Slag treatment process and equipment

Abstract

The invention relates to a process and related equipment for value-added treatment of slag generated by steelmaking of an electric arc furnace. Using the principle of metallothermic reduction, slag is treated with aluminum and / or silicon scrap (e.g., scrap from waste photovoltaic cells), converting iron oxides of steel and any oxides of other alloy metals to iron and iron alloys, respectively, while converting aluminum and silicon to corresponding oxides. In this manner, the metals of steel are recovered from the starting slag and slag which can be preferentially used for, but not limited to, cement production is obtained. The process is carried out passively, does not require additional external energy input, and preferably is carried out simultaneously with steelmaking, so that the black slag can be continuously treated every time the black slag is generated in the steelmaking cycle.

Description

Technical Field

[0001] The present invention relates to a process and equipment for treating slag generated during the steelmaking process, particularly slag generated in electric arc furnace steelmaking, in order to recover metals, ferroalloys, and other materials from the slag that can be reused in the steelmaking process itself or in other product fields. Background Art

[0002] When producing steel by electric arc furnace melting, slag containing a high concentration of iron oxide (Fe x O y ) is generated. The current possibilities for reusing and valorizing this slag are very low, and it is generally collectively referred to as black slag. Therefore, black slag is a by-product generated when melting scrap steel or direct reduced iron to produce new steel. Its composition includes oxides of unwanted elements (such as silicon and phosphorus), or inevitable oxidation products of other alloying metals of iron and steel (such as manganese). In addition, there are added slag formers such as lime (CaO) and magnesia (MgO).

[0003] An electric arc furnace is a furnace that heats materials by an electric arc and operates by combining the chemical energy provided by oxygen and fuel. Using an electric arc furnace can produce steel with up to 100% scrap metal as raw material. Compared with primary steelmaking using iron ore as raw material, this method can reduce the energy consumption required for steelmaking. As mentioned above, an electric arc furnace is a device that can melt different mixtures of furnace charges. In addition to scrap steel, it can also melt direct reduced iron and hot briquetted direct reduced iron (hot briquetted iron).

[0004] The steel industry regards the slag generated during the melting process as a by-product, and part of it can be used for building materials (for example, base materials for road construction). According to the requirements of European unified standards, such materials must meet mechanical strength and stability standards, comply with health, health, and environmental protection requirements, and ensure safe use when in use.

[0005] A rough example of the composition of black slag is as follows: 47.7 wt% CaO, 19.6 wt% Fe x O y , 13.6 wt% SiO2, 5.8 wt% Al2O3, 5.3 wt% MnO, 3 wt% MgO, 0.96 wt% Cr2O3, 0.5 wt% P2O5, and 0.46 wt% TiO2. For every ton of steel produced, about 120 kg of black slag is generated. Therefore, a steel plant with an annual output of 1 million tons will also generate 120,000 tons of black slag per year, which contains about 30,000 tons of iron oxide, equivalent to 21,000 tons of potentially recoverable metallic iron. Thus, although black slag can be used for road construction, this is not sufficient to achieve the reuse of all black slag, and there is a risk of incurring costs for landfilling materials containing valuable components.

[0006] In addition to iron oxide, depending on the composition of the waste and additives, other types of oxides (such as Ba and V oxides) may occasionally be present in the slag. Ba, Cr, and V sometimes cause leaching problems during slag analysis: in fact, any calcium silicate present in the slag is water-soluble, resulting in leaching. However, for end-use, the slag must be inert, that is, it cannot cause the leaching of Ba, Cr, or V to exceed the defined standards.

[0007] Currently, the industrial process of recovering metals from black slag by carbon reduction method (Equation 1) has not been adopted because this method requires a large amount of energy:

[0008] FeO + C → Fe + CO(g) (1)

[0009] This reaction is an endothermic reaction, requiring high capital expenditure and operating expenditure, but the return on investment is not ideal.

