EP4624596A1

EP4624596A1 - Method for producing metallic iron melt

Info

Publication number: EP4624596A1
Application number: EP24167300.3A
Authority: EP
Inventors: Pande Nishant Prasad; Jenny WIKSTRÖM; Shabbir Taherbhai LAKDAWALA
Original assignee: Luossavaara Kiirunavaara AB LKAB
Current assignee: Luossavaara Kiirunavaara AB LKAB
Priority date: 2024-03-28
Filing date: 2024-03-28
Publication date: 2025-10-01
Also published as: WO2025202431A1

Abstract

Method for producing metallic iron melt, comprising: in a furnace, providing an iron bearing material having a metallization degree of at least 95 wt.%, a carbon content of at most 0.1 wt.%, and a gangue content of less than 3 4 5wt.% or less, and heating said iron material in said furnace to a temperature of 1600-1700 °C in a controlled atmosphere, thereby forming a metallic iron melt phase and a slag phase.

Description

TECHNICAL FIELD

The present invention relates to a method for producing metallic iron melt.

BACKGROUND ART

Direct reduced iron (DRI)-based processes are gaining popularity for reduction of iron ore. The temperature inside a DR shaft is generally below 1000 °C, leaving gangue-oxides inside the iron ore unreduced. As a result, the produced DRI essentially comprises metallic iron and some iron oxide, FeO, with some entrapments of unreduced gangue-oxides.
Unlike molten hot metal produced by blast furnace, the DRI remains in solid form and requires subsequent melting. A subsequent stage of melting and refining can be performed in e.g. an electric arc furnace (EAF). A typical EAF has relatively inferior refining capabilities compared to a traditional basic oxygen furnace (BOF).
WO2023204063A1 and WO2023204069A1 show a direct reduction step in which iron ore is brought into contact with a reducing agent under heating to obtain DRI. Thereafter the DRI is melted in an induction-melting furnace to obtain molten iron and to remove gangue contained in the DRI. The slag produced is discharged to the outside of the melting furnace. The melting step may include blowing oxygen gas into the molten iron during a portion or all of the melting step, and addition of a slag composition modifier. This is done to completely melt the slag with high fluidity for a smooth melting operation.
Such a method may increase the slag volume and the dissolved oxygen content in the Fe-melt, necessitating extensive de-oxidation treatment of the melt at a secondary metallurgy unit.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method for producing a metallic iron melt with at least 99.9 wt.% or more iron.
The invention is defined by the appended independent patent claims. Non-limiting embodiments emerge from the dependent claims, the appended drawings, and the following description.
According to a first aspect there is provided a method for producing metallic iron melt, comprising: in a furnace, providing an iron bearing material having a metallization degree of at least 95 %, a carbon content of at most 0.1 wt.%, and a gangue content of 5 wt.% or less, and heating the iron material in the furnace to a temperature of 1600-1700 °C in a controlled atmosphere, thereby forming a metallic iron melt phase with iron and a slag phase.
The metallization degree represents the extent to which iron bearing material (usually in the form of direct reduced iron or DRI) has been converted into metallic iron. It represents the proportion of metallic iron (Fe) in the total iron content of the material and indicates how much of the iron has been reduced from its original oxide form to metallic iron. Here, the metallization degree is at least 95 %, i.e. 95 % of the iron exists as metallic iron, while the remaining 5% is still in the oxide form. Preferably, the metallization degree is at least 97%.
