System and method for immersion-based melting of aluminium metal and alloys

Abstract

A melting furnace can include a feeding unit configured to feed solid metal and a heating chamber for heating and maintaining molten metal. The heating chamber can include a plurality of immersion heaters, wherein each immersion heater is immersed in and heating the molten metal. The melting furnace can further include a. pump configured to circulate the molten metal from the heating chamber into a melting chamber and a melting chamber configured to receive the solid metal from the feeding unit and the molten metal from the heating chamber, wherein the solid metal submerges in the molten metal within the melting chamber and melts to create a liquid metal. The liquid metal can circulate from the melting chamber to the heating chamber.

Description

Attorney Docket No. 6474.028WO1 SYSTEMS AND METHODS FOR IMMERSION-BASED MELTING OF ALUMINUM METAL AND ALLOYS CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 63 / 584,705 entitled ^SYSTEMS AND METHODS FOR IMMERSION-BASED MELTING OF ALUMINUM METAL AND ALLOYS,^ filed September 22, 2023, the disclosure of which is incorporated herein in its entirety by reference. BACKGROUND OF THE DISCLOSURE

[0002] Furnaces, such as induction furnaces, are often used to melt metals and metal alloys. Melting such materials is a common step in preparation for certain automotive applications, such as high pressure die casting of structure parts. Induction furnaces use electric energy for melting but typically require a water- cooled copper coil immersed into the melted metal, as well as high voltage cables. Moreover, induction furnaces involve highly complex facilities, which can result in a larger footprint and entail frequent maintenance. SUMMARY OF THE DISCLOSURE

[0003] According to one aspect of the present disclosure, a melting furnace can include a feeding unit configured to feed solid metal; a heating chamber for heating and maintaining molten metal, where the heating chamber can include a plurality of immersion heaters and each immersion heater can be immersed in and heating the molten metal; a pump configured to circulate the molten metal from the heating chamber into a melting chamber; and the melting chamber configured to receive the solid metal from the feeding unit and the molten metal from the heating chamber. The solid metal can be submerged in the molten metal within the melting chamber and melts to create a liquid metal and the liquid metal can circulate from the melting chamber to the heating chamber.

[0004] In some examples, the feeding unit can include at least one of a walking floor, a vibro feeder, or a pusher unit to load the solid metal with controlled speed. In some examples, the melting chamber can include a recessed bathAttorney Docket No. 6474.028WO1 section for mixing the solid metal in the molten metal. In some examples, the melting chamber can include one or more radiant roof heaters configured to maintain a refractory of the melting chamber above a pre-defined temperature value. In some examples, the one or more radiant roof heaters can have a power of between 15 and 90 kilowatts and the pre-GHILQHG^WHPSHUDWXUH^YDOXH^LV^^^^^&^

[0005] In some examples, the melting chamber can include a first laser for monitoring a charge level of the solid metal; and a second laser for monitoring a height of the liquid metal. In some examples, the melting chamber can include a ramp, wherein the solid metal slides down the ramp and into the recessed bath. In some examples, the melting furnace can include a cleaning chamber for removing dross out of the liquid metal via porous plugs prior to the liquid metal entering the heating chamber. In some examples, the cleaning chamber can include one or more skim damns configured to collect dross from the liquid metal. In some examples, each of the plurality of immersion heaters can have a diameter of between 75 and 135 mm; and the plurality of immersion heaters can have a heating power of between 1000 and 3000 kilowatts.

[0006] According to another aspect of the present disclosure, a method of operating a melting furnace can include heating molten metal in a heating chamber via a plurality of immersion heaters contacting the molten metal; pumping a portion of the molten metal from the heating chamber to a melting chamber; feeding solid metal into the melting chamber; melting the solid metal by submerging, in the melting chamber, the solid metal in the portion of the molten metal to create a metal mixture; and circulating the metal mixture from the melting chamber to the heating chamber.

