Electric furnace

Abstract

The present invention relates to an electric furnace having double melting furnaces. The electric furnace may comprise: a first upper cell forming a first upper space of a first melting furnace in whi

Description

Electric furnace

[0001] The present invention relates to an electric furnace, and more particularly, to an electric furnace having a dual melting furnace capable of simultaneously melting and refining main raw materials by simultaneously inputting ore-based iron sources (OBMs: Ore Based Materials) and low-particle scrap, and general scrap, so as to effectively separate the gangue component flowing in large quantities from the ore-based iron sources without mixing it with existing slag.

[0002] In general, the steel material production process of the steel industry can be broadly divided into a “blast furnace-converter” production system (hereinafter collectively referred to as converter) that uses ore as the main raw material, and an “electric furnace” production system that uses scrap, which is recovered / recycled after producing steel materials and turning them into products, as the main raw material.

[0003] The converter furnace system is widely used for the production of high-quality products, mainly plates that are sensitive to surface defects, based on the virginity of molten steel derived from ore. The electric arc furnace system, which uses scrap that can be affected by impurities (Cu, Sn, Cr, Mo, Ni, etc., collectively referred to as Tramp elements) added during product manufacturing or mixed in during recovery, is generally applied mainly to the production of bars and sections that require high strength. However, in cases where certain conditions are met, the electric arc furnace process can be used for plate production, and as carbon neutrality becomes a global issue, the electric arc furnace process, which emits ≤20% of the carbon dioxide (CO2) compared to the converter furnace process, is emerging as an alternative for future steel production (plate production).

[0004] These process obstacles in the production of high-quality plates using the electric furnace process can be broadly divided into problems arising from the main raw material (scrap) and the characteristics of the melting process.

[0005] The former is a factor that causes surface defects in products. Generally, mechanical processing is applied only in one direction, and plate products that perform surface plating tend to have surface defects that occur during the continuous casting process due to tramp elements introduced from the scrap, and these surface defects tend to worsen during the rolling process, and may also have poor workability. Secondly, due to the nature of the process that utilizes an arc (electrical energy) to melt the scrap, nitrogen (N2) gas in the air around the electrode is ionized (plasma) and injected into the molten steel through the arc flow, and the nitrogen accumulated in the scrap itself (absorbed during the production stage) generally shows a higher [N] ppm level than the converter process. This is usually ≥80ppm, which is much higher than the ≥15ppm of the converter, and indicates a molten steel quality that falls short of the high-quality plate component specifications of ≤30ppm.

[0006] To overcome these limitations, the active use of iron ore-based materials (OBMs) (e.g., DRI, HBI, PI, GPI, etc.) is being considered as an alternative. A representative example is DRI / HBI, which, unlike blast furnaces, processes iron ore into pellets and reacts them with reducing gas to directly reduce the iron. Currently, an increasing number of electric arc furnace steelmakers are applying this technology to commercial facilities to produce flat products. Since it is a raw material derived from ore (similar to blast furnace), it has the advantage of being able to control the virginity of the molten steel (level of Tramp element inflow) depending on the mixing ratio input when applying it to an electric furnace. When applied in large quantities (high mixing ratio application: ≥30%), it cannot be input through batch charging, which is the general main raw material charging method of an electric furnace, so a separate charging facility such as continuous roof charging is required, which may be a disadvantage. However, as the mixing ratio of ore-based iron sources (OBM's) increases, the scrap melting process, which is vulnerable to nitrogen inflow, is shortened (Flat Bath), which can have the effect of lowering the [N] level in the molten steel.

[0007] In order to produce high-grade steel such as automobile exterior panels through the electric furnace process, it is necessary to apply a DRI / HBI mixing ratio (≥80%) similar to the hot metal ratio (HMR) of the current electric furnace. However, there are limitations in increasing the mixing ratio (increased energy consumption, decreased productivity, etc.) with the current commercial equipment technology, so it is necessary to develop equipment technology to overcome these limitations.

[0008] Since DRI / HBI is produced through the direct gas reduction method, there was a problem that the gangue components (SiO2, AL2O3, etc.) contained in the ore had to be completely removed in the electric furnace, unlike the molten iron produced in the blast furnace, which goes through the solid (iron ore) to liquid (molten iron) process and is captured in the raw material. In addition, there was a problem that the amount of slag generated could increase exponentially as the amount of slag additive input for refining increased because the slag basicity (C / S) was rapidly lowered due to the gangue components.

[0009] Furthermore, due to the nature of the direct gas reduction method, reduction is somewhat disadvantageous compared to the blast furnace process, so the raw material typically has a high FeO content (5-8%). Therefore, there was a problem that maximum reduction (increased energy and reducing agent consumption) had to be achieved in the electric furnace, which is an oxidation process. This can result in a sharp decline in operating performance (increased energy and reducing agent consumption) as the mixing ratio increases, with increased use of sintering agent, increased electricity consumption, decreased molten steel recovery, and decreased productivity, resulting in a loss of cost competitiveness.

[0010] In this way, when operating a conventional commercial electric furnace using only dedicated input equipment, there was a problem in that it was limited to producing general boards (structural materials) at a DRI / HBI mixing ratio of up to 30%.

[0011] The present invention aims to solve various problems, including the above-mentioned ones, by providing an electric furnace capable of flexibly controlling the DRI / HBI (including other OBMs) mixing ratio from 0 to 100% depending on the steel grade being produced, while simultaneously ensuring operational stability and economic feasibility in response to high mixing ratios. However, these tasks are exemplary and the scope of the present invention is not limited thereby.

[0012] According to one embodiment of the present invention, an electric furnace is provided. The electric furnace may include a dual melting furnace in which at least a portion of two melting furnaces are combined to melt different iron sources, the electric furnace comprising: a first upper cell forming a first upper space of a first melting furnace in which a first iron source is introduced and melted; a second upper cell horizontally disposed with the first upper cell and forming a second upper space of a second melting furnace in which a second iron source is introduced and melted; a lower cell coupled to a lower portion of the first upper cell and the second upper cell to form a first lower space of the first melting furnace and a second lower space of the second melting furnace into a single integrated space; and a partition unit vertically movably installed between the first upper cell and the second upper cell to separate the first lower space of the first melting furnace and the second lower space of the second melting furnace, the first lower space being formed integrated by the lower cell.

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

[0014] According to one embodiment of the present invention, the first upper cell may include a first electrode part that is inserted into the first upper space of the first melting furnace through a small ceiling of a first loop part formed on an upper side of the first upper cell at least partially to melt the first iron source by arc heat; and a plurality of iron source supply parts that are arranged radially based on the center of the first electrode part and supply the first iron source through the first upper space of the first melting furnace.

[0015] According to one embodiment of the present invention, the first electrode section includes a plurality of alternating current (AC) electrodes arranged radially based on the center of the small ceiling of the first loop section, and the plurality of iron source supply sections can continuously supply the first iron source toward the fire point of the individual AC electrode corresponding to each individual iron source supply section.