[0010] This process is undoubtedly effective in metal recovery, but due to the endothermic nature of the reaction, it is only suitable for treating high-alloy steel waste because the separate recovery of iron is not sufficient to make this process economically sustainable.

[0011] The following documents are related to the treatment of slag in metallurgy or steelmaking processes: US 2008 / 0156144 A1, DE 2 307237 A1, US 2006 / 0196308 A1, US 5 882 375 A, EP 3 375 764 B1, US 6,241,797 B1, and WO2017 / 100808 A1, but these documents still have drawbacks in the management of slag treatment during the steelmaking process. Summary of the Invention

[0012] The present invention aims to overcome the above-mentioned drawbacks and proposes a process and equipment for the value-added treatment of black slag, avoiding treating the slag only as waste or low-value material, but regarding it as a true by-product with high added value. Another object of the present invention is to recover iron and other alloy metals of steel, if possible, from the slag. Another object of the present invention is to propose a slag treatment process and related equipment to convert the slag into an inert slag that is easy to use in the cement industry. Still another object of the present invention is to propose a process and equipment to reduce the slag storage generated between each furnace charge (smelting) in an electric arc furnace. Yet another object of the present invention is to minimize the heat input during the slag treatment process as much as possible.

[0013] Other objects or advantages of the present invention will become apparent from the following disclosure.

[0014] In a first aspect of the present invention, the object is achieved by a process for treating the slag produced by an electric arc furnace steelmaking process, which process for the starting slag, especially black slag, comprises the following steps:

[0015] (i) Mixing the starting slag with aluminum and / or silicon waste, the starting slag containing iron oxide (Fe x O y ) and preferably other oxides of alloying metals of steel, especially chromium oxide (Cr x O y ), especially in liquid form;

[0016] (ii) A thermite reduction reaction occurs between the iron oxide (and preferably other oxides of alloying metals of steel, especially chromium oxide (Cr x O y )) and the aluminum and / or silicon waste, thereby producing

[0017] (a) Iron, and preferably other alloying metals of steel, and

[0018] (b) Aluminum oxide (Al2O3) and / or silicon dioxide (SiO2), which are mixed with the other oxides originally present in the slag;

[0019] (iii) Separating (α) iron, and preferably other alloying metals of steel, and (β) the treated slag, the treated slag having a reduced iron oxide content and preferably a reduced content of alloying metal oxides of steel present in the slag, the slag containing the aluminum oxide (Al2O3) and / or silicon dioxide (SiO2) formed in step (ii);

[0020] wherein the reaction in step (ii) is carried out in the still liquid slag directly produced by the electric arc furnace, and the reaction relies on the exothermicity of the reaction itself and the heat provided by the still liquid slag.

[0021] By the above process, the chemical composition of the slag, especially the black slag produced by electric arc furnace steelmaking, can be changed.

[0022] The exothermicity of the above thermite reduction reaction and the heat of the liquid slag ensure the progress of the high-temperature reaction, so that no external heat not generated by the process itself needs to be provided additionally. Therefore, this is a passive slag treatment process; different from the active process, the latter actually requires additional active input of heat from the outside. The slag treated by this process is similar to blast furnace slag and cement clinker and is a high-quality material for producing cement.

[0023] Advantageously, the process according to the present invention is carried out in an on-line manner, that is, synchronously with the steelmaking, in the following specific mode:

[0024] Before step (i), steelmaking is carried out in an electric arc furnace while producing slag. At the end stage of the steelmaking process, the slag is discharged from the furnace while it is still in a liquid state. At the same time as the end of the steelmaking cycle and during the period between tapping in the previous steelmaking cycle and the new steelmaking cycle, the slag is directly processed according to steps (i) to (iii), and

[0025] where steps (i), (ii), and (iii) are repeated while a new round of steelmaking is carried out and new slag is produced.

[0026] The iron obtained by slag treatment, and other alloying metals of preferably steel, can be added to a new round or subsequent steelmaking cycles, or used for other purposes.