[0007] In some examples, feeding the solid metal into the melting chamber can include feeding the solid metal via at least one of a walking floor, a vibro feeder, or a pusher unit. In some examples, melting the solid metal can include submerging the solid metal in the portion of the molten metal in a recessed bath section of the melting chamber. In some examples, the method can include heating the melting chamber via one or more radiant roof heaters to maintain a refractory of the melting chamber above a pre-defined temperature value. In some examples, the one or more radiant roof heaters can have a power of between 15 and 90 kilowatts and the pre-GHILQHG^WHPSHUDWXUH^YDOXH^LV^^^^^&^Attorney Docket No. 6474.028WO1

[0008] In some examples, the method can include monitoring a charge level of the solid metal via a first laser; and monitoring a height of the metal mixture via a second laser. In some examples, feeding the solid metal into the melting chamber can include causing the solid metal to slide down a ramp and into the recessed bath. In some examples, the method can include filtering the metal mixture prior to the metal mixture entering the heating chamber. In some examples, filtering the metal mixture can include degassing the metal mixture via one or more porous plugs; and collecting dross from the metal mixture via one or more skim damns. In some examples, each of the plurality of immersion heaters can have a diameter of between 75 and 135 mm; and the plurality of immersion heaters can have a heating power of between 1000 and 3000 kilowatts. BRIEF DESCRIPTION OF THE FIGURES

[0009] Various objectives, features, and advantages of the disclosed subject matter can be more fully appreciated with reference to the following detailed description of the disclosed subject matter when considered in connection with the following drawings, in which like reference numerals identify like elements.

[0010] FIG. 1 is an immersion-based melting furnace according to some examples of the present disclosure.

[0011] FIG. 2 is a melting chamber from the immersion-based melting furnace of FIG. 1 according to some examples of the present disclosure.

[0012] FIG. 3 is a heating chamber from the immersion-based melting furnace of FIG. 1 according to some examples of the present disclosure.

[0013] FIG. 4 is an example method for operating an immersion-based melting furnace according to some examples of the present disclosure.

[0014] The drawings are not necessarily to scale, or inclusive of all elements of a system, emphasis instead generally being placed upon illustrating the concepts, structures, and techniques sought to be protected herein.Attorney Docket No. 6474.028WO1 DESCRIPTION

[0015] The following detailed description is merely exemplary in nature and is not intended to limit the claimed invention or the applications of its use.

[0016] Examples of the present disclosure are directed to systems and methods for immersion-based melting of aluminum metal and alloys, for example via an electric immersion-based melting furnace. The disclosed furnace utilizes various electric immersion heaters that operate based on resistant heating principles to heat up and maintain a bath of liquid metal, such as aluminum or other alloys. The liquid metal can be circulated into a separate chamber that receives solid metal to be melted. The liquid metal engulfs the solid metal, melting it, and the resulting mixture can be circulated back into the original chamber for heating via the immersion heaters. The disclosed examples provide various benefits, such as the ability to operate without processes cooling water or other complex utilities. Moreover, the footprint of the disclosed furnace is more compact than induction furnaces and entails less maintenance. In some examples, the disclosed furnace can, in the case of aluminum melting, melt up to three to ten metric tons of aluminum per hour. In addition, the configuration of the disclosed furnace enables easy cleaning and dross removal, which in turn can increase the service life of the unit and quality of the metal generated therefrom. In some examples, the disclosed furnace can be operated with an integrated holding section to feed directly into a casting process for large-scale structure parts.

[0017] In some examples, the disclosed immersion-based melting furnace can, in the case of aluminum melting, produce between about three and ten tons per hour (t / h) of liquid aluminum alloy per hour. In addition, the disclosed furnace can melt about 5500 kg / h of aluminum cast alloys and can be configured to hold between about fifteen and twenty tons of liquid metal.

[0018] FIG. 1 is an immersion-based melting furnace 100 according to some embodiments of the present disclosure. In some embodiments, the furnace 100 can include a feeding unit 101 configured to load solid metal into the furnace 100. In some embodiments, the solid metal can be aluminum, although this is not limiting and is merely exemplary in nature. In some embodiments, the solid metal can be loaded in the form of ingots, blocks, and / or internal run-around scrap. In addition, the furnace 100 can include a buffer 102 to allow the furnaceAttorney Docket No. 6474.028WO1 to be fed automatically but with an appropriate buffer of time. In some embodiments, the buffer can be solid metal and can cause there to be a buffer of about one hour. However, one hour of buffering time is not required and the length of the conveyor can vary based on the desired buffer time. In some embodiments, the feeding unit 101 can have a width of approximately 2.5 times the width of loading blocks. In some embodiments, the feeding unit 101 can include a walking floor, a vibro feeder, or a pusher. In some embodiments, the feeding unit 101 can include a heavy-duty walking floor charger with a capacity of twenty tons of more of metal charges. In some embodiments, if the furnace operates at a melting rate of around 5500 kg / h, the feeding unit 101 can load ingot bundles with a width of about 700mm and a 2m wide conveyor.