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

[0017] According to one embodiment of the present invention, the second electrode portion may include an upper direct current (DC) electrode formed on the second upper space side of the second melting furnace by being inserted through the small ceiling of the second loop portion; and a lower DC electrode formed on the second lower space side of the second melting furnace by being installed on the bottom surface of the lower cell so as to be opposite to the upper DC electrode in the vertical direction.

[0018] According to one embodiment of the present invention, the lower DC electrode may include a first lower electrode formed so that its central axis is coaxial with the central axis of the upper DC electrode on the bottom surface of the lower cell so as to face the upper DC electrode head-on.

[0019] According to one embodiment of the present invention, the lower DC electrode may further include a second lower electrode, which is formed so 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 face the upper DC electrode in an inclined direction, and is formed so as to be deflected toward the preheating supply unit with respect to the upper DC electrode.

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

[0021] According to one embodiment of the present invention, the volume of the first melting furnace formed by 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 formed by the second upper space of the second upper cell and the second lower space of the lower cell.

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

[0023] According to one embodiment of the present invention, the first melting furnace may include a first slag door formed at a boundary between the first upper cell and the lower cell, and formed as a double door including an upper door that opens upward and a lower door that opens downward so as to face each other in the vertical direction, so as to selectively discharge slag generated in the first melting furnace.

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

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

[0026] According to one embodiment of the present invention, a gas extraction device including a plurality of plugs arranged on the bottom surface of the lower cell to discharge gas may be further included so as to control the flow of molten metal between the first melting furnace and the second melting furnace.

[0027] According to one embodiment of the present invention, the lower cell may have a discharge port formed at a position opposite to a first electrode part installed in a small ceiling of a first loop part formed on the upper side of the first upper cell on the bottom surface forming the first lower space, so as to discharge molten metal inside the double melting furnace.

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

[0029] According to one embodiment of the present invention, the double melting furnace, which is formed by combining at least a portion of the first melting furnace and the second melting furnace, may further include a tilting device capable of tilting the double melting furnace in the horizontal direction or in a width direction perpendicular to the horizontal direction and the vertical direction.

[0030] According to one embodiment of the present invention, the tilting device may include a support cylinder that tiltably supports the dual melting furnace at a portion corresponding to the center of the dual melting furnace on the lower side of the dual melting furnace so as to maintain the center of the dual melting furnace tilted by the tilting device; and a plurality of drive cylinders that are individually driven to rise and fall, at least three of which are radially arranged around the support cylinder so as to support the dual melting furnace at least three points, so as to selectively tilt the dual melting furnace in the horizontal direction or the width direction.

[0031] According to one embodiment of the present invention, the tilting device tilts the dual melting furnace in the horizontal direction so that the dual melting furnace can tilt in the direction of the first melting furnace in which the tapping port is formed when the molten metal inside the dual melting furnace is tapped, and tilts the dual melting furnace in the width direction so that the dual 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 when the slag inside the first melting furnace or the slag inside the second melting furnace is discharged.

[0032] According to one embodiment of the present invention, the preheating supply unit may include a preheating chamber formed to be elongated in the vertical direction in a cylindrical shape or a polygonal cylinder shape so as to be formed as a finger type shaft furnace; and a chamber door installed at the lower side of the open preheating chamber to selectively open the lower side of the preheating chamber.

[0033] According to one embodiment of the present invention, the first iron source input into the first melting furnace may include ore-based materials (OBMs), and the second iron source input into the second melting furnace may include scrap.

[0034] According to one embodiment of the present invention as described above, it is based on parallel input of ore-based iron sources (OBMs: Ore Based Materials) and low-particle scrap, and general scrap, and effectively separates the gangue component flowing in a large amount from the ore-based iron source so that it is not mixed with the existing slag (the gangue composed mainly of SiO2 and Al2O3 mainly acts as an acidic slag, and when the amount flowing in is large, a large amount of CaO is input to refine / remove the P component in the molten steel, and the increase in the unit cost of the slag and the large amount of slag generated as a result act as major factors creating an uneconomical structure such as a decrease in the molten steel recovery rate, an increase in energy consumption, and an increase in operating time), thereby implementing a dual melting furnace capable of melting the main raw material and performing refining at the same time.

[0035] In this way, the present invention relates to a new concept electric furnace melting method that can secure productivity / economic efficiency / quality equal to or greater than that of the conventional “blast furnace-converter” production system while simultaneously injecting a large amount of ore-based iron (typically DRI) in order to convert the conventional “blast furnace-converter” production system into an “electric furnace” production system, and can have the effect of realizing carbon neutrality in steel production as a new type of electric furnace that can use a large amount of ore-based iron.

[0036] For example, in the case of applying an electric furnace having a dual melting furnace structure of the present invention, the operational impact of a large amount of gangue flowing in from the DRI can be effectively separated and discharged from the first melting furnace, thereby maintaining / managing optimal refining conditions, and a large amount of DRI can be applied using a high-efficiency first melting furnace dedicated to ore-based iron sources, thereby enabling reduction of tramp components, and a method of inputting / operating scrap through the first melting furnace into which ore-based iron sources are continuously charged and the second melting furnace connected thereto in a dual structure can achieve complete flat bath operation, and the effect of blocking nitrogen pickup through arc sealing due to the exhaust gas duct structure can be obtained, thereby making it possible to secure the tapping N level of the converter. In addition, the high-energy intensive structure of the first melting furnace, the scrap preheating of the second melting furnace using exhaust gas, and the simultaneous operation of the first and second melting furnaces can implement an electric furnace that can shorten the operation to the level of a converter furnace and lower the energy consumption level of a general scrap operation. Of course, the scope of the present invention is not limited by these effects.

[0037] FIG. 1 is a cross-sectional view schematically showing an electric furnace according to one embodiment of the present invention.

[0038] Fig. 2 is a cross-sectional view schematically showing a cross-section of an electric furnace taken along the cutting line AA of Fig. 1.

[0039] Fig. 3 is a cross-sectional view schematically showing a cut section of an electric furnace taken along the cutting line BB of Fig. 1.

[0040] Figures 4 to 7 are cross-sectional views schematically showing the operating process of the electric furnace of Figure 1 step by step.

[0041] Figures 8 and 9 are cross-sectional views schematically showing the curing process of the electric furnace of Figure 1.

[0042] Figures 10 and 11 are tables showing the results of comparing the operating performance using a conventional electric furnace and the expected operating index using the electric furnace of the present invention.

[0043] Hereinafter, various preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

[0044] The embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. The following embodiments may be modified in various ways, and the scope of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to more faithfully and completely explain the present disclosure and to fully convey the spirit of the present invention to those skilled in the art. In addition, the thickness and size of each layer in the drawings are exaggerated for convenience and clarity of explanation.

