Description:TECHNICAL FIELD
The present disclosure is in the field of metallurgy and more specifically slag processing. Particularly, the present disclosure provides a method for processing of Ferrochrome (FeCr) slag to obtain extraction of values such as specific metals and/or alloys thereof. Further provided herein is a system for facilitating the said method.

BACKGROUND OF THE DISCLOSURE

In FeCr manufacturing, approximately, 1 to 1.2 ton of Ferrochrome (FeCr) slag is generated for one ton of FeCr metal produced through Submerged Arc Furnace (SAF) route. Post tapping, the metal is casted and subsequently converted into a marketable product. And the generated slag which is at 1650 deg. C at the time of tapping is cooled to room temperature by using high pressure water jet granulation technique. After this, the granulated room temperature slag is stored in an open yard. Due to lack of potential application, FeCr slag is often dumped on the ground. While there are various endeavours directed towards utilization of FeCr slag, the main obstacle in the utilization of FeCr slag is the formation of chromium hexavalent ions, which are carcinogenic in nature, when rainwater percolates and interacts with Cr in FeCr slag.
Presently known methods for the utilization of FeCr slag are characterized by drawbacks such as high operating cost, environmental issues associated with the hydrometallurgical processes, ?CO?_2 emission associated with the carbothermic reduction, and process kinetic and productivity problems.
Therefore, it is the need of the hour to explore and develop alternate and efficient ways to utilize FeCr slag. Further, to facilitate efficient utilization of FeCr slag in such applications, removal of metals such as Cr and Mg from the slag is essential and is a requirement to be addressed.

STATEMENT OF THE DISCLOSURE
Addressing the aforementioned need for a method for facilitating value extraction from Ferrochrome slag, the present disclosure provides a method for processing Ferrochrome slag for obtaining metal(s), said method comprising subjecting the Ferrochrome slag to vacuum reduction in presence of a reductant and fluxing agent at a temperature of at least about 1550°C to obtain the metal(s).
In some embodiments, the vacuum reduction is performed at a temperature ranging from about 1550°C to about 1950°C.
In some embodiments, the metal(s) is selected from a group comprising Mg, Fe, Si, Cr, Ni, Ca, alloys thereof and any combination thereof.
In some embodiments, the reductant is selected from a group comprising FeSi, Al, C, CaC2 or any combination thereof.
In some embodiments, the fluxing agent is CaO.
In some embodiments, the ratio between the Ferrochrome slag, the reductant and the fluxing agent ranges from about 1:0.16:0.0 to about 1:0.5:0.7.
In some embodiments, one or more of the Ferrochrome slag, the reductant and the fluxing agent are subjected to crushing and/or grinding. In some embodiments, one or more of the Ferrochrome slag, the reductant and the fluxing agent is subjected to drying and/or dehydration.
In some embodiments, the ferro-chromium and the reductant are subjected to crushing and/or grinding followed by drying at a temperature of about 150 deg. C to about 200 deg. C for about 2 hours to about 3 hours; wherein the fluxing agent is subjected to dehydration at a temperature of about 550 deg. C to about 600 deg. C for about 2 hours to about 3 hours; and wherein the dried Ferrochrome slag and the dried reductant are mixed with the dehydrated fluxing agent prior to the vacuum reduction.
In some embodiments, the vacuum reduction is conducted in a crucible; and wherein the Ferrochrome slag, the reductant and the fluxing agent are added sequentially or simultaneously into the crucible.
In some embodiments, the vacuum reduction is performed in the presence of an inert carrier gas.
In some embodiments, the inert carrier gas is Argon (Ar).
In some embodiments, the vacuum reduction is performed at a pressure of less than about 100mbar. In an exemplary embodiment, the vacuum reduction is performed at a pressure below about 1mbar, preferably ranging from about 0.1mbar to about 1mbar.

In some embodiments, the vacuum reduction is conducted for a period of about 45 minutes to about 75 minutes.
In some embodiments, the metal(s) is obtained in the form of fumes from the vacuum reduction of the Ferrochrome slag.
In some embodiments, the method of the present disclosure further comprises subjecting the fumes to condensation to obtain the metal in the form of a powder.
In some embodiments, the method of the present disclosure further comprises
crushing and/or grinding the Ferrochrome slag and the reductant;
drying the crushed or ground Ferrochrome slag and reductant at a temperature of about 150 deg. C to about 200 deg. C for about 2 hours to about 3 hours;
dehydrating the fluxing agent at a temperature of about 550 deg. C to about 600 deg. C for about 2 hours to about 3 hours;
mixing the dried Ferrochrome slag and reductant and the dehydrated fluxing agent at a ratio of about 1:0.16:0.0 to about 1:0.5:0.7 to obtain a reaction mixture;
subjecting the reaction mixture to vacuum reduction in an inert atmosphere at a temperature of at least about 1550°C, pressure of less than about 100mbar for about 45 minutes to about 75 minutes;
subjecting fumes from the vacuum reduction to condensation
to obtain the metal(s).
In some embodiments, obtained metal(s) is Magnesium.
In some embodiments, the Magnesium has purity ranging from about 55% to about 97 %.
In a non-limiting embodiment, efficiency of extraction of Mg from the Ferrochrome slag ranges from about 5% to about 90%, preferably about 65% to about 90%.
In some embodiments, the method further provides a remnant slag within the crucible, and a metal alloy settled at the bottom of the crucible.
In some embodiments, the metal alloy is an Fe-Cr-Si alloy.
In some embodiments, extraction efficiency of Cr from the Ferrochrome slag is more than about 98%, preferably more than about 99%.
In some embodiments, the present disclosure further provides a system (100) for processing Ferrochrome slag for obtaining metal(s), the system comprising:
a reaction chamber (3) having a crucible (4);
a condenser (8) fluidly connected to the reaction chamber;
wherein the reaction chamber is structured to receive Ferrochrome slag, reductant(s) and fluxing agent(s); and
wherein the condenser is configured to receive fumes generated in the reaction chamber as a result of heating the mixture of FeCr slag, reductant(s) and fluxing agent(s) in the crucible at a temperature of at least about 1550°C, and condense the fumes to obtain the metal(s).
In some embodiments, the reaction chamber (3) includes a power source (1) for heating the crucible (4) and a carrier gas inlet (2);
In some embodiments, the condenser comprises an Inconel adapted to increase residence time of the fumes in the condenser.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, where:

