Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Patent
1982-03-31
1983-05-24
Vertiz, O. R.
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
423 83, 423 86, C22B 3412, C01G 4900, C01G 2300
Patent
active
043848834
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the metallization of the iron content of ferrotitaniferous materials, particularly naturally occurring ilmenites.
It is desirable to remove from ferrotitaniferous materials their iron content in order to make them more suitable for conversion to titanium containing products, chiefly titanium dioxide pigments.
BACKGROUND ART
There are several known methods of removing the iron content from ferrotitaniferous material. Most of these involve a reduction step to convert the iron content to a state whereby it may be conveniently separated from the relict titanium oxide material. For example in Australian Patent Specification No. 247 110 there is disclosed a multistep process for the upgrading of ilmenite wherein the ilmenite is reduced so that its iron content is metallized; the thus formed metallic iron is leached away from the titanium oxide material by a `rusting` process using an aqueous reagent. In another process described in U.S. Pat. No. 3,252,787 ilmenite is metallized and the iron content then removed by treatment with ferric chloride solution. In yet another process described in Australian Patent Specification No. 515 061 metallized ilmenite particles are subjected to a segregation treatment whereby small iron metal particles dispersed throughout each particle of metallized ilmenite are translocated and agglomerated to form large particles outside the relict particles.
For such processes which require removal of iron by means of reactions with liquids or gases it is desirable to have the metallic iron particles in a very fine state, homogeneously dispersed and accessible to the reactants through pores from the outside of the particles of metallized ferrotitaniferous material.
Studies on the reduction of ilmenite reported by G. Ostberg (Jernkont Ann 1960 144) (1) p. 46-76) showed that iron precipitated in grains of ilmenite by reduction occurred as discrete particles, the number of which per given volume was greater when hydrogen was used as the reductant than when carbon monoxide or solid carbon was used. The size of the particles was inversely proportional to the number. The number of particles could be increased by lowering the temperature used. These observations would indicate that to obtain a homogeneous dispersion of fine particles of metallic iron, hydrogen reduction should be used at the lowest practicable temperature. Unfortunately because of unfavourable reaction equilibria hydrogen reduction is considerably more costly to carry out than reduction with solid carbon.
DISCLOSURE OF INVENTION
However we have now discovered a process for the metallization of the iron content of ferrotitaniferous materials by which the metallic iron is formed as fine particles homogeneously dispersed within the grains of the material. This process involves partial metallization of the ferrotitaniferous material with hydrogen at a low temperature, followed by completion of the metallization process using a solid carbon reductant at a higher temperature.
Accordingly the present invention provides a process for the metallization of the iron content of ferrotitaniferous material, which process comprises in sequence, a first reduction step of heating the said ferrotitaniferous material to a temperature in the range of 600.degree. C. to 850.degree. C. in a reducing atmosphere comprising hydrogen gas so that more than 5% and not more than 50% of the iron content of the ferrotitaniferous material is converted to the metallic state, and a second reduction step of heating the product from the first reduction step containing residual oxidized iron to a temperature of at least 950.degree. C. in the presence of a solid carbonaceous material so that at least 90% of the iron content of the product from the second reduction step is in the metallic state.
It is essential in order to achieve the desired result from the process of the invention, namely the formation of fine particles of metallic iron, that at least 90%, and preferably at least 95%, of the iron content of the f
REFERENCES:
patent: 3252787 (1966-05-01), Shiah
Becker et al., "A New Process for Upgrading Ilmenite Mineral Sand", The Australasian Institute of Mining Metallurgy, No. 214, pp. 21-45, Jun. 1965.
ICI Australia Limited
Pak Chung K.
Vertiz O. R.
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