An improved apparatus for producing steel, including a lower furnace, an annular, water-cooled, fireproof lined cylindrical upper furnace, on which an upwardly closing conically tapering hat having openings can be placed. The smelting assembly is configured for the operational mode without melt flow and the operational mode with melt flow. To this end, at least one opening is provided in the conical furnace cover, through which opening at least one top lance can be introduced into the upper furnace. A plurality of sidewall injectors radially rotate around the cylindrical upper furnace in such a way that in a working position, the top lance and the sidewall injectors are directed onto a smelt level of a molten mass located in the lower furnace for refining.

A method for manufacturing molten iron by melting a cold iron source in an electric arc furnace having a carbonaceous material-injecting device. The method includes, in the carbonaceous material-injecting device, while a carbonaceous material is injected with a carrier gas through a central portion of the carbonaceous material-injecting device, injecting a fuel and a combustion-supporting gas through respective outer peripheral portions of the carbonaceous material-injecting device. The carbonaceous material injected through the central portion passes through a cylindrical combustion flame generated by a combustion reaction between the fuel and the combustion-supporting gas and is injected into molten slag and molten iron.

In a method for producing a molten steel according to one aspect of the present invention, the solid-state direct reduced iron contains 3.0% by mass or more of SiO.sub.2 and Al.sub.2O.sub.3 in total and 1.0% by mass or more of carbon. A ratio of a metallic iron to the total iron content contained in the solid-state direct reduced iron is 90% by mass or more, and an excess carbon content Cx is 0.2% by mass or more to the carbons contained in the solid-state direct reduced iron. The method includes a step in a first furnace of melting 40 to 100% by mass of the solid-state direct reduced iron, and separating a molten pig iron having a carbon content of 2.0 to 5.0% by mass and a temperature of 1350 to 1550° C. and a slag having a basicity of 1.0 to 1.4 and a step in a second furnace of melting a remainder of the solid reduced iron together with the molten pig iron separated in the first furnace and blowing oxygen onto the molten material to decarburize into a molten steel.

One object of the present invention is to provide a burner which makes it possible to prevent blockage and damage of the nozzle by the molten metal and the slag, and the present invention provides a burner including a combustion supporting gas supply passage which is configured to supply a combustion supporting gas toward a combustion supporting gas outlet provided at the center of the tip end side; a fuel supply passage which is configured to supply a fuel toward a fuel ejection outlet provided around the combustion supporting gas outlet; and a protective nozzle provided from a position surrounding a periphery of the fuel ejection outlet so as to project forward beyond the tip end surface at which the combustion supporting gas ejection outlet and the fuel ejection outlet are provided; wherein the combustion supporting gas supply passage includes a Laval nozzle, and a diameter-enlarged nozzle of which a diameter gradually increases from the tip end of the Laval nozzle toward the combustion supporting gas ejection outlet, and the protective nozzle has a shape which is gradually reduced in diameter forward from the tip end surface.

When using oxygen gas pipes 3, situations can arise, in particular due to slag return and similar dangers, in which the operator must initiate safety measures. Slag return safety devices are known which, in such a case, ensure that the gas flow is stopped by melting a cap 35 of a heat sensor 5. The response of this outlet valve 6 of the slag return safety device can be recognized, for example, by the fact that the inlet pressure of the existing oxygen gas 4 is used to push pins 21 located in the wall 19 of the oxygen gas pipe 3 beyond the outside 27 of the oxygen gas pipe 3, so that they cannot be overlooked as a warning signal. The movement of the pins 21 can be used to activate further signal systems 30 in order to provide additional indications of this movement optically and/or acoustically.

A method for providing a region of inert gas around the electrodes in an electric arc furnace is provided. This electric arc furnace includes consumable graphite electrodes, a melting zone, and at least one lance including an inlet and an outlet, wherein the inlet is connected to a liquid inert fluid source. The method includes introducing the consumable graphite electrodes into the melting zone, wherein the distal ends of the electrodes form arcs with a solid charge of scrap metal. The method also includes introducing the liquid inert fluid into the inlet end of the at least one lance, wherein the inert fluid exits the outlet end and is introduced into the melting zone proximate to the distal ends of the electrodes, thereby providing an inert gaseous blanket, once the liquid vaporizes, around the distal ends of the electrodes

A system and a method for determining/predicting a tapping time for a metal melt in an electric arc furnace (EAF), at least one electrode is provided for melting the metal melt until it reach a target tapping temperature, the EAF further includes a slag and smoke layer on the surface of the metal melt, wherein an electromagnetic stirrer is provided for stirring the metal melt.

A burner-lance unit (1) includes at least two gas connections (2a, 2b, 2c), a burner tube (3), and a lance tube (4) that is placed concentrically in the burner tube (3). The burner tube (3) and the lance tube (4) both have a gas inlet end and a gas outlet end (15). The lance tube (4) has a de Laval nozzle (4a) at the gas outlet end thereof. The de Laval nozzle (4a) is releasably connected to the lance tube (4). The burner tube (3) has a burner nozzle (3a) which is releasably connected to the burner tube (3).

A refractory-lined equipment includes a vessel defining an interior at least partially lined with a refractory material, and a nozzle assembly coupled to the vessel and extending into the interior. The nozzle assembly includes an outer sleeve fixed to the sidewall and extending through an aperture defined in the sidewall, the outer sleeve defining a central passageway, and a nozzle cartridge assembly positionable within the central passageway and including an inner sleeve, a refractory lining disposed about the inner sleeve, and a nozzle positioned within the inner sleeve. The nozzle cartridge assembly is removably coupled to the outer sleeve external to the vessel.

A charged material containing a metal raw material of at least one of ferrochromium containing metal Si or ferrosilicon and unreduced slag containing Cr oxide generated by oxidation refining is charged into an AC electric furnace including three electrodes, a mass ratio of a metal Si amount to a Cr oxide amount being from 0.30 to 0.40, and a C concentration being from 2.0% by mass to a saturation concentration, and operation is performed under a condition where a diameter PCD (m) of a circle passing through the centers of the three electrodes viewed in a plan view from a central axis direction of the electric furnace, an average electrode height H.sub.e (m) that is a vertical distance from a tip of each electrode to a molten metal surface, a furnace inner diameter D.sub.f (m), a molten slag thickness H.sub.s (m), a spreading diameter D.sub.arc (m) of an arc on the molten metal surface, and a deflection angle θ (deg) of the arc satisfy the following relationships to produce molten iron containing Cr.

D.sub.arc=PCD+2H.sub.e.Math.tan θ

θ=52.5−75.Math.(PCD/D.sub.f)

0.22≤D.sub.arc/D.sub.f≤0.30

0.35≤H.sub.e/H.sub.s≤1.50