Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Patent
1995-04-06
1996-11-26
Mai, Ngoclan
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
75395, 75414, 75612, 423 3, 423 20, 423111, 423155, C22B 6002
Patent
active
055781098
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for facilitating the removal of impurities, especially but not only radionuclides such as uranium and thorium and their radionuclide daughters, from titaniferous materials, and is concerned in particular embodiments with the removal of uranium and thorium from weathered or "altered" ilmenite and products formed from the ilmenite.
Ilmenite (FeTiO.sub.3) and rutile (TiO.sub.2) are the major commercially-important, mineral feedstocks for titanium metal and titanium dioxide production. Although ilmenite and rutile almost invariably occur together in nature as components of "mineral sands" or "heavy minerals" (along with zircon (ZrSiO.sub.4) and monazite ((Ce, La, Th)PO.sub.4)), ilmenite is usually the most abundant. Natural weathering of ilmenite results in partial oxidation of the iron, originally present in ilmenite in the ferrous state (Fe.sup.2 +), to ferric iron (Fe.sup.3 +). To maintain electrical neutrality, some of the oxidised iron must be removed from the ilmenite lattice. This results in a more porous structure with a higher titanium (lower iron) content. Such weathered materials are known as "altered" ilmenites and may have TiO.sub.2 contents in excess of 60%, compared with 52.7% TiO.sub.2 in stoichiometric (unaltered) ilmenite. As weathering, or alteration, of the ilmenite proceeds, impurities such as alumino-silicates (days) are often incorporated into the porous structure as discrete, small grains that reside in the pores of the altered ilmenite. It appears that uranium and thorium can also be incorporated into the ilmenite pores during this process.
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 undesirable 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 futile, 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 the more--plentiful ilmenites and altered ilmenites (typically 45 to 65 % TiO.sub.2) to synthetic ruffle (containing over 90% TiO.sub.2). A number of different processes have been developed to upgrade ilmenite to synthetic ruffle (SR), the most widely used, commercially, being the Becher process.
The Becher process involves reducing the iron in ilmenite (preferably altered ilmenite) to metallic iron in a reduction kiln at high temperatures to give so called reduced ilmenite, then oxidising the metallic iron in an aerator to produce a fine iron oxide that can be physically separated from the coarse titanium-rich grains forming a synthetic rutile. The product normally undergoes a dilute acid leach. Sulphur may be added to the kiln to facilitate removal of manganese and residual iron impurities, by formation of sulphides which are removed in the acid leach. The titanium-rich synthetic rutile so produced contains typically>90% TiO.sub.2.
Whether ilmenite is marketed as the raw mineral or as upgraded, value-added, synthetic rutile, producers are being increasingly required to meet more stringent guide-lines for the levels of the radioactive elements uranium and thorium in
REFERENCES:
patent: 2721793 (1955-10-01), Magri et al.
patent: 2815272 (1957-12-01), Armant et al.
patent: 2974014 (1961-03-01), Hoekje et al.
patent: 3502460 (1970-03-01), Martin et al.
patent: 3681047 (1972-08-01), Lynd et al.
patent: 3764651 (1973-10-01), Henkel et al.
patent: 3816099 (1974-06-01), Stewart et al.
patent: 3856512 (1974-12-01), Palmer et al.
patent: 3922164 (1975-11-01), Reid et al.
patent: 4097574 (1978-06-01), Auger et al.
patent: 4762552 (1988-08-01), Baldwin et al.
patent: 5011666 (1991-04-01), Chao et al.
patent: 5085837 (1992-02-01), Chao et al.
patent: 5181956 (1993-01-01), Chao
patent: 5411719 (1995-05-01), Hollitt et al.
patent: 5427749 (1995-06-01), Hollitt et al.
Aral Halil
Bruckard Warren J.
Freeman David E.
Grey Ian E.
Harris Harold R.
Mai Ngoclan
RGC Mineral Sands, Ltd.
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