodium, potassium, magnesium, calcium, boron, silicon, zinc, tin, nitrogen, phosphorous, arsenic, antimony, selenium, tellurium, fluorine, chlorine, and carbon.

[0035] In one embodiment, the system includes a third chamber for subsequent processing and at least one of the first, second, or third chambers are in an arc furnace (e.g., an AC arc furnace, a DC arc furnace, or a submerged arc furnace), an induction furnace, an electron beam furnace, a rotary kiln, a shaft furnace, a multihearth furnace, a fluidized bed reactor, a flash smelter, an electroslag refiner, a vacuum arc remelter, or a converter.

[0036] In one embodiment, the sulfide matte is at least partially decomposed under vacuum pressure, such as partial or full vacuum.

[0037] In one embodiment, a volatile compound of sulfur and an impurity is formed during the thermal decomposition and the volatile compound is reacted with at least a portion of a metal or alloy to produce an alloy of the metal and the impurity and to recover at least a portion of the sulfur in elemental form.

[0038] In one embodiment, a volatile compound of sulfur and a first nonmetallic or metalloid element is formed during the thermal decomposition and the volatile compound is reacted with at least a portion of an alloy or compound of a second metal to generate a sulfide of the second metal. At least a portion of the first nonmetallic or metalloid element of the volatile compound may be isolated from the sulfide of the second metal.

[0039] In one embodiment, at least a portion of a first nonmetallic or metalloid impurity element is preferentially reacted, distilled, condensed, or isolated from a second nonmetallic or metalloid impurity element.

[0040] In one embodiment, an arc furnace (e.g., an AC arc furnace, a DC arc furnace, or a submerged arc furnace), an induction furnace, an electron beam furnace, a rotary kiln, a shaft furnace, a multihearth furnace, a fluidized bed reactor, a flash smelter, an electroslag refiner, a vacuum arc remelter, or a converter is employed for thermally decomposing the sulfide matte and / or reacting the sulfur containing gas with a nonmetallic or metalloid element.

[0041] According to a second aspect of the present disclosure, there is provided a method for processing sulfides, comprising:- generating, preheating, premelting, and / or melting a sulfide in a first chamber; andthermally decomposing at least part of the sulfide to generate a sulfur containing gas in a second chamber.BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG. 1 is a schematic diagram of a material processing system where the second chamber is positioned within the first chamber, in accordance with at least some embodiments.

[0043] FIG. 2 is a schematic diagram of a material processing system where the second chamber is positioned outside the first chamber, in accordance with at least some embodiments.

[0044] FIG. 3 is a schematic diagram of a multi chamber material processing system where the second chamber is outside the first chamber and a conduit from the second chamber leads into a third chamber, in accordance with at least some embodiments.

[0045] FIG. 4 is a schematic view of a multi chamber material processing system that includes a third chamber connected to an exhaust stream from the second chamber to perform condensation of compounds or elements from the exhaust stream, in accordance with at least some embodiments.

[0046] FIG. 5 is a schematic view of a furnace where the vacuum chamber includes an open bottom bell that is immersed in the molten material, in accordance with at least some embodiments.

[0047] FIG. 6 is a schematic diagram of a process for matte reduction and recovery of distillate byproducts from exhaust streams in a multi chamber materials processing system, in accordance with at least some embodiments.

[0048] FIG. 7 is a schematic diagram of a process for matte reduction and separation of multiple exhaust byproducts in a multi chamber materials processing system, in accordance with at least some embodiments.

[0049] FIG. 8 is a diagram of thermodynamically derived sulfur partial pressures for the thermal decomposition of pure metal sulfides to metal and sulfur gas at a total pressure of 1 atm as a function of temperature.

[0050] FIG. 9 is a diagram of thermodynamically derived sulfur partial pressures (Ps2)cr(tfor the thermal decomposition of nickel sulfide to metal and sulfur gas at various metal sulfide to metal activity ratios at a total pressure of 1 atm.

[0051] FIG. 10 is a diagram of the thermodynamically derived silicon capacity of the gas phase (PSis2I Ps2)crit as a function of temperature for various silicon activities in a metal sulfide or product.

[0052] FIG. 11 is a diagram of the thermodynamically derived phosphorous capacity of the gas phase (PpS2 / Ps2)critas afunction of temperature for various phosphorous activities in a metal sulfide or product.

[0053] FIG. 12 is a diagram of ratios of nickel to various impurities for the sulfide feedstock and the metal / metal sulfide product from the thermal decomposition as reported in Table 1.DETAILED DESCRIPTIONDefinitions

[0054] In the present context, the term “matte” refers to a metal sulfide, a metal sulfide mixture, a sulfosalt or any mixture thereof. The matte can be at least partially molten, i.e., in a semi-liquid or liquid form.

[0055] A "computing system" may provide functionality for the present teachings. The computing system may include software executing on computer readable media that may be logically (but not necessarily physically) identified for particular functionality (e.g., functional modules). The computing system may include any number of computers / processors, which may communicate with each other over a network. The computing system may be in electronic communication with a datastore (e.g., database) that stores control and data information. Forms of computer readable media include, but are not limited to, disks, hard drives, random access memory, programmable read only memory, or any other medium from which a computer can read.

[0056] For purposes of explanation and not limitation, specific details are set forth such as particular architectures, interfaces, techniques, etc. in order to provide a thoroughunderstanding. In other instances, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description with unnecessary detail.

[0057] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to a / an / the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. The use of "first", "second," etc. for different features / components of the present disclosure are only intended to distinguish the features / components from other similar features / components and not to impart any order or hierarchy to the features / components.

[0058] Recitations of numerical ranges by endpoints include all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). Where a range of values is "greater than", "less than", etc., of a particular value, that value is included within the range.

[0059] Any direction referred to herein, such as "top," "bottom," "left," "right," "upper," "lower," "above," below," and other directions and orientations are described herein for clarity in reference to the figures and are not to be limiting of an actual device or system or use of the device or system. Many of the devices, articles, or systems described herein may be used in a number of directions and orientations.

[0060] In the present description, the terms “reactor” and ’’chamber” can be used interchangeably.Embodiments

[0061] There is an ongoing need for alternative sulfide metal reduction pathways in view of the limitations of existing processes. It would be beneficial to develop systems and / or methods that address and overcome the limitations of the existing approaches. For example, it is desirable to use gas phase sulfur and metal sulfide chemistry to conduct melt refining and metal separation during reduction in ways not achieved in aluminothermic reduction of sulfides via reactive vacuum distillation and reactive stripping. Additionally, enabling recovery of volatile impurities such as silicon, phosphorous, and magnesium, either as sulfides or through contact with a metal to form an alloy, without excessive aluminum contamination in the alloy or the recovered impurity, would be beneficial.

