A system for producing green steel with very low GHG emission intensity using an electric arc furnace.

Abstract

This provides a method for producing green steel using environmentally sustainable and energy-efficient processes. [Solution] This method 100 includes the step of obtaining scrap containing different types of scrap alloys other than pig iron and DRI from one or more scrap sources. The obtained scrap is charged into an electric furnace, preferably an electric arc furnace (EAF), and melted in the presence of a controlled oxygen supply. The oxygen supply is regulated using one or more control means to ensure a precise metallurgical reaction. The molten steel obtained from the electric arc furnace is transferred to a smelting furnace for refining and adjustment of its chemical composition. The refined molten steel is transferred to a vacuum smelting unit and then to a casting area for the solidification of green steel.

Description

Technical Field

[0004] , ,

[0001] Embodiments of the present disclosure generally relate to the metallurgical field. More specifically, the present disclosure relates to a system and method including an improved melting step by an electric arc furnace (hereinafter referred to as "EAF" in this specification) for producing environmentally friendly, i.e., low carbon emission, green steel that contributes to the decarbonization of the steel industry. Throughout this specification, the term "green steel" can be understood to refer to steel produced using an environmentally friendly and sustainable method that includes the use of electricity generated from renewable energy sources, reduction of carbon dioxide emissions, and minimization and recycling of waste during the manufacturing process.

Background Art

[0002] The description of the background art includes information that may be useful in understanding the present disclosure.

[0003] Steel is a basic material in the modern world and plays an important role in supporting the development of the world economy. With the increasing demand for steel, especially in emerging economies such as India, steel manufacturing has to meet growing needs while addressing environmental issues. Currently, India, the world's second-largest steel producer, aims to achieve a production capacity of 300 million tons by 2030. However, the steel sector is also one of the largest contributors to the world's greenhouse gas (GHG) emissions, accounting for about 7 - 9% of the world's emissions, and India accounts for 12% of those emissions.

[0004] Conventional steelmaking processes, especially the blast furnace (BF)-basic oxygen furnace (BOF) route, are highly emission-intensive and rely on iron ore as the main raw material. In contrast, the electric arc furnace (EAF) route uses metal scrap as the main raw material and may have a lower carbon footprint. However, even with this more sustainable approach, the EAF route still produces significant GHG emissions, mainly due to energy consumption, variations in scrap quality, and the oxygen-intensive nature of the refining process.

[0005] Green steel, or steel with low GHG emissions, is a key objective in the steel industry's ongoing efforts toward decarbonization. Various strategies have been developed to minimize emissions during the steel production process, including increased use of metal scrap, utilization of renewable energy sources, and improved furnace energy efficiency. The EAF route, in particular, when combined with technological advancements such as electric vehicles (EVs) for controlled oxygen supply and scrap transport, is a promising clean way to produce steel.

[0006] Furthermore, conventional steelmaking processes are characterized as some of the most emission-intensive processes. These processes include steelmaking via the blast furnace (BF)-basic oxygen converter (BOF) route, the electric arc furnace route (EAF), and the induction furnace (IF) route. In the BF-BOF route, steel is produced from iron ore, while in the EAF route, 100% scrap or a mixture of scrap and DRI / pig iron is used. Total GHG emissions vary depending on the different input raw materials used for melting. In recent years, several melting routes related to steelmaking have been used to produce steel.

[0007] Prior art discloses several methods related to steelmaking, with a particular focus on improving the efficiency of scrap utilization in EAFs.

[0008] Prior art document U.S. Patent No. 9,045,810 describes a method for melting steel in an electric arc furnace using a “hot heel,” which is a mass of molten metal held from a previous operation. The hot heel helps maintain the temperature required to melt new scrap metal, potentially optimizing the process and reducing energy consumption. The method stipulates that the hot heel must be at least 0.75 times the ratio of the heat required to melt the scrap to the heat obtained from the hot heel.

[0009] U.S. Patent No. 3,955,964 (May 11, 1976) describes a method for producing steel in an electric arc furnace using a molten charge made from high-carbon iron metal containing less than 3% carbon, 0.2% silicon, and 0.2% manganese, heated to at least 1375°C. Solid metal charges, including steel scrap, hot briquetted iron, direct reduced iron, and iron ore, are added to form the charge mixture. The molten steel is then superheated, finished, and poured into a ladle for casting while maintaining its chemical composition and purity.

[0010] U.S. Patent No. 6,162,274 (December 11, 2000) outlines a two-stage steelmaking process in a submerged electric arc furnace, in which reduced iron pellets are first charged to produce molten iron, and then this molten iron is used to efficiently melt a second portion of the pellets to produce steel. This process emphasizes maintaining a specific weight ratio (30-70%) of the first and second pellet portions to optimize melting and ensure the output of high-quality steel.

