COPPER (Cu) REMOVAL FROM STEEL

Abstract

A method for separating a first metal from a second metal or alloy is disclosed, wherein the first metal has a melting point lower than that of the second metal or alloy. A method for separating steel from contaminants such as copper is also disclosed. The method involves heating the first metal and the second metal or alloy to a temperature below the melting point of the second metal or alloy and then reacting the first metal with a halogen gas to form a separable metal halide, or embrittling the first metal and separating the embrittled first metal from the second metal or alloy.

Description

TECHNICAL FIELD

[0001] The present specification relates to a method for removing a metal from a second metal or alloy. BACKGROUND

[0002] The amount of steel discarded each year has been increasing over time and more steel must be produced from scrap to achieve emissions targets. The presence of contaminants such as copper limits the amount of scrap steel that can be recycled to replace general purpose steel. Copper as a contaminant in steel, if found as large components, is typically hand picked out of the steel leaving the vast majority of copper contaminants in the form of wiring in automotive scrap, appliances and equipment. Only a very small amount of steel, for example, engine blocks and powder metallurgy products, contain copper as part of the alloy. This means that a process for extracting copper from steel should focus primarily on removing copper wire.

[0003] Different methods for separating copper from steel have been proposed and tested, including manual and magnetic separation; however, this remains a challenging task, especially in achieving less than 0.4 wt.% copper in scrap steel. In the solid state, removing copper is problematic due to physical mixing. In the molten state, copper is practically impossible to remove due to its noble character relative to iron. Daehn et al. (Metallurgical and Materials Transactions B, Vol. 50B, 2019, 1225-1240, which is incorporated by reference herein) discloses different methods for removing residual copper from steel.

[0004] There is a need in the art for a method for separating a first metal from a second metal or alloy. Additionally, there is a need in the art for a method for separating a first metal from a second metal or alloy, wherein the physical properties (such as melting point, heat capacity, gas solubility, and thermal conductivity) of the first metal are different from the physical properties of the second metal or alloy. Further, there is a need in the art for a method, wherein one or more reagents used to separate the first metal from the second metal or alloy can be recycled. SUMMARY

[0005] In a first aspect, the present specification discloses a method for separating a first metal from a second metal or alloy, wherein the melting point of the first metal is lower than the melting point of the second metal or alloy, the method comprising the steps of:

[0006] heating the first metal and the second metal or alloy to a temperature below the melting point of the first metal and below the melting point of the second metal or alloy;

[0007] reacting the first metal with a halogen gas to form a metal halide; and

[0008] separating the metal halide from the second metal or alloy.

[0009] In a second aspect, the present specification relates to a system for separating a first metal from a second metal or alloy, wherein the melting point of the first metal is lower than the melting point of the second metal or alloy, the system comprising:

[0010] heating the first metal and the second metal or alloy to a temperature below the melting point of the first metal and below the melting point of the second metal or alloy;

[0011] reacting the first metal with a halogen gas to form a metal halide;

[0012] separating the metal halide from the second metal or alloy;

[0013] reacting the metal halide to reform the first metal and the halogen gas; and

[0014] recycling the halogen gas.

[0015] In a third aspect, the present specification relates to a method for separating a first metal from a second metal or alloy, the method comprising the steps of:

[0016] heating the first metal and the second metal or alloy to a temperature below the melting point of the first metal;

[0017] exposing the first metal to a gas, thereby allowing formation of a brittle first metal;

[0018] separating the brittle first metal from the second metal or alloy.

[0019] In a fourth aspect, the present specification relates to a method for producing steel, the method comprising one or more of the methods disclosed herein. BRIEF DESCRIPTION OF DRAWINGS

[0020] Reference will now be made to the drawings in which the example embodiments of the present application are illustrated by way of example, in which:

[0021] Figure 1 A steel production method is shown with a reactive gas pre-treatment stage by direct resistance heating.

[0022] Similar reference characters refer to similar components throughout the different drawings. DETAILED DESCRIPTION

[0023] Unless otherwise explained, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to any methods and materials described herein can be used in practice to test the present invention, typical materials and methods are described herein. In describing and claiming the present invention, the terminology used is disclosed below.

[0024] As described herein, in a first aspect, this specification discloses a method for separating a first metal from a second metal or alloy, wherein the first metal has a melting point lower than the melting point of the second metal or alloy, the method comprising the steps of:

[0025] heating the first metal and the second metal or alloy to a temperature below the melting point of the first metal and below the melting point of the second metal or alloy;

[0026] reacting the first metal with a halogen gas to form a metal halide; and

[0027] The metal halide is separated from the second metal or alloy.

[0028] As used herein, the term "first metal" is not particularly limited and should be understood by those skilled in the art, or can be determined. In one embodiment, for example and without limitation, the first metal is copper (Cu). The melting point of the first metal used in the method disclosed herein is lower than the melting point of the second metal or alloy from which the first metal is to be separated. In the embodiments disclosed herein, the melting point of copper is about 1085°C.

[0029] The term "second metal or alloy," as used herein, is not particularly limited and should be understood or determined by one skilled in the art. In one embodiment, by way of example and not limitation, the second metal or alloy is steel. Steel is an alloy made from iron with added carbon and other elements. Because steel is an alloy, its melting point can vary depending on the elements present in the alloy and may range from 1200°C to 1540°C. In one embodiment, by way of example and not limitation, the steel is scrap steel that has copper entangled with the steel and that may not be easily separated manually.

