Fine material feeding structure for an electric arc furnace

Abstract

A fine raw material feeding structure for an electric arc furnace is disclosed. According to one aspect of the invention, a fine raw material feeding structure for an electric arc furnace can be provided, comprising: a furnace body for receiving raw materials; a top for opening / closing an upper portion of the furnace body; at least one electrode rod inserted into the furnace body through the top; and a waste gas duct disposed in the top. The structure includes a supply pipe connected to a raw material hopper for supplying powdered raw materials to the furnace body, wherein the supply pipe is vertically arranged from the raw material hopper positioned above the furnace body toward a molten iron pool, and the height from the molten iron pool to the end of the supply pipe for discharging the powdered raw materials has a value less than 100 times the maximum size of the powdered raw materials, such that the loss rate of the powdered raw materials discharged from the supply pipe is included in a desired target value.

Description

Technical Field

[0001] This disclosure relates to raw material filling structures, and more specifically, to fine material filling structures for electric furnaces for filling powdered raw materials into an electric furnace without loss. Background Technology

[0002] Typically, electric arc furnaces are used primarily to melt raw materials such as scrap iron using the heat of an electric arc generated through electrode rods. On the other hand, molten reduction electric furnaces are constructed to directly produce molten iron from raw materials in a powdered state. For producing high-quality steel, direct reduced iron (DRI) or hot-pressed iron (HBI) is used as the raw material in molten reduction electric furnaces. In addition to DRI or HBI, powdered limestone and coal are injected to obtain the desired composition of the molten iron. Limestone acts as a flux, helping to remove impurities from the steel, and coal is added to the molten iron to increase the carbon content of the produced steel.

[0003] Figure 1 The illustration shows a melting and reducing electric furnace used to produce molten iron by supplying powdered raw materials.

[0004] Reference Figure 1 The electric furnace 10 includes a furnace body 11, a top 12 for opening and closing the upper part of the furnace body 11, an electrode rod 1 inserted into the furnace body 11 through an electrode rod hole formed in the top 12, a raw material loading tank 13 in contact with the top 12 for injecting powder raw material S, and an exhaust gas pipe 14 for discharging exhaust gas generated during the melting of the powder raw material S.

[0005] The furnace body 11 includes an iron shell 11a forming the framework of the furnace body 11 and a refractory layer 11b constructed inside the iron shell 11a. Inside the furnace body 11, a layer of molten iron 15 (hereinafter referred to as "molten iron pool") formed by melting raw materials is formed, and a layer of slag 16 floating on the molten iron pool 15 is formed. In addition, the furnace body 11 is provided with a slag outlet 18 that penetrates the wall surface to discharge slag and a molten iron outlet 17 that discharges molten iron.

[0006] When powdered raw material S is injected into the furnace body 11 through the raw material filling tank 13, electricity is supplied to the electrode rod 1 to carry out melting and reduction reactions.

[0007] However, when powdered raw material S is injected from the upper part of the furnace body 11 to produce molten iron, a problem arises: the powdered raw material S floats due to the heat inside the electric furnace 10 and the suction force of the exhaust gas pipe 14, and escapes along with the gas generated inside the electric furnace 10 through the exhaust gas port to the dust collector (not shown) in the direction of arrow B. This results in a loss of raw material, which not only reduces productivity but also increases raw material costs. Furthermore, the pipes and dust collector become clogged with raw material escaping through the exhaust gas pipe 14, thereby shortening the repair and replacement cycle. Summary of the Invention

[0008] Technical issues

[0009] One aspect of this disclosure is to provide a fine material loading structure for an electric furnace that minimizes the loss of raw materials generated during molten iron production.

