JP2590993B2 - DC arc furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a DC arc furnace mainly used for steelmaking using scrap as a raw material. (Prior art) Conventionally, in steelmaking, a blast furnace first converter system using iron ore as a raw material has been widely adopted as one suitable for mass production. On the other hand, an arc furnace using scrap as a raw material has been used. Electric furnace steelmaking is also widely adopted. In this electric furnace steelmaking, an AC arc furnace is usually used, and the size and power are gradually increased to the development of a UHP furnace (ultra high power furnace). It has been established as a mass-production steelmaking system. 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 flicker problem increases,
Due to the limitation of the electrode current density due to the electrode skin action peculiar to alternating current, some DC arc furnaces that supply direct current between the upper electrode and the furnace bottom electrode have also been overlooked. Although this DC arc furnace has not progressed so far for workability reasons, it has recently developed AC-DC with high power capacity.
The development of conversion rectification equipment has greatly contributed to its reconsideration, and conventionally known DC arc furnaces penetrate the furnace lid that covers the upper part of the furnace body composed of the furnace wall and furnace shell, An upper electrode connected to, for example, the cathode side of the DC power supply is provided so as to be able to move up and down, and a furnace bottom electrode connected to, for example, the anode side of the DC power supply is provided on the bottom of the furnace body. A DC arc is generated between the furnace and the furnace, so that the scraps charged in the furnace are melted by arc heating. In such a DC arc furnace, compared to the conventional AC arc furnace, the electrode diameter is reduced at the same current value, the reduction of the electrode surface oxidation reduction due to the diameter reduction, and the temperature of the electrode tip compared with AC is reduced. It is possible to provide advantages such as a reduction in electrode unit consumption due to a reduction in graphite sublimation based on the reduction, a reduction in flicker level and a reduction in arc nozzles. (Problems to be Solved by the Invention) As described above, the conventional DC arc furnace has several advantages as compared with the AC arc furnace, but the supply of DC power to the upper electrode is different from that of the conventional AC arc furnace. As in the case above, a rigid support bus (copper plate, copper pipe, etc.) is attached to the liftable electrode support arm with an electrode clamp at the tip for gripping the upper electrode.
Are fixed in a substantially parallel state, and one end of the rigid arm busbar is electrically connected to the electrode clamp, and the other end of the rigid arm busbar is electrically connected to one end of the flexible electric wire. Then, the other end of the flexible electric wire is connected to a fixed secondary bus connected to a DC power source (the configuration of the power connection part of the AC arc furnace is described in "Steel Handbook", page 532, 10. Electric furnace steelmaking method ( 1982
December 25, published by the Iron and Steel Institute of Japan). ), There is a problem that many electrical connection portions are present, electrical loss is increased, and energy costs are reduced and melting efficiency is improved. (Purpose of the Invention) The present invention has been made in view of the above problems, and it is possible to reduce power loss due to an electrical connection, reduce energy cost, and improve melting efficiency. It is intended to provide a DC arc furnace.