[0062] Conventional metal sulfide reduction takes place in a variety of furnaces via a range of processing chemistries. Hydrometallurgical routes include, but are not limited to, hydrogen reduction in aqueous systems, such as in an autoclave. Pyrometallurgical routes include, but are not limited to, smelting or conversion with oxygen using smelters and converters, or calcination in a kiln, multihearth furnace, or fluidized bed followed by carbothermic or hydrogen reduction. The previously used systems provide the aluminothermic reduction of sulfides via reactive vacuum distillation in an induction furnace at pyrometallurgical temperatures. Vacuum furnaces are utilized today for a range of metallurgical processes, including but not limited to, high temperature sintering, hot pressing for powder compaction or diffusion bonding, vacuum and thermal heat treating, precision vacuum brazing, degassing such as via a Ruhrstahl Heraeus (RH) degasser or vacuum induction degasser, and refining such as via arc remelting. However, these existing vacuum furnace systems fail to address unresolved challenges pertaining to materials transport between processing steps during vacuum distillation, exhaust management, byproduct recovery. Furthermore, the use of aluminum as a reductant in previously used systems may lower product purity through aluminum contamination and through retainage of impurities with a high affinity for aluminum.

[0063] An RH degasser is a vacuum treatment process used to remove hydrogen and other gases from molten steel. A refractory-lined vessel with two snorkels may be immersed into a ladle of liquid steel. Argon may be injected through the upper snorkel, creating a pressure differential that moves the steel up the snorkel and across the vessel's bottom to the lower snorkel. A partial amount of the steel may then be sucked into the reaction vessel under vacuum.

[0064] One goal in RH processes is to reduce the brittleness of the finished steel by removing hydrogen and other gases. The process can also be used to produce ultra-low carbon steel grades. RH degassers may be used today for removal of minor volatile impurities.

[0065] RH degassers can have a role in desulfurization, even though they have not been designed to incorporate aluminum inputs for aluminothermic reduction or for bulk sulfide thermal decomposition. Vacuum degassing can also help control alloys by allowing for precise additions of trace elements like boron, titanium, and niobium.

[0066] RH degassers have also not been designed to incorporate condensation of evolved gaseous species into a liquid, such as elemental sulfur or aluminum sulfide.

[0067] Composition adjustment by sealed argon bubbling-oxygen blowing (CAS-OB) utilizes a bell partially submerged in a molten metal alloy bath to enable temperature control and controlled alloying of the melt during ladle treatment. Through the use of the bell, a limited surface of the melt can be exposed to various melt reaction conditions, alleviating challenges with gas atmosphere control. However, this approach has not been considered for the management of sulfide reduction exhaust gas and reduction byproduct management.

[0068] According to an aspect, there is provided a system for processing sulfides, comprising:- a first chamber configured to generate, preheat, premelt, and / or melt a sulfide; and - a second chamber configured to thermally decompose at least part of the sulfide to generate a sulfur containing gas.

[0069] The present system enables a reduction-refining process for the sulfide, i.e., metal sulfide feedstock, to be conducted using thermal decomposition of the sulfide in a chamber for reduction. Direct thermal decomposition of the sulfide may serve as a prereduction and / or the main or primary reduction step in a metal production process.

[0070] The sulfide can be a metal sulfide or a metal sulfide matte. The second chamber can be configured to produce a sulfur deficient or depleted metal sulfide matte or a metal product and a sulfur containing gas.

[0071] The present system may utilize thermal decomposition of sulfides as a means to conduct metal separation, reduction, and refining. Thermal decomposition of sulfides may enable sulfide metal reduction pathways that provide improvements over existing reduction approaches. For example, in some examples, gas phase sulfur and metal sulfide chemistry can be used to conduct melt refining and metal separation in ways not achieved in aluminothermic reduction of sulfides via reactive vacuum distillation. Advantageously, direct thermal decomposition of sulfides can enable recovery of volatile impurities such as silicon, phosphorous, and magnesium, either as sulfides or through contact with a metal to form an alloy, without excessive aluminum contamination in the alloy or the recovered impurity. In some examples, thermal decomposition may be used as a prereduction step priorto reduction or roasting in order to reduce the reagent consumption and recover sulfur in elemental form.

[0072] The system may comprise one or more first chambers configured to generate, preheat, premelt, and / or melt a sulfide.

[0073] The system may comprise one or more second chambers configured to thermally decompose the sulfide to generate a sulfur containing gas.

[0074] According to an embodiment, the system further comprising a third chamber configured to react the sulfur containing gas with a metal to form an alloy and recover sulfur.

[0075] The system may comprise one or more third chambers configured to react the sulfur containing gas with a metal to form an alloy and recover sulfur.

[0076] According to an embodiment, the alloy and sulfur are free from aluminum contamination.

[0077] In some examples, the sulfide, a sulfide feedstock, or a sulfide matte, may be thermally decomposed in the first chamber or the second chamber, which generates the sulfur containing gas. The sulfide matte may be thermally decomposed under atmospheric pressure, partial vacuum, or full vacuum. For example, a sulfide of a metal may be decomposed to generate the sulfur containing gas, where the metal may include chromium, nickel, cobalt, iron, molybdenum, vanadium, titanium, niobium, or tantalum. In some examples, the first chamber may generate a sulfur deficient metal compound or alloy in addition to the sulfur containing gas. The sulfur containing gas may react with impurities from the sulfide matte or metal in the first chamber or second chamber. The impurities may include, but are not limited to, lithium, sodium, potassium, magnesium, calcium, boron, silicon, zinc, tin, nitrogen, phosphorous, arsenic, antimony, selenium, tellurium, fluorine, chlorine, or carbon. In some examples, the reaction product of the evolved sulfur containing gas and impurities is a gaseous sulfur containing compound of one or more impurities.

[0078] According to an embodiment, the first chamber, the second chamber and / or the third chamber, may comprise, but is not limited to, an arc furnace (e.g., an AC arc furnace, a DC arc furnace, or a submerged arc furnace), an induction furnace, an electron beam furnace, a rotary kiln, a shaft furnace, a multihearth furnace, a fluidized bed reactor, a flash smelter, an electroslag refiner, a vacuum arc remelter, or a converter.

[0079] In some examples, the thermal decomposition does not necessarily need to occur under vacuum. For example, in some examples, thermal decomposition of the metal sulfide may be achieved through leveraging the elevated temperature in the vicinity of an arc in an arc furnace at or near ambient pressures.

[0080] According to an embodiment, the sulfide is thermally decomposed under vacuum pressure.

[0081] According to an embodiment, the sulfide is thermally decomposed under approximately ambient pressure.

[0082] Existing sulfide reduction furnaces typically rely on smelters and converters. An arc furnace approach according to some present examples provides increased versatility, for example, enabling multiple reduction and refining stages to be coupled into a single arc furnace with multiple electrode sets and / or sequential arc furnaces within a single process block, although not limited thereto.