[0010] Technical solution

[0011] According to one aspect of this disclosure, a fine material loading structure for an electric furnace includes a furnace body for containing raw materials, a top for opening and closing an upper portion of the furnace body, at least one electrode rod inserted into the furnace body through the top, and a waste gas pipe disposed in the top. The fine material loading structure includes a supply pipe connected to a raw material hopper for supplying powdered raw materials and loading the powdered raw materials into the furnace body. The supply pipe is vertically positioned from the raw material hopper located in the upper portion of the furnace body toward the molten iron pool, and the height from the molten iron pool to the distal end of the supply pipe from which the powdered raw materials are discharged is set to have a value less than 100 times the maximum size of the powdered raw materials, such that the loss rate of the powdered raw materials discharged from the supply pipe is included in the desired target value.

[0012] The nozzle unit formed at the distal end portion of the supply tube can be configured to have at least two or more nozzle orifices.

[0013] The diameter of the nozzle orifice can be formed to be 10 times or more the maximum size of the powder raw material.

[0014] The supply tube can be made of graphite or ceramic materials.

[0015] The supply pipe can be configured to inject inert gas along with the powdered raw material.

[0016] The supply pipe can be arranged along the furnace wall of the furnace body in a way that exceeds 2 / 3 of the length of the circular track from the center of the furnace body to the center of the multiple electrode rods.

[0017] The supply pipe can be arranged at an imaginary line between 10° and 60° relative to the central part of the connecting furnace body and the center of the electrode rod.

[0018] When multiple electrode rods are set up and arranged in a straight line, the supply pipe can be positioned at a location that is more than 2 / 3 of the distance between the centers of the electrode rods.

[0019] Beneficial effects

[0020] The fine material loading structure for electric furnaces according to embodiments of this disclosure has the effect of minimizing the loss of raw materials generated during molten iron production, thereby improving the yield and quality of the final product.

[0021] In addition, the increased efficiency of electric furnace equipment reduces operating costs and makes it applicable to a variety of steel manufacturing applications. Attached Figure Description

[0022] Figure 1 This is a diagram showing a conventional melting-reduction electric furnace.

[0023] Figure 2 This is a diagram illustrating a melting-reduction electric furnace employing a fine material filling structure according to an embodiment of the present disclosure.

[0024] Figure 3 This is a diagram showing a nozzle unit of a supply pipe disposed in a fine material filling structure according to an embodiment of the present disclosure.

[0025] Figure 4 This is a graph showing the relationship between the loss rate of raw materials and the location of the supply pipe according to an embodiment of the present disclosure.

[0026] Figure 5 This is a graph showing the relationship between the size of the nozzle orifice formed in the supply pipe according to an embodiment of the present disclosure and the nozzle clogging rate.

[0027] Figure 6 This is a diagram showing the state in which the supply tube is positioned relative to the electrode rod according to an embodiment of the present disclosure. Detailed Implementation

[0028] In the following, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following embodiments are presented to fully convey the spirit of the present disclosure to those skilled in the art. The present disclosure is not limited to the embodiments presented herein, but may be embodied in other forms. In the drawings, figures of parts unrelated to the description have been omitted to clarify the disclosure, and the dimensions of components may be slightly exaggerated for ease of understanding.

[0029] Figure 2 This is a diagram illustrating a melt-reduction electric furnace employing a fine material packing structure according to an embodiment of the present disclosure. Figure 3This is a diagram illustrating a nozzle unit of a supply pipe disposed in a fine material filling structure according to an embodiment of the present disclosure. Figure 4 This is a graph showing the relationship between the raw material loss rate and the installation location of the supply pipe according to an embodiment of the present disclosure. Figure 5 This is a graph showing the relationship between the size of the nozzle orifice formed in the supply pipe according to an embodiment of the present disclosure and the nozzle clogging rate. Figure 6 This is a diagram showing the state in which the supply tube is positioned relative to the electrode rod according to an embodiment of the present disclosure.

