Electric furnace

Abstract

The present invention relates to an electric furnace having a double melting furnace, and includes a first upper cell forming a first upper space of a first melting furnace into which a first iron source is charged and melted, a second upper cell forming a second upper space of a second melting furnace into which a second iron source is charged and melted, a lower cell coupled to the lower portions of the first upper cell and the second upper cell, and integrating a first lower space of the first melting furnace and a second lower space of the second melting furnace into one integrated space, and a partition unit vertically installed between the first upper cell and the second upper cell and capable of separating the first lower space of the first melting furnace and the second lower space of the second melting furnace formed by being integrated by the lower cell.

Description

Technical Field

[0001] The present invention relates to an electric furnace, and more particularly, to an electric furnace having a double melting furnace that can effectively separate a large amount of gangue components flowing in from an ore-based iron source without mixing them into the existing slag while melting the main raw materials and performing refining at the same time by simultaneously charging an ore-based iron source (OBM’s: Ore Based Materials) and low-granularity scrap and general scrap.

Background Art

[0002] Generally, the steel material production process in the iron and steel industry can be roughly divided into a "blast furnace-converter" production system (hereinafter generally referred to as a converter) that uses ore as the main raw material, and an "electric furnace" production system that uses scrap that is recovered / reused after being commercialized using the produced steel material as the main raw material.

[0003] The converter system is widely used for the production of high-quality products, mainly sheet materials that are sensitive to surface defects, etc., based on the virginity of molten steel caused by ore. The electric furnace system that uses scrap that can be affected by impurities (such as Cu, Sn, Cr, Mo, Ni, etc., hereinafter generally referred to as tramp elements) added during commercialization or mixed during recovery is generally mainly applied to the production of bars / sections that require high strength. However, when specific conditions are met, sheet materials may be produced using the electric furnace process. As carbon neutrality becomes a global issue, the electric furnace process with a carbon dioxide (CO 2 ) generation amount of ≤20% level has emerged as an alternative for future steel production (production of sheet materials).

[0004] The process obstacles to the production of high-quality sheet materials using such an electric furnace process can be roughly classified into problems caused by the main raw material (scrap) and the characteristics of the melting process.

[0005] The former is a factor causing surface defects in products. In general, for sheet products where surface plating is performed while mechanical processing is applied only in one axial direction, surface defects generated in the continuous casting process due to tramp elements flowing in from scrap tend to deepen through the rolling process and can have the characteristic of inferior workability. Second, due to the characteristics of the process of melting scrap by utilizing an arc (electrical energy), nitrogen (N 2 ) gas in the air around the electrode is ionized (plasma) and injected into the molten steel through the arc flow. Along with the nitrogen accumulated in the scrap itself (nitrogen absorption in the production step), it generally shows a higher [N] ppm level compared to the converter process. This is usually at a level of ≧80 ppm, which is a very high level compared to ≧15 ppm in the converter, indicating the quality of molten steel that does not meet the component specifications of high-grade sheet products at a level of ≦30 ppm.

[0006] To overcome such limitations, the active use of ore-based iron sources (OBM’s: Ore Based Materials) (such as DRI, HBI, PI, GPI, etc.) based on iron ore is considered as an alternative. Typically, different from a blast furnace, DRI / HBI, which processes iron ore into pellets and reacts with reducing gas to directly reduce and produce an iron source, can be mentioned. Currently, there is an increasing trend among electric arc furnace steel companies that apply it to commercial facilities to produce sheet materials. Since it is a raw material caused by ore (with components similar to a blast furnace), when applied to an electric arc furnace, there is an advantage that the virginity of the molten steel (the inflow level of tramp elements) can be adjusted according to the input mixing ratio. When applied in large quantities (high mixing ratio application: ≧30%), since it cannot be input by the general main raw material charging method of Batch charging in an electric arc furnace, although it has a drawback that a separate input facility such as Continuous Roof Charging is required, the higher the mixing ratio of the ore-based iron source (OBM’s), the more the scrap melting process vulnerable to nitrogen inflow is shortened (becoming a Flat Bath), and the effect of reducing the [N] level in the molten steel can be obtained.

[0007] In order to produce high-grade steel such as automotive outer panels through the electric furnace process, it is necessary to apply a DRI / HBI mixing ratio (≧80%) at a level similar to the current hot metal ratio (HMR) of the converter. However, with the current commercial equipment technology, there are limitations (such as an increase in energy consumption and a decrease in productivity) in increasing the mixing ratio. Therefore, it is necessary to develop equipment technology to overcome this.

Summary of the Invention

Problems to be Solved by the Invention

[0008] DRI / HBI is produced through the direct gas reduction method. Different from the process of hot metal produced in the blast furnace from the solid phase (iron ore) to the liquid phase (hot metal), where gangue components (such as SiO 2 , AL 2 O 3 etc.) are separated / removed, it is trapped in the raw materials. Therefore, there is a problem that the entire amount must be removed in the electric furnace. In addition, the level of the inflowing [P] component is very high compared to scrap, and the basicity (C / S) of the slag decreases rapidly due to the gangue components. Therefore, there is a problem that the amount of slag generated may increase geometrically as the amount of slag-making agent input for refining increases.

[0009] Also, due to the characteristics of the direct gas reduction method, the reduction is somewhat less favorable compared to the blast furnace process. Therefore, the content of FeO in the raw materials is generally high (5 - 8%). Thus, there is a problem that reduction (increase in the consumption of energy and reducing agent) must be carried out as much as possible in the electric furnace, which is an oxidation process. This may lead to a rapid deterioration of the operating performance as the mixing ratio increases, such as an increase in the amount of slag-making agent used, an increase in power consumption, a decrease in the molten steel recovery rate, and a decrease in productivity, resulting in the loss of cost competitiveness.

[0010] Thus, when operating a conventional commercial electric furnace with only dedicated input equipment, there is a problem that it is limited to producing general sheet materials (structural materials) at the Max. 30% level of the DRI / HBI mixing ratio.

[0011] The present invention is for solving various problems including the above problems, and aims to provide an electric furnace capable of fluidly controlling the blending ratio of DRI / HBI (including other OBM’s) from 0 to 100% according to the steel type to be produced, and at the same time ensuring the stability of operation and economy corresponding to a high blending ratio. However, such problems are exemplary and do not limit the scope of the present invention thereby.

Means for Solving the Problems

[0012] According to an embodiment of the present invention, an electric furnace is provided. The electric furnace is an electric furnace having a double melting furnace in which at least a part of two melting furnaces are combined so as to be able to melt different iron sources, a first upper cell forming a first upper space of a first melting furnace into which a first iron source is charged and melted; a second upper cell arranged horizontally with respect to the first upper cell and forming a second upper space of a second melting furnace into which a second iron source is charged and melted; a lower cell coupled to the lower parts of the first upper cell and the second upper cell, and making a first lower space of the first melting furnace and a second lower space of the second melting furnace into one integrated space; and a partition unit installed vertically movably between the first upper cell and the second upper cell and separating the first lower space of the first melting furnace and the second lower space of the second melting furnace integrated by the lower cell.

[0013] According to an embodiment of the present invention, the furnace wall of the first upper cell may be formed of a refractory so that the first melting furnace can have a heat-resistant structure.

[0014] According to an embodiment of the present invention, the first upper cell may include a first electrode unit at least a part of which is inserted into the first upper space of the first melting furnace through a small skylight of a first roof part formed above the first upper cell, and melting the first iron source by arc heat; and a plurality of iron source supply units arranged radially with respect to the center of the first electrode unit and supplying the first iron source through the first upper space of the first melting furnace.