[0083] The first chamber, the second chamber and / or the third chamber may comprise multiple electrodes in series, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or more. Each of one or more chambers (in a single arc furnace or different arc furnaces) may each have its own series of electrodes.

[0084] The second chamber may also contain single or multiple tapholes in different locations and heights for introduction or removal of different sulfidizing agents, calcination agents, decomposition agents, reducing agents, feedstocks, or products from the furnace, although not limited thereto. Having multiple chambers or furnaces connected together can reduce the need for chamber or furnace tapping and ladle transport and minimize molten sulfide exposure to ambient conditions, although not limited thereto.

[0085] The first chamber, the second chamber and / or the third chamber or their bottom design may be slanted to enable gravimetric transfer of materials between processing steps.

[0086] The system may comprise multiple chamber areas for conducting the process. The chamber areas can be defined by separate furnaces connected by piping, although not limited thereto. In some examples, a larger system may be split into chamber areas, each operating like a separate furnace. In some examples, one chamber area may be containedwithin another chamber area or the chamber areas may be arranged together within a single furnace.

[0087] According to an embodiment, the first chamber and the second chamber are positioned inside of the same furnace, reactor or converter.

[0088] According to an embodiment, the second chamber is positioned within the first chamber.

[0089] According to an embodiment, the second chamber is positioned outside of the first chamber.

[0090] In some examples, the chamber areas may consist of or be separated by structures such as partition walls or dams. Various partitioning designs between chambers and / or furnaces may be utilized, including tap based or walls for liquid to flow over or under into a subsequent processing chamber. Various roof types may also be employed, including refractory or water-cooled metals. A variety of materials may be utilized for roofs, walls, refractory linings, or partitioning, including but not limited to carbon, graphite, metal carbides (e.g. silicon carbide, chromium carbide, etc.), copper-based alloys, stainless steel, nickel-based alloys, chromium-based alloys, refractory metal based alloys (e.g. alloys containing one or more of niobium, tantalum, molybdenum, tungsten, rhenium, etc.), chromite refractories (e.g. magnesiochromite, calciochromite, etc.), oxide-carbon refractories (e.g. magnesiocarbon), phosphate-containing refractories (e.g. monazite, calcium phosphate, etc.), oxide-based refractories (e.g. oxides containing one or more of alumina, magnesia, calcia, silica, zirconia, hafnia, yttria, rare earth oxides, etc.).

[0091] According to an embodiment, the sulfide is a sulfide or a metal, and the second chamber is configured to thermally decompose the sulfide of the metal to generate the sulfur containing gas.

[0092] According to an embodiment, the metal comprises chromium, nickel, cobalt, iron, molybdenum, vanadium, titanium, tungsten, niobium, or tantalum.

[0093] According to an embodiment, the sulfide comprises a nonmetallic or metalloid element, i.e., impurity. The nonmetallic or metalloid impurity can be present in a feedstock comprising the sulfide. The present system enables removing the impurities at least partially from a sulfide matte or metal product by the thermal decomposition.

[0094] According to an embodiment, the sulfur containing gas comprises lithium, sodium, potassium, magnesium, calcium, boron, silicon, zinc, tin, nitrogen, phosphorous, arsenic, antimony, selenium, tellurium, fluorine, chlorine, or carbon.

[0095] According to an embodiment, the sulfide comprises a metallic, metalloid, sulfosalt or nonmetallic impurity, wherein the sulfur containing gas is configured to strip or separate at least a portion of the metallic, metalloid, or nonmetallic impurity from the sulfide to form a sulfur containing gaseous compound of the impurity.

[0096] According to an embodiment, the sulfide comprises silicon sulfide, wherein a ratio of sulfur containing gas to the silicon sulfide is controlled to separate silicon from the silicon sulfide.

[0097] According to an embodiment, the sulfide comprises phosphorus sulfide, wherein a ratio of sulfur containing gas to the phosphorous sulfide is controlled to separate phosphorous from the phosphorus sulfide.

[0098] According to an embodiment, the sulfide comprises magnesium sulfide, wherein a ratio of sulfur containing gas to the magnesium sulfide is controlled to separate magnesium from the magnesium sulfide.

[0099] According to an embodiment, the sulfide comprises calcium sulfide, wherein a ratio of sulfur containing gas to the calcium sulfide is controlled to separate calcium from the calcium sulfide.

[0100] According to an embodiment, the sulfide comprises a metallic, metalloid, or nonmetallic impurity, wherein the sulfur containing gas is configured to strip or separate at least a portion of the metallic, metalloid, or nonmetallic impurity from the sulfide to form a sulfur containing gaseous compound of the impurity.

[0101] According to an embodiment, the sulfide comprises silicon sulfide, wherein a ratio of sulfur containing gas to the silicon sulfide is controlled to separate silicon from the silicon sulfide

[0102] According to an embodiment, the sulfide comprises phosphorus sulfide, wherein a ratio of sulfur containing gas to the phosphorous sulfide is controlled to separate phosphorous from the phosphorus sulfide.

[0103] According to an embodiment, the sulfide comprises magnesium sulfide, wherein a ratio of sulfur containing gas to the magnesium sulfide is controlled to separate magnesium from the magnesium sulfide

[0104] According to an embodiment, the sulfide comprises calcium sulfide, wherein a ratio of sulfur containing gas to the calcium sulfide is controlled to separate calcium from the calcium sulfide.

[0105] According to an embodiment, the second chamber is configured to perform metallothermic reduction. In some examples, the metallothermic reduction can be aluminothermic reduction. The aluminothermic reduction can be performed on molten sulfides or matte.

[0106] In some examples, the thermal decomposition may be used in lieu of the metallothermic reduction, e.g., aluminothermic reduction, of the metal sulfide. In some examples, the thermal decomposition may be used as a prereduction step prior to the metallothermic reduction in order to reduce the consumption of metallothermic reductant, e.g., aluminum, and pre-purify the matte.

[0107] According to an embodiment, the system further comprises:- a first conduit connected between the first chamber and the second chamber and configured to transfer the sulfide from the first chamber to the second chamber using vacuum pressure; and- a second conduit connected to the second chamber and configured to transfer the sulfur containing gas from the second chamber.

[0108] The system may comprise one or more first conduits, such as two first conduits.

[0109] The system may comprise one or more second conduits, such as two second conduits.

[0110] According to an embodiment, the second chamber is configured to introduce a metal to serve as a reductant, such that the sulfur containing gas is extracted through reduction.

[0111] According to an embodiment, the second conduit is configured to condense sulfur, aluminum sulfide, magnesium sulfide, silicon sulfide, calcium sulfide, boron sulfide,aluminum oxide, magnesium oxide, silicon oxide, calcium oxide, boron oxide, a ferroalloy, or an aluminum alloy.