[0027] Therefore, steps (i), (ii), and (iii) of slag treatment preferably start and end between the start of one slag tapping and the next slag tapping, and are carried out simultaneously with the smelting process occurring in the electric arc furnace. To achieve this operation management, the overall duration of steps (i), (ii), and (iii) is preferably 30 minutes to 90 minutes.

[0028] In a preferred embodiment of the present invention, step (i) is directly carried out after slag tapping by directly adding aluminum and / or silicon to the slag flow flowing out from the slag tapping gate forming part of the electric arc furnace, particularly preferably starting within 2 minutes after slag tapping, and / or simultaneously with slag tapping. In this way, the latent heat of the slag is fully utilized to cause a chemical reaction between it and aluminum and / or silicon without additional heat input.

[0029] In an embodiment of the present invention, step (ii) is carried out in a reactor without any energy input device, that is, without any additional heating device, such as no heating tube in the reactor wall or no inserted electrode in the reactor. Step (i) is also preferably carried out without preheating the mixed components.

[0030] Therefore, the slag treatment process according to the present invention preferably adopts a "tapping - tapping" continuous treatment mode. This means that each time the electric arc furnace finishes slag tapping and tapping, the currently produced slag (i.e., the aforementioned black slag) will be treated separately, avoiding its accumulation and cooling and / or mixing with the slag from previous furnace batches or other plants (e.g., the white slag produced by a ladle furnace).

[0031] In fact, in a preferred embodiment of the present invention, the starting slag in step (i) is not mixed with the slag produced by other processes and / or additional alumina or silica. This not only enables rapid treatment of the high - temperature slag but also eliminates the need for additional material feeding devices. The slag obtained after treatment can be directly used in the cement industry or road construction.

[0032] Steps (i), (ii) and (iii) are advantageously carried out in air rather than in a controlled inert atmosphere, thus simplifying the equipment.

[0033] Conversely, in the prior art, electric arc furnace steel manufacturers tend to accumulate the slag generated from multiple furnace charges for treatment, thus using a dedicated active furnace for slag treatment to optimize costs, resulting in increased capital expenditure and operating expenditure. On the other hand, the present invention adopts an "online" mode process, and the heat required for the reaction already exists in the slag, thus eliminating the need for "additional" energy input. In addition, the use of a passive reactor enables the slag to be treated synchronously during the production process, eliminating the need to set up a dedicated waste slag storage area for further treatment in an active furnace, which is redundant in the process and equipment according to the present invention, while avoiding various environmental problems associated with storage.

[0034] Table 1 below lists examples of the components of electric arc furnace slag (not directly usable for cement production) and cement clinker. Advantageously, the components of the slag are close to those of the clinker to make it suitable for the application requirements of the cement industry:

[0035] Table 1

[0036] Thermite processes, such as the aluminothermic process or the silicothermic process, can reduce iron oxide to metallic iron while producing stable oxides (SiO2, Al2O3):

[0037] 3FeO + 2Al → 3Fe + Al2O3 + energy (2)

[0038] 2FeO + Si → 2Fe + SiO2 + energy (3)

[0039] The metals and related oxides suitable for applying the thermite process can be determined by the Ellingham diagram. The Ellingham diagram is a Cartesian coordinate system diagram that represents the relationship between the free energy of the reaction of forming a metal oxide from the elements constituting the metal oxide and the temperature...

[0040] The thermite process is a metallurgical process that uses aluminum or other metals with a high chemical affinity for oxygen (such as silicon) to reduce metal oxides, and the heat generated by the reaction will melt the reduced metal. Subsequently, the energy generated can be further recovered / utilized (for example, for steam production).

[0041] Through this process, while recovering the iron component in the slag and other alloy metals of steel to produce high-value alloys, high-value slag is produced, the whole process is energy self-sustaining, and the energy of the exothermic reduction reaction can be recovered.

