Process for the direct production of cast iron from iron bearing

Details Process for the direct production of cast iron from iron bearing Process for the direct production of cast iron from iron bearing

1999-08-04

2000-11-14

Kastler, Scott

Specialized metallurgical processes, compositions for use therei

Processes

Producing or treating free metal

266190, C21B 1100

Patent

active

061464406

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

The present invention relates to a process and an apparatus for the direct production of cast iron and, more specifically, to a process and an apparatus for the production of cast iron starting from iron bearing ore (hereinafter also indicated as "iron ore") of varying grain size and in various stages of oxidation.
Processes for the indirect production of cast iron from carbon coke and iron bearing ore made to undergo agglomeration are well known and tested and currently represent the only industrial process for production of cast iron in which the production capacity exceeds one million tons per year.
Processes for direct production of cast iron from non-coke carbon and iron bearing material which are not made to undergo agglomeration processes, and in which both materials have a low grain size, are only known on a pilot test level.
In particular, processes are known that have two stages.
A first stage for pre-reduction and pre-heating to a temperature at which the iron bearing ore starts to melt which takes place in a substantially cylindrical chamber, into which the iron bearing ore is driven by means of a plurality of nozzles in such a way as to give it a rotational motion along the walls of the chamber, thus increasing the time that it remains in contact with a reducing gas, for example carbon monoxide, supplied from the lower chamber.
And a second stage for final reduction of the pre-reduced matter obtained in the first chamber, which takes place in a second chamber positioned below the first one and in communication therewith, and normally referred to as a converter chamber, into which a fuel, for example fine coal, and an element supporting combustion, for example oxygen, are input to create a hot reducing gas capable of reducing the compound coming from the first pre-reduction chamber in a smelted condition through delivery of the gas produced in the first pre-reduction and pre-heating chamber.
In the first chamber the energy required by the chemical reactions and physical transformations that take place is provided by post-combustion of the reducing gas, generated by gasification of the coal, with the oxygen injected into the converter and the oxygen bound to the iron ore.
According to a method that forms part of the state of the art is known the use of a central nozzle for emission into the second chamber (converter) of fuel and oxygen.
The use of the central nozzle in the converter reduces the uniformity of distribution of the coal and oxygen with respect to the overall surface area of the metal bath at which these raw materials are aimed.
Furthermore, according to a method foreseen in the European Patent No. EP 0 690136, the central nozzle solution can cause problems in long-term operation of the cyclone; in effect this nozzle can become an obstacle to the uniform performance of the chemical reactions and create a surface on which deposits can form, resulting in partial blockage of the working area.
For this reason, in spite of the progress made to date in this field, the problems relating to processes for the direct and continuous production of cast iron from iron bearing ore, and the identification of apparatuses suitable to carry out said processes and capable of giving highly flexible production, remain substantially unsolved.
The aim of the present invention is therefore to provide a process for the direct and continuous production of cast iron and an apparatus suitable to carry out said process, said apparatus not involving the use of central nozzles, and being capable of guaranteeing a high level of production flexibility.
This aim is achieved by the present invention by means of the use of side nozzles to inject coal, flux and oxygen into the converter.
In fact in this way there is a greater uniformity of distribution of said materials throughout the cross section of the converter, more effective stirring of the slag which in this way increases the reduction kinetics and the heat exchange between slag/bath/gas, and greater flexibility in the post-combustion levels that can

REFERENCES:
patent: 5662860 (1997-09-01), Klassen et al.

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