AU2012206949A1

AU2012206949A1 - Production of ferro-alloys

Info

Publication number: AU2012206949A1
Application number: AU2012206949A
Authority: AU
Inventors: Paul James O'kane; Veena Sahajwalla; Paul Anthony Vielhauer
Original assignee: OneSteel NSW Pty Ltd
Current assignee: OneSteel NSW Pty Ltd
Priority date: 2011-01-13
Filing date: 2012-01-13
Publication date: 2013-05-02
Also published as: WO2012094707A1; AU2016202882A1; EA201390946A1; AU2018250373A1

Abstract

A method for producing a ferro-alloy, such as steel, in a metallurgical furnace and a reductant feed material for use in the method are disclosed. The method includes using a hydrocarbon polymer as a part of a reductant feed material and selecting a ratio of the hydrocarbon polymer addition and the other reductant addition to optimise operational indicators of the method. The reductant feed material includes a (i) a hydrocarbon polymer and (ii) another reductant.

Description

WO 2012/094707 PCT/AU2012/000021 PRODUCTION OF FERRO-ALLOYS The present invention relates to a method of producing ferro-alloys (such as steel) in an electric arc 5 furnace or other suitable metallurgical furnace. International Publication WO 2006/024069 in the name of New South Innovations Pty Ltd, hereinafter referred to as the "first International Publication" discloses a 10 method for producing a ferro-alloy in an electric arc furnace that is characterised by supplying an unagglomerated carbon-containing polymer that functions as a slag foaming agent to the furnace. 15 The first International Publication defines the term "unagglomerated carbon-containing polymer" as covering "both fine and coarse granulated and particulate polymers and is intended to exclude such polymers as formed together with EAF waste dust or steel dust". The 20 International Publication describes that such agglomerated solids comprising polymers and EAF waste dust or steel dust do not function as a slag foaming agent. The first International Publication describes that, 25 typically, the unagglomerated carbon-containing polymer is charged into an electric arc furnace such that it at least partially combusts and produces a carbonaceous residue. The International Publication also describes that the carbonaceous residue then oxidises to cause slag foaming 30 and may additionally function as a reducing agent, as a fuel and/or a recarburiser. The first International Publication describes that, typically, the carbon-containing polymer comprises the 35 atoms C, H and optionally 0 only and that, whilst other elements may be present in the polymer (e.g. N, S, P, Si, halogens etc.) these other elements may interfere with WO 2012/094707 PCT/AU2012/000021 2 ferro-alloy production and/or produce contaminants, pollutants, noxious gases etc. The International Publication describes that, by judiciously selecting the carbon-containing polymer, the formation of noxious gases 5 and other detrimental or harmful products can be avoided. The International Publication describes that one suitable carbon-containing polymer is polyethylene but other plastics such as polypropelyene, polystyrene, polybutadiene styrene, APS etc. may also be used. 10 The applicant has carried out trials on the method of producing ferro-alloys described in the first International Publication. The trials were carried out on ferro-alloys in the form of steel at electric arc furnace 15 facilities in Melbourne and Sydney. International publication WO 2010/022473 in the name of New South Innovations Pty Ltd, hereinafter referred to as the "second International Publication" discloses an 20 invention of a method for producing a ferro-alloy in an electric arc furnace arising from a consideration of the results of the trials. Claim 1 of the second International Publication 25 defines a method for producing a ferro-alloy, such as steel, in an electric arc furnace or other suitable metallurgical furnace that comprises supplying a mixture of (a) a carbon-containing polymer that is capable of acting as a slag foaming agent and (b) another source of 30 carbon into the furnace during at least a part of a power on phase of the method. Claim 2 of the second International Publication defines a method for producing a ferro-alloy, such as 35 steel, in an electric arc furnace or other suitable metallurgical furnace that comprises supplying a mixture of (a) a carbon-containing polymer that is capable of WO 2012/094707 PCT/AU2012/000021 3 acting as a slag foaming agent and (b) another source of carbon into the furnace during at least a part of a first power-on phase of the method and supplying a further mixture of the carbon-containing polymer and another 5 source of carbon into the electric arc furnace during a second power-on phase of the method. Claim 3 of the second International Publication defines a method of producing a ferro-alloy in an electric 10 arc furnace or other suitable metallurgical furnace which comprises: (a) supplying an initial charge of a feedstock for the ferro-alloy to the furnace; 15 (b) operating in a first power-on phase and establishing an arc between an electrode or electrodes of the furnace and the solid feedstock charge and generating heat in the furnace and melting the