The carbon content of the iron material is at most 0.1 wt.%. Preferably, the carbon content is as low as possible, thereby the present method can provide a metallic iron melt phase with 99 wt.% or even 99.9 wt.% iron. The carbon content may depend on factors such as the reducing gas used to produce the iron bearing material in a direct reduced iron (DRI) furnace, the type of iron ore, and the specific production process. When using a DR process in which the reducing gas is 100% or close to 100% hydrogen, ammonia or ammonia mixed with hydrogen, an iron bearing material with a low or a minimal amount of carbon is produced.
The presence of carbon in significant concentrations, for instance above0.1 wt.% in the iron bearing material could result in the reduction of gangue oxides to a certain extent during melting, thereby introducing tramp elements into the Fe-melt.
The above described method aims to capitalize on the advantage offered by H₂-based reduction, which yields carbon-free iron-bearing material for subsequent melting. DRI produced through existing routes using natural gas or a mixture of natural gas and hydrogen typically contains carbon within the range of 1-4 wt.%, making such a DRI unsuitable for the proposed process.
It is important to acknowledge that in real-world conditions, carbon-free iron-bearing material may still contain trace amounts of carbon as a contaminant, but in very low concentrations (e.g., ppm-levels), due to various intermediate handling and transportation stages.
A low carbon content is crucial for ensuring the quality of the Fe-melt. Higher carbon content negatively affects Fe-melt quality, thereby compromising the effectiveness of the proposed process. To maintain the claim of producing a nearly impurity-free iron melt, it is vital to implement a stringent carbon limit.
The iron bearing material may also comprise smaller amounts of one or more additional elements such as Si, V, Cr, Ti, Mn, P, S, and/or Al in the gangue, mainly as oxide mineral forms. Such materials are then provided in the produced slag phase and may be extracted therefrom. The gangue content of the iron bearing material should be at most 5 wt.%.
During the above-describe method the gangue oxides form a slag melt or crust, encapsulating unreduced FeO-content present in the iron bearing material.
A slight increase in gangue content by e.g. 0.5 wt% has sizeable effect on the method. This equates to approximately 15-20 kg of additional slag per ton of melted Fe. In practical terms, such an increase in slag weight translates to a proportionate significant increase in slag volume during melting, given the lower density of slag compared to molten iron.
With the above-described method, increase in slag volume from iron oxidation, i.e. iron losses, and dissolution of oxygen in the Fe-melt may be restricted. The metallic iron melt phase may comprise at least 99 wt.% or at least 99.9 wt.% iron. Such a metallic iron melt phase can be used to make clean or even ultra-clean steel grades (after minor adjustments in a secondary metallurgy unit (for e.g. in a Ladle Furnace)).
The temperature range of 1600-1700°C is based on considerations regarding the balance between achieving complete melting of the iron melt while preventing complete melting of the slag phase comprising the gangue oxides.
It is understood that a controlled atmosphere is affected/controlled by parameters such as flow rate, pressure, any gas provided in the furnace etc. The controlled atmosphere may e.g. include vacuum, an inert atmosphere, or a reducing atmosphere in the furnace. The controlled atmosphere in the furnace is used to prevent iron re-oxidation and to minimize oxygen ingress into the metallic iron melt.
An iron bearing material having a metallization degree of at least 95% and at most 5 wt.% gangue content is important for ensuring the effectiveness of the above-described method. These limits are set based on several key aspects of the process:

1) Firstly, the method aims to produce a clean iron melt while minimizing iron losses compared to conventional steelmaking practices. Dropping DRI metallization below 95% metallization would lead to higher iron losses compared to the levels typical in the conventional steelmaking routes.
2) Additionally, enrichment of valuable gangue oxides in the slag phase is a significant add-on aspect of the method, offering new opportunities for value recovery. However, at lower metallization levels, the slag becomes richer in FeO content, diminishing the concentrations of other valuable components such as V- and Ti oxides. This compromises the prospects of valuable elements recovery from the slag, affecting the overall value proposition of the method above.
3) Ensuring a minimal slag volume is crucial for effectively executing the method on a larger scale. A reduced slag volume facilitates smooth melting operation, even when the slag is partially molten. If the slag is completely melt, it would result in the undesirable partitioning of gangue elements between the metal and the slag.

Performing the same method as described above but without a controlled atmosphere in the furnace and using an iron bearing material that has a lower metallization degree, and/or a higher carbon content and/or a higher gangue content, i.e. a low-grade iron bearing material, may result in increased slag volume production, a higher degree of oxygen dissolution in the metallic iron melt, and, hence, a less clean metallic iron melt.
When there is a larger slag volume produced there is a need to completely melt the slag. This can be done by blowing oxygen into the furnace and by adding slag modifiers. This may result in iron losses and oxygen dissolution in the metallic melt, which typically occur during steelmaking. With the above method, slag melting will not be crucial due to the low slag volumes produced. Complete slag melting leads to phosphorus-partitioning and entry of phosphorus into the Fe-bearing metallic melt. Oxygen blowing and CaO-bearing material additions is then used to refine the Fe-melt from phosphorus contaminations. Such a method may also increase the dissolved oxygen content in the Fe-melt, necessitating extensive de-oxidation treatment of the melt at a secondary metallurgy unit.
Whereas, in the above method, any such oxygen-blowing treatment (which is typical in primary steelmaking stage in an electric arc furnace (EAF)/ basic oxygen furnace (BOF)) is not necessary. The addition of reagents or slag modifiers during melting may be limited, considering that the slag need not be completely molten. This would facilitate the production of a slag phase enriched in gangue oxides, containing valuable components such as vanadium, titanium, and chromium oxides.
As compared to conventional iron and steelmaking methods, the above-described method minimizes entry of tramp elements from gangue oxides into the molten metallic melt. This reduces the necessity of refining the metallic melt through extensive oxygen blowing, thereby, enabling significant reduction in iron losses and slag volume . Consequently, efficiency is enhanced and environmental impact is minimized as compared to the standard methods, and the production of high-quality steel products is facilitated.
Melting duration can vary depending on furnace specifications, including power and efficiency, as well as design factors influencing heat losses. In one example, it is at least 1 hour.
The provided iron bearing material may have a metallization degree of at least 96 %, at least 97 %, at least 98 %, or at least 99 %.
The provided iron bearing material may have a carbon content of at most 0.05 wt.%, or at most 0.01 wt.%.
The furnace may be heated to a temperature of 1600-1680 °C, or 1620-1650 °C.
The provided iron bearing material may have a gangue content of less than 4.5 wt.%, or less than 4 wt.%, or less than 3.5 wt.%, or less than 3 wt.%, or less than 2.5 wt.%, or less than 2 wt.%, or less than 1.5 wt.%, or less than 1 wt.%, or less than 0.5 wt.%.
The controlled atmosphere in the furnace may be a reducing atmosphere.
A (slightly) reducing atmosphere prevents re-oxidation of the Fe-melt with oxygen in atmospheric air. Common gases used in slightly reducing atmospheres include gas mixtures such as H₂-H₂O, CO-CO₂. The reducing atmosphere is highly dependent on thermodynamic factors such as temperature and pressure conditions in the furnace.
The controlled atmosphere in the furnace may have an absolute pressure of 100 Pa to atmospheric pressure.
Hence, the controlled atmosphere in the furnace may be a low vacuum, i.e. 3 kPa to 100 kPa, or a medium vacuum of 100 Pa-3 kPa.
Alternatively, the controlled atmosphere in the furnace is an atmospheric pressure (101.3 kPa).
The controlled atmosphere in the furnace may be an inert atmosphere.
The inert atmosphere may comprise argon, nitrogen or carbon dioxide.
The method described above may not comprise addition of oxygen gas or slag modifiers into the furnace.
The advantages of this are discussed above.
The method may further comprise recovering transition elements from the formed slag phase.
Such a step could give value-added transition element oxides enriched in the slag phase. For example, the valuable transition element oxides such as V₂O₅, TiO₂, and Cr₂O₃.
The method may comprise a step of providing the iron bearing material using a gas mixture comprising 90-100 vol.% hydrogen, 0-10 vol.% nitrogen, 0-10 vol.% H₂O through a Direct Reduction (DR) process.
The balance of the gas constituents may be <0.1 vol.%. These could be minor concentrations of gaseous species bearing element combinations such as H-O, N-O, N-H, H-N-O, etc.
The Direct Reduction (DR) process may be performed in a shaft furnace, in a multi hearth furnace, or in a rotary kiln furnace.
DRI produced using natural gas typically exhibits metallization levels below 95%. However, trial results from producing DRI using a gas mixture comprising 90-100 vol.% hydrogen (other components in the gas mixture being 0-10 vol.% nitrogen, 0-10 vol.% H2O, balance <0.1 vol%) as the reducing gas demonstrate a remarkable increase in metallization, consistently achieving levels above 99%. The resulting DRI would primarily consist of pure Fe (carbon-free), with minor amounts of FeO and unreduced gangue oxides.
