Method for operating an electric melter

Abstract

The invention relates to a method for operating an electric melter according to claim 1.

Description

[0001] The invention relates to a method for operating an electric melter in which iron-containing feedstocks are introduced and melted to form molten iron and liquid slag.

[0002] From EP 3 992 309 A1, for example, it is known to melt sponge iron with a high degree of metallization and little gangue as an iron-containing feedstock in an electric melter in order to produce less slag, so that less iron is transferred into the slag in the form of iron oxide and removed with the slag, so that the iron loss can be kept low.

[0003] Furthermore, the Richardson-Ellingham diagram is well known in expert circles, in which the oxygen potentials of metal oxides are plotted as a function of temperature.

[0004] When iron-containing feedstocks are smelted, reduction processes take place at high temperatures. This produces or leaves behind solid components, some of which still need to be reduced, such as oxides FeO and SiO 2 and optionally TiO 2 , but mostly molten and gaseous compounds, such as CO and CO 2 etc. For a reduction reaction to take place, the free reaction enthalpy ΔG red of the reduction must be negative. According to Hess's law, the free reaction enthalpy ΔG red is equal to the difference between the free enthalpies of formation of the compounds, whereby the general rule for the reduction of a metal oxide MeO 2 by a reducing agent R is: Me + O 2 <==> MeO 2 with ΔG MeO2 ; R + O 2 <==> RO 2 with ΔG RO2 ; ΔG red = ΔG RO2 - ΔG MeO2 . This relationship allows us to compare the free enthalpies of formation of compounds and to determine which substances are suitable as reducing agents.Since ΔG red must be negative and the free enthalpy of formation of stable compounds is always negative, ΔG RO2 for the oxidation of the reducing agent must be greater in magnitude than ΔG MeO2 for the oxidation of the metal, so that at equilibrium, the standard free reaction enthalpy ΔG° is determined: ΔG° = ΔH° - T * ΔS°, where H° is the standard reaction enthalpy, T is the temperature, and S° is the standard reaction entropy. Under the "idealized" assumption that ΔH° and ΔS° are independent of temperature, the equation for ΔG° allows a graphical plot versus temperature as a straight line, allowing the free enthalpies of formation of different compounds to be compared. For metal oxides, this can be represented in the so-called Richardson-Ellingham diagram. In the Richardson-Ellingham diagram, ideal conditions are assumed, i.e. that all liquid and solid phases exist as pure phases, so that their activity is one.This simplifies the standard free reaction enthalpy to the so-called oxygen potential: ΔG° = - R * T * In k = - R * T * In [(a MeO 2< ) / (a Me 2< * a O2 )] = R * T * In p O2 , with R as the general gas constant (8.314 J mol -1< K -1< ); T: temperature (K); k: equilibrium constant; a MeO : activity of the metal oxide; a Me : activity of the metal; p O2 : oxygen partial pressure.

[0005] In the Richardson-Ellingham diagram, curves for the more noble metals lie above those for the less noble ones, with the less noble metals correspondingly having a higher oxygen affinity and thus, in principle, being suitable as reducing agents, while they themselves are sometimes difficult to reduce. The Richardson-Ellingham diagram shows that a phase change (from solid to liquid state) has a major influence on the temperature dependence of the oxygen potential (phase changes lead to a change in the slope of the straight line, since entropy increases from solid to liquid to gaseous). It must be noted, however, that the Richardson-Ellingham diagram assumes ideal conditions, so that, for example, an activity of the metal and the oxide different from 1, e.g. due to the formation of mixed phases, leads to a deviation from the described relationships.A further disadvantage is that only statements about the theoretically achievable equilibrium states are possible, while the path and the time to reach the equilibrium, ie the crucial area of ​​reaction kinetics, are ignored, see for example . https: / / application.wiley-vch.de / books / sample / 3527315802c01.pdf , page 37 ff.

[0006] Until now, a statement about the quality of the produced liquid slag and also of the iron melt could only be made through sampling during the respective tapping process, so that the desired qualities could only be reconditioned in subsequent process steps if necessary. Quasi-in-situ monitoring, especially of the quality of the iron melt, has not been considered to date.

