Industrial electric heating furnaces – Arc furnace device
Reexamination Certificate
2000-03-21
2001-09-11
Hoang, Tu Ba (Department: 3742)
Industrial electric heating furnaces
Arc furnace device
C373S063000, C373S085000, C075S500000, C266S236000
Reexamination Certificate
active
06289034
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and to an apparatus for producing molten metal (which term includes metal alloys) from a metalliferous feed using electrical energy.
The present invention relates particularly, although by no means exclusively, to producing iron, steel, and ferroalloys in an electric furnace.
The term “electric furnace” is understood herein to cover any furnace that relies wholly or partly on electric current for heating a metal containing metalliferous charge.
By way of example, the term “electric furnace” covers conventional a/c and d/c arc furnaces commonly used in steelmaking, submerged arc furnaces commonly use in the production of ferroalloys and pig iron, and induction furnaces commonly used for melting scrap.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved process and apparatus for producing molten metal from a metalliferous feed in an electrical furnace.
According to the present invention there is provided a process for producing metals from a metalliferous feed material in an electric furnace, which process includes the steps of:
(a) forming a molten bath having a metal layer and a slag layer on the metal layer in the furnace;
(b) supplying electrical energy to the furnace and converting the electrical energy to thermal energy and thereby contributing to the heat input requirements of the process;
(c) injecting a carrier gas and a solid carbonaceous material into the molten bath via one or more than one lance/tuyere;
(d) causing molten material to be projected from the molten bath as splashes, droplets, and streams into a space above a nominal quiescent surface of the molten bath and forming a transition zone; and
(e) injecting an oxygen-containing gas into the furnace via one or more than one lance/tuyere and post-combusting reaction gases released from the molten bath and thereby further contributing to the heat requirements of the process.
The term “metal layer” is understood herein to mean that region of the bath that is predominantly metal.
The term “slag layer” is understood herein to mean that region of the bath that is predominantly slag.
The term “transition zone” is understood herein to mean a zone above the nominal quiescent surface of the molten bath in which there are ascending and thereafter descending droplets or splashes of molten material.
The term “quiescent surface” in the context of the molten bath is understood herein to mean the surface of the molten bath under process conditions in which there is no gas/solids injection and therefore no bath agitation.
Step (a) of forming a molten bath may include supplying an initial solid charge of the metalliferous feed material to the furnace and melting at least part of the charge by means of thermal energy generated from electrical energy supplied to the furnace.
Alternatively, step (a) may include supplying the metalliferous feed material to the furnace in a molten form and thereby forming the molten bath.
In either situation described in the preceding two paragraphs, the process may include adding further metalliferous feed material to the furnace at a later stage in the process.
The transition zone is an effective region for post combustion of reaction gases. In addition, the movement of droplets, splashes, and streams of molten material between the bath and the transition zone is an effective means of transferring to the molten bath the heat generated by post combustion of reaction gases. Furthermore, the molten material, and particularly the slag, in the transition zone is an effective means of minimising heat loss by radiation via the side wall of the furnace in contact with the transition zone.
The transition zone is quite different to the slag layer. By way of explanation, under stable operating conditions of the process, the slag layer comprises gas bubbles in a liquid continuous volume whereas the transition zone comprises splashes, droplets, and streams of molten material in a gas continuous phase. More particularly, the transition zone is a non-foaming slag environment and, therefore, is quite different to the zone that is generated in conventional arc furnaces as a consequence of carbon boil and foaming slag practices in these furnaces.
In a situation where the electric furnace includes electrodes extending into the furnace for supplying electrical energy to the furnace, it is preferred that the process includes forming a protective layer of molten material on the electrodes.
It is preferred particularly that the splashes, droplets and streams of molten material projected from the molten bath in step (d) forms the protective coating.
The reaction gases released from the molten bath may include any suitable combustible gases, such as CO and H
2
.
Post-combusting reaction gases and transferring energy to the bath in accordance with the present invention contributes to the thermal energy requirements of the process and thereby reduces the electrical energy requirements of the furnace.
Preferably the level of post-combustion is at least 40%, more preferably at least 60%, where post-combustion is defined as:
[
CO
2
]
+
[
H
2
O
]
[
CO
2
]
+
[
H
2
O
]
+
[
CO
]
+
[
H
2
]
where:
[CO
2
]=volume % of CO
2
in off-gas
[H
2
O]=volume % of H
2
O in off-gas
[CO]=volume % of CO in off-gas
[H
2
]=volume % of H
2
in off-gas
The injection of the carrier gas and the solid carbonaceous material into the molten bath and the injection of oxygen-containing gas into the furnace in accordance with the present invention causes mixing of constituents in the molten bath and in the transition zone and other sections of the gas space above the molten bath which promotes the chemical reactions required by the process.
Depending on the end product to be produced by the process, other solid materials may be injected into the molten bath with the solid carbonaceous material.
By way of example, when the process is concerned with producing iron, metalliferous feed material in the form of iron ore and/or partially reduced iron ore, slag forming agents, and fluxes may be injected with the carrier gas and the solid carbonaceous material into the molten bath.
By way of further example, when the process is concerned with producing steel, metalliferous feed material in the form of scrap steel, pig iron, steel plant wastes, and other iron-containing sources, slag forming agents, and fluxes may be injected with the carrier gas and the solid carbonaceous material into the molten bath.
By way of particular example, when the process is concerned with producing steel from iron ore and/or partially reduced iron ore, the final stages of the process may include stopping injection of the solid carbonaceous material into the molten bath to facilitate adjustment of the carbon concentration of the molten bath to that for a required steel composition.
It is preferred that the carrier gas and the solid carbonaceous material and optionally other solid materials be injected into the metal layer of the molten bath.
It is preferred particularly that the transition zone be formed by injecting the carrier gas and the solid carbonaceous material and optionally other solid materials into the molten bath through one or more than one lance/tuyere positioned above and extending downwardly towards the metal layer of the molten bath.
It is preferred that the one or more than one lance/tuyere be at an angle of between 10 and 70° to the vertical.
It is preferred particularly that the angle be between 20 and 60°.
It is preferred that the lances/tuyeres be retractable.
It is preferred that the injection of the carrier gas and the solid carbonaceous material and optionally other solid materials into the molten bath be sufficient to cause molten material to be projected into the space above the bath in a fountain-like manner.
The metalliferous feed material may be in any suitable form, such as lump pellets, and fines.
The metalliferous feed material may be preheated.
The carrier gas may be any suitable c
Hoang Tu Ba
Merchant & Gould P.C.
Technologies Resources Pty. Ltd.
LandOfFree
Process and an apparatus for producing metals and metal alloys does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and an apparatus for producing metals and metal alloys, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and an apparatus for producing metals and metal alloys will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2445402