Method For The Production Of Metal Products Starting From Ferrous Material, By Means Of An Electric Arc Furnace

Abstract

Method for the production of metal products starting from ferrous material, by means of an electric arc furnace.

Claims

1. Method for the production of metal products starting from ferrous material, by means of an electric arc furnace, comprising: preheating and melting of said ferrous material by the combined action of the electric arc of said electric arc furnace, and of the combustion of a fuel, wherein said ferrous material is transformed into a molten metal material; refining of said molten metal material, which is transformed into a molten metal product by the action of a reducing agent generated from carbon sources; wherein a polymeric material is used in at least partial replacement of said fuel for said preheating and said melting and/or said carbon sources for said refining, wherein said polymeric material derives from waste, from refuse or from recycling, in particular from domestic, urban and/or industrial waste, and comprises two or more of: Polyethylene (PE), Polypropylene (PP), Polyethylene terephthalate (PET), High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), or combinations thereof wherein said polymeric material has a calorific value not lower than 30 MJ/Kg, referred to the dry sample after 4 hours of drying at 105° C., wherein said polymeric material comprises a polymeric fraction greater than 50% by weight on the dry sample.

2. Method as in claim 1, wherein said polymeric material derives from or comprises secondary raw plastic materials.

3. Method as in claim 1, wherein said polymeric material comprises at least one thermoplastic polymer, in particular a thermoplastic polyolefin, or a mixture of thermoplastic polymers, in particular a mixture of thermoplastic polyolefins.

4. Method as in claim 1, wherein said method also comprises a step to supply fuel and a step to supply carbon sources, wherein said polymeric material is supplied in at least partial replacement of said fuel and/or said carbon sources.

5. Method as in claim 4, wherein the supply of carbon sources and/or the supply of fuel provide that said polymeric material is finely shredded or pulverized, in order to be picked up and moved.

6. Method as in claim 4, wherein the supply of carbon sources and/or the supply of fuel provides that said polymeric material is loaded into the electric arc furnace together with the metal material by mechanical transport means.

7. Method as in claim 1, wherein the mass substitution ratio between said carbon sources and said polymeric material is in a range comprised between 0.1 and 1, preferably between 0.1 and 0.99, even more preferably between 0.5 and 0.75.

8. Method as in claim 1, wherein the mass replacement ratio between said fuel and said polymeric material is between 0.2 and 1, preferably between 0.5 and 0.99.

9. Method as in claim 1, wherein said polymeric material comprises a polymeric fraction greater than 65% by weight, preferably higher than 80% by weight.

10. Method as in claim 1, wherein said polymeric material comprises a chlorine content not higher than 2%, referred to the dry sample after 4 hours of drying at 105° C.

11. Method as in claim 1, wherein said polymeric material also comprises one or more elastomers, in particular styrene butadiene rubber and/or natural rubber.

12. Method as in claim 1, wherein said polymeric material comprises a sulfur content not higher than 5000 mg/kg, according to the DIN 51724-3 (2012-07) method.

13. Method as in claim 1, wherein said polymeric material is densified.

14. Method as in claim 1, wherein said polymeric material has an ash residue at 550° C. lower than 8%, evaluated according to the CNR IRSA 2 Q64 Vol. 2 1984 method.

15. Method as in claim 1, wherein preheating and melting of said ferrous material constitute a single operating step of said method.

16. Use of a polymeric material in a method for the production of metal products starting from ferrous material, by means of an electric arc furnace, comprising: preheating and melting of said ferrous material by the combined action of the electric arc of said electric arc furnace and of the combustion of a fuel, in which said ferrous material is transformed into a molten metal material; refining of said molten metal material, which is transformed into a molten metal product by the action of a reducing agent generated from carbon sources; wherein said polymeric material is used in at least partial replacement of said fuel for said preheating and melting and/or of said carbon sources for said refining; wherein said polymeric material derives from waste, from refuse or from recycling, in particular from domestic, urban and/or industrial waste, and comprises two or more of: Polyethylene (PE), Polypropylene (PP), Polyethylene terephthalate (PET), High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), or combinations thereof, wherein said polymeric material has a calorific value not lower than 30 MJ/Kg, referred to the dry sample after 4 hours of drying at 105° C., wherein said polymeric material comprises a polymeric fraction greater than 50% by weight on the dry sample.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0079] These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:

[0080] FIG. 1 shows the result of calorific value analysis of samples of polymeric material in accordance with embodiments of the present invention;

[0081] FIG. 2 shows the result of analysis of chlorine content in samples of polymeric material in accordance with embodiments of the present invention;

[0082] FIG. 3 shows the result of analysis of sulfur content in samples of polymeric material in accordance with embodiments of the present invention;

[0083] FIG. 4 shows by means of a block diagram example embodiments of the method of the present invention.