[0007] Furthermore, local overheating in the melter and, preferably, simultaneous adjustment of low oxygen partial pressures can lead to the reduction of SiO2 to Si from the liquid slag. Silicon from the liquid slag could then diffuse into the molten iron and enrich it. This would lead to problems during further processing, for example, in a converter, particularly during oxygen blowing, including unwanted ejection and / or excessive slag production and / or heat release during refining, etc.

[0008] The object of the present invention is to further develop this process in such a way that a desired quality of the iron melt can be achieved in the melter.

[0009] This object is achieved by a method having the features of claim 1. Further embodiments are described in the subclaims.

[0010] According to the invention, during the melting operation, oxidic iron substances are added to the iron melt, which results in a redox potential in the iron melt, which enables the oxygen of the oxidic iron substance in the iron melt to be separated and to combine with dissolved silicon in the iron melt to form silicon dioxide and optionally with dissolved titanium in the iron melt to form titanium dioxide.

[0011] During the production of molten iron, components of silicon (compounds) and optionally titanium (compounds) are always present, whereby the content varies depending on the origin of the iron ore primarily used for pig iron / crude steel production. Silicon and optionally titanium, but also other components such as aluminum and magnesium, are contained in oxide form in the so-called gangue of the iron ore. During smelting, the gangue leads to the formation of liquid slag and contributes in particular to the composition of the liquid slag that forms on the molten iron during smelting. This applies both to the conventional blast furnace route and to the recently increasing direct reduction-smelter route. Even with direct reduction, which will continue to increase in the future, the gangue can be used in the production of sponge iron, i.e.are not significantly affected or removed during metallization of iron ore to sponge iron by gassing the iron ore with a reducing gas, so that they also remain essentially, in particular essentially unchanged, in the sponge iron.

[0012] Irrespective of this, other iron-containing feedstocks or additives, such as scrap, recycled materials, etc., which can be introduced into the melter, also contain silicon or silicon compounds and optionally titanium or titanium compounds along with iron and impurities.

[0013] Titanium or titanium compounds are present in very low or negligible amounts in most iron ores, for example, below approximately 0.5 wt.%, especially below 0.3 wt.%, preferably below 0.1 wt.%, and most preferably below 0.05 wt.%. In some iron ore deposits, the titanium content can be as high as 4 wt.%. These high contents are undesirable for further processing of the iron melt.

[0014] The iron melt produced from iron-containing feedstocks therefore inevitably contains silicon or dissolved silicon and optionally titanium or dissolved titanium in the iron melt.

[0015] In order to reduce the silicon content in the molten iron, which can be at least 0.010 wt.%, to a maximum of 1.0 wt.%, in particular to a maximum of 0.80 wt.%, preferably to a maximum of 0.60 wt.%, more preferably to a maximum of 0.50 wt.%, more preferably to a maximum of 0.40 wt.%, in order to ensure reliable further processing of the molten iron, for example in a converter, oxidic iron substances are added to the molten iron. The oxygen separates from the oxidic iron substance and combines with the dissolved silicon in the molten iron. The resulting silicon dioxide has a lower density than the surrounding molten iron and rises to the interface with the liquid slag and is thus transferred into the liquid slag.

[0016] For example, in order to reduce and / or maintain the optional titanium content in the molten iron to a minimum, for example to a maximum of 0.5 wt.%, in particular to a maximum of 0.3 wt.%, preferably to a maximum of 0.1 wt.%, more preferably to a maximum of 0.05 wt.%, the addition of oxidic iron substances to the molten iron is helpful. The titanium content in the molten iron can be 0, or it can be permitted, for example with a content of at least 0.0005 wt.%. As already described, the oxygen separates from the oxidic iron substance and combines with the dissolved silicon as well as the dissolved titanium in the molten iron. The additional titanium dioxide resulting from this also has a lower density than the surrounding molten iron and rises to the interface with the molten slag, where it is thus also transferred into the molten slag.