Figure 1 depicts a flow chart of the process of the present disclosure for values extraction from Ferrochrome slag.
Figure 2 depicts SEM-EDS analysis of the powder particles collected from the chamber.
Figure 3 depicts XRD pattern of the powder particles collected from the chamber.
Figure 4 depicts XPS pattern of the powder particles collected from the chamber.
Figure 5 depicts (a) schematic diagram of the system of the present disclosure; and (b) enlarged view of coil and crucible section of the coil and crucible setup (labeled as (3) inside reaction chamber); the dotted lines represent direction of the carrier gas, continuous arrows show the direction flow of the reaction products; arrows in both directions stemming from (1) and (13) depict the flow of water.

DETAILED DESCRIPTION OF THE DISCLOSURE
The present disclosure aims to provide a method and a system to extract values such as metals but not limited to Cr and Mg along with alloys comprising such metals from a Ferrochrome (FeCr) slag and allow utilization of the remaining slag in different commercial applications. More particularly, the present disclosure intends to extract Mg and Cr from high temperature FeCr slag at its taping temperature through a silicothermic route. Before defining the method and the system further, definitions of specific terms used throughout the present disclosure are set out below –

Definitions
As used herein, the term ‘Ferrochrome slag’ or ‘FeCr slag’ refers to waste material obtained from the manufacturing of high carbon ferrochromium alloy. This slag is formed as a liquid at 1700 °C and its main components are SiO2, Al2O3 and MgO. Additionally, it comprises chrome, ferrous/ferric oxides and CaO.
As used herein, the term ‘vacuum reduction’ refers to a reduction reaction in an interior pressure of a reaction chamber maintained below atmospheric pressure.
As used herein, the term ‘remnant slag’ refers to the slag that remains in the crucible after completion of the vacuum reduction reaction.
As used herein, the term ‘comprising’ when placed before the recitation of steps in a method means that the method encompasses one or more steps that are additional to those expressly recited, and that the additional one or more steps may be performed before, between, and/or after the recited steps. For example, a method comprising steps a, b, and c encompasses a method of steps a, b, x, and c, a method of steps a, b, c, and x, as well as a method of steps x, a, b, and c. Furthermore, the term ‘comprising’ when placed before the recitation of steps in a method does not (although it may) require sequential performance of the listed steps, unless the content clearly dictates otherwise. For example, a method comprising steps a, b, and c encompasses, for example, a method of performing steps in the order of steps a, c, and b, the order of steps c, b, and a, and the order of steps c, a, and b, etc.
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. The suffix ‘(s)’ at the end of any term in the present disclosure envisages in scope both the singular and plural forms of said term.
As used in this specification and the appended claims, the singular forms ‘a’, ‘an’ and ‘the’ includes both singular and plural references unless the content clearly dictates otherwise. The use of the expression ‘at least’ or ‘at least one’ suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results. As such, the terms ‘a’ (or ‘an’), ‘one or more’, and ‘at least one’ can be used interchangeably herein.
Numerical ranges stated in the form ‘from x to y’ include the values mentioned and those values that lie within the range of the respective measurement accuracy as known to the skilled person. If several preferred numerical ranges are stated in this form, of course, all the ranges formed by a combination of the different end points are also included.
The terms ‘about’ or ‘approximately’ as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, are meant to encompass variations of and from the specified value, such as variations of +/-10% or less, +/-5% or less, +/-1% or less, and +/-0.1% or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. It is to be understood that the value to which the modifier ‘about’ or ‘approximately’ refers is itself also specifically, and preferably, disclosed.
As used herein, the terms ‘include’, ‘have’, ‘comprise’, ‘contain’ etc. or any form said terms such as ‘having’, ‘including’, ‘containing’, ‘comprising’ or ‘comprises’ are inclusive and will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
As regards the embodiments characterized in this specification, it is intended that each embodiment be read independently as well as in combination with another embodiment. For example, in case of an embodiment 1 reciting 3 alternatives A, B and C, an embodiment 2 reciting 3 alternatives D, E and F and an embodiment 3 reciting 3 alternatives G, H and I, it is to be understood that the specification unambiguously discloses embodiments corresponding to combinations A, D, G; A, D, H; A, D, I; A, E, G; A, E, H; A, E, I; A, F, G; A, F, H; A, F, I; B, D, G; B, D, H; B, D, I; B, E, G; B, E, H; B, E, I; B, F, G; B, F, H; B, F, I; C, D, G; C, D, H; C, D, I; C, E, G; C, E, H; C, E, I; C, F, G; C, F, H; C, F, I, unless specifically mentioned otherwise.
Embodiments
As mentioned in the above section, the present disclosure is directed towards a method for processing Ferrochrome slag for obtaining metal(s), said method comprising subjecting the Ferrochrome slag to vacuum reduction in presence of reductant(s) and fluxing agent(s) at a temperature of at least about 1550°C to obtain the metal(s).
