Fine raw material feeding structure of electric arc furnace

Abstract

A fine raw material feeding structure of an electric arc furnace is disclosed. According to one aspect of the present invention, a fine raw material feeding structure of an electric arc furnace, which comprises: a furnace body for accommodating a raw material; a roof for opening / closing the upper portion of the furnace body; at least one electrode rod inserted into the furnace body through the roof; and an exhaust gas duct provided in the roof, can be provided, the structure comprising a supply pipe connected to a raw material hopper for supplying the powdered raw material, so as to feed the powdered raw material into the furnace body, wherein the supply pipe is vertically disposed toward a molten iron bath from the raw material hopper positioned above the furnace body, and the height from the molten iron bath to the end of the supply pipe for discharging the powdered raw material has a value of less than 100 times the maximum size of the powdered raw material, so that the loss rate of the powdered raw material discharged from the supply pipe is included in a required target value.

Description

Structure for feeding fine raw materials into an electric furnace

[0001] The present invention relates to a raw material input structure, and more particularly, to a fine raw material input structure of an electric furnace that inputs fine raw material in the form of powder into an electric furnace without loss.

[0002] Typically, electric arc furnaces (EAFs) utilize the arc heat generated by electrodes to melt raw materials, primarily scrap. Conversely, smelting-reduction electric furnaces are designed to produce molten iron directly from powdered raw materials. To produce high-quality steel, smelting-reduction electric furnaces typically use either direct reduced iron (DRI) or hot briquetted iron (HBI). Furthermore, to achieve the desired molten iron composition, powdered limestone and coal are often added to the furnace, in addition to DRI or BHI. Limestone acts as a flux, helping to remove impurities from the steel, while coal is added to the molten iron to increase the carbon content of the resulting steel.

[0003] Figure 1 illustrates a smelting reduction type electric furnace that produces molten iron by supplying powdered raw materials.

[0004] Referring to Fig. 1, an electric furnace (10) includes a furnace body (11), a loop (12) for opening and closing the upper portion of the furnace body (11), an electrode rod (1) inserted into the furnace body (11) through an electrode rod hole formed in the loop (12), a raw material charging chute (13) for charging powdered raw material (S) by contacting the loop (12), and an exhaust gas duct (14) for discharging exhaust gas generated when melting the powdered raw material (S).

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

[0006] When powdered raw material (S) is fed into the inside of the furnace body (11) through the raw material feeding chute (13), power is supplied to the electrode rod (1) to cause melting and reduction reactions.

[0007] However, when the powdered raw material (S) mentioned above is fed from the top of the furnace body (11) to produce molten iron, a problem occurs in which the powdered raw material (S) rises due to the heat inside the electric furnace (10) and the suction force of the exhaust gas duct (14) and escapes to a dust collector (not shown) through the exhaust port in the direction of arrow B together with the gas generated inside the electric furnace (10). As a result, loss of raw material occurs, which not only reduces productivity but also increases the cost of raw material. In addition, the duct and dust collector become clogged by the raw material that escapes through the exhaust gas duct (14), which shortens the cycle of repair and replacement.

[0008] One aspect of the present invention is to provide a structure for feeding fine raw materials into an electric furnace, which can minimize the loss of raw materials occurring during the production of molten iron.

[0009] According to one aspect of the present invention, there is provided a pulverized raw material input structure of an electric furnace including a furnace body for receiving raw materials, a loop for opening and closing the upper part of the furnace body, at least one electrode rod inserted into the furnace body through the loop, and an exhaust gas duct provided in the loop, the pulverized raw material input structure of an electric furnace including a supply pipe for inputting the powdered raw material into the furnace body by being connected to a raw material hopper for supplying powdered raw material, and the supply pipe is vertically arranged from the raw material hopper located at the upper part of the furnace body toward a molten iron bath, and the height of the supply pipe for discharging the powdered raw material from the molten iron bath to the end thereof is set to have a value less than 100 times the maximum size of the powdered raw material so that the loss rate of the powdered raw material discharged from the supply pipe is included in a required target value.

[0010] The nozzle portion formed at the end of the above supply pipe may be provided to have at least two nozzle holes.

[0011] The diameter of the above nozzle hole can be formed to be at least 10 times the maximum size of the powder raw material.

[0012] The above supply pipe may be made of graphite or ceramic material.

[0013] The above supply pipe may be arranged to inject an inert gas together with the above powder raw material.

[0014] The above supply pipe may be provided in the direction of the furnace wall of the furnace body so as to exceed 2 / 3 of the length from the center of the furnace body to the circular track connecting the centers of the plurality of electrode rods.

[0015] The above supply pipe may be arranged to be arranged between 10° and 60° from an imaginary line connecting the center of the body and the center of the electrode rod.