[0042] This process reduces the content of iron oxide and alloy metals of steel in the slag, while producing alumina and / or silica with components comparable to those of cement clinker.

[0043] The metallothermic reduction process can be carried out in a special container (i.e., a metallothermic reduction furnace), where the liquid slag can be fed together with the reducing agent, but it is preferably carried out in a reactor without a heating device. In the case of using liquid slag as the starting material, the exothermic reduction reaction can be triggered without an external energy source, while in the case of feeding solid slag, additional energy is required. However, if it is necessary to carry out the reaction in a metallothermic reduction furnace, for example, when a large amount of carbon is added, the metallothermic reduction furnace can be heated using resistors, electric arcs, plasma torches, etc.

[0044] In a preferred embodiment, in step (i), a carbon supply is also provided, and in step (ii), the added carbon reacts with iron oxide and preferably also with other oxides of the alloy metals of steel to form carbon monoxide and iron, and preferably the alloy metals of steel. Part of it dissolves in the liquid iron. Adding carbon causes an endothermic reaction (1) to adjust the system temperature. The residual carbon dissolves in the liquid iron for steelmaking. In an alternative embodiment, the residual carbon dissolves in the liquid iron to produce pig iron. The energy balance of the above reactions (2) and (3) depends on the consumption of Al and / or Si (exothermic reaction with metal oxides such as FeO) and the consumption of carbon (endothermic reaction with metal oxides such as FeO). Adding carbon can also be used to adjust the liquidus temperature of the liquid metal. The liquidus is a geometric point in the phase diagram, which indicates that the liquid phase exists above this temperature, while below this temperature, the solidification process begins, and at this time, the melt coexists with the crystal.

[0045] Advantageously, in the total amount of the additive composed of aluminum and / or silicon waste and carbon, the weight percentage of aluminum and / or silicon waste is 50.0 - 99.9 wt%. It should be understood that carbon is not an essential component, but can be adjusted as needed. The additional amount of carbon added is determined by those skilled in the art through their common knowledge.

[0046] The advantages of the process according to the present invention are particularly obvious when producing high-alloy ferroalloys. When the starting slag contains alloy metal oxides of steel, such as chromium oxide, and in step (ii), the alloy metal oxides are also reduced by aluminum and / or silicon to produce the corresponding alloy metals of steel, which together with iron form the corresponding ferroalloys.

[0047] According to the process of the present invention, photovoltaic cell waste can also be recycled by using the silicon contained in the photovoltaic cell waste to participate in the metallothermic reduction reaction. Therefore, in a preferred embodiment of the present invention, the silicon waste can come from discarded photovoltaic cells.

[0048] Preferably, in step (i), the mixture formed by mixing the starting slag, aluminum and / or silicon waste, and optionally carbon contains:

[0049] (I) The base mixture consists of the following components:

[0050] (α) 90 - 96 wt% of slag, preferably containing 15 - 40 wt% of Fe x O y ; 10 - 20 wt% of SiO2; 3 - 9 wt% of Al2O3; 35 - 55 wt% of CaO; and 2 - 10 wt% of MgO and other metal oxides, the concentration of which depends on the composition of the steel in the refining;

[0051] (β) 4 - 10 wt% of aluminum and / or silicon waste;

[0052] And optionally further contains:

[0053] (II) Carbon, the amount of which is such that in the total amount consisting of aluminum and / or silicon waste and carbon, the weight percentage of aluminum and / or silicon waste is 50.0 - 99.9 wt%.

[0054] Advantageously, the slag formed in step (ii) by the metallothermic reduction process and having a reduced iron oxide content, and preferably a reduced content of alloy metal oxides of steel, contains, by weight percentage:

[0055] 43 - 57 wt% of CaO;

[0056] 10 - 20 wt% of SiO2;

[0057] 17 - 27 wt% of Al2O3;

[0058] 1 - 4 wt% of MgO;

[0059] In the case of treating low - alloy steel slag, the iron oxide and the content of alloy metal oxides of steel are less than 5 wt%, or in the case of treating high - alloy steel slag, the iron oxide and the content of alloy metal oxides of steel are more than 5 wt%.