[0011] Chinese Patent No. 104962800 relates to a method for smelting stainless steel, including electric arc furnace (EAF) smelting, primary smelting in a low-frequency (LF) furnace, vacuum oxygen decarburization (VOD) furnace smelting, and resmelting in an LF furnace. This method addresses the challenges of improving the quality of molten steel, reducing production costs, and smelting various types of molten steel in a single EAF.

[0012] Chinese Patent No. 102787195 describes a stainless steel smelting method using an ultra-high-power electric arc furnace with an eccentric bottom for direct iron reduction, a large-flow furnace wall cluster coal oxide gun, and refining by an AOD furnace and a VOD furnace before continuous casting.

[0013] The prior art described above focuses on conventional steelmaking methods that involve higher GHG emissions than the proposed new process. The proposed method aims to address GHG emission reductions that remain unaddressed through conventional routes.

[0014] Therefore, in the field of the art, there is a pressing need to provide systems and methods for producing green steel using an improved melting step with low-carbon emissions EAF. [Overview of the Initiative] [Problems that the invention aims to solve]

[0015] Some of the objectives of this disclosure that at least one embodiment satisfies in this specification are listed below in this specification.

[0016] The overall objective of this disclosure is to provide a system and method for producing green steel in an environmentally friendly manner that reduces GHG emissions.

[0017] Another object of this disclosure is to improve electric arc furnace (EAF) steelmaking processes by integrating controlled oxygen supply, increasing process energy efficiency, and utilizing electric vehicles for scrap transport.

[0018] Another object of this disclosure is to reduce the environmental impact of steel production by optimizing the use of metal scrap from various sources, including industrial scrap, manufacturing scrap, and post-consumer scrap, thereby providing a system to minimize the need for primary raw materials and reduce emissions associated with iron ore extraction.

[0019] Another object of this disclosure is to provide a method that enables the sorting and selection of scrap to secure specific metal combinations, thereby optimizing the composition of the steel produced and improving the overall quality of the final product, i.e., green steel.

[0020] Various objects, features, aspects, and advantages of the subject matter of the present invention will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawings in which similar figures represent similar components. [Means for solving the problem]

[0021] Within the scope of this application, it is expressly assumed that the various aspects, embodiments, examples, and alternatives described in the preceding paragraphs, claims, and / or the following description and drawings, in particular their individual features, may be used independently or in any combination. Features described in relation to one embodiment are applicable to all embodiments unless such features are incompatible.

[0022] One aspect of the present disclosure provides a method for producing green steel with minimal greenhouse gas emissions. The method comprises a first step of obtaining scrap (scarp) from one or more sources, the scrap comprising various types of scrap alloys. The scrap is charged into an electric furnace and melted in the presence of a controlled oxygen supply to obtain molten steel. The molten steel is transferred to a smelting furnace, further refined under vacuum for refining and degassing, and then sent to a casting area to produce green steel.

[0023] In another aspect of this disclosure, scrap is transported using an electric vehicle and sorted to achieve a specific combination of metals. The scrap may include industrial scrap, manufacturing scrap, waste scrap, post-consumer scrap, process scrap, carbon steel scrap, stainless steel scrap, alloy steel scrap, non-ferrous scrap, electronic equipment scrap, or high-alloy scrap. The oxygen supply is regulated using control means such as an oxygen lance, flow control valve, flow meter, calculation system, or oxygen purity control system.

[0024] In yet another aspect of the present disclosure, the method includes the step of mixing a refining agent within an electric arc furnace to form a slag. The refining agent can include lime, fluorite, dolomite, or a synthetic slag material. Lime is a basic flux and helps remove acidic impurities such as phosphorus and sulfur. Fluorite (CaF2) acts as a flux to lower the melting point of the slag, improve its fluidity, and facilitate the removal of impurities. Dolomite (CaMg(CO3)2) is a double carbonate of calcium and magnesium. It supplies both calcium and magnesium oxides during melting. Aluminum acts as a deoxidizer and reacts with dissolved oxygen to reduce its content in the molten steel. Silica contributes to slag formation but is typically used in an acidic slag environment. Synthetic slag is a pre-mixed combination of fluxes (such as lime, fluorite, alumina, etc.) tailored to specific refining needs.

[0025] In yet another aspect, the method includes the steps of refining molten steel in a refining furnace, alloying with ferroalloys and alloys, and degassing the refined steel using a device that adjusts the additions to the molten steel (trimming additions) to achieve the desired chemical composition. The degassed steel is then transferred to the casting area.

[0026] In yet another aspect, the power sources for the charging, melting, refining, and vacuum degassing operations are generated from renewable energy sources. The vacuum within the vacuum refining apparatus is formed using electrical power generated from renewable energy sources and biodiesel.

Brief Description of the Drawings

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the disclosed methods and systems, and like reference numerals refer to the same parts throughout the different drawings. The components in the drawings are not necessarily to scale, and instead, emphasis is placed on clearly illustrating the principles of the present disclosure. Some of the drawings may show components using block diagrams and may not represent the internal circuits of each component. It will be understood by those skilled in the art that the disclosure of such drawings includes the disclosure of electrical components, electronic components, or circuits commonly used for implementing such components.

