Electric furnace operation method

Abstract

A method for operating an electric furnace is provided, which includes melting a first iron source in a first melting furnace having a first electrode unit disposed therein, preheating a second iron source in a second melting furnace having a second electrode unit disposed therein, and melting the second iron source in the second melting furnace, wherein the first melting furnace and the second melting furnace share an internal space, and the second electrode unit emits a first gas in the preheating of the second iron source, and the second electrode unit emits a second gas different from the first gas in the melting of the second iron source.

Description

[Technical Field]

[0001] The present invention relates to a method for operating an electric furnace. [Background technology]

[0002] Generally, the steel material production process in the steel industry can be broadly divided into a blast furnace-converter production system (converter process) that uses ore as the main raw material, and an electric furnace production system (electric furnace process) that uses scrap as the main raw material, which is recovered and reused after the produced steel material is made into products.

[0003] The converter process is widely used to produce high-quality products based on ore, especially plate materials that are sensitive to surface defects. The electric arc furnace process is generally used to produce bars and sections that require high strength, as scrap can contain impurities (Cu, Sn, Cr, Mo, Ni, etc., collectively referred to as tramp elements).

[0004] Recently, as carbon neutrality has become a global issue, the electric arc furnace process, which produces less than 20% of the CO2 emissions of the converter process, has emerged as an alternative for future steel production.

[0005] In the case of the electric furnace process, surface defects generated during the continuous casting process due to tramp elements flowing in from the scrap tend to deepen through the rolling process, resulting in poor workability.

[0006] To overcome these limitations, the active use of ore-based materials (OBMs) (e.g., DRI, HBI, PI, GPI, etc.) is considered an alternative.

[0007] A typical example is direct reduced iron (DRI / HBI), which, unlike blast furnaces, produces iron by processing iron ore into pellets and then reacting them with reducing gas to directly reduce them.Currently, there is a growing trend for electric arc furnace steel companies to apply this method to commercial facilities to produce plate materials.

[0008] When ore-based iron sources are fed into an electric furnace, a large amount of unreduced iron oxide (FeO) may be contained due to the reduction structure in which reducing gas penetrates and reacts with the solid raw material, which can increase the amount of slag generated and reduce the recovery rate of molten steel.

[0009] In addition, due to the process characteristics of melting scrap using an arc (electrical energy), nitrogen (N2) gas in the air around the electrode can become ionized (plasma) and be injected into the molten steel through the arc flow, making it difficult to control the nitrogen (N2) content. Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a method for operating an electric furnace that can effectively reduce iron oxide (FeO) contained in slag and improve the recovery rate of molten steel even when direct reduced iron is used in the electric furnace.

[0011] Another object of the present invention is to provide a method for operating an electric furnace that can more smoothly control the nitrogen (N2) content in molten steel in the electric furnace.

[0012] The problems to be solved by the present invention are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0013] According to an embodiment of the method for operating an electric furnace for solving the above problem, the method includes the steps of melting a first iron source in a first melting furnace having a first electrode unit disposed therein, preheating a second iron source in a second melting furnace having a second electrode unit disposed therein, and melting the second iron source in the second melting furnace, wherein the first melting furnace and the second melting furnace share an internal space, and the second electrode unit releases a first gas in the step of preheating the second iron source, and the second electrode unit releases a second gas different from the first gas in the step of melting the second iron source.

[0014] The first gas may include a reducing gas, and the second gas may include an inert gas.

[0015] The reducing gas may include at least one selected from carbon dioxide (CO2) gas, methane (CH4) gas, and hydrogen (H2) gas, and the inert gas may include argon (Ar) gas.

[0016] The first gas may further include an inert gas.

[0017] The step of melting the second iron source includes an initial melting stage and a later melting stage, and the second electrode unit may emit the second gas in the initial melting stage, and may emit a third gas different from the second gas in the later melting stage.

[0018] The second gas may include an inert gas, and the third gas may include a reducing gas.

[0019] The second electrode may be exposed to the outside during the initial melting stage, and at least a portion of the second electrode may be immersed in the slag during the later melting stage.

[0020] The step of melting the first iron source may be carried out simultaneously with the steps of preheating the second iron source and melting the second iron source.

[0021] In the melting of the first iron source, the first electrode unit may emit a third gas.

[0022] The third gas may include a reducing gas.

[0023] The method may further include a step of refining molten metal by mixing the first slag in the first melting furnace and the second slag in the second melting furnace, wherein in the step of refining the molten metal, the first electrode unit may emit a third gas, and the second electrode unit may emit a fourth gas, and the third gas and the fourth gas may include a reducing gas.

[0024] The first electrode unit may include a first AC electrode, a second AC electrode, and a third AC electrode, and the second electrode unit may include an upper DC electrode and a lower DC electrode.

[0025] The upper DC electrode may include an inner tube defined by penetrating the upper DC electrode in a lengthwise direction and through which at least one of the first gas and the second gas can flow, a gas supply part located on one side of the inner tube and through which at least one of the first gas and the second gas is supplied, and a gas discharge part located on the other side of the inner tube and through which at least one of the first gas and the second gas is discharged.

[0026] The first iron source can include an ore-based iron source and the second iron source can include scrap.

[0027] According to one embodiment of the present invention, a method for operating an electric furnace includes a step of introducing an iron source into an electric furnace including electrodes, a step of applying electric power to the electrodes to melt the iron source, and a step of introducing oxygen into the electric furnace to perform refining, wherein the electrode units release a first gas in the step of melting the iron source, and the electrode units release a second gas different from the first gas in the step of refining.

[0028] The first gas may include an inert gas, and the second gas may include a reducing gas.

[0029] The electrode unit may include a first AC electrode, a second AC electrode, and a third AC electrode.

[0030] Each of the first AC electrode, the second AC electrode, and the third AC electrode may emit at least one of the first gas and the second gas from inside.

[0031] According to one embodiment of the present invention, a method for operating an electric furnace includes an electrode rod, and defines a space for accommodating at least one of an iron source, molten iron, and slag therein. The method includes discharging a first gas including an inert gas from the electrode rod, and discharging a second gas including a reducing gas from the electrode rod, wherein one end of the electrode rod is exposed in the discharging of the first gas, and the one end of the electrode rod is positioned inside the slag in the discharging of the second gas.

[0032] The electrode rod may include an inner tube through which the first gas and the second gas flow, and a gas discharge part located on one side of the inner tube and discharging the first gas and the second gas, and the gas discharge part may be disposed at a tip of the one side of the electrode rod.

[0033] Other exemplary embodiments are included in the detailed description and drawings. [Effects of the Invention]

[0034] According to an embodiment of the method for operating an electric furnace, even when direct reduced iron is used in an electric furnace, iron oxide (FeO) contained in slag can be effectively reduced, thereby improving the recovery rate of molten steel.

[0035] According to the method for operating an electric furnace according to an embodiment, the nitrogen (N2) content in molten steel in the electric furnace can be more smoothly controlled.