[0015] According to an embodiment of the present invention, the first electrode part includes a plurality of alternating current (AC) electrodes arranged radially with reference to the center of the small skylight of the first loop part, and each of the plurality of iron source supply parts can continuously supply the first iron source toward the ignition point of the corresponding individual AC electrode.

[0016] According to an embodiment of the present invention, at least a part of the second upper cell is inserted into the second upper space of the second melting furnace through the small skylight of the second loop part formed above the second upper cell, and a second electrode part for melting the second iron source by arc heat; and a preheating supply part installed on one side of the second electrode part above the second upper cell, temporarily storing a predetermined amount of the second iron source in an internal storage space, preheating the second iron source temporarily stored in the storage space using waste heat generated inside the second melting furnace, and then supplying the second iron source through the second upper space of the second melting furnace.

[0017] According to an embodiment of the present invention, the second electrode part includes an upper direct current (DC) electrode inserted through the small skylight of the second loop part and formed on the second upper space side of the second melting furnace; and a lower DC electrode installed opposite to the upper DC electrode in the vertical direction on the bottom surface of the lower cell and formed on the second lower space side of the second melting furnace.

[0018] According to an embodiment of the present invention, the lower DC electrode can include a first lower electrode formed on the bottom surface of the lower cell such that its central axis is coaxial with the central axis of the upper DC electrode so as to be formed opposite to the upper DC electrode.

[0019] According to an embodiment of the present invention, the lower DC electrode may be formed such that its central axis is inclined at a predetermined angle with respect to the central axis of the upper DC electrode on the bottom surface of the lower cell so as to be formed to face the upper DC electrode in an inclined direction, and further include a second lower electrode formed to be biased toward the preheating supply unit with reference to the upper DC electrode.

[0020] According to an embodiment of the present invention, the second electrode unit may cause energization between the upper DC electrode and the second lower electrode immediately after the preheating supply unit supplies the second iron source, and cause energization between the upper DC electrode and the first lower electrode after the melting of the second iron source is completed.

[0021] According to an embodiment of the present invention, the volume of the first melting furnace including the first upper space of the first upper cell and the first lower space of the lower cell may be formed to be smaller than the volume of the second melting furnace including the second upper space of the second upper cell and the second lower space of the lower cell.

[0022] According to an embodiment of the present invention, the first upper cell and the second upper cell may be connected in the form of a duct so that the first upper space of the first melting furnace and the second upper space of the second melting furnace can communicate with each other, and an exhaust gas duct for supplying waste heat generated in the first melting furnace to the second melting furnace side may be further included.

[0023] According to an embodiment of the present invention, the first melting furnace may include a first slag door formed of a double door including an upper door formed at a boundary portion between the first upper cell and the lower cell so as to selectively remove slag generated in the first melting furnace, facing in the vertical direction and opened upward, and a lower door opened downward.

[0024] According to an embodiment of the present invention, the first melting furnace may open the upper door so as to constantly maintain the height of the slag inside the first melting furnace at a predetermined level during operation, and open the lower door when removing the slag inside the first melting furnace.

[0025] According to an embodiment of the present invention, the second melting furnace may include a second slag door formed of a single door that is formed at a boundary portion between the second upper cell and the lower cell and is open upward or downward so as to selectively remove slag generated in the second melting furnace.

[0026] According to an embodiment of the present invention, it may further include a gas bottom blowing device including a plurality of plugs disposed on the bottom surface of the lower cell to discharge gas so as to control the flow of molten metal between the first melting furnace and the second melting furnace.

[0027] According to an embodiment of the present invention, a tapping hole may be formed at a position facing the first electrode portion installed in the small skylight of the first roof portion formed above the first upper cell on the bottom surface forming the first lower space so that the molten metal inside the double melting furnace can be tapped from the lower cell.

[0028] According to an embodiment of the present invention, the bottom surface of the lower cell forming the first lower space in which the tapping hole is formed may be formed higher than the bottom surface forming the second lower space.

[0029] According to an embodiment of the present invention, it may further include a tilting device capable of double-tilting the double melting furnace in which at least a part of the first melting furnace and the second melting furnace are combined in the horizontal direction, or in the width direction perpendicular to the horizontal direction and the vertical direction.

[0030] According to an embodiment of the present invention, the tilting device includes: a support cylinder that supports the double melting furnace to be tiltable at a portion corresponding to the center of gravity of the double melting furnace below the double melting furnace so as to maintain the center of gravity of the double melting furnace tilted by the tilting device; and a plurality of drive cylinders that are radially arranged at least three around the support cylinder so that the double melting furnace can be supported by at least three points and can be individually lifted and lowered to selectively tilt the double melting furnace in the horizontal direction or the width direction.

[0031] According to an embodiment of the present invention, when tapping the molten metal inside the double melting furnace, the double melting furnace is tilted in the horizontal direction so that the double melting furnace can tilt in the direction of the first melting furnace where the tapping port is formed. When removing the slag inside the first melting furnace or the slag inside the second melting furnace, the double melting furnace can be tilted in the width direction so that the double melting furnace can tilt in the direction of the first slag door of the first melting furnace and the second slag door of the second melting furnace.

[0032] According to an embodiment of the present invention, the preheating supply unit includes: a preheating chamber formed in a cylindrical shape or a polygonal cylindrical shape and extending long in the vertical direction so as to be formed as a finger type shaft furnace; and a chamber door installed below the opened preheating chamber to selectively open the lower side of the preheating chamber.

[0033] According to an embodiment of the present invention, the first iron source input into the first melting furnace may include an ore-based iron source (OBM’s: Ore Based Materials), and the second iron source input into the second melting furnace may include scrap.

Effects of the Invention

[0034] According to an embodiment of the present invention made as described above, based on the parallel charging of ore-based iron sources (OBM’s: Ore Based Materials) and low-grit scrap, and general scrap, the gangue components flowing in large amounts from the ore-based iron sources are effectively separated so as not to be mixed into the existing slag (the main components are SiO 2 and Al 2 O 3 The gangue composed of acts mainly as acidic slag. When the inflow amount is large, it causes a large amount of CaO to be added to refine / remove the P component in the molten steel. The increase in the flux unit and the large amount of slag generated thereby act as the main factors creating uneconomic structures such as a decrease in the molten steel recovery rate, an increase in the energy consumption amount, and an increase in the operation time), and a double melting furnace capable of melting the main raw materials and performing refining at the same time can be realized.

[0035] Thus, the present invention relates to a new concept of an electric furnace melting method that can ensure the same or higher productivity / economy / quality as the conventional "blast furnace-converter" production system while charging a large amount of ore-based iron sources (typically DRI) in order to convert the conventional "blast furnace-converter" production system to an "electric furnace" production system. It is a new form of electric furnace that enables the use of a large amount of ore-based iron sources and can have the effect of realizing carbon neutrality in steel production.

