[Walshbig]

Red mud is a byproduct from bayer process of alumina production. I would like to work on Titanium recovery from redmud. A quick googling indicates there are a lot of research methods around for this purpose but non is economically beneficial. Any suggestion which one is better to start with?

[Enthalpy]

Hi Walshbig, welcome here!

My coments aren't worth more than 2 cents as I'm outside of my skills here, but...

They say red mud is an environmental hazard primarily because it's alkaline. Would it be possible to separate Na and Ca oxides "just" with water and use them to capture CO₂? Reducing the CO₂ emissions of a plant means money.

Could a blast furnace, possibly built on purpose, be driven to reduce iron only, producing pig iron, and leave Al and Ti oxides as slag? If the iron contains some Al and Ti it's no worry, as these are desired for some kinds of steel, but all Al and Ti can't stay in Fe since the worldwide steel production can't absorb them.

[Enthalpy]

Valuable titanium is the incentive to process red mud, but I like increasingly the production of pig iron to remove Fe from Al, Ti and Si oxides.

Red mud (freed of Na and Ca oxides) is a very poor iron "ore" (50% Fe₂O₃) but it's free, or even, we want to get rid of it.

Aluminium plants are not installed near coal mines nor gas wells. Though, iron ore travels 800km by train in South Africa, so 2.5 times less coke can travel 2,000km if needed. Petrol coke (freed of sulphur!) could even travel from Alberta's oil sands deposits to Quebec's aluminium plants.

The blast furnace must be bigger to accommodate the iron-poorer red mud. At 0.25$/kg/yr for a complete plant it looks affordable.

More heat is necessary to pre-heat the iron-poorer red mud (but as much carbon to reduce only the iron oxide). I suggest to recycle this heat by injecting as well the slag in a modified cooper, in addition to the flue gas.

The amount of CO₂ is the same as if producing pig iron from good ore.

Alternately, perhaps the iron oxide can be melted away from aluminium, titanium and silicon oxides, prior to reduction in the blast furnace if pig iron is desired. Around 1560°C, Fe₂O₃ decomposes to Fe₃O₄ which melts at 1597°C while SiO₂, TiO₂ and Al₂O₃ keep solid up to 1713°C, 1843°C and 2072°C. It depends much on how the oxides combine in red mud and when heated - maybe, but maybe not. If sunlight is available all the year, 1km² of solar concentrators provide the heat for the red mud output of a typical aluminium plant - recycling the heat would improve. At averaged 3mm steel thickness, the concentrators' material costs 50M€.

Marc Schaefer, aka Enthalpy