[0036] The effects of the embodiments are not limited to the above examples, and a wider variety of effects are included within the present specification. [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an electric furnace according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of an upper DC electrode according to one embodiment. [Figure 3] FIG. 3 is a flowchart of a method for operating an electric furnace according to one embodiment. [Figure 4] 4 to 9 are cross-sectional views showing the process steps of an electric furnace operating method according to one embodiment. [Figure 5] 4 to 9 are cross-sectional views showing the process steps of an electric furnace operating method according to one embodiment. [Figure 6] 4 to 9 are cross-sectional views showing the process steps of an electric furnace operating method according to one embodiment. [Figure 7] 4 to 9 are cross-sectional views showing the process steps of an electric furnace operating method according to one embodiment. [Figure 8] 4 to 9 are cross-sectional views showing the process steps of an electric furnace operating method according to one embodiment. [Figure 9] 4 to 9 are cross-sectional views showing the process steps of an electric furnace operating method according to one embodiment. [Figure 10] FIG. 10 is a graph showing the behavior of nitrogen at each stage of the electric furnace operation method. [Figure 11] FIG. 11 is a flowchart of a method for operating an electric furnace according to another embodiment. [Figure 12] 12A to 12C are cross-sectional views showing the process steps of the electric furnace operating method according to the embodiment of FIG. [Figure 13] 13A to 13C are cross-sectional views showing the process steps of the electric furnace operating method according to the embodiment of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0038] The advantages and features of the present invention, as well as methods for achieving them, will become apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in various different forms. These embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully convey the scope of the invention to those skilled in the art. The present invention is defined only by the scope of the claims.

[0039] As used herein, when a component (or region, layer, portion, etc.) is referred to as being "on," "coupled," or "bonded" to another component, it means that it may be directly disposed / coupled / bonded to the other component, or that a third component may be disposed therebetween.

[0040] The same reference numerals refer to the same elements, and in the drawings, thicknesses, ratios, and dimensions of elements are exaggerated for the purpose of effectively explaining the technical contents.

[0041] "And / or" includes all combinations of one or more of the associated constructs that can be defined.

[0042] Terms such as "first," "second," etc. may be used to describe various components, but the components should not be limited by these terms. These terms are used only to distinguish one component from another. For example, a first component may be designated as a "second component," and similarly, a second component may be designated as a "first component" without departing from the scope of the present invention. A singular expression includes a plural expression unless the context clearly indicates a different meaning.

[0043] Furthermore, terms such as "under," "below," "on," and "above" are used to describe the relative relationships of components shown in the drawings. These terms are relative concepts and are described based on the directions shown in the drawings.

[0044] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by a person skilled in the art to which this invention belongs. Furthermore, terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art, and are not interpreted in an idealized or overly formal sense unless expressly defined herein.

[0045] It should be understood that the use of terms such as "comprise" or "have" is intended to specify the presence of a stated feature, number, step, operation, component, part, or combination thereof, but does not preclude the presence or possible addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0046] FIG. 1 is a cross-sectional view schematically illustrating an electric furnace according to an embodiment.

[0047] Referring to FIG. 1, an electric furnace 1000 according to one embodiment may include a first upper cell 100, a second upper cell 200, a lower cell 300, a partition unit 400, an exhaust gas duct 500, a bottom gas blowing device 600, and a tilting device 700.

[0048] The electric furnace 1000 may have a double furnace structure that forms a single body that shares the lower cell 300. In the electric furnace 1000, the first upper cell 100 and the second upper cell 200 each share the lower cell 300 and may be coupled to the lower cell 300.

[0049] The electric furnace 1000 may further include a first melting furnace 10 and a second melting furnace 20 capable of melting different iron sources. The first upper cell 100 and the lower cell 300 constitute the first melting furnace 10 and may define a first upper space A1-1 and a first lower space A1-2 of the first melting furnace 10. The second upper cell 200 and the lower cell 300 constitute the second melting furnace 20 and may define a second upper space A2-1 and a second lower space A2-2 of the second melting furnace 20.

[0050] The electric furnace 1000 may include a double melting furnace F, which is formed by structurally combining at least a portion of a first melting furnace 10 and a second melting furnace 20. The double melting furnace F may have a structure in which the upper cells 100 and 200 of the first melting furnace 10 and the second melting furnace 20 are separately constructed, and the lower cell 300 is constructed as a single cell. The first melting furnace 10 and the second melting furnace 20 may be interconnected to share an internal space defined by the upper cells 100 and 200 and the lower cell 300.

[0051] The lower cell 300 may include a tapping port 310 through which the molten metal 3 and / or slag 4a, 4b of the first melting furnace 10 and the second melting furnace 20 may be tapped. The tapping port 310 may be located on the first melting furnace 10 side.

[0052] However, the position of the tapping hole 310 is not limited to that shown in the figure, and the tapping hole 310 may be disposed on the second melting furnace 20 side. Alternatively, the tapping hole 310 may be disposed on both the first melting furnace 10 and the second melting furnace 20.

[0053] The first melting furnace 10 may have a space therein for accommodating the first iron source 1, the first slag 4a, and the molten metal 3. The first melting furnace 10 may receive the first iron source 1 and melt it. The first iron source 1 may be continuously fed into the first melting furnace 10 by an iron source supply unit 120. The first melting furnace 10 may include a continuous melting structure that may control energy input according to the feeding rate of the first iron source 1.

[0054] Although not limited thereto, the first iron source 1 may include ore-based materials (OBM's) (iron oxide, DRI, HBI, PI, GPI, LRI, etc.), and may also include some low-grain scrap (Shredder, incoming wire, etc.).

[0055] The first melting furnace 10 may include a first slag door 11. The first slag 4a inside the first melting furnace 10 may be selectively discharged through the first slag door 11. This allows the level of the first slag 4a inside the first melting furnace 10 to be controlled.

[0056] A plurality of first slag doors 11 may be provided along the periphery of the first melting furnace 10 near the boundary between the first upper cell 100 and the lower cell 300. The first slag door 11 may include an upper door 11a that opens upward (to one side of the Z axis) and a lower door 11b that opens downward (to the other side of the Z axis). In other words, the first slag door 11 may be a double door.

[0057] However, the structure of the first slug door 11 is not limited to the above, and the first slug door 11 may be implemented as a single door to perform opening and closing operations.

[0058] The second melting furnace 20 may have a space therein for storing the second iron source 2, the second slag 4b, the molten metal 3, etc. The molten metal 3 may be stored throughout the first melting furnace 10 and the second melting furnace 20.

[0059] The second melting furnace 20 may be charged with and melt a second iron source 2, which is different from the first iron source 1. The second iron source 2 may be preheated through a preheat supply unit 220 before being introduced into the second melting furnace 20. This may improve the operating speed and efficiency of the second melting furnace 20.