[0017] Oxidic iron substances can be all conceivable iron carriers that contain or consist of oxygen compounds, such as preferably iron ore carriers, preferably iron-containing agglomerates or, for example, oxidic recycled materials or metallurgical materials arising in a metallurgical complex, in particular residues / dust from a coking plant, sintering plant and / or burden preparation. The advantage of an oxidic iron substance added to the molten iron is that it reduces to iron, thus substituting the silicon in the molten iron and thus increasing the iron yield in the molten iron. The oxidic iron substance can also already have a certain so-called degree of metallization, for example between 0.1% and a maximum of 70%, in particular a maximum of 65%, 60%, 55%, 50%, preferably a maximum of 45%, 40%, 35%, 30%, preferably a maximum of 25%, 20%, 15%, 10%, so that a sufficient reduction potential can still exist.The determination of the degree of metallization of a substance is familiar to the person skilled in the art, whereby the degree of metallization is defined as the quotient of the mass of elemental iron present Fe elemental and the mass of total iron present Fe total .

[0018] It is therefore important that the oxidic iron substances are introduced into the molten iron, where they can react directly with dissolved silicon and, optionally, with dissolved titanium. Applying them, for example, to the molten iron or liquid slag would not serve the desired purpose.

[0019] A process-reliable, further-processable iron melt essentially requires little silicon, or rather, a low-silicon iron melt. The redox potential, which is set for the desired, essentially complete, reduction of the added oxidic iron substances in the iron melt, can be easily defined as follows using the free enthalpy - R * T In p O2 , which, depending on the temperature, ideally lies between approximately -290 and -620 kJ / mol O2.

[0020] According to one embodiment, the oxidic iron substances are solid, preferably powdery with a grain size between > 0 and a maximum of 5 mm, in particular a maximum of 3 mm, preferably a maximum of 2 mm, and preferably comprise or consist of iron ore carriers which are introduced into the iron melt through a lance or nozzle.

[0021] According to a preferred embodiment, the addition of the powdered oxidic iron substance can be supported by a carrier gas which promotes the transport into the iron melt.

[0022] According to a further preferred embodiment, the carrier gas can comprise or consist of carbon monoxide, carbon dioxide, argon, and / or nitrogen. Carbon monoxide and / or carbon dioxide are preferably used because the carbon in the carrier gas reacts in the molten iron and can thus be used to enrich the molten iron with carbon.

[0023] According to one embodiment, the redox potential can be determined during melting operation by an actual analysis.

[0024] The actual analysis can be determined, in particular, from continuous oxygen activity measurements. It is well known in expert circles to carry out oxygen activity measurements to estimate the current oxygen concentration in iron melts, since different oxygen concentrations are required or must be adjusted in the various metallurgical treatment processes and also during steel production. For example, in a steelworks during the refining of pig iron in the converter, where the oxygen concentration is actively increased in order to reduce the carbon content in the pig iron. Disposable probes from Heraeus, known under the trade name CELOX, are well known for their ability to measure the current oxygen activity a(O2) of the melt across the entire technically possible concentration range, for example during desulfurization, in the furnace, in the ladle, or in the continuous casting tundish.For example, a correlation of the measured oxygen to sulfur and silicon in pig iron, to carbon and aluminum content in steel can be implemented in a firmware of the respective measuring instrument.

[0025] The actual analysis can be determined alternatively or additionally from a continuous thermal radiation measurement. For example, by using pyrometers, especially two-color pyrometers or two-color pyrometers, whose functionality for measuring emissivity of liquids (measurement objects) and the resulting temperature is known. In order to draw conclusions about the temperature and / or thermal radiation of the molten iron located below the radiating liquid slag, a correction factor must be included. This procedure is also familiar to the expert and can be determined, in particular, through trial-and-error tests.

[0026] The actual analysis can be determined alternatively or additionally by a continuous density measurement of the molten iron. For example, this can be done according to Archimedes' principle or using X-rays or gamma radiation. The principle of density measurement is well known.