[0036] For example, when applying an electric furnace with the double melting furnace structure of the present invention, by effectively separating and discharging the operational impact of a large amount of gangue flowing in from DRI in the first melting furnace, the optimal refining conditions can be maintained / managed, and since a large amount of DRI can be applied by utilizing the highly efficient first melting furnace dedicated to ore-based iron sources, it is possible to reduce the tramp components. Through the charging / operation method of scrap via the first melting furnace into which ore-based iron sources are continuously charged and the second melting furnace connected to it in a double structure, a complete Flat Bath operation can be achieved, and through Arc Sealing by the exhaust gas duct structure, the effect of blocking nitrogen pickup can be obtained, so it is possible to secure the tapping N level of the converter. In addition, the high energy-intensive structure of the first melting furnace, the preheating of scrap in the second melting furnace using exhaust gas, and the simultaneous operation of the first melting furnace and the second melting furnace can realize an electric furnace capable of reducing the energy consumption to below the general scrap operation level and shortening the operation to the converter level. Of course, the scope of the present invention is not limited by such effects.

Brief Description of the Drawings

[0037]

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Embodiments for Carrying Out the Invention

[0038] Hereinafter, with reference to the accompanying drawings, various preferred embodiments of the present invention will be described in detail.

[0039] The embodiments of the present invention are provided to more fully explain the present invention to those having ordinary knowledge in the technical field. The following embodiments can be deformed into various other forms, and the scope of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to further enrich and complete the present disclosure and to fully convey the idea of the present invention to those skilled in the art. Also, in the drawings, the thickness and size of each layer are exaggerated for the convenience of explanation and clarity.

[0040] Hereinafter, the embodiments of the present invention will be described with reference to the drawings schematically showing the ideal embodiments of the present invention. In the drawings, for example, due to manufacturing technology and / or tolerance, deformations of the illustrated shapes can be expected. Therefore, the embodiments of the idea of the present invention should not be construed as being limited to the specific shapes of the regions illustrated in this specification, and should include, for example, shape changes caused by manufacturing.

[0041] FIG. 1 is a cross-sectional view schematically showing an electric furnace 1000 according to an embodiment of the present invention, FIG. 2 is a cross-sectional view schematically showing a cut surface of the electric furnace 1000 taken along the cut line A-A of FIG. 1, and FIG. 3 is a cross-sectional view schematically showing a cut surface of the electric furnace 1000 taken along the cut line B-B of FIG. 1. FIGS. 4 to 7 are cross-sectional views schematically showing the operation process of the electric furnace 1000 of FIG. 1 step by step, FIGS. 8 and 9 are cross-sectional views schematically showing the tilting process of the electric furnace 1000 of FIG. 1, and FIGS. 10 and 11 are tables showing the results of comparing the operation results using a conventional electric furnace with the predicted operation indexes using the electric furnace 1000 of the present invention.

[0042] First, as shown in FIG. 1, an electric furnace 1000 according to an embodiment of the present invention can be an electric furnace having a double melting furnace F in a form in which at least a part of two melting furnaces 10 and 20 arranged in the horizontal direction (X-axis direction) are combined so as to be able to melt different iron sources.

[0043] For example, the first melting furnace 10 of the double melting furnace F can be charged with a first iron source (1 in FIG. 4) that mainly contains ore-based iron sources (OBM’s: Ore Based Materials) (such as DRI, HBI, PI, GPI, etc.) and can also contain some low-granularity scrap (shredder, granulated iron ore, etc.) and melted. It can be a structure that is continuously melted through the input of energy (a level that can maintain the melting energy of the first iron source 1 and the temperature of the molten metal (3 in FIG. 4) in the furnace at a target level) controlled according to the input speed of the first iron source 1 continuously input through the ceiling.

[0044] Due to the characteristics of the melting described above, the first melting furnace 10 does not require a large space because the first iron source 1 is not stacked in the furnace. Therefore, the furnace internal volume is limited to the minimum size at which the outer wall is not damaged by the arc generated by the electrode (smaller in volume compared to the second melting furnace 20 described later), and a structure that can intensify the input electric energy can induce high-speed melting.

[0045] In addition, the second melting furnace 20 in the double melting furnace F is a dedicated melting furnace into which only scrap is charged as the second iron source (2 in FIG. 4), and its basic structure is at the level of a conventional commercial electric furnace. It can be a parent body with a scrap preheating furnace additionally installed for high-speed / high-efficiency operation.

[0046] The first melting furnace 10 and the second melting furnace 20 that make up such a double melting furnace F have at least a part of their structures joined to form a double furnace structure that shares the lower cell 300 and constitutes one body. High-efficiency auxiliary equipment for controlling the input of chemical energy and in-furnace reactions (such as auxiliary raw materials and gas injectors, the types and positions of which can be freely operated as required according to the concept of process design, so specific descriptions thereof are omitted in the present invention) can be installed and operated.

[0047] Hereinafter, the first upper cell 100, the second upper cell 200, the lower cell 300, and the partition unit 400 that make up the first melting furnace 10 and the second melting furnace 20 of the double melting furnace F described above will be described in more detail.

[0048] As shown in FIG. 1, the first upper cell 100 is composed of refractory materials and can form the first upper space A1-1 of the first melting furnace 10 into which the first iron source 1 is charged and melted.

[0049] More specifically, for the purpose of continuously charging and melting an ore-based iron source (OBM’s) and low-grade scrap that may be partially included as the first iron source 1, due to its characteristics, the first melting furnace 10 maintains a certain position above the molten metal level (Hot Heel~Matal Line) where the arc is generated (in the direction from the center of the furnace volume to the lower cell). As a result, the distance between the furnace wall of the first upper cell 100 and the ignition point is maintained at a constant level, which is the same as that in a conventional commercial scrap melting furnace. Different from the conventional ones, it is not necessary to require a high cooling level in a specific operating interval. Rather, excessive cooling of the furnace wall means energy loss, which does not conform to the concept of the high-energy intensive furnace body of the first melting furnace 10 in the present invention. In a dedicated furnace for continuously charging and melting an ore-based iron source (OBM’s) and low-grade scrap, in terms of the fact that the scratch phenomenon of the furnace wall that may occur in the Scrap Batch Charging method does not occur, for the concept of furnace body heat preservation, it may be effective that the furnace wall of the first upper cell 100 is composed of refractory materials.

[0050] However, the first upper cell 100 can be provided with a minimum amount of water cooling equipment so as to prevent deformation of the refractory material itself that plays a role of confining high heat in the furnace body with respect to the external iron skin. (The outer skin water cooling structure is not shown in FIG. 1)

[0051] As shown in FIG. 1, such a first upper cell 100 includes at least a part inserted into the first upper space A1-1 of the first melting furnace 10 through the small skylight of the first roof part 100a formed on the upper side of the first upper cell 100, and a first electrode part 110 for melting the first iron source 1 by arc heat, and a plurality of iron source supply parts 120 arranged radially with the center of the first electrode part 110 as a reference and supplying the first iron source 1 through the first upper space A1-1 of the first melting furnace 10.

[0052] More specifically, as shown in FIGS. 1 and 2, the first electrode part 110 includes a plurality of alternating current (AC) electrodes 111, 112, 113 arranged radially with reference to the center of the small hearth of the first loop part 100a. The plurality of iron source supply parts 120 are formed in the same number as the plurality of AC electrodes 111, 112, 113, and each individual iron source supply part can continuously supply the first iron source 1 toward the ignition point of the corresponding individual AC electrode.

[0053] For example, the first electrode part 110 composed of a plurality of AC electrodes 111, 112, 113 (a direct current energization system can also be introduced if necessary) is charged into the first melting furnace 10 as the first iron source 1. An ore-based iron source (OBM’s) that is relatively lower in specific gravity than molten steel has the property of being present at the interface between the slag 4a or the molten metal 3 and the slag 4a. Therefore, it may be efficient to form a wide ignition point. Moreover, for the protection of the arc at the initial stage of operation and the prevention of nitrogen pickup by the arc, the formation of the slag 4a is necessary. Subsequently, when a large amount of gangue flows in due to the input of the ore-based iron source (OBM’s) and the amount of the slag 4a increases rapidly, rather, the formation of the slag 4a must be suppressed. In the first melting furnace 10, monitoring of the height of the slag 4a may become important. The measurement for this may also be advantageous for the alternating current energization system.

