System and method for processing materials

Abstract

According to an example aspect, there is provided a system for processing materials, comprising: one or more sulfidation chambers configured to maintain a high operating temperature and hold a metal oxide mixture in a molten form; and one or more sulfidizing agent sources connected to the sulfidation chamber(s) and configured to introduce one or more solid, liquid, or gaseous sulfidizing agents to the sulfidation chamber(s), wherein the sulfidizing agent(s) is / are configured to react with at least a portion of the molten metal oxide mixture to form a metal sulfide mixture in a molten form, wherein the molten metal sulfide mixture is separated from any remaining molten metal oxide mixture in the sulfidation chamber(s).

Description

SYSTEM AND METHOD FOR PROCESSING MATERIALSFIELD

[0001] The present teachings relate generally to processing materials and, more particularly to sulfidation of a molten metal oxide mixture and reduction of a molten metal sulfide mixture.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. This may use a series of operations often including 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. After a target metal or mineral compound has been at least partially enriched, it generally goes through a series of steps often including smelting, reduction, and / or refining operations to produce a final metal or alloy product.

[0004] 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 may be separated from one another via density. Excess process heat can be utilized to melt scrap metals and recycle them for remanufacture. While smelting furtherenriches 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.

[0005] 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 a reduction pathway and reducing agent are made based on chemical, engineering, and operational considerations. 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.

[0006] 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. Non-carbon reductants may also be employed, including but not limited to 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.

[0007] Reduction of a compound without a reducing agent may be achieved in some instances via thermal decomposition or electrochemical decomposition as a result of 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.

[0008] Once a crude metal product has been reduced, it may require further refining to meet market or subsequent processing specifications. Following reduction, excess reductants (e.g. carbon, aluminum, silicon, etc.) or feedstock impurities (e.g. sulfur, silicon, iron, phosphorous, etc.) may still be present in the crude metal. These impurities may be removed via a variety of processing options, including but not limited to molten statepyrometallurgy with gasses, reductants, or slags, molten state electrometallurgy, aqueous electrometallurgy, distillation, and / or controlled solidification.

[0009] Known systems and methods for metal extraction from mineral ores via beneficiation, smelting, reduction, and refining suffer from issues pertaining to pollution, energy use, and difficulty in recovering certain metals such as chromium. These known systems and methods are limited in their ability to accommodate new mineral feedstocks from lower grade or chemically complex ore streams. Furthermore, increased utilization of recycled materials and scrap introduces new process contaminants to the system, which often necessitates changes to impurity separation and refining operations. Environmental sustainability concerns drive metals processing and business operations to face these chemical and engineering challenges. Therefore, technical solutions that decrease energy usage, emissions, and pollution arising from impurity management are critical as well as systems which improve metal recovery.

[0010] 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 alloys to be reduced to metals with lower direct greenhouse gas emissions. 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.

[0011] Additionally, oxides within a feedstock can be difficult to separate from one another, motivating the use of alternative processing chemistries. Sulfidation can be used to separate oxides by selectively converting them to sulfides. Sulfidation of oxides was previously envisioned to occur in certain machines, such as rotary kilns, fluidized beds, multihearth furnaces, shaft furnaces, and converters. However, mixed phase sulfidation (i.e. both solid and liquid) hinders mass transport and the use of such machines. There is a need to improve metal recovery from the sulfidation process.

[0012] Sulfidation of a solid feedstock utilizing a gaseous element restricts the maximum feedstock particle size which a system can process. Systems that require a smaller feedstock particle size require more energy consumption and cost to grind feedstocks in preparation for processing. The sulfidation reaction must propagate throughout the entirefeedstock particle to be effective. In some instances, the product that results from sulfidation may have a lower melting point than the oxide. This can result in the sulfide product produced from the sulfidation reaction becoming a liquid which may reduce movement of any unreacted solid feedstock in the furnace or reactor and result in gas flow and mass transport limitations.

[0013] Therefore, it would be beneficial to develop systems and / or methods to melt and sulfidize metal oxide mixtures and systems and / or methods for sulfide reduction processes.SUMMARY

[0014] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0015] According to a first aspect, there is provided a system for processing materials, comprising:- one or more sulfidation chambers configured to maintain a high operating temperature and hold a metal oxide mixture in a molten form; and- one or more sulfidizing agent sources connected to the sulfidation chamber(s) and configured to introduce one or more solid, liquid, or gaseous sulfidizing agents to the sulfidation chamber(s), wherein the sulfidizing agent(s) is / are configured to react with at least a portion of the molten metal oxide mixture to form a metal sulfide mixture in a molten form, wherein the molten metal sulfide mixture is separated from any remaining molten metal oxide mixture in the sulfidation chamber(s).

[0016] According to a second aspect, there is provided a method for processing materials, comprising:- inputting a metal oxide mixture to one or more sulfidation chambers configured to maintain a high operating temperature, to form the molten metal oxide mixture; and- introducing one or more solid, liquid, or gaseous sulfidizing agents to the sulfidation chamber(s) by one or more sulfidizing agent sources connected to the sulfidation chamber(s), wherein the sulfidizing agent(s) is / are configured to react with at least a portion of the molten metal oxide mixture to form a metal sulfide mixture in a moltenform; wherein the molten metal sulfide mixture is separated from any remaining molten metal oxide mixture in the sulfidation chamber(s).BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a schematic diagram of sulfidation in a sulfidation chamber being an arc furnace, in accordance with at least some embodiments;

[0018] FIG. 2 is a schematic diagram of sulfidation in a sulfidation chamber being an arc furnace with multiple electrodes, in accordance with at least some embodiments;

[0019] FIG. 3a is a schematic diagram of sulfidation in a sulfidation chamber being an induction furnace in accordance with at least some embodiments;

[0020] FIG. 3b is a schematic diagram of sulfidation in a sulfidation chamber being a resistive furnace in accordance with at least some embodiments;

[0021] FIG. 4 is a schematic diagram of sulfidation in sulfidation chamber being a flash smelter in accordance with at least some embodiments;

[0022] FIG. 5 is a schematic diagram of sulfidation in a flash smelter of another embodiment in accordance with at least some embodiments;

[0023] FIG. 6 is a schematic diagram of sulfidation in a sulfidation chamber being a blast furnace in accordance with at least some embodiments;

[0024] FIG. 7 is a schematic diagram of sulfidation in a sulfidation chamber being a converter in accordance with at least some embodiments;

[0025] FIG. 8 is a block diagram of a sulfidation and reduction process in accordance with at least some embodiments;

[0026] FIG. 9 is a schematic view of a material processing system in accordance with at least some embodiments;

[0027] FIG. 10 is a schematic view of a material processing system in accordance with at least some embodiments;

[0028] FIG. 11 is a schematic view of a material processing system in accordance with at least some embodiments;

[0029] FIG. 12 is a flowchart showing a process of feedstock being sulfidized in accordance with at least some embodiments;

[0030] FIG. 13 is a flowchart showing a process of feedstock being sulfidized and reduced in accordance with at least some embodiments;

[0031] FIG. 14 is a block diagram of a controller for a material processing system in accordance with at least some embodiments;

[0032] FIG. 15a is a scanning electron microscope image of a sulfidized chromite from a solid-gas sulfidation environment;

[0033] FIG. 15b is a scanning electron microscope image of chromium content from a solid-gas sulfidation environment;

[0034] FIG. 15c is a scanning electron microscope image of sulfur content from a solid-gas sulfidation environment;

[0035] FIG. 15d is a scanning electron microscope image of a sulfidized chromite from a liquid-gas sulfidation environment in accordance with at least some embodiments;

[0036] FIG. 15e is a scanning electron microscope image of chromium content from a liquid-gas sulfidation environment in accordance with at least some embodiments;

[0037] FIG. 15f is a scanning electron microscope image of sulfur content from a liquid-gas sulfidation environment in accordance with at least some embodiments;

[0038] FIG. 16 is an image depicting phase separation of mixed metal oxide, metal sulfide, and metal alloy following upon molten state sulfidation in accordance with at least some embodiments;

[0039] FIG. 17 is an image depicting phase separation of mixed metal oxide and metal sulfide following upon melting in accordance with at least some embodiments;

[0040] FIG. 18 is an image depicting phase separation of matte and slag phases following sulfidation of picking sludge with different oxide additives in accordance with at least some embodiments;

[0041] FIG. 19 is an image depicting phase separation of matte and slag phases following sulfidation of picking sludge with different sulfide additives in accordance with at least some embodiments; and

[0042] FIG. 20 is an image depicting phase separation of matte and slag phases following sulfidation of picking sludge with different oxide additives in accordance with at least some embodiments.DETAILED DESCRIPTIONDefinitions

[0043] In compliance with the statute, the present teachings have been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the present teachings are not limited to the specific features shown and described, since the systems and methods herein disclosed comprise preferred forms of putting the present teachings into effect.

[0044] For purposes of explanation and not limitation, specific details are set forth such as particular architectures, interfaces, techniques, etc. in order to provide a thorough understanding. In other instances, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description with unnecessary detail.

[0045] 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.

[0046] In the present context, the term “molten” means that a metal oxide mixture or metal sulfide mixture can be at least partially molten, i.e., in a semi-liquid or liquid form. The molten metal oxide mixture or the molten metal sulfide mixture may be mushy or may have two phases, namely solid and liquid phases.

[0047] 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.

[0048] 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.Embodiments

[0049] Oxides can be difficult to separate from one another, motivating the use of alternative processing chemistries. Sulfidation can be used to separate oxides by selectively converting them to sulfides. Sulfidation of oxides was previously envisioned to occur in certain machines, such as rotary kilns, fluidized beds, multihearth furnaces, shaft furnaces, and converters. However, mixed phase sulfidation (i.e. both solid and liquid) hinders mass transport and the use of such machines. In addition, the operating temperature of such machines is maintained either directly through the use of a flame or reaction exothermicity, or indirectly through resistive heating elements, thermal radiation, or combustion. When reaction exothermicity or indirect heating is utilized, the upper bound reaction temperature is limited. When a flame is used, the presence of carbon, hydrogen, oxygen, or other gases can limit sulfidation selectivity. An object of the present invention is thus to mitigate at least some of the above-mentioned problems.

[0050] According to an aspect, there is provided a system for processing materials, comprising:- a one or more sulfidation chambers configured to maintain a high operating temperature and hold a metal oxide mixture in a molten form; and- one or more sulfidizing agent sources connected to the sulfidation chamber(s) and configured to introduce one or more solid, liquid, or gaseous sulfidizing agents to the sulfidation chamber(s), wherein the sulfidizing agent(s) is / are configured to react with at least a portion of the molten metal oxide mixture to form a metal sulfide mixture in a molten form, wherein the molten metal sulfide mixture is separated from any remaining molten metal oxide mixture in the sulfidation chamber(s).

[0051] Sulfidation can be conducted in one or more sulfidation chambers. According to an embodiment, the sulfidation chamber(s) may comprise a furnace, a reactor and / or a converter, such as an AC arc furnace, a DC arc furnace, a submerged arc furnace, a rotary kiln, a multihearth furnace, a fluidized bed reactor, a flash smelter, an electroslag refiner, a vacuum arc remelter, an induction furnace, a shaft furnace, a converter, a vacuum arc furnace, or a vacuum converter.

[0052] In some examples, an oxide feedstock may be inserted into the sulfidation chamber(s), which is / are configured to melt the oxide feedstock into the molten metal oxide in preparation for sulfidation.

[0053] In some examples, the oxide feedstock may be melted prior to addition into the sulfidation chamber(s).

[0054] In some examples, the system contains a plurality of sulfidation chambers which are each separate furnaces connected by piping. In some examples, a larger system is split into sulfidation chamber portions, each operating like a separate furnace. The sulfidation chamber portions may be separated by structures such as partition walls or dams.

[0055] In an example, sulfidation can be conducted in an electric arc furnace. In this way, mixed phase sulfidation can be handled, higher maximum operating temperatures achieved, and with the reduced presence of combustion gases, although not limited thereto. An arc furnace approach provides increased versatility, for example, enabling multiple sulfidation or sulfidation- reduction-refining to be coupled into a single arc furnace with multiple electrode sets and / or sequential arc furnaces within a single process block.