[0084] To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can conveniently be incorporated into other embodiments without further clarifications.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

[0085] We will now refer in detail to the various embodiments of the invention, of which one or more examples are shown in the attached drawings. Each example is supplied by way of illustration of the invention and shall not be understood as a limitation thereof. For example, the characteristics shown or described insomuch as they are part of one embodiment can be adopted on, or in association with, other embodiments to produce another embodiment. It is understood that the present invention shall include all such modifications and variants.

[0086] Before describing these embodiments, we must also clarify that the phraseology and terminology used here is for the purposes of description only, and cannot be considered as limitative.

[0087] Unless otherwise defined, all the technical and scientific terms used here and hereafter have the same meaning as commonly understood by a person with ordinary experience in the field of the art to which the present invention belongs. Even if methods and materials similar or equivalent to those described here can be used in practice and in the trials of the present invention, the methods and materials are described hereafter as an example. In the event of conflict, the present application shall prevail, including its definitions. The materials, methods and examples have a purely illustrative purpose and shall not be understood restrictively.

[0088] All the percentages and ratios indicated refer to the weight of the total composition (w/w), unless otherwise indicated.

[0089] All percentage ranges shown here are provided with the provision that the sum with respect to the overall composition is 100%, unless otherwise indicated.

[0090] All the intervals reported here shall be understood to include the extremes, including those that report an interval “between” two values, unless otherwise indicated.

[0091] The present description also includes the intervals that derive from uniting or overlapping two or more intervals described, unless otherwise indicated.

[0092] The present description also includes the intervals that can derive from the combination of two or more values taken at different points, unless otherwise indicated.

[0093] The Applicant has developed a polymeric material to be used in iron and steel methods which use an electric arc furnace for the production of metal products from ferrous material.

[0094] In some embodiments, the polymeric material developed by the Applicant comprises a mixture of heterogeneous plastic materials.

[0095] In some embodiments, the heterogeneous plastic materials can derive from waste material, from refuse or from recycling, or derive from virgin material, that is, not from recycling, waste or refuse.

[0096] For example, the heterogeneous plastic materials that can be used can comprise waste or recycled plastic materials, for example from domestic, urban and/or industrial refuse, of a heterogeneous type and possibly with a high plastic content.

[0097] The waste plastic materials can for example comprise waste or recycling of household material, industrial waste, packaging, disposable plastic objects, plastic refuse in general.

[0098] In some embodiments, the heterogeneous plastic materials can also derive from recycling methods of these waste plastic materials.

[0099] In particular, by way of a non-limiting example, the waste plastic materials can be collected in special disposal or selection plants, and possibly sent to special recycling plants, equipped to further select the various components of the plastic.

[0100] By way of example, a typical separation that occurs in these plants separates reusable waste plastic materials, for example because they lend themselves to be melted again and processed to form new products, and non-reusable waste plastic materials, for example because if subjected to new heat or chemical treatments they can degrade and possibly carbonize.

[0101] Plastic materials coming from recycling and suitable for a new use are typically indicated as secondary-raw plastic materials.

[0102] Plastic materials, refuse and/or secondary-raw materials, typically comprise a large variety of heterogeneous polymers with variable chemical structures.

[0103] In some embodiments, the polymeric material developed by the Applicant therefore comprises plastics and polymers in all their forms, including, by way of a non-limiting example, in the form of raw material, secondary raw material, by-product, refuse, or combinations thereof.

[0104] In some embodiments, the polymeric material can comprise at least one thermoplastic polymer, for example a thermoplastic polyolefin, or a mixture of thermoplastic polymers, for example thermoplastic polyolefins.

[0105] In some embodiments, the polymeric material can comprise a mixture of polymer-based recycled plastic materials.