solid feedstock 20 charge; (c) after a first period of time into the first power-on phase, commencing supply of a mixture of (i) a carbon-containing polymer that is capable of acting as a 25 slag foaming agent and (ii) another source of carbon into the furnace; (d) at the end of the first power-on phase, supplying a further charge of the ferro-alloy feedstock to the 30 furnace; (e) operating in a second power-on phase by re establishing the arc; 35 (f) after a first period of time into the second power-on phase, commencing injection of a mixture of (i) a carbon-containing polymer that is capable of acting as a WO 2012/094707 PCT/AU2012/000021 4 slag foaming agent and (ii) another source of carbon into the furnace; and (g) at the end of the second power-on phase, tapping 5 molten ferro-alloy from the furnace. The above description of the disclosure in the first and the second International Publications is not to be taken as an admission that the disclosure in the 10 International Publications is part of the common general knowledge in Australia or elsewhere. The disclosure in the first and the second International publications is incorporated herein by 15 cross-reference. The applicant has carried out further research and development work in relation to the methods of producing ferro-alloys described in the first and the second 20 International publications. The applicant has found as a result of the further research and development work that a steelmaking method in an electric arc furnace that includes the use of 25 hydrocarbon polymers, i.e. polymers comprising carbon and hydrogen, as a part of the reductant feed material for the method can provide a significant improvement in a number of key operational indicators compared to electric arc furnace steelmaking methods that use conventional 30 reductant sources, such as coke, as feed materials for the methods and do not use hydrocarbon polymers as a reductant source. Relevant operational indicators include any one or 35 more of electricity consumption for a heat, the amount of FeO in slag at the end of a heat, the total amount of reductant required for a heat, the melting rate during a WO 2012/094707 PCT/AU2012/000021 5 heat, and the emissions (such as C02) released during the course of a heat. In particular, the applicant has found that the 5 hydrogen component of the hydrocarbon polymers has a significant impact on reduction of FeO to iron in slag, the level of foamy slag, and the total reductant requirements for a heat in a steelmaking method. 10 In particular, the applicant has found that supplying hydrogen polymers and other reductant (i.e. conventional carbon sources such as coke) into an electric arc furnace has a synergistic effect on the production of steel in an electric arc furnace that is not achieved by the injection 15 of hydrocarbon polymers as the sole reductant and conventional carbon sources such as coke as the sole reductant. In general terms, the present invention provides a 20 method for producing a ferro-alloy, such as steel, in an electric arc furnace or other suitable metallurgical furnace that includes supplying a hydrocarbon polymer as a part of a reductant feed material for the method in the furnace. 25 In more particular terms, according to the present invention there is provided a method for producing a ferro-alloy, such as steel, in an electric arc furnace or other suitable metallurgical furnace that includes 30 supplying a hydrocarbon polymer as a part of a reductant feed material for the method in the furnace and selecting a ratio of the hydrocarbon polymer addition and the other reductant addition to optimise operational indicators of the method, as described herein. 35 The term "hydrocarbon polymer" is understood herein to mean a polymer comprising carbon and hydrogen. The WO 2012/094707 PCT/AU2012/000021 6 polymer may include oxygen and other elements. It is noted that whilst other elements (such as nitrogen, sulphur and phosphorus) may be present in the polymer, in any situation it is important to consider whether and to 5 what extent these other elements may interfere with ferro alloy production and/or produce contaminants and pollutants, including noxious gases. The operational indicators may include any one or 10 more of electricity consumption for a heat in the furnace, the amount of FeO in slag at the end of the heat, the amount of reductant required for the heat, the melting rate (i.e. the tonnes of steel produced divided by the power-on time in minutes) during the heat, and the 15 emissions (such as CO 2 ) released during the course of the heat. The method may include supplying, such as by injecting, the hydrocarbon polymer and the other reductant 20 during any suitable phase of the method. The method may include supplying the hydrocarbon polymer and the other reductant during a power-on phase of the method. 25 The method may include supplying the hydrocarbon polymer and the other reductant during a power-off phase of the method. 30 The method may include supplying the hydrocarbon polymer and the other reductant at the same time or at a different time during the method. The hydrocarbon polymer may be an unagglomerated 35 polymer described herein.