[0056] In an example, sulfidation of a liquid slag or blacktop above a liquid slag is conducted in an electric arc or submerged electric arc furnace.

[0057] The chamber may contain a heat source capable of raising the internal environment to a temperature for melting the desired oxide feedstock and maintaining the resulting liquid oxide mixture as molten. In some examples, this is achieved by maintaining a melt processing environment with a temperature between 1000 and 3000 °C and a pressure between 0.001 and 1000 atm. Typically a melt processing environment with a temperature between 1300 and 2500 °C and a pressure between 0.1 and 2 atm would generally be preferred.

[0058] In examples that utilize arc furnaces, the heat source may be an electrode. Some embodiments that utilize arc furnaces may contain multiple electrodes, such as 1 to 15 electrodes, which may be placed in series, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or more, and each of one or more chambers (in a single arc furnace or different arc furnaces) may each have its own series of electrodes.

[0059] In some examples, the one or more sulfidation chamber(s) may contain a vacuum chamber or an additional vacuum unit.

[0060] According to an embodiment, the sulfidizing agent(s) are selected from the group of sulfur containing species, such as elemental sulfur, hydrogen sulfide, carbon disulfide, carbonyl sulfide, and a metal sulfide compound, and combinations thereof.

[0061] Once the oxide feedstocks are melted into a molten oxide mixture and contained within the sulfidation chamber(s), the molten oxide mixture can be contacted by the sulfidizing agent(s) to form a molten metal sulfide mixture.

[0062] In some examples, the sulfidizing agent may be introduced through one or more sulfidizing agent inlets, such as at least one of a tuyere, a taphole, a hollow electrode, a lance, a packed wire, tube or hose, a lance, a thermal decomposition or melting of a metal sulfide or metallothermic reduction of a metal sulfide.

[0063] In some examples, the sulfidation chamber(s) may also contain one or more tapholes in different locations and heights of the sulfidation chamber(s) for introduction or removal of the sulfidizing agent.

[0064] In some examples, the taphole(s) may be equipped with slide gates or stopper rods for starting and stopping the tapping and to control the tapping flow from the sulfidation chamber(s). In some examples, the slide gates may be used to control a material flowrate and / or mixing dynamics for single or multiphase flow during tapping or casting of materials from tapholes.

[0065] In some examples, the sulfidation chamber(s) may also be equipped with a tilting mechanism to control which molten phase layer is removed via the taphole(s) or the chamber inlet(s).

[0066] In some examples, the sulfidizing agent can also be introduced into the sulfidation chamber(s) through a lance or packed within a wire that is fed inside the furnace.The shell or casing of the wire can be made of aluminum, nickel or other metal, or from other compounds which provide suitable flexibility needed to feed the wire into the sulfidation chamber(s).

[0067] Wire core composition can be designed to improve the selectivity or aggressiveness of the sulfidation. For a plastic, rubber, acrylic, epoxy, or organic wire casing, the thickness and composition of the casing can be used to add hydrogen or carbon species to the sulfidation chamber(s) in a predetermined hydrogen to sulfur or carbon to sulfur ratio. Wires can be used for quick control of sulfidizing agent feed amount for improved process control. Wires can be also used to feed other feed materials and compounds to control viscosity, conductivity, composition or other parameters of the phases within the furnace.

[0068] According to an embodiment, wherein the sulfidizing agent inlet(s) is / are configured to adjust a flowrate and a temperature of the sulfidizing agent(s) to at least partially control wear of a freeze lining adjacent the sulfidizing agent inlet(s).

[0069] According to an embodiment, wherein the sulfidizing agent inlet(s) is / are configured to adjust the flowrate and the temperature of the sulfidizing agent(s) to at least partially control a bubble size in the molten metal oxide mixture, the molten metal sulfide mixture and / or foam on their surface resulting from sulfidizing agent(s) introduced into the sulfidation chamber(s).

[0070] According to an embodiment, the sulfidizing agent inlet(s) is / are configured to control a ratio of solids to liquids to gases for controlling a bubble size in the molten metal oxide mixture, the molten metal sulfide mixture and / or foam on their surface resulting from sulfidizing agent(s) introduced into the sulfidation chamber(s).

[0071] According to an embodiment, the control comprises reducing the bubble size in the molten metal oxide mixture, the molten metal sulfide mixture and / or foam on their surface and / or making it uniform. Bubble sizes between 0.1 mm and 100 mm are generally preferred.

[0072] According to an embodiment, the sulfidizing agent(s) is / are generated within the sulfidation chamber(s) through thermal decomposition, hydrogen reduction, or metallothermic reduction of a metal sulfide.

[0073] According to an embodiment, the chamber inlet(s) is / are configured to add a bulk liquid mixture to the sulfidation chamber(s) to collect the molten metal sulfide mixture; wherein the bulk liquid mixture comprises a least one of a sulfide, halide, or liquid alloy, or any combination thereof.

[0074] Factors such as immiscibility and phase density of the molten metal sulfide and molten metal oxides cause the phases to separate after sulfidation occurs, allowing one to remove a desired liquid mixture from the sulfidation chamber(s). The rate and quality of separation may be controlled through parameters such as surface tension, viscosity, and density. These parameters of both the oxide and sulfide mixtures may be adjusted by introducing additives into the sulfidation chamber(s). These additives include, but are not limited to, metal oxides, metal sulfides, metal halides, or a combination thereof.

[0075] According to an embodiment, the sulfidation chamber(s) comprise(s) one or more chamber inlets configured to feed an oxide feedstock to the sulfidation chamber(s) to form the molten metal oxide mixture; wherein the oxide feedstock comprises one or more feedstock metals selected from the group of iron, nickel, chromium, molybdenum, cobalt, silicon, aluminum, magnesium, calcium, titanium, copper, rare earth metals, vanadium, and manganese.

[0076] According to an embodiment, an oxide additive is added to the sulfidation chamber(s) to adjust viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and / or melting point of the molten metal oxide mixture.

[0077] According to an embodiment, the chamber inlet(s) is / are further configured to add one or more sulfide additives into the sulfidation chamber(s) to adjust viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and / or melting point of the molten metal sulfide mixture.

[0078] According to an embodiment, the chamber inlet(s) is / are further configured to add one or more halides containing feedstock to the sulfidation chamber(s) to adjust viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and / or melting point of either the molten metal oxide or the molten metal sulfide mixture.

[0079] In some examples, additives can be used to adjust the selectivity of the sulfidation reaction within the sulfidation chamber(s). The viscosity of the liquid oxide bath, the basicity of the oxide bath, inlet gases flowrates, sulfur to sulfur dioxide ratio, sulfurbubble size, dissolved sulfur gas content, and bubble residence time in the molten metal oxide mixture, the molten metal sulfide mixture and / or foam on their surface are all parameters that affect the selectivity of the sulfidation reaction.

[0080] In some examples where halide additives are included, the potential sulfurhalide compound emissions are lower than when sulfidation of a diluted or fluxed oxide is conducted in a liquid halide bath or solvent.

[0081] According to an embodiment, the molten metal oxide mixture comprises feedstock containing metal to be recycled.

[0082] According to an embodiment, the sulfidation chamber(s) further comprise(s) one or more reducing agent inlet(s) for introducing reducing agent into the sulfidation chamber(s), to subject the molten metal sulfide mixture a reduction refining reaction.

[0083] According to an embodiment, the system further comprises one or more reduction chambers containing a reducing agent and configured to maintain a high operating temperature. In other examples, the reduction chamber can be an electrolytic cell that uses electricity instead of a reducing agent.

[0084] According to an embodiment, the reducing agent can be selected from the group of aluminum, silicon, silicon carbide, magnesium, calcium, calcium carbide, iron, chromium, oxygen, sulfur dioxide, hydrogen, coal, coke, and biomass, and mixtures thereof.

[0085] According to an embodiment, the molten metal sulfide mixture is transferred from the sulfidation chamber(s) to the reduction chamber(s) in a molten or semi molten state, wherein the molten metal sulfide mixture entering the reduction chamber(s) is subject to a reduction refining reaction.

[0086] According to an embodiment, the system further comprises a transferring system and / or a launder configured to transfer the molten metal sulfide or oxide mixture between the sulfidation chambers, between the reduction chambers or from the sulfidation chamber(s) to the reduction chamber(s) without exposure to ambient conditions.

[0087] According to an embodiment, the molten metal sulfide mixture is removed from the sulfidation chamber(s) and cooled to form a solid metal sulfide mixture, which is crushed and transferred to the reduction chamber(s). Optionally solid metal sulfide mixture can be further comminuted and processed to at least separate a portion of one of the sulfidephases and / or impurity oxide phases present in the solid metal sulfide mixture prior transferring it to reduction chamber(s).

[0088] According to an embodiment, the sulfidation chamber(s) and the reduction chamber(s) is / are positioned sequentially in a single furnace, reactor or converter.

[0089] According to an embodiment, the sulfidation chamber(s) is / are positioned in a first furnace, reactor or converter and the reduction chamber(s) is / are positioned in a second furnace, reactor or converter, wherein the first furnace, reactor or converter and the second furnace, reactor or converter are positioned sequentially.

[0090] According to an embodiment, the first furnace, reactor or converter, and the second furnace, reactor or converter, are configured to conduct the sulfidation and the reduction sequentially and / or parallel.

[0091] In some examples, the molten metal sulfide mixture can be introduced into a first sulfidation chamber to react with at least a portion of the molten metal oxide mixture. Once sulfidation of the molten metal oxide mixture in the first sulfidation chamber is at least partially complete, any remaining molten metal oxide mixture can be transferred to a second sulfidation chamber, wherein the remaining molten metal oxide mixture can undergo another round of sulfidation before being removed from the second sulfidation chamber. The process can be repeated for several times.

[0092] According to an embodiment, the system comprises two or more sulfidation chambers, wherein the molten metal oxide mixture is configured to be transferred from a first sulfidation chamber and / or the reduction chamber to a second sulfidation chamber, and optionally from the second sulfidation chamber to a third sulfidation chamber.

[0093] According to an embodiment, the liquid metal sulfide mixture is configured to be removed from the first sulfidation chamber and / or the second sulfidation chamber before the transferring of the molten metal oxide mixture.

[0094] According to an embodiment, the high operation temperature of the sulfidation chamber(s) is at least 80 % of a melting temperature of the metal oxide mixture, for example 1000-3000 °C, such as 1300-2500 °C.

[0095] According to an embodiment, the high operation temperature of the reduction chamber(s) is at least 80 % of a melting temperature of the metal sulfide mixture.

[0096] In some examples, various partitioning designs between the first, second and / or third sulfidation chamber may be utilized, including tap-based or walls for liquid to flow over or under into a subsequent sulfidation chamber.

[0097] In some examples, the first, second and / or third sulfidation chamber can be equipped with one or more tilting mechanisms to facilitate the flow of the molten metal sulfide mixture between the sulfidation chambers and from the sulfidation chamber(s) into the reduction chamber(s) for subsequent processing via a mouth, launder, or tube.

[0098] In some examples, 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. magnesiochrom ite, calciochrom ite, 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, doloma, silica, zirconia, hafnia, yttria, rare earth oxides, etc.).

[0099] In some examples, arc furnaces can be connected sequentially to conduct multiple sulfidations or sulfidation-reduction-refining operations on materials to avoid cooling the materials, e.g., to room temperature. Having multiple arc furnaces connected together can reduce the need for furnace tapping and ladle transport and minimize molten sulfide exposure to ambient conditions, although not limited thereto. The furnaces may be slanted to enable gravimetric transfer of materials between processing steps. In some examples, a tilting mechanism may be used to allow at least a portion of a molten pool to be transferred from one chamber or chamber portion to another.

[0100] The various embodiments, examples and variants disclosed here in connection with the system apply mutatis mutandis to the method.