[0106] In some embodiments, the polymeric material can comprise any plastic polymer whatsoever, for example Polyethylene (PE), Polypropylene (PP), Polyethylene terephthalate (PET), High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), or combinations thereof, advantageously two or more of the polymers as above, or combinations thereof.

[0107] In some embodiments, the polymeric material comprises a binary mixture of Polyethylene (PE) and Polypropylene (PP).

[0108] The polymeric material can possibly also comprise, in addition to at least one of these plastic polymers, also one or more elastomers, for example styrene butadiene rubber (SBR) and/or natural rubber (NR).

[0109] In some embodiments, the polymeric material of the present invention can therefore include a polymeric fraction, which in some embodiments can be present in a percentage higher than 50%, preferably higher than 65%, even more preferably higher than 80% by weight on the dry sample, and a non-polymeric fraction, in a percentage substantially complementary to the polymeric fraction.

[0110] Advantageously, the non-polymeric fraction of the polymeric material can include heterogeneous materials, for example inert materials, or even materials suitable to provide additional characteristics to the polymeric material, so as to guarantee a wide versatility of use for it.

[0111] In particular, it can be advantageous to use the polymeric material with a low percentage of polymeric fraction, in any case within the ranges indicated above, in iron and steel operations that require particular characteristics or functionalities, which can be provided by means of the materials included in the non-polymeric fraction.

[0112] On the other hand, it can be advantageous to use the polymeric material with a high percentage of polymeric fraction, in any case within the ranges indicated above, in iron and steel operations that require high carbon contents and/or high calorific value.

[0113] Here and in this description, when the calorific value is mentioned, we always refer to the so-called lower calorific value (LCV), normally determined by subtracting the latent heat of vaporization of the water formed during combustion from the higher calorific value (HCV).

[0114] In fact, in these cases a high content of heterogeneous polymers ensures a high fraction of carbon and hydrogen in the polymeric material.

[0115] Thanks to this high fraction of carbon and hydrogen, the polymeric material is suitable to be used as a fuel in combustion reactions, in which the carbon contained in the polymers is converted into, for example, carbon monoxide and/or carbon dioxide.

[0116] In some embodiments, high polymeric fractions, containing carbon and hydrogen, can be associated with a high calorific value.

[0117] Advantageously, by varying the percentages of polymeric and non-polymeric fraction it is possible to modulate the carbon content and the calorific value of the polymeric material.

[0118] In some embodiments, the polymeric material can have a calorific value not lower than 30 MJ/Kg, referred to the dry sample after 4 hours of drying at 105° C., in accordance with regulation UNI EN 15400, or other recognized equivalent international standard.

[0119] For example, FIG. 1 shows the results of five calorific value analyses performed on five different samples of polymeric material, in which it is possible to observe that the calorific value is always higher than 30 MJ/Kg.

[0120] In some embodiments, some substances, potentially unwanted, coming from waste plastic materials and/or from refuse, may also be present in the non-polymeric fraction of the polymeric material.

[0121] However, the Applicant has found that these substances, even when present, constitute a minimal and negligible fraction of the polymeric material, and do not exceed the technical standards and legislation in force and applicable for products used in the iron and steel industry.

[0122] For example, in some embodiments, the polymeric material can comprise a chlorine content not higher than 2%, referred to the dry sample after 4 hours of drying at 105° C., in accordance with regulation UNI EN 15408, or other recognized equivalent international standard.

[0123] FIG. 2 shows the results of various analysis procedures aimed at quantifying the chlorine fraction contained in five samples of polymeric material.

[0124] It is possible to observe that, in these examples, the maximum values of chlorine fraction recorded are around 13000 mg/Kg, which corresponds to 1.3% by weight. This value is lower than the 2% limit threshold provided by legislation for the use of materials in iron and steel processes. Furthermore, FIG. 3 shows the results of analyses conducted on five samples of polymeric material for the quantification of the sulfur content.

[0125] It is possible to observe how the polymeric material can comprise very small fractions of sulfur, even equal to zero.

[0126] For example, bar 4 of FIG. 4 shows sulfur values just above 1000 mg/Kg, which corresponds to about a fifth of the limit value for the sulfur content for iron and steel use.