[0060] Although not limited thereto, the second iron source 2 may include scrap, and may also include a portion of a high-particle ore-based iron source.

[0061] The second melting furnace 20 may include a second slag door 21. The second slag 4b inside the second melting furnace 20 may be selectively discharged through the second slag door 21. This allows the level of the second slag 4b inside the second melting furnace 20 to be controlled.

[0062] A plurality of second slag doors 21 may be provided along the periphery of the second melting furnace 20 near the boundary between the second upper cell 200 and the lower cell 300. The second slag door 21 may include a shape that can be resealed after being opened during operation.

[0063] The first upper cell 100 may include a first electrode unit 110 and at least one iron source supply unit 120 .

[0064] The first electrode unit 110 may be disposed in the first melting furnace 10. The first electrode unit 110 may penetrate the first upper cell 100 and at least a portion thereof may be inserted into the first upper space A1-1 of the first melting furnace 10. The first electrode unit 110 may generate arc heat, and the first iron source 1 charged inside the first melting furnace 10 may be melted by the arc heat.

[0065] The first electrode unit 110 may include first to third AC electrodes 111, 112, and 113. Three-phase AC may be applied to the first electrode unit 110 through the first to third AC electrodes 111, 112, and 113. The first to third AC electrodes 111, 112, and 113 may be connected to a power source (not shown) that can provide power.

[0066] The first electrode unit 110 may be connected to a gas supply pipe GP. Specifically, the first to third AC electrodes 111, 112, and 113 may be connected to the first to third gas supply pipes GP1, GP2, and GP3, respectively.

[0067] The first to third AC electrodes 111, 112, and 113 can receive various types of gases from a gas storage tank GS through the first to third gas supply pipes GP1, GP2, and GP3. The gas storage tank GS can include multiple sub-tanks that store different types of gases.

[0068] The first to third AC electrode rods 111, 112, and 113 may eject different gases depending on the operation stage of the electric furnace 1000. This allows each operation stage of the electric furnace 1000 to proceed more smoothly, which will be described in detail later.

[0069] The iron source supply units 120 may be arranged radially based on the center of the first electrode unit 110. The iron source supply units 120 may supply the first iron source 1 into the first melting furnace 10. The plurality of iron source supply units 120 may continuously supply the first iron source 1 to three hot spots formed between the first to third AC electrode rods 111, 112, and 113, thereby improving melting efficiency.

[0070] The second upper cell 200 may be disposed alongside the first upper cell 100. The second upper cell 200 may include a second electrode unit 210 and a preheat supply unit 220.

[0071] The second electrode unit 210 may be disposed in the second melting furnace 20. The second electrode unit 210 may penetrate the first upper cell 100 and at least a portion thereof may be inserted into the second upper space A2-1 of the second melting furnace 20. The second electrode unit 210 may generate arc heat, and the second iron source 2 charged inside the second melting furnace 20 may be melted by the arc heat.

[0072] The second electrode unit 210 may include an upper DC electrode 211 and a lower DC electrode 212. The upper DC electrode 211 and the lower DC electrode 212 may be disposed to face each other. The upper DC electrode 211 and the lower DC electrode 212 may be electrically connected to each other to generate an arc.

[0073] The lower DC electrode 212 may include a first lower electrode 212a and a second lower electrode 212b. The first lower electrode 212a may be disposed to face the upper DC electrode 211 along the longitudinal direction of the upper DC electrode 211. The second lower electrode 212b may be disposed to be biased toward the preheat supply unit 220 with respect to the upper DC electrode 211.

[0074] Immediately after the second iron source 2 is supplied to the second melting furnace 20, the second electrode unit 210 can cause current to flow between the upper DC electrode 211 and the second lower electrode 212b. After the melting of the second iron source 2 is completed, the second electrode unit 210 can cause current to flow between the upper DC electrode 211 and the first lower electrode 212a.

[0075] Depending on whether the second iron source 2 is to be melted or not, the upper DC electrode 211 selectively energizes different lower electrodes, thereby controlling the flow of input electric energy and leading to an effective melting operation.

[0076] The upper DC electrode 211 may be connected to a fourth gas supply pipe GP4 of the gas supply pipe GP. Through the fourth gas supply pipe GP4, the upper DC electrode 211 may receive various types of gases from a gas storage tank GS.

[0077] The upper DC electrode 211 may eject different gases depending on the operation stage of the electric furnace 1000. This may allow each operation stage of the electric furnace 1000 to proceed more smoothly, as will be described in detail later.

[0078] The first to third AC electrode rods 111, 112, and 113 and the upper DC electrode 211 may include spaces therein through which gas can flow, and the gas can be ejected through the spaces. For a detailed description of this, please refer to FIG. 2.

[0079] FIG. 2 is a cross-sectional view of an upper DC electrode 211 according to one embodiment.

[0080] Although the description will be made based on the upper DC electrode 211 in FIG. 2, the description of the upper DC electrode 211 can be applied to each of the first to third AC electrodes 111, 112, and 113 in substantially the same manner.

[0081] 2, the upper DC electrode 211 is connected to a fourth gas supply pipe GP4 and may receive gas from the fourth gas supply pipe GP4, and may discharge the supplied gas from the internal space to the outside.

[0082] The upper DC electrode 211 may emit different gases depending on the operation stage. The gas emitted from the upper DC electrode 211 may be at least one selected from an inert gas, a reducing gas, and a heat source gas.

[0083] The inert gas may include, but is not limited to, argon (Ar) gas, and each of the reducing gas and the heat source gas may include at least one selected from hydrogen (H) gas, carbon dioxide (CO) gas, and methane (CH) gas.

[0084] The upper DC electrode 211 may include an electrode body 211a and a line fastening part 211b that are coupled to each other. The line fastening part 211b may include a screw thread, and the screw thread may be inserted into the electrode body 211a to couple the electrode body 211a and the line fastening part 211b to each other.

[0085] However, the structure of the upper DC electrode 211 is not limited to this, and may be embodied in a structure in which the upper part of the electrode body 211a is inserted into the line fastening part 211b and screwed together.

[0086] The electrode main body 211a may generate arc heat when supplied with electric power. The line connecting part 211b may connect the fourth gas supply pipe GP4 to the electrode main body 211a so that gas may be supplied toward the electrode main body 211a.

[0087] The upper DC electrode 211 may define an inner tube IP, a gas supply portion SP, and a gas discharge portion EM. The inner tube IP may be defined by an electrode body portion 211a and a line connection portion 211b.

[0088] The inner pipe IP may be defined to penetrate the upper DC electrode 211 along the length direction of the upper DC electrode 211. The inner pipe IP may penetrate the electrode body 211a and the line fastening portion 211b to provide a space through which gas can flow. The inner pipe IP may extend along the length direction (Z-axis direction) of the upper DC electrode 211.