[0030] The heating step, as disclosed herein with respect to the first aspect of this specification, involves heating the first metal and the second metal or alloy to a temperature close to the melting point of the first metal but below the melting point of the second metal or alloy. The heating step is performed to allow the first metal to react under conditions selected for the specific first metal and overall process design. In a first embodiment, the heating step is performed using resistive heating, as disclosed herein. In a second embodiment, the heating step is performed using direct resistive heating, as disclosed herein.

[0031] The basic principle of resistance heating is that when an electric current passes through a resistance, the power lost appears as heat. In other words, a material has a certain resistance that resists or hinders the flow of current through it. Thus, there is an electrical loss in the resistor that is dissipated as heat. There are two types of resistance heating, direct resistance heating and indirect resistance heating. In one embodiment, direct resistance heating is used to separate copper from scrap steel, as disclosed herein.

[0032] In direct resistance heating, an electric current passes through the material to be heated (the first metal and the second metal or alloy). In direct resistance heating, the material acts as the medium to complete the circuit. The resistance of the material to the flow of current produces Ohmic losses (I 2 R), thereby causing the material to heat. In one embodiment, for example and without limitation, direct resistance heating is performed by inserting graphite electrodes at each end of the scrap steel in a closed system and passing an electric current through the material to produce a voltage drop based on the resistance of the scrap steel containing copper. This voltage drop produces heat, with higher resistance producing more energy. A schematic of the method is shown in FIG. 1. To the best of the inventors’ knowledge, this method of heating has not been used in the steel industry before; however, the type of furnace required for this method is similar to an Acheson furnace used to make graphite. Thus, in one embodiment, direct resistance heating is used to separate copper from scrap steel using the method steps disclosed in the various aspects herein. Figure 1

[0033] The temperature to which the first metal and the second metal or alloy are heated should be close to the melting point of the first metal, but below the melting point of the second metal or alloy. Heating to this temperature allows the first metal to preferentially react with the halogen gas, while the second metal or alloy remains substantially unreacted compared to the first metal. Additionally, avoiding reaching the melting point of the second metal or alloy can help avoid alloying of the first metal with the second metal or alloy. In one embodiment, for example and without limitation, the scrap steel containing copper (the first metal) is heated to a temperature of about 900 °C to about 1,500 °C, and all values and ranges therebetween. In a second embodiment, for example and without limitation, the scrap steel containing copper (the first metal) is heated to a temperature of about 1,000 °C to about 1,200 °C, and all values and ranges therebetween. In a third embodiment, for example and without limitation, the scrap steel containing copper (the first metal) is heated to a temperature of about 1,000 °C to about 1,150 °C, and all values and ranges therebetween. In a fourth embodiment, for example and without limitation, the scrap steel containing copper (the first metal) is heated to a temperature of about 1,050 °C to about 1,150 °C, and all values and ranges therebetween. ​

[0034] The step of reacting the first metal with a halogen gas to form a metal halide is not particularly limited and should be known to one skilled in the art or can be determined. In one embodiment, for example and without limitation, the reaction is performed in a reaction chamber comprising the first metal and the second metal or alloy. In one embodiment, for example and without limitation, the halogen gas is chlorine (CI2) or bromine (Br2). In further embodiments, for example and without limitation, the ratio of halogen gas to first metal is about 0.01 : 1 to 1 : 1, 1 : 1 to 10: 1, 1 : 1 to 3: 1, and all values and ranges therebetween. In particular embodiments, the ratio of halogen gas to first metal is about 10: 1, 9: 1, 8: 1, 7: 1, 6: 1, 5: 1, 4: 1, 3: 1, 2: 1, 1 : 1, 0.9: 1, 0.8: 1, 0.7: 1, 0.6: 1, 0.5: 1, 0.4: 1, 0.3: 1, 0.2: 1, 0.1 : 1, 0.09: 1, 0.08: 1, 0.07: 1, 0.06: 1, 0.05: 1, 0.04: 1, 0.03: 1, 0.02: 1, or 0.01 : 1.

[0035] In another embodiment, for example and without limitation, the halogen gas is introduced into the reaction chamber via an inlet along with a carrier gas. In one embodiment, for example and without limitation, the carrier gas is air or nitrogen. In further embodiments, for example and without limitation, the ratio of carrier gas to halogen gas is about 5: 1 to about 100: 1, and all values and ranges therebetween. In particular embodiments, the ratio of carrier gas to halogen gas is about 10: 1, 15: 1, 20: 1, 25: 1, 30: 1, 35: 1, 40: 1, 45: 1, 50: 1, 55: 1, 60: 1, 65: 1, 70: 1, 75: 1, 80: 1, 85: 1, 90: 1, or 95: 1.

[0036] A halogen gas can be introduced into a reaction chamber containing the first metal and the second metal or alloy to react with the first metal to form a metal halide. In one embodiment, for example and without limitation, the reaction conditions are selected such that the residence time of the halogen gas in the reaction chamber (or reactor) used to perform the step of reacting the first metal with the halogen gas to form the metal halide is about 2 to about 60 minutes, and all values and ranges therebetween. In a second embodiment, for example and without limitation, the reaction conditions are selected such that the residence time of the halogen gas in the reaction chamber (or reactor) used to perform the step of reacting the first metal with the halogen gas to form the metal halide is about 10 to about 45 minutes, and all values and ranges therebetween. In a third embodiment, for example and without limitation, the reaction conditions are selected such that the residence time of the halogen gas in the reaction chamber (or reactor) used to perform the step of reacting the first metal with the halogen gas to form the metal halide is about 15 to about 30 minutes, and all values and ranges therebetween.

