Steelmaking system and method for manufacturing steel strip

Abstract

This steelmaking system comprises an electric arc furnace (EAF) for preparing molten steel, an electric smelting furnace (ESF) for preparing molten iron, a recovery device for separating reduced iron from off-gas discharged from the electric smelting furnace, and a separation guide for supplying the reduced iron, which is separated in the recovery device, to the electric arc furnace.

Description

Steelmaking system and steel strip manufacturing method

[0001] The present disclosure relates to a steelmaking system including an electric furnace and a method for manufacturing steel strips.

[0002] Pig iron can be produced in blast furnaces. When pig iron is produced using the blast furnace method, carbon monoxide is used as a reducing gas and is oxidized into carbon dioxide. As carbon dioxide is one of the greenhouse gases, its reduction is necessary to achieve carbon neutrality.

[0003] Research and development are underway on electric furnace operations based on hydrogen-direct reduced iron (H2-DRI) capable of reducing carbon dioxide emissions. By producing hydrogen-reduced iron using hydrogen and melting it using electricity to produce molten iron, carbon dioxide emissions can be significantly reduced compared to blast furnace operations that produce molten iron using coke.

[0004] Electric furnaces used in electric furnace operations include, for example, the Electric Arc Furnace (EAF) and the Electric Smelting Furnace (ESF). The EAF produces molten steel, but it is unfavorable for manufacturing high-grade steel due to the disadvantage of increasing the nitrogen concentration in the molten steel during the melting process. The ESF produces molten iron, and since molten steel is produced in a converter located downstream, it is advantageous for manufacturing high-grade steel.

[0005] Electric arc furnaces have primarily been used for melting reduced iron; however, due to equipment limitations, the use of high-grade reduced iron with a high iron content is required. High-grade iron ore may require prior beneficiation or, as a high-cost product, can lead to increased production costs.

[0006] In order to establish a sustainable electric arc furnace process, it is necessary to develop a melting process utilizing low-grade iron ore. For example, low-grade iron ore may include iron ore with an iron content of less than 62%, and high-grade iron ore may include iron ore with an iron content of 62% or more.

[0007] According to one aspect of the present disclosure, a steelmaking system and a method for manufacturing steel strips are provided that can reduce losses occurring during the process of transporting and using raw materials in an electric melting reduction furnace (ESF).

[0008] According to one aspect of the present disclosure, a steelmaking system and a method for manufacturing steel strips are provided that can reduce costs incurred for processing process by-products of a steel mill.

[0009] According to one aspect of the present disclosure, a steelmaking system and a method for manufacturing steel strips are provided that can improve the quality of steel produced through an electric arc furnace (EAF).

[0010] According to one aspect of the present disclosure, a steelmaking system and a method for manufacturing steel strips are provided that can improve the yield of molten steel in an electric arc furnace (EAF).

[0011] The technical problems to be solved in this document are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this invention belongs from the description below.

[0012] According to one aspect of the present invention, a steelmaking system comprises an electric arc furnace (EAF) for producing molten steel, an electric smelting furnace (ESF) for producing molten iron, a recovery device for separating reduced iron from exhaust gas discharged from the electric smelting furnace, and a separation guide for supplying the reduced iron separated by the recovery device to the electric arc furnace.

[0013] The above-described steelmaking system may further include an HBI manufacturing device for producing HBI (Hot Briquetted Iron) by rolling reduced iron supplied to the electric arc furnace at high temperature.

[0014] The above separation guide may be configured to supply reduced iron discharged from the above recovery device to the electric arc furnace via the above HBI manufacturing device.

[0015] The above-described steelmaking system may further include a mixing line for mixing at least a portion of the molten iron produced in the electric melting reduction furnace with the molten steel produced in the electric arc furnace.

[0016] The above-described ironmaking system may further include a fluidized reduction furnace for converting iron ore into reduced iron and supplying it to the electric arc furnace and the electric melting reduction furnace.

[0017] The above fluidized reduction furnace may be configured such that the average particle size of the reduced iron produced from the fluidized reduction furnace is smaller than the average particle size of the raw materials charged into the fluidized reduction furnace.

[0018] The hydrogen gas supplied to the above fluidized bed reduction furnace can be arranged to be at a temperature of 600°C or higher and 900°C or lower.

[0019] The above electric melting reduction furnace can be configured to melt reduced iron by a brush arc formed by a plurality of electrode rods.

[0020] The above electric melting reduction furnace may be configured to melt reduced iron by heat generated by a plurality of electrode rods that are at least partially immersed in slag.