[0054] Also, the plurality of iron source supply units 120 can be a device that continuously feeds an ore-based iron source (OBM’s) as the first iron source 1 (low-granularity scrap can be fed as needed). Although not shown, it is transferred from the main raw material storage facility to a conveyor and freely falls into a pipe-shaped shooter (position energy → kinetic energy) through an intermediate hopper installed at a sufficient height above the first melting furnace 10 to ensure sufficient kinetic energy, and is continuously fed into the furnace through a plurality of inlets secured to correspond to the plurality of AC electrodes 111, 112, 113 on the ceiling of the furnace. More specifically, the plurality of iron source supply units 120 can maximize the melting efficiency by continuously feeding the first iron source 1 to the locations of the three ignition points formed between the plurality of AC electrodes 111, 112, 113 of the first electrode unit 110.

[0055] As shown in FIG. 1, the second upper cell 200 can form the second upper space A2-1 of the second melting furnace 20 in which scrap is charged and melted as the second iron source 2, and is arranged side by side with the first upper cell 100 in the horizontal direction (X-axis direction). Here, although the second iron source 2 mainly contains scrap, it can also contain some high-granularity ore-based iron sources together.

[0056] More specifically, due to the characteristics of melting metal, the second melting furnace 20 can have a structure similar to that of a commercial electric furnace for melting general scrap. Due to the characteristics of the raw material formulation applied in the present invention, since the input ratio of general scrap is small, the height of the scrap charged / stacked in the furnace is low, so the up / down variation of the ignition point generation position is relatively small compared to a general electric furnace (to the extent that the furnace wall and the ignition point approach each other), but still, the possibility of increasing the local thermal influence degree of the furnace wall cannot be excluded. Moreover, since it is more efficient to reduce the energy loss by reducing the second upper space A2-1 in the furnace as the input ratio decreases, such an influence must also be considered. Therefore, although the second upper cell 200 of the second melting furnace 20 is designed similarly to the water-cooling equipment of a commercial electric furnace, it is somewhat miniaturized and preferably composed of a water-cooling equipment with a double-layer structure that can effectively form a thick slag coating layer on the furnace wall for heat insulation, and is configured with a system that can independently control the cooling capacity of each layer.

[0057] As shown in FIG. 1, such a second upper cell 200 includes a second electrode part 210 at least partially inserted into the second upper space A2-1 of the second melting furnace 20 through the small skylight of the second roof part 200a formed on the upper side of the second upper cell 200 to melt the second iron source 2 by arc heat, and a preheating supply part 220 installed on one side of the second electrode part 210 on the upper side of the second upper cell 200, temporarily storing a predetermined amount of the second iron source 2 in the internal storage space, preheating the second iron source 2 temporarily stored in the storage space using the waste heat generated inside the second melting furnace 20, and then supplying the second iron source 2 through the second upper space A2-1 of the second melting furnace 20.

[0058] For example, as shown in FIG. 1, the second electrode unit 210 is inserted through the small ceiling of the second loop unit 200a and includes an upper direct current (DC) electrode 211 formed on the second upper space A2-1 side of the second melting furnace 20, and a lower DC electrode 212 installed on the bottom surface of a lower cell 300 to be described later so as to face the upper DC electrode 211 in the vertical direction and formed on the second lower space A2-2 side of the second melting furnace 20. The lower DC electrode 212 includes a first lower electrode 212a formed on the bottom surface of the lower cell 300 such that its central axis can be coaxial with the central axis of the upper DC electrode 211 so that it can be formed facing the upper DC electrode 211, and a second lower electrode 212b formed on the bottom surface of the lower cell 300 such that its central axis is inclined at a predetermined angle with respect to the central axis of the upper DC electrode 211 so that it can be formed facing the upper DC electrode 211 in an inclined direction and biased toward the preheating supply unit 220 with respect to the upper DC electrode 211.

[0059] At this time, the second electrode unit 210 can cause energization between the upper DC electrode 211 and the second lower electrode 212b immediately after the preheating supply unit 220 supplies the second iron source 2, and can cause energization between the upper DC electrode 211 and the first lower electrode 212a after the melting of the second iron source 2 is completed.

[0060] More specifically, as described above, the second electrode unit 210 can be a DC electrode unit additionally configured with a second lower electrode 212b biased toward the preheating supply unit 220 with respect to the upper DC electrode 211. The second melting furnace 20, which is a dedicated furnace for melting general scrap, basically has no limitation on the type of power supply system (AC or DC applicable), but due to the position of the preheating supply unit 220, when the second iron source 2 is charged, there is a structural limit point where the second iron source 2 is biased and input to the lower side of the preheating supply unit 220 away from the center of the second electrode unit 210.

[0061] In order to dissolve this efficiently, it is necessary to concentrate the input electrical energy on this part. Therefore, it may be more advantageous to apply a direct current power supply system to the second electrode part 210. For example, since the direct current power supply system has the advantage that the flow of current is formed vertically, i.e., an upper direct current electrode 211 and a lower direct current electrode 212, if the second lower electrode 212b among the lower direct current electrodes 212 is installed biased towards the lower side of the preheating supply part 220, it may be possible to bias the input of energy to this part. Further, after the dissolution of the input second iron source 2 is completed, since it is important to uniformly input energy to the entire lower cell 300 part of the second melting furnace 20, a first lower electrode 212a is also arranged directly below the upper direct current electrode 211, like an existing commercial DC furnace.

[0062] By this, by selectively using or varying the ratio of the two lower electrodes 212a and 212b and controlling the flow of the input of electrical energy to the second melting furnace 20 during the process, an effective melting operation can be induced. Although not shown, in relation to this, auxiliary chemical energy input equipment can also be applied to the furnace wall on the lower side of the preheating supply part 220.

[0063] Further, the preheating supply part 220 may be formed as a finger type shaft furnace, and may be composed of a preheating chamber 221 formed in a cylindrical shape or a polygonal cylindrical shape and extending long in the vertical direction (Z-axis direction), and a chamber door 222 installed below the opened preheating chamber 221 and selectively opening the lower side of the preheating chamber 221 so that the second iron source 2 can be selectively supplied.

[0064] More specifically, the preheating supply part 220 is a facility that preheats the second iron source 2 by utilizing the waste heat generated in the first melting furnace 10 and the second melting furnace 20 (supplying the preheating in the form of exhaust gas) for high-speed melting and energy input reduction, and is formed as a finger type shaft furnace that is relatively advantageous in maintenance and operation, and can be applied to the upper part of the second melting furnace 20.

[0065] The electric furnace 1000 having the double melting furnace F of the present invention is designed to be suitable for the production of high-grade steel that must use a large amount of ore-based iron sources (OBM’s), so that the input ratio of the second iron source 2, which is scrap, can be extremely low compared to general electric furnaces. Accordingly, it is preferable that the preheating supply unit 220 is designed to have a volume capable of accommodating the second iron source 2 required for one melting operation at once.