[0112] According to an embodiment, the second conduit is configured to oxidize sulfur a sulfide or sulfosalt of aluminum, silicon, magnesium, calcium, strontium, barium, molybdenum, tungsten, phosphorous, arsenic, antimony, selenium, or tellurium.

[0113] According to an embodiment, the second conduit or the second chamber is configured to separate sulfur, a ferroalloy, an aluminum alloy, or oxides, oxysulfides, sulfides, sulfates, sulfosalts, carbonates, or carbides of aluminum, silicon, magnesium, calcium, strontium, barium, molybdenum, tungsten, zinc, phosphorous, arsenic, antimony, selenium, and / or tellurium from one another via condensation, distillation, magnetic separation, or electrostatic separation.

[0114] According to an embodiment, the second chamber is further configured to generate a metal or a sulfur depleted matte.

[0115] According to an embodiment, the system further comprises the third chamber, wherein the second conduit is configured to transfer the metal or the sulfur depleted matte to the third chamber.

[0116] According to an embodiment, the first chamber, the second chamber and / or the third chamber is configured to generate a sulfur deficient metal compound or alloy in addition to the sulfur containing gas.

[0117] According to an embodiment, the first chamber is configured to perform sulfidation and the third chamber is configured to perform refining.

[0118] According to an embodiment, the second chamber is configured to produce a metal alloy.

[0119] According to an embodiment, the first and / or second conduit comprises a snorkel, a tube or a pipe. In some examples, a snorkel-based reactor may be used to conduct thermal decomposition of sulfides in a separate, second chamber from the main reactor liquid pool in the first chamber. The snorkel system can be used to transfer material between sulfidation, reduction, and refining chambers and / or reactors.

[0120] According to an embodiment, the system comprises a bell-shaped reactor or conduit. In some examples, a bell-shaped reactor or conduit may be used to conduct aluminothermic reduction and / or thermal decomposition of sulfides within a vacuum chamber created above the melt by immersing the bell into the molten matte bath. The bellshaped reactor can be used to eliminate the need for transfer conduits and can be therefore beneficial in systems where the produced metal or sulfur deficient matte is returned to the first chamber from the second chamber.

[0121] According to an example, the first chamber and the second chamber is the same chamber. For example, generating, preheating, premelting, and / or melting a sulfide and thermally decomposing of at least part of the sulfide can be conducted in consecutive process steps in the same chamber.

[0122] The various embodiments and variants disclosed here in connection with the system apply mutatis mutandis to the method.

[0123] According to an aspect, there is provided a method of processing sulfides, comprising:- generating, preheating, premelting, and / or melting a sulfide in a first chamber; and- thermally decomposing at least part of the sulfide to generate a sulfur containing gas in a second chamber.

[0124] According to an embodiment, the method further comprises transferring the sulfide from the first chamber to the second chamber via a first conduit.

[0125] According to an embodiment, the method further comprises transferring the thermally decomposed sulfide from the second chamber to a third chamber via the second conduit.DETAILED DESCRIPTION OF THE DRAWINGS

[0126] The present teachings are described more fully hereinafter with reference to the accompanying drawings, in which the present embodiments are shown. The following description is presented for illustrative purposes only and the present teachings should not be limited to these embodiments. Any computer configuration and architecture satisfyingthe speed and interface requirements herein described may be suitable for implementing the system and method of the present embodiments.

[0127] It will be appreciated that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of illustrated embodiments of the present disclosure.

[0128] In the figures, a metallic reductant can be fed to a second chamber for a metallothermic reduction as alternative to thermal decomposition.

[0129] Referring now to FIG. 1, a schematic view of a material processing system 100 is provided. The material processing system 100 may include a furnace, reactor or vessel. In some examples, the material processing system 100 may include a furnace configured to conduct sulfidation. In some examples, the material processing system 100 may include a furnace or a chamber for preheating or melting a metal sulfide produced in a separate process to form a liquid sulfide matte. For example, the material processing system 100 may include, but is not limited to including, an arc furnace (e.g., an AC arc furnace, a DC arc furnace, or a submerged arc furnace), an induction furnace, an electron beam furnace, a rotary kiln, a shaft furnace, a multihearth furnace, a fluidized bed reactor, a flash smelter, an electroslag refiner, a vacuum arc remelter, or a converter.

[0130] In the illustrated examples, the material processing system 100 may include a first chamber 102. A chemical feedstock, such as a sulfide, a metal sulfide or sulfide matte, may be introduced into the first chamber 102 via chute and / or hopper 119 to form a molten matte 106. In some examples, the sulfide matte feedstock includes a sulfide of at least one of chromium, nickel, cobalt, iron, molybdenum, vanadium, titanium, tungsten, niobium, and tantalum.

[0131] The material processing system 100 may include one or more heating elements that are operable to produce a molten matte 106 from the chemical feedstock in the first chamber 102, as is known in the art. In some examples, the heating elements may be operable to produce the molten matte 106 at a temperature sufficient to conduct thermal decomposition at a given pressure. In some examples, the heating elements may include an electric arc, induction heater, or plasma source.

[0132] The material processing system 100 may also include a second chamber 202 that is connected to the first chamber 102 via a plurality of transfer conduits 110, e.g., snorkels, tubes, pipes, etc., although not limited thereto. The second chamber 202 may receive at least a portion of the molten matte 106, i.e. sulfide to be processed, via one or more of the transfer conduits 110. In some examples, the entire molten matte 106 can be circulated through the second chamber 202 and back into the first chamber 102 via the transfer conduits 110. The second chamber atmosphere 204 may be maintained at atmospheric, partial vacuum, or full vacuum pressure. The molten matte 106 may be drawn, electromagnetically pumped, suctioned, or vacuumed into the second chamber 202. In some examples, the molten matte 106 may be moved via a pressure differential between the first chamber atmosphere 104 and the second chamber atmosphere 204. The first chamber 102 may include a chamber outlet 116 that can be used to extract process offgas from the first chamber and / or it can be used to regulate the pressure of the first chamber atmosphere 104. Additionally, or alternatively, the molten matte 106 can be directed towards the second chamber 202 using any fluid motive source known to those skilled in the art.