In a non-limiting embodiment, the Ferrochrome slag comprises (in wt%) about 29% to about 31% of SiO2, about 24% to about 27% Al2O3, about 22% to about 26% MgO, about 8% to about 11% Cr2O3, about 3% to about 4% Fe2O3 and about 3% to about 4% CaO.
In some embodiments, the vacuum reduction is conducted at a temperature ranging from about 1550°C to about 1950°C.
In some embodiments, the vacuum reduction is conducted at a temperature of about 1550°C, about 1600°C, about 1650°C, about 1700°C, about 1750°C, about 1800°C, about 1850°C, about 1900°C, about 1950°C.
In a non-limiting embodiment, one of the objectives of the invention is to utilize hot liquid slag in its liquid state itself. For keeping the FeCr slag at its liquid state (> 90 wt. % liquid fraction), the slag should ideally be maintained at at least about 1500 deg. C. However, to maintain sufficient fluidity, super heating above 1500 deg C is required. Accordingly, the present disclosure provides a method particularly characterized by vacuum reduction at a temperature of at least about 1550°C. In some
In a non-limiting embodiment, the heating for vacuum reduction of the Ferrochrome slag in presence of reductant(s) and fluxing agent(s) at a temperature of at least about 1550°C is achieved by electromagnetic means.
Thus, in some embodiments, provided herein in a method for processing Ferrochrome slag for obtaining metal(s), said method comprising subjecting the Ferrochrome slag to vacuum reduction in presence of reductant(s) and fluxing agent(s) at a temperature of at least about 1550°C to obtain the metal(s).
In some embodiments, the method is directed towards obtaining metal(s) is selected from a group comprising Mg, Fe, Si, Cr, Ni, Ca, alloys thereof and any combination thereof.
Thus, in some embodiments, provided herein is a method for processing Ferrochrome slag for obtaining metal(s) selected from a group comprising Mg, Fe, Si, Cr, Ni, Ca, alloys thereof and any combination thereof, said method comprising subjecting the Ferrochrome slag to vacuum reduction in presence of reductant(s) and fluxing agent(s) at a temperature of at least about 1550°C to obtain the metal(s).
In some embodiments, the method for processing Ferrochrome slag for obtaining metal(s) selected from a group comprising Mg, Fe, Si, Cr, Ni, Ca, alloys thereof and any combination thereof, comprises subjecting the Ferrochrome slag to vacuum reduction in presence of reductant(s) and fluxing agent(s) at a temperature of about 1550°C to about 1950°C to obtain the metal(s).
In some embodiments, the reductant is selected from a group comprising FeSi, Al, C, CaC2 or any combination thereof.
In some embodiments, the choice of fluxing agent includes but is not limited to CaO.
In some embodiments, provided herein is a method for processing Ferrochrome slag for obtaining metal(s) selected from a group comprising Mg, Fe, Si, Cr, Ni, Ca, alloys thereof and any combination thereof, said method comprising subjecting the Ferrochrome slag to vacuum reduction in presence of a reductant and fluxing agent at a temperature of at least about 1550°C to obtain the metal(s); wherein the reductant is selected from a group comprising FeSi, Al, C, CaC2 or any combination thereof; and/or wherein fluxing agent includes but is not limited to CaO.
In some embodiments, the method for processing Ferrochrome slag for obtaining metal(s) selected from a group comprising Mg, Fe, Si, Cr, Ni, Ca, alloys thereof and any combination thereof, comprises subjecting the Ferrochrome slag to vacuum reduction in presence of reductant(s) and fluxing agent(s) at a temperature about 1550°C to about 1950°C to obtain the metal(s); wherein the reductant is FeSi; and/or wherein fluxing agent is CaO.
In some embodiments, the ratio between the Ferrochrome slag, the reductant(s) and the fluxing agent(s) (in terms of weight) ranges from about 1:0.16:0.0 to about 1:0.5:0.7, including all ratios within the said range.
Without intending to be limited by theory, in some embodiments, the CaO in the slag may provide the required content of fluxing agent to facilitate the extraction of metal(s) from the Ferrochrome slag to a certain extent. Thus, taking into account the possibility of basing reliance on CaO in the slag as fluxing agent, the ratio between the Ferrochrome slag, the reductant(s) and the fluxing agent(s) ranges from about 1:0.16:0.0 to about 1:0.5:0.7.
However, to enhance the said effect, additional fluxing agent such as but not limited to CaO may be added to the slag. Thus, in some embodiments, the ratio between the Ferrochrome slag, the reductant(s) and the fluxing agent(s) over and above CaO in the slag (in terms of weight) ranges from about 1:0.16:0.18 to about 1:0.5:0.7, including any ratio falling within the said range.
In a non-limiting embodiment, the ratio between the Ferrochrome slag, the reductant(s) and the fluxing agent(s) (in terms of weight) is about 1:0.16:0.0, about 1:0.16:0.05, about 1:0.2:0.1, about 1:0.3:0.2, about 1:0.4:0.3, about 1:0.5:0.6, or about 1:0.5:0.7.
In some embodiments, one or more of the Ferrochrome slag, the reductant(s) and the fluxing agent(s) are subjected to crushing and/or grinding. In some embodiments, two or more of the Ferrochrome slag, the reductant(s) and the fluxing agent are subjected to crushing and/or grinding. In some embodiments, the Ferrochrome slag, the reductant(s) and the fluxing agent(s) are subjected to crushing and/or grinding.
In some embodiments, the crushing and/or grinding is performed prior to or after mixing of the Ferrochrome slag, the reductant(s) and the fluxing agent(s).