[0021] According to one aspect of the present invention, a steelmaking system comprises an electric arc furnace (EAF) for producing molten steel, an electric smelting furnace (ESF) for producing molten iron, an HBI (Hot Briquetted Iron) manufacturing device for producing HBI by rolling reduced iron supplied to the electric arc furnace at high temperature, a recovery device for separating reduced iron from exhaust gas discharged from the electric smelting furnace, a separation guide for supplying reduced iron separated from the recovery device to the electric arc furnace via the HBI, and a mixing guide for mixing at least a portion of the molten iron produced in the electric smelting furnace with the molten steel produced in the electric arc furnace.

[0022] According to one aspect of the present invention, a method for manufacturing a steel strip may include the steps of obtaining molten iron using a steelmaking system, adjusting the composition of the molten iron, casting the molten iron with adjusted composition to obtain a slab, and rolling the slab.

[0023] The steelmaking system and steel strip manufacturing method according to the embodiments of the present invention are configured to separate and recover Fine Direct Reduced Iron (Fine DRI) from the exhaust gas discharged from the Electric Molten Reducer (ESF) and supply it to the Electric Arc Furnace (EAF), thereby reducing losses that occur during the raw material transfer and usage process of the Electric Molten Reducer (ESF).

[0024] The steelmaking system and steel strip manufacturing method according to the embodiments of the present invention are configured to separate and recover Fine Direct Reduced Iron (Fine DRI) from the flue gas discharged from the Electric Molten Reducer (ESF) and supply it to the Electric Arc Furnace (EAF), thereby reducing the costs incurred for the treatment of process by-products in a steel mill.

[0025] The steelmaking system and steel strip manufacturing method according to the embodiments of the present invention are configured to mix at least a portion of the molten iron produced in an electric melting reduction furnace (ESF) with molten steel produced in an electric arc furnace (EAF), thereby improving the quality of the steel produced through the electric arc furnace (EAF).

[0026] The steelmaking system and steel strip manufacturing method according to the embodiments of the present invention are configured to mix at least a portion of the molten iron produced in an electric melting reduction furnace (ESF) with the molten steel produced in an electric arc furnace (EAF), thereby improving the yield of the molten steel in the electric arc furnace (EAF).

[0027] The effects according to the concept of the present disclosure are not limited to the effects mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description below.

[0028] FIG. 1 schematically illustrates a steelmaking system according to one embodiment of the present disclosure.

[0029] The embodiments described in this specification are merely the most preferred embodiments of the present invention and do not represent all technical concepts of the present invention; therefore, it should be understood that various equivalents or modifications that can replace them at the time of filing this application are also included within the scope of the rights of the present invention.

[0030] Singular expressions used in the description may include plural expressions unless the context clearly indicates otherwise. In the drawings, the shapes and sizes of elements may be exaggerated to provide a clearer description.

[0031] In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0032] Throughout the specification, ordinal expressions such as “first” and “second” are used to distinguish multiple components from one another, and the ordinals used do not indicate the order of placement, manufacturing order, or importance among the components.

[0033] When it is stated that a component is "connected" to another component, it should be understood that it may be directly connected to that other component, or that there may be other components in between.

[0034] FIG. 1 schematically illustrates a steelmaking system according to one embodiment of the present disclosure.

[0035] Referring to FIG. 1, a steelmaking system (1) according to one embodiment of the present disclosure may include a fluidized reduction furnace (10), an electric melting reduction furnace (20), and an electric arc furnace (30). A steelmaking system (1) according to one embodiment of the present disclosure may include a recovery device (40) and an HBI manufacturing device (50).

[0036] The ironmaking system (1) may include a fluidized reduction furnace (10). The fluidized reduction furnace (10) may be configured to convert iron ore into reduced iron and supply it to an electric arc furnace (30) and an electric melting reduction furnace (20).

[0037] For example, a fluidized reduction furnace (10) may be advantageous for controlling the temperature of the reduction furnace compared to a shaft reduction furnace. Since insufficient heat in the reduction furnace can cause iron ore to fail to reduce, a fluidized reduction furnace (10) which is advantageous for controlling the temperature of the reduction furnace in hydrogen reduction steelmaking may be desirable.