[0028] [Figure 1] An exemplary flowchart of a method for manufacturing green steel with an improved melting step according to an exemplary embodiment of the present disclosure is shown. [Figure 2] An exemplary block diagram of a system for manufacturing green steel according to an exemplary embodiment of the present disclosure is shown. [Figure 3] An exemplary flowchart representing the overall process of manufacturing green steel according to an embodiment of the present disclosure is shown.

[0029] Other objects, advantages, and novel features of the present disclosure will become apparent from the following detailed description of the embodiments when considered in conjunction with the accompanying drawings.

Best Mode for Carrying Out the Invention

[0030] Here, various exemplary embodiments will be described in more detail with reference to the accompanying drawings, which show only some exemplary embodiments. The specific structural and functional details disclosed herein are merely representative for explaining the exemplary embodiments. However, the present disclosure can be embodied in many alternative forms and should not be construed as limited to only the exemplary embodiments described herein.

[0031] The following is a detailed description of embodiments of the present disclosure shown in the accompanying drawings. The embodiments are described in detail to clearly convey the present disclosure. However, the amount of detail provided is not intended to limit anticipated variations of the embodiments, but rather to cover all modifications, equivalents, and substitutions that fall within the spirit and scope of the present disclosure as defined by the accompanying claims.

[0032] In this specification, exemplary embodiments of the present disclosure will be described below with reference to Figures 1 to 3 of the accompanying drawings.

[0033] Figure 1 shows an exemplary flowchart (100) of a method (100) for producing green steel (600) with an improved melting step, according to an exemplary embodiment of the present disclosure.

[0034] In one embodiment of the present disclosure, a method (100) for producing green steel (600) while minimizing greenhouse gas emissions and optimizing the use of renewable energy sources is disclosed.

[0035] In block 101, method (100) includes the step of obtaining scrap (201) from one or more scrap sources (700). The scrap (201) includes, but is not limited to, different types of scrap alloys (202). The one or more scrap sources (700) may include, but is not limited to, industrial scrap, manufacturing scrap, waste scrap, post-consumer scrap, process scrap, carbon steel scrap, stainless steel scrap, alloy steel scrap, non-ferrous scrap, electronic equipment scrap, or high-alloy scrap. The scrap (201) is transported using an electric vehicle to reduce the environmental impact.

[0036] In block 102, method (100) includes step (102) of charging the obtained scrap (201) into an electric arc furnace (203). In a preferred embodiment, the electric furnace (203) is an electric arc furnace (EAF), which is an energy-efficient device for melting metal scrap. The scrap (201) is separated to obtain a specific combination of metals and then charged into the electric arc furnace (203). The obtained scrap (201) is preferably divided into different types of scrap alloys (202) from which pig iron and directly reduced iron (DRI) are removed for low GHG emissions.

[0037] Block 103 includes melting (103) charged scrap (201) generated in an electric arc furnace (203) to produce molten steel (204). During the melting (103) process, a controlled oxygen supply is provided to the electric arc furnace (203) using one or more control means (205).

[0038] In such embodiments, the control means (205) may include, but are not limited to, an oxygen lance, one or more flow control valves, one or more flow controllers, a computational control system, or an oxygen purity control mechanism. The controlled oxygen supply ensures precise metallurgical reactions such as dephosphorization and carbon control, thereby improving the quality of the molten steel (204). In these embodiments, dephosphorization is the removal of phosphorus from the molten steel. Phosphorus is an undesirable impurity because it can make steel brittle. This reaction occurs by forming phosphorus oxide, which is absorbed into the slag.

[0039] In block 104, the molten steel (204) is transferred from the electric arc furnace (203) to the smelting furnace (207) for further processing (104). The smelting furnace (207) refines the molten steel (204) by removing impurities and adjusting its chemical composition (105). During the refining (105), one or more refining agents are added to the molten steel (204). These refining agents may include, but are not limited to, lime (CaO), fluorite (CaF2), dolomite (CaMg(CO3)2), or synthetic slag materials. The addition of refining agents promotes slag formation, which reacts with the molten steel (204) in a slag-metal reaction. The slag-metal reaction may include, but is not limited to, desulfurization, deoxidation, and inclusion removal. This reaction refines the molten steel (204) and ensures that the refined steel meets the desired specifications.