WO 2012/094707 PCT/AU2012/000021 7 The unagglomerated hydrocarbon polymer may include any one or more of synthetic rubber, natural rubber, high density polypropylene, and low density polypropylene. 5 The hydrocarbon polymer may be an agglomerated hydrocarbon polymer. Examples of such agglomerates include agglomerates of hydrocarbon polymers and any one or more of fluxes, iron oxides (such as mill scale), and bag house solids. 10 The other reductant may be any suitable source of carbon and may include any one or more of coke, carbon char, charcoal and graphite. 15 The ratio of the hydrocarbon polymer and the other reductant supplied into the furnace may be varied during the period of addition of these materials in the method. The ratio of the hydrocarbon polymer and the other 20 reductant supplied into the furnace may be constant during the period of addition of these materials in the method. The flowrate of the mixture of the hydrocarbon polymer and the other reductant supplied into the furnace 25 may be constant or may be varied during the method. There may be continuous or periodic supply of the hydrocarbon polymer and the other reductant into the furnace during the method. 30 The hydrocarbon polymer may comprise 20-60 wt.% of the total weight of the hydrocarbon polymer and the other reductant supplied into the furnace. 35 Typically, the hydrocarbon polymer comprises 20 50 wt.% of the total weight of the hydrocarbon polymer and the other reductant supplied into the furnace.

WO 2012/094707 PCT/AU2012/000021 8 Typically, the hydrocarbon polymer comprises 35 45 wt.% of the total weight of the hydrocarbon polymer and the other reductant supplied into the furnace. 5 The sizes and the densities of each of the hydrocarbon polymer and the other reductant supplied into the furnace may be selected having regard to the materials handling requirements for mixing and transporting the 10 mixture to the furnace. The hydrocarbon polymer and the other reductant may be supplied as separate components and therefore stored and supplied to the furnace as separate components. 15 The method may include mixing the hydrocarbon polymer and the other reductant and forming a mixture and supplying the mixture to the furnace. 20 The hydrocarbon polymer and the other reductant may be mixed remotely from the furnace and stored as a mixture, for example proximate the furnace, and supplied via a pipeline or other suitable delivery system to the furnace. 25 Alternatively, the hydrocarbon polymer and the other reductant may be stored separately, for example proximate the furnace, and mixed as required and transported to the furnace. 30 The materials handling considerations may include forming the mixture as a homogeneous mixture, i.e. a mixture that has a substantially uniform density with minimum segregation of the components 35 The materials handling considerations may include being able to transport the mixture to the furnace WO 2012/094707 PCT/AU2012/000021 9 efficiently, i.e. by avoiding blockages in pipes or other delivery systems. The hydrocarbon polymer may be in the form of 5 particles. The size of the hydrocarbon polymer particles may be less than 6 mm. 10 The size of the hydrocarbon polymer particles may be less than 4 mm. The size of the hydrocarbon polymer particles may be greater than 1 mm. 15 The size of the hydrocarbon polymer particles may be 1-6 mm. The size of the hydrocarbon polymer particles may be 20 1-4 mm. The method may include supplying an oxygen-containing gas, such as oxygen, into the furnace during the power-on phase or phases. 25 The method may include monitoring the slag profile, as described herein, during the course of the method and controlling supply of the hydrocarbon polymer and the other reductant having regard to the monitored slag 30 profile. The term "slag profile" is understood herein to mean characteristics, such as iron oxide levels, of the slag that provide an indication (directly or indirectly) of the 35 operation of the method.