[0066] Also, in the preheating supply unit 220 described above, as shown in FIG. 1, in order to effectively utilize the waste heat generated in the first melting furnace 10, the first upper space A1-1 of the first melting furnace 10 and the second melting furnace 20 The first upper cell 100 and the second upper cell 200 may be connected in the form of a duct (Duct) so that the second upper space A2-1 can communicate with each other, and the waste heat generated in the first melting furnace 10 is transferred to the second melting furnace 20 side. An exhaust gas duct 500 for supplying may be installed.

[0067] More specifically, the preheating supply unit 220 employed in the second melting furnace 20 of the present invention is a preheating furnace that can preheat the second iron source 2 by utilizing waste heat supplied in the form of exhaust gas that is not used for the production of molten metal among the energy input into the furnace and is released into the atmosphere. However, when the partition unit 400 described later physically separates the first upper space A1-1 of the first melting furnace 10 and the second upper space A2-1 of the second melting furnace 20, there may occur a problem that the waste heat generated in the first melting furnace 10, which accounts for more than half of the main energy supply, cannot be received.

[0068] To solve this problem, by installing an exhaust gas duct 500 that connects the first upper space A1-1 of the first melting furnace 10 and the second upper space A2-1 of the second melting furnace 20, a heat transfer path for the waste heat generated in the first melting furnace 10 can be ensured. At the same time, by positioning the intake port on the second melting furnace 20 side of the exhaust gas supplied from the first melting furnace 10 in the opposite direction of the preheating supply unit 220, after the flow of the fluid passes through the arc generation point of the second melting furnace 20, it is configured to be supplied to the preheating supply unit 220, and a sealing function that blocks the arc generated in the second electrode unit 210 from the atmosphere can also be achieved.

[0069] Therefore, the exhaust gas duct 500 that connects the first upper space A1-1 of the first melting furnace 10 and the second upper space A2-1 of the second melting furnace 20 can recover the waste heat generated in the first melting furnace 10 and at the same time perform two functions of blocking the phenomenon that nitrogen (N 2 ) in the atmosphere is picked up by the arc flow into the molten metal 3.

[0070] As shown in FIG. 1, the lower cell 300 is coupled in a vertical direction (Z-axis direction) perpendicular to the horizontal direction (X-axis direction) with the first upper cell 100 and the second upper cell 200, and the first lower space A1-2 of the first melting furnace 10 and the second lower space A2-2 of the second melting furnace 20 can be made into one integrated space.

[0071] In addition, the lower cell 300 is installed in the small skylight of the first roof portion 100a formed above the first upper cell 100 on the bottom surface forming the first lower space A1-2 so that the molten metal 3 inside the double melting furnace F can be tapped. A tapping port 310 can be formed at a position facing the first electrode unit 110, and the bottom surface forming the first lower space A1-2 in which the tapping port 310 is formed can be formed higher than the bottom surface forming the second lower space A2-2.

[0072] For example, in the double melting furnace F of the present invention, the upper cells 100 and 200 of the first melting furnace 10 and the second melting furnace 20 can be configured in two separate forms, and the lower cell 300 can be integrated in the form of a single furnace body. Such a lower cell 300 has a structure in which the molten metal 3 is mixed without a submerged hill structure that separates the first melting furnace 10 and the second melting furnace 20, and simply forms a profile in which the height of the bottom surface on the first melting furnace 10 side is higher than that of the second melting furnace 20 side for the purpose of tapping and maintenance of the tapping port 310. This can be a structure installed at the lower part of the first melting furnace 10 without a separate protruding part for installing the tapping port 310.

[0073] Such a structure of the lower cell 300 allows for free movement of substances and heat, enables integrated utilization of resources (electric power, chemical energy) separately configured in the first melting furnace 10 and the second melting furnace 20, and at the same time enables the design of a shortened process that simultaneously utilizes the functions of different slags 4a and 4b separated between the first melting furnace 10 and the second melting furnace 20 by the partition unit 400 described later.

[0074] In addition, the tapping port 310 formed in the lower cell 300 is designed with a structure that eliminates an unnecessary cold zone by removing the protruding structure for tapping in a commercial electric furnace as described in the structure of the lower cell 300 above. As a result, when selecting the position of the tapping port 310, for the supply of sand that is charged for sealing after tapping, as shown in FIG. 3, it is positioned directly below the input port of any one of the plurality of AC electrodes 111, 112, 113 of the first electrode unit 110, and the sand input tube can be configured to descend through the input port of the AC electrode to fill the sand.

[0075] Also, as shown in FIGS. 1 and 3, at the bottom surface of the lower cell 300, a gas bottom blowing device 600 including a plurality of plugs 600a, 600b, 600c, 600d, 600e, 600f, 600g for discharging gas can be arranged so as to control the flow of the molten metal 3 between the first melting furnace 10 and the second melting furnace 20.

[0076] For example, in order to effectively implement a shortened process in which the first melting furnace 10 and the second melting furnace 20 are separated by a partition unit 400 described later by the integrated lower cell 300 and simultaneously implement melting and refining characteristics suitable for their respective purposes, the flow of the molten metal 3 (the flow of substances and heat) must be controlled according to the purposes of the detailed processes. The formation of a deflected flow (a flow in which the main flow is concentrated in one direction, the first melting furnace 10 → the second melting furnace 20, or the second melting furnace 20 → the first melting furnace 10), or the formation of a flow that rapidly and uniformly mixes the entire volume of the molten metal 3, etc. can be applicable.

[0077] For this purpose, a gas bottom blowing device 600 for implementing the intended flow control can be installed on the bottom surface of the lower cell 300 that constitutes the lower spaces A1-2 and A2-2 of the first melting furnace 10 and the second melting furnace 20. FIG. 3 shows an embodiment in which the plugs 600a, 600b, 600c, 600d, 600e, 600f, 600g of the gas bottom blowing facility 600 are arranged on the bottom surface of the lower cell 300. The detailed matters of this device (the type, size, number, position, etc. of the plugs) are not necessarily limited to FIG. 3 and can be variously changed according to the purpose. At this time, the type of gas introduced through the gas bottom blowing facility 600 can be an inert gas (Ar, N 2 ) for mere flow control, or a fuel / raw material (O 2 , Ch 4 , CO, etc.) for reaction and heat source supply can be selectively introduced.

[0078] Also, as shown in FIG. 1, a tilting device 700 capable of double-tilting a double melting furnace F in which at least a part of the first melting furnace 10 and the second melting furnace 20 are combined in a form below the lower cell 300 in the horizontal direction (X-axis direction), or in the horizontal direction (X-axis direction) and the width direction (Y-axis direction) perpendicular to the vertical direction (Z-axis direction) can be installed.

[0079] More specifically, the tilting device 700 includes a support cylinder 710 that supports the double melting furnace F in a tiltable manner at a portion corresponding to the center of gravity of the double melting furnace F below the double melting furnace F so as to maintain the center of gravity of the double melting furnace F tilted by the tilting device 700, and at least three are radially arranged around the support cylinder 710 so that the double melting furnace F can be supported at at least three points, and a plurality of drive cylinders 720 capable of individually driving up and down so that the double melting furnace F can be selectively tilted in the horizontal direction (X-axis direction) or the width direction (Y-axis direction).

[0080] For example, the support cylinder 710 of the tilting device 700 is a structure installed at the center of gravity of the double melting furnace F, which supports the double melting furnace F and is tiltable in the horizontal direction (X-axis direction) and the width direction (Y-axis direction), and a structure is inserted into the support surface of the double melting furnace F in connection with this, and it is a cylinder that can only move up and down without separate driving force, and can play a role in holding the position of the double melting furnace F. Such a support cylinder 710 is a device necessary to satisfy the necessity of having to make the tapping and slag discharge directions different in order to embody the characteristics of the structure of the double melting furnace F of the present invention.

