Industrial electric heating furnaces – Arc furnace device
Reexamination Certificate
2000-04-28
2001-05-08
Hoang, Tu Ba (Department: 3742)
Industrial electric heating furnaces
Arc furnace device
C266S047000, C432S013000
Reexamination Certificate
active
06229838
ABSTRACT:
This application claims priority under 35 U.S.C. §§119 and/or 365 to 99 05859 filed in France on May 7, 1999; the entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject of the present invention is an electric arc furnace for the production of steel, as well as a method for operating this furnace.
2. Description of the Related Art
As is known, steel is obtained in such furnaces by melting scrap between electrodes, these furnaces comprising gas injectors provided with respective cooling chambers placed in a wall of the furnace. These injectors make it possible for oxygen and natural gas to be injected simultaneously so as to increase the energy supplied to the metal.
The use of burners and of injectors consisting of lances with oxygen injected at supersonic speed is well known. In the technology of manufacturing steel in an electric arc furnace, scrap is melted by establishing, in particular, an electric arc between the electrodes of the furnace and the metal so as to supply energy, melt the metal and keep it molten. By using burners and by adding oxygen and carbon, the additional energy that speeds up the metal melting process can be delivered to the metal.
The fitting of oxygen and carbon injectors and of burners in the wall of the furnace cannot be accomplished without taking into account a number of parameters, namely the position of the injector or of the burner on the panel, the available space outside the furnace at the chosen place for fitting them, etc. Each wall injector or each burner is protected by a cooling chamber consisting of a water-cooled cooling box usually made of copper, which is inserted into the panel.
A burner makes it possible to melt the scrap more rapidly and to eliminate any cold spots in the furnace, while an oxygen lance makes it possible to inject oxygen into the slag in order to obtain a foaming slag and to inject oxygen into the pool in order to decarburize it. The angle of propagation of the burner flame in the vertical plane with respect to the horizontal plane must lie within a defined angular range, the flame not being able to be angled radially in the furnace. On the other hand, the angle of oxygen injection with respect to the surface of the pool must be relatively large so that the oxygen can penetrate the pool or the slag without bouncing back off the surface of either of them. In practice, the angles of oxygen injection in the vertical plane must be greater than 40 degrees with respect to the horizontal plane.
In order to reduce the volume requirement and the problems caused by the multiplicity of holes in the panels of the furnace, devices have been created for fulfilling several functions with the same gas outlets. Thus, burners are known which can be switched to “oxygen lance” mode or oxygen lances are known which can operate in “burner” mode using the same gas outlets.
These devices therefore propagate their flame and inject their oxygen in the same direction. They do not allow the angle of oxygen injection and that of propagation of the flame to be modified.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a solution allowing this drawback to be eliminated, by reducing the volume requirement of the gas injectors around a furnace while maintaining their specificity and by simplifying the fluid feeds around the furnace.
The electric arc furnace for the production of steel forming the subject of the invention is of the type comprising gas injectors provided with respective cooling chambers placed in a wall of the furnace.
According to the invention, at least one single chamber is associated with at least two injectors in order to cool them.
According to one embodiment of the invention, at least one of the injectors is a supersonic gas injector, such as an oxygen lance, and at least one other injector is a burner that can use at least one oxygen-containing gas and a fuel.
The cooling chamber is, for example, a “cooling box” using water as the coolant. The invention therefore makes it possible to place a burner and a supersonic oxygen lance in the same cooling box (generally made of copper) both the burner and the lance being angled in the vertical and horizontal planes at angles appropriate to their respective functions, the function of the burner being to heat the pool of metal and/or to ensure postcombustion above the pool in order to oxidize the CO (and H
2
) possibly formed, whereas the lance, which is preferably a supersonic oxygen injection lance, directed towards the pool of metal allows decarburization of the molten iron, with or without the addition of pulverized coal.
In principal, this arrangement does not mean that the dimensions of the cooling box have to be increased with respect to a cooling box associated with a burner or with an oxygen injector according to the prior art.
According to another characteristic of the invention:
in the vertical plane, the longitudinal axis of the burner, which corresponds to the angle of propagation of its flame, defines with a horizontal plane an angle of between 20 and 30 degrees approximately; in the horizontal plane, the angle between the longitudinal axis of the burner and a vertical plane perpendicular to the wall of the cooling chamber is between zero degrees and 30 degrees approximately.
For further details about the type of tools according to the invention and the way in which they are used, reference may be made, for example to the texts U.S. Pat. Nos. 4,622,007, 4,642,047, 5,714,113, 5,788,921 or 5,843,368.
Further features and advantages of the invention will appear in the course of the following description, given with reference to the appended drawings which illustrate by way of non-limiting examples several embodiments thereof.
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Bremont Marc
Flichy Sébastien
Laurent Jacky
Viraize Frederic
Vuillermoz Jean-Claude
Burns Doane Swecker & Mathis L.L.P.
Hoang Tu Ba
L'Air Liquide, Societe Anonyme pour l'Etude et l'
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