[0045] Hereinafter, embodiments of the present invention will be described with reference to drawings schematically illustrating ideal embodiments of the present invention. In the drawings, variations in the shapes depicted may be expected, for example, depending on manufacturing techniques and / or tolerances. Therefore, embodiments of the present invention should not be construed as limited to the specific shapes of the regions depicted herein, but should include, for example, variations in shapes resulting from manufacturing processes.

[0046] FIG. 1 is a cross-sectional view schematically showing an electric furnace (1000) according to one embodiment of the present invention, FIG. 2 is a cross-sectional view schematically showing a cross-section of the electric furnace (1000) taken along the cutting line AA of FIG. 1, and FIG. 3 is a cross-sectional view schematically showing a cross-section of the electric furnace (1000) taken along the cutting line BB of FIG. 1. In addition, FIGS. 4 to 7 are cross-sectional views schematically showing step-by-step the operation process of the electric furnace (1000) of FIG. 1, 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 performance using a conventional electric furnace with the expected operation index using the electric furnace (1000) of the present invention.

[0047] First, as illustrated in FIG. 1, an electric furnace (1000) according to one embodiment of the present invention may be an electric furnace having a dual melting furnace (F) in which at least a portion of two melting furnaces (10, 20) arranged in a horizontal direction (X-axis direction) are joined together so as to be able to melt different iron sources.

[0048] For example, the first melting furnace (10) among the dual melting furnaces (F) is a melting furnace that can melt by charging the first iron source (1 in FIG. 4) that mainly includes ore-based iron sources (OBM's: Ore Based Materials) (DRI, HBI, PI, GPI, etc.) but may also include some low-grain scrap (Shredder, grain, etc.), and can have a structure that continuously melts through energy input (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.

[0049] The first melting furnace (10) does not require a large space because the first iron source (1) is not stacked inside the furnace due to the melting characteristics described above, and the volume inside the furnace is limited to a minimum size that does not damage the outer wall from the arc generated by the electrode (small with a smaller volume compared to the second melting furnace (20) described later), and can induce high-speed melting with a structure that can concentrate the input electric energy.

[0050] In addition, the second melting furnace (20) among the double melting furnaces (F) is a dedicated melting furnace in which only scrap is fed into the second iron source (2 in Fig. 4). The existing structure is at the level of a conventional commercial electric furnace, and may be a base in which a scrap preheating furnace for high-speed / high-efficiency operation is additionally installed.

[0051] The first melting furnace (10) and the second melting furnace (20) constituting the dual melting furnace (F) are a dual-furnace structure in which at least a portion of the structure is combined to form a single body sharing a lower cell (300), and can be operated by installing high-efficiency auxiliary equipment (such as raw material and gas injectors, the types and locations of which can be freely operated as needed according to the process design concept, and thus a specific description thereof is omitted in the present invention) for controlling chemical energy input and reactions within the furnace.

[0052] Hereinafter, the first upper cell (100), the second upper cell (200), the lower cell (300), and the bulkhead unit (400) constituting the first melting furnace (10) and the second melting furnace (20) of the above-described double melting furnace (F) will be described in more detail.

[0053] As shown in Fig. 1, the first upper cell (100) is made of refractory material and can form a first upper space (A1-1) of the first melting furnace (10) into which the first iron source (1) is introduced and melted.

[0054] More specifically, the first melting furnace (10) is designed to continuously input / melt ore-based iron sources (OBM's) and some low-grained scrap that may be included as the first iron source (1), and, due to its characteristics, the arc generation location is maintained at a certain position above the molten metal level (Hot Heel ~ Matal Line) (from the center of the furnace volume to the lower cell direction), so that the distance between the furnace wall of the first upper cell (100) and the point of fire is maintained at a certain level, and thus, unlike conventional commercial scrap melting furnaces, a high cooling level may not be required in a specific operation section. Rather, excessive furnace wall cooling means energy loss and does not fit with the high-energy intensive furnace concept of the first melting furnace (10) of the present invention, and in a dedicated furnace that continuously feeds / melts ore-based iron sources (OBM's) and low-grain scrap, the furnace wall scratching phenomenon that may occur in the scrap batch charging method does not occur, so for the furnace body heat preservation concept, it may be effective for the first upper cell (100) to be composed of a refractory furnace wall.

[0055] However, the first upper cell (100) may be equipped with a minimum water cooling facility to prevent deformation of the outer steel shell that secures the refractory material itself, which serves to confine high heat to the furnace body. (The outer steel shell water cooling structure is not shown in Fig. 1)

[0056] As shown in FIG. 1, the first upper cell (100) may include a first electrode part (110) that melts the first iron source (1) by arc heat and is inserted into the first upper space (A1-1) of the first melting furnace (10) through the small ceiling of the first loop part (100a) formed on the upper side of the first upper cell (100) at least in part, and a plurality of iron source supply parts (120) that are arranged radially based on the center of the first electrode part (110) and supply the first iron source (1) through the first upper space (A1-1) of the first melting furnace (10).

[0057] More specifically, as illustrated in FIGS. 1 and 2, the first electrode portion (110) includes a plurality of alternating current (AC) electrodes (111, 112, 113) arranged radially based on the center of the small ceiling of the first loop portion (100a), and the plurality of iron source supply portions (120) are formed in the same number as the plurality of AC electrodes (111, 112, 113), so that each individual iron source supply portion can continuously supply the first iron source (1) toward the point of the corresponding individual AC electrode.

[0058] For example, the first electrode unit (110) composed of a plurality of alternating current electrodes (111, 112, 113) (a direct current system can also be introduced as needed) has a characteristic that the ore-based iron source (OBM's) having a relatively lower specific gravity than the molten steel, which is fed as the first iron source (1) to the first melting furnace (10), exists at the interface between the slag (4a) or the molten metal (3) and the slag (4a), so it can be efficient to form a wide ignition point. In addition, slag (4a) forming is necessary for arc protection in the early stage of operation and to prevent nitrogen pickup by the arc, and later, if a large amount of gangue is introduced as the ore-based iron source (OBM's) is fed thereafter and the amount of slag (4a) rapidly increases, the forming of the slag (4a) should be suppressed, and thus, monitoring the height of the slag (4a) can become important in the first melting furnace (10). Measurements for this may also benefit the AC power system.

[0059] In addition, the plurality of iron source supply units (120) may be a device that continuously inputs ore-based iron sources (OBM's) (low-grain scrap can be input as needed) into the first iron source (1). Although not shown, the first iron source (1) may be transferred by a conveyor from the main raw material storage facility, and may be a device that secures sufficient kinetic energy by allowing the iron to fall freely (potential energy → kinetic energy) into a pipe-shaped shooter through an intermediate hopper installed at a sufficient height above the first melting furnace (10) and continuously inputs the first iron source (1) into the furnace through a plurality of input ports respectively corresponding to the plurality of AC electrodes (111, 112, 113) on the furnace ceiling. More specifically, the plurality of iron source supply units (120) may maximize melting efficiency by continuously inputting the first iron source (1) into three points formed between the plurality of AC electrodes (111, 112, 113) of the first electrode unit (110).