WO 2012/094707 PCT/AU2012/000021 10 The slag profile may be monitored continuously or periodically. According to the present invention there is also 5 provided a method of producing a ferro-alloy, such as steel, in an electric arc furnace or other suitable metallurgical furnace which includes: (a) supplying an initial solid charge of a feedstock 10 for the ferro-alloy to the furnace; (b) operating in a first power-on phase and establishing an arc between an electrode or electrodes of the furnace and the solid feedstock charge and generating 15 heat in the furnace and melting the solid feedstock charge; (c) after a first period of time into the first power-on phase, commencing supply of (i) a hydrocarbon 20 polymer and (ii) another reductant into the furnace as a reductant feed material for the method; (d) at the end of the first power-on phase, supplying a further charge of the ferro-alloy feedstock to the 25 furnace; (e) operating in a second power-on phase by re establishing the arc; 30 (f) after a first period of time into the second power-on phase, commencing supply of (i) a hydrocarbon polymer and (ii) another reductant into the furnace as a reductant feed material for the method; and 35 (g) at the end of the second power-on phase, tapping molten ferro-alloy from the furnace.

WO 2012/094707 PCT/AU2012/000021 11 According to the present invention there is also provided an electric arc furnace or other suitable metallurgical furnace which includes a materials handling system for supplying (i) a hydrocarbon polymer and (ii) 5 another reductant into the furnace as a reductant feed material for a method of producing a ferro-alloy, such as steel, in the furnace. The materials handling system may be adapted to 10 supply a mixture of the hydrocarbon polymer and the other reductant. According to the present invention there is also provided a reductant feed material for use in a method of 15 producing a ferro-alloy, such as steel, in an electric arc furnace or other suitable metallurgical furnace which includes a mixture of (i) a hydrocarbon polymer and (ii) another reductant. 20 The hydrocarbon polymer may include an unagglomerated hydrocarbon polymer including any one or more of synthetic rubber, natural rubber, high density polypropylene, and low density polypropylene. 25 The hydrocarbon polymer may include an agglomerated hydrocarbon polymer including any one or more of agglomerates of hydrocarbon polymers and any one or more of fluxes, iron oxides (such as mill scale), and bag house solids. 30 The other reductant may include any one or more of coke, carbon char, charcoal and graphite. The hydrocarbon polymer may comprise 20-60 wt.% of 35 the total weight of the hydrocarbon polymer and the other reductant supplied into the furnace.

WO 2012/094707 PCT/AU2012/000021 12 The hydrocarbon polymer may comprise 35-45 wt.% of the total weight of the hydrocarbon polymer and the other reductant supplied into the furnace. 5 The present invention is described further by way of example with reference to the accompanying drawing which is a timeline for one embodiment of a method of producing steel in an electric arc furnace in accordance with the present invention. 10 The following description of the timeline shown in the Figure was developed during the course of trials at electric arc facilities in Australia. 15 In general terms, the technology developed by the applicant as a consequence of the trials, including the flowsheet, focuses on areas such as, but not limited to, mixing of unagglomerated hydrocarbon polymers and other materials, supplying the mixture to a furnace, materials 20 handling of the mixture upstream of the furnace, and temperature pick-up and overall heat control in the furnace. It can readily be appreciated that appropriate 25 timelines for producing steel in other electric arc furnaces could readily be developed on a case-by-case basis. With reference to the figure, a first solid feedstock 30 for producing steel in the form of a scrap charge is supplied to the electric arc furnace in a two minute period of time. After charging the furnace, power is supplied to the 35 furnace electrodes and oxygen (or other suitable oxygen containing gas) is injected into the furnace. Arcs are established between the electrodes and the solid WO 2012/094707 PCT/AU2012/000021 13 feedstock, thereby generating heat that progressively melts the solid charge. After approximately 3MWh of power had been supplied 5 to the furnace, which is typically a period of time of three minutes into this first power-on phase, injection of fluxes in the form of lime and magnesia into the furnace commences. These materials are supplied to form a slag on molten material forming in the furnace. The figure of 10 3MWh equates to the power required for the electrodes to "bore down" through the scrap and to be arcing on the heavy melt in the bottom of the furnace. After approximately 8MWh of power has been supplied 15 to the furnace, which is typically a period of eight minutes into the first power-on phase, a mixture of an unagglomerated hydrocarbon polymer in the form of rubber and another source of reductant in the form of coke are injected into the furnace. The figure of 8MWh equates to 20 when a flat bath of molten material and a liquid slag begin to form. The injection of the mixture continues at a constant flow rate for a period of four minutes to the end of the first power-on (and oxygen injection) phase. The mixture is injected via a lance extending into the 25 furnace. Typically, the rubber is in the form of 1-4 mm particles. Typically, the rubber/coke mixture is a homogeneous mixture. Typically, the amounts of rubber and coke in the rubber/coke mixture are selected so that the rubber comprises 35-45 wt.% of the rubber/coke mixture. 30 The rubber/coke mixture acts as a reductant of FeO in the slag. The applicant found in the course of the trials that the rubber/coke mixture provided a synergistic effect. 35 WO 2012/094707 PCT/AU2012/000021 14 The rubber/coke mixture and the reduction products also act as a slag foaming agent, as described in the International Publication. 5 A second charge of the feedstock for producing steel in the form of a scrap charge is supplied to the furnace during a two minute period following the end of the first power-on phase. 10 After charging the second feedstock charge, power to the furnace and oxygen (or other suitable oxygen containing gas) injection are re-established and the furnace commences operating a second power-on phase. 15 After approximately 3MWh of power has been supplied to the furnace following the second feedstock charge, which is typically three minutes of the second power-on phase, fluxes in the form of lime and magnesia are supplied to the furnace to contribute to maintaining a 20 required level of slag in the furnace. After approximately 20 MWh of power has been supplied to the furnace since the first feedstock charge, which is typically a further five minute period of time in the 25 second power-on phase, the mixture of rubber and coke is again injected into the furnace via the lance and injection of the mixture continues at a constant flow rate until the end of the second power-on (and oxygen injection) phase. Typically, the second power-on (and 30 oxygen injection) phase runs for 24-28 minutes. Typically, the rubber is in the form of 1-4 mm particles. Typically, the rubber/coke mixture is a homogeneous mixture. Typically, the amounts of rubber and coke in the rubber/coke mixture are selected so that the rubber 35 comprises 35-45 wt.% of the rubber/coke mixture.