[0030] Reference Figures 2 to 6 According to one aspect of this disclosure, the fine material loading structure is a device for loading raw material S in powder form into a melting-reduction electric furnace (hereinafter referred to as "furnace"). Here, the electric furnace 10 is arranged in the same configuration as the electric furnace 10 described in the background section above. However, the difference lies in the conventional raw material loading tank 13 used for loading the powdered raw material S. That is, the reference numerals in the drawings shown in this embodiment are different from those in the standard raw material loading tank 13. Figure 1 The same reference numerals in the accompanying drawings indicate components that perform the same function.

[0031] According to one aspect of this disclosure, a fine material filling structure may include a supply pipe 100, which is inserted and installed facing the interior of the furnace body 11 to fill the furnace body 11 with powdered raw material S.

[0032] One end of the supply pipe 100 can be connected to the raw material hopper 110 located outside the furnace body 11, and the other end of the supply pipe 100 can be located near the molten iron pool 15. At this time, a nozzle unit 120 for discharging powdered raw material S is provided at the distal end of the other end of the supply pipe 100. This supply pipe 100 is vertically positioned from the raw material hopper 110 toward the molten iron pool 15. Here, the molten iron pool 15 is a pool for storing molten iron formed by melting raw materials, and a slag layer 16 is formed on the molten iron.

[0033] The position of the distal end of the supply pipe 100 discharging the powdered raw material S must be adjusted to address the problem of the powdered raw material S escaping into the exhaust gas pipe 14 due to heat within the electric furnace 10 and the suction force of the exhaust gas pipe 14 when it is being loaded into the furnace body 11. This is to reduce the loss rate of the powdered raw material S discharged into the exhaust gas pipe 14 along with the exhaust gas. The height of the distal end of this supply pipe 100 can be set according to the maximum size (diameter) of the powdered raw material S. At this time, the powdered raw material S can be prepared as direct reduced iron (DRI) or hot-pressed iron (HBI), as well as limestone and carbonaceous materials in powder form.

[0034] More specifically, the height of the distal end of the supply pipe 100 refers to the distance spaced upwards from the molten iron pool 15, with reference to the molten iron pool 15. (See reference...) Figure 4 The height from the molten iron pool 15 to the distal end of the supply pipe 100 can be determined as "nozzle unit height / maximum diameter of raw material". That is, the distance between the molten iron pool 15 and the distal end of the supply pipe 100 is preferably set to a value less than 100 times the maximum size of the powdered raw material. As described above, the height of the distal end (nozzle unit) of the supply pipe 100 can be set according to the maximum diameter of the raw material. For example, when the diameter of the largest raw material in the powdered raw material S is 10 mm, the distance between the supply pipe 100 and the molten iron pool 15 can be set to 1000 mm (1 m).

[0035] This is because, such as Figure 4 As shown, when the distance between the molten iron pool 15 and the distal end of the supply pipe 100 is greater than or equal to 100 times, the amount of powdered raw material drawn into and discharged into the exhaust pipe 14 increases, thereby increasing the raw material loss rate. Conversely, when the distance between the molten iron pool 15 and the distal end of the supply pipe 100 is less than 100 times, the raw material loss rate is 0%, thus eliminating the need to unnecessarily place the supply pipe 100 close to the molten iron pool 15. This is because if the supply pipe 100 is unnecessarily placed close to the molten iron pool 15, the probability of damage to the supply pipe 100 due to high temperature (heat deformation, etc.) increases. Therefore, it is preferable that the loss rate of the powdered raw material S is set to be within the desired target value (0%). Therefore, it should be understood that the height of the supply pipe 100 also meets the requirement of preventing damage to the supply pipe 100 installed in the high-temperature electric furnace 10.

[0036] Meanwhile, since the supply pipe 100 is located close to the high-temperature slag and melt, the supply pipe 100 can be formed of graphite or ceramic material that can withstand high temperatures without melting. More specifically, it is preferred that the nozzle unit 120 is formed of graphite or ceramic material that can withstand high temperatures, wherein the nozzle unit 120 is formed at the distal end of the supply pipe 100.

