JPH05312475A - Continuous scrap charging type arc furnace - Google Patents

Abstract

(57) [Summary] [Objective] The present invention effectively melts scrap that is continuously charged in the furnace, increases the charging speed of scrap, and completely eliminates harmful substances generated during preheating of scrap. The present invention provides a continuous scrap charging type arc furnace to be eliminated. [Structure] An upper furnace body of a portion into which scrap of an arc furnace is continuously charged has a furnace body profile inclined toward the furnace center side, and a branch duct is provided from an exhaust gas duct for discharging gas generated in the furnace, The branch duct is connected to the storage room that houses the scrap transfer device via a fan that increases the gas pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous scrap charging type arc furnace used for melting metal materials, refining molten metal and the like.

[0002]

2. Description of the Related Art As an arc furnace for refining, an electric current is caused to flow between an electrode arranged above a molten metal charged in the furnace and an electrode attached to a furnace wall such as a furnace bottom or a side wall to melt the molten metal. There is known a DC arc furnace for refining the molten metal, and an AC arc furnace for refining the molten metal by passing an electric current between three electrodes arranged above the molten metal charged in the furnace. Most arc furnaces of this type perform batch loading of scrap in buckets, which requires the time to open and close the furnace lid when scrap is loaded, reducing productivity and reducing the amount of heat in the furnace when the furnace lid is opened and closed. Practical application of an arc furnace that disperses into the outside atmosphere and continuously charges scrap in terms of energy efficiency is expected. Therefore, various proposals have been made for this practical use. For example, in Japanese Patent Application Laid-Open No. 61-502899, a charging port for continuously charging scrap into the furnace wall portion of the furnace body is provided. Disclosed is an arc furnace having a structure in which scrap is placed in an exhaust gas duct and is charged into the furnace while preheating with exhaust gas.

[0003]

At this time, if the continuous charging rate of scrap and the melting rate of scrap cannot be balanced, the scrap is piled up in the charging portion of the scrap, which hinders the production. The important point is to increase the scrap dissolution rate. For this reason, it is necessary to increase the scrap dipping ratio in order to increase the heat transfer area between the scrap and the molten metal, which has a large influence on the amount of heat received from the molten metal, which accounts for the majority of the melting heat of the scrap. However, JP-A-61-250289
A furnace body profile in which the depth of the molten metal becomes deeper from the furnace wall portion toward the center portion of the furnace body, as in Japanese Patent Publication No. 9, the so-called furnace bottom shape is an inverted truncated cone shape and the side surface of the furnace body is a vertical cylinder In the arc furnace, the scrap can be charged only in the peripheral furnace wall where the depth of the molten metal is small, and the heat transfer area between the scrap and the molten metal cannot be increased. Has disadvantages,
It was difficult to increase the scrap charging speed. As a method of compensating for this drawback, a method of ejecting the scrap carrier into the arc furnace is conceivable, but it is difficult to secure the function of the scrap carrier because it receives high heat from the arc.

Further, a technique for preheating the scrap with the exhaust gas from the furnace in the process of transporting the scrap by a transport device installed in the exhaust gas duct has been proposed. It has a drawback that the toxic substances such as bad odor and white smoke generated at the part where the scrap is preheated by the low temperature exhaust gas are gradually discharged to the downstream flow of the exhaust gas duct as they are. INDUSTRIAL APPLICABILITY The present invention makes it possible to effectively increase the melting rate of scrap that is continuously charged in the furnace and raise the constraint limit of the scrap charging speed. It is an object of the present invention to provide a continuous scrap-charging type arc furnace capable of completely eliminating the harmful substances that are generated.

[0005]

[Means for Solving the Problems] As a means for achieving the object, a conveying device for continuously charging scrap into a furnace is provided, and the depth of molten metal pool from the furnace wall to the center of the furnace. In a continuous scrap-charging type arc furnace that is deeper toward, position the tip of the transfer device for charging scrap into the furnace at a position midway between the furnace wall of the molten metal pool surface and the upper electrode. The upper furnace body of the arc furnace has a furnace body profile that is inclined toward the center of the furnace so that the upper end of the furnace body is aligned with the lower surface of the tip of the transfer device. Further, a branch duct should be provided from an exhaust gas duct for discharging the gas generated in the furnace, the branch duct should be connected to a storage room for storing a scrap carrier, and a fan for increasing gas pressure should be installed in the branch duct. Also features.

