Becher process

The Becher process is an industrial process used to produce synthetic rutile, a form of titanium dioxide, from the ore ilmenite. It is competitive with the chloride process and the sulfate process, which achieve similar net conversions.^[1]^[2]

With the idealized formula FeTiO₃, ilmenite contains 55-65% titanium dioxide, the rest being iron oxide. The Becher process, like other beneficiation processes, aims to remove iron. The Becher process exploits the conversion of the ferrous iron (FeO) to ferric iron (Fe₂O₃).^[3] Ilmenite ores can be upgraded to synthetic rutile by increasing their TiO2 content to between 90 and 96 percent. ^[4]

History

This technology was developed in the early 1960s in Western Australia^[5] by a joint initiative between industry and government. The process was named after Robert Gordon Becher, who while working at the Western Australian Government Chemical Laboratories (the precursor to ChemCentre) invented, developed and introduced the technique to the Western Australian Mineral Sands industry.^[6] The process was patented in 1961.^[7]

Process

The Becher process is suitable for weathered ilmenite that has low concentrations of chromium and magnesium.^[8] There are four steps involved in removing the iron portion of the ilmenite:

Oxidation

Oxidation involves heating the ilmenite in a rotary kiln with air to convert iron to iron(III) oxide:

4 FeTiO₃ + O₂ → 2 Fe₂O₃·TiO₂ + 2 TiO₂

This step is suitable for a range of ilmenite-containing feedstocks.^[9]

Reduction

Reduction is performed in a rotary kiln with pseudobrookite (Fe₂O₃.TiO₂), coal, and sulfur, then heated to a temperature greater than 1200 °C.^[10] The iron oxide in the mineral grains is reduced to metallic iron to produce reduced ilmenite:

Fe₂O₃·TiO₂ + 3 CO → 2 Fe + TiO₂ + 3 CO₂

The "reduced ilmenite" is separated from the char prior to the next step.

Aeration

Aeration involves the removal of the metallic iron created in the last step by "rusting" it out. This conversion is achieved in large tanks that contain 1% ammonium chloride solution with air being pumped through the tank. The tank is being continuously agitated, and the iron will rust and precipitate in the form of a slime.

4 Fe + 3 O₂ → 2 Fe₂O₃

The finer iron oxide is then separated from the larger particles of synthetic rutile.

Acid leach

Once the majority of the iron oxide has been removed the remainder of it is leached away using 0.5M sulfuric acid.^[11]

References

^ Welham, N.J. (1996). "A parametric study of the mechanically activated carbothermic reduction of ilmenite". Minerals Engineering. 9 (12): 1189–1200. doi:10.1016/S0892-6875(96)00115-X.
^ Benson, L. L.; Mellor, I.; Jackson, M. (2016). "Direct reduction of synthetic rutile using the FFC process to produce low-cost novel titanium alloys" (PDF). Journal of Materials Science. 51 (9): 4250–4261. Bibcode:2016JMatS..51.4250B. doi:10.1007/s10853-015-9718-1.
^ "Rutile and ilmenite - Australian production and potential profile". Archived from the original on 2021-02-23. Retrieved 2008-03-01.
^ "Patent Landscape Report". WIPO. Retrieved 2023-10-19.
^ "Australian Atlas of Mineral Resources Mineral Sands Fact Sheet". Archived from the original on 2007-08-30.
^ "ATSE Clunies Ross Foundation Medal Awards - 1992".^{[permanent dead link]}
^ "Treatment of titanium-containing material". CLAIMS Patent Services. Retrieved 16 August 2016.
^ "Murdoch University Titanium" (PDF). Archived from the original (PDF) on 2006-12-01.
^ Bruckard, Warren J.; Calle, Carmen; Fletcher, Stephen; Horne, Michael D.; Sparrow, Graham J.; Urban, Andrew J. (2004). "The application of anthraquinone redox catalysts for accelerating the aeration step in the becher process". Hydrometallurgy. 73 (1–2): 111–121. doi:10.1016/j.hydromet.2003.09.003.
^ "Chamber of Minerals and Energy Western Australia - Mineral Sands Factsheet" (PDF). Archived from the original (PDF) on 2008-07-04.
^ "WIPO-WO/1994/003647 TREATMENT OF TITANIFEROUS MATERIALS".^{[permanent dead link]}