[0127] In general, sulfur fractions of less than 5000 mg/kg were recorded in all cases, which corresponds to the limit value for the sulfur content in materials for iron and steel use.

[0128] Therefore, in some embodiments, the polymeric material can comprise a sulfur content not higher than 5000 mg/kg, which corresponds to 0.5% by weight, according to the DIN 51724-3 (2012-07) method, or other equivalent recognized international standard.

[0129] In some embodiments, by suitably selecting the polymeric material, so that it advantageously comprises two or more of: Polyethylene (PE), Polypropylene (PP), Polyethylene terephthalate (PET), High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), or combinations thereof, it is possible to obtain even more advantageous values of calorific value, chlorine content and sulfur content, as summarized in the table below for analyses conducted on five samples of selected polymeric material as described above (the analysis methods used are as above):

TABLE-US-00002 Analysis Analysis Analysis Analysis Analysis 1 2 3 4 5 Cl % 0.36 0.36 0.48 0.37 0.53 S % 0.05 0.12 0.0584 0.173 0.07 LCV 43 36.1 39.1 35.41 35.68 MJ/Kg

[0130] In some embodiments, therefore, it is possible to obtain calorific values higher than 35 MJ/kg.

[0131] In other embodiments, it is possible to obtain chlorine content values lower than 1%, advantageously lower than 0.6%.

[0132] In other embodiments, it is possible to obtain sulfur content values lower than 1%, advantageously lower than 0.6%.

[0133] Furthermore, in some embodiments, the percentage of residual humidity present in the polymeric material of the present invention can be controlled and adjusted if necessary.

[0134] Advantageously, it is possible to vary the percentage of residual humidity according to requirements, giving versatility of use to the polymeric material of the present invention.

[0135] In some embodiments, the polymeric material can have a residual humidity not higher than 10% by weight, preferably not higher than 2% by weight.

[0136] The polymeric material can also be conformed in variable shapes and sizes according to requirements.

[0137] For example, in some embodiments it can be shaped as spheres, pellets or granules of variable diameter, or flakes, densified, or even in cylindrical, discoid or elongated shapes.

[0138] In some embodiments, the polymeric material can also be finely shredded or pulverized, to be picked up and moved for example by streams of air and/or gas at high pressure or high speed.

[0139] For example, in some embodiments the polymeric material can be made as granules with a diameter varying between 0.1 mm and 10 mm, and in other embodiments this range can also be wider, for example between 0.1 mm and 300 mm.

[0140] In some embodiments, the polymeric material is densified, that is, it has undergone a densification operation, in which the fragmented material is processed to obtain a densified material, to improve its physical properties.

[0141] With the term densification we mean any process of volumetric reduction attributable to agglomeration, conglomeration, extrusion, pelletization, homogenization, drawing and plasticization, or their derivatives, such as “densifier”, “densified”, “plasticizer” or “plasticized”, “conglomerator” or “conglomerate”, and so on. Each of these processes can be understood as “densification”, that is, a process through which the polymer fraction of a primary heterogeneous mixture, or even only part of it, is taken to melting point, so that it is thickened and homogenized, for example due to thermal heating effect and friction effect due to rubbing. Here and in the following description, it will be possible to use equivalently also the term “densification”, or its derivatives, such as “densifier” or “densified”, or the term “agglomeration”, or its derivatives, such as “agglomerate” and “agglomerator” as a replacement for “plasticization” or its derivatives, such as “plasticizer” or “plasticized”.

[0142] In some embodiments, the plasticization operation can be carried out using an extruder, possibly a twin-screw extruder.

[0143] In some embodiments, this operation can be performed for example by feeding the fragmented polymeric material by means of a hopper into the plasticizer, for example into the extruder, which can work in a variable temperature range, suitable to melt the materials that make up the fragmented material.

[0144] After being cooled, the densified polymeric material can be directly cut or sectioned to size at exit from the plasticizer, for example by means of shears, to obtain densified material of variable shapes and sizes, as a function of an exit section of the plasticizer and the cutting cadence.

[0145] In some embodiments, after the cooling, the densified polymeric material can be subjected to fragmentation in a special fragmentation device. For example, the fragmentation can be a grinding, which can typically be carried out by means of a mill.