WO 2012/094707 PCT/AU2012/000021 15 After the second power-on phase ends, the furnace is tapped to discharge molten steel and slag from the furnace during a two minute period. 5 At the end of tapping, there is a two minute turnaround time before the method is repeated with a new charge of scrap is supplied to the furnace. Based on trials at Sydney and Melbourne electric arc 10 furnace facilities of the applicant, results achieved to date indicate that the use of hydrocarbon polymers as a part of the reductant feed for a method of producing steel in accordance with the invention: 15 (a) speeds up the slag-foaming process; (b) reduces the level of FeO in slag for a given amount of reductant addition compared to a conventional method based on the injection of reductant other than 20 hydrocarbon polymer; (c) reduces the amount of reductant addition required to produce the same amount of steel compared to a conventional method based on the injection of reductant 25 other than hydrocarbon polymer; (d) reduces electricity consumption, meaning a fall in greenhouse gas emissions if produced by coal-fired power stations; 30 (e) reduces total cost of production by reducing the quantity of injectant material required; (f) improves furnace productivity by increasing the 35 melting rate - a measure of the tonnes of steel produced for every minute of electric arc furnace power-on time; and WO 2012/094707 PCT/AU2012/000021 16 (g) reduces greenhouse gas emissions, such as CO 2 produced in the method. 5 In addition, the use of hydrocarbon polymers has significant potential environmental advantages by using materials that may otherwise be regarded as waste products only suitable for use as land fills. 10 The above findings are significant outcomes. Many modifications may be made to the embodiment of the method of the present invention described above without departing from the spirit and scope of the 15 invention. By way of example, whilst the embodiment is described in the context of producing steel, the present invention is not so limited and extends to the production of ferro 20 alloys generally. Furthermore, whilst the embodiment is described in the context of producing steel in an electric arc furnace, the present invention is not so limited and extends to the 25 production of steel and ferro-alloys generally in any suitable metallurgical vessel. In addition, whilst the embodiment includes the use of an unagglomerated hydrocarbon polymer, the present 30 invention is not so limited and extends to the use of agglomerated hydrocarbon polymers. In addition, whilst the embodiment includes the supply of the mixture of the unagglomerated hydrocarbon 35 polymer and the other reductant by injecting the mixture through one of more than one lance extending into the furnace, the present invention is not so limited and WO 2012/094707 PCT/AU2012/000021 17 extends to supplying the mixture in to the furnace using any suitable apparatus. In addition, whilst the embodiment includes 5 particular time periods for charging the furnace, and supplying other materials to the furnace, the present invention is not limited to these time periods and extends to any suitable time periods. In addition, the present invention extends to situations in which there is 10 continuous charging of materials to the furnace. In addition, whilst the embodiment includes continuous injection of the mixture of the unagglomerated hydrocarbon polymer and the other reductant at constant 15 flow rates during part of power-on phases, the present invention is not so limited and extends to periodic injection and/or variable flow rates of injection during power-on phases and, if required, other non-power-on phases of the method. 20 In addition, whilst the embodiment includes the use of lime and magnesia as slag-forming agents, the present invention is not so limited and extends to the use of any suitable materials. 25 In addition, whilst the embodiment includes supplying lime and magnesia during the first and second power-on phases, the present invention is not so limited and extends to adding these and other fluxes with the scrap, 30 during power-on and after power on. In addition, whilst the embodiment includes operating the method with two power-on phases, the present invention is not so limited and extends to operating with one or any 35 other suitable number of power-on phases.