[0133] The pressure in the second chamber atmosphere 204, e.g., atmospheric, partial vacuum, or full vacuum, may be suitable to at least partially decompose the molten matte 106 in the second chamber 202 via thermal decomposition. The thermal decomposition of the molten matte 106 inside chamber 202 may produce a sulfur deficient or depleted (or metal enriched) molten matte 206, i.e. reduced sulfide or material, that can be returned to the first chamber 102, via one or more of the transfer conduits 110, for further processing. The first chamber may include a tapping hole 122 that can be used to extract molten matte 106 and / or depleted molten matte 206. The thermal decomposition may also produce extracted gases 216, e.g., volatile compounds expelled from the molten matte 106 during thermal decomposition, i.e. a sulfur containing gas. As described below, the thermal decomposition may occur spontaneously when the pressure in the second chamber atmosphere 204 is below a threshold decomposition pressure, e.g., a threshold partial pressure of the extracted gases 216 at a given temperature of the molten matte 106. Thermal decomposition may occur spontaneously when the processing temperature in the second chamber 202 is above a threshold temperature at a given pressure in the molten matte 106. The extracted gases 216 may exit the second chamber atmosphere 204 via an outlet conduit 218, which may direct the extracted gases 216 elsewhere to be condensed and / or further processing.

[0134] In some examples, the second chamber 202 may include a chute and / or hopper 219 that may be used to introduce a metal in order to perform metallothermic reduction instead of thermal decomposition of the molten sulfide 106. Reaction can yield a metal product and / or sulfur deficient matte 206.

[0135] In some examples in which the molten matte 106 includes metal sulfide, the extracted gases 216 may include sulfur gas and / or volatile sulfides with a different stoichiometry or composition than the molten matte 106. The depleted molten matte 206 may include metal and / or metal sulfide with a different stoichiometry or composition than the molten matte 106. For example, the volatile sulfides in the extracted gases 216 may be relatively enriched with sulfur and the depleted molten matte 206 may be relatively deficient or depleted of sulfur and enriched with metal. Similarly, the volatile sulfides in the extracted gases 216 may be relatively enriched with silicon, phosphorous, or other impurities and the depleted molten matte 206 may be relatively depleted of impurities and enriched with a target metal. Thermal decomposition of the metal sulfide molten matte 106 may occur spontaneously when the pressure in the second chamber atmosphere 204 is below a threshold partial pressure of sulfur gas at a given temperature of the molten matte 106. Thermal decomposition of the metal sulfide molten matte 106 may occur spontaneously when the processing temperature in the second chamber 202 is above a threshold temperature at a given pressure in the molten matte 106.

[0136] In some examples, sulfur gas in the extracted gases 216 may also react with the molten matte 106 and / or the depleted molten matte 206 in the second chamber 202 to produce the volatile sulfides in the extracted gases 216. For example, in some examples, sulfur gas may react with impurity nonmetallic, metalloid, or metallic elements or compounds in the molten matte 106 and / or the depleted molten matte 206 to produce a volatile compound containing sulfur and the nonmetallic or metalloid element or compound. The impurity elements or compounds may include, but are not limited to including, lithium, sodium, potassium, magnesium, calcium, boron, silicon, zinc, tin, nitrogen, phosphorous, arsenic, antimony, selenium, tellurium, fluorine, chlorine, or carbon.

[0137] In some examples, the volatile compounds in the extracted gases 216 may contain sulfur and one or more impurities, including but not limited to, lithium, sodium, potassium, magnesium, calcium, boron, silicon, zinc, tin, nitrogen, phosphorous, arsenic, antimony, selenium, tellurium, fluorine, chlorine, or carbon. Impurity elements may bedissolved in sulfide compounds of the molten matte 106 or the depleted molten matte 206 to matte or alloys of iron, nickel, chromium, molybdenum, cobalt, silicon, aluminum, magnesium, and calcium, for example.

[0138] In some examples, reaction kinetics between the sulfur gases and metallic, nonmetallic, or metalloid elements or compounds in the molten matte 106 or the depleted molten matte 206 may be controlled via a pressure and / or temperature in the second chamber 202. In some examples, the pressure and / or temperature in the second chamber 202 may be controlled to preferentially react the sulfur gas with certain nonmetallic or metalloid elements or compounds. For example, in some examples, the pressure and / or temperature in the second chamber 202 may be controlled to preferentially react the sulfur gas with silicon and / or phosphorus.

[0139] In some examples, a ratio of sulfur to silicon sulfide in the gas phase, or a partial pressure ratio, may be controlled to separate or strip silicon from the molten matte 106 or the depleted molten matte 206 as a volatile, sulfur containing compound. In some examples, a ratio of sulfur to phosphorous sulfide in the gas phase, or a partial pressure ratio, may be controlled to separate or strip phosphorous from the molten matte 106 or the depleted molten matte 206 as a volatile, sulfur containing compound. Similar ratios may be defined for other matte or metal impurities. In some examples, a ratio of sulfur to magnesium sulfide in the gas phase, or a partial pressure ratio, may be controlled to strip or separate magnesium from the molten matte 106 or the depleted molten matte 206 as a volatile, sulfur containing compound. In some examples, a ratio of sulfur to calcium sulfide in the gas phase, or a partial pressure ratio, may be controlled to strip or separate calcium from the molten matte 106 or the depleted molten matte 206 as a volatile, sulfur containing compound.

[0140] In some examples, reaction kinetics between metals and nonmetallic or metalloid elements or compounds in the molten matte 106 or the depleted molten matte 206 may be controlled in the second chamber 202. For example, in some examples, a metal, or an alloy or compound thereof, may react with one or more nonmetallic or metalloid elements and sulfur gas to generate a volatile sulfide of the metal. In this way, impurity elements in the sulfide matte or decomposition product may be preferentially reacted and / or isolated in the second chamber 202.

[0141] The extracted gases 216 containing sulfur gas and volatile sulfides may exit the second chamber 202 via the outlet conduit 218 for further processing, e.g., for subsequentseparation of sulfur and sulfide compounds, although not limited thereto. In some examples, elemental sulfur in the extracted gases 216 may be recovered in a separate chamber area connected to the outlet conduit 118. This separate chamber area may include a molten matte of a metal, such as one or more of iron, nickel, chromium, molybdenum, cobalt, silicon, aluminum, magnesium, and calcium.

[0142] In some examples, volatile sulfides, or volatile impurity compounds, in the extracted gases 216 may react with components or additives in a separate chamber area to regenerate or recover elemental sulfur. For example, in some examples, the volatile impurity compounds or sulfides in the extracted gases 216 may react with an alloy or compound in a separate chamber area to at least partially regenerate or recover elemental sulfur in the extracted gases 216. Additionally, or alternatively, in some examples, the volatile impurity compounds or sulfides in the extracted gases 216 may react with an alloy or compound in a separate chamber area to generate a sulfide of the metal of the molten matte, and at least a portion of the nonmetallic or metalloid element in the volatile compound or sulfide may be isolated from the generated sulfide of the metal.