[0019] In addition, the furnace 100 can include a melting chamber 103 surrounded by refractory walls 109. In some embodiments, a refractory wall can refer to a material that is generally resistant to decomposition by heat, pressure, and other extreme conditions. Moreover, the walls can retain their form and strength even when exposed to such extreme conditions, such as those present at the inside of a furnace. The melting chamber 103 can receive the solid metal from the feeding unit 101. In addition, the melting chamber 103 can receive liquid metal in order to form a bath and melt the solid metal. Additional details of the melting chamber 103 are discussed in relation to FIG. 2.

[0020] Further, the furnace 100 can include a heating chamber 110 that can receive a mixture from the melting chamber 103, which can be surrounded by a refractory wall 109. The mixture can be created from the melting of the solid metal ingots in the melting chamber 103 within the liquid metal. In some embodiments, the mixture can be fully liquid, although this is not necessarily required and may not always occur. In other words, the entirety of the solid metal may not necessarily become liquid in the melting chamber 103. In some embodiments, the heating chamber 110 can include porous plugs 104a-c (referred to individually as a ^porous plug 104^ or collectively as ^porous plugs 104^), which can cause floatation of dross from the mixture received by the melting chamber 103, as well as degassing. For example, a porous plug 104 can include ceramic, such as alumina ceramic, with known or controlled porosity that enable and enhance gas flow. Additionally, other types of gas diffusers mayAttorney Docket No. 6474.028WO1 be used, as well. In some embodiments, the porous plugs 104 can force, via floatation, suspended dross and / or oxide films into a dross layer. Then, one or more skim damns (see FIG. 3) can trap the floating or sinking dross, which can ensure easy cleaning of the furnace 100. In some embodiments, the area containing the porous plugs 104 and the skim damns can be referred to as a ^cleaning section.^ In some embodiments, each skim damn can have a length that is about twice the radius of the floatation bubbles reaching the surface of the liquid metal within the furnace.

[0021] In addition, the heating chamber 110 can include a plurality of immersion heaters 105. Each of the immersion heaters 105 can be immersed in the liquid metal (or liquid metal mixture prior to complete melting) contained within the heating chamber 110. In some embodiments, there can be 26 immersion heaters 105 which are organized into groups of four to six elements. In some embodiments, each grouping of immersion heaters 105 can be connected to a removable lid, which can be raised to enable cleaning. In some embodiments, the heating chamber 110 can include a transfer pump 106 configured to circulate the liquid metal around the heating chamber 110. In some embodiments, the transfer pump 106 can be a mechanical pump or an inductive pump. In some embodiments, the heating chamber 110 can also include a pump 108 that is configured to pump liquid metal into the melting chamber 103 for melting purposes.

[0022] In some embodiments, the furnace 100 can include a holding section 112. In some embodiments, the holding section 112 can be configured to feed directly into a casting process for large-scale structure parts. In some embodiments, the holding section 112 can include a level pump and degasser 107a-b, as well as a transfer pump 111 that can pump liquid metal for a casting process, such as into a subsequent furnace. In some embodiments, the holding section 112 can have a capacity of about 15 tons of metal content and can be configured to receive 2750 kg every thirty minutes. In addition, the holding section 112 can be configured to keep the temperature of the received metal constant within about twelve degrees for an hour.