The method may further comprise a step of providing the iron bearing material using 100% ammonia gas in a Direct Reduction (DR) process.
Such DRI primarily consists of pure Fe (carbon-free), with minor amounts of FeO, iron-nitrides and unreduced gangue oxides.
The method may comprising an alternative step of providing the iron bearing material using a mixture of ammonia gas and hydrogen gas in a Direct Reduction (DR) process.
Such DRI primarily consists of pure Fe (carbon-free), with minor amounts of FeO, iron-nitrides and unreduced gangue oxides.
The iron bearing material may in addition or alternatively comprise steel scrap.
The furnace used may be an induction furnace.
In an induction furnace, temperatures of 1600-1700°C can be achieved without any localized over-temperature. This is primarily attributed to the direct induction of eddy currents within the solid feed, leading to swift melting. Unlike conventional EAF and fuel-fired furnaces, the lack of excessively high localized temperatures in the induction furnace coupled with absence of carbon prevents the reduction of gangue oxides present in the DRI. As a result, melting of carbon-free DRI in an induction furnace would produce a relatively pure iron melt during the melting process, as impurities from gangue oxides will not join the metallic melt.
The furnace used may be an electrical-resistance furnace.
The method may further comprise to prepare the formed steel melt for refining in a secondary metallurgy unit.
Such treatments in the secondary normally comprise degassing, deoxidation and alloying treatments. Hence, the metallic iron melt produced with the above-described method is suitable for producing high-quality steel products without the need for extensive refining processes. To transform an iron melt into steel, a requisite level of carbon alloying is necessary. A significant advantage offered by the above-described method is the ability to add carbon to the melt at a stage where further refining may not be necessary. This feature is unprecedented. No prior process has provided such an advantage. The significance lies in the fact that the presence of carbon in the metallic iron melt during the refining in conventional processes continually facilitates reversion of tramp elements from the slag phase back into the melt. Intense oxygen blowing is then carried out to mitigate this impurity element reversion to and remove carbon from the metallic melt. However, this results in extensive iron reoxidation, an increase in slag volume, and significant consumption of resources. Moreover, after such rigorous oxygen blowing, the melt becomes nearly saturated with dissolved oxygen content, leading to complications during subsequent alloying stages. If adequate deoxidation of the melt is not conducted prior to alloying, valuable alloying elements are lost in the LF (Ladle Furnace) slag formed during secondary metallurgy treatment. Therefore, the above-described method addresses several challenges inherent in conventional steelmaking processes, including the challenge of sufficient refining when starting with a high-carbon iron melt (e.g., hot metal from blast furnace), the challenge of controlling iron losses during refining, and the challenge of controlling alloying element losses to the slag during secondary metallurgy alloying treatment.
The iron bearing material is provided in the furnace in a cold state.
With cold state is here meant at a temperature of 65°C or less.
The iron bearing material may be provided in the furnace in a hot state.
With hot state is here meant at a temperature of 300°C or more.
Thereby, the heat produced for forming the iron bearing material can be utilized in the melting process. Iron bearing material may be introduced into the furnace in the form of hot DRI, cold DRI, or a combination thereof.
According to a second aspect there is provided a metallic iron melt phase comprising at least 99.9 wt.% iron.
The process of molten melt processing during conventional steelmaking can be broadly categorized into three main steps: 1) the conversion of hot metal into crude steel during the primary steelmaking phase, 2) the conversion of crude steel into killed steel through deoxidation treatment in a secondary metallurgy unit, and 3) the conversion of killed steel melt into finished steel melt via alloying treatment in the secondary metallurgy unit. The iron melt produced through this new process will exhibit advantageous and significant differences compared to both crude steel melt and killed steel melt. The melt from the proposed new process will guarantee an iron content exceeding 99.9 wt%, unlike crude steel, which typically contains iron content below 99.9 wt%. Additionally, the iron melt will match or surpass killed steel melt in terms of dissolved oxygen content.
Determination of the steel melt composition for its total iron content may be performed using Optical Emission spectroscopy, with measurements conducted on quenched metallic stub samples. The dissolved oxygen content in the melt may be measured using melt probes operating on the principle of activity measurement in a galvanic cell utilizing solid electrolytes.
The provided metallic iron melt phase comprising at least 99.9 wt.% iron may have a dissolved oxygen content that is lower than the common levels of around 500 ppm found in crude steel, and around 50 ppm in semi-killed steel melts.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a process and set-up of producing metallic iron melt.
Fig. 2 shows extent of Fe-loss during melting of carbon-free DRI in an induction furnace based on mass-balance calculations.
Fig. 3 shows correlation between slag rate and Fe-content (or grade) of iron ore for the process shown in Fig. 1. The correlation is obtained through mass-balance, considering that the carbon-free DRI produced using this iron ore has a metallization of 99 wt.%.
Figs 4a and 4b show characteristics of slag obtained by melting carbon-free DRI produced from iron ore pellets in an induction furnace. The pellets have Fe-total ≈ 67.7%, and the ratio of CaO/SiO2 ≈ 1.35. These plots are obtained through mass-balance calculations.