[0101] A method for processing materials, comprising:- inputting a metal oxide mixture to one or more sulfidation chambers configured to maintain a high operating temperature, to form the molten metal oxide mixture; and- introducing one or more solid, liquid, or gaseous sulfidizing agents to the sulfidation chamber(s) by one or more sulfidizing agent sources connected to the sulfidation chamber(s), wherein the sulfidizing agent(s) is / are configured to react with at least a portion of the molten metal oxide mixture to form a metal sulfide mixture in a molten form; wherein the molten metal sulfide mixture is separated from any remaining molten metal oxide mixture in the sulfidation chamber(s).

[0102] According to an embodiment, the method comprises feeding oxide feedstock to the sulfidation chamber(s) via one or more chamber inlets to form the molten metal oxide mixture.

[0103] According to an embodiment, the method comprises adding an oxide additive to the sulfidation chamber(s) to adjust viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and / or melting point of the molten metal oxide mixture.

[0104] According to an embodiment, the method comprises adding one or more sulfides into the sulfidation chamber(s) via the chamber inlet(s), to adjust viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and / or melting point of the molten metal sulfide mixture.

[0105] According to an embodiment, the method comprises adding one or more halides containing feedstock to the sulfidation chamber(s) via the chamber inlet(s), to adjust viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and / or melting point of the molten metal oxide or the molten metal sulfide mixture.

[0106] According to an embodiment, the method comprises adjusting the flowrate and the temperature of the sulfidizing agent(s) by sulfidizing agent inlet(s) connected to sulfidizing agent source(s), to at least partially control a bubble size in the molten metal oxide mixture, the molten metal sulfide mixture and / or foam on their surface resulting from the sulfidizing agent(s) introduced into the sulfidation chamber(s), or to control a ratio of solids to liquids to gases for controlling a bubble size in the molten metal oxide mixture, the molten metal sulfide mixture and / or foam on their surface resulting from the sulfidizing agent(s) introduced into the sulfidation chamber(s).

[0107] According to an embodiment, the method comprises adding a bulk liquid mixture to the sulfidation chamber(s) via the chamber inlet(s), to collect the molten metal sulfide mixture.

[0108] According to an embodiment, the method comprises introducing reducing agent into the sulfidation chamber(s) via one or more reducing agent inlet(s) connected to the sulfidation chamber(s), to subject the molten metal sulfide mixture a reduction refining reaction.

[0109] According to an embodiment, the method comprises transferring the molten metal sulfide mixture from the sulfidation chamber(s) to one or more reduction chamber(s) in a molten or semi-molten state, wherein the molten metal sulfide mixture entering the reduction chamber(s) is subjected to a reduction refining reaction.

[0110] According to an embodiment, the transferring is conducted by a transferring system and / or a launder.

[0111] According to an embodiment, the method comprises:- removing the molten metal sulfide mixture from the from the sulfidation chamber(s);- cooling the molten metal sulfide mixture to form a solid metal sulfide mixture; and- crushing the solid metal sulfide mixture; and- optionally comminuting and at least separating a portion of one of sulfide phases and / or impurity oxide phases present in the solid metal sulfide mixture; and- transferring the solid metal sulfide mixture to one or more reduction chamber(s).

[0112] According to an embodiment, the method comprises transferring the molten metal oxide mixture from a first sulfidation chamber and / or a reduction chamber to a second sulfidation chamber, and optionally from the second sulfidation chamber to a third sulfidation chamber.

[0113] According to an embodiment, the method comprises removing the liquid metal sulfide mixture from the first sulfidation chamber and / or the second sulfidation chamber before the transferring of the molten metal oxide mixture.DETAILED DESCRIPTION OF THE DRAWINGS

[0114] 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.

[0115] 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.

[0116] Referring now to FIG. 1, shown is a schematic diagram of sulfidation in a sulfidation chamber 100 being an arc furnace. In other examples, the sulfidation chamber 100 may consist of, but is not limited to, an induction furnace or a resistively heated furnace. The sulfidation chamber 100 is built to establish and maintain a molten processing environment which may melt any oxide feedstock added to the sulfidation chamber 100 in order to form a molten metal oxide mixture 110. An oxide feedstock added to the sulfidation chamber may contain, but is not limited to, metal oxide, ore, recyclable metals, or any other material containing at least one metal oxide. A sulfidizing agent may be introduced into the sulfidation chamber 100 in order to contact the liquid oxide mixture and selectively sulfidize oxides. The internal environment or processing conditions of the sulfidation chamber 100 may be adjusted and additives may be introduced to adjust the selectivity of the sulfidation process implemented in the sulfidation chamber 100.

[0117] The sulfidation chamber 100 may include a chamber inlet 114 as well as an electrode 116 that serves as a heat source for the arc furnace. The electrode 116 is utilized to maintain a melt processing environment within the sulfidation chamber 100 which keeps any oxide feedstock within the sulfidation chamber 100 in the liquid state. The structure of the sulfidation chamber 100 includes side walls 104, a roof 102, and a bottom 106.

[0118] The metal oxide feedstock may be fed into the chamber inlet(s) 114 of the sulfidation chamber 100, where the chamber inlet 114 may have a port with a shutter or valve to ensure the chamber inlet 114 is closed during operation of the sulfidation chamber 100. The chamber inlet(s) 114 may be placed at various locations within the sulfidation chamber 100, including but not limited to at the top of the furnace, above the blacktop, withinthe blacktop, within liquid layers of the sulfidation chamber 100, or a combination thereof. In some embodiments the oxide feedstock is a solid when inserted into the chamber 100. In some examples, the metal oxide feedstock is melted prior to entering the sulfidation chambers 100.

[0119] The sulfidation chamber 100 may comprise one or more chamber inlets 114. The chamber inlets may be placed at different levels. In particular, a plurality of the chamber inlets 114 may be utilized in examples wherein multiple materials are co-smelted, coprocessed, and / or co-reduced. In some examples, the chamber inlet(s) 114 may comprise a removable roof 102 or an opening located towards the top of the sulfidation chamber with no closure mechanism. In some examples, the chamber inlets 114 may include a hatch located on any of the exterior surfaces of the sulfidation chamber, where the hatch may have a lid with a closure mechanism or a cover plate which is removably fixed to the structure of the sulfidation chamber 100. In some examples, the chamber inlet(s) 114 may be always opened, always closed, or opened and closed during feeding, gas exhausting, and / or system monitoring. In some examples, the chamber inlet(s) 114 is / are (an) opening(s) used for feeding a sulfi dizing agent containing wire or a lance into the sulfidation chamber 100. In some examples, a separate gas outlet 122 is used for gas exhausting.

[0120] In some examples, during operation of the sulfidation chamber 100, a molten metal oxide mixture 110 and a molten metal sulfide mixture 112 are within the sulfidation chamber. A sulfi dizing agent may be introduced into the molten metal oxide mixture 110 through a tuyere 108 and / or chamber inlet 114 and / or through hollow electrode 116. The tuyere 108 enters the sulfidation chamber 100 through the side wall 104 and has an opening similar to a nozzle that allows for the sulfidizing agent to enter into the sulfidation chamber 100, as shown by the arrows in FIG. 1. The size of the opening on the tuyere 108 affects the size of sulfidizing agent bubbles. One or more tuyeres 108 may be present in the sulfidation chamber 100. In some examples, the size of the bubbles containing the sulfidizing agent may be controlled by the ratio of solids to liquids to gases carried into the chamber via the tuyere 108 gas stream. Bubble sizes between 0.1 mm and 100 mm are generally preferred. In some examples, the gas flowrate through one or more tuyeres 108, hollow electrodes, or lances, may be varied to control whether the bubbles from one or more multiple inlets collide, combine and grow inside the sulfidation chamber 100. In some examples, the size of sulfidizing agent bubbles may be modulated by controlling a gas flowrate and a temperature, which can determine the length of a freeze layer extending from the tuyere 108. Themorphology of the freeze layer from the tuyere 108 may control whether bubbles from the same or different tuyeres 108 remain separate or combine to form larger bubbles. Some examples may implement a blast gate to restrict flow through the tuyere 108 and control freeze lining formation extending from the tuyere 108. In some examples, the size of sulfidizing agent bubbles which are introduced into the molten metal oxide mixture 110 affects the selectivity of the sulfidation reaction.

[0121] In some examples, a sulfidation reaction occurs upon contact between the sulfidizing agent and the molten metal oxide mixture 110. This reaction produces a metal sulfide which will become a part of a layer of the molten metal sulfide mixture 112 as well as exhaust gas 120. The exhaust gas may consist of sulfur dioxide in some embodiments and exit the sulfidation chamber 100 through an outlet 122. In some examples, the temperature and gas atmosphere within the sulfidation chamber 100 may cause any sulfides or sulfates to undergo reaction or thermal decomposition and revert to an oxide.

[0122] In some examples, additives can be inserted into the sulfidation chamber 100 through the chamber inlet 114. These additives are utilized to adjust key parameters within the sulfidation chamber 100 and can adjust the selectivity of the sulfidation reaction occurring within the sulfidation chamber 100, as well as impact the separation between the molten metal oxide mixture 110 and molten metal sulfide mixture 112. In some examples, the additives are inserted into sulfidation chamber 100 as solids and melted within the sulfidation chamber. In some examples, the additives are melted prior to entry to the sulfidation chamber 100. In some examples, the additives may be added to the oxide feedstock prior to entry into the sulfidation chamber 100. In some examples, the additives may be carried into the sulfidation chamber 100 via suspension in the gas phase through a tuyere 108. The additives can be introduced to the sulfidation chamber before sulfidation, during sulfidation, after sulfidation, or a combination thereof.

[0123] In some examples, the tuyere 108 may extend down into the furnace from the roof 102 or there may be one or more tuyeres 108 positioned around the sulfidation chamber to introduce the sulfidizing agent at a few different locations. In some examples, the sulfidizing agent is delivered to the layer of the molten metal oxide mixture 110 through the electrode 116. The electrode 116 may contain an inner chamber 118 which allows the sulfidizing agent to enter the sulfidation chamber 100. In some examples, the sulfidizing agent is delivered through a top lance. In some examples, the sulfidizing agent may bedelivered via both tuyere 108, the inner chamber 118 of the electrode 116, a top lance, within a cored wire, tube, or hose, or a combination thereof.

[0124] In some examples, once sulfidation concludes, at least part of the molten metal sulfide mixture 112 may be removed from the sulfidation chamber 100 through taphole 124 and sent to another chamber for further processing. Immiscibility and phase density between the molten metal oxide mixture 110 and the molten metal sulfide mixture 112, along with viscosity, surface tension, and other parameters result in the mixtures separating. Any oxides and sulfides within the sulfidation chamber 100 may be removed simultaneously or sequentially, either through the same or separate tapholes 124, barriers, partitions, pipes, or other inlets and outlets from the sulfidation chamber.

[0125] In some examples, supplemental heating or cooling may be utilized before, within, or after transferring molten metal oxide mixture 110 and / or molten metal sulfide mixture 112 to maintain or modulate properties of the transferred molten metal sulfide mixture 112 or molten metal oxide mixture 110.

[0126] In some examples, the oxide feedstock and the molten metal sulfide mixture 112 or molten metal oxide mixture 110 may be added or removed from the sulfidation chamber 100 in batch, semibatch, or continuous manners. The batch, semibatch, and continuous addition or removal of the molten metal sulfide mixture 112 or molten metal oxide mixture 110 may be leveraged to control liquid levels and residence times in the system.

[0127] In some examples, the structure of the sulfidation chamber 100 may be covered in a refractory material. The refractory material may cover only the roof 102 while in others the refractory material may be disposed on at least the side walls 104 and the bottom 106 of the sulfidation chamber 100.