[0023] FIG. 2 is a melting chamber 103 from the immersion-based melting furnace of FIG. 1 according to some embodiments of the present disclosure. TheAttorney Docket No. 6474.028WO1 view of FIG. 2 can be taken from the A-A cross-section of FIG. 1. The melting chamber 103 can receive aluminum blocks at various stages 201a-d from the feeding unit 101 via the buffer 102. In some embodiments, the melting chamber 103 can include a swinging door 202, which can be open during melting mode and closed in standby to keep heat within the melting chamber 103. In some embodiments, the aluminum block 201 can slide down a ramp into a bath 208 of liquid metal. The liquid metal in the bath 208 can have been circulated into the melting chamber 103 via the pump 108 of FIG. 1 contained in the heating chamber 110. In some embodiments, the liquid metal in the bath 208 can be maintained at a level 203 in standby mode and at a second level 204 in melting mode. Further, the melting chamber 103 can include a door 205 that enables access to the bath 208 for cleaning purposes. In some embodiments, the melting chamber 103 can include one or more radiant roof heaters (e.g., resistant heaters) 206 that are configured to heat the melting chamber 103 maintain a pre-defined WHPSHUDWXUH^OHYHO^^VXFK^DV^^^^^&^^In some embodiments, each of the radiant heaters 206 can have a power output of between about 15 and 90 kilowatts. In some embodiments, adding heat to the system via the radiant heaters 206 can help reduce the risk of moisture in the metal while aluminum block 201 slides down the ramp. In some embodiments, the melting chamber 103 can also include a fan (not shown) for convective heating. Further, the melting chamber 103 can include one or more lasers 207 for monitoring various characteristics of the melting process. For example, a first laser can monitor the charge level of the aluminum block 201 as it enters the melting chamber 103 and a second laser can monitor the level of the liquid metal mixture within the bath 208.

[0024] FIG. 3 is a heating chamber 110 from the immersion-based melting furnace of FIG. 1 according to some embodiments of the present disclosure. The view of FIG. 3 can be taken from the B-B cross-section of FIG. 1. As discussed in FIG. 2, the melting chamber 103 can include levels 203 and 204 of the liquid metal. The heating chamber 110 can include porous plugs 104a-c and the plurality of immersion heaters 105, as discussed in relation to FIG. 1. In addition, the heating chamber 110 can include two skim damns 301a-b to trap the floating or sinking dross within the liquid metal. In some embodiments, the heating chamber 110 can include a sloped floor 302 to collect sediments andAttorney Docket No. 6474.028WO1 enable simple draining procedures. In some embodiments, the heating chamber 110 can maintain the liquid metal at a level between levels 303 and 304. In other words, the heating chamber 110 can utilize a minimum and maximum metal level.

[0025] FIG. 4 is an example method 400 for operating an immersion-based melting furnace according to some embodiments of the present disclosure. At block 401, a bath of liquid metal is maintained in the heating chamber 110 with a plurality of immersion heaters 105. At block 402, at least a portion of the liquid metal is pumped from the heating chamber 110 to the melting chamber 103, such as via a mechanical pump or inductive pump (pump 108). At block 403, a feeding unit 101 loads solid metal into a melting chamber 103. In some embodiments, the solid metal can be fed in in shape of ingots, blocks, or scrap metal. In some embodiments, the solid metal can be fed via a walking floor, a vibro feeder, or a pusher unit with controlled speed. In some embodiments, the solid metal can slide down a ramp (i.e., via gravity) into a bath of the liquid metal, which causes the solid metal to melt. In other words, the solid metal is submerged in the liquid metal, causing the solid metal to heat up until it begins to melt. This creates a metal mixture.

[0026] At block 404, the metal mixture is pumped from the melting chamber 103 to a cleaning section. Once in the cleaning section, at block 405, the mixture is cleaned. In some embodiments, cleaning the mixture can include degassing the metal mixture via one or more porous plugs 104 and collecting dross from the metal mixture via one or more skim damns. At block 406, the cleaned mixture is further pumped into the heating chamber 110, such as for additional heating to be applied via the immersion heaters 105. Exemplary Aspects.

[0027] The following exemplary embodiments are provided, the numbering of which is not to be construed as designating levels of importance:

[0028] Aspect 1 provides a melting furnace comprising: a feeding unit configured to feed solid metal;Attorney Docket No. 6474.028WO1 a heating chamber for heating and maintaining molten metal, the heating chamber comprising a plurality of immersion heaters, wherein each immersion heater is immersed in and heating the molten metal; a pump configured to circulate the molten metal from the heating chamber into a melting chamber; and the melting chamber configured to receive the solid metal from the feeding unit and the molten metal from the heating chamber, wherein the solid metal submerges in the molten metal within the melting chamber and melts to create a liquid metal; wherein the liquid metal circulates from the melting chamber to the heating chamber.

[0029] Aspect 2 provides the melting furnace of Aspect 1, wherein the feeding unit comprises at least one of a walking floor, a vibro feeder, or a pusher unit to load the solid metal with controlled speed.