[0038] The fluidized reduction furnace (10) may be supplied with high-temperature hydrogen reducing gas, which is heated by the heat of reaction with oxygen. For example, the fluidized reduction furnace (10) may include a multi-stage reduction furnace in which a plurality of reactors are configured in a step-like manner. Among the plurality of reactors, oxygen may be introduced into at least some or each of them, or the inside of the reactor may be heated by heating the bottom or wall of the reactor. For example, the hydrogen gas supplied to the fluidized reduction furnace (10) may be approximately 900°C or lower. For example, the hydrogen gas supplied to the fluidized reduction furnace (10) may be approximately 600°C or higher and 900°C or lower. For example, the hydrogen gas supplied to the fluidized reduction furnace (10) may be approximately 700°C or higher and 900°C or lower. Since the inside of the reactor can be heated not only by hydrogen gas but also by heating the bottom or wall, a sufficient reduction reaction can be induced even if introduced at a temperature of 900°C or lower.

[0039] Inside the fluidized reduction furnace (10), iron oxide can be reduced and converted into reduced iron. Reduced iron may also be referred to as sponge iron. Reduced iron can be charged into an electric arc furnace (30) and / or an electric melting reduction furnace (20) in powder form or in agglomerated form. Reduced iron in powder form can be produced in the fluidized reduction furnace (10). The ash loaded into the fluidized reduction furnace (10) may have a particle size of approximately greater than 0 mm and less than or equal to 8 mm. This ash can be produced into reduced iron in powder form through the fluidized reduction furnace (10).

[0040] For example, reduced iron in powder form may have a particle size of approximately 8 mm or less. For example, reduced iron in powder form may have a particle size of approximately 7 mm or less. For example, reduced iron in powder form may have a particle size of approximately 6 mm or less. However, the particle size of reduced iron in powder form is not limited thereto.

[0041] In the fluidized reduction furnace (10), the raw materials flowing through it may collide with each other and be crushed into smaller pieces. For example, the fluidized reduction furnace (10) may be configured such that the average particle size of the reduced iron produced from the fluidized reduction furnace (10) is smaller than the average particle size of the raw materials charged into the fluidized reduction furnace (10). For example, the average particle size calculated from the raw materials prior to being charged into the fluidized reduction furnace (10) may be larger than the average particle size of the reduced iron.

[0042] For example, the massive method may include a high-temperature molding method. Massive reduced iron sources can be produced by mixing pulverized reduced iron with pyroclastic limestone and pulverized white meteorite. A mixture of pulverized reduced iron, pyroclastic limestone, and pulverized white meteorite can be produced by compression molding at a high temperature. For example, the high temperature may be 500°C or higher. For example, the high temperature may be 550°C or higher. For example, the high temperature may be 600°C or higher. For example, the high temperature may be 650°C or higher.

[0043] A fluidized reduction furnace (10) can produce fine direct reduced iron (Fine DRI) by fluidizing the fine ore. For example, the fine direct reduced iron (Fine DRI) may have a particle size of approximately 8 mm or less. For example, the fine direct reduced iron (Fine DRI) may be reduced to a metallization rate of approximately 60% or more. For example, the fine direct reduced iron (Fine DRI) may be reduced to a metallization rate of approximately 70% or more. For example, the fine direct reduced iron (Fine DRI) may be reduced to a metallization rate of approximately 80% or more.

[0044] Reduced iron (e.g., fine reduced iron and / or bulk reduced iron) produced in the fluidized reduction furnace (10) can be charged into an electric melting reduction furnace (20) and an electric arc furnace (30). A portion of the fine direct reduced iron (Fine DRI) produced in the fluidized reduction furnace (10) can be supplied to at least one electric melting reduction furnace (20), and another portion can be supplied to at least one electric arc furnace (30).

[0045] The steelmaking system (1) may include an electric smelting furnace (20, Electric Smelting Furnace, ESF). The electric smelting furnace (20) can melt raw materials in a reducing atmosphere.

[0046] The electric melting reduction furnace (20) may be configured to produce molten iron. For example, the electric melting reduction furnace (20) may be suitable for producing high-grade steel because it produces molten steel in a downstream converter.

[0047] The electric melting reduction furnace (20) may include a plurality of electrode rods. For example, the electric melting reduction furnace (20) may be configured to melt reduced iron by a brush arc formed by a plurality of electrode rods. For example, the electric melting reduction furnace (20) may be configured to melt reduced iron by heat formed by a plurality of electrode rods that are at least partially immersed in slag.

[0048] For example, fine direct reduced iron (Fine DRI) produced in a fluidized reduction furnace (10) can be stored in a storage. The fine direct reduced iron (Fine DRI) stored in the storage can be transported by a crane and fed into an electric melting reduction furnace (20). Most of the fine direct reduced iron (Fine DRI) fed into the electric melting reduction furnace (20) forms a pile in the electric melting reduction furnace (20) and is melted by an electrode rod, while the remaining portion can be discharged to the outside by the airflow inside the furnace.