[0128] FIG. 2 illustrates a sulfidation chamber 200 being an arc furnace with multiple electrodes 216. The sulfidation chamber 200 is similar to the sulfidation chamber 100 of FIG. 1 but focuses on a variation where a plurality of electrodes 216 are utilized. Therefore, the description of the sulfidation chamber 200 of FIG. 2 will generally discuss the main differences from the sulfidation chamber 100 of FIG. 1. A plurality of the electrodes 216 may be utilized to ensure a more uniform heat distribution within the sulfidation chamber200 as well as work together to achieve and maintain a steady temperature or manage different feed particle sizes.

[0129] The illustrated example of the sulfidation chamber 200 depicts three electrodes 216 each with an inner chamber 218. In some examples, the sulfidation chamber 200 may only utilize two electrodes 216. In some examples, the sulfidation chamber 200 may include more than three electrodes.

[0130] In some examples, a sulfidizing agent is introduced into the sulfidation chamber 200 though the inner chamber 218 of the electrodes 216. In some examples, a sulfidizing agent is introduced through each of the electrodes 216. In some examples, only a select few of the electrodes 216 introduce a sulfidizing agent into the sulfidation chamber 200.

[0131] FIG. 3a illustrates a schematic diagram of sulfidation in a sulfidation chamber 300 being an induction furnace. The sulfidation chamber 300 of FIG. 3 is similar to the sulfidation chamber 100 of FIG. 1, but discloses an induction furnace instead of an arc furnace. Therefore, the description will generally discuss the main differences. The sulfidation chamber 300 being the induction furnace utilizes a coil 322 placed outside of the sulfidation chamber to generate heat. An electric current is run through the coil 322 which results in a magnetic field being induced on either the structure of the sulfidation chamber and / or the materials contained within the sulfidation chamber and / or the inner crucible or susceptor within the furnace. The impact of this magnetic field on the sulfidation chamber 300 causes a rapid rise in temperature and is responsible for maintaining a melt processing environment which keeps the molten metal oxide mixture 310 within in a molten state. Due to this construction, there is no need to have any heat sources components extend into the molten metal oxide mixture 310 being heated reducing the risk of contamination.

[0132] Elimination of the electrode from the system may decrease direct greenhouse gas emissions generated from reaction between feedstocks or products in the sulfidation chamber and graphite or carbon electrodes. Furthermore, in some examples, the electrode of an arc furnace that extends into the sulfidation chamber may interact with the chemistry, kinetics, or mass transport of a sulfidation or reduction furnace. Pressure control within the chamber (e.g., at least a partial vacuum to at least partially pressured above ambient conditions) may be easier to achieve without an electrode present.

[0133] In some examples, a sulfi dizing agent enters through a tuyere 308 into the sulfidation chamber 300. Tuyere(s) 308 can be positioned in any height of the chamber including within the region corresponding to coil 322 and in any angle including through bottom 306 to deliver sulfidizing agent into molten metal sulfide mixture 312 or molten metal oxide mixture 310. The sulfidizing agent may interact with any molten metal oxide mixture 310 contained within the sulfidation chamber 300 to selectively sulfidize a metal oxide into a metal sulfide. The metal sulfide will separate from the molten metal oxide mixture 310 and form a molten metal sulfide mixture 312. Some examples of the induction furnace include multiple tuyeres 308. In some examples, a top lance 328 extends into the induction furnace and delivers sulfidizing agent to the molten metal oxide mixture 310. In some examples, sulfidizing agent is delivered through both one and multiple tuyeres 308 as well as the top lance 328 that can be positioned to enter the chamber through chamber roof 302, side wall 304 in different angles and positions. In some examples sulfidation agent is delivered as a solid metal sulfide containing compound separately or along with other solid feedstocks.

[0134] The illustrated embodiment of FIG. 3a shows a sulfidation chamber 300 being an induction furnace having a bottom 306, roof 302, and two side walls 304, wherein a refractory lining 324 is disposed on the interior of the bottom 306 and side walls 304. In some examples, the induction furnace may be used in place of an arc furnace for the first chamber 100.

[0135] FIG. 3b is a schematic diagram of sulfidation in a sulfidation chamber 300b being a resistive furnace. The sulfidation chamber 300b of FIG. 3b is similar to the induction furnace of FIG. 3a, but discloses a resistively heated furnace instead of the induction furnace. Therefore, the description will generally discuss the main differences. The resistive furnace utilizes resistive heating elements 326b placed inside of the sulfidation chamber to generate heat and maintain a melt processing environment which keeps the molten metal oxide mixture 310b within in a molten state.

[0136] In some examples, the heating elements 326b may either be imbedded in or contained in the furnace side walls 304b refractory or in refractory regions positioned within the sulfidation chamber. In some examples, the resistive heating elements 326b may be in the form of bricks lining the side walls 304b and the bottom 306b. An electric current is run through the heating elements 326b, generating heat in the heating elements 326b which heatsthe molten metal oxide mixture contained within the sulfidation chamber 300b. Elimination of the electrode required when using an arc furnace may decrease direct greenhouse gas emissions generated from reaction between feedstocks or products in the furnace and graphite or carbon electrodes.

[0137] In some examples, the electrode of an arc furnace may interact with the chemistry, kinetics, or mass transport of a sulfidation or reduction chamber. Pressure control within the reactor (e.g., at least a partial vacuum to at least partially pressured above ambient conditions) may be easier to achieve without an electrode present. The construction of the sulfidation chamber 300b being a resistive furnace may provide better control of heating electrically conductive and insulating materials within the sulfidation chamber and improved thermal gradients over an induction furnace. Resistive heating elements 326b may also be used in conjunction with other heat sources such as an induction heating coil or electric arc in some examples. The combination of heating agents may help control thermal gradients within the sulfidation chamber or to aid in the sulfidation chamber startup, material charging and melting, or shut down, or to control freeze lining behaviors.

[0138] In some examples, a sulfi dizing agent enters through a tuyere 308b into the sulfidation chamber 300b. In some examples, the sulfi dizing agent enters through a top lance 328b. The sulfidizing agent interacts with a molten metal oxide mixture 310b to selectively sulfidize a metal oxide into a metal sulfide and separate the metal sulfide into the molten metal sulfide mixture 312b. The illustrated embodiment of FIG. 3b shows a resistive furnace with a bottom 306b, roof 302b, and two side walls 304b, wherein a refractory lining 324b is disposed on the interior of the bottom 306b and side walls 304b. In some examples, an induction furnace may be used in place of an arc furnace for the sulfidation chamber 100 or the induction furnace system.

[0139] FIG. 4 is a schematic diagram of sulfidation in sulfidation chamber 400 being a flash smelter. The sulfidation chamber 400 of FIG. 4 is similar to the sulfidation chamber 100 of FIG. 1, but discloses a flash smelter instead of a typical arc furnace. Therefore, the description will generally discuss the main differences.

[0140] The illustrated example of the sulfidation chamber 400, i.e. the flash smelter, depicts a chamber inlet 414 where oxide feedstock is added to the system, as well as any additives needed during operation. The oxide feedstock is maintained in a molten state and a sulfidizing agent is introduced into the sulfidation chamber through a tuyere 408. In someexamples, a top lance and / or electrodes 416 may be used to add sulfidizing agent to the sulfidation chamber 400. During operation, the oxide feedstock is separated into a molten metal oxide mixture 410 and molten metal sulfide mixture 412. As described above, due to a multitude of factors such as immiscibility and phase density these mixtures separate from one another naturally. Tapholes 432 located in the sulfidation chamber 400 at various heights are utilized to draw off portions of either the molten metal oxide mixture 410 or molten metal sulfide mixture 412. The sulfidation chamber may also incorporate an outlet 430 to allow any exhaust gases generated during sulfidation to exit the sulfidation chamber.

[0141] FIG. 5 is a schematic diagram of sulfidation in a flash smelter. FIG. 5 depicts a multi-furnace system 500 incorporating a flash smelter in a first sulfidation chamber portion 540 separated from an arc furnace in a second sulfidation chamber portion 550 via a dam 528. The multi-furnace system 500 is similar to the flash smelter described in FIG. 4, but discloses a flash smelter and an arc furnace. Therefore, the description will generally discuss the main differences.

[0142] The first sulfidation chamber portion 540 and second sulfidation chamber portion 550 may be, but are not limited to, an induction, resistive furnace or arc furnace. In the illustrated example, the flash furnace depicted as the first sulfidation chamber portion 540 processes a feedstock containing a sulfide that is partially oxidized. This results in molten metal oxide mixture 510 and a molten metal sulfide mixture 512. An exhaust gas such as sulfur dioxide is produced during this process and is evacuated from the chamber portions via outlets 530.

[0143] In the illustrated example, the dam 528 extends from a roof 502 and bottom 506. The dam 528 separates the furnace into the first sulfidation chamber portion 540 and the second sulfidation chamber portion 550 allowing only molten metal oxide mixture 510 to flow into second sulfidation chamber. Feedstock may be put into the system through the chamber inlet 514 positioned in the first sulfidation chamber portion 540. Electrodes 516 are positioned in the second sulfidation chamber portion 550 to apply heat to the feedstock within the second sulfidation chamber portion. During sulfidation the dam 528 may provide separation of gas atmospheres between first sulfidation chamber portion 540 and the second sulfidation chamber portion 550 and / or separation of molten metal sulfide mixtures 512 and 522. The outlet 530 is positioned at the top of each chamber portions to provide an exhaust path for any gas produced during sulfidation. In another example, the dam 528 extends fromroof 502 into the molten metal sulfide mixture 512 isolating the chamber gas atmosphere portions from each other as well as molten metal oxide mixtures allowing only molten metal sulfide mixture 512 to flow into second chamber. Chamber inlet 524 positioned in second chamber may be used to introduce same and / or different feedstock compared to chamber inlet 514 including but not limited to different metal oxide and / or metal sulfide containing compounds, sulfidation agents, reductants and / or additives.

[0144] FIG. 6 is a schematic diagram of sulfidation in a sulfidation chamber 600 being a shaft furnace with a liquid region at the bottom. The sulfidation chamber 600 of FIG. 6 is similar to the sulfidation chamber 100 of FIG. 1, but discloses a blast furnace instead of an arc furnace. Therefore, the description will generally discuss the main differences. In some examples, the sulfidation chamber 600 may be a shaft furnace.

[0145] The illustrated example of sulfidation chamber 600 has a chamber inlet 614 located along the top of the sulfidation chamber. A tuyere 608 injects a sulfidizing agent into a molten metal oxide mixture 610 to form a molten metal sulfide mixture 612. Feedstock is added to the sulfidation chamber 600 through the chamber inlet 614 and is subjected to a melt processing environment within as it flows down towards the bottom of the sulfidation chamber 600. In some examples, a solid layer 620 builds up in the sulfidation chamber 600 above the molten metal oxide mixture 610 and the molten metal sulfide mixture 612.

[0146] The batch, semibatch, and continuous addition or removal of the molten metal oxide mixture 610 and the molten metal sulfide mixture 612 may be leveraged to control liquid levels and residence times in the system.

[0147] FIG. 7 is a schematic diagram of sulfidation in a sulfidation chamber 700 being a converter. The illustrated example is similar to the sulfidation chamber 100 of FIG. 1 described above, but discloses a converter instead of an arc furnace. Therefore, the description of the sulfidation chamber 700 will generally discuss the main differences.

[0148] In the illustrated example of FIG. 7, the sulfidation chamber 700 includes a top lance 728 which extends down into the sulfidation chamber 700. Sulfidizing agent is introduced into the molten metal oxide mixture 710 through the top lance. In some examples, the sulfidizing agent is introduced into the molten metal oxide mixture 710 and / or molten metal sulfide mixture 712 via tuyere(s) 708. In other examples, the sulfidizing agent is introduced through both the top lance 728 and tuyere(s) 708.

[0149] FIG. 8 is a block diagram of a sulfidation and reduction process. FIG. 8 shows a block diagram of a multi- chamber furnace 840 comprising a sulfidation chamber 850 and a reduction chamber 870, used for processing materials such as oxide feedstock 852. In the illustrated example of FIG. 8, the multi-chamber furnace 840 is an arc furnace. In other enabling examples, the multi-chamber furnace 840 may be, but is not limited to, an induction furnace or a resistively heated furnace.