[0089] The gas supply unit SP is located on one side of the inner pipe IP in the Z-axis direction and can receive gas from the fourth gas supply pipe GP4. The gas discharge unit EM is located on the other side of the inner pipe IP in the Z-axis direction and can discharge gas flowing in the inner pipe IP to the outside of the upper DC electrode 211. The gas discharge unit EM can be located at the other end of the upper DC electrode 211 in the longitudinal direction (Z-axis direction).

[0090] 1 again, the preheating supply unit 220 may store the second ferrous source 2 and preheat the second ferrous source 2 before charging it into the second melting furnace 20. The preheating supply unit 220 may include a finger-type shaft furnace. In this case, maintenance, repair, and operation of the preheating supply unit 220 may be easier.

[0091] The preheat supply unit 220 may preheat the second iron source 2 stored therein by utilizing waste heat generated from the first melting furnace 10 or the second melting furnace 20. In this case, the waste heat may be supplied to the preheat supply unit 220 in the form of exhaust gas.

[0092] The preheat supply unit 220 may include a preheat chamber 221 and a chamber door 222. The preheat supply unit 220 may be disposed at the top (one side in the Z-axis direction, opposite to gravity) of the second melting furnace 20. The second melting furnace 20, which is composed of the second upper cell 200 and the lower cell 300, may include the preheat supply unit 220.

[0093] The preheating chamber 221 may extend in the Z-axis direction and have a storage space for storing the second iron source 2. The preheating chamber 221 may have a cylindrical or polygonal tubular shape. The preheating chamber 221 may have one or more charging gates disposed on the top or side thereof for charging the second iron source 2.

[0094] The chamber door 222 is disposed below the preheating chamber 221 (the other side in the Z-axis direction, in the direction of gravity) and can selectively open the lower side of the preheating chamber 221. Thus, scrap stored inside the preheating chamber 221 can be selectively supplied into the second melting furnace 20.

[0095] The opening and closing rate of the chamber door 222 can be adjusted, thereby selectively controlling the amount of scrap fed into the second melting furnace 20.

[0096] The partition unit 400 may be disposed between the first upper cell 100 and the second upper cell 200 and may extend in the Z-axis direction. The partition unit 400 may be disposed between the first melting furnace 10 and the second melting furnace 20.

[0097] The partition wall unit 400 may include refractory to withstand the temperature of the molten metal or slag. The partition wall unit 400 may be replaceably coupled to the first upper cell 100 and the second upper cell 200.

[0098] The partition unit 400 can be raised and lowered to selectively separate 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.

[0099] The partition unit 400 can separate the first slag 4a located inside the first smelting furnace 10 from the second slag 4b located inside the second slag 20. The first slag 4a may be a reducing slag based on ore-based iron sources (OBMs), and the second slag 4b may be an oxidizing slag based on scrap.

[0100] Even if the first slag 4a and the second slag 4b have different properties, they can be separated by the partition unit 400 and placed together in the double melting furnace F without being mixed. Furthermore, the different functions of the first slag 4a and the second slag 4b can be utilized simultaneously, improving the efficiency of the overall operation process.

[0101] The exhaust gas duct 500 may be arranged in the form of a duct outside the first upper cell 100 and the second upper cell 200 to connect the first upper cell 100 and the second upper cell 200 .

[0102] In other words, the exhaust gas duct 500 can connect 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. High-temperature exhaust gas generated from the first melting furnace 10 can be supplied to the second melting furnace 20 through the exhaust gas duct 500.

[0103] The bottom gas blowing device 600 may be disposed in the lower cell 300 to blow out gas. A plurality of bottom gas blowing devices 600 may be provided. For example, a plurality of bottom gas blowing devices 600 may be disposed in the overlapping lower cells 300 of the first melting furnace 10 and the second melting furnace 20.

[0104] The gas ejected from the bottom gas blowing device 600 can contain at least one of an inert gas and a heat source gas.

[0105] The bottom gas blowing device 600 can be used to control the flow of the molten metal 3 and to feed fuel, raw materials, etc. into the double melting furnace F. The bottom gas blowing device 600 can be provided with at least one gas inlet, and the type, size, number, position, etc. of the gas inlet can be variously changed as needed.

[0106] The tilting device 700 can tilt the electric furnace 1000, thereby discharging the molten metal 3, the first slag 4a, the second slag 4b, etc., from the inside to the outside.

[0107] The tilting device 700 may include a support cylinder 710 that maintains the center of the electric furnace 1000 and a drive cylinder 720 that can move up and down. A plurality of drive cylinders 720 may be provided. The electric furnace 1000 may be tilted in a direction intersecting the Z-axis direction via the support cylinders 710 and the drive cylinders 720.

[0108] The method for operating an electric furnace according to the present invention will be described below.

[0109] FIG. 3 is a flowchart of a method for operating an electric furnace according to one embodiment.

[0110] 4 to 9 are cross-sectional views showing the process steps of an electric furnace operating method according to one embodiment.

[0111] Referring to FIGS. 3 and 4, first, a method of operating an electric furnace 1000 according to an embodiment may include a step of melting a first iron source 1 and preheating a second iron source 2 (S01).

[0112] Specifically, the melting of the first iron source 1 may be carried out in a first melting furnace 10, and the preheating of the second iron source 2 may be carried out in a second melting furnace 20. The melting of the first iron source 1 and the preheating of the second iron source 2 may be carried out simultaneously.

[0113] The first melting furnace 10 can continuously receive and melt the first iron source 1 through a plurality of iron source supply units 120. The second melting furnace 20 can preheat the second iron source 2 while maintaining the foaming of the second slag 4b.

[0114] The second ferrous source 2 may be preheated using waste heat from an arc in at least one of the first melting furnace 10 and the second melting furnace 20. For example, waste heat generated in the first melting furnace 10 during the process of melting the first ferrous source 1 may be supplied to the second melting furnace 20 through the exhaust gas duct 500 together with exhaust gas, and the second ferrous source 2 may be preheated together with the waste heat from the second melting furnace 20.

[0115] The partition unit 400 can be lowered to the maximum extent to separate the first melting furnace 10 and the second melting furnace 20. In other words, the partition unit 400 can separate the first slug 4a and the second slug 4b.

[0116] In the step (S01) of melting the first iron source 1 and preheating the second iron source 2, the first electrode unit 110 may emit a first gas G1, and the second electrode unit 210 may emit a second gas G2.

[0117] The first gas G1 may include a reducing gas, and may include, but is not limited to, at least one selected from hydrogen (H2) gas and methane (CH4) gas.

[0118] The first iron source 1 may contain a large amount of iron oxide (FeO) and may be introduced into the first melting furnace 10. When the first electrode unit 110 emits the first gas G1, even if a large amount of iron oxide (FeO) is introduced, the iron oxide can be more easily reduced.

[0119] In addition, when an arc occurs at the first electrode unit 110, the reducing gas emitted from the first electrode unit 110 may be converted into plasma by arc heat. The activation energy of the reducing gas converted into plasma may be reduced, thereby improving the efficiency of the reduction reaction.