[0037] The reaction can be performed, for example and without limitation, under conditions in which the formed metal halide is in the form of a gas phase and the second metal or alloy is in the form of a solid phase. Such conditions can vary depending on the first metal and the second metal or alloy, and should be known or can be determined by one skilled in the art. In one embodiment, for example and without limitation, in the case where the first metal is copper and the second metal or alloy is steel, the pressure and / or temperature of the reaction conditions can be selected such that the formed copper halide is in the form of a gas phase, which can more easily separate the copper halide from the steel, as the formed gaseous copper halide will exit the reaction chamber with the halogen gas and / or carrier gas.

[0038] The step of separating the metal halide from the second metal or alloy is not particularly limited. In one embodiment, for example and without limitation, copper (as the first metal) is reacted with chlorine gas or bromine gas in the reaction chamber to form copper (II) chloride (CuCl2) or copper (II) bromide (CuBr2), respectively. In such embodiments, the reaction conditions (temperature and pressure) can be selected to allow the formation of copper (II) chloride (CuCl2) or copper (II) bromide (CuBr2) in the gas phase, such that a carrier gas can be used to remove the copper (II) chloride (CuCl2) or copper (II) bromide (CuBr2) to exit the reaction chamber from the outlet of the reaction chamber.

[0039] In one embodiment, the methods disclosed herein include recycling a halogen gas used to react with a first metal to form a metal halide. In further embodiments, for example and without limitation, the metal halide formed in the reaction (e.g., copper chloride or copper bromide) is separated from the second metal or alloy (scrap steel) and removed from the reaction chamber via an outlet in the reaction chamber carried by a carrier gas. The separated metal halide can undergo a separate reaction to convert the separated metal halide to the separated first metal and reformed halogen gas. In one embodiment, for example and without limitation, a molten salt electrolysis can be used to convert the separated metal halide to the separated first metal and reformed halogen gas. The reformed halogen gas can be recycled back to the reaction chamber for further reaction with the first metal.

[0040] In a second aspect according to the present description, a system for separating a first metal from a second metal or alloy is disclosed, wherein the melting point of the first metal is lower than the melting point of the second metal or alloy, the system comprising:

[0041] heating the first metal and the second metal or alloy to a temperature close to the melting point of the first metal but below the melting point of the second metal or alloy;

[0042] reacting the first metal with a halogen gas to form a metal halide;

[0043] separating the metal halide from the second metal or alloy;

[0044] reacting the metal halide to reform the first metal and the halogen gas; and

[0045] recycling the halogen gas.

[0046] The system disclosed in the second aspect according to the present description includes the steps and process conditions of the first aspect of the method disclosed above, as well as the step and process conditions of recycling the halogen gas as described above.

[0047] Figure 1Embodiments of the first and second aspects of the present description are shown in which scrap steel (second metal or alloy) (10) is treated (or pre-treated to purify the steel) in a reaction chamber (12) to remove copper (first metal). The scrap steel (10) is loaded into the reaction chamber (12). The reaction chamber (12) is connected to a halogen gas supply (14) and a carrier gas (not shown). An electrode (16) is electrically connected to the scrap steel (10) in which a direct heating resistance allows the reaction chamber to be heated to 400-1,300 °C to cause the copper to react with the halogen gas to form copper halide which can be carried away (20) from the reaction chamber (12) by the carrier gas, thereby separating the copper from the scrap steel (10). The separated scrap steel can then be directed to an electric arc furnace (EAF) (18) for further processing and purification. The process of the EAF (18) is not particularly limited and should be known to the person skilled in the art. In the EAF (18), the separated steel can be treated using an electric arc at a temperature of up to about 1,650 °C.

[0048] In a third aspect, the present description relates to a method for separating a first metal from a second metal or alloy, wherein the melting point of the first metal is lower than the melting point of the second metal or alloy, the method comprising the steps of:

[0049] heating the first metal and the second metal or alloy to a temperature below the melting point of the first metal;

[0050] exposing the first metal to a gas, thereby allowing the formation of a brittle first metal; and

[0051] separating the brittle first metal from the second metal or alloy.

[0052] The heating step as disclosed herein in relation to the third aspect of the present description relates to heating the first metal and the second metal or alloy to a temperature below the melting point of the first metal to form a brittle first metal. The inventors have found that the heating rate and the selected atmosphere of the scrap metal can influence the level of brittleness of copper relative to steel and thus the removal of copper from scrap steel. This property of selective or preferential brittleness of the first metal relative to the second metal or alloy under certain heating rate and / or atmosphere conditions can be exploited when separating the first metal (impurity) from the second metal or alloy of interest. Thus, by selecting the heating rate and / or atmosphere conditions, copper can be made to preferentially brittle over steel. This is due to the copper preferentially reacting over steel. In one embodiment, the reaction is such that copper preferentially oxidizes over steel, which makes it easy to separate from the steel.