[0037] A nozzle unit 120 is formed at the distal end portion of the supply pipe 100 and may be configured to have at least two or more nozzle holes 121. Powdered raw material S can be discharged through each nozzle hole 121. This is to prevent the raw material S from accumulating in one place when it is filled through the nozzle unit 120. This is because if the powdered raw material S accumulates in one place and the portion exposed to the outside increases, the powdered raw material S is more prone to re-oxidation. Therefore, by injecting the powdered raw material S through multiple nozzle holes 121 for widespread diffusion, the re-oxidation characteristic can be minimized. Furthermore, by filling the raw material near the molten iron pool 15 using the nozzle unit 120, the time exposed to the outside can be reduced.

[0038] The diameter of the nozzle orifice 121 of this nozzle unit 120 can be formed to a predetermined size. This is because if the size of the nozzle unit 120 is formed too small, the nozzle orifice 121 will become clogged, making it impossible to smoothly inject the powder raw material S. (Refer to...) Figure 5 The diameter (mm) of the nozzle orifice 121 can be determined as "nozzle orifice diameter / maximum diameter of raw material". That is, the diameter of the nozzle orifice 121 is preferably formed to be 10 times or more the maximum size of the powdered raw material. This diameter of the nozzle orifice 121 is set based on the clogging rate of the nozzle orifice 121, and this is because when the nozzle orifice 121 is 10 times or more the maximum diameter of the raw material, the nozzle clogging rate is less than 10%, which is included in the desired target value. Therefore, as... Figure 5 As shown, the nozzle orifice 121 is preferably formed to have a diameter 10 to 20 times that of the maximum diameter of the raw material.

[0039] Simultaneously, the supply pipe 100 can be configured to inject an inert gas, such as argon, carbon dioxide, or nitrogen, along with the powdered raw material S. For example, the supply pipe 100 can be connected to a pneumatic delivery pipe (not shown) that provides the inert gas. Therefore, the inert gas can be configured to exit through any one of the plurality of nozzle orifices 121.

[0040] Additionally, the supply pipe 100 can be configured to be offset from the electrode rod 1 along the wall surface (refractory layer) of the furnace body 11. In this case, at least one electrode rod 1 is provided in the electric furnace 10, and typically three three-phase (RST) electrode rods 1a, 1b, and 1c are provided and used. These three-phase electrode rods 1a, 1b, and 1c originate from the center of the furnace body 11 (refer to...). Figure 6 The "C" in the diagram is set radially. (Refer to...) Figure 6The supply pipe 100 can be arranged along the furnace wall direction of the furnace body 11 to exceed 2 / 3 of the length A of the circular track O connecting the centers of the multiple electrode rods 1a, 1b, and 1c. Furthermore, the supply pipe 100 can be arranged at an angle between 10° and 60° relative to an imaginary line connecting the center C of the furnace body 11 and the centers of each electrode rod 1a, 1b, and 1c. This is to prevent the supply pipe 100 from thermal deformation due to the arc heat generated when the raw material is melted by receiving electricity. Additionally, this is because if raw material is injected into the same location as the electrode rods, the raw material will contact the electrode rods 1a, 1b, and 1c, causing a short circuit, and the power supply may become unstable.

[0041] At the same time, despite Figure 6 The diagram illustrates and describes the arrangement of three electrode rods 1a, 1b, and 1c, but this disclosure is not limited thereto, and one or more electrode rods can be arranged in a straight line and used. For example, when one electrode rod 1 is provided, the supply pipe 100 can be positioned between the electrode rod 1 and the furnace wall, but closer to the furnace wall than the electrode rod 1, to inject powder raw materials. Alternatively, when multiple electrode rods are arranged in a straight line, the supply pipe 100 can be configured to be positioned at a location exceeding 2 / 3 of the distance between the center of one electrode rod and the center of the adjacent electrode rod. In this case, the supply pipe 100 can be positioned between the electrode rods.