[0016] When the above electrode rods are provided in multiple pieces and arranged in a row, the supply pipe may be arranged to be placed at a position exceeding 2 / 3 of the distance between the centers of the electrode rods.

[0017] A structure for inputting finely divided raw materials into an electric furnace according to one embodiment of the present invention has the effect of minimizing the loss of raw materials occurring during the production of molten iron, thereby improving the yield and quality of the final product.

[0018] Additionally, it can improve the efficiency of electric furnace equipment, reducing operating costs and has the effect of being used in various steel manufacturing applications.

[0019] Figure 1 is a drawing showing a conventional melting reduction type electric furnace.

[0020] FIG. 2 is a drawing showing a melting reduction type electric furnace to which a fine raw material input structure according to one embodiment of the present invention is applied.

[0021] FIG. 3 is a drawing showing a nozzle section of a supply pipe provided in a fine powder raw material input structure according to one embodiment of the present invention.

[0022] Figure 4 is a graph showing the relationship between the loss rate of raw materials according to the arrangement position of the supply pipe according to one embodiment of the present invention.

[0023] Figure 5 is a graph showing the relationship between the size of a nozzle hole formed in a supply pipe and the nozzle clogging rate according to one embodiment of the present invention.

[0024] FIG. 6 is a drawing showing a state in which a supply pipe according to one embodiment of the present invention is arranged relative to an electrode rod.

[0025] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided to sufficiently convey the spirit of the present invention to those skilled in the art. The present invention is not limited to the embodiments presented herein and may be embodied in other forms. To clarify the present invention, the drawings may omit portions irrelevant to the description, and the sizes of components may be slightly exaggerated to facilitate understanding.

[0026] FIG. 2 is a drawing showing a melting reduction type electric furnace to which a fine raw material input structure according to one embodiment of the present invention is applied, FIG. 3 is a drawing showing a nozzle part of a supply pipe provided in a fine raw material input structure according to one embodiment of the present invention, FIG. 4 is a graph showing the relationship between a raw material loss rate according to an arrangement position of a supply pipe according to one embodiment of the present invention, FIG. 5 is a graph showing the relationship between a size of a nozzle hole formed in a supply pipe according to one embodiment of the present invention and a nozzle clogging rate, and FIG. 6 is a drawing showing a state in which a supply pipe according to one embodiment of the present invention is arranged with respect to an electrode rod.

[0027] Referring to FIGS. 2 to 6, a powdered raw material input structure according to one aspect of the present invention is a facility for inputting a powdered raw material (S) into a melting reduction type electric furnace (hereinafter referred to as an “electric furnace”). Here, the electric furnace (10) is provided with the same configuration as the electric furnace (10) described above in the background technology of the invention. However, there is a difference from the conventional raw material loading chute (13) for inputting the powdered raw material (S). That is, the same reference numerals in the drawings illustrated in this embodiment and in the drawings illustrated in FIG. 1 indicate members having the same function.

[0028] A powder raw material input structure according to one aspect of the present invention may include a supply pipe (100) that is inserted and installed so as to face the inside of the furnace body (11) and inputs powder raw material (S) into the inside of the furnace body (11).

[0029] The supply pipe (100) may be provided such that one end is connected to the raw material hopper (110) provided on the outside of the furnace body (11), and the other end is provided close to the molten iron bath (15). At this time, a nozzle part (120) for discharging powdered raw material (S) is provided at the other end of the supply pipe (100). This supply pipe (100) may be vertically arranged from the raw material hopper (110) toward the molten iron bath (15). Here, the molten iron bath (15) is a pool in which molten iron formed by melting raw materials is stored, and a slag layer (16) is formed on the molten iron.

[0030] In order to solve the problem that the powder raw material (S) escapes into the exhaust gas duct (S) due to the heat inside the electric furnace (10) and the suction force of the exhaust gas duct (14) when the powder raw material (S) is fed into the furnace body (11), the position of the end of the supply pipe (100) through which the powder raw material (S) is discharged must be adjusted. This is to reduce the loss rate of the powder raw material (S) discharged into the exhaust gas duct (14) together with the exhaust gas. The height of the end of the supply pipe (100) can be set according to the maximum size (diameter) of the powder raw material (S). At this time, the powder raw material (S) can be prepared as direct reduced iron (DRI), hot briquetted iron (HBI), limestone in powder form, and carbon ash.