[0040] In such embodiments, refining may include, but is not limited to, slag-metal reactions including desulfurization, deoxidation, and inclusion removal. Desulfurization removes sulfur, another impurity that can adversely affect the ductility and weldability of the steel. Sulfur reacts with calcium or magnesium-based refining agents (such as CaO or CaF2) to form calcium sulfide (CaS) or other stable sulfur compounds, which migrate into the slag. The deoxidation process reduces dissolved oxygen in the molten steel to prevent defects such as gas voids and inclusions. Deoxidizing agents such as silicon (Si), aluminum (Al), or manganese (Mn) are added to the molten steel. These elements react with oxygen to form stable oxides (e.g., SiO2, Al2O3, MnO), which float to the slag layer and are removed. Nonmetallic inclusions such as oxides and sulfides can impair the mechanical properties of the steel. Inclusions are captured and absorbed by the slag. The use of refining agents such as synthetic slag efficiently binds inclusions, ensuring that cleaner steel with good surface quality and structural integrity is obtained. After the refining (105) step, the molten steel (204) is subjected to degassing (107) in a vacuum refining unit (208). The vacuum refining unit (208) removes dissolved gases such as hydrogen, nitrogen, or oxygen from the refined molten steel (204). High levels of gas can lead to defects such as hydrogen-induced cracking or flakes. During the vacuum oxygen decarburization process, the carbon content in the molten steel is controlled and reduced under vacuum to meet specific compositional requirements. Carbon reacts with oxygen to form carbon monoxide (CO) or carbon dioxide (CO2), which leach from the molten steel (204). This reaction is facilitated under oxidizing conditions to produce low-carbon or ultra-low-carbon stainless steel. The degassing (107) step ensures that the refined steel exhibits excellent mechanical and chemical properties. After degassing (107), the refined steel is transferred to the casting area (206) for solidification and shaping.

[0041] Method (100) further includes the step of adjusting the addition of ferroalloys to molten steel (204) by adding one or more ferroalloys or alloying elements (106) to achieve a predetermined chemical composition of the refined steel. In such embodiments, the ferroalloys and alloying elements used in adjustment (106) may include, but are not limited to, silicon, aluminum, carbon, niobium, boron, tungsten, copper, manganese, chromium, nickel, molybdenum, vanadium, titanium, or cobalt. The adjustment (106) step ensures that the green steel (600) meets specific mechanical, chemical, and physical requirements.

[0042] The casting area (206) includes one or more molds for shaping the vacuum-refined steel into a desired form. In addition, the casting area (206) includes, but is not limited to, a cooling system (206-1) for accelerating the solidification of the molten steel. The cooling system (206-1) ensures uniform cooling and minimizes internal defects in the solidified steel.

[0043] In exemplary embodiments of the embodiments, the green steel (600) produced in the casting area (206) may include, but is not limited to, low carbon steel, medium carbon steel, high carbon steel, high-strength low-alloy (HSLA) steel, low-alloy steel, high-alloy steel, microalloy steel, stainless steel, iron (Fe)-based superalloy steel, tool steel, die steel, or valve steel.

[0044] In exemplary embodiments of the embodiment, method (100) utilizes a power source (111), which is electricity generated from a renewable energy source. In such embodiments, the renewable energy source may include, but is not limited to, solar, wind, or hydroelectric power. The power source (111) is used to operate an electric arc furnace (203), a smelting furnace (207), a vacuum smelting unit (208), and a casting area (206), thereby reducing the carbon footprint of the entire process. In addition, the vacuum smelting unit (208) can use the power source (111) to create a vacuum for its operation. The vacuum is created using one or more boiler operations. One or more boiler operations may include, but is not limited to, steam ejector operation, barometric condenser operation, mechanical booster, steam combination, thermocompressor operation, or steam turbine-driven vacuum pump.

[0045] In exemplary embodiments of the embodiments, metal scrap is metal waste generated from industrial processes, manufacturing, construction, and used products, and is recyclable.

[0046] In exemplary embodiments of the embodiment, Method (100) ensures that the manufacturing process incorporates environmentally sustainable practices. By using electricity generated from renewable energy sources, electric vehicles, and efficient furnaces, Method (100) minimizes greenhouse gas emissions. Green steel (600) produced through Method (100) is suitable for a wide range of applications, including, but not limited to, construction, automotive, energy, bearings, general engineering applications, nuclear, oil and gas, tools and molds, defense, chemical industry applications, and aerospace. In exemplary embodiments of the embodiment, one or more charging mechanisms are used to charge the resulting scrap (201). The charging mechanisms may include, but are not limited to, cranes, hoists, charging buckets, or vibratory feeders.

[0047] In this embodiment, sensors positioned inside and around the EAF(203) continuously or discretely measure variables such as temperature, oxygen flow rate, and metal temperature. An in-house developed model analyzes the data, and the oxygen supply within the EAF is adjusted accordingly.

