Process for upgrading titaniferous materials

Details Process for upgrading titaniferous materials Process for upgrading titaniferous materials

1996-04-01

1998-03-24

Andrews, Melvyn

Specialized metallurgical processes, compositions for use therei

Processes

Producing or treating free metal

75435, 423 83, C22B 102

Patent

active

057307741

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention relates to the removal of impurities from naturally occurring and synthetic titaniferous materials. The invention is particularly suited to the production of feed material for industrial chlorination systems, as used in the production of titanium metal and titanium dioxide pigments.


SUMMARY OF THE INVENTION

Embodiments of the present invention have the common feature of annealing or other heat treatment of temperature reduction processing. The annealing or heat treatment is conducted in such a manner that impurities which have been converted by high temperature treatment into forms which can only be leached with difficulty are transformed into forms from which impurities can be leached with relative ease. The annealing or heat treatment is followed at some stage by cooling and aqueous leaching as steps in an integrated process. Additional steps may be employed as will be described below.
In industrial chlorination processes titanium dioxide bearing feedstocks are fed with coke to chlorinators of various designs (fluidised bed, shaft, molten salt), operated to a maximum temperature in the range 700.degree.-1200.degree. C. The most common type of industrial chlorinator is of the fluidised bed design. Gaseous chlorine is passed through the titania and carbon bearing charge, converting titanium dioxide to titanium tetrachloride gas, which is then removed in the exit gas stream and condensed to liquid titanium tetrachloride for further purification and processing.
The chlorination process as conducted in industrial chlorinators is well suited to the conversion of pure titanium dioxide feedstocks to titanium tetrachloride.
However, most other inputs (i.e. impurities in feedstocks) cause difficulties which greatly complicate either the chlorination process itself or the subsequent stages of condensation and purification and disposal of waste. Table 1 provides an indication of the types of problems encountered. In addition, each unit of inputs which does not enter products contributes substantially to the generation of wastes for treatment and disposal. Some inputs (e.g. heavy metals, radioactives) result in waste classifications which may require specialist disposal in monitored repositories.
Preferred inputs to chlorination are therefore high grade materials, with the mineral rutile (at 95-96% TiO.sub.2) the most suitable of present feeds. Shortages of rutile have lead to the development of other feedstocks formed by upgrading naturally occurring ilmenite (at 40-60% TiO.sub.2),


TABLE 1 ______________________________________ Elemental Input Chlorination Condensation Purification ______________________________________ Fe, Mn Consumes Solid/liquid chlorine, chlorides coke, foul increases gas ductwork, volumes make sludges Alkali & Defluidise alkali fluid beds earth due to liquid metals chlorides, consume chlorine, coke Al Consumes Causes Causes chlorine, corrosion corrosion, coke makes sludges Si Accumulates Can encourage May require in duct distillation chlorinator, blockage. from product reducing Condenses in campaign part with life. titanium Consumes tetrachloride coke, chlorine V Must be removed, by chemical treatment and distillation Th, Ra Accumulates in chlorinator brickwork, radioactive; causes disposal difficulties ______________________________________ rutile (variously 92-95% TiO.sub.2). These upgrading processes have had iron removal as a primary focus, but have extended to removal of manganese and alkaline earth impurities, as well as some aluminium.
In the prior art, synthetic rutile has been formed from titaniferous minerals, e.g. ilmenite, via various techniques. According to the most commonly applied technique, as variously operated in Western Australia, the titaniferous mineral is reduced with coal or char in a rotary kiln, at temperatures in excess of 1100.degree. C. In this process the iron content of the mineral is substantially metallised. Sulphur ad

REFERENCES:
patent: 5063032 (1991-11-01), Gueguin

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