In an exemplary embodiment, Ferrochrome slag and the reductant are subjected to crushing and/or grinding prior to the mixing or blending of the Ferrochrome slag, the reductant and the fluxing agent for vacuum reduction.
In some embodiments, one or more of the Ferrochrome slag, the reductant(s) and the fluxing agent(s) is subjected to drying and/or dehydration.
In some embodiments, two or more of the Ferrochrome slag, the reductant(s) and the fluxing agent(s) are subjected to drying and/or dehydration.
In some embodiments, the drying and/or dehydration is performed prior to or after mixing of the Ferrochrome slag, the reductant(s) and the fluxing agent(s) and is optionally preceded or followed by crushing and/or grinding of one or more of the Ferrochrome slag, the reductant(s) and the fluxing agent(s).
In an exemplary embodiment, the Ferrochrome slag, the reductant(s) and the fluxing agent(s) are subjected to drying and/or dehydration prior to the mixing or blending of the components.
In some embodiments, one or more of the Ferrochrome slag, the reductant(s) and the fluxing agent(s) are subjected to one or more of crushing and/or grinding and, drying and/or dehydration. Said crushing, grinding, drying and/or dehydration may be performed on one or more of the ferro-chromium slag, the reductant and the fluxing agent individually, prior to mixing or post mixing in the ratios as defined above.
In some embodiments, the Ferrochrome slag and the reductant(s) are subjected to crushing and/or grinding followed by drying at a temperature of about 150 deg. C to about 200 deg. C for about 2 hours to about 3 hours.
In some embodiments, the fluxing agent is subjected to dehydration at a temperature of about 550 deg. C to about 600 deg. C for about 2 hours to about 3 hours.
In a non-limiting embodiment, the dried Ferrochrome slag, the reductant(s) and the dried reductant(s) are mixed with the dehydrated fluxing agent prior to the vacuum reduction.
In some embodiments, the vacuum reduction is conducted in a crucible. Said crucible, in some embodiments, is placed inside a reaction chamber. In a non-limiting embodiment, the crucible, in the reaction chamber, is in contact with a coil that allows heating of the crucible by electromagnetic means, more specifically relying on the principle of electromagnetic induction.
The Ferrochrome slag, the reductant(s) and the fluxing agent(s) may be added sequentially or simultaneously into the crucible. In some embodiments, the Ferrochrome slag, the reductant(s) and the fluxing agent(s) are added sequentially into the crucible. In some embodiments, the Ferrochrome slag, the reductant(s) and the fluxing agent(s) are added simultaneously into the crucible.
In some embodiments, the vacuum reduction is performed at a very low pressure, in the presence of an inert gas. The inert gas acts as carrier gas for carrying the evolved Mg vapours from the reaction crucible into the condenser.
In some embodiments, the inert gas employed in the method of the present disclosure includes but it not limited to Argon. In an exemplary embodiment, the inert gas is Argon.
In some embodiments, the inert gas is supplied into the reactor chamber at a rate of about 4L/min to about 7L/min, preferably about 5L/min.
In some embodiments, the inert gas is supplied into the reactor chamber at a rate of about 4L/min, about 5L/min, about 6L/min or about 7L/min.
In some embodiments, the vacuum reduction is performed at a pressure less than about 100mbar.
In some embodiments, the vacuum reduction is performed at a pressure ranging from about 0.1 mbar to about 99mbar.
In an exemplary embodiment, the vacuum reduction is performed at a pressure below about 1mbar, preferably ranging from about 0.1mbar to about 1mbar.
In some embodiments, the temperature for vacuum reduction as defined in the above embodiments is achieved by electromagnetic means. In some embodiments, the temperature for vacuum reduction is achieved by supplying power ranging from about 4.5kW to about 5.5kW, preferably about 5kW. In a non-limiting embodiment, the power is increased from about 2.5kW to about 5kW, with a step size of about 0.5kW.
In some embodiments, the vacuum reduction is conducted for a period of about 45 minutes to about 75 minutes.
Without intending to be restricted by theory, the vacuum reduction as described in the above embodiments leads to generation of fumes wherein said fumes comprise metal(s) such as but not limited to magnesium. Thus, in some embodiments, the heating of the contents of the crucible i.e. the Ferrochrome slag, the reductant(s) and the fluxing agent(s) is continued till the fume evolution stops.
In some embodiments, the fumes comprising metal(s) such as but not limited to magnesium are further subjected to condensation to facilitate deposition of magnesium on the walls of the reactor, passage from the reactor to a condenser and/or a condenser. In some embodiments, the carrier gas supplied into the reaction chamber aids in carrying the evolved metal(s) fumes into the condenser.
In some embodiments, the vacuum reduction leading to the evolution of the metal(s) fumes followed by condensation of the fumes occurs in tandem. Therefore, in a non-limiting embodiment, the total time taken for processing the Ferrochrome slag by vacuum reduction and condensation to yield metal(s) ranges from about 45 minutes to about 75 minutes.
In some embodiments, the method of the present disclosure comprises:
crushing and/or grinding the Ferrochrome slag and the reductant;