[0081] And the plurality of drive cylinders 720 of the tilting device 700 are control devices that actually tilt the double melting furnace F. Its basic structure is similar to that of the support cylinder 710, but it is a hydraulic cylinder that provides driving force and can be fixed to the support surface of the double melting furnace F. Such a plurality of drive cylinders 720 can tilt the double melting furnace F by at least three-point support. However, for the stable tilting of the double melting furnace F, two are provided on the side of the first melting furnace 10 and two on the side of the second melting furnace 20, with a total of four, based on the support cylinder 710 that takes the center of gravity of the double melting furnace F. It can be said that it is preferable to embody the tilting of the double melting furnace F in different directions (horizontal direction (X-axis direction) and width direction (Y-axis direction)).

[0082] As shown in FIG. 1, the partition unit 400 is installed between the first upper cell 100 and the second upper cell 200 of the double melting furnace F so as to be vertically movable (Z-axis direction), and is integrated by the lower cell 300 to form the first lower space A1-2 of the first melting furnace 10 and the second lower space A2-2 of the second melting furnace 20 can be selectively separated.

[0083] For example, the scrap charged and melted as the second iron source 2 in the second melting furnace 20 must form a slag 4b in an oxidizing atmosphere when melting. In the operation in an oxidizing atmosphere to remove P, an impurity in the molten steel, oxygen ions in the slag 4b are combined with P in the molten steel to form P 2 O 5 can be formed. Such P 2 O 5 becomes a part of the components in the slag 4b and can reduce P in the molten steel. On the contrary, the ore-based iron source (OBM’s) charged and melted as the first iron source 1 in the first melting furnace 10 must form a slag 4a in a reducing atmosphere when melting. By removing the oxygen of FeO remaining in the ore-based iron source (OBM’s) and mixing the reduced Fe into the molten steel, it can play a role in increasing the actual yield of the charged ore-based iron source (OBM’s).

[0084] When simultaneously using ore-based iron sources (OBM’s) and scrap, if the formed slag is reducing, the actual yield of Fe increases, but P is picked up into the molten steel and the P content increases. If the slag is oxidizing, it is advantageous for P removal, but the actual yield of Fe decreases. To solve this problem, in the double melting furnace F that combines the first melting furnace 10, which is an electric furnace dedicated to ore-based iron sources (OBM’s), and the second melting furnace 20, which is an electric furnace dedicated to scrap, it is necessary to ensure that the slag 4a from the ore-based iron source (OBM’s) and the slag 4b from the scrap are not mixed with each other but are simultaneously realized. For this reason, a partition unit 400 that can separate the slags 4a, 4b between the double melting furnaces F may be essential.

[0085] Thus, the fundamental purpose of the double melting furnace F of the present invention is that the melting and some refining operations of the main raw materials (OBM’s vs. general Scrap) with different characteristics from each other, such as the first iron source 1 and the second iron source 2, can be simultaneously performed by separating the slag 4a of the first melting furnace 10 and the slag 4b of the second melting furnace 20. Before the integration of the first melting furnace 10 and the second melting furnace 20 for final refining and endpoint control, among the different slags 4a, 4b generated in each furnace 10, 20, a large amount of slag that has lost its function or is not suitable for the final stage is excluded, thereby implementing a process for producing high-speed / high-efficiency / high-quality molten metal 3. This is a part that cannot be implemented when applying the combination of the main raw materials to a conventional general electric furnace.

[0086] For this purpose, the partition unit 400 is configured as a device for controlling the separation / integration of the slags 4a, 4b generated in the detailed process stages. The partition unit 400 is composed of a water-cooled structure and refractory materials and can be adjusted by a driving device that moves up and down between the first melting furnace 10 and the second melting furnace 20. This may be the main device for implementing the double melting furnace F of the present invention.

[0087] As described above, the first melting furnace 10 of the double melting furnace F, in which separation / integration can be selectively adjusted by the partition unit 400, includes a plurality of first slag doors 11 formed along the periphery of the first melting furnace 10 at the boundary between the first upper cell 100 and the lower cell 300 so as to selectively remove the slag 4a generated in the first melting furnace 10. The first slag doors 11 are formed of double doors including an upper door 11a that is formed to face in the vertical direction (Z-axis direction), is open upward, and a lower door 11b that is open downward. The second melting furnace 20 may include a second slag door 21 that is formed at the boundary between the second upper cell 200 and the lower cell 300 and is formed of a single door that is open upward or downward so as to selectively remove the slag 4b generated in the second melting furnace 20.

[0088] More specifically, the first slag door 11 formed by the double doors 11a and 11b of the first melting furnace 10 is a device for controlling the level of a large amount of slag 4a generated by the melting of an ore-based iron source (OBM’s) input as the first iron source 1. The double doors 11a and 11b may have a structure that can be opened upward and downward, respectively.

[0089] The slag 4a generated in the first melting furnace 10 basically has a different composition from the slag 4b of a general scrap operation generated in the second melting furnace 20, and such differences are partially controlled and maintained for the purpose. This is because the gangue components flowing in from the ore-based iron source (OBM’s) are mainly acidic components (SiO 2 , Al 2 O 3 ), resulting in the formation of low basicity slag and the characteristic of containing a large amount of FeO. The inflowing FeO must be reduced and recovered as much as possible by inputting a C-based auxiliary raw material, and the CO gas generated at this time forms the slag 4a. Since a large amount of the generated slag 4a is present, it is advantageous to maintain a low basicity state to avoid impairing operation stability when forming occurs. However, on the other hand, there is a conflicting problem that the arc cannot be stabilized without forming.

[0090] For these reasons, in the first melting furnace 10, in order to suppress forming and protect the arc at the same time, it is necessary to confine a certain amount of slag 4a in the furnace, which is also advantageous for the reduction of FeO. Therefore, during operation, the upper door 11a (water-cooled type) that opens upward is opened to maintain a certain level of slag 4a, and thereafter, when it is necessary to remove the slag 4a, it can be controlled by opening the lower door 11b that opens downward. At this time, in order to smoothly control a large amount of slag 4a, as shown in FIG. 2, the first slag door 11 can be configured by a multi-door formed along the circumference of the first melting furnace 10.

[0091] In addition, the second slag door 21 of the second melting furnace 20 is a device that serves the same role as an existing commercial electric furnace and can be used to discharge the slag 4b in the furnace. In the present invention, the first slag door 11 installed in the first melting furnace 10 has the characteristic of continuously discharging a large amount of generated slag 4a after appropriate measures to maintain an appropriate level, while the second slag door 21 must maintain a sealed state except for special purposes. Therefore, it does not have an upward-opening structure in the form of a simple water-cooled panel, but has the characteristic of a structure form capable of two-way (Y-axis direction, Z-axis direction) driving, so that it can be re-sealed after being opened during operation.

[0092] Hereinafter, the main features of the operation of the molten metal manufacturing process embodied through each detailed facility and device constituting the double melting furnace F of the electric furnace 1000 of the present invention will be described.

[0093] As shown in FIG. 4, at the initial stage of operation, the partition unit 400 descends to the maximum, and in a separated state between the first melting furnace 10 and the second melting furnace 20, the first melting furnace 10 continuously melts the ore-based iron source (OBM’s) input as the first iron source 1 through a plurality of iron source supply units 120. The second melting furnace 20 can preheat the scrap, which is the second iron source 2 inside the preheating supply unit 220 through arcing while maintaining the formation of the slag 4b, and additionally supply the melting energy of the first melting furnace 10.