[0060] Furthermore, advantageously, the iron (or steel) forming the alloy and preferably the alloy metals of steel produced in step (ii) contain:

[0061] 88 - 94 wt% of Fe;

[0062] 4 - 6 wt% of Si;

[0063] 0 - 3.5 wt% of C; and

[0064] 2 - 4 wt% of other metals such as Mn, V, Cr.

[0065] In one embodiment of the present invention, the iron is cast iron produced in step (ii), which contains 88-94 wt% of Fe, 4-6 wt% of Si, carbon with a content greater than 2 wt% and less than or equal to 3.5 wt%, and 2-4 wt% of other metals such as Mn, V, and Cr.

[0066] In a particularly preferred embodiment of the present invention, the slag is used for cement production.

[0067] The second aspect of the present invention relates to a slag treatment device, comprising:

[0068] (a) An electric arc furnace for steelmaking and generating black slag, which has at least one slag discharge door;

[0069] (b) A metal thermal reduction reactor without a heating device, which is adapted to receive the slag and is used for separately extracting liquid metal and the resulting slag;

[0070] (c) A first conveying device for conveying the slag to the metal thermal reduction reactor without a heating device, wherein the first conveying device is preferably the slag discharge door forming part of the electric arc furnace;

[0071] (d) A second conveying device arranged upstream of the metal thermal reduction reactor without a heating device for conveying and introducing aluminum and / or silicon waste materials and optionally carbon into the metal thermal reduction reactor without a heating device;

[0072] (e) A slag component analysis system associated with a control system, and the control system is used to add corresponding necessary amounts of aluminum and / or silicon waste materials and optionally carbon to the metal thermal reduction reactor without a heating device through the second conveying device; and

[0073] (f) A device for collecting the flue gas generated by the partial reduction of oxides and carbon contained in the slag and any splashes or metals sublimated from the metal thermal reduction reactor without a heating device.

[0074] Advantageously, the aluminum and / or silicon waste materials added in step (i) are crushed. Therefore, the device according to the present invention preferably includes a crushing device located upstream of the tank container.

[0075] It is also possible to consider storing the slag generated by the electric arc furnace and using it later after cooling. In this case, it should be heated again to make it melt, for example, by an energy supply system that does not use fossil fuels, such as resistors, plasma torches, electric arcs, etc. provided in the device.

[0076] The third aspect of the present invention relates to a mixture for recovering iron and preferably other alloy metals of steel from the slag generated by steelmaking in an electric arc furnace. The mixture is applicable to the process according to the present invention and comprises:

[0077] (I) A base mixture, consisting of the following components:

[0078] (α) 90 - 96 wt% of slag, preferably containing 15 - 40 wt% of Fe x O y ; 10 - 20 wt% of SiO2; 3 - 9 wt% of Al2O3; 35 - 55 wt% of CaO; and 2 - 10 wt% of MgO and other metal oxides, the concentrations of which depend on the composition of the steel in the refining process;

[0079] (β) 4 - 10 wt% of aluminum and / or silicon waste; and optionally further contains

[0080] (II) Carbon, in an amount such that in the total amount consisting of aluminum and / or silicon waste and carbon, the weight percentage of aluminum and / or silicon waste is 50.0 - 99.9 wt%.

[0081] The features and advantages described for one aspect of the present invention are equally applicable to other aspects of the present invention, with necessary modifications.

[0082] Since the process according to the present invention is exothermic, it is possible to recover useful metals under low - energy - consumption conditions to produce high - alloy ferroalloys and slag that can be used in cement production, and its industrial applicability is obvious. Thanks to the exothermic nature of the process according to the present invention, the process is also economically feasible for low - alloy ferroalloys.

