Provided is a molten metal holding furnace with heat dissipation and insulating properties. An insertion hole 20 of a molten metal holding furnace 10 has an inside cylindrical portion (tapered surface) 21 and an outside cylindrical portion 22 (cylindrical surface). A heating tube 30 has a distal cylindrical portion 35 corresponding to the inside cylindrical portion 21 and a proximal cylindrical portion 36 corresponding to the outside cylindrical portion 22. The heating tube 30 is inserted and positioned in the insertion hole with the distal cylindrical portion 35 positioned at the inner cylindrical portion 21 and the proximal cylindrical portion 36 positioned at the outside cylindrical portion 22. A filling material 60 is filled between the heating tube 30 and the insertion hole 20.

In a method for operating an electric arc furnace operated with an alternating voltage, a structure-borne sound signal occurring on a wall of the electric arc furnace is detected, from which structure-borne sound signal a parameter characterizing the flicker properties of the electric arc furnace is calculated. At least one process variable of the electric arc furnace is controlled on the basis of the calculated parameter. An electric arc furnace operated according to the method is used in and for a melting plant.

In a method for operating an electric arc furnace operated with an alternating voltage, a structure-borne sound signal occurring on a wall of the electric arc furnace is detected, from which structure-borne sound signal a parameter characterizing the flicker properties of the electric arc furnace is calculated. At least one process variable of the electric arc furnace is controlled on the basis of the calculated parameter. An electric arc furnace operated according to the method is used in and for a melting plant.

Provided are a fixed-type electric furnace enabling continuous operation which allows melting without the interruption of power supply and tapping in a fixed state, and a fixed-type electric furnace and a molten steel production method using same. The fixed-type electric furnace comprises: a preheating furnace which is disposed on the side of a melting furnace and preheats an iron source (scrap) using exhaust gas from the melting furnace; a supply means for supplying the iron source, which has been preheated in the preheating furnace, to the melting furnace; the melting furnace comprising electrodes for melting the preheated iron source; and a fixed-type discharge means for discharging molten steel which has been melted in the melting furnace, wherein the preheating furnace is integrally connected to the melting furnace.

Provided are a fixed-type electric furnace enabling continuous operation which allows melting without the interruption of power supply and tapping in a fixed state, and a fixed-type electric furnace and a molten steel production method using same. The fixed-type electric furnace comprises: a preheating furnace which is disposed on the side of a melting furnace and preheats an iron source (scrap) using exhaust gas from the melting furnace; a supply means for supplying the iron source, which has been preheated in the preheating furnace, to the melting furnace; the melting furnace comprising electrodes for melting the preheated iron source; and a fixed-type discharge means for discharging molten steel which has been melted in the melting furnace, wherein the preheating furnace is integrally connected to the melting furnace.

An electrode seal for use in a metallurgical furnace, the furnace comprising a furnace space heated by electrodes extending through an aperture into the furnace space. The electrode seal comprises at least three sets of shoes in consecutive lateral contact, each shoe having a biasing member for biasing a surface of the shoe toward one of the electrodes thereby allowing the one electrode to longitudinally move within the electrode seal while providing electrical insulation between the electrode and the aperture.

An electrode seal for use in a metallurgical furnace, the furnace comprising a furnace space heated by electrodes extending through an aperture into the furnace space. The electrode seal comprises at least three sets of shoes in consecutive lateral contact, each shoe having a biasing member for biasing a surface of the shoe toward one of the electrodes thereby allowing the one electrode to longitudinally move within the electrode seal while providing electrical insulation between the electrode and the aperture.

Provided is a heater protection tube for use with a molten metal holding furnace with heat dissipation and insulating properties. A heat protection tube 31 has a distal tapered cylindrical portion 35 corresponding to the inside tapered cylindrical portion 21 and a proximal non-tapered cylindrical portion 36 corresponding to the outside non-tapered cylindrical portion 22. The heater protection tube (31) is configured so that it can be mounted in the side wall (13) with the distal tapered cylindrical portion (35) located at the inside tapered cylindrical portion (21) and with the proximal non-tapered cylindrical portion (36) located at the outside non-tapered cylindrical portion (22).

Provided is a heater protection tube for use with a molten metal holding furnace with heat dissipation and insulating properties. A heat protection tube 31 has a distal tapered cylindrical portion 35 corresponding to the inside tapered cylindrical portion 21 and a proximal non-tapered cylindrical portion 36 corresponding to the outside non-tapered cylindrical portion 22. The heater protection tube (31) is configured so that it can be mounted in the side wall (13) with the distal tapered cylindrical portion (35) located at the inside tapered cylindrical portion (21) and with the proximal non-tapered cylindrical portion (36) located at the outside non-tapered cylindrical portion (22).

A method and device for depleting copper smelting slag. The method comprises mixing copper smelting molten slag (1) with a reductant (2) and an inert gas (3) under pressure, and then depleting same. The device for depletion comprises a furnace body (4), which furnace body (4) is provided with a feed opening (413) and a slag discharge port (416), and gas nozzles (411) disposed on the side wall of the furnace body.