[0027] The actual analysis can be determined alternatively or additionally by a continuous viscosity measurement of the iron melt. This is based on the fact that the oxides present in an iron melt can be divided into network-forming oxides, network-transforming oxides, and those that can have both properties depending on their composition (more network-forming than network-transforming oxides, or vice versa). A high proportion of network-forming oxides increases the viscosity, while an increasing proportion of network-transforming oxides decreases the viscosity. See, for example, Chapter 3 ff. in "Influence of Basicity and FeO Content on Viscosity of Blast Furnace Type Slags Containing FeO" Lee et al., ISIJ International, Vol. 44 (2004), No. 8, pp. 1283-1290, also applicable to the iron melt.

[0028] The actual analysis can be determined alternatively or additionally by a continuous electrical conductivity measurement of the molten iron. The concentration and mobility of electrons are influenced by the number of available cations and the size of the cations, respectively; see, for example, Chapter 5.4 in "Understanding the Structure and Structural Effects on the Properties of Blast Furnace Slag (BFS)", Sajid et al., ISIJ International, Vol. 59 (2019), No. 7, pp. 1153-1166, which also applies to molten iron.

[0029] For example, the iron-containing feedstocks used (in the smelter) are preferably reduced iron ore carriers in the form of sponge iron pieces and / or sponge iron pellets with a carbon content of between 0 and 4.8 wt.%, in particular > 0 wt.%, and a degree of metallization of at least 70%. The degree of metallization reflects the ratio of the metallic iron content to the total iron content in the sponge iron. It can in particular be at least 75%, preferably at least 80%, more preferably at least 88% and ideally up to 100%, in particular up to 99%. If the iron melt has a defined carbon content which is between 0, in particular > 0, preferably > 1.0, preferably > 2.0, particularly preferably > 3.0 and 4.5 wt.-%, cannot be provided by the iron-containing feedstock alone, carbon-containing additives must be taken into account and added in such quantities that the desired carbon content in the iron melt can be achieved.

[0030] The use of the invention is also conceivable in electric melters which are operated (only) with scrap and / or pig iron / steel as iron-containing feedstocks in combination with oxidic iron materials.

[0031] The preferred use of sponge iron as iron-containing feedstock also brings with it slag-forming components which are naturally present in the iron ore carrier and cannot be expelled in a preceding reduction process (gangue). If the gangue provided via the sponge iron is insufficient, further slag-forming agents can be introduced as additional additives if required in order to produce a liquid slag which can be further processed. Slag-forming agents are preferably added so that a basicity B4 in the liquid slag of between 0.7 and 1.8 is achieved. B4 can in particular be at least 0.8, preferably at least 0.9 and in particular a maximum of 1.7, preferably a maximum of 1.6. The basicity B4 corresponds to the ratio (CaO+MgO) to (SiO 2 +Al 2 O 3 ), whereby the determination of the characteristic quantities in the slag in the solid state is familiar to the person skilled in the art.The slag former comprises at least one or more of the elements from the group (CaO, MgO, SiO 2 , Al 2 O 3 ).

[0032] In principle, any material in gaseous, liquid, and / or solid form containing reducible free carbon that can be introduced into the electric melter is suitable as carbon-containing additives. Solid materials include coke dust, coke slaked coal, coke breeze, or coal particles. Liquid materials include ethanol, methanol, and other (suitable) hydrocarbons. Gaseous materials include carbon-containing gases such as carbon dioxide, methane (natural gas), carbon monoxide, propane, and butane.

[0033] To improve or increase the recycling rate, scrap can be added in addition to the iron-containing feedstocks, preferably to the sponge iron pieces and / or sponge iron pellets. This can be done, for example, in such a way that > ​​0 kg, in particular at least 20 kg, preferably at least 50 kg, preferably at least 80 kg, up to 500 kg, in particular up to 300 kg, preferably up to 200 kg of scrap can be added per ton of molten iron produced.

[0034] To melt the iron-containing feedstocks and optional additives, the electric melter has several electrodes that can be supplied with an electric current and thus provide the energy required to convert the materials into a liquid phase comprising molten iron and liquid slag. Depending on the size / dimensions of the electric melter, three, four, five, six, or more than six electrodes can be used. The energy required for melting is preferably provided at least in part from renewable energy (sun, wind, water, biomass). If the required energy can be provided entirely by renewable energy, and if this is available in the required quantities, the electric melter can be operated in a more climate-neutral manner.