DETAILED DESCRIPTION

Fig. 1 shows a process and set-up of producing metallic iron melt. Iron ore pellets 1 are introduced into a DR (Direct reduction) system 2 and an iron bearing material, (for instance DRI, or direct reduced iron), 4 is produced using e.g. 100% H₂ gas 3. Hot DRI 4a (e.g. using a Hot Link Bin) and/or cold DRI 5b, that has been cold down e.g. in a DRI cooler 5, is introduced into a furnace 6. The iron bearing material 4a, 5b introduced into the furnace 6 has a metallization degree of at least 95%, a carbon content of at most 0.1 wt.%, and a gangue content of 5wt.% or less. The furnace 6 may for e.g. be an induction melting furnace or an electrical-resistance furnace. In the furnace 6, the iron material is heated to a temperature of 1600-1700 °C in a controlled atmosphere, thereby forming a metallic iron melt phase 7 and a slag phase 8.
In order to obtain an iron bearing material having a metallization degree of at least 95%, a carbon content of at most 0.1 wt.%, and a gangue content of 5wt.% or less, a DRI process could be performed using a gas mixture comprising 90-100 vol.% hydrogen (other components in the gas mixture being 0-10 vol.% nitrogen, 0-10 vol.% H₂O, balance <0.1 vol.%), using 100% ammonia gas, or using a mixture of ammonia gas and hydrogen.

Laboratory scale experiment

A laboratory-scale DRI-melting experiment was conducted. Approximately 500 g of carbon-free DRI of metallization >97% produced from iron ore pellets was melted in a Tammann-furnace (electric resistance type laboratory-scale furnace) in an MgO-crucible. The furnace was heated to 1650°C, held at this temperature for 1 h, and subsequently cooled down to room temperature. Simultaneously, a purging flow of argon was maintained above the melting stock within the furnace throughout the course of the experiment. The solidified melt sample was later examined for chemical composition in an Optical Emission Spectrometer meant for analyzing metallic samples.

Chemical composition

Table 1 below presents a detailed chemical composition of the metallic melt produced from this test. Table 1: Chemical composition of the metallic melt obtained by melting highly metallized DRI (metallization > 97%) from pellets in a laboratory-scale Tammann furnace of 1650°C (compared with typical concentrations in crude steel after basic oxygen furnace (BOF) treatment (reference- R.J. Fruehon, Making, Shaping and Treating of Steel, Steel making and refining volume, AISE Steel Foundation, ed. 1998, United States Steel. Co. (1998)).

Elements	Concentration, wt. %	Typical concentration in crude steel after BOF
C	0.0032 ± 0.0015	0.04
Si	0.00032 ± 0.0019	0.005
V	0.0027 ± 0.00026
Cr	0.00013 ± 0.00005
Ti	0.0015 ± 0.00004
Mn	0.0030 ± 0.00021	0.138
P	0.0055 ± 0.00093	0.010
S	0.0024 ± 0.00024	0.010
Al	0.00017 ± 0.00009
N	0.0050 ± 0.00035	0.0050
Fe	99.9	99.797

Evidently, the iron bearing melt has very low concentrations of all tramp elements - C, Si, V, Cr, Ti, Mn, Mg, P, S, Al and N.

Fe loss

Iron losses occur in the operational steelmaking routes during the oxygen steelmaking step (in BOF/EAF). In this step, oxygen is introduced into the metallic melt to reoxidize impurity/tramp elements, allowing them to separate into a slag phase. This slag usually contains 15-30% FeO and is generated at a rate of approximately 100-150 kg/ton-crude steel across various operational steelmaking routes. In terms of iron losses (referring to the FeO lost to the steelmaking slag), the estimated range stands at 20-25 kg Fe-loss per ton of melted Fe.
In the proposed new route, which entails melting carbon-free DRI in an induction furnace, it becomes possible to eliminate the oxygen steelmaking step. This is because the iron bearing metallic melt would inherently be devoid of the tramp elements derived from gangue oxides. However, this new route would still involve Fe-loss, as the unreduced FeO in the DRI would join the slag phase during induction melting. The extent of Fe-loss in this form would depend solely on the degree of metallization of the carbon-free DRI undergoing melting in the induction furnace. This correlation of Fe-loss and DRI metallization is depicted in Fig. 2, which shows the extent of Fe-loss during melting of such produced carbon-free DRI in an induction furnace based on mass-balance calculations.
In the proposed new route, the resulting Fe-loss is significantly lower than that encountered in the conventional routes of steelmaking, provided, the carbon-free DRI is highly metallized (typically exceeding 97.5%). The estimated Fe-loss during induction melting of the DRI amounts to around 10kg/t-melted-Fe if its metallization is 99%.