[0120] When the first gas G1 contains a reducing gas, the first electrode unit 110 may be at least partially immersed in the first slug 4a. The other end of the first electrode unit 110 in the Z-axis direction may be immersed in the first slug 4a.

[0121] Specifically, like the gas emission section EM (see FIG. 2) of the upper DC electrode 211 (see FIG. 2), the gas emission sections of the first to third AC electrode rods 111, 112, and 113 of the first electrode section 110 are immersed in the first slug 4a, and the first to third AC electrode rods 111, 112, and 113 can emit the first gas G1.

[0122] When the gas releasing portions of the first to third AC electrodes 111, 112, and 113 are not immersed in the first slug 4a but are located outside the first slug 4a, the first to third AC electrodes 111, 112, and 113 can release inert gas.

[0123] In this case, the first to third AC electrode rods 111, 112, and 113 are surrounded by an inert gas atmosphere, thereby performing a function of sealing the periphery of the area where an arc is generated.

[0124] That is, when the first to third AC electrode rods 111, 112, 113 emit inert gas, it is possible to suppress or prevent nitrogen (N2) in the atmosphere from being picked up by the molten metal 3 due to the arc flow.

[0125] The second gas G2 may include at least one selected from an inert gas and a reducing gas, and may include, but is not limited to, argon (Ar) gas and carbon dioxide (CO2) gas, or methane (CH4) gas.

[0126] While the first ferrous source 1 is being melted in the first melting furnace 10, impurities resulting from the melting of the first ferrous source 1 may flow into the second melting furnace 20. In this case, in the second melting furnace 20, oxidative refining of the impurities that have flowed in may be carried out using oxygen (O2).

[0127] The second gas G2 may contain a reducing gas to reduce iron oxide (FeO) produced by oxygen (O2) used in refining. The second gas G2 may further contain an inert gas to balance the oxidative refining by oxygen (O2) and the reduction of iron oxide (FeO) produced by the oxidative refining.

[0128] Continuing with reference to FIGS. 3, 5 and 6, the method for operating the electric furnace 1000 may include a step of melting a first iron source 1 and a second iron source 2 (S02).

[0129] Specifically, the melting of the first ferrous source 1 may proceed in a first melting furnace 10, and the melting of the second ferrous source 2 may proceed in a second melting furnace 20. The melting of the first ferrous source 1 and the melting of the second ferrous source 2 may proceed simultaneously. The melting of the first ferrous source 1 may proceed continuously while the second ferrous source 2 is being preheated and melted.

[0130] As the first ferrous source 1 in the first melting furnace 10 melts, the level of the molten metal 3 can rise from a first level (level 1.) to a second level (level 2.). When the raised water level (level 2.) reaches a level at which the second ferrous source 2 is completely immersed, the chamber door 222 can be opened and the second ferrous source 2 preheated in the preheating chamber 221 can be loaded.

[0131] The melting efficiency of the second iron source 2 can be improved by charging the preheated second iron source 2 at the level of the molten metal 3. In addition, the time that the second iron source 2 and the molten metal 3 are exposed to the second slag 4b can be minimized, so that the pickup of nitrogen (N) by the arc flow can be suppressed or prevented.

[0132] The partition unit 400 can be raised depending on the level of the molten metal 3. This allows 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 to be expanded.

[0133] As the flow channel expands, material and heat exchange can be more effectively performed, and the first electrode 110 of the first melting furnace 10 and the second electrode 210 of the second melting furnace 20 can also be raised by the increased level of the molten metal 3.

[0134] In the step S02 of melting the first iron source 1 and the second iron source 2, the first electrode unit 110 may emit a first gas G1. The second electrode unit 210 may emit a third gas G3 (see FIG. 5) or a fourth gas G4 (see FIG. 6), which are different from the first gas G1, depending on the step of charging the second iron source 2.

[0135] Specifically, the melting step of the second iron source 2 may include an initial charging step (see FIG. 5) and a later charging step (see FIG. 6) of the second iron source 2.

[0136] In the initial stage of charging the second iron source 2, the second slag 4b may be separated and dispersed by the second iron source 2 dropping from the preheating chamber 221. As a result, parts of the molten metal 3 and the second iron source 2 may be exposed and not covered by the second slag 4b.

[0137] Also, the upper DC electrode 211 may be exposed without being immersed in the second slag 4b and the molten metal 3. The other end and the tip of the upper DC electrode 211 in the Z-axis direction may be exposed. In this case, the gas discharge portion EM of the upper DC electrode 211 may be exposed without being immersed in the second slag 4b.

[0138] In this case, the second electrode unit 210 may emit a third gas G3. The third gas G3 may include an inert gas. For example, the inert gas may include argon (Ar) gas, but is not limited thereto.

[0139] By the second electrode unit 210 emitting the third gas G3, the pickup of nitrogen (N) by the arc flow generated by the second electrode unit 210 can be suppressed or prevented.

[0140] In other words, the second electrode unit 210 emits the third gas G3, so that the space between the upper DC electrode 211 and the molten metal 3 can be filled with the third gas G3 atmosphere. The area around where the arc is generated can be filled with the third gas G3 atmosphere.

[0141] The arc current generated between the upper DC electrode 211 and the lower DC electrode 212 can be sealed by the third gas G3.

[0142] This makes it possible to suppress or prevent nitrogen (N) from flowing into the molten metal 3 due to the arc flow even if the upper DC electrode 211, the second iron source 2, and the molten metal 3 are exposed and not immersed in the second slag 4b.

[0143] For a more detailed explanation, refer to FIG.

[0144] FIG. 10 is a graph showing the behavior of nitrogen at each stage of the electric furnace operation method.

[0145] 10, the graph in Fig. 10 has a horizontal axis and a vertical axis, where the horizontal axis represents the flow (time) of the electric furnace operation process, and the vertical axis represents the nitrogen content (%).

[0146] The graph in Figure 10 shows the behavior of nitrogen (N) when the iron source charged into the melting furnace contains scrap and direct reduced iron (DRI) and the ratio of scrap to direct reduced iron (DRI) is 1:4.

[0147] This can be applied to the operation process performed in the electric furnace 1000 of the present invention. However, this is just one example of the operation process that can be performed in the electric furnace 1000, and the present invention is not limited to this.

[0148] In the graph of FIG. 10, graph X indicates the case where the inert gas is not discharged from the electrode units 110 and 210, and graph Y indicates the case where the inert gas is discharged from the electrode units 110 and 210 and the arc flow is sealed.

[0149] The graph in FIG. 10 includes stages A, B, C, D, E, F, G, H and I according to the electric furnace operation process.

[0150] In step A, before melting the iron source in the melting furnace, the electrodes 110 and 210 are heated. In step A, the nitrogen content (%) of graphs X and Y is confirmed to be 0.0035%.

[0151] In stage B, the iron source is melted by the arc heat. In stage B, the nitrogen content (%) in graphs X and Y increases.

