JPH07332862A - Dc electric furnace - Google Patents

Abstract

PURPOSE:To provide a DC electric furnace in the operation of which preheated metal material is fed to the middle inside the furnace body simultaneously with preheating of the metal material by exhaust gas at an increased efficiency so that the efficiency of electric energy to melt metal material can be increased. CONSTITUTION:In the middle inside a furnace body 1 an upper carbon electrode 3 is placed, designed to be lowered and lifted through a through hole 6 formed at a point in a preheating tower 5 which is provided above a furnace lid 4 and has a part leaning. The lower end of the preheating tower 5 is positioned in the middle of the furnace body 1. The preheating tower 5 has a charging hole inside through which metal material 7 is fed and an exhaust-gas duct 10 by which the exhaust gas is conveyed to dust-collecting equipment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC electric furnace used for melting metal materials, refining molten metal, and the like.

[0002]

2. Description of the Related Art As an electric furnace for refining, an electric current is passed 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 make a metal material. DC electric furnace for melting and refining molten metal, and AC electric for melting metal materials and refining molten metal by passing an electric current between three electrodes placed above the molten metal charged in the furnace. The furnace is known. In this type of electric furnace operation, the system that uses the exhaust gas is to place a preheating tank between the electric furnace and the dust collecting equipment, and load the metal material together with the bucket into this preheating tank. It was common to preheat.

However, the exhaust gas duct between the electric furnace and the preheating tank is water-cooled because high-temperature gas generated from the electric furnace passes through, and the temperature of the exhaust gas reaching the preheating tank is lowered by the amount of water cooling. Therefore, the heat of the exhaust gas is not efficiently used for preheating the metal material, resulting in a large loss in terms of thermal efficiency. In addition, white smoke and odor generated when the preheated metal material is transferred to the electric furnace together with the bucket have been a serious problem in terms of working environment.

Therefore, various methods have been proposed in which the heat of the exhaust gas is efficiently used for preheating the metal material, and the preheated metal material is charged into the electric furnace without being transported from the preheating tank to the electric furnace. For example, in Japanese Patent Laid-Open No. 3-505625, a metal material is preheated in a preheating tower formed on a furnace lid and a part of a furnace body, and a preheated metal material stored in the preheating tower is used. An electric furnace characterized by being dropped and charged naturally is disclosed. However, in this case, during the so-called refining period after the metallic material stored in the preheating tower provided on the furnace lid naturally falls and melts, the metallic material disappears in the preheating tower and the metallic material is removed by the heat of the exhaust gas. There was no preheating, so there was still a problem in terms of thermal efficiency.

Therefore, as a technique of a method for solving this problem, for example, in Japanese Patent Laid-Open No. 5-500263, two sets of electric furnaces are arranged, and the metallic material stored in the preheating tower of the electric furnace which is energized naturally. After dropping and melting, another method is proposed in which the other metal material is stored in a preheating tower and the exhaust gas is introduced into an electric furnace that is on standby to preheat the metal material and improve the thermal efficiency. Further, in JP-A-4-309789, the pretropical zone is formed only by the preheating tower, and a door is provided in the preheating tower.
A method has been proposed in which the metal material can be always stored in the preheating tower so that the heat of the exhaust gas in the refining period can be effectively used.

[0006]

Electric energy occupies most of the energy for melting the metal material in the electric furnace, and in the direct current electric furnace, it is the heat of the arc generated from the upper carbon electrode. When considering the energy efficiency in melting the metal material, the arc that is the energy source is arranged in the center of the furnace body as much as possible, that is, the upper carbon electrode is arranged, and the charging portion of the metal material to be melted is set in the furnace body. It is preferable to make the arc as central as possible and to ignite an arc from the upper carbon electrode at the central part of the metal material so as to melt the circumference uniformly. This is a big advantage of a DC electric furnace that requires only one upper carbon electrode, and is superior in energy efficiency to an AC electric furnace that requires three upper carbon electrodes. The same is of course true if the material is preheated.

However, JP-A-3-505625, JP-A-5-500263 and JP-A-4-309.
In the case of Japanese Patent No. 789, the preheating tower is installed on the side wall portion of the furnace body, so that the preheated metal material is charged only in the side wall portion of the furnace body, and the metal material is not charged. The side wall is not always used for melting the metal material that is heated by arc heat all the time, which leads to a decrease in energy efficiency.Because the metal material is charged only in the part away from the upper carbon electrode. However, there is a problem that the dissolution rate becomes slower than that of the method of disposing the upper carbon electrode in the central portion of the metal material to cause a decrease in energy efficiency.