[0060] As illustrated in Fig. 1, the second upper cell (200) is arranged parallel to the first upper cell (100) in the horizontal direction (X-axis direction) and can form a second upper space (A2-1) of the second melting furnace (20) into which scrap is fed and melted as a second iron source (2). Here, the second iron source (2) mainly includes scrap, but may also include some high-grain ore-based iron sources.

[0061] More specifically, the second melting furnace (20) may have a structure similar to a commercial electric furnace that melts general scrap due to its characteristics of melting metal. Due to the characteristics of the raw material mixing applied to the present invention, the input ratio of general scrap is small, so the height of the scrap input / stacked in the furnace is low, and thus the up / down variation in the location of the fire point is relatively small compared to a general electric furnace (to the extent that the furnace wall and the fire point become closer), but it cannot be ruled out that the local thermal influence of the furnace wall may still increase. In addition, since it is more efficient to reduce energy loss by making the second upper space (A2-1) in the furnace smaller as the input ratio decreases, this influence may also need to be considered. Accordingly, it may be desirable to configure the second upper cell (200) of the second melting furnace (20) as a system that can separately control the cooling capacity of each layer by configuring a water cooling facility of a double-layer structure that is designed similarly to the water cooling facility of a commercial electric furnace, but is somewhat smaller and can effectively form a thick slag coating layer on the furnace wall for insulation.

[0062] Such a second upper cell (200), as illustrated in FIG. 1, may include a second electrode part (210) that is inserted into the second upper space (A2-1) of the second melting furnace (20) through the small ceiling of the second loop part (200a) formed on the upper side of the second upper cell (200) at least in part to melt the second iron source (2) by the arc heat, and a preheating supply part (220) that is installed on one side of the second electrode part (210) on the upper side of the second upper cell (200) to temporarily store a predetermined amount of the second iron source (2) in the storage space therein, and preheats the second iron source (2) temporarily stored in the storage space using waste heat generated inside the second melting furnace (20), and then supplies the second iron source (2) through the second upper space (A2-1) of the second melting furnace (20).

[0063] For example, as shown in FIG. 1, the second electrode part (210) includes an upper direct current (DC) electrode (211) formed on the second upper space (A2-1) side of the second melting furnace (20) by being inserted through the small ceiling of the second loop part (200a) and a lower DC electrode (212) formed on the second lower space (A2-2) side of the second melting furnace (20) so as to be installed so as to face the upper DC electrode (211) in the vertical direction on the bottom surface of the lower cell (300) to be described later, and the lower DC electrode (212) is formed so as to face the upper DC electrode (211) head-on, and the first lower electrode (212a) and the upper DC electrode (211) are formed so that their central axis can be coaxial with the central axis of the upper DC electrode (211) on the bottom surface of the lower cell (300). In order to be formed, the second lower electrode (212b) may be formed so that its central axis is inclined at a predetermined angle with respect to the central axis of the upper DC electrode (211) on the bottom surface of the lower cell (300), and is formed to be deflected toward the preheating supply unit (220) with respect to the upper DC electrode (211).

[0064] At this time, the second electrode part (210) can cause current conduction between the upper DC electrode (211) and the second lower electrode (212b) immediately after the preheating supply part (220) supplies the second iron source (2), and can cause current conduction between the upper DC electrode (211) and the first lower electrode (212a) after the melting of the second iron source (2) is completed.

[0065] More specifically, as described above, the second electrode unit (210) may be a DC electrode unit additionally configured with a second lower electrode (212b) biased toward the preheating supply unit (220) based on the upper DC electrode (211). The second melting furnace (20), which is a general scrap melting furnace, basically has no restrictions on the type of power supply system (either AC or DC can be applied), but, due to the location of the preheating supply unit (220), when the second iron source (2) is charged, it may have a structural limitation in that the second iron source (2) is biased and fed to the lower side of the preheating supply unit (220) away from the center of the second electrode unit (210).

[0066] In order to melt this efficiently, it is necessary to concentrate the input electric energy to the relevant part, and for this purpose, it may be more advantageous to apply a direct current system to the second electrode part (210). For example, the direct current system has the advantage of forming an up / down current flow between the upper DC electrode (211) and the lower DC electrode (212), and if the second lower electrode (212b) among the lower DC electrodes (212) is installed to be biased below the preheating supply part (220), it may be possible to bias the energy input to the relevant part. In addition, since it is important to uniformly input energy to the entire lower cell (300) of the second melting furnace (20) after the melting of the input second iron source (2) is completed, the first lower electrode (212a) is also placed directly below the upper DC electrode (211) as in the existing commercial DC furnace.

[0067] Accordingly, by selectively using or varying the ratio of the two lower electrodes (212a, 212b), the flow of electrical energy input to the second melting furnace (20) during the process can be controlled to induce effective melting operation. Although not shown, in connection with this, an auxiliary chemical energy input facility may also be applied to the lower side of the preheating supply unit (220) furnace wall.

[0068] In addition, the preheating supply unit (220) may be configured with a preheating chamber (221) that is formed to be elongated in the vertical direction (Z-axis direction) in a cylindrical or polygonal cylinder shape so that it can be formed as a finger type shaft furnace, and a chamber door (222) that is installed on the lower side of the open preheating chamber (221) and selectively opens the lower side of the preheating chamber (221) so that the second iron source (2) can be selectively supplied.

[0069] More specifically, the preheating supply unit (220) is a facility that preheats the second iron source (2) by utilizing waste heat generated in the first melting furnace (10) and the second melting furnace (20) (supplied to the preheating furnace 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 portion of the second melting furnace (20).

[0070] The electric furnace (1000) having a dual melting furnace (F) of the present invention is designed to be suitable for the production of high-grade steel that requires the use of large quantities of ore-based iron sources (OBM's), and thus the input ratio of the second iron source (2), which is scrap, may be much lower than that of a general electric furnace. Accordingly, it may be desirable for the preheating supply unit (220) to be designed with a capacity capable of containing the second iron source (2) required for a single melting operation at once.

[0071] In addition, in order to effectively utilize the waste heat generated in the first melting furnace (10), as shown in FIG. 1, in the preheating supply unit (220) described above, an exhaust gas duct (500) may be installed to connect the first upper cell (100) and the second upper cell (200) in the form of a duct so that 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 be connected to each other, thereby supplying the waste heat generated in the first melting furnace (10) to the second melting furnace (20).

[0072] 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 producing molten metal among the energy input into the furnace and is released into the atmosphere. However, when the bulkhead unit (400) to be 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), a problem may arise that the waste heat generated in the first melting furnace (10), which accounts for more than half of the main energy supply, is not supplied.