drying the crushed or ground Ferrochrome slag and reductant at a temperature of 150 deg. C to about 200 deg. C for about 2 hours to about 3 hours.;
dehydrating the fluxing agent at a temperature of 550 deg. C to about 600 deg. C for about 2 hours to about 3 hours;
mixing the dried Ferrochrome slag and reductant and the dehydrated fluxing agent at a ratio of about 1:0.16:0.0 to about 1:0.5:0.7 to obtain a reaction mixture;
subjecting the reaction mixture to vacuum reduction in an inert atmosphere at a temperature of at least about 1550°C, pressure of less than about 100mbar for about 45 minutes to about 75 minutes; and
subjecting metal contain fumes arising from the vacuum reduction to condensation
to obtain the metal(s).
In a non-limiting embodiment, the above method facilitates deposition of metal(s) such as but not limited to magnesium on the walls of the reactor, passage from the reactor to a condenser and/or a condenser. In some embodiments, the metal(s) such as but not limited to magnesium is recovered by scraping the walls of the reactor, passage from the reactor to the condenser and/or the condenser.
Accordingly, in some embodiments, the method of the present disclosure comprises:
crushing and/or grinding the Ferrochrome slag and the reductant;
drying the crushed or ground Ferrochrome slag and reductant at a temperature of 150 deg. C to about 200 deg. C for about 2 hours to about 3 hours.;
dehydrating the fluxing agent at a temperature of 550 deg. C to about 600 deg. C for about 2 hours to about 3 hours;
mixing the dried Ferrochrome slag and reductant and the dehydrated fluxing agent at a ratio of about 1:0.16:0.0 to about 1:0.5:0.7 to obtain a reaction mixture;
subjecting the reaction mixture to vacuum reduction in an inert atmosphere at a temperature of at least about 1550°C, pressure of less than about 100mbar for about 45 minutes to about 75 minutes;
subjecting metal contain fumes arising from the vacuum reduction to condensation to facilitate deposition of metal(s) on the walls of the reactor, passage from the reactor to the condenser and/or the condenser; and
scraping the walls of the reactor, passage from the reactor to the condenser and/or the condenser to obtain the metal(s).
In a non-limiting embodiment, the metal(s) is obtained in the form of a powder.
In some embodiments, the method of the present disclosure yields extracted in more than one form, apart from the condensed metal powder.
In some embodiments, the method of the present disclosure, as described above, yields one or more of the following three products: (1) metal(s) deposited on the walls of the reactor, passage from the reactor to the condenser and/or the condenser, (2) remnant slag within the crucible, and (3) metal settled at the bottom of the crucible.
In some embodiments, the method of the present disclosure, yields three products: (1) metal(s) deposited on the chamber and passages on the walls of the reactor, passage from the reactor to the condenser and/or the condenser, (2) remnant slag within the crucible, and (3) metal settled at the bottom of the crucible.
In an exemplary embodiment, the metal(s) deposited on the chamber and passages on the walls of the reactor, passage from the reactor to the condenser and/or the condenser is magnesium. In some embodiments, the magnesium is deposited on the chamber and passages on the walls of the reactor, passage from the reactor to the condenser and/or the condenser in the form of a powder. In some embodiments, the purity of Mg (wt. %) in this powder ranges from about 55 % to about 97 %.
In a non-limiting embodiment, efficiency of extraction of Mg from the Ferrochrome slag ranges from about 5% to about 90%, preferably about 65% to about 90%. Without intending to be limited by theory, the said extraction efficiency increases with decrease in the pressure in the reactor. In some embodiments, the remnant slag within the crucible comprises one or more of MgO.Al_2 O_3, (2)? SiO?_2. Al_2 O_3.(Mg,Ca)O, (3) SiO_2.(Mg,Ca)O, and (4) MgO at varying proportions.
In some embodiments, the remnant slag within the crucible comprises MgO.Al_2 O_3, (2)? SiO?_2. Al_2 O_3.(Mg,Ca)O, (3) SiO_2.(Mg,Ca)O, and (4) MgO at varying proportions.
In some embodiments, the metal settled at the bottom of the crucible includes but is not limited to an Fe-Cr-Si alloy. In a non-limiting embodiment, the Fe-Cr-Si alloy settled at the bottom of the crucible comprises about 10% to about 40% Fe, about 45% to about 60% Cr and about 5% to about 45% Si.
In a non-limiting embodiment, efficiency of extraction of Cr from the Ferrochrome slag is above about 98%, preferably above about 99%.
Accordingly, in some embodiments, provided herein is a method of extraction of magnesium (Mg) and chromium (Cr) from a Ferrochrome slag, said method comprising
crushing and/or grinding the Ferrochrome slag and the reductant;
drying the crushed or ground Ferrochrome slag and reductant at a temperature of 150 deg. C to about 200 deg. C for about 2 hours to about 3 hours.;
dehydrating the fluxing agent at a temperature of 550 deg. C to about 600 deg. C for about 2 hours to about 3 hours;
mixing the dried Ferrochrome slag and reductant and the dehydrated fluxing agent at a ratio of about 1:0.16:0.0 to about 1:0.5:0.7 to obtain a reaction mixture;
subjecting the reaction mixture to vacuum reduction in an inert atmosphere at a temperature of at least about 1550°C, pressure of less than about 100mbar for about 45 minutes to about 75 minutes;
subjecting metal contain fumes arising from the vacuum reduction to condensation to obtain the Mg in the form of a powder; and wherein the Cr is obtained in the form of an alloy settled at the bottom of the crucible in which the method is performed.
