Method of making steel

Details Method of making steel Method of making steel

1996-03-18

1998-11-10

Andrews, Melvyn

Specialized metallurgical processes, compositions for use therei

Processes

Producing or treating free metal

75320, 75961, 75962, C21B 1314

Patent

active

058337350

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a method of producing briquettes for use in steelmaking processes in a melting vessel, including the step of briquetting iron-oxide containing metallurgical residues.
In smelting plants various iron oxide-containing residues, such as filter dusts from steel plants and blast furnaces, rolling scale from rolling mills and slurries from gas cleaning, are obtained as byproducts. In former times, such residues were disposed of by ultimate disposal on waste disposal sites or they were fed back into the blast-furnace process by application to sintering plants. In view of the increasing demand for a reduction of costs and in view of the limit values for environmental impact which have to be expected in the future, attempts have recently been made to recycle the residues into the steelmaking process. Methods known in this respect are methods in the case of which residues, especially filter dusts orginating from LD plants, are, on the one hand, hot-briquetted and introduced into a converter, or, on the other hand, blown into a converter. These methods are disadvantageous insofar as only a single iron oxide-containing residue can be used. In addition, only a limited amount of iron oxides can be supplied to the converter, and, consequently, said iron oxides exclusively serve as a substitute for cooling ore. It follows that, essentially, iron oxide-containing residue briquettes are supplied only for the purpose of temperature control. The amount of iron oxide-containing residues added rarely exceeds 5% by weight.
It is the object of the present invention to provide a method of producing briquettes which permit a better utilization of iron oxide-containing residues in a steelmaking process in a melting vessel.


BRIEF DESCRIPTION OF THE DRAWING

The DRAWING illustrates a steelmaking process in accordance with the invention in which briquettes including iron oxide-containing metallurgical residues and carbon carriers are added as scrap substitute.


DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, this task is solved by the feature that, prior to the briquetting step, the residues have added thereto essentially uniformly distributed carbon carriers, which are required for achieving an essentially complete, autothermal reduction of the iron oxide-containing residues so that the briquettes can be introduced into the converter as a scrap substitute. Carbon carriers are now located in immediate vicinity to the residues, said carbon carriers being capable of reducing the iron oxides contained in the residues. In addition, the energy balance is essentially optimized and a complete reduction of the iron oxides in the residues is guaranteed. In principle, the step of additionally adding carbon carriers does not seem to make much sense, since, especially in steelmaking processes, a reduction of the carbon content of the melt is normally aimed at. Since, however, the iron oxides contained in the residues can react with the carbon carriers in the residue briquettes, essential advantages are obtained. In the method according to the present invention, a mixture of various metallurgical residues can be used, e.g. filter dusts from steel plants and blast furnaces, rolling scale from rolling mills and dried slurries from wet gas cleaning. The mixing ratio can be chosen in accordance with the respective amount of byproducts obtained. Furthermore, a converter can now deal with large amounts of iron oxide-containing residues so that up to 30% of these residues can be supplied to the converter. Hence, the residues cannot only be used as a substitute for cooling ore, as has been done in the case of the methods known, but they can even be introduced into the converter instead of scrap. This provides essential economic advantages as well as a good possibility of recycling metallurgical residues in steelmaking processes.
U.S. Pat. No. 2,865,731 already discloses the measure of briquetting iron oxide-containing residues while adding cellulose fibres as

REFERENCES:
patent: 2865731 (1958-12-01), Crowe
patent: 3653876 (1972-04-01), Wienert
patent: 4765829 (1988-08-01), Beckmann et al.
patent: 5100464 (1992-03-01), Kelly et al.
patent: 5591247 (1997-01-01), Dumont et al.

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