[0083] Of course, in a preferred embodiment of the process according to the present invention, the energy generated in step (iii) can be used for other purposes within the steel mill equipped with the equipment according to the present invention.

[0084] The process according to the present invention does not produce CO2, unless in the case of using carbon raw materials and with low energy - consumption requirements, the CO2 flow is also low, and the process according to the present invention has minimal impact on the environment.

[0085] Therefore, the present invention achieves the object of proposing a black - slag recovery process that can obtain ferroalloys, namely steel (about 200 kg / t of black slag) and materials for cement production (about 800 kg / t of black slag). This new way of treating slag in combination with the production of ferroalloys, using recycled metals (such as Al, Si) as reagents, does not produce CO2 (except in the case of partial carbon feed), and due to the exothermic nature of the metallothermic reduction reaction, no additional energy supply is required. This is a circular economy that regards slag as a secondary product of steelmaking (regards it as a by - product), and aluminum and / or silicon waste enters the cycle, while producing materials that can be directly applied to multiple market areas.

[0086] Therefore, the advantages of the present invention are the recovery of metals, the production of highly valuable materials for the cement industry, the reaction process without consuming natural gas and low / no electrical energy consumption (but using the energy that may be recovered by the process itself). This process is particularly suitable for low-carbon steel and alloy steel.

[0087] In a preferred embodiment of the present invention, by carrying out the production of steel and black slag and the passive treatment of black slag in parallel in an electric arc furnace, and by substantially continuously repeating these processes, not only the need for external energy input is avoided, but also the storage of the generated black slag before subsequent cumulative treatment in a dedicated active furnace is avoided.

[0088] The objectives and advantages of the present invention will be further highlighted by the description of the following non-limiting examples.

[0089] Variants and other features of the present invention are detailed in the dependent claims. The preferred embodiments of the process, equipment, and mixtures according to the present invention are described by the accompanying drawings, but should not be construed as limiting the present invention. In particular, unless otherwise specified, the number, shape, size, and material of the equipment and each component can be adjusted, and equivalent elements can be applied without departing from the concept of the present invention. Description of the Drawings

[0090] Figure 1 is a schematic block diagram of the process according to the present invention. Detailed Description of the Embodiments

[0091] In Figure 1 it is possible to see the metallothermic reduction furnace or reactor 2, which receives (arrow 10) different starting materials (slag from the electric arc furnace, aluminum and / or silicon waste, and optionally carbon) to produce an optimal mixture for the metallothermic reduction reaction. After the reaction occurs inside the metallothermic reduction furnace 2, the following products 6 can be extracted from its downstream (arrow 12): ferroalloy, treated slag, and possibly low-flow carbon monoxide gas, which is conveyed (arrow 16) to the flue gas collection and treatment equipment 18 for its oxidation to CO2. The treated slag is applied (arrow 14) to the cement industry 8. This scheme also describes a device according to the present invention, where arrows 10, 12, and 14 represent conveying means, and the starting reagent 4 comes from a feeding device that provides aluminum and / or silicon waste, slag (in this case, slag from the electric arc furnace), and optionally carbon. On the other hand, the metallothermic reduction furnace feed analysis system and the aluminum and / or silicon waste crushing system that can be configured in the device are not shown in the figure. As the metallothermic reduction reactor, the same type of container used in the industrial production of ferroalloys by the metallothermic reduction method can be used.

[0092] Table 2 below provides an example of the thermodynamic equilibrium mass balance of the process according to the present invention:

[0093] Table 2

[0094] It can be seen that the efficiency of this process is that the iron oxide contained in the slag is almost completely extracted, that is, reduced to metallic iron, and at the same time, an increase in the alumina content resulting from the thermite reduction reaction with Al can also be observed.

[0095] In this embodiment, the addition amount of carbon in the aluminum scrap was calculated to produce liquid steel with a melting point lower than that of liquid iron.