[0143] In the embodiment of FIG. 1, the second chamber 202 is positioned in the first chamber 102. FIG. 2 depicts another embodiment of a material processing system 200 that is similar to the material processing system 100, with like reference signs used to indicate like elements and components. In this example, the second chamber 202 is positioned outside of the first chamber 102 such that the first chamber 102 and the second chamber 202 are separate chambers connected by the transfer conduits 110. Here again, the molten matte 106 from the first chamber 102 may be drawn, electromagnetically pumped, suctioned, vacuumed, or otherwise moved into the second chamber 202. Thermal decomposition with or without metallothermic reduction of the molten matte 106 and reaction between sulfur gas and the matte 106 or the depleted molten matte 206 may occur in the second chamber 202 as described above.

[0144] Referring now to FIG. 3, in another embodiment of a material processing system 300, a third chamber 302 may be included in addition to the first chamber 102 and the second chamber 202. Like reference signs are used in FIG. 3 to indicate like elements and components between the material processing system 300 and the material processing systems 100, 200 of FIGS. 1 and 2. In this example, the third chamber 302 may be connectedto the second chamber 202 via one or more of the transfer conduits 110. A molten matte or metal 306 may be contained in the third chamber 302.

[0145] The molten matte or metal 306 may include sulfur deficient or depleted (or metal enriched) molten matte 206 from the second chamber 202. The depleted molten matte 206 may be routed to the third chamber 302 and contained therein as the molten metal or matte 306 following thermal decomposition and sulfur gas reaction in the second chamber 202. The depleted molten matte or metal 206 may be collected in the third chamber 302 as the matte or metal 306 for further processing.

[0146] A schematic view of a multi chamber material processing system 400 according to another embodiment is provided in FIG. 4. In this example, the one or more vacuum chambers, i.e. a first chamber 102 and a second chamber 202, may have one or more of a chute and / or hopper 219 for alloys and other raw materials, although not limited thereto. Here, extracted gases 216, i.e. sulfur containing gas, may be continuously removed from the second chamber 202 and / or gaseous product 316 may be removed from one or more subsequent chambers, i.e. a third chamber 302 which may include a condensation product 321 that is separated from the extracted gas 216. Here, the process may be conducted in one or more passes. That is, the unprocessed material may be processed through the vacuum chambers as many times as necessary to achieve the desired product.

[0147] FIG. 5 provides a schematic view of a material processing system 500. In this example, the separation process as described with reference to FIGS. 1-4 may be conducted inside a bell that can be partially submerged into the molten matte 106 to serve as the second chamber 202 and form a second chamber atmosphere 204 that is separated from the first chamber atmosphere 104. Bell design can be used to eliminate the need for transfer conduits and can be therefore beneficial in systems where the produced metal or sulfur deficient matte 206 is returned to the first chamber 102.

[0148] Exemplary processes for processing sulfides through a vacuum reactor are shown in FIG. 6 and FIG 7. Generally, the first chamber may comprise of any vessel used for holding, melting, or producing molten metal sulfide or sulfosalt precursors. A variety of furnace or vessel designs may be used in the first chamber, including but not limited to a kiln, shaft furnace, arc furnace, induction furnace, resistively heated furnace, flash smelter, converter, or ladle, although not limited thereto. In some examples, the first chamber may serve as a sulfidation furnace to produce a sulfide, sulfate, oxysulfide, or sulfosalt reductionfeedstock from various precursor materials, including but not limited to oxides, sulfides, sulfates, oxysulfides, carbonates, phosphates, selenides, tellurides, arsenides, antimonides, or sulfosalts. The sulfidation chamber may melt the feedstock and introduce a sulfidizing agent.

[0149] The internal environment or processing conditions of the sulfidation chamber may be adjusted to target certain metal oxides and convert them to metal sulfides. During this process, sulfur dioxide gas may be generated within the system. Remaining metal oxides may be removed from the sulfidation chamber and furnace system. The metal oxide may be sent to another furnace to undergo additional sulfidation. The converted metal sulfides may then be transferred to a reduction chamber. The reduction chamber may be able to maintain the metal sulfide in a liquid state and may introduce a reduction agent.

[0150] The reduction agent may combine with the sulfur in the metal sulfide to generally produce the desired metal or an alloy of the desired metal, one or more sulfur-containing gases, and a compound of reducing agent and sulfur. Depending on the presence of impurities in the system, other sulfur containing gaseous, liquid, or solid byproducts may be formed, including but not limited to carbon-sulfur compounds, carbonyl compounds, sulfosalts, oxysulfides, and thiophosphates.

[0151] Referring now to FIG. 6, a schematic diagram for processing materials in a multi chamber materials processing system is provided. In this example, multiple reactors for holding and / or processing molten matte are provided and with each reactor a vacuum chamber is provided. A feedstock may be provided to a first reactor and processed through its corresponding vacuum chamber to form a first distillate.

[0152] Additionally, some of the feedstock provided to the first reactor may continue into the second chamber, vessel, or separate chamber or processing step, and the process may be repeated. A second distillate may be formed though the second vacuum chamber and the leftover matte that is not processed through the second chamber may move on to the third reactor for further processing. Although this example depicts three chamber and reactor pairs, a plurality of chamber and reactor pairs may be provided in other examples. Once the feed stock is processed through the final reactor, a slag, gangue, or matte waste is produced. Depending on the configuration, different metals or metal alloys and / or mattes might be extracted from the different reactor steps or chambers.

[0153] FIG. 7 provides another example of a schematic diagram of a process for processing materials in a multi chamber materials processing system. In this example, a single reactor is provided for multiple chambers performing vacuum distillation and condensation steps, although not limited thereto. Although there are three chambers depicted in this example, a plurality of chambers may be used to process materials in other examples.

[0154] Here, a feedstock may enter the reactor and be processed through a first chamber resulting in a first distillate. From there, the first distillate is suctioned into subsequent chambers for processing, producing subsequent distillate. Materials exiting the chambers and not proceeding to subsequent chambers may be regarded as condensate. Additionally, any material exiting the reactor and not proceeding to a subsequent chamber may be regarded as slag, gangue, or matte waste.

[0155] Aspects of the present teachings will now be illustrated with reference to the following non-limiting examples.EXAMPLESExample 1

[0156] As discussed above, the pressure in the second chamber atmosphere 104 of any one or more of the material processing systems 100, 200, 300, 400, 500 can be controlled to achieve the thermal decomposition and desired reaction kinetics in the second chamber 202. Referring to FIG. 8, a sulfur partial pressure (may be determined for the thermal decomposition reaction at thermodynamic equilibrium of a pure metal sulfide to the pure metal and sulfur.