Configuration of the Invention

(Means for Solving the Problems) The present invention relates to a DC power supply having an upper electrode connected to one side of a DC power supply and held by an electrode clamp, and a furnace bottom electrode connected to the other side of the DC power supply. In the arc furnace, the conductor from the electrode clamp to the fixed secondary bus or the rectifier of the DC power supply via the electrode support arm is constituted by a flexible cable in which a conductor is placed in an elastic hose. If necessary, the flexible cable constituting the conductor from the electrode clamp to the fixed secondary bus of the DC power supply or the rectifier via the electrode support arm is supplied with cooling water into an elastic hose to form a conductor. It is characterized by having a water cooling structure for cooling. (Embodiment) FIG. 1 shows an embodiment of a DC arc furnace according to the present invention. This DC arc furnace 1 has columns 3 and 4 installed on a foundation 2.
The furnace body 5 is supported by the
Is provided with a furnace lid 6, which is suspended by a support 7, and which can be raised and lowered and turned. In addition, it penetrates through the furnace lid 6 and, on the same electrode pitch circle centered on the core C, equidistant (12
Upper electrode 11 composed of, for example, three graphite electrodes at 0 ° intervals)
Is arranged. These upper electrodes 11 are supported by an electrode clamp 12, an electrode support arm 13, and the like, respectively, and can be raised and lowered by an electrode lifting mechanism 14. Further, as shown in FIG. 2, the upper electrode 11 is electrically connected to one end of a flexible cable 16 in which a conductor 15 is placed in an elastic hose 14 made of, for example, a rubber hose. And the flexible cable 16
The other end of the flexible cable 16 is supported by a fixed secondary bus 19 connected to a DC power supply 18 at the other end thereof. The rectifier 18 is connected to the cathode side of the rectifier 20 in this embodiment. The flexible cable 16 is a water-cooled cable that cools the conductor 15 by supplying cooling water into the elastic hose 14. Further, a furnace body tilting mechanism 26 is provided on the base 2 and an exhaust gas duct 27 is provided on the upper part of the furnace. Further, the furnace bottom portion of the furnace main body 5 is arranged at equal intervals (120) in the circumferential direction on the same electrode pitch circle centered on the core C.
3), three furnace bottom electrodes 25 made of, for example, a conductive metal are arranged in a penetrating state, and each furnace bottom electrode 25 is connected to a rectifier 20 of the DC power supply 18 by an electrode lead (not shown). Is connected to the anode side. In the DC arc furnace 1 having such a configuration, a DC power supply is supplied through an electrode support arm 13 from an electrode clamp 12 which holds an upper electrode 11.
The conductor section up to the fixed secondary bus 19 (or the rectifier 20 in another embodiment) may be connected to the
Since the flexible cable 16 is formed of a water-cooled water-cooled cable into which the cooling water is supplied and the cooling water is supplied, a rigid arm busbar provided substantially in parallel with the electrode arm (13) is used. As compared with a DC arc furnace that directly adopts the structure of an AC arc furnace in which a flexible electric wire is connected to the other end side of the supporting arm busbar, the number of electrical connection portions is reduced, and the electrical connection at the connection portion is reduced. Loss can be reduced, and energy cost can be reduced and melting efficiency can be improved. Next, in the DC arc furnace 1 having the above structure, a capacity of 20 to
n was melted while flowing the cooling water into the elastic hose 14 of the flexible cable 16 to cool the conductor 15, and a rigid arm almost parallel to the electrode arm (13) was used. The power consumption can be reduced by about 5% as compared with the case where power is supplied using a bus bar and a flexible electric wire. In the above embodiment, the upper electrode 11 and the furnace bottom electrode 25 were used.
Are both three, but the number is not limited to this. Further, the fixed secondary bus 19 may be omitted, and the flexible cable 16 may be directly connected to the rectifier 20 of the DC power supply 18.

【The invention's effect】

As described above, the present invention relates to a DC arc furnace including an upper electrode connected to one side of a DC power supply and held by an electrode clamp, and a furnace bottom electrode connected to the other side of the DC power supply. Since the conductor from the electrode clamp to the fixed secondary bus of the DC power supply or the rectifier via the electrode arm is constituted by a flexible cable in which a conductor is placed in an elastic hose, the electrode arm is substantially formed. Since a rigid arm busbar is provided in parallel and the number of electrical contacts can be reduced as compared with a case where a flexible electric wire is connected to the arm busbar, it is possible to further reduce the electric loss. In addition, a remarkably excellent effect of reducing energy cost and improving dissolution efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an embodiment of a DC arc furnace according to the present invention, and FIG. 2 is a sectional view of a flexible cable. 1 DC arc furnace, 11 Upper electrode 12 Electrode clamp, 13 Electrode arm, 14 Elastic hose, 15 Conductor, 16 Flexible cable, 18 DC power supply , 19… fixed secondary bus, 20… rectifier, 25… hearth electrode.

Claims (2)

(57) [Claims] 1. A DC arc furnace comprising an upper electrode connected to one side of a DC power supply and held by an electrode clamp, and a furnace bottom electrode connected to the other side of the DC power supply. A DC arc furnace characterized in that a conductor from a supporting arm to a fixed secondary bus of the DC power supply or a rectifier is formed of a flexible cable having a conductor inserted in an elastic hose. 2. A flexible cable constituting a conductor from an electrode clamp to a fixed secondary bus or a rectifier of a DC power supply via an electrode support arm, supplies cooling water into an elastic hose to cool the conductor. The DC arc furnace according to claim 1, wherein the DC arc furnace is a water-cooled cable.