[0146] The densified polymeric material can then be fragmented into the desired sizes, to obtain a polymeric material in the desired fragmented form, for example in the form of granules, grains, particles or similar fragmented forms, hereafter referred to as granules for simplicity.

[0147] In some embodiments, the granules of densified polymeric material can have sizes comprised between 0.01 mm and 300 mm.

[0148] In possible implementations, the granules of densified polymeric material can have sizes comprised between 0.01 mm and 3 mm.

[0149] In other possible implementations, the granules of polymeric product can have sizes comprised between 3 mm and 10 mm.

[0150] In still other possible implementations, the granules of polymeric product can have sizes comprised between 10 mm and 300 mm.

[0151] In some embodiments, the densified and fragmented polymeric material can be subjected to screening so as to obtain a polymeric material with uniform sizes.

[0152] On the basis of the characteristics of the polymeric material in accordance with the embodiments described here, the Applicant has used the polymeric material of the present invention in a method for the transformation of ferrous material into a metal product by means of an electric arc furnace.

[0153] Embodiments of the method of the present invention are described by means of the block diagram shown in FIG. 4.

[0154] The method initially provides the supply of ferrous material A.

[0155] The ferrous material can comprise any material whatsoever containing a suitable quantity of metal, suitable to be melted in an electric arc furnace, such as for example scrap metal materials or products, ferrous matrix materials, scrap, in particular ferrous scrap.

[0156] The ferrous material can be for example stored in a warehouse or scrap yard, or in a storage warehouse.

[0157] The ferrous material is loaded, in known modes, into an electric arc furnace of a steel plant, also in itself known, for the production of a metal product starting from ferrous material by means of an electric arc furnace.

[0158] The ferrous material can for example be loaded by a loading apparatus, by means of one or more charge baskets and/or by means of a conveyor line, for example provided with a conveyor belt.

[0159] The method can also provide the supply of fuel B and/or polymeric material.

[0160] The fuel, in itself known, can comprise natural gas, methane and/or other hydrocarbons, oil derivatives, coke derivatives, coke dust, anthracite in various sizes, hydrogen, methane and/or syngas.

[0161] In some embodiments, the polymeric material can be used in at least partial replacement of the fuel.

[0162] Advantageously, the characteristics of high calorific value and low ash fraction of the polymeric material allow an advantageous use thereof in addition to, or at least in partial replacement of, the fuel.

[0163] By way of example, the gaseous fuel (natural gas) normally used typically varies between 3 Nm.sup.3/ton and 6 Nm.sup.3/ton of loaded scrap (metal charge in the electric arc furnace), while the solid fuel generally used in the state of the art, for example charge anthracite, coke dust, can vary from 0.2% to 2% of the weight of the loaded scrap. For example, between 0.2% and 1.5% by weight of solid fuel can be introduced, in particular between 0.4 and 1.3%.

[0164] Here, in the present description and in the claims, with the expression “replacement ratio” or “replacement ratio by mass” or “replacement ratio by weight” we mean the quantity of generic fuel and/or carbon source that it is possible to remove from the process to produce a metal product, replacing it with the polymeric material described here, correlated to the total amount of solid fuel and/or carbon source normally used. For example, in a process in which the total amount of fuel normally used, for example anthracite, is equal to 1000 kg, and it is possible to remove it entirely and instead use the polymeric material according to the embodiments described here, then the replacement ratio will be 1:1. Otherwise, if only 250 kg can be removed, the replacement ratio will be 0.25. In other words, we therefore mean the ratio between quantity of fossil source removed/quantity of fossil source used previously, where the quantities are typically expressed in kilograms, and by fossil source we mean a generic fuel or carbon source, depending on the case.

[0165] In some embodiments, the replacement ratio between generic fuel, for example solid, and polymeric material can be variable, based on the percentage of polymeric fraction present in the polymeric material and on the type of fuel used, its physical form, the kinetics of use and the reactivity in the thermodynamic system in which it is used. For the purposes of the present description, the definition provided hereafter applies to the term “replacement ratio”.

[0166] In some embodiments, the mass replacement ratio between generic fuel and polymeric material described here can be comprised between 0.2 and 1, preferably between 0.5 and 0.99.

[0167] The modes for introducing the polymeric material into the electric arc furnace can vary, for example on the basis of the type of electric arc furnace used, the sizes of the polymeric material and the generic fuel replaced.