[0048] In summary, the disclosed method (100) includes an improved melting step in which the use of oxygen is controlled. The method first begins with the transport of scrap (201) and raw materials by zero-emission vehicles such as battery-operated forklifts and trucks. The resulting scrap (201) includes different types of scrap alloys (202) encompassing all kinds of iron alloys. Method (100) limits the use of oxygen and supplies a calculated amount of oxygen necessary for dephosphorization. Method (100) strategically excludes the use of pig iron in the scrap (201) charged into the EAF (203) and uses scrap (201) that is suitable for the chemical properties of the alloy to be produced. Generally, the scrap (201) charged (i.e., input to the EAF) includes pig iron (20-25%), heavy molten scrap (50-60%), DRI (8-10%), factory return scrap (5-8%), and machining chip scrap (5-8%). Pig iron is composed of approximately 4% carbon, which is reduced by the injection of oxygen to form CO and CO2, contributing to GHG emissions. Adding DRI increases the phosphorus concentration. Since phosphorus is an impurity, the addition of oxygen is necessary to refine the impurity. Therefore, the amount of oxygen used in EAF(203) increases. For this reason, the use of DRI and pig iron is prohibited. This method further includes steps of ladle refining and vacuum degassing, as well as adjustments to the addition of ferroalloys, in order to keep GHG emissions very low. The electricity required for melting in EAF and LF furnaces, vacuum refining equipment, and casting of alloys produced therefrom is generated by renewable energy sources such as solar power. Vacuum is generated for VD and VOD, which use biodiesel for boiler operation. Therefore, this method (100) is a cost-effective way to produce green steel (600) with very low GHG emissions.

[0049] Figure 2 shows an exemplary block diagram (200) of a system (200) for manufacturing green steel (600) according to an exemplary embodiment of the present disclosure.

[0050] Another embodiment of the present disclosure discloses a system (200) for producing green steel (600) in an environmentally sustainable manner while optimizing energy efficiency and material use. The system (200) includes an electric furnace (203) (hereinafter used interchangeably with the terms “electric arc furnace” and “EAF”) designed to melt scrap (201). The scrap (201) is obtained from one or more scrap sources (700) and comprises different types of scrap alloys (202). The types of scrap alloys (202) may include, but are not limited to, industrial scrap, manufacturing scrap, waste scrap, post-consumer scrap, process scrap, carbon steel scrap, stainless steel scrap, alloy steel scrap, non-ferrous scrap, electronic equipment scrap, or high-alloy scrap. The scrap (201) is transported to the EAF (203) using an electric vehicle powered by a renewable energy source to minimize greenhouse gas emissions. Next, the scrap (201) is separated to obtain specific combinations of metals necessary for further processing.

[0051] The system (200) includes a melting means (209) that facilitates the melting of the charged scrap (201) within the EAF (203). The melting process is carried out in the presence of a controlled oxygen supply to achieve the precise metallurgical reaction required for the production of molten steel (204). The controlled oxygen supply is carried out using one or more control means (205).

[0052] In exemplary embodiments of the embodiment, the control means (205) may include, but are not limited to, an oxygen lance, one or more flow control valves, one or more flow controllers, a computational control system, or an oxygen purity control mechanism. The controlled oxygen supply ensures efficient reactions such as dephosphorization and carbon removal, thereby improving the quality of the molten steel (204).

[0053] In yet another embodiment of the present disclosure, the system (200) integrates an in-house developed model to monitor data and adjust the oxygen supply in real time accordingly.

[0054] The system (200) further includes a transfer means (210) for transferring molten steel (204) from the EAF (203) to a smelting furnace (207). The smelting furnace (207) is connected to the EAF (203) and is used to smelt the molten steel (204) by removing impurities and adjusting its chemical composition. During the smelting process, one or more refining agents are added to facilitate the slag-metal reaction.

[0055] In exemplary embodiments of the embodiments, the refining agent may include, but is not limited to, lime (CaO), fluorite (CaF2), dolomite (CaMg(CO3)2), or synthetic slag material. The slag-metal reaction may include, but is not limited to, desulfurization, deoxidation, and inclusion removal.

[0056] After the step in the refining unit (207), the molten steel (204) is fed to the vacuum refining unit (208). The vacuum refining unit (208) removes dissolved gases such as hydrogen, nitrogen, or oxygen from the refined steel. These reactions purify the molten steel (204) and ensure that the refined steel meets the desired specifications.

[0057] In an exemplary embodiment of the embodiment, the refined molten steel (204) is transferred to a casting area (206) for solidification and shaping. The casting area (206) comprises one or more molds for shaping the refined steel into a desired form. The casting area (206) also includes a cooling system (206-1) that promotes uniform solidification of the molten steel, reduces internal defects, and ensures excellent structural integrity. The green steel (600) produced in the casting area (206) may include, but is not limited to, low-carbon steel, medium-carbon steel, high-carbon steel, high-strength low-alloy (HSLA) steel, low-alloy steel, micro-alloy steel, high-alloy steel, stainless steel, iron (Fe)-based superalloy steel, tool steel, die steel, or valve steel.

[0058] The power required to operate System (200) is supplied by electricity generated from renewable energy sources such as solar, wind, or hydroelectric power. The use of renewable energy sources minimizes the carbon footprint of System (200) and aligns with environmental sustainability goals.