[0031] More specifically, the height of the end of the supply pipe (100) refers to the distance spaced upward from the molten iron bath (15) based on the molten iron bath (15). Referring to FIG. 4, the height from the molten iron bath (15) to the end of the supply pipe (100) can be determined as “nozzle height / maximum raw material diameter.” That is, it is preferable that the distance between the molten iron bath (15) and the end of the supply pipe (100) has a value less than 100 times the maximum size of the powdered raw material. The height setting of the end (nozzle) of the supply pipe (100) can be set according to the maximum raw material diameter, as described above. For example, when the diameter of the largest raw material among the powdered raw materials (S) is 10 mm, the distance between the supply pipe (100) and the molten iron bath (15) can be set to 1,000 mm (1 m).

[0032] This is because, as shown in Fig. 4, when the distance between the molten iron bath (15) and the end of the supply pipe (100) is 100 times or more, the amount of powder raw material sucked into the exhaust gas duct (14) and discharged increases, thereby increasing the raw material loss rate. In addition, when the distance between the molten iron bath (15) and the end of the supply pipe (100) is less than 100 times, the raw material loss rate is the same as 0%, so there is no need to unnecessarily place the supply pipe (100) close to the molten iron bath (15). This is because, if the supply pipe (100) is unnecessarily close to the molten iron bath (15), the probability of damage (thermal deformation, etc.) of the supply pipe (100) due to high temperature increases. Therefore, it is preferable that the loss rate of the powder raw material (S) be set to be included in the required target value (0%). Accordingly, the height of the supply pipe (100) should be understood to also satisfy the requirement for preventing damage to the supply pipe (100) provided within the high-temperature electric furnace (10).

[0033] Meanwhile, the supply pipe (100) may be formed of graphite or ceramic material that can withstand high temperatures without melting, as it is positioned in close proximity to high-temperature slag and molten material. More specifically, it is preferable to form the nozzle portion (120) formed at the end of the supply pipe (100) of graphite or ceramic material that can withstand high temperatures.

[0034] The nozzle unit (120) is formed at the end of the supply pipe (100) and may be provided with at least two nozzle holes (121). The powder raw material (S) may be discharged through each nozzle hole (121). This is to prevent the powder raw material (S) from accumulating in one place when injected through the nozzle unit (120). This is because if the powder raw material (S) accumulates in one place and a large portion is exposed to the outside, it is easy for it to be re-oxidized. Accordingly, by injecting the powder raw material (S) through a plurality of nozzle holes (121), it is possible to minimize re-oxidization by allowing it to spread widely. In addition, by injecting the raw material close to the molten iron bath (15) through the nozzle unit (120), it is possible to reduce the time it is exposed to the outside.

[0035] The diameter of the nozzle hole (121) of the nozzle part (120) can be formed to have a set size. This is because if the size of the nozzle part (120) is formed too small, the nozzle hole (121) will be blocked, making it difficult to smoothly feed the powder raw material (S). Referring to FIG. 5, the diameter (mm) of the nozzle hole (121) can be determined as “nozzle hole diameter / maximum raw material diameter.” That is, it is preferable that the diameter of the nozzle hole (121) be formed to have a value that is 10 times or more the maximum size of the powder raw material. This is because the diameter of the nozzle hole (121) is set according to the nozzle hole (121) blockage rate, and when the nozzle hole (121) is 10 times or more the maximum raw material diameter, the nozzle blockage rate is less than 10%, which is included in the required target value. Accordingly, as shown in Fig. 5, it is preferable that the nozzle hole (121) be formed to have 10 to 20 times the maximum diameter of the raw material.

[0036] Meanwhile, the supply pipe (100) may be configured to inject an inert gas, such as argon, carbon dioxide, or nitrogen gas, together with the powdered raw material (S). For example, the supply pipe (100) may be connected to a gas supply pipe (not shown) that supplies the inert gas. Accordingly, the inert gas may be discharged through any one of the plurality of nozzle holes (121).

[0037] In addition, the supply pipe (100) may be arranged to be biased toward the wall surface (refractory layer) of the furnace body (11) from the electrode rod (1). At this time, at least one electrode rod (1) is provided in the electric furnace (10), and typically three three-phase (RST) electrode rods (1a, 1b, 1c) are provided and used. These three-phase electrode rods (1a, 1b, 1c) are arranged radially from the center of the furnace body (11) (see 'C' in FIG. 6). Referring to FIG. 6, the supply pipe (100) may be arranged in the direction of the furnace wall of the furnace body (11) so as to exceed 2 / 3 of the length (A) from the center (C) of the furnace body (11) to the circular track (O) connecting the centers of the plurality of electrode rods (1a, 1b, 1c). In addition, the supply pipe (100) may be arranged to be arranged between 10° and 60° from the imaginary line connecting the center (C) of the furnace body (11) and the center of each electrode rod (1a, 1b, 1c). This is to prevent the supply pipe (100) from being thermally deformed by the arc heat generated when the raw material is melted by supplying power. In addition, this is because if the raw material is fed to the same position as the electrode rod, a short circuit may occur when the raw material comes into contact with the electrode rod (1a, 1b, 1c), which may cause the power supply to become unstable.

