Becher process

The Becher Process is an industrial process used to upgrade ilmenite to synthetic rutile. [cite web|url=http://www.met.sgs.com/met_mineral_sands_metallurgy| title=SGS Metallurgical Services - Mineral Sands] .

The mineral, ilmenite contains 55-65% titanium as TiO₂, the rest being iron oxide. The Becher process removes the iron oxide, leaving a residue of synthetic rutile, which is more than 90% TiO₂. [cite web|url=http://www.chemlink.com.au/titan_rutile.htm| title=Rutile and ilmenite - Australian production and potential profile] .

History

This technology was developed in the early 1960s in Western Australia [cite web|url=http://www.australianminesatlas.gov.au/info/factsheets/titanium.jsp | title=Australian Atlas of Mineral Resources Mineral Sands Fact Sheet] by a joint initiative between industry and government. The process was named after Robert Becher, who invented, developed and introduced the technique to the Western Australian Mineral Sands industry. [cite web|url=http://www.cluniesross.org.au/the-awards/previous-award-winners/1992-award-winners/| title=ATSE Clunies Ross Foundation Medal Awards - 1992 ] The process was patented in 1961.Fact|date=March 2008

Process

The Becher Process is suitable for weathered ilmenite that has low concentrations of chromium and magnesium. [cite web|url=http://wwwscience.murdoch.edu.au/teach/m358/titanium.pdf| title=Murdoch University Titanium ] There are four steps involved in removing the iron portion of the ilmentite:
# Oxidation
# Reduction
# Aeration
# Leaching

Oxidation

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

: 4 FeTiO_{3 (s)} + O_{2 (g)} → 2 Fe₂O₃·TiO_{2 (s)} + 2 TiO_{2 (s)}

This allows for use of a wide range of ilmenite materials with varying Fe(II) and Fe(III) content to be used in the next step.

Reduction

Reduction is performed in a rotary kiln with pseudobrookite (Fe₂O₃.TiO₂), coal and sulfur, then heated to a temperature greater than 1200 °C. [cite web|url=http://www.education.cmewa.com.au/images/1_MineralSands.pdf| title=Chamber of Minerals and Energy Western Australia - Mineral Sands Factsheet ] The iron oxide in the mineral grains is reduced to metallic iron to produce reduced ilmenite:

: Fe₂O₃·TiO_{2 (s)} + 3 CO _(g) → 2 Fe _(s) + 2 TiO_{2 (s)} + 3 CO_{2 (g)}

Once the Reduced Ilmenite has cooled it is separated from the char by screening, then continues to the next step of the process.

Aeration

Aeration involves the removal of the metallic iron created in the last step by "rusting" it out. This 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 out of solution, away from the titanium dioxide portion in the form of a slime.

: 4 Fe _(s) + 3 O_{2 (g)} → 2Fe₂O₃

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 [cite web|url=http://www.wipo.int/pctdb/en/wo.jsp?WO=1994%2F03647&IA=WO1994%2F03647&DISPLAY=DESC| title=WIPO-WO/1994/003647) TREATMENT OF TITANIFEROUS MATERIALS ] .

References