[0150] The oxide feedstock 852 is input into the sulfidation chamber 850 and may comprise metal oxide, ore, recyclable metals, or any other material containing at least one metal oxide. The sulfidation chamber 850 melts the oxide feedstock 852 and introduces a sulfidizing agent 854 (e.g., gas, solid, liquid). The internal environment or processing conditions of the sulfidation chamber 850 can be adjusted to target certain mixed metal oxides 858 and convert them to metal sulfides 860. During this process sulfur dioxide gas 856 may be generated within the system.

[0151] Remaining mixed metal oxides 858 are removed from the sulfidation chamber 850 and multi-chamber furnace 840 and may be sent to another furnace to undergo additional sulfidation or reduction. The converted metal sulfides 860 are then transferred to a reduction chamber 870. The reduction chamber 870 is able to maintain the metal sulfide 860 in a liquid state and introduces a reducing agent 872. The reducing agent 872 combines with the sulfur in the metal sulfide 860 to generally produce the desired metal or an alloy of the desired metal 878, one or more sulfur-containing gases 874, and a compound of reducing agent and sulfur 876. In other examples, remaining mixed metal oxides 858 may continue to reduction chamber 870 instead of converted metal sulfides 860 and converted metal sulfides 860 are instead removed from the multi-chamber furnace 840 and may be sent to another furnace to undergo reduction or oxidation.

[0152] 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 carbonsulfur compounds, carbonyl compounds, sulfosalts, oxysulfides, and thiophosphates.

[0153] FIG. 9 illustrates an example of a material processing system 990 consisting of a sulfidation chamber 900 connected to a reduction chamber 950 via a transfer pipe or a launder 980. The sulfidation chamber 900 and the reduction chamber 950 are separate arc furnaces connected via the transfer pipe or a launder 980. In other examples, both chambers may exist within a single arc furnace. In yet another example, the chambers may be equippedwith one or more tilting mechanisms to facilitate the flow from one chamber into another for subsequent processing via a mouth, launder, tube, or a combination thereof.

[0154] The sulfidation chamber 900 comprises a chamber inlet 914, an electrode 916 which is utilized to apply heat to a material within the sulfidation chamber and as well a gas outlet 920. The structure of the sulfidation chamber 900 consists of side walls 904, a roof 902, and a bottom 906.

[0155] Oxide feedstock is fed into the chamber inlet(s) 914 of the sulfidation chamber 900, where the chamber inlet 914 may comprise a port with a shutter or valve to ensure the chamber inlet 914 is closed during operation of the furnace. The chamber inlet(s) 914 may be placed at various locations within the sulfidation chamber, including but not limited to, at the top of the sulfidation chamber, above the blacktop, within the blacktop, within liquid layers of the first surface, or a combination thereof.

[0156] Some examples may include one or more chamber inlets 914 at different levels, in particular a plurality of chamber inlets 914 are utilized in implementing examples where multiple materials are co-smelted, co-processed, and / or co-reduced. In other examples, the inlet 914 may include a removable roof 902 or an opening located towards the top of the sulfidation chamber with no closure mechanism. In yet another example, the chamber inlet 914 may include a hatch located on any of the exterior surfaces of the sulfidation chamber, where the hatch may have a lid with a closure mechanism or a cover plate which is removably fixed to the structure of the sulfidation chamber 900. In some examples, the chamber inlet 914 may be always opened, always closed, or opened and closed during feeding, gas exhausting, and / or system monitoring. In another example, the chamber inlet 914 is used for feeding a sulfi dizing agent containing wire or a lance into the sulfidation chamber 900.

[0157] During operation of the sulfidation chamber 900 a layer of molten metal oxide mixture 910 and a layer of molten metal sulfide mixture 912 are generated within the sulfidation chamber 900. A sulfidizing agent is introduced into the molten metal oxide mixture 910 and / or into the molten sulfide mixture 912 through a tuyere(s) 908. The tuyere(s) 908 enters the sulfidation chamber through the side wall 904 and has an opening similar to a nozzle that allows for the sulfidizing agent to enter into the sulfidation chamber 900, as shown by the arrows in FIG. 9.

[0158] In other examples, the tuyere 908 may extend down into the sulfidation chamber from the roof 902 or there may be one or more tuyeres 908 positioned around the sulfidation chamber to introduce the sulfidizing agent at a few different locations. In yet another example, the sulfidizing agent is delivered to the molten metal oxide mixture 910 through the electrode 916. The electrode 916 may contain an inner chamber 918 which allows the sulfidizing agent to enter into the sulfidation chamber 900. In further alternatives, sulfidizing agent may be delivered via both tuyere 908 and inner chamber 918 of the electrode 916. In beforementioned examples, sulfidation agent(s) can also be delivered as a solid sulfide containing compound via chamber inlet 914.

[0159] Once sulfidation concludes, the desired molten metal sulfide mixture 912 can be removed from the sulfidation chamber 900 and placed in the reduction chamber 950, where a process is undertaken to reduce the metal sulfide to the desired metal. Any oxides and sulfides within the sulfidation chamber 900 may be removed simultaneously or sequentially, either through the same or separate tap holes, barriers, partitions, pipes, or other inlets and outlets from the sulfidation chamber.

[0160] In some examples, supplemental heating or cooling may be utilized before, within, or after the transfer to maintain or modulate properties of the transferred molten metal sulfide mixture or molten metal oxide mixture. The illustrated example of FIG. 9 utilizes a transfer pipe or a launder 980 to move molten metal sulfide mixture from the sulfidation chamber 900 to the reduction chamber 950. In some examples, the transfer pipe 980 is configured to minimize materials exposure to ambient conditions external to the material processing system 990. In some examples, the transfer pipe 980 may utilize a valve or shutter to keep the transfer pipe 980 closed until flow is desired. Similarly, when a launder is used instead of transfer pipe, tapping hole can be closed with clay until flow is desired.

[0161] Additionally, the molten metal sulfide mixture may be moved to the reduction chamber via a ladle or launder system as well. In another example, the system may desire a gradual transfer of the sulfide during operation of the system. In some examples, the oxide feedstock and product materials, i.e. the molten metal oxide mixture and / or the molten metal sulfide mixture, may be added or removed from the sulfidation chamber 900 in batch, semibatch, or continuous manners. The batch, semibatch, and continuous addition or removal of the product materials may be leveraged to control liquid levels and residence times in the system.

[0162] As shown in this example, the reduction chamber 950 can be of a similar structure to that of the sulfidation chamber 900, where there are sidewalls 954, a roof 952, and a bottom 956. An electrode 966 similar to that of the sulfidation chamber 900 is utilized to heat the product material within the reduction chamber 950 and supply any heat needed to begin the reduction process. The reduction chamber 950 can include one or many tuyeres 970 to introduce a reducing agent into the furnace. Reducing agents can be also introduced via chamber inlet 976.

[0163] In some examples, the system may introduce reducing agent through an inner chamber 968 of the electrode 966 or top lance. A chamber inlet 976 or an exhaust outlet 972 may be located in any position along the structure of the reduction chamber 950 to introduce reducing agents or remove by-products produced by the reduction reaction. A tap hole 974 may be located on the reduction chamber to provide an outlet for molten metal after reduction.

[0164] In some examples, the structure of the sulfidation chamber 900 and the reduction chamber 950 may be covered in a refractory material. In some examples, the refractory material may cover only the roof 902, 952 while in others the refractory material may be disposed on at least the side walls 904, 954 and the bottoms 906, 956 of the chambers.

[0165] FIG. 10 illustrates another example of a material processing system incorporating two separate chambers connected via a transfer pipe or a launder 1080. The illustrated example of FIG. 10 is like the material processing system 990 of FIG. 9, but discloses two chambers for sulfidation each containing a plurality of electrodes 1016. In the illustrated example of FIG. 10, the two chambers are separate arc furnaces. As described above, the oxide feedstock is introduced into a first arc furnace 1040, i.e. a first sulfidation chamber. Once sulfidation of the oxide feedstock in the first furnace 1040 is complete, metal oxide in the molten metal oxide mixture 1010 is transported via a transfer pipe 1080 to a second arc furnace 1050, i.e. a second sulfidation chamber, where the molten metal oxide mixture 1060 undergoes another round of sulfidation before being removed via the outlet 1090. In other example, a second furnace 1050 is instead a reduction chamber where molten metal oxide mixture 1060 undergoes a reduction reaction producing a metal alloy 1062.

[0166] In some examples, the transfer pipe 1080 is configured to minimize materials exposure to ambient conditions external to the material processing system during transfer between the arc furnaces.

[0167] Once removed, the molten metal oxide mixture 1060 may proceed to another sulfidation process or reduction process. The metal sulfide in the molten metal sulfide mixture 1012 of the first furnace is removed via a tap hole 1026 and sent to another furnace for reduction. The same process is repeated in the second arc furnace via a tap hole 1074.

[0168] Another example of a dual chamber material processing system 1100 is described with reference to FIG. 11. The illustrated example is similar to the material processing system 990 described above, but discloses a first chamber 1130 and a second chamber 1132 within one arc furnace separated by a dam 1128. Therefore, the description of the dual chamber material processing system 1100 will generally discuss the main differences. The dam 1128 serves to separate the sulfide phase layer 1112 of each chamber. In another example, the dam 1128 may extend to a roof 1102 and establish two separate chambers wherein a tuyere 1108 as shown in the first chamber 1130 is also present in the second chamber 1132.

[0169] Electrodes 1116 are positioned above each chamber in order to provide localized heating within the chamber. A tap hole 1126 is located in the side wall 1104 of each chamber, and is utilized to move the sulfide phase layer to a reduction chamber or additional sulfidation furnace for further processing. The illustrated example in Fig. 11 has two inlets 1114 for feedstock, one located in first chamber 1130, and the other positioned in second chamber 1132. In further aspects of this example each feedstock inlet 1114 is correlated to only one chamber. In the illustrated example, oxide containing feedstock introduced via chamber inlet 1114 of chamber 1130 is first sulfidized in the first chamber 1130 and remaining molten metal oxide mixture 1110 flows into second sulfidation chamber 1132 for further sulfidation targeting to sulfidize same and / or different metal compared to first chamber.

[0170] In other examples, the chambers may work in parallel, each working on sulfidation of oxide feedstocks and then moving the respective metal sulfide to either another furnace for further refining or a reduction reactor, although not limited thereto. In another example where the dam 1128 establishes two separate chambers, sulfidation may occur in one of the chambers and the resulting metal sulfide may be transported through, over, and / or under the dam 1128 to the other chamber in order to undergo reduction. In another example sulfidation may occur in one chamber and further refining processes such as calcination or decomposition may occur in the other.

[0171] In another example the slope of the bottom surface 1106 is such that fluid is encouraged to move from one chamber over or under the dam 1128. In some examples the dam 1128 extends all the way from the roof 1102 of the furnace into phase layer 1112 allowing only phase layer 1112 to move into second chamber 1132. In others the dam 1128 only serves to separate the sulfide layers as shown in FIG. 11. In these examples a first sulfidation occurs in a first chamber 1130, with the sulfide phase layer 1112 accumulating in the system and eventually allowing remaining oxide phase layer 1110 to flow over the dam 1128 to move to the second chamber 1132 where a sulfidation, calcination or reduction process occurs or vice versa.

[0172] FIG. 12 is a flowchart 1200 showing an exemplary process of feedstock being sulfidized. Although flowchart 1200 provides discrete steps in a set order, a person of skill in the art will recognize on reading the disclosure that each step described may further be broken into several additional steps not specifically described and / or certain described steps may be combined into a single operation.

[0173] At step 1210 feedstock (e.g., containing gangue and three different metal oxides) enters the first sulfidation chamber. In step 1220 the feedstock is heated, a sulfidizing agent is input into the first sulfidation chamber, and the first sulfidation chamber environment or processing conditions are adjusted in order to target and sulfidize one of the three metal oxides. After the sulfidation of the first metal oxide, step 1222 occurs and the resulting metal sulfide is drawn out of the first sulfidation chamber. This may occur before, after, or during step 1230, where the remaining feedstock is transported to a second sulfidation chamber.