[0038] Meanwhile, although FIG. 6 illustrates and describes three electrode rods (1a, 1b, 1c), the present invention is not limited thereto, and one electrode rod or multiple electrode rods may be arranged in a row and used. For example, when one electrode rod (1) is arranged, the supply pipe (100) may be positioned between the electrode rod (1) and the furnace wall, but may be positioned closer to the furnace wall than the electrode rod (1) so that the powdered raw material may be introduced. In addition, when multiple electrode rods are arranged in a row, the supply pipe (100) may be arranged at a position exceeding 2 / 3 of the distance between the center of the electrode rod and the center of the neighboring electrode rod. At this time, the supply pipe (100) may be arranged between the electrode rods.

[0039] In this way, a method for producing molten iron through a fine raw material input structure according to one aspect of the present invention in an electric furnace (10) provided with at least one electrode rod (1) will be briefly described.

[0040] First, raw materials such as scrap are loaded into the furnace body (11) and flux such as lime and silica is loaded at the same time.

[0041] Next, a three-phase alternating current voltage is applied to the electrode (1) to form an arc between the electrode (1) and the scrap, thereby melting the raw material. As a result, a molten iron bath (15) is formed within the furnace body (1), and a slag layer (16) is formed on top of it.

[0042] When the molten iron bath (15) is formed, powder raw materials (DRI, limestone, carbon, etc.) are fed together with an inert gas through the supply pipe (100). At this time, the feeding speed of the powder raw materials (S) is controlled so as to minimize exposure to an oxidizing atmosphere. For example, if the speed of the powder raw materials (S) fed through the supply pipe (100) is fast, the feeding amount also increases. This is because the exposure time of the powder raw materials (S) increases as the speed of dissolving the powder raw materials (S) through the electrode (1) becomes slow. Accordingly, the feeding speed and feeding amount of the powder raw materials (S) can be controlled in accordance with the speed of dissolving the powder raw materials (S) through the electrode (1) to minimize re-oxidation.

[0043] As described above, by continuously supplying powder raw material (S) and supplying power to the electrode rod (1), melting and reduction reactions of the powder raw material (S) occur, thereby producing molten iron having a saturated carbon concentration.

[0044] Meanwhile, while monitoring and adjusting the operation of the electric furnace (10), it is possible to adjust the power input value for the electrode rod (1), the flow rate of the powder raw material, and the position of the input port (height and arrangement position of the supply pipe).

[0045] As described above, although the present invention has been described by limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

Claims

1. In a structure for feeding fine raw materials into an electric furnace, which comprises a body for receiving raw materials, a loop for opening and closing the upper part of the body, at least one electrode rod inserted into the body through the loop, and an exhaust gas duct provided in the loop, It includes a supply pipe that is connected to a raw material hopper that supplies powder raw materials and injects the powder raw materials into the inside of the furnace, The above supply pipe is arranged vertically from the raw material hopper located at the upper part of the furnace body toward the molten iron bath, An electric furnace pulverized raw material input structure in which the height of the end of the supply pipe discharging the powder raw material from the molten iron bath is set to be less than 100 times the maximum size of the powder raw material so that the loss rate of the powder raw material discharged from the supply pipe is within a required target value.

2. In paragraph 1, A structure for feeding fine powder raw materials into an electric furnace, wherein a nozzle part formed at the end of the above supply pipe has at least two nozzle holes.

3. In paragraph 2, An electric furnace fine powder raw material input structure formed so that the diameter of the nozzle hole is at least 10 times the maximum size of the powder raw material.

4. In paragraph 1, The above supply pipe is a structure for feeding fine raw materials into an electric furnace made of graphite or ceramic material.

5. In paragraph 1, The above supply pipe is a fine raw material input structure of an electric furnace provided to input an inert gas together with the above powder raw material.

6. In paragraph 1, The above-mentioned supply pipe is an electric furnace pulverized raw material input structure provided in the direction of the furnace wall of the furnace body so as to exceed 2 / 3 of the length from the center of the furnace body to the circular track connecting the centers of the plurality of electrode rods.

7. In paragraph 1, A structure for feeding fine raw material into an electric furnace, wherein the supply pipe is arranged at an angle of 10° to 60° from an imaginary line connecting the center of the body and the center of the electrode rod.

8. In paragraph 1, When the above electrode rods are prepared in multiple pieces and arranged in a row, A structure for feeding fine raw material into an electric furnace, wherein the supply pipe is arranged at a position exceeding 2 / 3 of the distance between the centers of the electrode rods and the electrode rods.

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