[0073] To solve this, an exhaust gas duct (500) connecting 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 be installed to secure a path for the waste heat generated in the first melting furnace (10). At the same time, the inlet of the exhaust gas supplied from the first melting furnace (10) on the second melting furnace (20) side can be positioned in the opposite direction of the preheating supply unit (220), so that the flow of the fluid passes through the arc generation point of the second melting furnace (20) and is then supplied to the preheating supply unit (220), thereby also performing a sealing function to block the arc generated in the second electrode unit (210) from the atmosphere.

[0074] Accordingly, the exhaust gas duct (500) connecting 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 perform two functions: recovering waste heat generated in the first melting furnace (10) and simultaneously blocking the phenomenon of nitrogen (N2) in the atmosphere being picked up by the arc current into the molten metal (3).

[0075] As shown in FIG. 1, the lower cell (300) is connected to the first upper cell (100) and the second upper cell (200) in a horizontal direction (X-axis direction) and a vertical direction (Z-axis direction) perpendicular to each other, so that 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 formed into one integrated space.

[0076] In addition, the lower cell (300) may have a discharge port (310) formed at a position opposite to the first electrode part (110) installed in the small ceiling of the first loop part (100a) formed on the upper side of 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 discharged, and the bottom surface forming the first lower space (A1-2) where the discharge port (310) is formed may be formed higher than the bottom surface forming the second lower space (A2-2).

[0077] For example, the dual melting furnace (F) of the present invention may have a structure in which the upper cells (100, 200) of the first melting furnace (10) and the second melting furnace (20) are configured as two separate forms, and the lower cell (300) is integrated into a single furnace form. This 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 may form a profile in which the bottom surface height on the first melting furnace (10) side is higher than the bottom surface on the second melting furnace (20) side only for the purpose of maintaining the tapping port (310). This may be a structure installed at the bottom of the first melting furnace (10) without a separate protruding part for installing the tapping port (310).

[0078] This structure of the lower cell (300) allows free movement of materials and heat, enabling integrated utilization of resources (electricity, chemical energy) separately configured in the first melting furnace (10) and the second melting furnace (20), and at the same time, enables a shortened process design that simultaneously utilizes the functions of heterogeneous slags (4a, 4b) separated in the first melting furnace (10) and the second melting furnace (20) by a partition unit (400) to be described later.

[0079] In addition, the discharge port (310) formed in the lower cell (300) is designed to eliminate an unnecessary cold zone by removing the protruding structure for discharge that is present in a commercial electric furnace, as described in the structure of the lower cell (300) described above. Accordingly, in selecting the location of the discharge port (310), in order to supply sand to be injected for sealing after discharge, as shown in FIG. 3, by positioning it directly below the inlet of one of the plurality of AC electrodes (111, 112, 113) of the first electrode unit (110), the sand injection tube can be configured to be lowered through the inlet of the AC electrode to fill the sand.

[0080] In addition, as shown in FIGS. 1 and 3, a gas discharge device (600) including a plurality of plugs (600a, 600b, 600c, 600d, 600e, 600f, 600g) for discharging gas can be arranged on the bottom surface of the lower cell (300) so as to control the flow of molten metal (3) between the first melting furnace (10) and the second melting furnace (20).

[0081] 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) to be described later by an integrated lower cell (300) and simultaneously implement melting and refining characteristics suitable for each purpose, the flow (material and heat flow) of the molten metal (3) must be controlled to suit the detailed process purpose. This may include forming a biased flow (a flow in which the main flow is concentrated in one direction, such as the first melting furnace (10) → the second melting furnace (20) or the second melting furnace (20) → the first melting furnace (10)) or forming a flow that quickly and uniformly mixes the entire volume of the molten metal (3).

[0082] To this end, a gas storage device (600) for implementing the desired flow control can be installed on the bottom surface of the lower cell (300) constituting the lower space (A1-2, A2-2) of the first melting furnace (10) and the second melting furnace (20). FIG. 3 shows an example in which plugs (600a, 600b, 600c, 600d, 600e, 600f, 600g) of the gas storage facility (600) are arranged on the bottom surface of the lower cell (300). The details of the device (type, size, number, location, etc. of plugs) are not necessarily limited to FIG. 3 and can be variously changed depending on the purpose. At this time, the type of gas injected through the gas storage facility (600) may be selectively injected as an inert gas (Ar, N2) for simple flow control or a fuel / raw material (O2, Ch4, CO, etc.) for reaction and heat source supply.

[0083] In addition, as shown in FIG. 1, on the lower side of the lower cell (300), a dual melting furnace (F) in the form of at least a portion of the first melting furnace (10) and the second melting furnace (20) combined may be installed with a tilting device (700) capable of tilting in the horizontal direction (X-axis direction) or in the width direction (Y-axis direction) perpendicular to the horizontal direction (X-axis direction) and the vertical direction (Z-axis direction).

[0084] More specifically, the tilting device (700) may be configured with a support cylinder (710) that tilts the dual melting furnace (F) at a portion corresponding to the center of the dual melting furnace (F) on the lower side of the dual melting furnace (F) so as to maintain the center of the dual melting furnace (F) tilted by the tilting device (700), and a plurality of drive cylinders (720) that are individually capable of being raised and lowered so that at least three are radially arranged around the support cylinder (710) so as to support the dual melting furnace (F) at at least three points, and the dual melting furnace (F) can be selectively tilted in the horizontal direction (X-axis direction) or the width direction (Y-axis direction).

[0085] For example, the support cylinder (710) of the tilting device (700) is a structure installed at the center of gravity of the dual melting furnace (F), which supports the dual melting furnace (F) and has a part that can tilt in the horizontal direction (X-axis direction) and the width direction (Y-axis direction), and a cylinder that is connected to this and into which a structure is inserted within the support surface of the dual melting furnace (F) so that only up / down movement is possible without a separate driving force, and can play a role in holding the position of the dual melting furnace (F). Such a support cylinder (710) is a device necessary to satisfy the need to change the tapping and slag discharge directions in order to implement the structural characteristics of the dual melting furnace (F) of the present invention.

[0086] And, the plurality of driving cylinders (720) of the tilting device (700) are control devices that tilt the actual dual melting furnace (F), and although their basic structure is similar to the support cylinder (710), they can be fixed to the support surface of the dual melting furnace (F) by hydraulic cylinders that provide driving force. These plurality of driving cylinders (720) can tilt the dual melting furnace (F) by at least three-point support, but in order to stably tilt the dual melting furnace (F), it may be desirable to configure a total of four cylinders, two on the side of the first melting furnace (10) and two on the side of the second melting furnace (20), based on the support cylinder (710) that holds the center of the dual melting furnace (F), to implement two-directional (horizontal direction (X-axis direction) and width direction (Y-axis direction)) tilting of the dual melting furnace (F).