[0053] As broadly described above, the heating rate can be selected to allow copper to preferentially embrittle the steel and minimize reaction with the steel, depending on the composition of the copper-containing scrap steel. In one embodiment, for example and without limitation, the copper-containing scrap steel is rapidly heated to achieve copper preferential embrittlement of the steel. In a second embodiment, for example and without limitation, the scrap steel is heated at a rate of at least about 30 °C / min. In a third embodiment, for example and without limitation, the scrap steel is heated at a rate of about 35 °C / min, 40 °C / min, 45 °C / min, 50 °C / min, 55 °C / min, 60 °C / min, 65 °C / min, 70 °C / min, 75 °C / min, 80 °C / min, 85 °C / min, 90 °C / min, 95 °C / min, or 100 °C / min.

[0054] In one embodiment, the copper-containing scrap steel is heated to allow the copper to preferentially react (e.g., oxidize) with the scrap steel, thereby embrittling the copper. It has been found that direct heating (as with a gas burner, which affects the volume of gas and the oxidation state of the gas) or indirect heating (which heats through a barrier and takes a long time to heat and results in significant electrical costs) results in copper alloying with the steel, thereby making it more difficult to remove. By selecting a heating method that avoids copper alloying with the scrap steel, the copper can be embrittled, thereby making it easier to separate. One non-limiting example of such a heating method is resistance heating. For example and without limitation, another method involves direct resistance heating.

[0055] In a first embodiment, the heating step is performed using resistance heating, as disclosed herein, as described above. In a second embodiment, the heating step is performed using direct resistance heating, as disclosed herein, as described above. In a third embodiment, for example and without limitation, the copper-containing scrap steel (second metal or alloy) is heated to a temperature of about 500 °C to about 1,000 °C, and all values and ranges therebetween. In a fourth embodiment, for example and without limitation, the copper-containing scrap steel (second metal or alloy) is heated to a temperature of about 600 °C to about 900 °C, and all values and ranges therebetween. The selected temperature is below the melting point of copper to inhibit copper alloying with the steel.

[0056] The heating time of the scrap steel and copper is not particularly limited and can vary depending on the design and application requirements; however, care should be taken to avoid alloying of the copper with the steel, and the heating time should be consistent with the tapping to tapping time in an electric arc furnace (EAF) operation in which the steel is further processed. In one embodiment, for example and without limitation, the heating time of the scrap steel and copper is from about 5 to about 30 minutes, and all values and ranges therebetween. In a second embodiment, for example and without limitation, the heating time of the scrap steel and copper is from about 10 to about 25 minutes or from about 15 to about 20 minutes, and all values and ranges therebetween. In a third embodiment, for example and without limitation, the heating time of the scrap steel and copper is at most about 30 minutes.

[0057] In one embodiment, the atmosphere of the reaction chamber used to perform the heating can be controlled to allow preferential embrittlement of the copper. In a further embodiment, for example and without limitation, the method is performed in an atmosphere containing one or more of the following: air, enriched air containing up to 100% oxygen (O2), nitrogen (N2), carbon monoxide (CO), carbon dioxide (CO2), chlorine (CI2), and bromine (Br2). In a still further embodiment, for example and without limitation, the partial pressure, flow rate, oxygen or halogen supply causing embrittlement of the reaction gas can be controlled to allow preferential embrittlement of the copper relative to the steel. Controlling the reactive gas as described above allows the non-copper (i.e., steel or iron) to not react, to react minimally, or to react less than the ratio of copper to steel, and can aid in the preferential embrittlement of copper over steel. Under such conditions, the extent of the reaction of the reactive gas with the copper is higher than the steel, or the ratio of copper to steel, and results in preferential embrittlement of the copper over the steel.

[0058] The term “embrittlement” as used herein is not particularly limited and should be known or understood by one of skill in the art. In one embodiment, for example and without limitation, embrittlement involves preferential reaction of oxygen with copper relative to steel. In a particular embodiment, for example and without limitation, oxygen can be present in the copper. In another embodiment, for example and without limitation, embrittlement results in a significant decrease in the ductility of the copper, which causes the copper to become a powder under light to moderate agitation and / or milling.

[0059] Various factors influence the embrittlement of a metal. These factors include heat capacity, gas solubility, and thermal conductivity. Based on the differences in these factors of the first metal and the second metal or alloy, temperature and pressure conditions can be selected to allow preferential embrittlement of the first metal over the second metal or alloy. Once embrittled, the first metal can be more easily separated from the second metal or alloy.

[0060] The step of separating the embrittled first metal from the second metal or alloy is not particular and can vary depending on design and application requirements. After heating the first metal and the second metal or alloy under conditions for embrittlement of the first metal (e.g., copper), the first metal and the second metal or alloy can be shaken, stirred, lightly ground, or vibrated to separate the first metal from the second metal or alloy.

[0061] Embodiments of the third aspect are further described. In the described embodiments, the steel will be heated directly with electricity (AC or DC) in a sealed cell that can be compressed at either end by electrode plates to ensure the scrap steel is in contact throughout the heating time. Heat will be generated by the material electrical resistance and radiative heat transfer from the material to the surrounding environment of the reactor. The steel can be rapidly heated to several hundred degrees below the melting point of copper. This promotes embrittlement of the copper during the rapid heating while maintaining control of the atmosphere and preventing alloying with the steel. The focus of the copper removal is the wire that is somehow attached to the scrap steel. Larger pieces of copper can typically be hand picked or removed by eddy currents. Once heated, the charge is shaken / vibrated and the smaller embrittled solids will be collected from the bottom of the heater. The hot charge can then be moved to an EAF for melting. The heating chamber can be designed in a way that maintains the temperature of the steel as needed, such as by using EAF exhaust gases as an energy source to maintain the temperature of the chamber.