Advantage of Minimal Slag-Metal interaction

In an induction furnace, the electrically non-conductive oxides (including gangue-oxides and FeO in DRI) constituting the slag phase undergo indirect heating through heat transfer from conductive metallic phases. Unlike EAF or BOF, induction furnace heating lacks chemical energy due to melt oxidation. These combined factors contribute to a significant reduction in chemical interaction between slag and metallic melt within an induction furnace, in contrast to EAF/BOF. This notably translates into lower dissolved oxygen concentrations in the Fe-melt.

Advantage of potential for Value-added products from obtained slag

In the above-described method, the slag would encompass the gangue oxides and FeO within the DRI. Accordingly, the slag rate and slag-composition would depend on - (1) DRI metallization, and (2) DRI Gangue content (equivalent to iron ore grade or Fe-content%). Fig. 3 illustrates a typical scenario of slag rate during melting of DRI, wherein the Fe-content within a hematite-based iron ore (the iron-bearing feed - Lump Ore/Sinters/Pellets/Briquettes) ranges between 60-70%, and the resultant DRI has a metallization of 99%.
In the above-described method, the slag generation rate is estimated to be below 100 kg/t-melted-Fe, provided that the iron ore's Fe-content exceeds 66%.
Considering a specific case of carbon-free DRI produced from pellets, Fe-content ≈ 67.7%, Fig. 4a demonstrates the relationship of slag rate for the above-describe method, with respect to (w.r.t) the degree of metallization for the carbon-free DRI produced from the pellets.

Correspondingly, Fig. 4b depicts FeO-content (%) variations in the slag w.r.t DRI-metallization. (In the used pellets, the CaO/SiO₂ ratio is maintained closely at around 1.35). Additionally, Table 2 lists the detailed slag-compositions with varying metallization of the DRI produced from ironore pellets derived from a high grade iron ore. Table 2: Calculated compositions of slag obtained by melting carbon-free DRI (of different degree of metallization) produced from iron ore pellets in an induction furnace.

DRI-Metallization, %	Slag composition
DRI-Metallization, %	CaO, %	SiO₂, %	Al₂O₃, %	MgO, %	FeO, %	P, %	V₂O₅, %	TiO₂, %	MnO, %
100	27.8	20.6	11.3	18.1	0.0	0.31	9.95	10.29	1.72
99.9	27.0	20.0	11.0	17.6	2.7	0.30	9.68	10.01	1.67
99.8	26.3	19.5	10.7	17.1	5.3	0.29	9.43	9.75	1.63
99.7	25.6	19.0	10.5	16.7	7.7	0.29	9.19	9.50	1.58
99.6	25.0	18.5	10.2	16.3	10.0	0.28	8.96	9.27	1.54
99.5	24.4	18.1	9.9	15.9	12.2	0.27	8.74	9.04	1.51
99	21.7	16.1	8.9	14.1	21.7	0.24	7.79	8.06	1.34
98	17.9	13.2	7.3	11.6	35.7	0.20	6.40	6.62	1.10
97	15.2	11.2	6.2	9.9	45.4	0.17	5.43	5.62	0.94
96	13.2	9.8	5.4	8.6	52.6	0.15	4.72	4.88	0.81
95	11.6	8.6	4.7	7.6	58.1	0.13	4.17	4.31	0.72