[0049] The steelmaking system (1) may include a discharge guide (21) for guiding exhaust gas and fine direct reduced iron (Fine DRI) discharged from an electric melting reduction furnace (20) to a recovery device (40). The discharge guide (21) may connect the electric melting reduction furnace (20) and the recovery device (40). For example, the discharge guide (21) may include at least one of a flow path, a pipe, a hose, a duct, and / or a line.

[0050] The steelmaking system (1) may include a recovery device (40, separator). The recovery device (40) may be configured to separate reduced iron from the flue gas discharged from the electric melting reduction furnace (20). The recovery device (40) may collect fine direct reduced iron (Fine DRI) discharged from the electric melting reduction furnace (20). For example, since the fine direct reduced iron (Fine DRI) contained in the flue gas discharged from the electric melting reduction furnace (20) is a useful resource with a high iron content, economic efficiency can be improved by recovering and recycling it.

[0051] For example, fine direct reduced iron (Fine DRI) may be discharged from the electric melting reduction furnace (20) along with the exhaust gas of the electric melting reduction furnace (20). The recovery device (40) can recover fine direct reduced iron (Fine DRI) by filtering the exhaust gas discharged from the electric melting reduction furnace (20). As an example, the recovery device (40) can first cool the exhaust gas to a suitable temperature and then separate and collect fine direct reduced iron (Fine DRI) by passing it through several stages of filters.

[0052] The steelmaking system (1) may include a separation guide (41) for supplying reduced iron separated from the recovery device (40) to the electric arc furnace (30). For example, the separation guide (41) may be configured to supply reduced iron discharged from the recovery device (40) to the electric arc furnace (30) via the HBI manufacturing device (50).

[0053] The separation guide (41) can combine the fine direct reduced iron (Fine DRI) recovered by the recovery device (40) with the fine direct reduced iron (Fine DRI) supplied to the electric arc furnace (30). The combined fine direct reduced iron (Fine DRI) can be supplied to the electric arc furnace (30). For example, the combined fine direct reduced iron (Fine DRI) can be supplied to the electric arc furnace (30) via the HBI manufacturing device (50).

[0054] A steelmaking system (1) according to one embodiment of the present disclosure can separate fine direct reduced iron (Fine DRI) from the exhaust gas discharged from the electric melting reduction furnace (20) and supply it to the electric arc furnace (30), thereby improving the yield. A steelmaking system (1) according to one embodiment of the present disclosure can separate fine direct reduced iron (Fine DRI) from the exhaust gas discharged from the electric melting reduction furnace (20) and supply it to the electric arc furnace (30), thereby reducing losses occurring during the process of transporting and using raw materials in the electric melting reduction furnace (20). A steelmaking system (1) according to one embodiment of the present disclosure can separate fine direct reduced iron (Fine DRI) from the exhaust gas discharged from the electric melting reduction furnace (20) and supply it to the electric arc furnace (30), thereby reducing costs incurred during the treatment of steelmaking process by-products.

[0055] The steelmaking system (1) may include an electric arc furnace (30, Electric Arc Furnace, EAF). The electric arc furnace (30) may be configured to produce molten steel. For example, the electric arc furnace (30) may increase the nitrogen concentration in the molten steel during the melting process, so it may not be suitable for producing high-grade steel.

[0056] The electric arc furnace (30) can produce molten steel by converting electric energy into thermal energy to melt direct reduced iron (DRI). For example, the electric arc furnace (30) may include a cylindrical furnace body and a detachable roof. The furnace body contains refractory material, and a graphite electrode may be mounted on the upper roof. For example, three electrodes may be used, and they may be configured to move up and down via an electrode lifting device.

[0057] For example, the electric arc furnace (30) can be loaded with raw materials by loading direct reduced iron (DRI) into a basket and moving the basket with a crane when the top of the furnace body is opened. Once loading is complete, the electrode can be lowered to come into contact with the material being loaded, and the material can be melted by the heat generated as an arc occurs between the electrode and the material being loaded. After melting is complete, a refining process can follow. During the refining process, treatments such as adding ferroalloys to control composition, deoxidation, and desulfurization can be performed, and the temperature and composition can be adjusted. When the target temperature and composition are reached, a tapping operation can be performed to receive the molten steel into a ladle and transfer it to a subsequent process.

[0058] Due to the characteristics of the equipment, the electric arc furnace (30) may require the use of high-quality reduced iron with a relatively high iron content. The ironmaking system (1) according to one embodiment of the present disclosure can supply high-quality reduced iron with a relatively high iron content to the electric arc furnace (30) by means of a fluidized reduction furnace (10).