[0157] The determination of a thermodynamically derived (Ps^crtt for pure immiscible compounds is readily appreciated by one skilled in the art. When a metal and its sulfide are in thermodynamic equilibrium with one another, the system P2will equal the thermodynamically derived (Ps^crtt the process conditions. In FIG. 8, thermodynamically derived (Ps^crttarecompared for the thermal decomposition of pure metal sulfides to metal and sulfur gas at a total pressure of 1 atm as a function of temperature. The operationally requiredmay be different than the thermodynamically derived equilibrium due to kinetic, mass transport, solution mixing, and reactor specific effects. When P2or the system pressure are below the operationally required thermaldecomposition of the metal sulfide may be thermodynamically spontaneous, producing the enriched (or sulfur deficient or depleted) metal and sulfur gas.Example 2

[0158] Referring to FIG. 9, a sulfur partial pressure (may be determined for the thermal decomposition reaction at thermodynamic equilibrium of a metal sulfide to the metal and sulfur. The methodology to derive (Ps^crtt forasystem where the metal and metal sulfide are miscible with one another is readily appreciated by one skilled in the art. However, the solution effects that relate the mixing activity of the sulfidewith the metal(aWj) may be experimentally unknown in a molten matte or a mixture of two or more molten mattes, metals, or compounds.

[0159] When a metal and its sulfide are in thermodynamic equilibrium with one another, the system P2may equal the thermodynamically derived (Ps^crtt for the process conditions. In FIG. 9, thermodynamically derived (Ps^crttarecompared for the thermal decomposition of nickel sulfide (N13S2) to metal and sulfur gas at various metal sulfide to metal activity ratios at a total pressure of 1 atm. The ratios of feedstock and product activities can make a sulfide easier (higher PS2) or harder (lowerPS2) to thermally decompose. The operationally required (Ps^crit is usually different than the thermodynamically derived due to kinetic, mass transport, unknown solution mixing, or reactor specific effects.

[0160] When P2and / or the system pressure are below the operationally (F^^crtt thermal decomposition of the metal sulfide may occur, producing the enriched (or sulfur deficient or depleted) metal and elemental sulfur gas. In a system open to sulfur gas, S2, continuous removal of S2 may decrease the metal sulfide and sulfur content of the mixed metal / metal sulfide system. Simultaneously, thecontinue thermal decomposition of the metal sulfide and remove sulfur from the system may also decrease. Various stoichiometries of sulfur (monoatomic S up to Ss) may be considered similarly.Example 3

[0161] Referring to FIGS. 10 and 11, in a metal sulfide or product, some impurities may form volatile sulfides in the presence of sulfur gas that is generated via thermal decomposition of the metal sulfide. For a given impurity (e.g., anionic or cationic), a ratio of the partial pressure of an impurity sulfide to the partial pressure of sulfur gas (PS2) maybe defined as the impurity capacity of the sulfur gas stream. The impurity capacity may be dependent on the mixing behavior of the impurities in the system (activity, a).

[0162] In FIG. 10, a thermodynamically derived silicon capacity of the gas phase Psis2 / Ps2)crit is plotted versus temperature for various silicon activities in the metal product. In FIG. 11, a thermodynamically derived phosphorous capacity of the gas phase (Pps2is plotted versus temperature for various phosphorous activities in the metal product. The operationally achievable (PSis2maY be different than the thermodynamically derived (PSis2respectively, due to kinetic, mass transport, unknown solution mixing, or reactor specific effects.

[0163] Using the methodology of FIGS. 10 and 11, similar ratios and gas phase capacities can be defined for other impurities. In this way, a sulfur to impurity sulfide ratio in the gas phase can be controlled to separate or strip the impurity from and refine a metal or matte product. For example, a sulfur to silicon sulfide ratio in the gas phase can be controlled to separate or strip silicon from and refine the a metal or matte product, and / or a sulfur to phosphorous sulfide ratio in the gas phase can be controlled to separate or strip phosphorous from and refine the metal or matte product. In some examples, a sulfur to magnesium sulfide ratio in the gas phase can be controlled to strip or separate magnesium from and refine the metal or matte product. In some embodiments, a sulfur to calcium sulfide ratio in the gas phase can be controlled to strip or separate calcium from and refine the metal or matte product.

[0164] Various process parameters may be utilized to target a given gas ratio or composition for thermal decomposition or impurity removal, including temperature, pressure, material flowrate, arc power (if an arc furnace) etc. The controller may leverage a proportional, proportional- integral, proportional-integral-derivative, or internal model control algorithm. More advanced control algorithms and models can be used to increase the level of control. Various observable quantities, including but not limited to compositions sampled from the furnace, process temperature, conductivity, or arc behavior (if in an arc furnace) may be used to inform the extent of thermal decomposition, impurity removal, and metal reduction during the thermal decomposition process.Example 4

[0165] Referring now to FIG. 12 and Table 1 below, nickel sulfide MSP (mixed sulfide precipitate) was either thermally decomposed or aluminothermically reduced at a temperature of 1600 C and a total pressure of 10'2atm (PS2~10‘2atm) for 15 to 60 minutes in a carbon crucible to yield a sulfur depleted or depleted metal / metal sulfide product. The bulk composition of the sulfide feedstock and the metal / metal sulfide products following thermal decomposition or aluminothermic reduction are reported in Table 1, as quantified via ICP analysis and LECO combustion analysis. In FIG. 12, the ratios of nickel to various impurities are plotted for the feedstock and the product from the thermal decomposition.Table 1. Nickel Sulfide Mixed Sulfide Precipitate (Ni MSP) composition before and after thermal decomposition or aluminothermic reduction.<< <<<< << <<

[0166] Through thermal decomposition, sulfur was depleted in the system and constituted the bulk of the impurity removal. Zinc, silicon, magnesium and calcium impurities were also depleted, as shown by the increasing nickel to impurity ratios following thermal decomposition. Due to the still fairly high ?s2in the system (PS2~10‘2atm), these impurities were removed as volatile sulfides, leaving a purified, nickel enriched matte product. The nickel to phosphorous ratio is shown to remain approximately constant.

[0167] This is due to the already low phosphorous content in the system. For the amount of phosphorous in the system and the amount of sulfur removed, the phosphorous capacity of the gas phase was not high enough to deplete phosphorous from the metal / metal sulfide product. Additional phosphorous impurities in the system may have been introduced from the carbon crucible.

[0168] Silicon and phosphorous contents were lower in the metal / metal sulfide product from thermal decomposition than the metal / metal sulfide product from aluminothermic reduction. Depending on the purity of the aluminum reductant source, additional silicon and phosphorous impurities may be introduced during reduction with the reductant. Aluminum's affinity for these and other impurities suggests that they are likely to remain along with excess aluminum impurities in the metal product. The results indicate that for management of some impurities such as silicon or phosphorus in nickel sulfide systems, a reduction approach based on direct thermal decomposition according to the present teachings is more effective than aluminothermic reduction. Aluminothermic reduction also leads to substantially higher aluminum contamination in the final product vs direct thermal decomposition.

[0169] While the present teachings have been described above in terms of specific embodiments, it is to be understood that they are not limited to these disclosed embodiments. Many modifications and other embodiments will come to mind to those skilled in the art to which this pertains, and which are intended to be and are covered by both this disclosure and the appended claims. It is intended that the scope of the present teachings should be determined by proper interpretation and construction of the appended claims and their legal equivalents, as understood by those of skill in the art relying upon the disclosure in this

[0170] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0171] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention.