[0168] In some embodiments, the polymeric material can be directly introduced into the electric arc furnace together with the ferrous material.

[0169] In some embodiments, the polymeric material can be loaded directly into the electric arc furnace by mechanical transport means.

[0170] The mechanical transport means can for example comprise conveyor belts, possibly integrated with continuous feed technologies, which feed the polymeric material directly into the arc furnace by means of an aperture made in the crucible.

[0171] Other embodiments can provide that the polymeric material is loaded into the basket together with the metallic material.

[0172] In these embodiments, the sizes of the polymeric material can be variable, preferably reduced to facilitate mixing.

[0173] In some embodiments, the polymeric material can be introduced into the electric arc furnace by means of introduction lances, located, for example, at the base of the crucible.

[0174] In these embodiments, the polymeric material can be taken to a suitable size so as to be pneumatically transportable and injectable, for example suitable to be moved by streams of air or gas at high pressure and speed.

[0175] Possibly, the polymeric material can be introduced by means of lances which allow to have combined streams of oxygen, polymeric material and/or fuel, for example natural gas and/or other types of fossil fuels.

[0176] The method of the present invention therefore provides the preheating C of the ferrous material, aimed at increasing the temperature of the ferrous material, by combustion of the fuel and/or the polymeric material.

[0177] During the preheating C, the heat is provided by the electric arc, for example even reaching peaks of 11000° C., and by special burners which burn a combined stream of oxygen, fuel and/or polymeric material, or also by means of preheating fumes.

[0178] The provision of heat removes the humidity and the volatile components from the ferrous material.

[0179] Advantageously, the use of polymeric material in combustion processes allows to obtain quantities of heat comparable or higher than those obtainable for example from the combustion of natural gas, but with significantly more advantageous production costs, transport costs and availability of usable product, as well as optimized energy performance.

[0180] Advantageously, the low fraction of residual humidity contained in the polymeric material promotes, in the preheating process of the ferrous material, the removal of the humidity and of the volatile components.

[0181] Advantageously, the low fractions of sulfur and chlorine contained in the polymeric material keep the emission of post-combustion pollutants into the atmosphere, such as sulfur dioxide and/or dioxins, at low levels.

[0182] Advantageously, the emissions of sulfur and chlorine-based pollutants into the atmosphere related to the combustion of the polymeric material are lower compared to the emissions relating to fossil fuels, in particular coke, anthracite, and compared to the replacement sources of traditional fuels such as ELT and ASR.

[0183] Following the preheating C of the ferrous material, the melting D of the ferrous material is provided, in which a molten bath of molten metal material is formed in the crucible of the electric furnace.

[0184] In the melting D, the ferrous material therefore passes from the solid state to the liquid state.

[0185] Also in the melting D, as for the preheating C, the heat can be generated by the electric arc of the electric arc furnace and by special burners, which burn combined streams of oxygen, fuel and/or polymeric material.

[0186] Operational details related to the melting D and related to the use, to the characteristics and to the modes of use of the polymeric material in this step can therefore be similar to what was described above with regards to the preheating C.

[0187] In some embodiments, considering the similarity, the preheating C and the melting D can form a single heating step aimed at melting, in which the polymeric material described here is used.

[0188] In some embodiments, the supply of ferrous material A, the supply of fuel B, the preheating C and the melting D can be carried out cyclically.

[0189] For example, in the event the ferrous material has a considerable bulk and completely fills the crucible of the electric arc furnace, it is possible to partly melt it to reduce its bulk, and subsequently proceed with a new introduction of ferrous material, directly into the molten bath.

[0190] According to the present invention, a refinement E is also provided, in which the molten metal material of the molten bath is transformed into the final metal product.

[0191] The refinement E provides to give the steel the desired steel grade by the action of a suitable reducing agent, for example CO and H.sub.2, which can be generated by one or more suitable carbon sources.

[0192] In some embodiments, the polymeric material can be used in at least partial replacement of the carbon sources, thanks to its high carbon and hydrogen content.

[0193] In embodiments described with FIG. 4, parallel to the refinement E, the supply of carbon sources F and/or of the polymeric material of the present invention is then also provided.