[0059] In summary, by employing innovative technologies and sustainable practices, the disclosed system (200) addresses the need for a more environmentally friendly method of producing steel. Green steel (600) produced by system (200) is suitable for a wide range of applications across industries such as construction, automotive, energy, bearings, general engineering applications, nuclear power, oil and gas, tools and molds, defense and aerospace, and chemicals.

[0060] Figure 3 shows an exemplary flow chart (300) illustrating the overall process for manufacturing green steel (600) according to one embodiment of the present disclosure.

[0061] Referring to Figure 3, the obtained scrap (201) is strategically selected to have little or no ferroalloy additive and is transported using an electric vehicle in step 301. Further charging of the scrap at the EAF is carried out using a crane powered by electricity generated from a renewable energy source, and lime is added in step 302 for slag production. After charging, primary melting is carried out in an electric furnace (203), where oxygen use is carefully controlled, and only the amount of oxygen necessary for dephosphorization is supplied in step 303. The melting of the charged scrap (201) is carried out using electricity or power generated from a renewable energy source such as solar power (step 303-1). The liquid metal thus produced is then transferred in step 304 to a ladle furnace, i.e., a smelting furnace (207), for refining purposes. Following the slag-metal reaction occurring in the ladle furnace (207), vacuum processing is performed by a vacuum refining unit (208) to refine the liquid metal and control the levels of gases such as O2, H2, and N2. The amount of GHG emissions generated during the steps is extremely low. Adjustments to the addition of ferroalloys are made in step 305-1 after the GHG emissions, which have very low VD levels, have been discharged. In the case of stainless steel, or when the wt% carbon requirement is much lower, the liquid metal is transferred to vacuum oxygen decarburization (VOD) in step 305 to remove carbon. The refined liquid metal thus produced is then transferred to either the continuous casting route (306) or the ingot casting route (307). In the disclosed method (200), green steel (600) with very low GHG emissions is produced in step 308, thereby significantly reducing the GHG emission level.

[0062] A further embodiment of the present disclosure is a method (100) for producing steel with very low greenhouse gas (GHG) emissions, covering Scope 1, Scope 2, and Scope 3 as defined by the GHG Protocol. The scopes include Scope 1: direct emissions during the manufacturing stage, Scope 2: indirect emissions during power generation, and Scope 3: indirect emissions during the production and transport of raw materials and fuel.

[0063] Table 1 shows the definitions of GHG emissions under Scope 1, Scope 2, and Scope 3. [Table 1]

[0064] Scope 1 Emission Reduction: The raw materials required to produce steel through the EAF route are charge mixtures that essentially contain various types of scrap. During EAF steelmaking, the use of pig iron, which is the main source of GHG emissions, is prohibited. Unlike the conventional EAF steelmaking route, where oxygen is blown in to generate energy through exothermic reactions, resulting in increased GHG emissions, the disclosed method limits the use of oxygen and supplies a calculated amount of oxygen necessary for dephosphorization. The energy required to melt the scrap is supplied entirely by electrical energy. Scrap is generated during hot deformation, casting, grinding, and machining, etc. Such scrap is available in the vicinity of the production site. Scrap sources (700) may include, but are not limited to, industrial scrap, manufacturing scrap, waste scrap, post-consumer scrap, process scrap, carbon steel scrap, stainless steel scrap, alloy steel scrap, non-ferrous scrap, electronic equipment scrap, or high-alloy scrap. To reduce and avoid the use of virgin ferroalloys, scrap (201) is carefully selected to conform to the chemical properties required for the finished steel products. In smelting furnaces (207) or ladle furnaces (hereinafter, the terms ladle furnace and smelting furnace are used interchangeably), and in vacuum degassing, a minimal amount of ferroalloy is used to adjust the additions after vacuum degassing (VD).

[0065] Scope 2: Electricity is generated using captive or non-captive renewable energy power plants and supplied via power sources (211). The same energy is used for electric arc furnaces (EAF), ladle furnaces (207), melting steel in vacuum degassing and VOD, and melting steel for casting via continuous casting (CC) or ingot casting (IC) routes. Biodiesel is used to generate the energy required for steam generation in boilers for vacuum degassing or to create a vacuum in the vacuum decarburization (VOD) process.

[0066] Scope 3: Raw materials, i.e., scrap, are transported to the melting facility using electric vehicles such as forklifts and e-trucks. Furthermore, such spent manufacturing scrap has zero GHG emissions according to ISO 14404-2:2013. Method for calculating carbon dioxide emission intensity from steel production, Part 2: Steel plants with electric arc furnaces (EAF).

