JPH01167571A - DC arc furnace - Google Patents

Abstract

PURPOSE:To enable execution of wide range dissolution, to shorten a dissolving time, and to improve dissolution efficiency, by a method wherein a furnace bottom electrode is situated in a position where a specified relation is established between the distance of an upper electrode from a core and the distance of the furnace bottom electrode from the core. CONSTITUTION:Three upper electrodes 11 are disposed at a distance A from a core C and at equal intervals in the direction of a periphery centering around the core C. At the furnace bottom part of a furnace body 5 and in a position at a distance (a) from the core C, three furnace bottom electrodes 21 are situated at equal intervals in the direction of a periphery centering around the core C. Since the furnace bottom electrode 21 is situated at a position where a relation between the distance A and the distance (a) is a >=A, a DC arc generated between the electrodes 11 and 21 is brought into a further wider state, even dissolution of a raw material present on the furnace side wall side can be effected rapidly, shortening of a dissolving time can be realized, and dissolution efficiency can be improved.

Description

[Detailed description of the invention] [Purpose of the invention]

(Industrial Application Field) This invention relates to a direct current arc furnace that is mainly used for steelmaking using scrap as a raw material. (Prior Art) Conventionally, in steelmaking, a blast furnace that uses iron ore as a raw material is The converter method is widely adopted as it is suitable for mass production, but on the other hand, electric furnace steelmaking using an arc furnace that uses scrap as raw material is also widely adopted. , an AC arc furnace was used, which gradually became larger and more powerful, leading to the development of the UHP furnace (Ultra High Power Furnace), which became established as an alternative mass-production steelmaking method to the blast furnace-converter method. However, in AC arc furnaces operated by UHP, there is a limit to the reduction of circuit impedance for effective use of high power energy, and the problem of flicker increases.
Since there is a limit to the electrode current density due to the electrode skin effect peculiar to alternating current, there has been some reconsideration of direct current arc furnaces that supply direct current between the upper electrode and the bottom electrode. This DC arc furnace has not made much progress until now due to workability reasons, but in recent years high power capacity AC-D
The development of rectifier equipment for C conversion has greatly contributed to this reconsideration, and the conventionally known DC arc furnace has a furnace cover that covers the top of the furnace body, which consists of furnace walls and a furnace shell. , and also a plurality of upper electrodes connected to, for example, the cathode side of the DC power source are provided at positions separated from the core core by a predetermined distance toward the furnace side wall, and are movable up and down. A plurality of bottom electrodes connected to, for example, the anode side of the DC power source are provided in a coolable manner at a distance smaller than the distance from the reactor core of the upper electrode, that is, at a position closer to the reactor core, and between the upper electrode and the bottom electrode. By generating a direct current arc, the scrap charged into the furnace was heated and melted by the arc. In such a DC arc furnace, the diameter of the electrode is smaller at the same current value than in a conventional AC arc furnace, and due to this smaller diameter, the electrode surface oxidation loss is reduced, and the temperature at the tip of the electrode is lower than in an AC furnace. It is possible to bring about advantages such as a reduction in electrode consumption due to a reduction in graphite sublimation, a reduction in flicker level, and a reduction in arc noise. (Problems to be Solved by the Invention) As described above, conventional DC arc furnaces have several advantages over AC arc furnaces, but as mentioned above, in conventional DC arc furnaces, the bottom electrode It is located closer to the core than the upper electrode, and since DC arc tends to occur in the direction of the core due to the influence of electromagnetic force, it is difficult to melt the portion of the charged material that is close to the core. Although it is carried out at an early stage, it has the problem that the melting of the charged material in the wall part of the furnace (II) tends to be slow.
Further improvements are required. (Purpose of the invention) This invention was made in view of these needs, and it is possible to shorten the melting time of charged raw materials, reduce energy costs, and improve melting efficiency. The purpose is to provide a DC arc furnace.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a DC arc furnace equipped with a plurality of upper electrodes and a plurality of furnace bottom electrodes connected to a DC power source, with respect to the distance glIA of the upper electrode from the core. , the furnace bottom electrode is provided at a position where a distance a from the core of the furnace bottom electrode satisfies the relationship a≧A. (Embodiment) FIG. 1 shows an embodiment of a DC arc furnace according to the present invention. This DC arc furnace 1 consists of pillars 3 and 4 installed on a foundation 2.
The furnace body 5 is supported by
A furnace lid 6 is disposed in the furnace, and this furnace lid 6 is suspended by a support 7 and can be raised and lowered and rotated. In addition, it penetrates this reactor lid 6 and is placed at a distance MA from the reactor core C at equal intervals (
Three upper electrodes 11 made of, for example, graphite electrodes are arranged at 120° intervals. These upper electrodes 11 are each supported by an electrode pole 7 12 and an electrode support arm 13, and can be raised and lowered by an electrode lifting mechanism 14. Further, the upper electrode 11 has an electrode bus bar 16 . Flexible wire 17
In this embodiment, the DC power supply is connected to the cathode side via the secondary side bus bar 18. Furthermore, the bottom part of the reactor body 5 has a distance of 1 ll from the reactor core C.
At point Ia, three bottom electrodes 21 made of conductive metal, for example, are arranged at equal intervals (120° intervals) in the circumferential direction centering on the core C, and the distance in this case is a is the distance 1liIA of the upper electrode 11 from the core
, the relationship is set such that a≧A, that is,
The electrode pitch circle of the bottom electrode 21 is made to be the same as or larger than the electrode pitch circle of the upper electrode 11, and each bottom electrode 21 is connected to the DC power source 12 by an electrode lead (not shown). In this embodiment, it is connected to the anode side. Furthermore, a furnace body tilting mechanism 22 is provided on the foundation 2, and an exhaust gas duct 23 is provided on the upper portion of the furnace. In the DC arc furnace 1 having such a configuration, the bottom electrode 21 is located at a position where the distance a from the core C of the bottom electrode 21 satisfies a≧A with respect to the distance 111 mA from the top electrode 11 from the core C. , the DC arc generated between the upper electrode 11 and the bottom electrode 21 becomes more spread out, making it possible to quickly melt the charged material on the side wall of the furnace. , it becomes possible to perform average dissolution and shorten the dissolution time. Next, in the DC arc furnace 1 having the above structure, a capacity of 20 t.
on, at a position where the relationship between the distance A from the reactor core C to the upper electrode 11, the distance a from the reactor core C to the bottom electrode 21, and the distance glIR from the reactor core C to the reactor side wall is a=(A+R)/2. When melting was performed with the bottom electrode 21 installed, the melting time was about 50 minutes, and the bottom electrode (21) was connected to the top electrode (
11) The melting time in the conventional case located on the C side of the core is approximately 6
The dissolution time could be reduced by about 20% compared to 0 minutes. In addition, in this embodiment, the upper electrode 11 and the hearth bottom electrode 2
1 shows the case where there are three in each case, but the number is not limited to this, and the distance glA from the core C to one upper electrode 11 and the distance glA from the core C to the other upper electrode 11 The distance @A' is different from the core C
When the distance #a from the core C to the other bottom electrode 21 is different from the distance gia' from the core C to the other bottom electrode 21, for example, when the pitch circle of each electrode is an ellipse, It is sufficient that a≧A and a′≧A′, and that the upper electrode 11 and the bottom electrode 21
They do not have to be on the same radial direction, and the numbers of the upper electrode 11 and the furnace bottom electrode 21 may be different, and in any case, the furnace It is sufficient that the electrode pitch circle of the bottom electrode 21 is the same or larger.