[0062] The embrittled solids can then be physically separated from the steel while still in the reactor or immediately after transport to the EAF. One way to accomplish this is to vibrate or shake the reactor during or after heating. Another way is to use vibration during the material transport but need to preserve the heat. The solids are collected after transport or via an opening at the bottom of the chamber.

[0063] The atmosphere can be a combination of air, nitrogen, CO2, and chlorine. The inventors have found that rapid heating of the steel preferentially embrittles the copper without significantly oxidizing the steel.

[0064] When introducing elements of the present disclosure, the articles "a," "an," "the" and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," containing" and "having" are intended to be open-ended terms.

[0065] The term "comprising," as used in this document, is meant to be open-ended, specifying the presence of stated features, elements, components, groups, integers, and / or steps, but does not exclude the presence of other unstated features, elements, components, groups, integers, and / or steps. The foregoing also applies to words having similar meanings, such as "including," "having," and their derivatives. It will be understood that any described embodiment that "comprises" certain components is also a "consisting" embodiment that "consists" of those components, and a "consisting essentially of" embodiment that "consists essentially of" those components, where "consisting" has a closed or limiting meaning and "consisting essentially of" means including the components listed, but also including other components not listed, provided that other components do not materially alter the technical effect of the described technical effect.

[0066] It will be understood that any component included herein, whether specified or not, can be expressly excluded from the claimed application by the use of a negative limitation, such as any specific compound or method step as implicitly or explicitly defined herein.

[0067] Additionally, all ranges recited herein include the endpoints and any intermediate ranges.

[0068] Finally, as used herein the degree terms "substantially," "about," and "approximately" mean an acceptable quantity that one of ordinary skill in the art includes in considering a reflection of the word they modify, without significant change or modification of the end result. These degree terms should be interpreted to include at least ±5% of the modified term.

[0069] The abbreviation, "e.g." is derived from the Latin exempli gratia, and is used herein to indicate a non-limiting example. Consequently, the abbreviation "e.g." is synonymous with the term "for example." The word "or" is intended to mean either or both of the words that it connects, unless the context clearly indicates otherwise.

[0070] The phrase "at least one of" followed by a list of two or more items, means one or more of the listed items. The phrase "at least one of" is followed by a list of two or more items. For example, "at least one of A, B, and C" means A or B or C or any combination thereof (e.g. A+B, A+C, B+C, or A+B+C). The phrase "one or more of" followed by a list of two or more items, means one, two, three, four, or five or more of the listed items. The phrase "one or more of" is followed by a list of two or more items. For example, "one or more of A, B, and C" means A or B or C or any combination thereof (e.g. A+B, A+C, B+C, or A+B+C).

[0071] Example

[0072] Example 1 : Experimental Set-up and Methods

[0073] To test the effectiveness of copper removal by halogenation, reactive gas experiments were performed. Scrap steel was heated by loading (0.5 wt. % copper wiring) steel into a crucible enclosed in a reactor tube. The top of the reactor contained a gas inlet for air or N2, CO, and CO2 (if applicable) and halogen gas (CI2 or Br2). A gas lance was connected to the gas inlet to feed the gas from the bottom of the sample. An exhaust line was connected to capture the solids of the reaction.

[0074] After the tests were completed, the steel charge was removed from the reactor and melted. The melted sample was taken and analyzed for elemental Cu and Fe content.

[0075] It is worth noting that the furnace used for these experiments heated the steel using indirect resistance heating, where electricity was passed through resistance heating coils outside the reactor tube. The high resistance of these coils converted the electricity into heat, which was transferred to the steel in the reactor tube by radiation.

[0076] For this technology, the use of a heating method is required, regardless of the use or release of carbon. Passing electricity through the steel can be heated sufficiently to melt the copper. However, the use of electric heating in any capacity (i.e., direct or indirect resistance heating, or another form of heat production that does not use carbon as a fuel) is an embodiment of the technology.

[0077] Results

[0078] Table 1 provides a summary of all test conditions and copper removal results in percent form. The different variables listed include the atmosphere type (i.e., inert or oxidizing), the halogen to copper ratio (on a molar basis), and the test duration. The different operating conditions in these tests are listed as follows:

[0079] Halogen: CI2 or Br2

[0080] Copper content: 0.5 wt. %

[0081] Stoichiometric ratio of halogen to copper: 1 : 1 to 3: 1

[0082] Ratio of carrier gas to halogen: 10: 1, 20: 1

[0083] Residence time: 15-30 minutes

[0084] Temperature: 1050-1200 °C, but the selective melting window for Cu is between ~ 1100-1500 °C

[0085] CO:CO2 ratio: 10%

[0086] Table 1 Summary of test conditions and copper removal results for completed chlorination and bromination tests.

[0087]

[0088]

[0089] * indicates testing without halogen (air only).

[0090] *** indicates testing was performed below the melting point of copper (~1050°C)

[0091] The results of Table 1 show that copper is removed using halogen gases. Additionally, the use of inert atmospheres (nitrogen) and chlorine can significantly remove copper from scrap steel.