[0030] Aspect 3 provides the melting furnace of any of Aspects 1 or 2, wherein the melting chamber comprises a recessed bath section for mixing the solid metal in the molten metal.

[0031] Aspect 4 provides the melting furnace of Aspect 3, wherein the melting chamber comprises one or more radiant roof heaters configured to maintain a refractory of the melting chamber above a pre-defined temperature value.

[0032] Aspect 5 provides the melting furnace of Aspect 4, wherein the one or more radiant roof heaters have a power of between 15 and 90 kilowatts and the pre-GHILQHG^WHPSHUDWXUH^YDOXH^LV^^^^^&^

[0033] Aspect 6 provides the melting furnace of any of Aspects 3-5, wherein the melting chamber comprises: a first laser for monitoring a charge level of the solid metal; and a second laser for monitoring a height of the liquid metal.

[0034] Aspect 7 provides the melting furnace of any of Aspects 3-6, wherein the melting chamber comprises a ramp, wherein the solid metal slides down the ramp and into the recessed bath.

[0035] Aspect 8 provides the melting furnace of any of Aspects 1-7 comprising a cleaning chamber for removing dross out of the liquid metal via porous plugs prior to the liquid metal entering the heating chamber.Attorney Docket No. 6474.028WO1

[0036] Aspect 9 provides the melting furnace of Aspect 8, wherein the cleaning chamber comprises one or more skim damns configured to collect dross from the liquid metal.

[0037] Aspect 10 provides the melting furnace of any of Aspects 1-9, wherein: each of the plurality of immersion heaters has a diameter of between 75 and 135 mm; and the plurality of immersion heaters has a heating power of between 1000 and 3000 kilowatts.

[0038] Aspect 11 provides a method of operating a melting furnace comprising: heating molten metal in a heating chamber via a plurality of immersion heaters contacting the molten metal; pumping a portion of the molten metal from the heating chamber to a melting chamber; feeding solid metal into the melting chamber; melting the solid metal by submerging, in the melting chamber, the solid metal in the portion of the molten metal to create a metal mixture; and circulating the metal mixture from the melting chamber to the heating chamber.

[0039] Aspect 12 provides the method of Aspect 11, wherein feeding the solid metal into the melting chamber comprises feeding the solid metal via at least one of a walking floor, a vibro feeder, or a pusher unit.

[0040] Aspect 13 provides the method of any of Aspects 11 or 12, wherein melting the solid metal comprises submerging the solid metal in the portion of the molten metal in a recessed bath section of the melting chamber.

[0041] Aspect 14 provides the method of Aspect 13 comprising heating the melting chamber via one or more radiant roof heaters to maintain a refractory of the melting chamber above a pre-defined temperature value.

[0042] Aspect 15 provides the method of Aspect 14, wherein the one or more radiant roof heaters have a power of between 15 and 90 kilowatts and the pre- GHILQHG^WHPSHUDWXUH^YDOXH^LV^^^^^&^

[0043] Aspect 16 provides the method of any of Aspects 13-15 comprising: monitoring a charge level of the solid metal via a first laser; and monitoring a height of the metal mixture via a second laser.Attorney Docket No. 6474.028WO1

[0044] Aspect 17 provides the method of any of Aspects 13-16 wherein feeding the solid metal into the melting chamber comprises causing the solid metal to slide down a ramp and into the recessed bath.

[0045] Aspect 18 provides the method of any of Aspects 11-17 comprising filtering the metal mixture prior to the metal mixture entering the heating chamber.

[0046] Aspect 19 provides the method of Aspect 18, wherein filtering the metal mixture comprises: degassing the metal mixture via one or more porous plugs; and collecting dross from the metal mixture via one or more skim damns.

[0047] Aspect 20 provides the method of any of Aspects 11-19, wherein: each of the plurality of immersion heaters has a diameter of between 75 and 135 mm; and the plurality of immersion heaters has a heating power of between 1000 and 3000 kilowatts.

[0048] While various embodiments have been described above, it should be understood that they have been presented by way of example and not limitation. It will be apparent to persons skilled in the relevant art(s) that various changes in form and detail may be made therein without departing from the spirit and scope. In fact, after reading the above description, it will be apparent to one skilled in the relevant art(s) how to implement alternative embodiments. For example, other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims.

[0049] In addition, it should be understood that any figures which highlight the functionality and advantages are presented for example purposes only. The disclosed methodology and system are each sufficiently flexible and configurable such that they may be utilized in ways other than that shown.