[0087] As illustrated in FIG. 1, the bulkhead unit (400) is installed vertically (Z-axis direction) between the first upper cell (100) and the second upper cell (200) of the dual melting furnace (F) so as to be able to be raised and lowered, thereby selectively separating 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), which are formed integrally by the lower cell (300).

[0088] For example, scrap that is introduced into the second iron source (2) in the second melting furnace (20) and melted must form slag (4b) in an oxidizing atmosphere when melting. By operating in an oxidizing atmosphere to remove P, which is an impurity in the molten steel, oxygen ions in the slag (4b) can combine with P in the molten steel to form P2O5. This P2O5 can become a part of the slag (4b) and reduce P in the molten steel. Conversely, ore-based iron sources (OBM's) that are introduced into the first iron source (1) in the first melting furnace (10) and melted must form slag (4a) in a reducing atmosphere when melting. By removing the oxygen of the FeO remaining in the ore-based iron source (OBM's), the reduced Fe can be mixed into the molten steel and play a role in increasing the yield of the introduced ore-based iron source (OBM's).

[0089] When using ore-based iron sources (OBM's) and scrap at the same time, if the formed slag is reducing, the Fe yield increases, but P is picked up into the molten steel, increasing the P content. If the slag is oxidizing, it is advantageous for removing P, but the Fe yield decreases. To solve this, in a dual melting furnace (F) that combines two electric furnaces, the first melting furnace (10) which is a dedicated electric furnace for ore-based iron sources (OBM's) and the second melting furnace (20) which is a dedicated electric furnace for scrap, it is necessary to ensure that the slag (4a) according to ore-based iron sources (OBM's) and the slag (4b) according to scrap are not mixed with each other and can be produced simultaneously. Accordingly, a partition unit (400) that can separate the slags (4a, 4b) between the dual melting furnaces (F) may be essential.

[0090] In this way, the fundamental purpose of the dual melting furnace (F) of the present invention is to enable the melting and some refining operations of raw materials (OBM's vs. general scrap) with different properties, such as the first iron source (1) and the second iron source (2), to be performed simultaneously by separating the slag (4a) of the first melting furnace (10) and the slag (4b) of the second melting furnace (20), and to implement a process for producing high-speed / high-efficiency / high-quality molten metal (3) by excluding a large amount of slag that has lost its function or is not suitable for the final stage among the heterogeneous slags (4a, 4b) generated in each furnace (10, 20) before the integration of the first melting furnace (10) and the second melting furnace (20) for final refining and end-point control. This is a part that is impossible to implement when the corresponding raw material combination is applied to a conventional general electric furnace.

[0091] To this end, a partition unit (400) is configured as a device that controls the separation / integration of slag (4a, 4b) generated according to the detailed process steps, and the partition unit (400) is configured with a water-cooling structure and a refractory material and can be adjusted by a driving device that moves up / down between the first melting furnace (10) and the second melting furnace (20). This may be a main device that implements the dual melting furnace (F) of the present invention.

[0092] In this way, the first melting furnace (10) of the dual melting furnace (F) in which separation / integration can be selectively adjusted by the bulkhead unit (400) includes a first slag door (11) formed as a double door including an upper door (11a) that opens upward and a lower door (11b) that opens downward, formed to face each other in the vertical direction (Z-axis direction) so as to selectively exclude slag (4a) generated in the first melting furnace (10), formed at the boundary between the first upper cell (100) and the lower cell (300), and the second melting furnace (20) is formed as a single door that opens upward or downward, formed at the boundary between the second upper cell (200) and the lower cell (300), so as to selectively exclude slag (4b) generated in the second melting furnace (20). It may include a second slag door (21).

[0093] More specifically, the first slag door (11) formed by the double doors (11a, 11b) of the first melting furnace (10) is a device for controlling the level of a large amount of slag (4a) generated by melting of ore-based iron sources (OBM's) fed into the first iron source (1), and may have a structure that can be opened in the upper / lower directions by the double doors (11a, 11b).

[0094] The slag (4a) produced in the first melting furnace (10) is fundamentally different in composition from the slag (4b) of the general scrap operation produced in the second melting furnace (20), and this difference is controlled and maintained to some extent for the purpose. This is because the gangue components introduced from ore-based iron sources (OBM's) are mainly acidic (SiO2, Al2O3), forming a low-saltiness slag, and also has the characteristic of containing a large amount of FeO. The introduced FeO must be reduced and recovered as much as possible by adding C-based auxiliary materials, and the CO gas generated at this time foams the slag (4a). Since the generated slag (4a) is large in volume and foaming occurs, it is advantageous to maintain a low-saltiness state because it deteriorates the stability of the operation, but on the other hand, there is a conflicting problem that the arc cannot be stabilized without foaming.

[0095] For this reason, in the first melting furnace (10), it is necessary to confine a certain amount of slag (4a) in the furnace to suppress forming and protect the arc, which may also be advantageous for FeO reduction. Therefore, during operation, the upper door (11a) (water-cooled) that opens upward is opened to maintain a certain level of slag (4a), and when slag (4a) discharge is required, the lower door (11b) that opens downward can be opened to control this. At this time, in order to smoothly control a large amount of slag (4a), as illustrated in FIG. 2, the first slag door (11) may be configured as a multi-door in which a plurality of doors are formed along the perimeter of the first melting furnace (10).

[0096] In addition, the second slag door (21) of the second melting furnace (20) is a device that plays the same role as a conventional commercial electric furnace and can be utilized for discharging slag (4b) inside the furnace. In the present invention, if the first slag door (11) installed in the first melting furnace (10) has the characteristic of continuously discharging a large amount of slag (4a) generated after an appropriate measure to maintain an appropriate level, the second slag door (21) must be maintained in a sealed state except for a special purpose, and therefore, rather than a simple upward opening structure in the form of a water-cooled panel, it may have the characteristic of a structure that can be driven in two directions (Y-axis direction, Z-axis direction), so that it can be re-sealed after being opened during operation.

[0097] Below, the main features of the operation of the molten metal manufacturing process implemented through each detailed facility and device constituting the dual melting furnace (F) of the electric furnace (1000) of the present invention will be described.

[0098] As shown in Fig. 4, at the beginning of operation, the bulkhead unit (400) is lowered to the maximum, and in a state of separation of the first melting furnace (10) and the second melting furnace (20), the first melting furnace (10) can melt ore-based iron sources (OBM's) continuously fed into the first iron source (1) through a plurality of iron source supply units (120), and the second melting furnace (20) can preheat scrap, which is the second iron source (2), inside the preheating supply unit (220) through arcing while maintaining the forming of slag (4b), and additional melting energy can be supplied to the first melting furnace (10).