[0174] In some examples, the sulfidation chamber is run until the sulfide phase layer, i.e. molten metal sulfide mixture, almost reaches a tap hole positioned in the upper region of the sulfidation chamber, where upon reaching this level the metal oxide phase layer, i.e. molten metal oxide mixture, can be removed via an upper tap hole, and then the sulfide phase layer is removed via a lower tap hole.

[0175] In step 1240 the second sulfidation chamber is heated, the same sulfidizing agent as in the first sulfidation chamber or a second sulfidizing agent is added to the second sulfidation chamber, and the second sulfidation chamber environment or processing conditions are adjusted to sulfidize the second metal oxide, i.e. second molten metal oxide mixture. After sulfidation of the second metal oxide, step 1242 removes the resulting secondprocessed metal sulfide, i.e. second molten metal sulfide mixture, from the second sulfidation chamber. Step 1250 transports the remaining feedstock to a third sulfidation chamber. This may occur after, before, or during the step 1242.

[0176] At step 1260, a third sulfidizing agent is added to the third sulfidation chamber. The third sulfidation chamber's environment or processing conditions are adjusted and the third metal oxide undergoes sulfidation. In step 1262, the third and final metal oxide is removed from the third sulfidation chamber, this may be done before, after, or during step 1264 where the remaining gangue is removed from the system. The first, second, and third sulfidizing agents may be the same or they may be different from each other.

[0177] As discussed above, in some examples transfer pipes are used to move material between the chambers, while in other examples a ladle system may be used. In other examples, the amount of transfers changes in relation to the amount of metal oxides in the oxide feedstock. In some examples, fluxes or additive may be added to the sulfidation chambers to control the fluidity or other thermophysical properties or composition of the sulfide, oxide, or alloy feedstock or product. In some examples, additive(s) may be added to control the reducing power of the gaseous environment inside the chamber, including but not limited to carbon containing compounds.

[0178] FIG. 13 is a flowchart 1300 showing an exemplary process of feedstock being sulfidized and reduced. Although flowchart 1300 provides discrete steps in a set order, a person of skill in the art will recognize on reading the disclosure that each step described may further be broken into several additional steps not specifically described and / or certain described steps may be combined into a single operation.

[0179] At step 1310, an oxide feedstock (e.g., containing gangue and three different metal oxides) is input into a first sulfidation chamber. In step 1320, the oxide feedstock is heated, a sulfidizing agent is input into the first sulfidation chamber and the first sulfidation chamber environment or processing conditions are adjusted in order to target and sulfidize one of the three metal oxides. In step 1322, metal sulfide, i.e. molten metal sulfide mixture, resulting from the first sulfidation process is transported to a first reduction chamber. At step 1330 the remaining feedstock is transported to a second sulfidation chamber.

[0180] In step 1324, once the first metal sulfide is in the first reduction chamber, a reducing agent is introduced to reduce the first metal sulfide to a first metal. In step 1340,the second sulfidation chamber is heated, a sulfidizing agent is added to the second sulfidation chamber, and the second sulfidation chamber's environment or processing conditions are adjusted to sulfidize the second metal oxide. After sulfidation of the second metal oxide, step 1342 occurs where the resulting metal sulfide is removed from the second sulfidation chamber and transferred to a second reduction chamber. In step 1344, the second metal sulfide is reduced via a reducing agent to a second metal. In step 1350, the remaining feedstock is transported to a third sulfidation chamber. In step 1360, a sulfidizing agent is added to the third sulfidation chamber and the third sulfidation chamber's environment or processing conditions are adjusted to target the third metal oxide.

[0181] In step 1362, the third and final metal oxide is removed from the third sulfidation chamber and sent to a third reduction chamber. This may be done before, after, or during step 1366 where the remaining gangue is removed from the system. In step 1364, the third metal sulfide is reduced to a third metal completing the processing of smelting the feedstock. As discussed above in some examples transfer pipes or launders are used to move material between furnace chambers, in other examples a ladle system may be used. In other examples, the amount of steps changes in relation to the amount of metal oxides in the feedstock.

[0182] FIG. 14 depicts a block diagram of a controller 1400 for a material processing system, interacting with a furnace 1410 as described above. In some examples, the controller interacts with one or more chambers or chamber portions within the same furnace. The controller 1400 includes a power module 1402 and a communications module 1004. The communications module 1404 may enable the controller to transmit and receive data with external systems as well as the furnace 1410.

[0183] The furnace 1410 may also contain a sensor module 1412 which may include but is not limited to flow sensors, hall effect sensors, resistivity sensors, thermopower sensors, temperature sensors, pressure sensors, infrared spectrometers, mass spectrometers, and electrochemical sensors. The furnace 1410 may also have a configuration module which may control aspects of the furnace such as opening and closing valves on inlet ports under direction of the controller 1400.EXAMPLESExample 1

[0184] Ferrochromium alloy is the main source of chromium used in the manufacturing of stainless steel, apart from the chromium present in remelted stainless steel scrap. Ferrochromium is made through the reduction of chromite mineral, and can be produced in high, medium, and low carbon varieties based on the reduction and converting technologies employed. High carbon ferrochromium is produced via carbothermic reduction of chromite, which contains oxides of chromium, iron, and various gangue elements. Since chromite is an oxide-based mineral, direct carbon dioxide emissions are inherent to the conventional carbothermic reduction process. One avenue to decrease carbon dioxide emissions from chromite reduction is to perform a treatment on the mineral to change its chemical makeup. Through sulfidation of chromite, the chromium and iron oxides can be converted into sulfides. Once chromium and iron are sulfides, they are more amenable to reduction to ferrochromium alloy without direct carbon dioxide emissions.

[0185] In this example, chromite was sulfidized via three different approaches (1 solid-gas and 2 liquid state) to illustrate the comparative advantages of higher temperature liquid state sulfidation versus lower temperature solid-gas sulfidation. Solid-gas sulfidation was conducted via reacting a bed of solid chromite concentrate particles held in a graphite reactor tray at 1300 °C for 2 hours with elemental sulfur gas as the sulfi dizing agent at a sulfur to sulfur dioxide partial pressure ratio of 106and a system pressure of 1 atm. FIG. 15a shows a Scanning Electron Microscope (SEM) micrograph image of sulfidized chromite grains after the solid-gas sulfidation reaction. The lighter gray regions in the images depict product phases richer in sulfur, while darker regions depict product phases richer in oxygen. The presence of unreacted oxide-rich regions in the center of chromite grains indicates that the sulfidation reaction was incomplete.

[0186] FIG. 15b is an EDS element map for chromium that shows the same area as in FIG. 15a, but with lighter regions corresponding to locations where chromium content is higher and darker regions corresponding to locations where chromium content is lower. Generally, chromium remains present in most of the chromite grains after sulfidation is complete, with the chromium content slightly lower on the outside edges of grains.

[0187] FIG. 15c is an EDS element map for sulfur that also shows the same area as in FIG. 15a, but with lighter regions corresponding to locations where sulfur content is higher and darker regions corresponding to locations where sulfur content is lower. Sulfur distribution is uneven throughout the grains following sulfidation, with sulfur-rich regions concentrated on the outside edges of grains.

[0188] When comparing FIGS. 15a-15c, solid-gas sulfidation of chromite is observed to be uneven throughout the chromite grains. Sulfur gas was able to react with some chromium on the outside of the grain, but struggled to penetrate deeper into the chromite particles. This limitation left a substantial amount of chromium inside the grain unsulfidized. Thus, employing a solid-gas sulfidation environment may leave a large percentage of chromium unreacted due to poor mass transport and kinetic effects, decreasing the metal recovery from the feedstock and necessitating longer sulfidation reaction time or finer grinding of chromite feedstocks.

[0189] The first liquid state sulfidation approach was conducted on chromite with a silica additive (3: 1 chromite to silica by mass) at a temperature of 1700 °C for 30 minutes in an alumina crucible using sulfur gas generated from the thermal decomposition of iron-rich sulfides at a pressure of 0.001 atm. Liquid state sulfidation does not need to be conducted under vacuum and can also be accomplished at ambient or elevated pressures with an appropriate sulfidizing agent. The system did not contain any carbon species or other reductants, enabling a demonstration of liquid state sulfidation without reducing conditions or reductive additives. The silica additive was utilized to modulate the viscosity, surface tension and basicity of the molten oxide. FIG. 15d shows a SEM micrograph image of solidified sulfidized chromite grains after the liquid state sulfidation process. The lighter gray regions in the images depict product phases richer in sulfur, while darker regions depict product phases richer in oxygen. The absence of clear particles and the distribution of lighter, sulfur-rich phases throughout indicates that molten sulfidation of chromite was able to proceed to completion.

[0190] FIG. 15e is an Energy -Dispersive X-ray Spectroscopy (EDS) element map for chromium that shows the same region as in FIG. 15d, but with lighter regions corresponding to areas where chromium content is higher and darker regions corresponding to areas where chromium content is lower. Chromium is observed to be distributed through the sulfidized product. FIG. 15f is an EDS element map for sulfur that also shows the same region as inFIG. 15d, but with lighter regions corresponding to areas where sulfur content is higher and darker regions corresponding to areas where sulfur content is lower. Sulfur is observed to be distributed throughout the sulfidized product, with locations rich in sulfur overlapping with regions rich in chromium.

[0191] FIGS. 15d— 15f indicate the molten state sulfidation was able to sulfidize the chromium throughout the chromite. Chromium and sulfur are generally observed to partition to the same phases. Some unsulfidized chromium still remains in small oxide particles distributed throughout, but these phases are generally smaller and less prevalent than unreacted oxide regions observed during solid-gas sulfidation. Compared to solid-gas sulfidation, liquid state sulfidation is shown to be advantageous in sulfidizing chromium from chromite, with higher degrees of chromium sulfidation achieved in less reaction time. Molten state sulfidation as successfully demonstrated in this example can be conducted in a variety of reactors, such as those illustrated in FIGS. 1-11.

[0192] The second liquid-state sulfidation approach was conducted on chromite that had already been partially sulfidized, where iron species had already selectively partitioned to sulfide phases while chromium species had remained as oxides. The partially sulfidized chromite was melted in a graphite crucible with a silica additive (3 : 1 chromite to silica by mass) at 1650 °C for 30 minutes. Upon melting, the iron sulfide served as a sulfidizing agent for chromium oxides, with graphite present from the crucible serving as an additive to create a partially reducing atmosphere environment.

[0193] The solidified products from the second liquid sulfidation approach are depicted in FIG. 16, with compositions reported in Table 1 as measured via SEM-EDS. Three bulk liquids were observed to form during the sulfidation: a chromium-rich matte 1610, a silica-rich slag 1620, and an iron-rich metal 1630. Within the sulfide matte, small metal precipitates were observed that were less chromium-rich than the bulk metal, likely precipitating within the matte during cooling. The formation of the bulk iron-rich metal is attributed to the partially reducing environment arising from the use of the graphite crucible.Table 1. Product phases from liquid state sulfidation of partially sulfidized chromite under reducing conditions as determined via SEM-EDS.

[0194] Sulfidation of chromium was observed to be largely complete, with limited residual chromium content remaining in the slag. Compared to solid-gas sulfidation as described in this example, liquid state sulfidation is observed to achieve higher degrees of sulfidation for target elements in less reaction time. It is shown that additives, such as graphite or other reductants, can be used to help control how reducing the environment is during liquid state sulfidation, which in turn can contribute to the formation of distinct liquid product phases. However, as also demonstrated in the first liquid state sulfidation approach in this example, liquid state sulfidation can also be conducted without dedicated additives that contribute to a reducing environment.Example 2

[0195] During liquid state sulfidation, the target metal sulfide product may be too dilute to form a liquid matte phase layer separate from the liquid metal oxide. In these cases, an additive may be added to the chamber to collect sulfidized products in preparation for removal from the chamber. The additive may serve as a host and / or collector for small sulfide droplets which may not be prevalent enough to form their own coherent liquid phase. The additive may be introduced to the sulfidation furnace directly as a liquid, or as a solid that then melts within the furnace to form a bulk liquid mixture.

