Solid material comminution or disintegration – Processes – With application of fluid or lubricant material
Patent
1993-03-01
1997-01-21
Husar, John M.
Solid material comminution or disintegration
Processes
With application of fluid or lubricant material
241 23, 241 2414, B02C 1900, B02C 1912
Patent
active
055953476
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a process which enhances the extraction of ilmenite from deposits of mineral sands, or mineral concentrates thereof.
BACKGROUND ART
Mineral sands may contain many valuable minerals, among which are principally ilmenite, rutile, zircon, leucoxene, monazite and gold. These minerals are extracted by using differences in density and differences in the magnetic and electrical properties of the individual mineral species to separate them from the less valuable mineral components of the sands, and from each other.
Several prior art techniques are available for the separation of mineral sands into their valuable components. The most common method is generalized in FIG. 1 in block diagram form. The mineral sands are delivered as a wet raw sand to a gravity circuit (WET PLANT) to produce a coarse heavy mineral concentrate (HMC). This HMC may then be fed to a second stage where the magnetic properties of some of the component minerals are used to effect a further separation and concentration.
Ilmenite is a composite of iron and titanium oxides and is weakly magnetic. Highly magnetic minerals, such as magnetite, are removed from the HMC by a low intensity magnetic separator. The residual material may then be subjected to a wet high intensity magnetic separation (WHIMS) stage to concentrate the ilmenite. The WHIMS product may then be processed through an electrostatic stage in a DRY MILL.
The compound of particular interest for which ilmenite is the principal source is titanium dioxide, and the typical titanium dioxide concentration when the above prior art process is applied to ilmenite from the West Coast of The South Island of New Zealand ranges between 45%-47% TiO.sub.2 with typical assays of silicon dioxide (silica) in the range of 4% to 6% and dialuminium trioxide (alumina) of 2% to 2.5%. By contrast, concentrates of West Australian ilmenites commonly contain TiO.sub.2 in excess of 50%.
Due to the presence of iron oxides in ilmenite, the magnetic susceptibility of ilmenite can be increased by roasting under a variety of conditions. This increase in magnetic susceptibility is a well-known phenomenon and occurs through alteration of the chemical composition and crystalline structure, for example as discussed in the articles referred to below and allows the ilmenite to be readily separated from other minerals for example chromite, quartz, garnet and rutile, etc. by magnetic separation techniques.
One such prior art process is that operated by the Richards Bay Minerals (RBM) Company in South Africa which mines and treats raw sands which are high in chromite to recover ilmenite and other minerals. The raw sands are first processed through gravity and WHIMS circuits. The WHIMS separates the feed into non-magnetic and magnetic fractions, and the non-magnetic fraction, which contains rutile and zircon is then treated in a DRY MILL after being separated from the magnetic ilmenite/chromite fraction. The ilmenite/chromite fraction is roasted with excess oxygen at about 800.degree. C. for 40 minutes. This magnetizes the ilmenite and allows it to be separated magnetically from the chromite as described at pp. 555-8 of "Magnetic Methods for the Treatment of Minerals", by J. Svoboda, Elsevier (1987), or Australian Patent 502866.
Another process is described in GB 2043607 which describes roasting an ilmenite ore in an hydrous atmosphere to enhance its magnetic susceptibility to separate it from rutile as an "impurity".
Besides the above patents, articles describing magnetising roasting known to the applicant are by Curnow & Parry (Nature, Dec. 11, 1954, p. 1101, Journal and Proc. of the Royal Society of N.S.W. Vol. 89 [1955] p. 64), Ishikawa and Akimoto (Journal of Physical Society of Japan Vol. 12 No. 10, Oct. 1957; Vol. 13, No. 10, Oct. 1958) and Bozorth, Walsh & Williams (Physical Review Vol. 108, No. 1, Oct. 1, 1957, p. 1083).
The process described by Curnow & Parry is one of oxidation in air at temperatures between 600.degree. C. and 800.degree. C. A ferric to ferrous ratio of 1
REFERENCES:
patent: 2765074 (1956-10-01), Diamond
patent: 3022956 (1962-02-01), Haseman
patent: 3625354 (1971-12-01), Heitmann
patent: 4158041 (1979-06-01), Tolley
patent: 5035365 (1991-07-01), Birmingham
patent: 5127856 (1992-07-01), Oder
"Letters to the Editor, " Physical Review, vol. 108, No. 1, pp. 157-158, published Oct. 1, 1957.
"Ilmenite, " pp. 555-558 (undated).
Hanlon, F. N., Journal and Proceedings of the Royal Society of New South Wales for 1955, vol. LXXXIX, Part I-IV, pp. 64-72.
Ishikawa, Y., et al. "Magnetic Property and Crystal Chemistry of Ilmenite (MeTiO.sub.3) and Hematite (alpha-Fe.sub.2 O.sub.3) System, " Oct. 1958.
Ishikawa, Y., et al., "Magnetic Properties of FeTiO.sub.3 -Fe.sub.2 O.sub.3 Solid Solution Series, " vol. 12, No. 10, pp. 1084-1098, Oct. 1957.
Austpac Gold N.L.
Husar John M.
Schindler Edwin D.
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