[0067] In yet another embodiment of the present disclosure, the disclosure helps to minimize GHG emissions generated throughout the steelmaking method (100). Using the disclosed method (100), all types of steel, including low-carbon steel, medium-carbon steel, high-carbon steel, HSLA steel, low-alloy steel, micro-alloy steel, high-alloy steel, stainless steel, Fe-based superalloys, tool steel, die steel, or valve steel, can be effectively manufactured. The individual elemental ranges are specified in Table 2 below. Since the entire range of various chemical compositions of the steel grades that can be manufactured is a subset of the elemental ranges listed in Table 2, Table 2 encompasses all types of steel and iron alloys. [Table 2]

[0068] In summary, this disclosure integrates steps to reduce GHG emissions at each scope. To minimize Scope 1 emissions, scrap (201) is used as raw material. Scrap (201) is selected to match the chemical properties of the final finished grade steel products. Pig iron or directly reduced iron (DRI) is not used in the charge mixture. To reduce Scope 2 emissions, electricity is generated using renewable energy sources such as solar power and biodiesel for vacuum generation. To reduce Scope 3 emissions, scrap (201) is collected from nearby locations and transported to the melting station via electric vehicles.

[0069] In yet another embodiment of this disclosure, practical examples illustrating method (100) are disclosed. [Examples]

[0070] Example 1: Method (100) is applied to two more cases of different types of low-alloy steel, such as Cr-Mo steel and Cr-Ni-Mo steel. In all cases, neither pig iron nor DRI is used, and oxygen is blown into the EAF if necessary for dephosphorization. Heating numbers: HN170967 (Regular) and GS177974 (Green Steel); Grade: AISI 4340 [Table 3]

[0071] Table 4 shows scrap (201) and ferroalloys, as well as their respective consumption amounts. [Table 4]

[0072] Table 5 shows the emissions related to the heat generated by green steel. [Table 5]

[0073] Example 2: Heating numbers: HN178103 (Regular) and GS169107 (Green Steel); Grade: 4140H Table 6 shows the chemical composition achieved in the ladle furnace. [Table 6]

[0074] Table 7 shows scrap metal, ferroalloys, and their respective consumption amounts. [Table 7]

[0075] Table 8 below shows the emissions related to the heat generated by green steel. [Table 8]

[0076] Using the method disclosed in this invention, the GHG emissions generated during the production of crude steel for 4340 steel and 4140 steel are 0.210 and 0.227 tCO2e / MT steel castings, respectively. In contrast, the conventional route for the production of crude steel for 4340 steel and 4140 steel yields 1.911 and 1.688 tCO2e / MT steel castings, respectively. Thus, this disclosure has helped to significantly reduce GHG emissions by 80-90% compared to the emissions generated by using conventional processing routes. Therefore, method (100) is useful for reducing GHG emissions and can be used in the production of various steel grades from different series.

[0077] The above describes only preferred embodiments of the Disclosure and does not limit the Disclosure. Any modifications, equivalent substitutions, and improvements within the scope of the principles of the Disclosure should be included within the scope of the Disclosure.

[0078] Since the subject matter of dependent claims may constitute separate and independent disclosures in relation to the prior art on the priority date, the applicant reserves the right to make them the subject matter of independent claims or divisional applications. These may further include independent disclosures having a structure independent of the subject matter of the preceding dependent claims.

[0079] Furthermore, elements and / or features of different exemplary embodiments may be combined with and / or substituted for each other within the scope of the present disclosure and the appended claims.

[0080] Benefits of this disclosure The proposed disclosure provides a system and method that includes an improved melting step using EAF to produce environmentally friendly, i.e., very low-carbon-emission green steel.

[0081] The proposed disclosure provides a system and method that includes oxygen control mechanisms, such as oxygen lances and flow control systems, used to precisely manage the oxygen supply during the steelmaking process, thereby reducing energy consumption and minimizing emissions.

[0082] The proposed disclosure provides a system and method for producing green steel with minimal environmental impact, emphasizing environmental sustainability by incorporating renewable energy sources, precise control of scrap segregation, and optimization of oxygen supply and refining processes.

[0083] The proposed disclosure provides a system and method that offers a cost-effective way to produce green steel with very low emissions when green hydrogen is not used.

[0084] The proposed disclosure provides systems and methods required for melting in EAF and LF furnaces, as well as in vacuum refining equipment, and for casting alloys produced thereby, using power sources generated by renewable energy sources such as solar power.

[0085] The proposed disclosure provides a system and method for generating a vacuum for vacuum degassing (VD) and vacuum oxygen decarburization (VOD) using biodiesel for boiler operation.

Claims

1. A method (100) for manufacturing green steel (600), wherein the method (100) is A step (101) of obtaining scrap (201) from one or more scrap sources (700), wherein the scrap (201) includes different types of scrap alloys (202) present therein, Step (102) of charging the obtained scrap (201) into an electric furnace (203), A step of obtaining molten steel (204) by melting the charged scrap (201) in the electric furnace (203) (103), wherein the charged scrap (201) is melted in the electric furnace (203) in the presence of a controlled oxygen supply, The molten steel (204) is transferred from the electric furnace (203) to a refining furnace (207) connected to the electric furnace (203) (104), the molten steel (204) is refined, and then transferred to a casting area (206) to obtain the green steel (600), and Method (100), including the method (100).