[0035] The electric melter is preferably an OSBF (Open Slag Bath Furnace) furnace. These include submerged electric arc furnaces, especially SAF (Submerged Electric Arc Furnaces), which are melting furnaces with arc resistance heating that form arcs between the electrode and the charge material and / or the liquid phase, or which heat the charge material and / or the liquid phase using the Joule effect. In SAF, the electrodes are immersed in the charge material and / or the liquid phase, especially the liquid slag. Depending on the functional principle / mode of operation, the submerged electric arc furnaces can be designed as alternating current submerged arc furnaces (SAFac) or direct current submerged arc furnaces (SAFdc).Alternatively, melting furnaces with direct arc action, which deviate from the functional principle / operation described above, can also be used, so-called EAFs (Electric Arc Furnaces), which form arcs between the electrode and the liquid phase. This includes the alternating current arc melting furnace (EAFac), the direct current arc melting furnace (EAFdc), and the ladle furnace (LF).

[0036] The advantage of using submerged arc furnaces (SAF) is that they operate in a reducing atmosphere, whereas direct arc furnaces (EAF) operate in an oxidizing atmosphere.

[0037] The invention is explained in more detail using the following embodiments in conjunction with the drawing.

[0038] In Figure 1The invention is explained using the example of an electric melter (10) in a schematic sectional view. The electric melter (10) comprises a vessel (15) into which iron-containing feed materials and optional additives are introduced, in particular in an amount depending on how much molten iron (1) is to be produced. In order to fill the vessel (15) of the electric melter (10) with iron-containing feed materials and optional additives, feeding takes place via one or more feeding points (12), which can be provided centrally or distributed depending on the size. The electric melter (10) can comprise a lid (18) which can close the vessel (15) at the top in order to be able to set a defined or targeted furnace atmosphere in its interior, for example. The lid (18) can be arranged so as to be movable essentially vertically, see double arrow.If a lid (18) is present, the feeding point(s) (12) are openings in the lid (18) with corresponding feed lines. The required iron-containing feed materials and optional additives can be fed in via means not shown. The iron-containing feed materials comprise or consist predominantly of sponge iron. In addition, other iron-containing substances, such as iron-containing scrap, can also be added to improve the recycling rate. Additional additives such as slag formers, for example lime, silicon dioxide, magnesium oxide and / or aluminum oxide, can be mixed in as required and preferably, in particular if the gangue of the preferably used sponge iron is not sufficient to be able to adjust the desired basicity of the liquid slag (2) to be tapped off. This measure is familiar to the person skilled in the art.

[0039] Once the iron-containing feedstocks and optional additives have been introduced, at least one electrode (11), in this exemplary embodiment there are three electrodes (11), the number of electrodes (11) being selected essentially depending on the dimensions of the electric melter (10), is supplied with energy to melt the iron-containing feedstocks and optional additives. The positioning of the electrode(s) (11) can be adjusted vertically in order preferably to prevent an arc from forming between the charge and the electrode(s) (11), with at least one immersion of the electrode tip into the charge or into the liquid slag (2) preferably being provided. The energy required for melting can preferably be provided at least in part from renewable energy (sun, wind, water).

[0040] The process gas generated during melting operation is discharged via at least one opening (14).

[0041] The preferred use of sponge iron as an iron-containing feedstock, depending on its production and whether the iron ore has been reduced to sponge iron using carbon-containing gas, such as CO, or hydrocarbon-containing gas, such as CH4 or natural gas, or hydrogen-containing gas, such as H2, or mixtures thereof in a preferred preceding direct reduction process, exhibits varying or low carbon contents. This circumstance is known to those skilled in the art and can therefore generally add carbon-containing additives via the feed before or during the smelting process.

[0042] The invention provides that during the melting operation, an addition of oxidic iron substances into the iron melt (1) takes place, which results in a redox potential in the iron melt (1), which enables the oxygen of the oxidic iron substance in the iron melt (1) to be separated and to combine with dissolved silicon in the iron melt (1) to form silicon dioxide, and optionally with the dissolved titanium in the iron melt (1) to form titanium dioxide.