[0059] The electric arc furnace (30) can use fine direct reduced iron (Fine DRI) or hot briquetted iron (HBI) produced by processing fine direct reduced iron (Fine DRI). For example, fine direct reduced iron (Fine DRI) is composed of relatively small particles, so it may be disadvantageous to oxidation. For example, hot briquetted iron (HBI) may have a relatively high density. As hot briquetted iron (HBI) has a high density, the iron content per unit volume increases, which can reduce logistics costs.

[0060] The steelmaking system (1) may include an HBI manufacturing device (50) for manufacturing hot briquetted iron (HBI). The HBI manufacturing device (50) may be configured to manufacture hot briquetted iron (HBI) by rolling reduced iron supplied to an electric arc furnace (30) at high temperature. For example, the HBI manufacturing device (50) may form by compressing at high pressure. For example, the HBI manufacturing device (50) may be configured to continuously perform several stages of processes, such as uniform mixing of raw materials, temperature control, pressure control, and product extraction. At each process stage, key process variables may be monitored and controlled through sensors and a control system.

[0061] The steelmaking system (1) may include a mixing line (61) for mixing at least a portion of the molten iron produced in the electric melting reduction furnace (20) with the molten steel produced in the electric arc furnace (30). For example, since the molten iron produced in the electric melting reduction furnace (20) may have a relatively low impurity concentration and the molten steel produced in the electric arc furnace (30) may have a relatively high impurity concentration, when the molten iron produced in the electric melting reduction furnace (20) is mixed with the molten steel produced in the electric arc furnace (30), a relatively high-quality steel can be produced.

[0062] Specific embodiments have been illustrated and described above. However, the invention is not limited to the embodiments described above, and those skilled in the art may make various modifications without departing from the essence of the technical concept of the invention as described in the following claims.

Claims

1. Electric Arc Furnace (EAF) for producing molten steel; Electric Smelting Furnace (ESF) for producing molten iron; A recovery device for separating reduced iron from exhaust gas discharged from the above-mentioned electric melting reduction furnace; and A steelmaking system comprising a separation guide for supplying reduced iron separated from the above recovery device to the above electric arc furnace.

2. In Paragraph 1, A steelmaking system further comprising an HBI manufacturing device for producing HBI (Hot Briquetted Iron) by rolling reduced iron supplied to the electric arc furnace at high temperature.

3. In Paragraph 2, The above separation guide is a steelmaking system configured to supply reduced iron discharged from the above recovery device to the electric arc furnace via the above HBI manufacturing device.

4. In Paragraph 1, A steelmaking system further comprising a mixing line for mixing at least a portion of the molten iron produced in the electric melting reduction furnace with the molten steel produced in the electric arc furnace.

5. In Paragraph 1, A steelmaking system further comprising a fluidized reduction furnace for converting iron ore into reduced iron and supplying it to the electric arc furnace and the electric melting reduction furnace.

6. In Paragraph 5, The above fluidized reduction furnace is a steelmaking system configured such that the average particle size of the reduced iron produced from the above fluidized reduction furnace is smaller than the average particle size of the raw materials charged into the above fluidized reduction furnace.

7. In Paragraph 5, A steelmaking system configured such that the hydrogen gas supplied to the above-mentioned fluidized reduction furnace is at a temperature of 600°C or higher and 900°C or lower.

8. In Paragraph 1, The above electric melting reduction furnace is an ironmaking system configured to melt reduced iron by a brush arc formed by a plurality of electrode rods.

9. In Paragraph 1, The above electric melting reduction furnace is an ironmaking system configured to melt reduced iron by heat generated by a plurality of electrode rods at least partially immersed in slag.

10. Electric Arc Furnace (EAF) for producing molten steel; Electric Smelting Furnace (ESF) for producing molten iron; An HBI manufacturing apparatus for producing HBI (Hot Briquetted Iron) by rolling reduced iron supplied to the above electric arc furnace at high temperature; and A recovery device for separating reduced iron from exhaust gas discharged from the above-mentioned electric melting reduction furnace; A separation guide for supplying reduced iron separated from the above recovery device to the electric arc furnace via the above HBI; and A steelmaking system comprising: a mixing guide for mixing at least a portion of the molten iron produced in the electric melting reduction furnace with the molten steel produced in the electric arc furnace.

11. A step of obtaining molten iron using a steelmaking system according to any one of claims 1 to 10; A step of adjusting the composition of the molten iron above; A step of obtaining a slab by casting molten iron with the above-mentioned components adjusted; and A step of rolling the above slab; A method for manufacturing a steel strip including

Images