Roasting of titaniferous materials

Details Roasting of titaniferous materials Roasting of titaniferous materials

1996-09-10

1999-05-04

Andrews, Melvyn

Specialized metallurgical processes, compositions for use therei

Processes

Producing or treating free metal

75477, 266173, 423 86, C22B 3412

Patent

active

059000406

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates generally to the treatment of titaniferous materials, e.g. ores such as ilmenite, in a kiln such as a rotary kiln. Such processes include those in which at least part of the iron contained in the titaniferous ore is reduced to metallic iron or to the ferrous state. The metallic or ferrous iron, as the case may be, is typically removed to leave a titanium dioxide (TiO.sub.2) residue known as synthetic rutile. More particularly, this invention relates to an improved method for the introduction of reagents to the kiln.


BACKGROUND ART

Ilmenite, altered ilmenites and rutile are the major, commercially-important mineral feedstocks for titanium metal and titanium dioxide pigment production. Most of the world's mined ilmenite is used for the production of titanium dioxide pigments for use in the paint and paper industries. Pigment grade TiO.sub.2 has been traditionally produced by reacting ilmenite with concentrated sulphuric acid and subsequent processing to produce a TiO.sub.2 pigment--the so-called sulphate route. However this process is becoming increasingly unacceptable on environmental grounds due to the large volumes of acidic liquid wastes which it produces. The alternative process--the so-called chloride route--involves reaction with chlorine to produce volatile titanium tetrachloride and subsequent oxidation to TiO.sub.2. Unlike the sulphate route, the chloride route is capable of handling feedstocks, such as rutile, which are high in TiO.sub.2 content and low in iron and other impurities.
Consequently the chloride-route presents fewer environmental problems and has become the preferred method for TiO.sub.2 pigment production. Also, whilst the sulphate route is capable of producing only TiO.sub.2 pigments, both titanium metal and TiO.sub.2 pigments can be produced via the chloride route. Natural rutile supplies are insufficient to meet the world demands of the chloride-route process. Thus there is an increasing need to convert or upgrade the more-plentiful ilmenites and altered ilmenites (typically 45 go 62% TiO.sub.2) to synthetic rutile (containing over 90% TiO.sub.2).
Several processes are known for the production of synthetic rutile. The most commonly-practised process, usually referred to as the Becher process, involves the following main stages: ilmenite feed largely to metallic iron using coal as the heat source and the reductant, the resultant mixture of metallic iron and titanium phases being known as "reduced ilmenite". the metallic iron to iron oxide particles discrete from the TiO.sub.2 -rich mineral particles. -rich mineral comprising the synthetic rutile product. and manganese and magnesium.
In one advantageous but by no means exclusive application, the present invention is applicable to the first of these stages.
A paper entitled "Synthetic Rutile Operations of RGC Mineral Sands Limited at Capel and Narngulu, WA" ("Australasian Mining and Metallurgy", 1993, pp 1301 to 1304, published by The Australasian Institute of Mining and Metallurgy) describes, inter alia, reduction kiln operation including the feature of feeding coal to both the feed and discharge ends of the kiln.
Several other processes have been proposed for upgrading ilmenite or other ferro-titaniferous ores, and a number of these include a reduction step performed in a kiln.
One general class entails reduction of the iron to the ferrous state, followed by a direct acid leach of the kiln product to remove the iron. The so-called Murso process, described for example in British patent 1225826, involves a pre-oxidation of iron in the feed to the ferric state followed by reduction in a kiln, preferably using a gaseous reductant such as hydrogen, to the ferrous state or to a mixture of the ferrous and metallic states. Another process, known as the "Hybrid" process and disclosed for example in international patent publication WO91/13150, involves control of the temperature in the reduction kiln at a lower value than in the commercial Becher process so as to favour formation of a metatit

REFERENCES:
patent: 2814558 (1957-11-01), Halversen
patent: 3705795 (1972-12-01), Heitman
patent: 3988148 (1976-10-01), Queneau et al.
patent: 4378244 (1983-03-01), Kennelley et al.
patent: 4740239 (1988-04-01), Tuovinen et al.
patent: 5578109 (1996-11-01), Harris et al.

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