WO 2012/094707 PCT/AU2012/000021 18 In addition, whilst the embodiment describes the supply of the mixture of the unagglomerated hydrocarbon polymer and the other reductant, the present invention also extends to embodiments in which there is supply of 5 only one of the components rather than a mixture of the components at other times in the method.

Claims

1. A method for producing a ferro-alloy, such as steel, in an electric arc furnace or other suitable metallurgical 5 furnace that includes supplying a hydrocarbon polymer as a part of a reductant feed material for the method in the furnace and selecting a ratio of the hydrocarbon polymer addition and the other reductant addition to optimise operational indicators of the method, the operational 10 indicators including any one or more of electricity consumption for a heat in the furnace, the amount of FeO in slag at the end of the heat, the amount of reductant required for the heat, the melting rate during the heat, and the emissions released during the course of the heat. 15

2. The method defined in claim 1 includes supplying, such as by injecting, the hydrocarbon polymer and the other reductant during a power-on phase of the method. 20 3. The method defined in claim 1 or claim 2 includes supplying the hydrocarbon polymer and the other reductant during a power-off phase of the method.

4. The method defined in any one of the preceding claims 25 includes supplying the hydrocarbon polymer and the other reductant at the same time or at a different time during the method.

5. The method defined in any one of the preceding claims 30 wherein the hydrocarbon polymer includes an unagglomerated hydrocarbon polymer including any one or more of synthetic rubber, natural rubber, high density polypropylene, and low density polypropylene. 35 6. The method defined in any one of claims 1 to 4 wherein the hydrocarbon polymer includes an agglomerated hydrocarbon polymer including any one or more of WO 2012/094707 PCT/AU2012/000021 20 agglomerates of hydrocarbon polymers and any one or more of fluxes, iron oxides (such as mill scale), and bag house solids. 5 7. The method defined in any one of the preceding claims wherein the other reductant includes any one or more of coke, carbon char, charcoal and graphite.

8. The method defined in any one of the preceding claims 10 includes varying the ratio of the hydrocarbon polymer and the other reductant during the period of addition of these materials.

9. The method defined in any one of the claims 1-7 15 includes keeping the ratio of the hydrocarbon polymer and the other reductant supplied into the furnace constant during the period of addition of these materials.

10. The method defined in any one of the preceding claims 20 includes varying the flowrate of the mixture of the hydrocarbon polymer and the other reductant supplied into the furnace.

11. The method defined in any one of claims 1-9 includes 25 keeping the flowrate of the mixture of the hydrocarbon polymer and the other reductant supplied into the furnace constant.

12. The method defined in any one of the preceding claims 30 wherein the hydrocarbon polymer comprises 20-60 wt.% of the total weight of the hydrocarbon polymer and the other reductant supplied into the furnace.

13. The method defined in any one of the preceding claims 35 wherein the hydrocarbon polymer comprises 20-50 wt.% of the total weight of the hydrocarbon polymer and the other reductant supplied into the furnace. WO 2012/094707 PCT/AU2012/000021 21

14. The method defined in any one of the preceding claims wherein the hydrocarbon polymer comprises 35-45 wt.% of the total weight of the hydrocarbon polymer and the other 5 reductant supplied into the furnace.