In some embodiments, provided herein is a method of extraction of magnesium (Mg) and chromium (Cr) from a Ferrochrome slag, said method comprising
crushing and/or grinding the Ferrochrome slag and the reductant;
drying the crushed or ground Ferrochrome slag and reductant at a temperature of 150 deg. C to about 200 deg. C for about 2 hours to about 3 hours.;
dehydrating the fluxing agent at a temperature of 550 deg. C to about 600 deg. C for about 2 hours to about 3 hours;
mixing the dried Ferrochrome slag, reductant and the dehydrated fluxing agent at a ratio of about 1:0.16:0.0 to about 1:0.5:0.7 to obtain a reaction mixture;
subjecting the reaction mixture to vacuum reduction in an inert atmosphere at a temperature of at least about 1550°C, pressure of less than about 100mbar for about 45 minutes to about 75 minutes;
subjecting metal contain fumes arising from the vacuum reduction to condensation to obtain the Mg in the form of a powder; and wherein the Cr is obtained in the form of an Fe-Cr-Si alloy settled at the bottom of the crucible in which the method is performed.
In some embodiments, the method is characterized by low CO_2 emission with good kinetics for efficient productivity.
Referring now to Figure 5 which illustrates a schematic view of a system (100) for processing Ferro-chromium slag for obtaining metal(s). The system (100) may broadly include a reaction chamber (3) and a condenser (8), which may be fluidly connected to each other. As seen in Figure 5 the reaction chamber may include a crucible (4) which may be structured to hold raw material such as Ferrochrome slag, reductant(s) and fluxing agent(s). In a non-limiting embodiment, the reaction chamber is an induction furnace.
In an embodiment, the reaction chamber (3) may include a power source (1) for heating the crucible (4) and a carrier gas inlet (2). In some embodiments, the power source comprises a coil support (17). In some embodiments, the power source is an AC power source attached with a transformer and supplies electrical energy to the coil. The coil, in some embodiments, is a water-cooled copper coil that facilitates holding the crucible setup and also generates electromagnetics to melt the materials. In some embodiments, a ceramic or alumina support is provided at the bottom of coil and crucible setup to provide thermal insulation and/or to avoid short circuiting.
In a non-limiting embodiment, the crucible is a graphite crucible (22), preferably cylindrical in shape, with a diameter of 7.5 cm and 15 cm height. In a non-limiting embodiment, the crucible is further surrounded by one or more layers. In some embodiments, the crucible is wrapped with graphite felt (19) and mica (18). In some embodiments, the mica forms the first outer layer of the crucible assembly and suppresses the arc generation between the graphite crucible and the coil. The graphite sheet, in some embodiments, is an intermediate layer and forms a layer between the graphite crucible and the outer mica layer.
Additionally, the reaction chamber (3) may include a charging hopper (6) for introducing raw materials, a pressure transmitter (5) and a radiation pyrometer (7) which are adapted to measure pressure variation within the reaction chamber (3) and measure temperature of the liquid raw materials inside the crucible (4), respectively. Further, the reaction chamber may comprise an inlet for the carrier gas (2), a thermocouple (9) for measuring temperature within the reactor.
Referring further to Figure 5, the condenser (8) that is fluidly connected to the reaction chamber may include an Inconel chamber (11) and collecting crucible (10) fixed at bottom of the Inconel chamber (11). The Inconel chamber (11) [thus, the condenser (8)] may be configured to receive fumes generated in the reaction chamber as a result of heating the mixture of FeCr slag, reductant(s) and fluxing agent(s) at a temperature of at least about 1550°C. The carrier gas supplied into the reaction chamber (3) may aid in carrying the evolved metal(s) fumes into the condenser (8). In an embodiment, the Inconel chamber (11) is a fixed Inconel impeller which may increases residence time within the condenser (8). Further, the condensed fumes in the condenser (8) may be collected in the collecting crucible (10), where the condensed fumes are in the form of a liquid or in the form of powder. Additionally, the system (100) may include dust collector (13) coupled to the collecting crucible (10) and a vacuum pump (15). The vacuum pump (15) may create the necessary vacuum in the passage from chamber up to condenser crucible and further, may create suction which may aid in transferring the dust generated during processing of the ferro-chromium slag for obtaining metal(s). The vacuum pump, in some embodiments, is connected to a throttle valve (14) to adjust the vacuum level within the chamber by adjusting percentage of the valve opening and further, a gas outlet from the vacuum pump (16) that is attached with the vacuum pump and may be used to exhaust sucked air into atmosphere.
In an embodiment, the system has low CO_2 emission with efficient kinetics thus enabling productivity.
In an embodiment, the foregoing descriptive matter is illustrative of the disclosure and not a limitation. Providing working examples for all possible combinations of optional elements in the slag employed as starting material and process parameters such as but not limiting to time and temperature of vacuum reduction within the range defined in the present disclosure, is considered redundant.