[0099] Next, as shown in Fig. 5, the level of the molten metal (3) rises (Level 1 → Level 2) by the melting process of the first melting furnace (10), and when the risen level (Level 2) reaches a level at which the second iron source (2) being preheated is completely submerged in the molten metal (3), the chamber door (222) can be opened to load the second iron source (2) preheated in the preheating chamber (221).

[0100] In this way, by charging the second iron source (2) preheated according to the level of the molten metal (3), it is possible to secure the melting efficiency of the second iron source (2), which is scrap, while at the same time preventing nitrogen (N) pickup due to arcing.

[0101] At this time, the baffle unit (400) is raised in accordance with the level of the rising molten metal (3), so that the flow channel of the molten metal (3) between the lower spaces (A1-2, A2-2) of the first melting furnace (10) and the second melting furnace (20) can be expanded (material and heat exchange activated). In addition, the first electrode unit (110) of the first melting furnace (10) and the second electrode unit (210) of the second melting furnace (20) can also be appropriately raised in accordance with the level of the rising molten metal (3).

[0102] Next, as illustrated in FIG. 6, in the first melting furnace (10), upward opening of the upper door (11a) of the first slag door (11) may occur for level control of the slag (4a), and in the second melting furnace (20), melting of the second iron source (2) charged with the molten metal (3) and preheating of the new second iron source (2) temporarily stored in the preheating supply unit (220) for the next operation may occur. At this time, as the partition wall unit (400) is further raised in accordance with the level of the raised molten metal (3), the flow channel of the molten metal (3) between the lower spaces (A1-2, A2-2) of the first melting furnace (10) and the second melting furnace (20) may be further expanded (material and heat exchange may be activated). In addition, 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 be continuously raised in accordance with the level of the rising molten metal (3).

[0103] Next, as illustrated in Fig. 7, by fully raising and fully opening the bulkhead unit (400), the slag (4a) (a factor in reducing refining performance) of the first melting furnace (10) is discharged by upward opening of the upper door (11a) of the first slag door (11), and then mixed with the slag (4b) of the second melting furnace (20) to perform final refining. In this way, the effect of maximizing refining efficiency can be achieved by expanding the refining reaction interface area through the full opening of the bulkhead unit (400).

[0104] Throughout the entire process of the above-described drawings 4 to 7, a continuous refining reaction can be maintained in the second melting furnace (20) through material and heat exchange by the lower cell (300) in which the first melting furnace (10) and the second melting furnace (20) are integrated, and finally, as shown in Drawing 7, the maximum refining capacity can be secured after the baffle unit (400) is fully opened. At this time, the first melting furnace (10) can reduce a large amount of FeO introduced from ore-based iron sources (OBM's) by maintaining the reducing slag (4a) until the baffle unit (400) is fully opened.

[0105] In addition, as shown in Fig. 8, when the molten metal (3) inside the double melting furnace (F) is discharged, the drive cylinder (720) on the second melting furnace (20) side of the tilting device (700) is raised, thereby causing the double melting furnace (F) to be tilted in the horizontal direction (X-axis direction), so that the double melting furnace (F) can be tilted in the direction of the first melting furnace (10) in which the discharge port (310) is formed.

[0106] In addition, as illustrated in FIG. 9, when the partition unit (400) separates the first melting furnace (10) and the second melting furnace (20) during operation, and when forced discharge of slag (4a) inside the first melting furnace (10) or slag (4b) inside the second melting furnace (20) is required, the inner drive cylinder (720) in the width direction (Y-axis direction) of the tilting device (700) is raised so that the dual melting furnace (F) can be tilted in the width direction (Y-axis direction) so that the dual melting furnace (F) can be tilted toward the first slag door (11) of the first melting furnace (10) and the second slag door (21) of the second melting furnace (20).

[0107] In order to smoothly tilt the dual melting furnace (F) as described above, such as in FIG. 8 or FIG. 9, the preheating supply unit (220) can be formed in a form that is separable from the dual melting furnace (F), and the driving procedure for lowering the main body of the dual melting furnace (F) and tilting in the desired direction can be performed by the special tilting device (700) proposed in the present invention.

[0108] Accordingly, according to an electric furnace (1000) according to one embodiment of the present invention, it is based on parallel input of ore-based iron sources (OBM's: Ore Based Materials) and low-particle scrap, and general scrap, and effectively separates the gangue component that is introduced in large quantities from the ore-based iron source so that it is not mixed with the existing slag (the gangue composed mainly of SiO2 and Al2O3 acts mainly as acidic slag, and when the amount introduced is large, a large amount of CaO is introduced to refine / remove the P component in the molten steel, and the increase in the unit cost of the slag and the large amount of slag generated as a result act as major factors that create an uneconomical structure such as a decrease in the molten steel recovery rate, an increase in energy consumption, and an increase in operating time), thereby implementing a dual melting furnace that can perform refining while melting the main raw material.

[0109] In this way, the present invention relates to a new concept electric furnace melting method that can secure productivity / economic efficiency / quality equal to or greater than that of the conventional “blast furnace-converter” production system while simultaneously injecting a large amount of ore-based iron (typically DRI) in order to convert the conventional “blast furnace-converter” production system into an “electric furnace” production system, and can have the effect of realizing carbon neutrality in steel production as a new type of electric furnace that can use a large amount of ore-based iron.

[0110] For example, when applying an electric furnace having a dual melting furnace structure of the present invention, the operational impact of a large amount of gangue flowing in from the DRI can be effectively separated and discharged from the first melting furnace, thereby maintaining / managing optimal refining conditions, and a large amount of DRI can be applied using a high-efficiency first melting furnace dedicated to ore-based iron sources, thereby enabling reduction of tramp components, and a method of inputting / operating scrap through the first melting furnace into which ore-based iron sources are continuously charged and the second melting furnace connected thereto in a dual structure can achieve complete flat bath operation, and the effect of blocking nitrogen pickup through arc sealing due to the exhaust gas duct structure can be obtained, thereby making it possible to secure the tapping N level of the converter. In addition, the high-energy intensive structure of the first melting furnace, the scrap preheating of the second melting furnace using exhaust gas, and the simultaneous operation of the first and second melting furnaces can shorten the operation to the level of a converter furnace, with energy consumption below the level of general scrap operation.

[0111] For example, as shown in FIGS. 10 and 11, when the DR-class DRI of Table 1 is applied in large quantities based on the actual operating performance of a commercial electric furnace, the effect of the present invention is compared with the expected operating indicators of the commercial electric furnace and the present invention, as shown in Table 2. At this time, the expected operating performance is reflected by performing a simple energy and material calculation targeting the main indicators that change during the applied operation based on the components of the DRI of FIG. 10.