[0172] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality.REFERENCE SIGNS LIST100, 200, 300, 400, 500 material processing system102 first chamber104 first chamber atmosphere106, 206, 306 molten matte or metal110 conduit116, 216 extracted gas119, 219 chute or hopper122 tapping hole202 second chamber204 second chamber atmosphere206, 306 depleted molten matte218 outlet conduit302 third chamber316 gaseous product321 condensed product

Claims

CLAIMS:

1. A system for processing sulfides, comprising:- a first chamber configured to generate, preheat, premelt, and / or melt a sulfide;and- a second chamber configured to thermally decompose at least part of the sulfide to generate a sulfur containing gas.

2. The system of claim 1, wherein the first chamber and the second chamber are positioned inside of the same furnace, reactor or converter.

3. The system of claim 1 or 2, wherein the second chamber is positioned within the first chamber.

4. The system of claim 1, wherein the second chamber is positioned outside of the first chamber.

5. The system of any one of the preceding claims, wherein the sulfide is a sulfide of a metal, and the second chamber is configured to thermally decompose the sulfide of the metal to generate the sulfur containing gas.

6. The system of claim 5, wherein the metal comprises chromium, nickel, cobalt, silicon, magnesium, calcium, iron, molybdenum, vanadium, titanium, tungsten, niobium, or tantalum.

7. The system of any one of the preceding claims, wherein the sulfide comprises a nonmetallic or metalloid element.

8. The system of any one of the preceding claims, wherein the sulfur containing gas comprises lithium, sodium, potassium, magnesium, calcium, boron, silicon, zinc, tin, nitrogen, phosphorous, arsenic, antimony, selenium, tellurium, fluorine, chlorine, or carbon.

9. The system of any one of the preceding claims, wherein the sulfide comprises a metallic, metalloid, sulfosalt, or nonmetallic impurity, wherein the sulfur containing gas is configured to strip or separate at least a portion of the metallic, metalloid, or nonmetallic impurity from the sulfide to form a sulfur containing gaseous compound of the impurity.

10. The system of any one of the preceding claims, wherein the sulfide comprises silicon sulfide, wherein a ratio of sulfur containing gas to the silicon sulfide is controlled to separate silicon from the silicon sulfide.

11. The system of any one of the preceding claims, wherein the sulfide comprises phosphorus sulfide, wherein a ratio of sulfur containing gas to the phosphorous sulfide is controlled to separate phosphorous from the phosphorus sulfide.

12. The system of any one of the preceding claims, wherein the sulfide comprises magnesium sulfide, wherein a ratio of sulfur containing gas to the magnesium sulfide is controlled to separate magnesium from the magnesium sulfide.

13. The system of any one of the preceding claims, wherein the sulfide comprises calcium sulfide, wherein a ratio of sulfur containing gas to the calcium sulfide is controlled to separate calcium from the calcium sulfide.

14. The system of any one of the preceding claims, further comprising a third chamber configured to react the sulfur containing gas with a metal to form an alloy and recover sulfur.

15. The system of claim 14, wherein the alloy and sulfur are free from aluminum contamination.

16. The system of any one of the preceding claims 14-1,5 wherein the first chamber, the second chamber and or the third chamber comprises an arc furnace, an induction furnace, an electron beam furnace, a rotary kiln, a shaft furnace, a multihearth furnace, a fluidized bed reactor, a flash smelter, an electroslag refiner, a vacuum arc remelter, or a converter.

17. The system of any one of the preceding claims, wherein the first chamber, the second chamber and / or the third chamber is configured to generate a sulfur deficient metal compound or alloy in addition to the sulfur containing gas.

18. The system of any one of the preceding claims, wherein the sulfide is thermally decomposed under vacuum pressure.

19. The system of any one of the preceding claims, wherein the sulfide is thermally decomposed under approximately ambient pressure.

20. The system of any one of the preceding claims, wherein the second chamber is configured to perform metallothermic reduction.

21. The system of any one of the preceding claims, wherein the second chamber is configured to introduce a metal to serve as a reductant, such that the sulfur containing gas is extracted through reduction.

22. The system of any one of the preceding claims, further comprising:- a first conduit connected between the first chamber and the second chamber and configured to transfer the sulfide from the first chamber to the second chamber using vacuum pressure; and- a second conduit connected to the second chamber and configured to transfer the sulfur containing gas from the second chamber.

23. The system of claim 22, wherein the second conduit is configured to condense sulfur, aluminum sulfide, magnesium sulfide, silicon sulfide, calcium sulfide, boron sulfide, aluminum oxide, magnesium oxide, silicon oxide, calcium oxide, boron oxide, a ferroalloy, or an aluminum alloy.

24. The system of claim 22 or 23, wherein the second conduit is configured to oxidize sulfur a sulfide or sulfosalt of aluminum, silicon, magnesium, calcium, strontium, barium, molybdenum, tungsten, phosphorous, arsenic, antimony, selenium, or tellurium.

25. The system of any one of the preceding claims 22-24, wherein the second conduit or the second chamber is configured to separate sulfur, a ferroalloy, an aluminum alloy, or oxides, oxysulfides, sulfides, sulfates, sulfosalts, carbonates, or carbides of aluminum, silicon, magnesium, calcium, strontium, barium, molybdenum, tungsten, zinc, phosphorous, arsenic, antimony, selenium, and / or tellurium from one another via condensation, distillation, magnetic separation, or electrostatic separation.

26. The system of any one of the preceding claims 22-25, wherein the second chamber is further configured to generate a metal or a sulfur depleted matte.

27. The system of claim 26, wherein the system further comprises the third chamber, wherein the second conduit is configured to transfer the metal or the sulfur depleted matte to the third chamber.

28. The system of any one of the preceding claims 14-27, wherein the first chamber is configured to perform sulfidation and the third chamber is configured to perform refining.

29. The system of any one of the preceding claims, wherein the second chamber is configured to produce a metal alloy.

30. The system of any one of the preceding claims 22-29, wherein the first and / or second conduit comprises a snorkel, a tube or a pipe.

31. The system of any one of the preceding claims 1 to 29, wherein the system comprises a bell-shaped reactor or conduit.

32. A method of processing sulfides, comprising:- generating, preheating, premelting, and / or melting a sulfide in a first chamber; and- thermally decomposing at least part of the sulfide to generate a sulfur containing gas in a second chamber.

33. The method of claim 32, further comprising transferring the sulfide from the first chamber to the second chamber via a first conduit.

34. The method of claim 33, further comprising:- transferring the thermally decomposed sulfide from the second chamber to a third chamber via the second conduit.

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