15. The method defined in any one of the preceding claims includes storing the hydrocarbon polymer and the other reductant as separate components and supplying the 10 hydrocarbon polymer and the other reductant to the furnace as separate components.

16. The method defined in any one of claims 1-14 includes mixing the hydrocarbon polymer and the other reductant and 15 forming a mixture and supplying the mixture to the furnace.

17. The method defined in any one of the preceding claims wherein the hydrocarbon polymer is in the form of 20 particles that are less than 6 mm.

18. The method defined in any one of the preceding claims wherein the hydrocarbon polymer is in the form of particles that are less than 4 mm. 25

19. The method defined in any one of the preceding claims wherein the hydrocarbon polymer is in the form of particles that are greater than 1 mm. 30 20. The method defined in any one of the preceding claims wherein the hydrocarbon polymer is in the form of particles having a particle size range of 1-4 mm.

21. The method defined in any one of the preceding claims 35 includes monitoring the slag profile during the course of the method and controlling supply of the hydrocarbon WO 2012/094707 PCT/AU2012/000021 22 polymer and the other reductant having regard to the monitored slag profile.

22. A method for producing a ferro-alloy, such as steel, 5 in an electric arc furnace or other suitable metallurgical furnace that includes supplying a hydrocarbon polymer as a part of a reductant feed material for the method in the furnace. 10 23. A method of producing a ferro-alloy, such as steel, in an electric arc furnace or other suitable metallurgical furnace which includes: (a) supplying an initial solid charge of a feedstock 15 for the ferro-alloy to the furnace; (b) operating in a first power-on phase and establishing an arc between an electrode or electrodes of the furnace and the solid feedstock charge and generating 20 heat in the furnace and melting the solid feedstock charge; (c) after a first period of time into the first power-on phase, commencing supply of (i) a hydrocarbon 25 polymer and (ii) another reductant into the furnace as a reductant feed material for the method; (d) at the end of the first power-on phase, supplying a further charge of the ferro-alloy feedstock to the 30 furnace; (e) operating in a second power-on phase by re establishing the arc; 35 (f) after a first period of time into the second power-on phase, commencing of (i) a hydrocarbon polymer WO 2012/094707 PCT/AU2012/000021 23 and (ii) another reductant into the furnace as a reductant feed material for the method; and (g) at the end of the second power-on phase, tapping 5 molten ferro-alloy from the furnace.

24. An electric arc furnace or other suitable metallurgical furnace which includes a materials handling system for supplying a (i) a hydrocarbon polymer and (ii) 10 another reductant into the furnace as a reductant feed material for a method of producing a ferro-alloy, such as steel, in the furnace.

25. The furnace defined in claim 24 wherein the materials 15 handling system is adapted to supply a mixture of the hydrocarbon polymer and the other reductant.

26. A reductant feed material for use in a method of producing a ferro-alloy, such as steel, in an electric arc 20 furnace or other suitable metallurgical furnace which includes a mixture of (i) a hydrocarbon polymer and (ii) another reductant.

27. The reductant feed material defined in claim 26 25 wherein the hydrocarbon polymer includes an unagglomerated hydrocarbon polymer including any one or more of synthetic rubber, natural rubber, high density polypropylene, and low density polypropylene. 30 28. The reductant feed material defined in claim 26 wherein the wherein the hydrocarbon polymer includes an agglomerated hydrocarbon polymer including any one or more of agglomerates of hydrocarbon polymers and any one or more of fluxes, iron oxides (such as mill scale), and bag 35 house solids. WO 2012/094707 PCT/AU2012/000021 24

29. The reductant feed material defined in any one of claims 26 to 28 wherein the other reductant includes any one or more of coke, carbon char, charcoal and graphite. 5 30. The reductant feed material defined in any one of claims 26 to 29 wherein the hydrocarbon polymer comprises 20-60 wt.% of the total weight of the hydrocarbon polymer and the other reductant supplied into the furnace. 10 31. The reductant feed material defined in any one of claims 26 to 30 wherein the hydrocarbon polymer comprises

35-45 wt.% of the total weight of the hydrocarbon polymer and the other reductant supplied into the furnace.