[0006]

According to the present invention, the inclined upper furnace body protects the carrier device from the radiant heat in the furnace, so that the carrier device can be installed so as to protrude to the vicinity of the central portion of the furnace. Since scrap can be charged into a deep-water pool, the surface area of scrap in contact with molten metal can be increased, and the scrap charging position can be made closer to the arc, which is the source of melting energy, so the scrap melting rate can be increased. Can be increased. Also, a portion of the exhaust gas was introduced into the storage room that houses the scrap transport device through a branch duct, and after the scrap was preheated, it was pushed into the arc furnace again to generate high-temperature gas, which was generated during scrap preheating. It is possible to completely pyrolyze harmful substances.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a continuous scrap charging type arc furnace according to the present invention in the case of a DC arc furnace type. It goes without saying that the continuous scrap charging type arc furnace according to the present invention can be applied to an AC arc furnace. The DC arc furnace forms a container with a furnace body 1 and a furnace lid 2, and a furnace bottom electrode 3 penetrates the furnace lid 2 at the lower part of the furnace body main body 1 and an upper part for passing electricity. The electrode 4 is arranged. The inner side of the lower part of the furnace body 1 that contacts the inverted frustoconical molten metal 5 is lined with a refractory material 6, and the upper furnace body 7 that is not in contact with the molten metal 5 is provided with a water cooling box 17. The upper furnace body 7 in the portion where the conveying device 9 for supplying the scrap 8 is arranged is inclined toward the center of the furnace body. As a result, the water-cooled box 1 is prevented from the high heat load, which has been a hindrance when the transfer device 9 is independently pushed into the furnace.
Since the transfer device 9 can be protected by the upper furnace body 7 equipped with 7, the part of the scrap 8 to be charged into the furnace can be the part where the oil retention depth of the molten metal 5 near the center of the furnace is large. That is, the scrap 8 is sufficiently immersed in the molten metal 5, the heat transfer area of the scrap can be increased, and the scrap 8 can be brought closer to the arc 18 of the melting energy source, so that the scrap melting speed can be improved. Becomes

The scrap 8 is continuously charged into the furnace by the transfer device 9 from the charging port 10 attached to the furnace body 1, and the transfer device 9 is stored in the storage chamber 11 and is stored in the storage chamber 11. The chamber 11 has an exhaust gas elbow 12 attached to the furnace lid 2.
Branch duct 1 branched from exhaust gas duct 13 connected to
4 are connected via a fan 15 which increases the gas pressure. As a result, a part of the high-temperature exhaust gas generated in the furnace is pressurized and introduced into the storage chamber 11, preheats the scrap 8 sent by the transfer device 9, and the gas containing the harmful substance generated at the time of preheating is reheated. It is sent into the furnace and the temperature rises. Storage room 11
A sealing device 16 such as an air curtain is installed at the opening of the storage chamber 11 through which the scrap transportation device 9 passes so that the exhaust gas guided to the inside does not leak to the outside air.

[0009]

As described above, in the continuous scrap-charging type arc furnace according to the present invention, scrap can be stably charged into a deep portion of a pool of molten metal, and therefore, contact with molten metal is possible. The surface area of the scrap increases, the melting rate of the scrap can be increased, and the preheating of the scrap to be charged can be carried out by completely suppressing the generation of harmful substances such as bad odors and white smoke due to the preheating. The melting characteristics of scrap can be greatly improved, and it contributes greatly to the improvement of productivity and reduction of energy cost, which are inherent advantages of the continuous scrap charging method.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an example in which the furnace body structure of a continuous scrap charging type arc furnace of the present invention is applied to a DC arc furnace type.

[Explanation of symbols]

 1 Furnace Body 2 Furnace Lid 5 Molten Metal 7 Upper Furnace 8 Scrap 9 Conveyor 11 Storage Room 13 Exhaust Duct 14 Branch Duct 15 Fan

Claims (2)

[Claims] 1. A continuous scrap-charging type arc furnace having a conveying device for continuously charging scrap into the furnace, wherein the depth of the molten metal pool is deeper from the wall of the furnace toward the center of the furnace. In, the tip of the carrier for charging scrap into the furnace is located at an intermediate position between the furnace wall and the upper electrode on the surface of the pool of molten metal, and the upper end of the furnace body is aligned with the lower surface of the tip of the carrier. Scrap charging type arc furnace characterized by having a furnace body profile in which the upper furnace body of the arc furnace is inclined toward the center of the furnace 2. A continuous scrap-charging type arc furnace having a conveying device for continuously charging scrap into the furnace, wherein the depth of the molten metal pool is deeper from the wall of the furnace toward the center of the furnace. In the above, a branch duct is provided from an exhaust gas duct for discharging the gas generated in the furnace, the branch duct is connected to a storage room for storing a scrap carrier, and a fan for increasing gas pressure is installed in the branch duct. A continuous scrap charging type arc furnace.