[0152] In the stage C, slags 4a and 4b are formed as the melting progresses. In the stage C, the nitrogen content (%) of graphs X and Y decreases.

[0153] In step D, the melting furnace is heated to prepare for the decarburization process. It can be seen that the nitrogen content (%) of graphs X and Y can be maintained in step D.

[0154] Stage E is the stage where the decarburization process progresses. At stage E, it can be seen that the nitrogen content (%) in graphs X and Y decreases.

[0155] In the F stage, a new iron source is added. In the F stage, it can be seen that the nitrogen content (%) of the X and Y graphs is maintained.

[0156] Stage G is the stage where steel is tapped. At stage G, it can be seen that the nitrogen content (%) in graphs X and Y increases.

[0157] Stage H is the stage where the tapped molten metal is stored. It can be seen that the nitrogen content (%) of graphs X and Y is maintained during Stage H.

[0158] In step I, the molten metal is cast. In step I, the nitrogen content (%) of graphs X and Y is increased.

[0159] It can be seen that the nitrogen content (%) in graph Y increases relatively less in stage B compared to graph X. That is, the inert gas is released from the electrode units 110 and 210, sealing the arc flow, thereby suppressing and preventing nitrogen (N) pickup in stage B.

[0160] In addition, if nitrogen (N) pickup is suppressed and prevented in step B, it can be seen that graph Y behaves as if it has a lower nitrogen content than graph X even if the subsequent processes are continuously carried out.

[0161] Referring again to FIGS. 3 and 6, in the later stage of charging when the second iron source 2 is completely immersed in the molten metal 3, the second electrode portion 210 can emit the fourth gas G4.

[0162] When the fourth gas G4 is released, the other end of the upper DC electrode 211 in the Z-axis direction and the other end can be immersed in the second slug 4b. That is, the gas release part EM of the upper DC electrode 211 can be immersed in the second slug 4b.

[0163] The fourth gas G4 may include at least one of an inert gas and a reducing gas, and the reducing gas may include at least one selected from carbon dioxide (CO2), hydrogen (H2), and methane (CH4).

[0164] For example, the fourth gas G4 may include argon (Ar) gas and carbon dioxide (CO2) gas, or may include methane (CH4) gas.

[0165] When the fourth gas G4 contains carbon dioxide (CO2) gas, the formation of the second slag 4b can be more smoothly carried out. When the fourth gas G4 contains methane (CH4) gas or hydrogen (H2) gas, the reduction of iron oxide (FeO) generated by oxygen used to dissolve the second iron source 2 can be more smoothly carried out.

[0166] In addition, when the fourth gas G4 further contains an inert gas, the balance between the dissolving performance and the reducing performance can be controlled by adjusting the concentration of the reducing gas.

[0167] Continuing with reference to FIGS. 3 and 7, the method for operating the electric furnace 1000 may include a step of adjusting the level of the first slag 4a (S03).

[0168] Specifically, in the first melting furnace 10, the upper door 11a of the first slag door 11 can be opened upward, thereby discharging the first slag 4a and adjusting the water level of the first slag 4a, thereby improving the efficiency of subsequent refining.

[0169] In the second melting furnace 20, the melting of the second iron source 2 charged into the molten metal 3 may continue, or preheating of a new second iron source 2 supplied to the preheat supply unit 220 may proceed.

[0170] In this case, the partition unit 400 may also be raised depending on the level of the molten metal 3. This may further expand 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.

[0171] The expansion of the flow channel can enhance material and heat exchange, and the first electrode 110 of the first melting furnace 10 and the second electrode 210 of the second melting furnace 20 can also rise due to the rising level of the molten metal 3.

[0172] Continuing with reference to FIGS. 3 and 8, the method for operating the electric furnace 1000 may include a step of mixing and refining the first slag 4a and the second slag 4b (S03).

[0173] Specifically, the partition unit 400 can be raised to the maximum extent to fully open the space between the first melting furnace 10 and the second melting furnace 20. As a result, the first slag 4a and the second slag 4b can be mixed and refined.

[0174] After adjusting the water level of the first slag 4a, which is a reducing slag, the first slag 4a and the second slag 4b are mixed, thereby improving refining efficiency. In addition, by raising the partition unit 400 to the maximum, an interface where a refining reaction can occur can be determined, thereby further improving refining efficiency.

[0175] After the first slag 4a and the second slag 4b are mixed, oxidative refining can be carried out using oxygen (O2), which can cause decarburization and dephosphorization reactions at high speed.

[0176] The first electrode unit 110 may emit a fifth gas G5, and the second electrode unit 210 may emit a sixth gas G6. Each of the fifth gas G5 and the sixth gas G6 may include a reducing gas.

[0177] The reducing gas may include, but is not limited to, at least one selected from carbon dioxide (CO2), methane (CH4), and hydrogen (H2). The fifth gas G5 and the sixth gas G6 may emit the same type of gas, but are not limited thereto.

[0178] The fifth gas G5 and the sixth gas G6 release reducing gases, which can reduce iron oxide (FeO) produced by oxygen (O2) used in oxidative refining. The concentrations of the reducing gases released by the fifth gas G5 and the sixth gas G6 can be adjusted taking into consideration the amount of oxygen (O2) input, refining capacity, reducing capacity, etc.

[0179] The fifth gas G5 and the sixth gas G6 release reducing gases, which allows both refining of the molten metal 3 and reduction of iron oxide (FeO) to proceed. In addition, by adjusting the concentration of the reducing gas, both the refining ability and the reducing ability can be adjusted, which can improve the efficiency of the process.

[0180] 4 to 8, material and heat exchange can proceed between the first melting furnace 10 and the second melting furnace 20 through the area not separated by the partition wall unit 400. As a result, the refining reaction can proceed continuously in the second melting furnace 20, and maximum refining capacity can be ensured when the partition wall unit 400 is raised to its maximum.

[0181] The first melting furnace 10 maintains the first slag 4a until the partition unit 400 reaches its maximum elevation and the first slag 4a and the second slag 4b are mixed together, thereby allowing the reduction of a large amount of iron oxide (FeO) introduced from the first iron source 1 to proceed.

[0182] Continuing with reference to FIGS. 3 and 9, the method for operating the electric furnace 1000 may include a step of tapping the molten metal 3 (S05).

[0183] Specifically, the double melting furnace F can be tilted by raising the drive cylinder 720 on the second melting furnace 20 side. The double melting furnace F can be tilted toward the first melting furnace 10 where the tapping hole 310 is formed.

[0184] This allows for smoother tapping of the molten metal 3 and / or slag 4 inside the first melting furnace 10 and the second melting furnace 20. Here, the slag 4 may refer to a mixture of the first slag 4a and the second slag 4b.

[0185] The preheat supply unit 220 may be formed in a form that can be separated from the remaining part of the second upper cell 200. In this case, the double melting furnace F may be tilted more smoothly.

