Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1994-10-31
1996-06-04
Andrews, Melvyn
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75460, 75466, 266221, 266268, C21B 716, C21B 500
Patent
active
055229166
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the injection of oxygen into a blast furnace or a cupola.
By blast furnace or cupola, is meant an apparatus comprising a more or less cylindrical chamber with a vertical axis into which is introduced from the top or throat metallic mineral and coke, the term mineral designating here any material adapted to supply, by reduction, metal and coke, and, toward the lower part of the chamber, there is introduced a gas containing oxygen, such as hot air, which, by reacting with the coke, raises the temperature of the descending mass, to reduce the mineral and form liquid metal which collects in the lower part of the chamber.
The gas containing oxygen is injected into the chamber by a series of tuyeres, which are generally regularly spaced in a horizontal circle.
The gas containing oxygen is introduced by the tuyere at a relatively high speed, and there results, in the mass of mineral and coke, the formation of a cavity whose axis, parallel to that of the tuyere adjacent the latter, then is concave upwardly. Contradictory information has been published on the more or less dense presence of pieces of coke in the cavity. It appears that they occur in low quantity and that they are continuously agitated by currents of gas.
It is known to inject, by the tuyeres, into foundry blast furnaces, carbon in addition to hot air. This injection of carbon permits diminishing the consumption of coke. To conserve good operating conditions, it is then necessary to introduce superoxygenated air through the tuyeres.
So as to improve the operation of the blast furnace, it would be desirable to be able to regulate the dimensions of the cavity. Unfortunately, the latter depends on a certain number of parameters which, by reason of other constraints, cannot as a practical matter be modified: the flow rate, the temperature and the pressure of the air are dictated by the production regime of the blast furnace, the efficiency of gasification of the coke, and the nature of the mineral to be reduced. The number of tuyeres for a given blast furnace can be changed only with great difficulty, and this number corresponds to the need for homogeneity of the distribution of the gas in the chamber. The injections of powdered carbon and oxygen through the tuyeres have the effect of decreasing the required coke charge, but are practically without effect on the dimensions of the cavity. The injection of pure oxygen permits efficacious gasification of the carbon powder, but its effect is limited by the fact that in the bottom of the cavity the atmosphere is comprised essentially of carbon monoxide (CO.sub.2), practically pure, so that the non-gasified particles of carbon must recirculate within the cavity, under the influence of gas currents, so as to achieve their gasification.
The invention has for its object to provide an injection process for oxygenated gas in a blast furnace or a cupola, which permits improving the operating conditions of this blast furnace or cupola.
To obtain this result, the invention provides a process for obtaining metal in the blast furnace or cupola, according to which the mineral and the coke are introduced in the throat of the blast furnace or cupola and a gas containing oxygen is injected, with carbon, toward the lower portion of the blast furnace by tuyeres opening within the chamber of this latter, this process having the particularity that at least one portion of the oxygen is injected by the tuyere in the form of a jet of liquid oxygen at high speed.
Preferably, the speed at which the liquid oxygen leaves the tuyere is greater than 100 meters per second.
Preferably, the liquid oxygen, from a source of liquid oxygen at ambient pressure, passes through a pressurizing pump, then into a subcooling device located adjacent the blast furnace, before reaching a nozzle of a cross section calculated to transform the pressure of the liquid oxygen into velocity, this nozzle being disposed in the tuyere and coaxial with it.
The liquid oxygen injected at high speed passes at least in pa
REFERENCES:
patent: 3701517 (1972-10-01), Gray
patent: 5244489 (1993-09-01), Grenier
Buffenoir Marc
Karinthi Pierre
Streicher Eric
Andrews Melvyn
L'Air Liquids, Societe Anonyme pour L'Etude et L'Exploitation de
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