[0042] As described above, a method for producing molten iron in an electric furnace 10 provided with at least one electrode rod 1 by means of a fine material loading structure according to one aspect of the present disclosure will be briefly described.

[0043] First, raw materials such as waste are loaded into the furnace body 11, and fluxes such as lime and silica sand are loaded at the same time.

[0044] Next, a three-phase AC voltage is applied to the electrode rod 1 to form an electric arc between the electrode rod 1 and the scrap, thereby melting the raw material. As a result, a pool of molten iron 15 is formed in the furnace body 11, and a slag layer 16 is formed on the pool of molten iron 15.

[0045] When the molten iron pool 15 is formed, powdered raw materials (DRI, limestone, coal, etc.) are injected along with an inert gas through the supply pipe 100. At this time, the loading rate of the powdered raw material S is controlled to minimize exposure to the oxidizing atmosphere. For example, if the rate at which the powdered raw material S is injected through the supply pipe 100 is fast, the input amount also increases. This is because the rate at which the powdered raw material S dissolves via the electrode rod 1 is slower, thereby increasing the exposure time of the powdered raw material S. Therefore, by controlling the supply rate and quantity of the powdered raw material S according to the rate at which it dissolves via the electrode rod 1, re-oxidation can be minimized.

[0046] As described above, while continuously supplying powdered raw material S, electricity is supplied to electrode rod 1, causing the powdered raw material S to undergo a melting and reduction reaction, thereby producing molten iron with a saturated carbon concentration.

[0047] At the same time, while monitoring and adjusting the operation of the electric furnace 10, the power input value of the electrode rod 1, the flow rate of the powder raw material, and the position of the input port (height and setting position of the supply pipe) can be adjusted.

[0048] As described above, although the present invention has been described with reference to defined embodiments and accompanying drawings, the present invention is not limited thereto, and those skilled in the art to which this invention pertains can make various modifications and changes within the technical spirit of the present invention and the equivalent scope of the appended claims.

Claims

1. A fine material loading structure for an electric furnace, the fine material loading structure comprising a furnace body for receiving raw materials, a top for opening and closing an upper portion of the furnace body, at least one electrode rod inserted into the furnace body through the top, and a waste gas duct disposed in the top, the fine material loading structure comprising: A supply pipe is connected to a raw material hopper that supplies powdered raw materials and fills the furnace body with the powdered raw materials. The supply pipe is vertically arranged from the raw material hopper located in the upper part of the furnace body toward the molten iron pool, and... The height of the distal end from the molten iron pool to the supply pipe from which the powdered raw material is discharged is set to a value less than 100 times the maximum size of the powdered raw material, such that the loss rate of the powdered raw material discharged from the supply pipe is included in the desired target value.

2. The fine material loading structure for an electric furnace according to claim 1, in, The nozzle unit formed at the distal end portion of the supply tube is configured to have at least two or more nozzle orifices.

3. The fine material filling structure for an electric furnace according to claim 2, in, The diameter of the nozzle orifice is formed to be 10 times or more the maximum size of the powder raw material.

4. The fine material loading structure for an electric furnace according to claim 1, in, The supply tube is made of graphite or ceramic material.

5. The fine material loading structure for an electric furnace according to claim 1, in, The supply pipe is configured to inject inert gas together with the powdered raw material.

6. The fine material loading structure for an electric furnace according to claim 1, in, The supply pipe is arranged along the furnace wall of the furnace body in a manner that exceeds 2 / 3 of the length of the circular track from the center of the furnace body to the center of the multiple electrode rods.

7. The fine material loading structure for an electric furnace according to claim 1, in, The supply pipe is arranged at an angle between 10° and 60° relative to an imaginary line connecting the central portion of the furnace body and the center of the electrode rod.

8. The fine material loading structure for an electric furnace according to claim 1, in, When multiple electrode rods are set up and arranged in a straight line The supply tube is positioned at a location more than 2 / 3 of the distance between the center of one electrode rod and the center of the adjacent electrode rod.

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