The plots depicted in Figure 4(a)-(b) indicate that the induction furnace melting of a carbon-free and highly metallized DRI (metallization > 99%) derived from KPRS pellets would lead to minimal slag volumes (<60 kg/t-melted-Fe) and limited FeO-content in the slag (< 22%). Additionally, these slag-compositions would be enriched in valuable Ti- and V-oxides. This presents opportunities to develop valuable by-products using the slag generated from the proposed new process.
From Table 1 it is evident that the Fe-bearing melt exhibits exceptionally low impurity concentrations, particularly the phosphorus (P) levels. Consequently, the necessity for extensive melt refining, especially dephosphorization, during steelmaking is significantly reduced. In contrast, conventional processes often require substantial flux additions either during iron ore pellet-making, or separately during primary steelmaking to enable high partitioning of the impurity elements into the slag phase (e.g., lime additions during BOF converter operation for efficient dephosphorization).
In summary of the advantages of the above-described method, it offers a unique opportunity to harness two key advantages intrinsic to a hydrogen-based iron ore reduction process, i.e.:
(1) achieving consistently high DRI metallization (>99%), and (2) generating carbon-free DRI. This approach signifies a transformative leap in efficiency and sustainability of the integrated steelmaking technology
Additionally, the DRI production reactor can operate in diverse modes of gas-solid interactions, including counter-current, co-current, or rotary kiln designs and could be seamlessly integrated with the proposed method for introducing hot DRI to the induction melting. This integration has the potential to optimize the energy value-chain, extending from pelletizing to steel production. Consequently, this alignment is poised to significantly enhance the specific energy efficiency of steel production. The anticipated outcome is a product that is cost competitive w.r.t steel production (with reduced CO₂-emissions), and also aligns with our commitment to environmental sustainability. The pivotal distinction lies in the absence of carbon in the melted DRI, preventing the reduction of gangue oxides during melting and yielding an iron melt with low impurities.

Claims

Method for producing metallic iron melt, comprising:
- in a furnace, providing an iron bearing material having a metallization degree of at least 95%, a carbon content of at most 0.1 wt.%, and a gangue content of 5 wt.% or less,

- heating said iron material in said furnace to a temperature of 1600-1700 °C in a controlled atmosphere, thereby forming a metallic iron melt phase and a slag phase.
The method of claim 1, wherein the provided iron bearing material has a metallization degree of at least 96 %, at least 97 %, at least 98 %, or at least 99 %.
The method of claim 1 or 2, wherein the provided iron bearing material has a carbon content of at most 0.05 wt.%, or at most 0.01 wt.%.
The method of any of claims 1-3, wherein said furnace is heated to a temperature of 1600-1680 °C, or 1620-1650 °C.
The method of any of claims 1-4, wherein the provided iron bearing material has a gangue content of less than 4.5 wt.%, or less than 4 wt.%, or less than 3.5 wt.%, or less than 3 wt.%, or less than 2.5 wt.%, or less than 2 wt.%, or less than 1.5 wt.%, or less than 1 wt.%, or less than 0.5 wt.%.
The method of any of the preceding claims, wherein the controlled atmosphere in the furnace is a reducing atmosphere.
The method of any of the preceding claims, wherein the controlled atmosphere in the furnace has an absolute pressure of 100 Pa to atmospheric pressure.
The method of any of the preceding claims, wherein the controlled atmosphere in the furnace is an inert atmosphere.
The method of any of the preceding claims, comprising no addition of oxygen gas or slag modifiers into the furnace.
The method according to any of the preceding claims, further comprising recovering transition elements from the formed slag phase.
The method according to any of the preceding claims, comprising a step of providing the iron bearing material using a gas mixture comprising 90-100 vol.% hydrogen, 0-10 vol.% nitrogen, and 0-10 vol.% H₂O in a Direct Reduction (DR) process.
The method according to any of claims 1-10, comprising a step of providing the iron bearing material using 100% ammonia gas in a Direct Reduction (DR) process.
The method according to any of claims 1-10, comprising a step of providing the iron bearing material using a mixture of ammonia gas and hydrogen gas in a Direct Reduction (DR) process.
The method according to any of claims 1-13, wherein the iron bearing material is or comprises steel scrap.
The method of according to any of the preceding claims, wherein the furnace is an induction furnace.
The method of according to any of claims 1-14, wherein the furnace is an electrical-resistance furnace.
The method of according to any of the preceding claims further comprises to prepare the formed steel melt for refining in a secondary metallurgy unit.
The method of according to any of the preceding claims, wherein the iron bearing material is provided in said furnace in a cold state.
The method of according to any of the preceding claims, wherein the iron material is provided in said furnace in a hot state.
A metallic iron melt phase comprising at least 99.9 wt.% iron.