[0196] In some instances, the sulfide product may be so dilute that it does not exceed its solubility limit within the of the liquid / semiliquid oxide mixture and does not nucleate and precipitate from the liquid oxide mixture on its own. The presence of an additive may either decrease the solubility limit of the sulfide in the molten metal oxide mixture or serve as an interface to facilitate the nucleation of sulfide product droplets. The additive mayconsist of, but is not limited to, a sulfide, a halide, sulfosalt, a liquid alloy, or some combination thereof.

[0197] The same or other additives may be employed during sulfidation to adjust the densities, viscosity, surface tension, thermopower, melting points, and / or the basicity of the molten oxide and sulfide phases. Generally, more acidic oxide mixtures within the chamber support higher metal recovery during sulfidation of transition metals. However, sulfidation may still benefit from more basic slag chemistries in some systems. Acidic or basic additives can also be employed to modulate the selectivity of liquid state sulfidation process for targeted sulfidation of one species versus another.

[0198] The beneficial effect of additives to support oxide / sulfide phase separation during processing of chromite concentrate was demonstrated. A mixture of calcium oxide, aluminum oxide, and silicon oxide were introduced to the chromite to help modulate the density, viscosity, surface tension, and basicity of the molten oxide phase, which was melted at 1600 °C. Nickel mixed sulfide precipitate (MSP) was also mixed in the system during melting to help coalesce any chromite sulfidation products. Utilization of lower melting nickel sulfide species increases the fluidity of higher melting sulfide species, serving to improve phase separation between oxides and sulfides.FIG. 17 shows an image of phase separation of a mixed metal sulfide matte 1710 and metal oxide slag 1720 following melting for 15 minutes. The darker metal oxide 1720 phase has clearly separated and floated above the brighter metal sulfide 1710, aided by oxide and sulfide additives in the system. Halide or sulfosalt additives can also be employed to support similar phase separation. As shown in FIG. 17 the liquid-gas sulfidation environment produces, after cooling, a solid metal sulfide showing characteristics that it was molten during processing, as opposed to a sintered result achieved from a solid-gas sulfidation environment. These results indicate that the use of additives can enhance the molten state sulfidation process through modulation of thermophysical properties toward improved phase separation and sulfide product recovery. The evidence of clear, immiscible oxide and sulfide liquids in this example further supports the furnace designs in FIGS. 1-11, where molten oxide and sulfide liquids can be separately tapped from the furnace vessel or directed into selected or separated furnace chambers.Example 3

[0199] Pickling sludge is a waste material from surface treatment of stainless steel products. Stainless steel pickling sludge waste may be pyrolyzed to produce an oxide mixture of iron, chromium, nickel, molybdenum, copper, and other species. Liquid state sulfidation is a promising method to selectively recover nickel in a sulfide matte from the pickling sludge oxide mixture.

[0200] Four different scenarios for liquid state sulfidation of pyrolyzed stainless steel picking sludge were tested, with operating conditions for experimental trials reported in Table 2. Scenario 1 was meant to serve as a baseline for molten state sulfidation of pyrolyzed stainless steel picking sludge using iron sulfide (FeS) as a sulfur source. Scenario 2 was meant to serve as a comparison against Scenario 1, where elemental sulfur generated through in situ decomposition of pyrite was utilized as a sulfur source instead. Scenario 3 was meant to serve as a comparison against Scenario 1, where different oxide additives were present. Scenario 4 was meant to serve as a comparison against Scenarios 1 and 2, where extra pyrite was added to serve as a sulfide phase additive. Additives or reductants to create or modulate a reducing environment or atmosphere in the system were not utilized in any of these scenarios.Table 2. Experimental conditions for liquid state sulfidation of pyrolyzed stainless steel pickling sludge.

[0201] SEM images of the interface region between matte and slag products for the four scenarios are included in FIG. 18. Slag phases are darker gray and matte phases arelighter gray in the micrographs. Matte and slag phases are observed to have been molten and solidified, as opposed to sintered, indicating that at the sulfidation temperature the system was molten. The compositions of bulk oxide slag and sulfide matte phases following liquid state sulfidation of pyrolyzed stainless steel pickling sludge for the four scenarios are included in Table 3 as determined via SEM-EDS mapping. Nickel, copper, manganese, and molybdenum generally partitioned to the sulfide matte phase during sulfidation, whereas chromium vanadium, cobalt, silicon, aluminum, and calcium generally partitioned to the oxide slag. While below the SEM-EDS detection limit in this example, titanium is anticipated to exhibit similar behavior to vanadium under these sulfidation operation conditions and partition to the slag phase. Similarly, magnesium is expected to exhibit similar partitioning behavior to calcium under these operating conditions. In this way, liquid state sulfidation can be employed to at least partially separate rare earth elements between oxide and sulfide phases. Chromium rich oxides were observed to accumulate at the interfaces between the slag and matte phases and along interfaces with the crucible and are therefore more prevalent in interfacial oxide phases than the composition values reported in Table 3 suggest. Iron partitioning was split between matte and slag phases. The selective partitioning of nickel, copper, molybdenum, and manganese to sulfide phases demonstrates that molten state sulfidation can be conducted selectively.Table 3. Matte and slag product compositions for liquid state sulfidation of pyrolyzed stainless steel pickling sludge as determined via SEM-EDS.

[0202] Scenarios 1 and 2 were designed to serve as a point of comparison between condensed phase sulfur sources (Scenario 1, FeS) and gaseous sulfur sources (Scenario 2, elemental sulfur gas evolved during pyrite thermal decomposition). Comparing the composition values between Scenario 1 and 2 reported in Table 3, minimal differences in matte and slag compositions were observed. This result indicates that either gaseous or condensed sources of sulfur may be effectively utilized during liquid state sulfidation processes.

[0203] Scenarios 1 and 3 were designed to serve as a point of comparison between different oxide additives, where Scenario 3 had additional lime and alumina added compared to Scenario 1. Epoxy -mounted samples 40 mm in diameter showing cross sections of matte and slag phases from Scenario 1 (top) and Scenario 3 (bottom) are included in FIG. 19. Matte product phases from Scenario 1 are observed to form a range of larger jagged droplets 1910 and a cloud of smaller, more rounded droplets 1920 suspended in the slag 1930. Meanwhile, matte product phases from Scenario 3 are better coalesced and are observed to form smoother droplets 1940 in the slag 1950 without the substantially less cloud of smaller matte droplets. The better coalescence of matte droplets observed in Scenario 3 illustrates the role of oxide additives in helping modulate thermophysical and properties for matte collection in the system, including but not limited to viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and / or melting point.

[0204] As shown in Table 3, the bulk matte liquid phase in Scenario 3 is observed to be more enriched in nickel compared to Scenario 1. Meanwhile, the slag in Scenario 3 is observed to be more enriched in iron compared to Scenario 1. These results indicate that liquid state sulfidation during Scenario 3 was more selective for nickel versus iron than in Scenario 1. While copper is also observed to be more enriched in the matte from Scenario 3 versus Scenario 1, molybdenum was observed to remain predominately in the slag phase from Scenario 3. These differences have arisen from different slag additive chemistry of Scenario 3 (lime and additional alumina) vs Scenario 1. Indeed, the more basic slag system due to the lime additive in Scenario 3 led to less overall transition metal sulfidation, with the sulfidation that did happen occurring more selectively for chalcophilic elements. In some system chemistries however, trends observed in slag basicity towards sulfidation selectivity can be outweighed by thermodynamic mixing effects in the slag or matte solutions between different components. Nevertheless, the results from comparing Scenarios 1 and 3 indicatethat oxide additives can also help modulate the chemical selectivity during molten state sulfidation, not just thermophysical properties contributing to phase separation.

[0205] Scenario 4 versus Scenarios 1 and 2 was designed to serve as a comparison between the effects of sulfidation without and without sulfide additives. Excess pyrite was added in Scenario 4 to help collect and coalesce matte droplets formed during the molten state sulfidation. Comparing the compositions of slag and matte phases between Scenarios 1, 2, and 4, similar iron levels are observed in the slag, indicating that excess pyrite addition did not lead to substantially more iron oxide sulfidation even though additional sulfur gas could be generated due to additional pyrite thermal decomposition. This indicates that the excess iron sulfides from the pyrite served predominately as a sulfide additive available to help collect and coalesce matte droplets.

[0206] An epoxy-mounted sample 40 mm in diameter showing cross sections of matte and slag products from Scenario 1 (top) and a cross section of the 45 mm diameter alumina crucible with matte and slag products still in situ from Scenario 4 (bottom) are included in FIG. 20. Matte product phases from Scenario 1 are observed to form a range of larger jagged droplets 2010 and a cloud of smaller, more rounded droplets 2020 suspended in the slag 2030. The products from the sulfidation in Scenario 1 had to be fractured and removed from their alumina crucible to reveal matte phases suspended inside the center of the slag volume, which had not agglomerated into a visible liquid matte pool in the bottom of the crucible. Meanwhile, in Scenario 4 sufficient matte coalescence had occurred to support visible observation of matte at the bottom of the alumina crucible.

[0207] When the alumina crucible 2040 was cross sectioned, solidified matte liquid 2050 was observed to have accumulated in the bottom half of the melt and had coalesced around the solidified oxide slag pool 2060, adhered along one wall of the alumina crucible due to surface tension effects. Comparing the bulk accumulation of liquid matte in Scenario 4 versus the suspended droplets of liquid matte in Scenarios 1 and 2, the sulfide additive clearly helped support agglomeration and setting of the denser matte phases 2050 from the less dense slag phases to the bottom of the crucible 2040. These results indicate that the use of additives can aid in the thermophysical behavior of sulfide products from liquid state sulfidation processes. These additives do not need to be sulfides; metallic, halide, and sulfosalt species can also help control molten matte phase stability and properties includingbut not limited to viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and melting point.

[0208] Summarizing the results of Example 3, liquid state sulfidation of pyrolized stainless steel pickling sludge enabled the selective sulfidation of various oxide components of a molten oxide feedstock into a sulfide matte. Through the use of additives to one or more of the molten slag and matte phases, the thermophysical properties of the liquids can be modulated to support matte and slag phase coalescence and density driven phase separation. Elements were observed to selectively partition between slag and matte product phases, indicating that liquid state sulfidation can be conducted selectively for target elements, as demonstrated in this example for partitioning of nickel, copper, iron, chromium, manganese, molybdenum, vanadium, cobalt, silicon, aluminum, and calcium. Additives are also observed to help tune liquid state sulfidation selectively. Rare earth species, while below the SEM-EDS detection limit in this example, will partition between the slag and matte in this system based on the balance of their siderophilic versus chalcophilic versus lithophilic behaviors and the presence of additives in the system at a given dosage of sulfidizing agent.

[0209] 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.

[0210] 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.