[0043] The addition of the oxidic iron substances can be carried out via at least one lance or nozzle (13, 13.1, 13.2, 13.3, 13.4), wherein the mouth of the lance or the nozzle (13, 13.1, 13.2, 13.3, 13.4) is or is positioned in the molten iron (1). The lance (13, 13.1, 13.4) can be arranged so as to be movable, see double arrow, or the lance or nozzle (13.2, 13.3) is permanently integrated in the vessel (15). The oxidic iron substance is preferably solid, preferably powdered, and particularly preferably comprises or consists of iron ore carriers. The addition can be supported by means of a carrier gas, which promotes the transport of the solid oxidic feedstock.

[0044] The carrier gas may comprise or consist of carbon monoxide, carbon dioxide, argon, and / or nitrogen. Carbon monoxide and / or carbon dioxide are preferred because the carbon can be used to enrich the molten iron (1) with carbon.

[0045] Once the end of the melting operation is reached, the liquid slag (2) is tapped through at least one tap hole (16) and the molten iron (1) is tapped through at least one tap hole (17) and the vessel (15) can be refilled with iron-containing feedstocks and optional additives, not shown here.

[0046] Not shown, nozzles for influencing the movement of the molten iron (1) can be arranged in the vessel (15). However, this task can also be performed by the nozzles (13, 13.1, 13.2, 13.3, 13.4), via which the oxidic iron substances are added in conjunction with a carrier gas. The electric melter (10) can be pivotally mounted to enable tilting and thus tapping of liquid slag (2) in one direction and molten iron (1) in the other direction. However, a rigid vessel (15), in particular with a rectangular cross-section, not shown here, is preferably provided. The operation of electric melters (10) is also familiar to those skilled in the art.

[0047] Particularly preferably, a reducing furnace atmosphere prevails inside the melter (10).

[0048] Also not shown is how the molten iron (1) is removed and fed to a further processing step. Preferably, the molten iron (1) is subjected to a treatment to reduce the carbon in the molten iron to a desired level. This is preferably done using oxygen in a so-called oxygen blowing process, particularly preferably in a converter. The tapped liquid slag (2) is also preferably fed to a granulation process to produce slag, particularly for the construction industry.

[0049] Figure 2shows an Ellingham diagram in which an ideal process window is spanned with a temperature between 1200 and 1500 °C, a lower curve (limit) by Si + O 2 -> SiO 2 and an upper curve (limit) by Fe + ½ O 2 -> FeO. The curve for Ti + O 2 -> TiO 2 lies slightly below the curve for Si + O 2 -> SiO 2 , so that in the presence of titanium, these reactions are also covered with the ideal process window. Thus, the corner points of the ideal process window are at 1200 °C with a minimum free enthalpy of approximately - 350 kJ / mol O 2 and a maximum free enthalpy of approximately - 620 kJ / mol O 2 and at 1500 °C with a minimum free enthalpy of approximately - 290 kJ / mol O 2 and a maximum free enthalpy of approximately - 560 kJ / mol O 2 .

[0050] If an actual analysis shows that the melting operation cannot be operated in a desired target operation and thus cannot lead to a low-silicon iron melt (1), it is preferable to add oxidic iron substances, preferably iron ore carriers in powder form with a grain size between > 0 and 5 mm in combination with a carrier gas, preferably a carbon-containing gas, to influence the melting operation via lances or nozzles (13, 13.1, 13.2, 13.3, 13.4), the mouth of which ends in the iron melt (1).

[0051] The adjustment is advantageously carried out in such a way that an oxygen partial pressure of approximately 10 -9< to 10 -16< bar, in particular of approximately 10 -9< to 10 -22< bar, preferably of approximately 10 -10< to 10 -20< bar, more preferably of approximately 10 -11< to 10 -18< bar is achieved, wherein, for example, the CO / CO 2 ratio is selected between 5 and 10 5< , in particular 10 and 10 4< , preferably 10 and 10 3<.