2. The aforementioned scrap (201) is obtained from one or more scrap sources (700) using an electric vehicle. The electric furnace (203) is an electric arc furnace (EAF), The obtained scrap (201) is separated to obtain a predetermined metal composition therefrom, and the obtained scrap (201) is then charged into the electric arc furnace (203), and the obtained scrap (201) is selected from any or a combination thereof from industrial scrap, manufacturing scrap, waste scrap, post-consumer scrap, process scrap, carbon steel scrap, stainless steel scrap, alloy steel scrap, non-ferrous scrap, electronic equipment scrap, or high-alloy scrap. The method according to claim 1 (100), wherein the controlled oxygen supply is performed using one or more control means (205) connected to the electric furnace (203), and the one or more control means (205) is selected from an oxygen lance, one or more flow control valves, one or more flow controllers, or oxygen purity control.

3. The above method (100) The step of obtaining slag by mixing one or more refining agents with the charged scrap (201) in the electric furnace (203), wherein the one or more refining agents are lime (CaO), fluorite (CaF ２ ), dolomite (CaMg(CO) ３ ) ２ The steps include selecting from either ), or synthetic slag material, A step of purifying the charged scrap (201) by mixing the obtained slag with the charged scrap (201) by one or more slag-metal reactions, wherein the one or more slag-metal reactions are selected from any or a combination thereof from dephosphorization, desulfurization, deoxidation, inclusion removal, gas removal (hydrogen, nitrogen or oxygen), or decarburization. The method according to claim 1, further comprising (100).

4. The above method (100) A step of refining the molten steel (204) in a refining furnace (207) connected to the electric furnace (203) (105), and then transferring it to the casting area (206), wherein the refining furnace (207) is connected to the electric furnace (203), The steps include: adjusting the molten steel (204) by adding one or more ferroalloys and alloying elements (106) to obtain a predetermined chemical composition of the refined steel (204); The steps include: degassing the refined steel (204) by the refining furnace (207) and the vacuum refining apparatus (208) connected to the casting area (206) (107), and transferring the vacuum-refined steel to the casting area (206); The method according to claim 1, further comprising (100).

5. The obtained scrap (201) is charged using a power source (111) generated from a renewable energy source. The loaded scrap (201) is melted using the power supply (111) generated from the renewable energy source. The molten steel (204) is refined using the power supply (111) generated from the renewable energy source. The method according to claim 1 (100), wherein the vacuum refining apparatus (208) uses the power supply (111) generated from the renewable energy source and uses biodiesel as fuel for steam generation to form a vacuum for the operation of one or more boilers.

6. The method according to claim 1 (100), wherein the manufactured green steel (600) is selected from any or a combination thereof from low carbon steel, medium carbon steel, high carbon steel, microalloy steel, high-strength low-alloy (HSLA) steel, low-alloy steel, high-alloy steel, stainless steel, iron (Fe)-based superalloy steel, and tool steel, die steel, or valve steel.

7. The method according to claim 1 (100), wherein the different types of scrap alloys (202) are selected based on the chemical composition related to the obtained scrap (201).

8. The method according to claim 1 (100), wherein the casting region (206) comprises one or more molds for shaping vacuum-refined steel into one or more shapes, and the casting region (206) further comprises a cooling system (206-1) for promoting the solidification of molten metal.

9. A system (200) for manufacturing green steel (600), wherein the system (200) An electric furnace (203) for charging scrap (201), wherein the scrap (201) is obtained from one or more scrap sources (700), and the scrap (201) contains different types of scrap alloys (202) present therein, A melting means (209) for melting the scrap (201) charged into the electric furnace (203), wherein the charged scrap (201) is melted in the presence of a controlled oxygen supply obtained in the electric furnace (203), A transfer means (210) for transferring the molten steel (204) from the electric furnace (203) to a refining furnace (207) connected to the electric furnace (203) in order to refine the molten steel (204), A vacuum refining apparatus (208) for degassing the refined steel received from the refining furnace (207) before transferring it to the casting area (206), thereby obtaining the green steel (600), and System (200), including the above.

10. The aforementioned scrap (201) is obtained from one or more scrap sources (700) using an electric vehicle. The electric furnace (203) is an electric arc furnace (EAF), The obtained scrap (201) is separated to obtain a specific combination of metals therefrom, and the obtained scrap (201) is then charged into the electric arc furnace (203), and the obtained scrap (201) is selected from any or a combination thereof from industrial scrap, manufacturing scrap, waste scrap, post-consumer scrap, process scrap, carbon steel scrap, stainless steel scrap, alloy steel scrap, non-ferrous scrap, electronic equipment scrap, or high-alloy scrap. The system (100) according to claim 9, wherein the controlled oxygen supply is performed using one or more control means (205) connected to the electric furnace (203), and the one or more control means (205) is selected from an oxygen lance, one or more flow control valves, one or more flow controllers, or oxygen purity control.

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