Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1998-02-17
2000-02-29
Andrews, Melvyn
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75581, C21C 552
Patent
active
060304316
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to the heating and melting of a scrap bulk and, more particularly, to a method for improving energy input in heating and melting of a scrap bulk.
(ii) Description of the Related Art
The output-limiting step in the heating and melting of scrap is the transfer of energy to the scrap bulk. As a result, the melting phase may be supported, for example, by burners installed on the side walls in the case of electric arc finaces. The transfer of heat into the scrap bulk by these burners, however, is limited since the conduction of heat through the large interstitial volume of the scrap charge is poor. The energy which can be introduced by burners is therefore limited to a max. 10% of the total energy required for scrap melting.
A known converter method for scrap melting provides for melting the scrap column from below by means of bottom nozzles that are operated with oxygen and finely divided coal. This achieves an optimal transfer of the heat of the hot combustion gases to the scrap bulk. In a variant of this method, coke is charged at the bottom of the converter before the scrap is added and the coke is then burned using oxygen. In small converters it has proven possible to convert scrap to liquid steel with this method at a coke consumption of approximately 220 kg. Additional energy is transferred to the scrap from above through combustion of the reaction gases using an oxygen jet.
In another method, a natural gas- or oil-oxygen burner is installed in the side wall immediately above the floor of the converter. This method does make possible melting of the scrap, but a considerable portion of the iron is oxidized, and the liquefied iron must be removed from the converter at a temperature just above the melting point in order to undergo post-treatment in a separate container.
European Patent 0 350 982 A1.sup.1 discloses a method for improving the energy input during the heating and melting of a scrap bulk. In this method, a channel is burned into the scrap bulk by a burner having the form of a lance and an oxygen lance is then inserted into the channel. This lance insertion has proven to be impossible to execute in actual practice.
In summary, one should note that in all the heretofore known methods it has not been possible to achieve a substantial transfer of energy from the combustion of fossil fuels, whether coal, oil, or natural gas, into a scrap bulk without concomitant strongly perturbing secondary reactions and with the required high thermal efficiency.
SUMMARY AND OBJECTS OF THE INVENTION
The object of the invention is the transfer of energy into a scrap bulk at high thermal Efficiencies and without the appearance of perturbing secondary reactions.
The aforesaid object is achieved by a method for improving the energy input during the heating and melting of a scrap bulk, in which a channel is burned into the scrap bulk and additional energy for the heating and melting of the scrap bulk is input through this channel, wherein said method is characterized in that the said channel is burned into the scrap bulk by means of a hot, oxygen-containing gas jet.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
It has surprisingly been found that a hot, oxygen-containing gas jet can burn a channel into a scrap bulk within only a few minutes.
Thus, it has been possible, for example, with a central nozzle to burn a channel approximately 20 cm in diameter and 3 m deep within 3 minutes using a hot air jet of 2000 M.sup.3 /hour and a draft temperature of 1400.degree. C., an exit velocity from the hot air nozzle of 600 m/s, and the addition of 100 Nm.sup.3 /hour natural gas.
A channel can be burned into the scrap bulk without the addition of fossil fuel using a hot, oxygen-containing gas jet alone. However, channel burning is preferably executed in the presence of fossil fuel. The fossil fuel can be present in the scrap bulk, but is preferably added to the gas jet. It should be understood that both variants, addition of fossil fuel
REFERENCES:
patent: 5286277 (1994-02-01), Aizatulov et al.
patent: 5599375 (1997-02-01), Gitman
Patent Abstracts of Japan vol. 012, No. 117, Apr. 13, 1988, JP 62 238318.
Patent Abstracts of Japan vol. 009, No. 309, Dec. 5, 1985, JP 60 149710.
Patent Abstracts of Japan vol. 008, No. 046, Feb. 29, 1984, JP 58 204111.
Brotzmann Karl
Deloche Daniel
Andrews Melvyn
L'Air Liquide, Societe Anonyme pour l'Etude et l'Expolitation de
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