[0094] Next, as shown in FIG. 5, when the level of the molten metal 3 rises (Level1. → Level2.) due to the melting process in the first melting furnace 10 and the risen level (Level2.) reaches a level where it completely submerges into the molten metal 3 at the time of charging the preheated second iron source 2, the chamber door 222 can be opened to charge the second iron source 2 preheated in the preheating chamber 221.

[0095] In this way, by charging the preheated second iron source 2 according to the level of the molten metal 3, it is possible to ensure the melting efficiency of the second iron source 2 which is scrap, and at the same time, it can have the effect of preventing nitrogen (N) pickup due to arcing.

[0096] At this time, as the partition unit 400 rises in accordance with the risen level of the molten metal 3, the flow channel of the molten metal 3 between the lower spaces A1-2 and A2-2 of the first melting furnace 10 and the second melting furnace 20 can be expanded (activation of mass and heat exchange). And the first electrode part 110 of the first melting furnace 10 and the second electrode part 210 of the second melting furnace 20 can also rise appropriately in accordance with the risen level of the molten metal 3.

[0097] Next, as shown in FIG. 6, in the first melting furnace 10, the upward opening of the upper door 11a of the first slag door 11 for adjusting the level of the slag 4a can occur, and in the second melting furnace 20, the melting of the second iron source 2 charged into the molten metal 3 and the preheating of the new second iron source 2 newly temporarily stored in the preheating supply unit 220 for the next operation can occur. Also at this time, as the partition unit 400 further rises in accordance with the risen level of the molten metal 3, the flow channel of the molten metal 3 between the lower spaces A1-2 and A2-2 of the first melting furnace 10 and the second melting furnace 20 can be further expanded (activation of mass and heat exchange). And the first electrode part 110 of the first melting furnace 10 and the second electrode part 210 of the second melting furnace 20 can also continue to rise in accordance with the risen level of the molten metal 3.

[0098] Next, as shown in FIG. 7, by completely raising and fully opening the partition unit 400, after the upward opening of the upper door 11a of the first slag door 11 to remove the slag 4a (a factor causing a decrease in refining ability) in the first melting furnace 10, it can be mixed with the slag 4b in the second melting furnace 20 for final refining. By such complete opening of the partition unit 400, it is possible to have the effect of maximizing the refining efficiency through the interfacial expansion of the refining reaction.

[0099] Throughout all the steps shown in FIGS. 4 to 7 described above, the first melting furnace 10 and the second melting furnace 20 can maintain a continuous refining reaction in the second melting furnace 20 through substance and heat exchange by the integrated lower cell 300. Finally, as shown in FIG. 7, after the partition unit 400 is completely opened, the maximum refining ability can be ensured. At this time, the first melting furnace 10 can reduce a large amount of FeO flowing in from ore-based iron sources (OBM’s) through the maintenance of the reducing slag 4a until the partition unit 400 is completely opened.

[0100] Also, as shown in FIG. 8, when tapping the molten metal 3 inside the double melting furnace F, by raising the drive cylinder 720 on the side of the second melting furnace 20 of the tilting device 700, the double melting furnace F can be tilted in the horizontal direction (X-axis direction), and the double melting furnace F can be tilted in the direction of the first melting furnace 10 where the tapping port 310 is formed.

[0101] Also, as shown in FIG. 9, during operation, when it is necessary to forcibly remove the slag 4a inside the first melting furnace 10 or the slag 4b inside the second melting furnace 20 with the partition unit 400 separating the first melting furnace 10 and the second melting furnace 20, by raising the drive cylinder 720 inside in the width direction (Y-axis direction) of the tilting device 700, the double melting furnace F can be tilted in the width direction (Y-axis direction) so that the double melting furnace F can be tilted in the direction of the first slag door 11 of the first melting furnace 10 and the second slag door 21 of the second melting furnace 20.

[0102] For the smooth tilting of the double melting furnace F as shown in FIG. 8 or FIG. 9 described above, the preheating supply unit 220 can be formed in a separable form from the double melting furnace F, and by the special tilting device 700 proposed in the present invention, the driving procedure for the descent and tilting of the main body of the double melting furnace F in the target direction can proceed.

[0103] Therefore, according to the electric furnace 1000 according to an embodiment of the present invention, based on the parallel charging of ore-based iron sources (OBM’s: Ore Based Materials) and low-granularity scrap, and general scrap, the gangue components flowing in in large amounts from the ore-based iron sources are effectively separated so as not to be mixed into the existing slag (the gangue mainly composed of SiO 2 and Al 2 O 3 acts mainly as acidic slag, and when the inflow amount is large, it causes a large amount of CaO to be charged to refine / remove the P component in the molten steel. The increase in the slag-making agent unit price and the large amount of slag generated thereby act as the main factors creating uneconomic structures such as a decrease in the molten steel recovery rate, an increase in the energy consumption amount, and an increase in the operation time), and it is possible to embody a double melting furnace that can melt the main raw materials and perform refining at the same time.

[0104] Thus, the present invention relates to a new concept of an electric furnace melting method that can ensure the same or higher productivity / economy / quality as the conventional "blast furnace - converter" production system while charging a large amount of ore-based iron sources (typically DRI) in order to convert the conventional "blast furnace - converter" production system to an "electric furnace" production system. It is a new form of electric furnace that can use a large amount of ore-based iron sources and has the effect of realizing carbon neutrality in steel production.

[0105] For example, when applying an electric furnace with the double melting furnace structure of the present invention, the operation influence of a large amount of gangue flowing in from DRI can be effectively separated and discharged in the first melting furnace, so that the optimal refining conditions can be maintained / managed. Since a large amount of DRI can be applied by utilizing the highly efficient first melting furnace dedicated to ore-based iron sources, it is possible to reduce the tramp components. Through the charging / operation method of scrap via the first melting furnace into which ore-based iron sources are continuously charged and the second melting furnace connected to it in a double structure, a complete Flat Bath operation and, through Arc Sealing by the exhaust gas duct structure, the effect of blocking nitrogen pickup can be obtained, so that it is possible to ensure the tapping N level of the converter. In addition, the high energy-intensive structure of the first melting furnace, the preheating of scrap in the second melting furnace using exhaust gas, and the simultaneous operation of the first melting furnace and the second melting furnace can reduce the energy consumption to below the general scrap operation level and shorten the operation to the converter level.

[0106] For example, as shown in FIGS. 10 and 11, when the implementation effect of the present invention is compared with the expected operation index of the present invention by applying a large amount of DR-class DRI in Table 1 based on the actual operation results of a commercial electric furnace, it is shown in Table 2. At this time, the expected operation results were applied based on the components of DRI in FIG. 10, and simple energy and material accounting were performed for the main indicators that change during operation and reflected.

[0107] As shown in Table 2 of FIG. 11, the power consumption was 617 kWh / ton in the commercial electric furnace, but according to the expected operation index of the present invention, it is expected that 361 kWh / ton will be used, and it can be seen that the power consumption is reduced by nearly half. The operation time took 84 minutes in the commercial electric furnace, but according to the expected operation results of the present invention, it is shown that it takes 39 minutes, and it can be seen that the operation time is also reduced by nearly half. At this time, the levels of Cu and N can be controlled to levels similar to those of the converter at ≤0.03% and ≤30 ppm, and it is expected that all the expected operation indexes of the present invention are at the same or even better levels when compared with the commercial scrap electric furnace.