[0096] Generally speaking, the present invention is applicable to the slag for recovering low-carbon steel or alloy steel from an electric arc furnace, so that through an exothermic process of reducing metal oxides by using aluminum (or silicon) scrap, metals such as Fe, Cr, and Si can be recovered.

[0097] This process according to the present invention has high process flexibility and can be adjusted according to the target products (ferroalloys containing elements such as Si, Cr, and C with high market value and slag for the cement industry).

Claims

1. A process for treating the slag produced in steelmaking by an electric arc furnace, the process being directed to the starting slag and comprising the following steps: (i) Mix the starting slag with aluminum and / or silicon waste, the starting slag containing iron oxide (Fe x O y ) and other oxides of alloying metals of steel, preferably, especially chromium oxide (Cr x O y ), especially in liquid form; (ii) a thermite reduction reaction occurs between the iron oxide (and preferably other oxides of the alloying metals of the steel, in particular chromium oxide (Cr x O y )) and the aluminum and / or silicon waste, thereby producing (a) iron, and other alloying metals, preferably steel, and (b) alumina (Al2O3) and / or silica (SiO2), which are mixed with the other oxides already present in the slag; (iii) separating (α) the iron, and other alloying metals, preferably steel, and (β) the treated slag, the treated slag having a reduced iron oxide content and preferably a reduced content of the alloying metal oxides of steel present in the slag, the slag comprising the alumina (Al2O3) and / or silica (SiO2) formed in step (ii); wherein the reaction of step (ii) is carried out in the still liquid slag directly produced by the electric arc furnace, the reaction relying on the exothermicity of the reaction itself and the heat provided by the still liquid slag.

2. The process according to claim 1, characterized in that: before step (i), it comprises producing slag while making steel by an electric arc furnace, wherein, at the end stage of the steelmaking process, the slag is discharged from the furnace while still being liquid, and directly treating the slag according to steps (i) to (iii) at the same time as the end of the steelmaking cycle and during a new steelmaking cycle after tapping in the previous steelmaking cycle, and wherein steps (i), (ii), and (iii) are repeated while carrying out a new round of steelmaking and producing new slag.

3. The process according to claim 1 or 2, characterized in that, Step (i) is carried out directly after slag discharge by directly adding the aluminum and / or silicon to the slag flow flowing out of the slag discharge gate forming part of the electric arc furnace, particularly preferably starting within 2 minutes after slag discharge and / or simultaneously with slag discharge.

4. The process according to any one of claims 1 to 3, characterized in that, Step (ii) is carried out in a reactor without a heating device, such as a reactor wall without heating tubes or a reactor without inserted electrodes.

5. The process according to any one of the preceding claims, characterized in that, The steps (i), (ii), and (iii) of slag treatment start and end between the start of one slag discharge and the start of the next slag discharge, and are carried out simultaneously with the smelting process occurring in the electric arc furnace, wherein the overall duration of steps (i), (ii), and (iii) is preferably 30 minutes to 90 minutes.

6. The process according to any one of the preceding claims, characterized in that, Steps (i), (ii), and (iii) are carried out in air, rather than in a controlled inert atmosphere.

7. The process according to any one of the preceding claims, characterized in that, The starting slag in step (i) is not mixed with the slag produced by other processes and / or additional alumina or silica.

8. The process according to any one of the preceding claims, characterized in that, In step (i), a carbon supply is also provided, and in step (ii), the added carbon reacts at least in part with the iron oxide and preferably with the other oxides of the alloying metals of steel to form carbon monoxide and iron and preferably the alloying metals of steel.

9. The process according to claim 8, characterized in that, The iron exists in the form of steel.

10. The process according to claim 8, characterized in that, The iron exists in the form of cast iron.

11. The process according to claim 8, 9 or 10, characterized in that, In the total amount of additives consisting of the aluminum and / or silicon waste and carbon, the weight percentage of the aluminum and / or silicon waste is 50.0 - 99.9 wt%.

