Ilmenite/Rutile – Alpha Thermal Process

Titanium mineral concentrates of economic importance include ilmenite, leucoxene, rutile, titaniferous slag, and synthetic rutile.
Ilmenite is often beneficiated to produce synthetic rutile or titaniferous slag [Boateng, 2016]. Although numerous technologies are used to produce synthetic rutile, nearly all are based on either selective leaching or thermal reduction of iron and other impurities in ilmenite. Titaniferous slag with a TiO₂ content of 75% to 95% is produced commercially by rotary kilns processes..
TiO₂ pigment is produced from titanium mineral concentrates by either the chloride process or the sulfate process. In the sulfate process, ilmenite or titanium slag is reacted with sulfuric acid. Titanium hydroxide is then precipitated by hydrolysis, filtered, and calcined. In the chloride process, rutile is converted to TiCl₄ by chlorination in the presence of petroleum coke. TiCl₄ is oxidized with air or oxygen at about 1000° C (1800 F), and the resulting TiO₂ is calcined in rotary kilns to remove residual chlorine and any hydrochloric acid that may have formed in the reaction.
The sulfate process for the manufacture of titanium dioxide pigment involves feedstock prepared by digesting ilmenite ore with sulfuric acid following the reaction : FeTiO₃ + 2H₂SO4 = TiOSO₄ + FeSO₄ + 2H₂O.TiOSO₄TiO_2.nH₂O + H₂SO₄ = TiO₂nH₂O TiO₂ + nH₂O.
After a final wash and minor additions of materials to control crystallite growth the pulp is calcined rotary kilns. Rotary kiln calcination removes bound water, SO₂ and SO3 from the wet pulp feed. The acidic, gaseous effluent is scrubbed and recycled into the process. Crystallite growth and, where relevant, conversion to rutile occurs around 1000 °C depending on the pigment type being made. Cooling must be relatively slow to prevent the formation of trivalent titanium which would adversely affect pigment color. Kilns used for this process have short L/D’s and the feedstock is chemically produced at site as part of the process.