While the present disclosure is susceptible to various modifications and alternative forms, specific aspects thereof have been shown by way of examples and drawings and are described in detail below. However, it should be understood that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and the scope of the invention as defined by the appended claims.

EXAMPLES:

Example 1:
The experiment was performed in a 1 kg scale crucible. Table 1 characterizes the Ferrochrome slag employed as starting material.
Table 1: Chemical composition of FeCr slag in wt. %
SiO2 Al2O3 MgO Cr2O3 Fe2O3 CaO
31 25 24 11 4 3

Prior to mixing, the Ferrochrome slag and the FeSi (reductant) were subjected to crushing by a manual mortar and then subsequently drying at about 150 deg. C for about 2 hours. In parallel, CaO (fluxing agent) was subjected to dehydration at a temperature of about 550 deg. C, for about 2 hrs.

Post the drying and dehydration, the raw materials i.e. the Ferrochrome slag, the FeSi and the CaO were added to a graphite crucible at a ratio of about 1:0.2:0.7 and the crucible was placed inside the reaction chamber, in contact with a coil that held the crucible and created heat by electromagnetic means to melt the materials inside the crucible. The said coil setup consisted of main water-cooled copper coil. The following process parameters were maintained in the reaction crucible:
temperature above about 1550 deg C
pressure less than about 100 mbar, power up to about 5 kW, and
Ar gas flow of about 5 L/min

In parallel, the temperature of the condenser (connected to the reaction chamber – see Figure -5) was maintained at about 850 deg. C. The condenser comprised of a water-cooled pyrometer at the top of the condenser.
The vacuum reduction reaction was conducted till fumes stopped arising from the crucible. Once the vapor or fume evolution stopped, the power was switched off. However, Ar and vacuum application was made to continue until the temperature in the crucible reached 150 deg. C. The chamber was opened once crucible reached room temperature.
The vacuum reduction in the crucible and the condensation of the fumes arising therefrom yielded the following three products:
(1) deposited powder on the chamber and passages of the reactor ,
(2) remnant slag within the crucible, and
(3) metal settled at the bottom of the crucible.to facilitate deposition of from the walls of the condenser.

Example 2: Characterization of the obtained products
As mentioned in the previous example, the method of the present disclosure as shown in Example 1 led to formation of three products: (1) deposited powder on the chamber and passages of the module, (2) remnant slag within the crucible, and (3) metal settled at the bottom of the crucible. These were characterized as follows –
Deposited powder:
The collected powder in the crucible and chamber surface was scraped and collected. The colour of the powder (collected from chamber surface and condenser) was grey which resembled magnesium powder that is commercially available.
From the EDS analysis, the Mg (wt. %) in this powder was confirmed to be Mg having purity varying between about 58% and about 65 % (Figure 2). The extracted powder’s XRD pattern (Figure 3) partially matched with the Mg pattern (from Xpert plus database); the peak with 2theta value of 36.87 matched with Mg peaks from standard database. To re-confirm the presence of Mg, the powder was taken for XPS (Figure 4) which also confirmed the presence of Mg. The Mg peak was identified at 49.77 eV along with the peaks of MgO. All these analyses confirmed that the Mg powder was present along with MgO, which was possibly due to vacuum leak persisting in the chamber.
and (3) The remnant slag and metal settled at the bottom of the crucible:
The following phases were identified in the remnant slag in the crucible with the help of BSD image contrast and EDS analysis: (1) MgO.Al_2 O_3, (2)? SiO?_2. Al_2 O_3.(Mg,Ca)O, (3) ? SiO?_2.(Mg,Ca)O, and (4) MgO. These phases were found to be completely different when compared with the phases of FeCr slag which comprised (1) ?Mg_2 SiO?_4 and (2) ?MgAl_2 O?_4, except ?MgAl_2 O?_4.
Further, the settled Fe-Cr-Si alloy was analysed for its exact composition -
Table 2 characterizes the raw input FeCr slag composition along with post processing slag composition. The settled Fe-Cr-Si alloy composition is also presented in the Table 2.
Table 2: Composition of the input and processed slag with settled alloys composition
wt. % O Mg Al Si Ca Cr Fe
FeCr slag, pre-process 44.86 15.31 11.70 15.30 0.96 8.95 2.32
Post process remnant slag 51.60 10.58 10.36 13.74 13.72
Fe-Cr-Si alloy composition 42.46 45.57 11.97

Table 3 provides the extraction efficiency of Cr from the Ferrochrome slag as defined in Table 1 of Example 1. The table depicts high extraction efficiency (>99%) of Cr from the slag. Furthermore, the experiment confirms feasibility of extraction of Mg from Ferrochrome slag.
Table 3: Extraction efficiency of Cr from FeCr slag
Input raw materials (in g) Process Condition Extraction efficiency (in %)
FeCr slag (g) Fe-Si (g) CaO (g) T in deg. C P in mbar Cr (%)
120 25 85.2 >1550 <100 >99.0

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.