[0112] As shown in Table 2 of Fig. 11, the power consumption was 617 kWh / ton in a commercial electric furnace, but according to the expected operating indicator of the present invention, it is expected to be 361 kWh / ton, indicating that the power consumption was reduced by nearly half. The operating time was 84 minutes in a commercial electric furnace, but according to the expected operating performance of the present invention, it was expected to be 39 minutes, indicating that the operating time was also reduced by nearly half. At this time, the Cu level and N level can be controlled to a level similar to that of a furnace, ≤0.03% and ≤30 ppm, respectively, and it was expected that all of the expected operating indicators of the present invention would be the same as or better than those of a commercial scrap electric furnace.

[0113] Here, the operating results of the commercial electric furnace of Fig. 11 are the average performance of 100% scrap actual operation performed in the standard operating commercial electric furnace, and the expected operating index of the embodiment of the present invention corresponds to the case where DRI 80% + scrap 20% is applied.

[0114] While the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will appreciate that various modifications and equivalent alternative embodiments are possible. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the appended claims.

Claims

1. In an electric furnace having a dual melting furnace in which at least 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 the first iron source is introduced and melted; A second upper cell formed by the first upper cell and the second upper space of the second melting furnace, which is arranged in the horizontal direction and into which the second iron source is introduced and melted; A lower cell coupled to the lower portion of the first upper cell and the second upper cell, thereby forming 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 that is vertically movably installed between the first upper cell and the second upper cell, and separates the first lower space of the first melting furnace and the second lower space of the second melting furnace, which are formed integrally by the lower cell; Including, electric.

2. In paragraph 1, The above first upper cell, An electric furnace in which the furnace wall is formed of a refractory material so that the first melting furnace can have a heat-resistant structure.

3. In paragraph 1, The above first upper cell, A first electrode part, at least a portion of which is inserted into the first upper space of the first melting furnace through a small ceiling of the first loop part formed on the upper side of the first upper cell, to melt the first iron source by arc heat; and A plurality of iron source supply units arranged radially based on the center of the first electrode unit and supplying the first iron source through the first upper space of the first melting furnace; Including, electric.

4. In paragraph 3, The above first electrode part, It includes a plurality of alternating current (AC) electrodes arranged radially based on the center of the small ceiling of the first loop section, The above multiple iron supply units are: An electric furnace in which each individual iron source supply unit continuously supplies the first iron source toward the fire point of its corresponding individual alternating current electrode.

5. In paragraph 1, The second upper cell is, A second electrode part, at least a portion of which is inserted into the second upper space of the second melting furnace through a small ceiling of the second loop part formed on the upper side of the second upper cell, to melt the second iron source by arc heat; and A preheating supply unit installed on one side of the second electrode portion at the upper side of the second upper cell, temporarily storing a predetermined amount of the second iron source in the 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; Including, electric.

6. In paragraph 5, The above second electrode part, An upper direct current (DC) electrode inserted through the small ceiling of the second loop section and formed on the second upper space side of the second melting furnace; and A lower DC electrode is installed on the bottom surface of the lower cell so as to be opposite to the upper DC electrode in the vertical direction, and is formed on the second lower space side of the second melting furnace; The above 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 to face the upper DC electrode head-on; and A second lower electrode formed so 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 face the upper DC electrode in an inclined direction, and is formed so as to be deflected toward the preheating supply unit with respect to the upper DC electrode; Including, electric.

7. In paragraph 6, The above second electrode part, An electric furnace in which, immediately after the preheating supply unit supplies the second iron source, current is energized between the upper DC electrode and the second lower electrode, and after the melting of the second iron source is completed, current is energized between the upper DC electrode and the first lower electrode.

8. In paragraph 1, An electric furnace in which the volume of the first melting furnace, which is formed by the first upper space of the first upper cell and the first lower space of the lower cell, is smaller than the volume of the second melting furnace, which is formed by the second upper space of the second upper cell and the second lower space of the lower cell.

9. In paragraph 1, An exhaust gas duct that connects the first upper cell and the second upper cell 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 be connected to each other, and supplies waste heat generated in the first melting furnace to the second melting furnace; Including more, electric.

10. In paragraph 1, The above first melting furnace is, A first slag door formed as a double door including an upper door that opens upward and a lower door that opens downward, formed at a boundary portion between the first upper cell and the lower cell so as to be formed facing each other in the vertical direction so as to selectively discharge slag generated in the first melting furnace; Including, electric.

11. In paragraph 10, The above first melting furnace is, An electric furnace in which the upper door is opened during operation so that the height of the slag inside the first melting furnace can be maintained at a predetermined level, and the lower door is opened when the slag inside the first melting furnace is to be discharged.

12. In paragraph 1, The above second melting furnace is, A second slag door formed at the boundary between the second upper cell and the lower cell, and formed as a single door that opens upward or downward, so as to selectively discharge slag generated in the second melting furnace; Including, electric.

13. In paragraph 1, A gas discharge device including a plurality of plugs arranged 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; Including more, electric.

14. In paragraph 1, The above lower cell is, An electric furnace in which a discharge port is formed at a position opposite to a first electrode part installed in a small ceiling of a first loop part formed on the upper side of the first upper cell on the bottom surface forming the first lower space so as to discharge molten metal inside the double melting furnace.

15. In paragraph 14, The above lower cell is, An electric furnace in which the floor surface forming the first lower space in which the above discharge port is formed is formed higher than the floor surface forming the second lower space.

16. In paragraph 14, A tilting device capable of tilting the double melting furnace in the horizontal direction or in a width direction perpendicular to the horizontal direction and the vertical direction, wherein at least a portion of the first melting furnace and the second melting furnace are combined; Including more, electric.

17. In paragraph 16, The above-mentioned driving device is, A support cylinder that tilts and supports the dual melting furnace in a portion corresponding to the center of the dual melting furnace on the lower side of the dual melting furnace so as to maintain the center of the dual melting furnace tilted by the tilting device; and A plurality of drive cylinders, each of which is radially arranged around the support cylinder so as to support the double melting furnace at least at three points, and capable of individually moving up and down so as to selectively tilt the double melting furnace in the horizontal direction or the width direction; Including, electric.

18. In paragraph 16, The above-mentioned driving device is, An electric furnace in which, when molten metal inside the double melting furnace is tapped, the double melting furnace is tilted in the horizontal direction so that the double melting furnace can be tilted toward the first melting furnace in which the tapping port is formed, and when slag inside the first melting furnace or slag inside the second melting furnace is discharged, the double melting furnace is tilted in the width direction so that the double melting furnace can be tilted toward the first slag door of the first melting furnace and the second slag door of the second melting furnace.

19. In paragraph 5, The above preheating supply unit, A preheating chamber formed to be elongated in the vertical direction in a cylindrical or polygonal cylinder shape so that it can be formed into a finger type shaft furnace; and A chamber door installed at the lower side of the open preheating chamber and selectively opening the lower side of the preheating chamber; Including, electric.

20. In paragraph 1, The first iron source injected into the first melting furnace is, Includes ore-based materials (OBMs), The second iron source injected into the second melting furnace is, Electric furnace, including scrap.

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