[0092] Example 2 :

[0093] Metal charges consisting of copper and steel wire of varying thicknesses were prepared for heating experiments. The thickness of the wire was between 8-18 AWG, compressed vertically between two stainless steel rods welded to steel plates, each connected to a power supply through copper leads. Between these steel plates was the metal sample, sealed in an insulated ceramic reactor (suitable for lab-scale testing, but commercial reactors would have a different construction of materials). Multiple gas inlet lines were placed at the bottom of the vertical reactor to achieve maximum residence time of the gas and enhanced gas / solid contact.

[0094] Once the power supply was turned on, gas flow was initiated for the specified time. The metal charge was heated in the 10-30 minute time range, and the reactor interior temperature was brought from room temperature to 500-1000°C. An input voltage of 1-8V and a current of 0-300A was used (sufficient for charge sizes in the hundreds of grams - charge sizes in the tonnage scale would require much higher power).

[0095] Once cooled, the metal was removed from the reactor. Characterization of the embrittlement effect of the present invention was done by shaking and / or grinding to disintegrate the brittle copper from the steel and collected by gravity.

[0096] The following are examples of test conditions.

[0097] In an oxidizing atmosphere, steel in the hundreds of grams was heated to 500-800°C in 30 minutes with air flow starting at room temperature at 200 mL / min, and the copper embrittlement resulting from the rapid heating and oxidation was evaluated after the duration of the test.

[0098] In an inert atmosphere, steel in the hundreds of grams was heated to 500-800°C in 30 minutes with N2 flow starting at room temperature at 200 mL / min, and the copper embrittlement resulting from the rapid heating without oxidation was evaluated after the duration of the test.

[0099] Clause

[0100] 1. A method for separating a first metal from a second metal or alloy, wherein the melting point of the first metal is lower than the melting point of the second metal or alloy, the method comprising the steps of:

[0101] heating the first metal and the second metal or alloy to a temperature close to the melting point of the first metal but below the melting point of the second metal or alloy;

[0102] reacting the first metal with a halogen gas to form a metal halide; and

[0103] separating the metal halide from the second metal or alloy.

[0104] 2. The method of clause 1, wherein electrical heating is performed to heat the first metal and the second metal or alloy.

[0105] 3. The method of clause 1 or 2, wherein the electrical heating is performed by direct resistance heating.

[0106] 4. The method of any one of clauses 1 to 3, wherein the first metal is copper.

[0107] 5. The method of any one of clauses 1 to 4, wherein the second metal or alloy is steel.

[0108] 6. The method of any one of clauses 1 to 5, wherein the heating step is performed to a temperature of about 900 °C to about 1500 °C.

[0109] 7. The method of any one of clauses 1 to 5, wherein the heating step is performed to a temperature of about 1000 °C to about 1200 °C.

[0110] 8. The method of any one of clauses 1 to 7, wherein the halogen gas is chlorine or bromine.

[0111] 9. The method of any one of clauses 1 to 8, wherein the formed metal halide is in the form of a gas phase and the second metal or alloy is in the form of a solid phase, the method further comprising the step of removing the gas phase containing the metal halide to separate the metal halide from the second metal or alloy.

[0112] 10. The method of any one of clauses 1 to 9, wherein after separating the metal halide, the method further comprises the step of reacting the metal halide to separate the first metal from the second metal or alloy and reform the halogen gas.

[0113] 11. The method according to clause 10, further comprising the step of recycling the halogen gas.

[0114] 12. The method of any one of clauses 1 to 11, wherein the ratio of the halogen gas to the first metal is from about 1:1 to about 10:1.

[0115] 13. The method of any one of clauses 1 to 11, wherein the ratio of the halogen gas to the first metal is from about 1:1 to about 3:1.

[0116] 14. The method of any one of clauses 1 to 13, further comprising a carrier gas.

[0117] 15. The method of clause 14, wherein the carrier gas is air or nitrogen.

[0118] 16. The method of clause 14 or 15, wherein the ratio of the carrier gas to the halogen gas is from about 5:1 to about 100:1.

[0119] 17. The method of any one of clauses 1 to 16, wherein the residence time of the halogen gas in the reactor used to carry out the step of reacting the first metal with the halogen gas to form the metal halide is from about 10 to about 60 minutes.

[0120] 18. A system for separating a first metal from a second metal or alloy, wherein the first metal has a melting point lower than the melting point of the second metal or alloy, the system comprising:

[0121] heating the first metal and the second metal or alloy to a temperature close to the melting point of the first metal but below the melting point of the second metal or alloy;

[0122] reacting the first metal with a halogen gas to form a metal halide;

[0123] separating the metal halide from the second metal or alloy;

[0124] reacting the metal halide to reform the first metal and the halogen gas; and

[0125] The halogen gas is recycled.

[0126] 19. The system of clause 18, wherein electrical heating is performed to heat the first metal and the second metal or alloy.

[0127] 20. The system of clause 18 or 19, wherein the electrical heating is by direct resistive heating.

[0128] 21. The system of any one of clauses 18-20, wherein the first metal is copper.

[0129] 22. The system of any one of clauses 18-21, wherein the second metal or alloy is steel.

[0130] 23. The system of any one of clauses 18-22, wherein the heating step is conducted to a temperature of about 900 °C to about 1400 °C.

[0131] 24. The system of any one of clauses 18-23, wherein the heating step is conducted to a temperature of about 1000 °C to about 1200 °C.

[0132] 25. The system of any one of clauses 18-24, wherein the halogen gas is chlorine or bromine.

