Chemistry of inorganic compounds – Oxygen or compound thereof – Metal containing
Patent
1991-08-15
1993-07-06
Morris, Theodore
Chemistry of inorganic compounds
Oxygen or compound thereof
Metal containing
423 78, 423 72, 423 74, 423341, 423343, C01G 23047
Patent
active
052251780
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a method for the extraction of titanium products occurring in titaniferous minerals, and more particularly to the recovery of titanium tetrafluoride from ilmenite and the like.
BACKGROUND OF THE INVENTION
Titaniferous materials are raw materials which serve as a source for titanium dioxide, titanium metal or other titanium compounds. Commercially viable titaniferous materials contain as low as 10% titanium dioxide and in excess of 95%. Most often the titanium is associated with other mineral types and the titaniferous portion is usually bound with an iron compound. Examples of titaniferous materials include ilmenite, leucoxene, rutile, anatase, titaniferous magnetite, vanadiferous magnetite, certain slags and synthetic rutiles obtained by reduction and leaching of ilmenite sands. The term thus generally includes other titanium bearing sands, ores, concentrates, slags, by-products and the like.
The most commonly mined forms of titanium as oxide are ilmenite and rutile. ilmenite beach sand concentrates typically contain titanium dioxide (40-60%), ferrous oxide (5-19%) and ferric oxide (24-25%) together with other metal oxides and residual silica. ilmenite rock concentrates are generally of lower titanium dioxide yield than sand concentrates. Australian rutile contains upward of 94-95% titanium dioxide with the balance chiefly as iron oxides.
Titanium dioxide in pure form is much in demand as a white pigment of high reflectivity which leads to a high opacity index. Non-pigmentary titanium dioxide is used in the manufacture of ceramics and for the production of titanium metal and for other purposes.
In the traditional "Sulphate" process for the recovery of titanium dioxide, ilmenite is digested with sulphuric acid: (SO.sub.4).sub.3 +TiOSO.sub.4 +5H.sub.2 O (1)
The liquor is clarified, filtered and mud residues are dumped. The filtered solution is fractionally crystallized under vacuum; iron sulphate being first removed by crystallization and filtration, the titanyl sulphate bearing solution being then concentrated, hydrolysed to an insoluble titanium oxide under critically controlled conditions to avoid occlusion of residual iron salts, and then filtered, washed and calcined. Conduct of the process has generally been considered to be costly and difficult to control and the process cannot be used efficiently with titaniferous minerals containing less than approximately 50% TiO.sub.2.
The other major process for the production of titanium oxide is the chloride process which requires a feedstock of high titanium concentration material such as rutile or synthetic rutile. The preferred process on environmental grounds is the chloride process and with the supply of rutile being limited plants must include a synthetic rutile plant.
Titanium tetrachloride is produced by direct chlorination of the rutile in a furnace or fluidised bed. Using petroleum coke mixed with rutile or synthetic rutile and chlorine gas chlorination proceeds rapidly at temperatures in the range of 800.degree.-1000.degree. C. The main products are titanium tetrachloride and carbon monoxide with smaller quantities of carbon dioxide and phosgene.
Titanium tetrachloride is usually oxidised to titanium dioxide by combustion with oxygen.
On chlorination Fe.sub.2 O.sub.3 in the titaniferous mineral is converted to FeCl.sub.3 which is volatile and must be separated from TiCl.sub.4 by fractional distillation. To the extent that there is residual FeCl.sub.3 in the TiCl.sub.4 the resulting white TiO.sub.2 will be discoloured, FeCl.sub.3 being converted on oxidation or hydrolysis to brown Fe.sub.2 O.sub.3.
Both the sulphate and chloride processes suffer from environmental problems and the pigment industry is continually looking for ways of overcoming this major issue and in the case of the chloride process there is a need for feedstock of high titanium content such as rutile or synthetic rutile.
In other suggested processes, the ilmenite has been digested with hydrochloric or nitric acids but these process
REFERENCES:
patent: 2900234 (1959-08-01), Jackson et al.
patent: 4220629 (1980-09-01), Wyndham et al.
patent: 4390365 (1983-06-01), Hard et al.
patent: 4629607 (1986-12-01), Gueguin
patent: 4629611 (1986-12-01), Fan
Chlorination of Ilmenite in a Fluidized Bed, L. K. Doraiswamy, et al, Oct. 1959, pp. 80-88.
O'Donnell Thomas A.
Pong Theresa K. H.
Wood David G.
Morris Theodore
Squillante Edward
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