【Effect of the invention】

As explained above, in the present invention, in a DC arc furnace equipped with a plurality of upper electrodes and a plurality of furnace bottom electrodes connected to a DC power source, the distance of the upper electrode from the core is @A.
On the other hand, the distance 1ta of the bottom electrode from the core is a≧A
Since the furnace bottom electrode is installed at a position that has the relationship of This makes it possible to reduce energy costs and improve melting efficiency.Furthermore, since the distance between the bottom electrodes increases, their maintenance and replacement work becomes even easier. This results in a significantly superior effect.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing an embodiment of a DC arc furnace according to the present invention. DESCRIPTION OF SYMBOLS 1... DC arc furnace, 11... Upper electrode 19... DC power supply, 21... Hearth bottom electrode, A... Distance of upper electrode from core, a... Hearth bottom electrode of core Distance from the reactor core, C...core, R...distance from the reactor side wall to the reactor core. Patent applicant: Daido Steel Co., Ltd. Representative patent attorney: Yutaka Oshio

Claims (1)

[Claims] (1) In a DC arc furnace equipped with a plurality of upper electrodes and a plurality of furnace bottom electrodes connected to a DC power source, a distance a of the bottom electrode from the core with respect to a distance A of the upper electrode from the core. A DC arc furnace characterized in that the furnace bottom electrode is provided at a position where a≧A.