[0050] Although the term ^at least one^ may often be used in the specification, claims and drawings, the terms ^a^, ^an^, ^the^, ^said^, etc. also signify ^at least one^ or ^the at least one^ in the specification, claims and drawings.

Claims

Attorney Docket No. 6474.028WO1 CLAIMS 1. A melting furnace comprising: a feeding unit configured to feed solid metal; a heating chamber for heating and maintaining molten metal, the heating chamber comprising a plurality of immersion heaters, wherein each immersion heater is immersed in and heating the molten metal; a pump configured to circulate the molten metal from the heating chamber into a melting chamber; and the melting chamber configured to receive the solid metal from the feeding unit and the molten metal from the heating chamber, wherein the solid metal submerges in the molten metal within the melting chamber and melts to create a liquid metal; wherein the liquid metal circulates from the melting chamber to the heating chamber.

2. The melting furnace of claim 1, wherein the feeding unit comprises at least one of a walking floor, a vibro feeder, or a pusher unit to load the solid metal with controlled speed.

3. The melting furnace of claim 1, wherein the melting chamber comprises a recessed bath section for mixing the solid metal in the molten metal.

4. The melting furnace of claim 3, wherein the melting chamber comprises one or more radiant roof heaters configured to maintain a refractory of the melting chamber above a pre-defined temperature value.

5. The melting furnace of claim 4, wherein the one or more radiant roof heaters have a power of between 15 and 90 kilowatts and the pre-defined WHPSHUDWXUH^YDOXH^LV^^^^^&.Attorney Docket No. 6474.028WO1 6. The melting furnace of claim 3, wherein the melting chamber comprises: a first laser for monitoring a charge level of the solid metal; and a second laser for monitoring a height of the liquid metal.

7. The melting furnace of claim 3, wherein the melting chamber comprises a ramp, wherein the solid metal slides down the ramp and into the recessed bath.

8. The melting furnace of claim 1 comprising a cleaning chamber for removing dross out of the liquid metal via porous plugs prior to the liquid metal entering the heating chamber.

9. The melting furnace of claim 8, wherein the cleaning chamber comprises one or more skim damns configured to collect dross from the liquid metal.

10. The melting furnace of claim 1, wherein: each of the plurality of immersion heaters has a diameter of between 75 and 135 mm; and the plurality of immersion heaters has a heating power of between 1000 and 3000 kilowatts.

11. A method of operating a melting furnace comprising: heating molten metal in a heating chamber via a plurality of immersion heaters contacting the molten metal; pumping a portion of the molten metal from the heating chamber to a melting chamber; feeding solid metal into the melting chamber; melting the solid metal by submerging, in the melting chamber, the solid metal in the portion of the molten metal to create a metal mixture; and circulating the metal mixture from the melting chamber to the heating chamber.Attorney Docket No. 6474.028WO1 12. The method of claim 11, wherein feeding the solid metal into the melting chamber comprises feeding the solid metal via at least one of a walking floor, a vibro feeder, or a pusher unit.

13. The method of claim 11, wherein melting the solid metal comprises submerging the solid metal in the portion of the molten metal in a recessed bath section of the melting chamber.

14. The method of claim 13 comprising heating the melting chamber via one or more radiant roof heaters to maintain a refractory of the melting chamber above a pre-defined temperature value.

15. The method of claim 14, wherein the one or more radiant roof heaters have a power of between 15 and 90 kilowatts and the pre-defined temperature YDOXH^LV^^^^^&^ 16. The method of claim 13 comprising: monitoring a charge level of the solid metal via a first laser; and monitoring a height of the metal mixture via a second laser.

17. The method of claim 13 wherein feeding the solid metal into the melting chamber comprises causing the solid metal to slide down a ramp and into the recessed bath.

18. The method of claim 11 comprising filtering the metal mixture prior to the metal mixture entering the heating chamber.

19. The method of claim 18, wherein filtering the metal mixture comprises: degassing the metal mixture via one or more porous plugs; and collecting dross from the metal mixture via one or more skim damns.Attorney Docket No. 6474.028WO1 20. The method of claim 11, wherein: each of the plurality of immersion heaters has a diameter of between 75 and 135 mm; and the plurality of immersion heaters has a heating power of between 1000 and 3000 kilowatts.

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