The foregoing description fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein, without departing from the principles of the disclosure.

Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
, Claims:
1) A method for processing Ferrochrome slag for obtaining metal(s), said method comprising subjecting the Ferrochrome slag to vacuum reduction in presence of a reductant and fluxing agent at a temperature of at least about 1550°C to obtain the metal(s).
2) The method as claimed in claim 1, wherein the vacuum reduction is performed at a temperature ranging from about 1550°C to about 1950°C.
3) The method as claimed in claim 1, wherein the metal(s) is selected from a group comprising Mg, Fe, Si, Cr, Ni, Ca, alloys thereof and any combination thereof.
4) The method as claimed in claim 1, wherein the reductant is selected from a group comprising FeSi, Al, C, CaC2 or any combination thereof.
5) The method as claimed in claim 1, wherein the fluxing agent is CaO.
6) The method as claimed in claim 1, wherein the ratio between the Ferrochrome slag, the reductant and the fluxing agent ranges from about 1:0.16:0.0 to about 1:0.5:0.7.
7) The method as claimed in claim 1, wherein one or more of the Ferrochrome slag, the reductant and the fluxing agent are subjected to crushing and/or grinding.
8) The method as claimed in claim 1, wherein one or more of the Ferrochrome slag, the reductant and the fluxing agent is subjected to drying and/or dehydration.
9) The method as claimed in claims 7 and 8, wherein the ferro-chromium and the reductant are subjected to crushing and/or grinding followed by drying at a temperature of about 150 deg. C to about 200 deg. C for about 2 hours to about 3 hours; wherein the fluxing agent is subjected to dehydration at a temperature of about 550 deg. C to about 600 deg. C for about 2 hours to about 3 hours; and wherein the dried Ferrochrome slag and the dried reductant are mixed with the dehydrated fluxing agent prior to the vacuum reduction.
10) The method as claimed in claim 1, wherein the vacuum reduction is conducted in a crucible; and wherein the Ferrochrome slag, the reductant and the fluxing agent are added sequentially or simultaneously into the crucible.
11) The method as claimed in claim 1, wherein the vacuum reduction is performed in the presence of an inert carrier gas.
12) The method as claimed in claim 11, wherein the inert carrier gas is Argon (Ar).
13) The method as claimed in claim 1, wherein the vacuum reduction is performed at a pressure of less than about 100mbar.
14) The method as claimed in claim 1, wherein the vacuum reduction is conducted for a period of about 45 minutes to about 75 minutes.
15) The method as claimed in claim 1, wherein the metal(s) is obtained in the form of fumes from the vacuum reduction of the Ferrochrome slag.
16) The method as claimed in claim 15, further comprising subjecting the fumes to condensation to obtain the metal in the form of a powder.
17) The method as claimed in claim 15, comprising:
crushing and/or grinding the Ferrochrome slag and the reductant;
drying the crushed or ground Ferrochrome slag and reductant at a temperature of about 150 deg. C to about 200 deg. C for about 2 hours to about 3 hours;
dehydrating the fluxing agent at a temperature of about 550 deg. C to about 600 deg. C for about 2 hours to about 3 hours;
mixing the dried Ferrochrome slag and reductant and the dehydrated fluxing agent at a ratio of about 1:0.16:0.0 to about 1:0.5:0.7 to obtain a reaction mixture;
subjecting the reaction mixture to vacuum reduction in an inert atmosphere at a temperature of at least about 1550°C, pressure of less than about 100mbar for about 45 minutes to about 75 minutes;
subjecting fumes from the vacuum reduction to condensation
to obtain the metal(s).
18) The method as claimed in any of claims 15 to 17, wherein the obtained metal(s) is Magnesium.
19) The method as claimed in claim 18, wherein the Magnesium has purity ranging from about 55% to about 97 %.
20) The method as claimed in claim 15, wherein the method further provides a remnant slag within the crucible, and a metal alloy settled at the bottom of the crucible.
21) The method as claimed in claim 20, wherein the metal alloy is Fe-Cr-Si alloy.
22) The method as claimed in claim 21, wherein extraction efficiency of Cr from the Ferrochrome slag is more than about 98%, preferably more than about 99%.
23) A system (100) for processing Ferrochrome slag for obtaining metal(s), the system comprising:
a reaction chamber (3) having a crucible (4);
a condenser (8) fluidly connected to the reaction chamber;
wherein the reaction chamber is structured to receive Ferrochrome slag, reductant(s) and fluxing agent(s); and
wherein the condenser is configured to receive fumes generated in the reaction chamber as a result of heating the mixture of FeCr slag, reductant(s) and fluxing agent(s) in the crucible at a temperature of at least about 1550°C, and condense the fumes to obtain the metal(s).
24) The system as claimed in claim 23, wherein the reaction chamber (3) includes a power source (1) for heating the crucible (4) and a carrier gas inlet (2);
25) The system as claimed in claim 23, wherein the condenser comprises an Inconel adapted to increase residence time of the fumes in the condenser.