[0194] Typical traditional carbon sources can comprise, for example, anthracite, MET-coke, Pulverized Coal Injected (PCI), GPC (Green Petroleum Coke) or other types of fossil carbon sources.

[0195] It is obvious that operational details and introduction modes described with reference to the step of supplying fuel B can, in some embodiments, also be used with reference to the step of supplying carbon sources F, and different modes can be used on each occasion, according to specific needs.

[0196] In some embodiments, in the step of supplying carbon sources F, the polymeric material is preferably injected below the slag, promoting the reduction of the oxides present. In other embodiments, it is loaded into the basket, together with the ferrous material, and/or directly into the electric arc furnace, by means of the mechanical transport means.

[0197] By way of example, the reducing agent is generated by the reaction of the carbon sources and/or the polymeric material with oxygen, under appropriate kinetic and thermodynamic conditions.

[0198] Typically, the reducing agent can comprise carbon monoxide and/or hydrogen.

[0199] In some embodiments, the carbon monoxide can be generated from carbon dioxide, or from the carbon brought by the carbon source and/or the polymeric material.

[0200] By way of example, the Applicant has verified that at least the polymeric fraction of polymeric material, in the working conditions of the electric arc furnace, can undergo reactions from which carbon monoxide and hydrogen are produced.

[0201] The carbon monoxide and hydrogen thus produced, then take part in the reduction reaction mechanisms, for example of the iron oxides, from which metallic iron is produced.

[0202] Typically, the flows of carbon sources for producing medium carbon steel are between 0.2% and 1.5%, preferably between 0.5% and 1.3%.

[0203] In some embodiments, the mass replacement ratio between carbon sources and the polymeric material can vary in a range comprised between 0.1 and 1, for example between 0.1 and 0.99, preferably between 0.5 and 0.75.

[0204] Furthermore, in some embodiments, during the refinement E, the streams of gas inside the molten bath, for example of carbon monoxide, allow to reduce the iron oxide content.

[0205] This operation, which promotes the generation of CO and H.sub.2, combined with other operations, can lead to the swelling of the slag (foaming practices), necessary for a correct optimization of the process.

[0206] The molten metal material present in the molten bath, once the desired composition has been reached, becomes molten metal product.

[0207] Subsequently, the unloading, or tapping, G of the molten metal product from the electric arc furnace can take place.

[0208] By way of example, the unloading, or tapping, G can be achieved by tilting the crucible of the electric arc furnace, typically made horizontally pivoting, so as to allow the outflow of the molten metal product, for example into a ladle.

[0209] The Applicant has further conducted experimental comparison tests in the use, on the one hand, of the polymeric material in accordance with the present description, and on the other hand of ASR (Automotive Shredded Residues) as a substitute for fossil sources in the production of metal products starting from ferrous material, by means of an electric arc furnace.

[0210] From the experimental data shown below in the table, the Applicant has surprisingly found that the polymeric material described here advantageously acts as a stabilizer of the production process of metal products starting from ferrous material, by means of an electric arc furnace.

[0211] In particular, the Applicant has found that, for the same boundary conditions such as scrap type, electrical and chemical input, at the end of the melting and refining cycle some Key Performance Indicators (KPI) of the steel appear to have, using the polymeric material described here, a reduced variability. Downstream of the analyses carried out on castings carried out with ASR and other castings carried out, by comparison, with the polymeric material described here, the data shown in the following table were obtained for carbon content at tapping (% C) and temperature detected at tapping (° C.).

TABLE-US-00003 Using the polymeric Parameter Using ASR material described here Tapping 0.07-0.47 0.10-0.20 % C Tapping 1540-1620 1595-1610 ° C.

[0212] Therefore, it is evident that compared to the performance of the process with the use of ASR, the use of the polymeric product reduces the variability of significant KPIs of steel, in particular the parameters of carbon content at tapping (% C) and temperature measured at tapping (° C.). These parameters are fundamental since, in the iron and steel industry, they generally indicate whether the process is efficient or not, consequently a limited or small variability is considered extremely advantageous.

[0213] It is clear that modifications and/or additions of steps may be made to the method as described heretofore, without departing from the field and scope of the present invention.

[0214] It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of method, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

[0215] In the following claims, the sole purpose of the references in brackets is to facilitate reading: they must not be considered as restrictive factors with regard to the field of protection claimed in the specific claims.