[0052] The redox potential is determined during melting operations by an actual analysis, wherein the actual analysis can be determined from an oxygen activity measurement, a thermal radiation measurement, a density measurement, a viscosity measurement, and / or a measurement of the electrical conductivity, in particular of the iron melt (1). The actual analysis is preferably carried out automatically, preferably continuously or discretely at specific times. Automated oxygen activity measurement is particularly preferred.

[0053] A minimum oxygen activity can be determined in the iron melt at ΔG° SiO2 = - R * T * In k = - R * T * In [(a SiO2 ) / (a Si * a O2 )] and a high oxygen activity at ΔG° FeO = - R * T * In k = - R * T * In [(a 2< FeO ) / (a 2< Fe * a O2 )]. Furthermore, the oxygen activity in the smelter above the liquid slag in the furnace atmosphere can be determined with ΔG° CO2 = - R * T * In k = - R * T * In [(a CO2 ) / (a CO * a 0.5< O2 )].

[0054] Example: On a laboratory scale, 100 kg of sponge iron from a 100% direct reduction process using hydrogen as the reducing gas was used in a SAF. Thus, the total carbon content introduced by the sponge iron was less than 0.30 wt.%. The titanium content was below 0.05 wt.%. Slag formers were added to achieve a basicity B4 of preferably 1.05 in the liquid slag. Carbon was added to molten iron for carburization to achieve a carbon content of approximately 4 wt.% in the molten iron. A first sample of the molten slag and one of the molten iron were taken and analyzed once the liquid phase was completely present. After adding iron ore carrier with a grain size of less than 1 mm and CO as the carrier gas for approximately 1 minute using a lance immersed in the molten iron, a second sample of the molten slag and the molten iron was taken and analyzed.Analysis of the samples showed that the silicon content could be reduced in the iron melt and increased in the liquid slag. The analysis of samples in metallurgy for their composition is well known to those skilled in the art.

Claims

1. A method for operating an electric melter in which iron-containing charge materials are introduced and melted in the melting operation to form molten iron (1) and liquid slag (2), characterized in that During the melting operation, oxidic iron substances are added to the iron melt (1), which results in a redox potential in the iron melt (1), which enables the oxygen of the oxidic iron substance in the iron melt (1) to be separated and to combine with dissolved silicon in the iron melt (1) to form silicon dioxide and optionally with dissolved titanium in the iron melt (1) to form titanium dioxide.

2. Method according to claim 1, wherein the oxidic iron substance is solid, which is introduced into the iron melt (1) through a lance or nozzle (13, 13.1, 13.2, 13.3, 13.4).

3. The method according to claim 2, wherein the oxidic iron substance is in powder form with a grain size between > 0 and a maximum of 5 mm and comprises or consists of iron ore carriers.

4. The method according to claim 3, wherein the addition of the oxidic iron substance is assisted by means of a carrier gas.

5. The method according to claim 4, wherein the carrier gas may comprise or consist of carbon monoxide, carbon dioxide, argon and / or nitrogen.

6. Method according to one of the preceding claims, wherein the reduction potential is determined during the melting operation by an actual analysis.

7. The method according to claim 6, wherein the actual analysis is determined from an oxygen activity measurement.

8. The method according to claim 6, wherein the actual analysis is determined from a thermal radiation measurement.

9. The method according to claim 6, wherein the actual analysis is determined from a density measurement.

10. The method according to claim 6, wherein the actual analysis is determined from a viscosity measurement.

11. The method according to claim 6, wherein the actual analysis is determined from an electrical conductivity measurement.

12. A process according to any one of the preceding claims, wherein reduced iron ore carriers in the form of sponge iron pieces and / or sponge iron pellets with a carbon content of between 0 and 4.5 wt.% and a degree of metallization of at least 70% are used as iron-containing feedstocks.

13. Process according to one of the preceding claims, wherein in addition to the iron-containing feedstocks, additional additives such as slag formers are introduced, which comprise at least one or more of the elements from the group (CaO, MgO, SiO2, Al2O3), so that a basicity B4 in the liquid slag of between 0.7 and 1.8 is established.

14. Method according to one of the preceding claims, wherein the energy required for melting is provided at least in part from renewable energy.

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