[0133] 26. The system of any one of clauses 18-25, wherein the formed metal halide is in the form of a gas phase and the second metal or alloy is in the form of a solid phase.

[0134] 27. The system of any one of clauses 18-26, wherein the ratio of the halogen gas to the first metal is about 1 : 1 to about 10: 1.

[0135] 28. The system of any one of clauses 18-27, wherein the ratio of the halogen gas to the first metal is about 1 : 1 to about 3: 1.

[0136] 29. The system of any one of clauses 18-28, further comprising a carrier gas.

[0137] 30. The system of clause 29, wherein the carrier gas is air or nitrogen.

[0138] 31. The system of clause 29 or 30, wherein the ratio of the carrier gas to the halogen gas is about 5: 1 to about 100: 1.

[0139] 32. The system of any one of clauses 18-31, wherein the residence time of the halogen gas in a reactor used to conduct the step of reacting the first metal with the halogen gas to form the metal halide is 10 to 60 minutes.

[0140] 33. A method for separating a first metal from a second metal or alloy, the method comprising the steps of:

[0141] heating the first metal and the second metal or alloy to a temperature below the melting point of the first metal;

[0142] exposing the first metal to a gas to form a brittle first metal; and

[0143] separating the brittle first metal from the second metal or alloy.

[0144] 34. The method of clause 33, wherein electrical heating is performed to heat the first metal and the second metal or alloy.

[0145] 35. The method of clause 33 or 34, wherein the heating step is performed using direct resistance heating.

[0146] 36. The method of any one of clauses 33 to 35, wherein the heating step has a minimum heating rate of about 30 °C / minute.

[0147] 37. The method of any one of clauses 33 to 36, wherein the heating step is performed for about 5 to about 30 minutes.

[0148] 38. The method of any one of clauses 33 to 37, wherein the method is performed in an atmosphere containing one or more of: air, enhanced air containing up to 100% oxygen, nitrogen (N2), carbon monoxide (CO), carbon dioxide (CO2), chlorine (CI2), and bromine (Br2).

[0149] 39. The method of any one of clauses 33 to 38, wherein the first metal is copper.

[0150] 40. The method of any one of clauses 33 to 39, wherein the second metal or alloy is steel.

[0151] 41. The method of any one of clauses 33 to 40, wherein the heating step is performed to a temperature of about 500 °C to about 1000 °C.

[0152] 42. The method of any one of clauses 33 to 41, wherein the atmosphere contains chlorine or bromine and heating the first metal forms a metal halide in a gas phase, the method further comprising a step of removing the gas phase containing the metal halide to separate the metal halide from the second metal or alloy.

[0153] 43. The method of clause 42, wherein after separating the metal halide, the method further comprises a step of reacting the metal halide to separate the first metal from the second metal or alloy and reforming the chlorine or the bromine.

[0154] 44. The method of clause 43, further comprising a step of recycling the chlorine or the bromine.

[0155] 45. The method of any one of clauses 33-44, wherein the first metal and the second metal or alloy are ground to separate the first metal from the second metal or alloy.

[0156] 46. The method of any one of clauses 33-45, wherein shaking, grinding, or tugging is performed to separate the first metal from the second metal.

[0157] 47. A method for making steel, the method comprising the method of any one of clauses 1-47.

[0158] 48. The method of clause 47, further comprising the step of directing the separated second metal or alloy into an electric arc furnace.

[0159] The above disclosure generally describes the application. A more complete understanding can be obtained by reference to the following examples. These examples are described for illustrative purposes and are not intended to limit the scope of the application. It is contemplated that variations and modifications might occur to those skilled in the art to which the present application pertains. Without further description, it is believed that one skilled in the art can, using the preceding description and illustrative examples, utilize the present application to its fullest extent. Accordingly, the working examples specifically indicate and describe the preferred aspects of the present application, and are not to be construed as limiting of the remainder of the disclosure in any way. Although specific terms are employed herein, such terms are intended in a descriptive sense and not for limitation.

[0160] All of the above publications, patents and patent applications herein incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety.

[0161] While the preferred embodiments of the application have been described above, it will be recognized and understood that numerous modifications can be made to the application and its alternative embodiments. If therefore, no limitation is intended by the foregoing description and illustration, and all such alternatives are considered within the scope of the application. Accordingly, the spirit and scope of the application should be judged in terms of the claims now appended and their equivalents.

Claims

1. A method for separating a first metal from a second metal or alloy, wherein the melting point of the first metal is lower than the melting point of the second metal or alloy, the method comprising the steps of: heating the first metal and the second metal or alloy to a temperature near the melting point of the first metal but below the melting point of the second metal or alloy; reacting the first metal with a halogen gas to form a metal halide; and separating the metal halide from the second metal or alloy.

2. The method of claim 1, wherein electrical heating is performed to heat the first metal and the second metal or alloy.

3. The method of claim 1 or 2, wherein the electrical heating is performed by direct resistance heating.

4. The method of any one of claims 1 to 3, wherein the first metal is copper.

5. The method of any one of claims 1 to 4, wherein the second metal or alloy is steel.

6. The method of any one of claims 1 to 5, wherein the heating step is performed to a temperature of about 900 °C to about 1500 °C.

7. The method of any one of claims 1 to 5, wherein the heating step is performed to a temperature of about 1000 °C to about 1200 °C.