[0186] The electric furnace 1000 includes a first melting furnace 10 and a second melting furnace 20 that melt different first and second iron sources 1 and 2, thereby ensuring productivity, economy, and quality and realizing carbon neutrality in steel production.

[0187] Ore-based ferrous metals (OBMs), low-grade scrap, and general scrap are fed into the melting furnaces 10 and 20 in parallel, and the respective slags 4a and 4b are separated, allowing the main raw materials to be melted and refined at the same time.

[0188] The operational impact of a large amount of gangue that can flow from ore-based iron sources (OBMs) can be separated and discharged in the first smelting furnace 10, making it possible to maintain and manage appropriate refining conditions. In addition, since a large amount of ore-based iron sources (OBMs) can be fed into the first smelting furnace 10, it is possible to reduce tramp components.

[0189] In addition, by feeding and operating scrap through the second melting furnace 20 connected to the first melting furnace 10, a complete flat bath operation may be possible.

[0190] Simultaneous operation of the first melting furnace 10 and the second melting furnace 20 and preheating of the second iron source 2 in the second melting furnace 20 can reduce energy consumption to below the level of general scrap operation and shorten operation to the level of a converter.

[0191] The first electrode unit 110 and the second electrode unit 210 release reducing gas to reduce the slags 4a and 4b, thereby improving the recovery rate of molten steel.

[0192] [Table 1]

[0193] In Table 1, Operation 1 indicates a case where the iron source melted in the melting furnace is 100% scrap, and Operation 2 indicates a case where the iron source melted in the melting furnace is composed of scrap and direct reduced iron (HBI). Operation 2 may be substantially the same as the operation of the electric furnace 1000 according to this embodiment.

[0194] The iron source used in the second operation includes scrap and direct reduced iron (HBI) in a ratio of 4:6, but the ratio of scrap to direct reduced iron (HBI) is not limited to this.

[0195] The contents described in Table 1 are merely examples of the first operation and the second operation, and the operations are not limited to these examples.

[0196] The charge amount for the first operation was 168.8 tons, the steel tapping amount was 152 tons, the burnt lime consumption rate was 18.2 kg / ton, the lightly burned consumption rate was 13.4 kg / ton, the CaO input amount was 3,029 kg, the total iron in the slag was 16.28%, and the theoretical amount of slag generated was 17,937 kg.

[0197] The charge amount for the second operation was 168.1 tons, the steel tapping amount was 149 tons, the burnt lime consumption rate was 28.2 kg / ton, the lightly burned consumption rate was 9.5 kg / ton, the CaO input amount was 3,940 kg, the total iron in the slag was 23.75%, and the theoretical amount of slag generated was 22,270 kg.

[0198] The molten steel recovery rate can be expressed by the following equation 1.

[0199] [Formula 1]

[0200] Molten steel recovery rate (%) = (tapped steel amount / charged steel amount) x 100 (%)

[0201] The molten steel recovery rate (%) can be calculated by dividing the tapped steel amount by the charged steel amount and multiplying the result by 100.

[0202] The molten steel recovery rate (%) of the first operation is (152 / 168.8) x 100 = 90.0%. The molten steel recovery rate (%) of the second operation is (149 / 168.1) x 100 = 88.6%. However, if reducing gas is released through the electrode parts 110, 210 to reduce the slags 4a, 4b, the molten steel recovery rate of the second operation can be improved.

[0203] The additional molten steel recovery rate of the second operation can be expressed by the following Equation 2.

[0204] [Formula 2]

[0205] Additional molten steel recovery rate (%) = (theoretical amount of slag generated (kg) x total amount of iron reduction) / charging amount (kg) x 100 (%)

[0206] The additional molten steel recovery rate (%) can be calculated by multiplying the theoretical amount of slag generated by the amount of total iron lost, dividing the result by the charged amount, and multiplying the result by 100.

[0207] The slags 4a and 4b may be reduced by the reducing gas released through the electrode units 110 and 210, and the total iron in the slags 4a and 4b may be reduced.

[0208] For example, if the total iron in the second run is reduced to 16.28%, which is the value of the total iron in the first run, the reduction in total iron in Equation 2 is 23.75%-16.28%=7.47%.

[0209] In this case, the additional molten steel recovery rate for the second operation is (22,270 (kg) x 7.47 (%)) / 168,100 (kg) = 0.98 (%).

[0210] For the second operation, the total molten steel recovery rate is 88.6% + 0.98% = 89.58%.

[0211] The slags 4a and 4b are reduced by the reducing gas released through the electrodes 110 and 210, so that even when scrap and direct reduced iron are used as the iron source, a molten steel recovery rate equivalent to that of an operation using only scrap can be ensured.

[0212] Furthermore, in the case of the second operation, the amount of scrap input is smaller than in the first operation, so high-quality molten steel with a significantly lower content of tramp elements can be produced.

[0213] Other embodiments will be described below. In the following embodiments, the same configurations as those already described will be omitted or simplified, and differences will be mainly described.

[0214] Fig. 11 is a flow chart of a method for operating an electric furnace according to another embodiment, and Figs. 12 and 13 are cross-sectional views of the process steps of the method for operating an electric furnace according to the embodiment of Fig. 11.

[0215] 11 and 12, an electric furnace 1000_1 according to another embodiment differs from the first embodiment in that it is configured as a single melting furnace instead of a double melting furnace F (see FIG. 1).

[0216] In addition, the operating method of the electric furnace 1000_1 according to the other embodiment differs from the first embodiment in that it includes a step of charging the iron source 1_1 (S01_1), a step of melting the iron source 1_1 (S02_1), a step of refining (S03_1), and a step of tapping (S04_1).

[0217] Specifically, the electric furnace 1000_1 may include an upper cell 100_1, a lower cell 300_1, a melting furnace 10_1 configured with the upper cell 100_1 and the lower cell 300_1, and an electrode unit 110_1.

[0218] The electrode unit 110_1 includes first to third AC electrode rods 111_1, 112_1, and 113_1, which are respectively connected to first to third gas supply pipes GP1, GP2, and GP3, and can receive a plurality of types of gases from a gas storage tank GS.

[0219] In step S01_1 of introducing the iron source 1_1, the iron source 1_1 is introduced into the melting furnace 10_1. The iron source 1_1 may include, but is not limited to, scrap. The iron source 1_1 may fill the entire volume of the melting furnace 10_1.

[0220] In the step S02_1 of melting the iron source 1_1, the electrode unit 110_1 may receive power to generate arc heat, and the iron source 1_1 may be melted in the melting furnace 10_1 by the generated arc heat.

[0221] The electrode unit 110_1 may emit a seventh gas G7. The seventh gas G7 may include an inert gas, such as, but not limited to, argon (Ar) gas.

[0222] The electrode portion 110_1 may be exposed without being immersed in the slag 4_1 and the molten metal 3_1. The other end and the other end of the electrode portion 110_1 in the Z-axis direction may be exposed. In this case, the gas discharge portion EM (see FIG. 2) of the electrode portion 110_1 may be exposed without being immersed in the slag 4_1.