[0108] Here, the operation results of the commercial electric furnace in FIG. 11 are the average actual performance of the actual operation with 100% scrap in the commercial electric furnace of the reference operation, and the predicted operation index of the embodiment of the present invention corresponds to the case where 80% DRI + 20% scrap is applied.

[0109] The present invention has been described with reference to the embodiments shown in the drawings, but these are merely exemplary, and it will be understood by those having ordinary knowledge in the relevant technical field that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention must be determined by the technical idea of the appended claims.

Claims

1. An electric furnace having a double melting furnace in which at least a part of two melting furnaces are combined so as to be able to melt different iron sources, a first upper cell forming a first upper space of a first melting furnace into which a first iron source is charged and melted, a second upper cell arranged horizontally with respect to the first upper cell and forming a second upper space of a second melting furnace into which a second iron source is charged and melted, a lower cell coupled to the lower portions of the first upper cell and the second upper cell, and integrating the first lower space of the first melting furnace and the second lower space of the second melting furnace into one integrated space, and a partition unit installed vertically movably between the first upper cell and the second upper cell, and separating the first lower space of the first melting furnace and the second lower space of the second melting furnace formed integrally by the lower cell. An electric furnace comprising.

2. The first upper cell, The electric furnace according to claim 1, wherein the furnace wall is formed of a refractory so that the first melting furnace can have a heat-resistant structure.

3. The first upper cell, a first electrode unit at least a part of which is inserted into the first upper space of the first melting furnace through a small skylight of a first roof portion formed above the first upper cell, and melting the first iron source by arc heat; The electric furnace according to claim 1, further comprising a plurality of iron source supply units arranged radially with respect to the center of the first electrode unit and supplying the first iron source through the first upper space of the first melting furnace.

4. The first electrode unit, including a plurality of alternating current (AC) electrodes arranged radially with respect to the center of the small skylight of the first roof portion, The plurality of iron source supply units, The electric furnace according to claim 3, wherein each individual iron source supply unit continuously supplies the first iron source toward the ignition point of the corresponding individual AC electrode.

5. The second upper cell, a second electrode unit at least a part of which is inserted into the second upper space of the second melting furnace through a small skylight of a second roof portion formed above the second upper cell, and melting the second iron source by arc heat; a preheating supply unit installed on one side of the second electrode unit above the second upper cell, temporarily storing a predetermined amount of the second iron source in an internal storage space, and using waste heat generated inside the second melting furnace. After preheating the second iron source temporarily stored in the storage space, the electric furnace according to claim 1, further comprising supplying the second iron source through the second upper space of the second melting furnace.

6. The second electrode part is inserted through the small ceiling of the second loop part, and includes an upper direct current (DC) electrode formed on the upper space side of the second melting furnace, and a lower DC electrode installed on the bottom surface of the lower cell so as to face the upper DC electrode in the vertical direction and formed on the lower space side of the second melting furnace, The lower DC electrode is a first lower electrode formed on the bottom surface of the lower cell so that its central axis can be coaxial with the central axis of the upper DC electrode so as to be formed facing the upper DC electrode, and a second lower electrode formed on the bottom surface of the lower cell so that its central axis is inclined at a predetermined angle with the central axis of the upper DC electrode so as to be formed facing the upper DC electrode in an inclined direction, and formed to be biased toward the preheating supply part with reference to the upper DC electrode. The electric furnace according to claim 5, comprising

7. The second electrode part is energized between the upper DC electrode and the second lower electrode immediately after the preheating supply part supplies the second iron source, and energized between the upper DC electrode and the first lower electrode after the melting of the second iron source is completed. The electric furnace according to claim 6.

8. The volume of the first melting furnace composed of the first upper space of the first upper cell and the first lower space of the lower cell is formed to be smaller than the volume of the second melting furnace composed of the second upper space of the second upper cell and the second lower space of the lower cell. The electric furnace according to claim 1.

9. The first upper cell and the second upper cell are connected in the form of a duct (Duct) so that the first upper space of the first melting furnace and the second upper space of the second melting furnace can communicate with each other, and the waste heat generated in the first melting furnace is discharged to the second melting furnace side. The electric furnace according to claim 1, further comprising an exhaust gas duct for supplying.

10. The first melting furnace is formed at the boundary between the first upper cell and the lower cell so as to selectively remove the slag generated in the first melting furnace, and includes a first slag door formed of a double door including an upper door formed to face in the vertical direction and open upward and a lower door open downward. The electric furnace according to claim 1.

11. The first melting furnace is During operation, the upper door is opened so that the height of the slag inside the first melting furnace can be constantly maintained at a predetermined level, and when removing the slag inside the first melting furnace, the lower door is opened. The electric furnace according to claim 10.

12. The second melting furnace The electric furnace according to claim 1, further comprising a second slag door formed at a boundary portion between the second upper cell and the lower cell, which is a single door that is open upward or downward, so that the slag generated in the second melting furnace can be selectively removed.

13. The electric furnace according to claim 1, further comprising a gas bottom blowing device including a plurality of plugs (Plugs) disposed on the bottom surface of the lower cell to discharge gas so as to control the flow of molten metal between the first melting furnace and the second melting furnace.

14. The lower cell The electric furnace according to claim 1, wherein a tapping hole is formed at a position facing the first electrode portion installed in the small hearth of the first roof portion formed above the first upper cell on the bottom surface forming the first lower space so that the molten metal inside the double melting furnace can be tapped.

15. The lower cell The electric furnace according to claim 14, wherein the bottom surface forming the first lower space where the tapping hole is formed is formed higher than the bottom surface forming the second lower space.

16. The electric furnace according to claim 1, further comprising a tilting device capable of double-tilting the double melting furnace in a form in which at least a part of the first melting furnace and the second melting furnace are combined in the horizontal direction, or in the horizontal direction and the width direction perpendicular to the vertical direction.

17. The tilting device A support cylinder that supports the double melting furnace in a tiltable manner at a portion corresponding to the center of gravity of the double melting furnace below the double melting furnace so as to maintain the center of gravity of the double melting furnace tilted by the tilting device; The electric furnace according to claim 16, further comprising a plurality of drive cylinders that are radially arranged at least three around the support cylinder so that the double melting furnace can be supported by at least three points and can be individually lifted and lowered to selectively tilt the double melting furnace in the horizontal direction or the width direction.

18. The tilting device When tapping the molten metal inside the double melting furnace, the double melting furnace is tilted in the horizontal direction so that it can tilt in the direction of the first melting furnace in which the tapping port is formed. When removing the slag inside the first melting furnace or the slag inside the second melting furnace, the double melting furnace is tilted in the width direction so that it can tilt in the direction of the first slag door of the first melting furnace and the second slag door of the second melting furnace. The electric furnace according to claim 16.

19. The preheating supply unit A preheating chamber formed to extend long in the vertical direction in a cylindrical shape or a polygonal cylindrical shape so that it can be formed as a finger type shaft furnace (Finger type shaft furnace), The electric furnace according to claim 5, further comprising a chamber door installed below the opened preheating chamber and selectively opening the lower side of the preheating chamber.

20. The first iron source charged into the first melting furnace Includes ore-based iron sources (OBM's: Ore Based Materials), The second iron source charged into the second melting furnace The electric furnace according to claim 1, comprising scrap.

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