8. The method of any one of claims 1 to 7, wherein the halogen gas is chlorine or bromine.

9. The method of any one of claims 1 to 8, wherein the formed metal halide is in the form of a gas phase and the second metal or alloy is in the form of a solid phase, the method further comprising the step of removing the gas phase containing the metal halide to separate the metal halide from the second metal or alloy.

10. The method of any one of claims 1 to 9, wherein after separating the metal halide, the method further comprises the step of reacting the metal halide to separate the first metal from the second metal or alloy and reform the halogen gas.

11. The method of claim 10, wherein the method further comprises the step of recycling the halogen gas.

12. The method of any one of claims 1 to 11, wherein the ratio of the halogen gas to the first metal is about 1:1 to about 10:

1.

13. The method of any one of claims 1 to 11, wherein the ratio of the halogen gas to the first metal is about 1:1 to about 3:

1.

14. The method of any one of claims 1 to 13, further comprising a carrier gas.

15. The method of claim 14, wherein the carrier gas is air or nitrogen.

16. The method of claim 14 or 15, wherein the ratio of the carrier gas to the halogen gas is about 5:1 to about 100:

1.

17. The method of any one of claims 1 to 16, wherein the residence time of the halogen gas in a reactor used to perform the step of reacting the first metal with the halogen gas to form the metal halide is about 10 to about 60 minutes.

18. A system for separating a first metal from a second metal or alloy, wherein the first metal has a lower melting point than the second metal or alloy, the system comprising: heating the first metal and the second metal or alloy to a temperature near the melting point of the first metal; reacting the first metal with a halogen gas to form a metal halide; separating the metal halide from the second metal or alloy; reacting the metal halide to reform the first metal and the halogen gas; and recycling the halogen gas.

19. The system of claim 18, wherein electrical heating is performed to heat the first metal and the second metal or alloy.

20. The system of claim 18 or 19, wherein the electrical heating is performed by direct resistance heating.

21. The system of any one of claims 18 to 20, wherein the first metal is copper.

22. The system of any one of claims 18 to 21, wherein the second metal or alloy is steel.

23. The system of any one of claims 18 to 22, wherein the heating step is performed to a temperature of about 900 °C to about 1400 °C.

24. The system of any one of claims 18 to 23, wherein the heating step is performed to a temperature of about 1000 °C to about 1200 °C.

25. The system of any one of claims 18 to 24, wherein the halogen gas is chlorine or bromine.

26. The system of any one of claims 18 to 25, wherein the formed metal halide is in the form of a gas phase and the second metal or alloy is in the form of a solid phase.

27. The system of any one of claims 18 to 26, wherein the ratio of the halogen gas to the first metal is about 1 : 1 to about 10:

1.

28. The system of any one of claims 18 to 27, wherein the ratio of the halogen gas to the first metal is about 1 : 1 to about 3:

1.

29. The system of any one of claims 18 to 28, further comprising a carrier gas.

30. The system of claim 29, wherein the carrier gas is air or nitrogen.

31. The system of claim 29 or 30, wherein the ratio of the carrier gas to the halogen gas is about 5: 1 to about 100:

1.

32. The system of any one of claims 18 to 31, wherein the residence time of the halogen gas in a reactor used to perform the step of reacting the first metal with the halogen gas to form the metal halide is 10 to 60 minutes.

33. A method for separating a first metal from a second metal or alloy, the method comprising the steps of: heating the first metal and the second metal or alloy to a temperature below the melting point of the first metal; exposing the first metal to a gas to form a brittle first metal; and separating the brittle first metal from the second metal or alloy.

34. The method of claim 33, wherein electrical heating is performed to heat the first metal and the second metal or alloy.

35. The method of claim 33 or 34, wherein the heating step is performed using direct resistance heating.

36. The method of any one of claims 33 to 35, wherein the heating step has a minimum heating rate of about 30 °C / minute.

37. The method of any one of claims 33 to 36, wherein the heating step is performed for about 5 to about 30 minutes.

38. The method of any one of claims 33 to 37, wherein the method is performed in an atmosphere containing one or more of: air, enhanced air containing up to 100% oxygen, nitrogen (N2), carbon monoxide (CO), carbon dioxide (CO2), chlorine (CI2), and bromine (Br2).

39. The method of any one of claims 33 to 38, wherein the first metal is copper.

40. The method of any one of claims 33 to 39, wherein the second metal or alloy is steel.

41. The method of any one of claims 33 to 40, wherein the heating step is performed to a temperature of about 500 °C to about 1050 °C.

42. The method of any one of claims 33 to 41, wherein the atmosphere contains chlorine or bromine, and heating the first metal forms a metal halide in gaseous form, the method further comprising a step of removing the gas phase containing the metal halide to separate the metal halide from the second metal or alloy.

43. The method of claim 42, wherein after separating the metal halide, the method further comprises a step of reacting the metal halide to separate the first metal from the second metal or alloy and reforming the chlorine or the bromine.

44. The method of claim 43, wherein the method further comprises a step of recycling the chlorine or the bromine.

45. The method of any one of claims 33 to 44, wherein the first metal and the second metal or alloy are ground to separate the first metal from the second metal or alloy.

46. The method of any one of claims 33 to 45, wherein shaking, milling, or troweling is performed to separate the first metal from the second metal.

47. A method for preparing steel, the method comprising the method of any one of claims 1 to 47.

48. The method of claim 47, wherein the method further comprises a step of directing the separated second metal or alloy into an electric arc furnace.

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