In view of the above, the present invention makes it possible to increase the thermal efficiency of the metallic material by the exhaust gas, and at the same time, to charge the preheated metallic material in the central portion of the furnace body to enhance the melting electric energy efficiency of the metallic material. The purpose is to provide an electric furnace.

[0009]

In order to solve the above problems, a direct current electric furnace of the present invention is a direct current electric furnace having a preheating tower having a movable door inside, and the preheating tower is made of a metal material. And an upper part for preheating, and a lower part inclined so that the drop port of the preheated metal material is located in the furnace central part, and the lower part is formed in the central part of the furnace lid. It is characterized in that a through-hole is formed in the lower portion located in the center of the furnace body so as to communicate with the section, and a carbon electrode which can be raised and lowered is disposed in the through-hole.

[0010]

In the present invention, since the preheating tower having the door provided inside is placed on the furnace lid, the metal material can be always stored in the preheating tower and the heat efficiency of the exhaust gas is improved while the preheated metal is kept. Material can be charged into the central part of the furnace body from the lower end of the preheating tower located in the central part of the furnace lid, and the upper carbon electrode arranged in the central part of the furnace body is provided with the through hole provided in the inclined preheating tower. It is possible to raise and lower it further and melt it from the central portion of the metallic material charged into the furnace.

[0011]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an overall vertical sectional view of a DC electric furnace according to the present invention. A furnace bottom electrode 2 is arranged in the lower part of the furnace body 1, and an upper carbon electrode 3 is arranged in the central part of the furnace body 1 in the upper part. A preheating tower 5 having an inclined portion is provided on the furnace lid 4, and a through hole 6 through which the upper carbon electrode 3 moves up and down is provided in a part of the inclined portion of the preheating tower 5. A movable door 8 for holding the metal material 7 is installed inside the preheating tower 5, and a charging port 9 for charging the metal material 7 into the preheating tower 5 and a dust collecting facility for exhaust gas are provided above (Fig. An exhaust gas duct 10 is provided which is connected to (not shown).

High-temperature exhaust gas generated during melting and refining of the metal material 7 passes through the preheating tower 5 and is sent to the dust collecting equipment through the exhaust gas duct 10. At this time, the metal material 7 in the preheating tower 5 is efficiently preheated by the high temperature exhaust gas. When the heating of the metallic material 7 charged in the furnace body 1 is completed and the metallic material 7 in the preheating tower 5 is charged, the upper carbon electrode 3 is pulled up by an electrode lifting device (not shown), and then the door 8 Open and load. At this time, since the lower end portion of the preheating tower 5 is located in the central portion of the furnace lid 4, the metal material 7 in the preheating tower 5 is charged into the central portion of the furnace body 1. Subsequently, after charging, the door 8 is closed and the upper metal material 7 is received and stored. After the door 8 is closed in this way, the upper carbon electrode 3 is lowered to ignite an arc in the center of the metal material to start melting. Thus, in the present invention, the preheating tower 5
It is possible to charge the metal material 7 preheated by the exhaust gas into the central part of the furnace body 1, and by tilting the lower part of the preheating tower 5, the upper carbon electrode 3 is moved to the central part of the furnace body 1. It is possible to dispose them and move up and down through the through-hole 6 provided in a part of the preheating tower 5.

[0013]

As described above, in the DC electric furnace according to the present invention, while effectively preheating the metal material,
In addition, it enables operations that increase the utilization efficiency of electric energy for melting and refining metal materials, and greatly contributes to reduction of energy cost and improvement of productivity.

[Brief description of drawings]

FIG. 1 shows an overall vertical sectional view of a DC electric furnace according to an embodiment of the present invention.

[Explanation of symbols]

 1 Furnace Body 2 Furnace Bottom Electrode 3 Upper Carbon Electrode 4 Furnace Lid 5 Preheating Tower 6 Through Port 7 Metal Material 8 Door 9 Loading Port 10 Exhaust Duct 11 Arc

Claims (1)

[Claims] 1. A direct current electric furnace having a preheating tower having a movable door inside, wherein the preheating tower stores a metal material,
It consists of an upper part to be preheated and a lower part that is inclined so that the drop port of the preheated metal material is located in the central part of the furnace, and the lower part is connected to the opening formed in the central part of the furnace lid. Further, the direct current electric furnace is characterized in that a through hole is formed in the lower portion, which is located at the center of the furnace body, and a carbon electrode that can be raised and lowered is disposed in the through hole.