[0223] By discharging the seventh gas G7 from the electrode unit 110_1, an inert gas atmosphere can be created around the electrode unit 110_1. As a result, even if arcing occurs at the electrode unit 110_1, the area where the arc occurs is created in an inert gas atmosphere, thereby suppressing or preventing a nitrogen (N) pickup phenomenon.

[0224] 11 and 13, an iron source 1_1 (see FIG. 12) may be melted to form molten metal 3_1 and slag 4_1. The periphery where an arc is generated at the electrode portion 110_1 may be sealed by the molten metal 3_1.

[0225] In the refining step (S03_1), oxygen is blown into the melting furnace 10_1 to oxidize and refine the molten metal 3_1.

[0226] The electrode unit 110_1 may emit an eighth gas G8. The eighth gas G8 may include a reducing gas. The reducing gas may include, but is not limited to, at least one selected from carbon dioxide (CO2) gas, hydrogen (H2) gas, and methane (CH4) gas.

[0227] At least a portion of the electrode portion 110_1 can be immersed in the slug 4_1. The other end and the other end of the electrode portion 110_1 in the Z-axis direction can be immersed in the slug 4_1. In this case, the gas discharge portion EM (see FIG. 2) of the electrode portion 110_1 can be immersed in the slug 4_1.

[0228] By discharging the eighth gas G8 from the electrode unit 110_1, iron oxide (FeO) generated by oxidation refining can be reduced. The reducing gas can be converted into plasma, which can improve the efficiency of the reduction reaction. This can improve the efficiency of the entire operation process.

[0229] In the tapping step (S04_1), if the conditions of the molten metal 3_1 correspond to the target conditions, the molten metal 3_1 can be tapped from the electric furnace 1000_1 by a transfer means.

[0230] In this case, different gases are released from the electrode unit 110_1 at different operation stages, thereby improving the efficiency of operation and the productivity of products.

[0231] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art will understand that the present invention may be embodied in other specific forms without changing the technical spirit or essential features thereof. Therefore, the above-described embodiments should be understood as illustrative in all respects and not restrictive. [Explanation of symbols]

[0232] 1:First iron source 2:Second iron source 3: Molten metal 4: Slag 10:First melting furnace 20:Second melting furnace 100: First upper cell 110:First electrode part 200: Second upper cell 210:Second electrode part 220: Preheat supply section 300: Lower cell 400: Partition unit 500: Exhaust gas duct 600: Bottom gas blower 700:Tilt device 1000: Electric furnace

Claims

1. Melting a first iron source in a first melting furnace having a first electrode unit disposed therein; Preheating a second iron source in a second melting furnace in which a second electrode unit is disposed; and melting the second iron source in the second melting furnace; The first melting furnace and the second melting furnace share an internal space, In the step of preheating the second iron source, the second electrode unit emits a first gas; a second electrode unit that emits a second gas different from the first gas during the melting of the second iron source;

2. 2. The method for operating an electric furnace according to claim 1, wherein the first gas includes a reducing gas, and the second gas includes an inert gas.

3. The reducing gas is carbon dioxide (CO ２ ) gas, methane (CH ４ ) gas and hydrogen (H ２ ) gases, 3. The method for operating an electric furnace according to claim 2, wherein the inert gas includes argon (Ar) gas.

4. 3. The method of operating an electric furnace according to claim 2, wherein the first gas further includes an inert gas.

5. The step of dissolving the second iron source includes an initial dissolution stage and a later dissolution stage, In the initial stage of dissolution, the second electrode portion releases the second gas, 2. The method of claim 1, wherein the second electrode unit emits a third gas different from the second gas in the later melting stage.

6. 6. The method for operating an electric furnace according to claim 5, wherein the second gas includes an inert gas, and the third gas includes a reducing gas.

7. In the initial stage of dissolution, the second electrode portion is exposed to the outside, 7. The method of claim 6, wherein the second electrode is at least partially immersed in the slag during the later melting stage.

8. 2. The method of claim 1, wherein the step of melting the first iron source is performed simultaneously with the steps of preheating the second iron source and melting the second iron source.

9. 9. The method of claim 8, wherein the first electrode unit emits a third gas during the melting of the first iron source.

10. 10. The method for operating an electric furnace according to claim 9, wherein the third gas includes a reducing gas.

11. The method further includes the step of refining molten metal by mixing the first slag in the first melting furnace and the second slag in the second melting furnace, In the step of refining the molten metal, the first electrode unit emits a third gas and the second electrode unit emits a fourth gas; 2. The method for operating an electric furnace according to claim 1, wherein the third gas and the fourth gas include a reducing gas.

12. the first electrode unit includes a first AC electrode, a second AC electrode, and a third AC electrode, 2. The method of claim 1, wherein the second electrode unit includes an upper DC electrode and a lower DC electrode.

13. The upper DC electrode is an inner tube defined by passing through the upper DC electrode in a longitudinal direction, through which at least one of the first gas and the second gas can flow; a gas supply unit located on one side of the inner pipe and supplying at least one of the first gas and the second gas; and 13. The method of claim 12, further comprising a gas discharge part located on the other side of the inner tube through which at least one of the first gas and the second gas is discharged.

14. 13. The method of claim 12, wherein the first iron source comprises an ore-based iron source and the second iron source comprises scrap.

15. A step of charging an iron source into an electric furnace including an electrode portion; applying power to the electrode portion to melt the iron source; and a step of introducing oxygen into the electric furnace to perform refining; In the step of melting the iron source, the electrode unit emits a first gas; 2. The method for operating an electric furnace, wherein, in the refining step, the electrode unit emits a second gas different from the first gas.

16. 16. The method of operating an electric furnace according to claim 15, wherein the first gas includes an inert gas, and the second gas includes a reducing gas.

17. 16. The method for operating an electric furnace according to claim 15, wherein the electrode unit includes a first AC electrode, a second AC electrode, and a third AC electrode.

18. 18. The method of claim 17, wherein each of the first AC electrode rod, the second AC electrode rod, and the third AC electrode rod emits at least one of the first gas and the second gas from inside thereof.

19. A method for operating an electric furnace including an electrode rod and defining a space therein for accommodating at least one of an iron source, molten iron, and slag, comprising: The electrode rod emits a first gas comprising an inert gas; and the electrode rod emits a second gas containing a reducing gas; In the step of discharging the first gas, one end of the electrode rod is exposed, 4. The method for operating an electric furnace, wherein the one end of the electrode rod is positioned inside the slag during the second gas release step.

20. The electrode rod is an inner tube through which the first gas and the second gas flow; and a gas discharge part located on one side of the inner tube and discharging the first gas and the second gas; 20. The method of claim 19, wherein the gas discharge portion is disposed at the tip of the one side of the electrode rod.

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