[0211] 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 LIST840, 1100 multi -chamber furnace850, 100, 200, 300, 300b, 400, 600 sulfidation chambers852 oxide feedstock854 sulfidizing agent856 sulfur dioxide gas858, 910 mixed metal oxide, molten metal oxide mixture860, 920 metal sulfide, molten metal sulfide mixture870 reduction chambers872 reducing agent874 sulfur-containing gas876 compound of reducing agent and sulfur878 alloy of metal990 material processing system102, 152, 302, 302b, 502, roof104, 154, 304, 304b side wall106, 156, 306, 306b bottom108, 170, 308, 308b, 408, 608, 708 tuyere110, 310, 310b, 410, 510, 610, 710 molten metal oxide mixture112, 312, 312b, 412, 520, 612, 620 molten metal sulfide mixture114, 414, 514, 614 chamber inlet116, 166, 216, 516 electrode118, 168, 218 inner chamber120 exhaust gas121 gas outlet172 exhaust outlet174, 626, 674 tap hole180, 680 transfer pipe322 coil324, 324b refractory lining326b resistive heating elements328, 328b, 728 top lance430, 530 outlet432 taphole500 multi -furnace system528 dam540 first sulfidation chamber portion550 second sulfidation chamber portion1020 solid layer1040 first arc furnace1050 second arc furnace1090 outlet1200, 1300 flowchart 1210-1264 steps of the process of FIG. 12 1300-1366 steps of the process of FIG. 13 1400 controller1402 power module1404 communications module1410 furnace1412 sensor module1610, 1710, 1910, 1920, 1940, 2010,2020, 2050 sulfide matte experimental product1620, 1720, 1930, 1950, 2030, 2060 oxide slag experimental product1630 metal alloy experimental product2040 alumina crucible

Claims

CLAIMS:

1. A system for processing materials, comprising:- one or more sulfidation chambers configured to maintain a high operating temperature and hold a metal oxide mixture in a molten form; and- one or more sulfidizing agent sources connected to the sulfidation chamber(s) and configured to introduce one or more solid, liquid, or gaseous sulfidizing agents to the sulfidation chamber(s), wherein the sulfidizing agent(s) is / are configured to react with at least a portion of the molten metal oxide mixture to form a metal sulfide mixture in a molten form, wherein the molten metal sulfide mixture is separated from any remaining molten metal oxide mixture in the sulfidation chamber(s).

2. The system of claim 1, wherein the sulfidation chamber(s) comprise(s) one or more chamber inlets configured to feed an oxide feedstock to the sulfidation chamber(s) to form the molten metal oxide mixture; wherein the oxide feedstock comprises one or more feedstock metals selected from the group of iron, nickel, chromium, molybdenum, cobalt, silicon, aluminum, magnesium, calcium, titanium, copper, rare earth metals, vanadium, and manganese.

3. The system of claim 2, wherein an oxide additive is added to the sulfidation chamber(s) to adjust viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and / or melting point of the molten metal oxide mixture.

4. The system of claim 2 or 3, wherein the chamber inlet(s) is / are further configured to add one or more sulfide additives into the sulfidation chamber(s) to adjust viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and / or melting point of the molten metal sulfide mixture.

5. The system of any one of the preceding claims 2-4, wherein the chamber inlet(s) is / are further configured to add one or more halides containing feedstock to the sulfidation chamber(s) to adjust viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and / or melting point of the molten metal oxide or the molten metal sulfide mixture.

6. The system of any one of the preceding claims, wherein the sulfidation chamber(s) comprise(s) a furnace, a reactor and / or a converter, such as an AC arc furnace, a DC arc furnace, a submerged arc furnace, a rotary kiln, a multihearth furnace, a fluidized bed reactor, a flash smelter, an electroslag refiner, a vacuum arc remelter, an induction furnace, a resistively heated furnace, a shaft furnace, a converter, a vacuum arc furnace, a blast furnace or a vacuum converter.

7. The system of any one of the preceding claims, wherein the sulfidizing agent(s) are selected from the group of sulfur containing species, such as elemental sulfur, carbon disulfide, metals sulfide, and hydrogen sulfide, and combinations thereof.

8. The system of any one of the preceding claims, wherein the sulfidizing agent source(s) comprise(s) one or more sulfidizing agent inlets, such as at least one of a tuyere, a taphole, a hollow electrode, a lance, a packed wire, tube or hose, or a lance.

9. The system of claim 8, wherein the sulfidizing agent inlet(s) is / are configured to adjust a flowrate and a temperature of the sulfidizing agent(s) to at least partially control wear of a freeze lining adjacent the sulfidizing agent inlet(s).

10. The system of claim 8 or 9, wherein the sulfidizing agent inlet(s) is / are configured to adjust the flowrate and the temperature of the sulfidizing agent(s) to at least partially control a bubble size in the molten metal oxide mixture, the molten metal sulfide mixture and / or foam on their surface resulting from of the sulfidizing agent(s) introduced into the sulfidation chamber(s).

11. The system of any one of the preceding claims 8 to 10, wherein the sulfidizing agent inlet(s) is / are configured to control a ratio of solids to liquids to gases for controlling a bubble size in the molten metal oxide mixture, the molten metal sulfide mixture and / or foam on their surface resulting from of the sulfidizing agent(s) introduced into the sulfidation chamber(s).

12. The system of claim 10 or 11, wherein the control comprises reducing the bubble size of the molten metal oxide mixture, the molten metal sulfide mixture and / or foam on their surface resulting from and / or making it uniform.

13. The system of any one of the preceding claims, wherein the sulfi dizing agent(s) is / are generated within the sulfidation chamber(s) through thermal decomposition, hydrogen reduction, or metallothermic reduction of a metal sulfide.

14. The system of any one of the preceding claims 2-13, wherein: the chamber inlet(s) is / are configured to add a bulk liquid mixture to the sulfidation chamber(s) to at least partially coalesce the molten metal sulfide mixture; or a bulk liquid mixture is added to second chamber or a ladle holding the mixture of molten metal sulfide and metal oxide; wherein the bulk liquid mixture comprises at least one of a sulfide, halide, sulfosalt, or liquid alloy, or any combination thereof.

15. The system of any one of the preceding claims 2-14, wherein: a solid additive is added to chamber with the oxide feedstock to improve the coalescing of the molten metal sulfide mixture; wherein the solid additive comprises at least one of a sulfide, halide, sulfosalt or metal alloy, or any combination thereof.

16. The system of any one of the preceding claims, wherein the molten metal oxide mixture comprises feedstock containing metal to be recycled.

17. The system of any one of the preceding claims, wherein the sulfidation chamber(s) further comprise(s) one or more reducing agent inlet(s) for introducing reducing agent into the sulfidation chamber(s), to subject the molten metal sulfide mixture a reduction refining reaction.

18. The system of any one of the preceding claims 1 to 16, further comprising: one or more reduction chambers containing a reducing agent and configured to maintain a high operating temperature.

19. The system of claim 17 or 18, wherein the reducing agent is selected from the group of aluminum, silicon, silicon carbide, magnesium, calcium, calcium carbide, iron, chromium, oxygen, sulfur dioxide, hydrogen, coal, coke, and biomass, and mixtures thereof.

20. The system of claim 17 or 19, wherein the molten metal sulfide mixture is transferred from the sulfidation chamber(s) to the reduction chamber(s) in a molten or semi-molten state, wherein the molten metal sulfide mixture entering the reduction chamber(s) is subjected to a reduction refining reaction.

21. The system of claim any one of the preceding claims 18-20, further comprising a transferring system and / or a launder configured to transfer the molten metal sulfide or oxide mixture between the sulfidation chambers, between the reduction chambers or from the sulfidation chamber(s) to the reduction chamber(s) without exposure to ambient conditions.

22. The system of any one of the preceding claims 18-21, wherein the molten metal sulfide mixture is removed from the sulfidation chamber(s) and cooled to form a solid metal sulfide mixture, which is crushed and transferred to the reduction chamber(s).

23. The system of any one of the preceding claims 18-22, wherein the sulfidation chamber(s) and the reduction chamber(s) are positioned sequentially in a single furnace, reactor or converter.

24. The system of any one of the preceding claims 18-23, wherein the sulfidation chamber(s) is / are positioned in a first furnace, reactor or converter and the reduction chamber(s) is / are positioned in a second furnace, reactor or converter, wherein the first furnace, reactor or converter and the second furnace reactor or converter, are positioned sequentially.

25. The system of claim 24, wherein the first furnace, reactor or converter, and the second furnace, reactor or converter, are configured to conduct the sulfidation and the reduction sequentially and / or parallel.

26. The system of any one of the preceding claims 18-25, comprising two or more sulfidation chambers, wherein the molten metal oxide mixture is configured to be transferred from a first sulfidation chamber and / or the reduction chamber to a second sulfidation chamber, and optionally from the second sulfidation chamber to a third sulfidation chamber.

27. The system of 26, wherein the liquid metal sulfide mixture is configured to be removed from the first sulfidation chamber and / or the second sulfidation chamber before the transferring of the molten metal oxide mixture.

28. The system of any one of the preceding claims, wherein the high operation temperature of the sulfidation chamber(s) is at least 80 % of a melting temperature of the metal oxide mixture, for example 1000-3000 °C, such as 1300-2500 °C.

29. The system of any one of the preceding claims, wherein the high operation temperature of the reduction chamber(s) is at least 80 % of a melting temperature of the metal sulfide mixture.

30. A method for processing materials, comprising:- inputting a metal oxide mixture to one or more sulfidation chambers configured to maintain a high operating temperature, to form the molten metal oxide mixture; and- introducing one or more solid, liquid, or gaseous sulfidizing agents to the sulfidation chamber(s) by one or more sulfidizing agent sources connected to the sulfidation chamber(s), wherein the sulfidizing agent(s) is / are configured to react with at least a portion of the molten metal oxide mixture to form a metal sulfide mixture in a molten form; wherein the molten metal sulfide mixture is separated from any remaining molten metal oxide mixture in the sulfidation chamber(s).

31. The method of claim 30, comprising feeding oxide feedstock to the sulfidation chamber(s) via one or more chamber inlets to form the molten metal oxide mixture.

32. The method of claim 31, comprising adding an oxide additive to the sulfidation chamber(s) to adjust viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and / or melting point of the molten metal oxide mixture.

33. The method of claim 31 or 32, comprising adding one or more sulfides into the sulfidation chamber(s) via the chamber inlet(s), to adjust viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and / or melting point of the molten metal sulfide mixture.

34. The method of any one of the preceding claims 30-33, comprising adding one or more halides containing feedstock to the sulfidation chamber(s) via the chamber inlet(s), to adjust viscosity, density, basicity, surface tension, conductivity, thermopower, boiling point, and / or melting point of the molten metal oxide or the molten metal sulfide mixture.

35. The method of any one of the preceding claims 30-34, comprising adjusting the flowrate and the temperature of the sulfidizing agent(s) by sulfidizing agent inlet(s) connected to sulfidizing agent source(s), to at least partially control a bubble size in the molten metal oxide mixture, the molten metal sulfide mixture and / or foam on their surface resulting from the sulfidizing agent(s) introduced into the sulfidation chamber(s), or to control a ratio of solids to liquids to gasses for controlling a bubble size in the molten metal oxide mixture, the molten metal sulfide mixture and / or foam on their surface resulting from the sulfidizing agent(s) introduced into the sulfidation chamber(s).

36. The method of claim 35, comprising adding a bulk liquid mixture to the sulfidation chamber(s) via the chamber inlet(s), to collect the molten metal sulfide mixture.

37. The method of any one of the preceding claims 30-36, comprising introducing reducing agent into the sulfidation chamber(s) via one or more reducing agent inlet(s) connected to the sulfidation chamber(s), to subject the molten metal sulfide mixture a reduction refining reaction.

38. The method of any one of the preceding claims 30-37, comprising transferring the molten metal sulfide mixture from the sulfidation chamber(s) to one or more reduction chamber(s) in a molten or semi-molten state, wherein the molten metal sulfide mixture entering the reduction chamber(s) is subjected to a reduction refining reaction.

39. The method of claim 38, wherein the transferring is conducted by a transferring system and / or a launder.

40. The method of any one of the preceding claims 30-39, comprising:- removing the molten metal sulfide mixture from the from the sulfidation chamber(s); - cooling the molten metal sulfide mixture to form a solid metal sulfide mixture;- crushing the solid metal sulfide mixture;- optionally comminuting and at least separating a portion of one of sulfide phases and / or impurity oxide phases present in the solid metal sulfide mixture; and- transferring the solid metal sulfide mixture to one or more reduction chamber(s).

41. The method of any one of the preceding claims 30-40, comprising transferring the molten metal oxide mixture from a first sulfidation chamber and / or a reduction chamber to a second sulfidation chamber, and optionally from the second sulfidation chamber to a third sulfidation chamber.

42. The method of claim 41, comprising removing the liquid metal sulfide mixture from the first sulfidation chamber and / or the second sulfidation chamber before the transferring of the molten metal oxide mixture.

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