12. The process according to any one of the preceding claims, characterized in that, The starting slag further contains alloy metal oxides of steel, such as in particular chromium oxide, and in step (ii), the alloy metal oxides are also reduced by aluminum and / or silicon, producing the corresponding alloy metals of steel, which together with iron form the corresponding alloys.

13. The process according to any one of the preceding claims, characterized in that, The silicon waste comes from photovoltaic cell waste.

14. The process according to any one of the preceding claims, characterized in that, In step (i), the mixture formed by mixing the starting slag, the aluminum and / or silicon waste, and optionally carbon contains: (I) A base mixture consisting of the following components: (α) 90 - 96 wt% slag, preferably containing 15 - 40 wt% Fe x O y ; 10 - 20 wt% SiO2; 3 - 9 wt% Al2O3; 35 - 55 wt% CaO; and 2 - 10 wt% MgO and other metal oxides, the concentration of which depends on the composition of the steel in the refining process; (β) 4 - 10 wt% of aluminum and / or silicon waste; and optionally further contains (II) Carbon in an amount such that in the total amount consisting of the aluminum and / or silicon waste and carbon, the weight percentage of the aluminum and / or silicon waste is 50.0 - 99.9 wt%.

15. The process according to any one of the preceding claims, characterized in that, The slag formed in step (ii) by the metallothermic reduction process and having a reduced iron oxide content, and preferably a reduced content of alloy metal oxides of steel, contains by weight percentage: 43 - 57 wt% of CaO; 10 - 20 wt% of SiO2; 17 - 27 wt% of Al2O3; 1 - 4 wt% of MgO; In the case of treating low-alloy steel slag, the iron oxide and alloy metal oxide content of steel is less than 5 wt%, or in the case of treating high-alloy steel slag, the iron oxide and alloy metal oxide content of steel is more than 5 wt%, and the iron or steel or cast iron forming the alloy produced in step (ii), and preferably the alloy metals of steel, contain: 88 - 94 wt% of Fe; 4 - 6 wt% of Si; 0 - 3.5 wt% of C; and 2 - 4 wt% of other metals such as Mn, V, Cr.

16. The process according to any one of the preceding claims, characterized in that, The slag is used for cement production.

17. A slag treatment device comprising: (a) An electric arc furnace for steelmaking and producing black slag, which has at least one slag discharge door; (b) A metallothermic reduction reactor without a heating device, which is adapted to receive the slag and is used to separately extract liquid metal and the resulting slag; (c) A first conveying device for conveying the slag to the metallothermic reduction reactor without a heating device, wherein the first conveying device is preferably the slag discharge door; (d) A tank container having a corresponding second conveying device, the second conveying device being arranged upstream of the metallothermic reduction reactor without a heating device for conveying and introducing aluminum and / or silicon waste and optionally carbon into the metallothermic reduction reactor without a heating device; (e) A slag component analysis system associated with a control system, the control system being used to add the corresponding necessary amounts of aluminum and / or silicon waste and optionally carbon to the metallothermic reduction reactor without a heating device through the second conveying device; and (f) A device for collecting the flue gas generated by the partial reduction of the oxides and carbon contained in the slag and any splashes or metals sublimated from the metallothermic reduction reactor without a heating device.

18. A mixture for recovering iron and preferably other alloy metals of steel from the slag generated by electric arc furnace steelmaking, comprising: (I) A base mixture consisting of the following components: (α) 90 - 96 wt% slag, preferably containing 15 - 40 wt% Fe x O y ; 10 - 20 wt% SiO2; 3 - 9 wt% Al2O3; 35 - 55 wt% CaO; and 2 - 10 wt% MgO and other metal oxides, the concentration of which depends on the composition of the steel in the refining process; (β) 4-10 wt% of aluminum and / or silicon waste; and optionally further contains (II) carbon in an amount such that in the total amount composed of the aluminum and / or silicon waste and carbon, the weight percentage of the aluminum and / or silicon waste is 50.0 - 99.9 wt%.

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