Alumina and Aluminium Production Processes

What is the typical daily output of the largest and most productive cells in terms of aluminium?

What is the average current efficiency of the most productive aluminium cells?

Which ions are probable current-carrying ions in the electrolytic reaction?

What is produced at the cathode during the electrolytic reduction of aluminium?

How much thermal energy is required to produce one tonne of aluminium?

What form of alumina is produced in the temperature range of 400–600°C?

What is the primary benefit of using cryolite in the production of aluminium?

Which country experienced the highest increase in alumina production from 2005 to 2015?

What is the typical composition of the electrolyte used in the Hall–Héroult process for aluminium production?

What is the purpose of the gas collection system in an electrolytic-reduction cell?

At what typical temperature is a modern electrolytic-reduction cell operated?

What is the average world price for alumina in 2015?

What role do carbon anodes play in the Hall–Héroult process?

Alumina Production

Alumina production, typically 99.3-99.7% Al₂O₃, is created using the Bayer process.
The Bayer process removes alumina from bauxite, with crystallization occurring between 400°C and 600°C.
Further heating to up to 1200°C converts the alumina to α-alumina (relatively inert).
World alumina production increased from 64.6 million tonnes to 115.2 million tonnes between 2005 and 2015, with China's output increasing to 51% of the total.
The average world price of alumina was approximately US$250 per tonne in 2015.

Aluminium Production (Hall-Héroult Process)

Alumina (high melting point, poor electrical conductor) is dissolved in molten cryolite (Na₃AlF₆) in the Hall-Héroult process.
Electrolyte typically contains 80-90% cryolite, 2-8% alumina, and additives like AlF₃ and CaF₂.
Cryolite, initially obtained from Greenland, is now made synthetically.
Electrolytic-reduction cells (pots) use baked carbon anodes (which need replacing regularly), molten cryolite-alumina electrolyte, molten aluminium, and a carbon-lined container.
These cells operate at around 950°C, 500 kA, and ~0.7 A cm⁻² anode current density.
The anode and cathode are separated by 4-5 cm, with a voltage drop of 4-4.5 V per cell.
Modern cells operate with around 95% current efficiency and around 4,000 kg of aluminium daily.
Potlines comprise 150-300 cells connected in series.
Cells have frozen cryolite protection for carbon linings and an alumina crust on the electrolyte surface.
Aluminium is siphoned out and cast into ingots while alumina is replenished.
The electrolytic reaction mechanisms involve Na⁺, AlF₄⁻, AlF₆³⁻, and ternary complex ions like AlOF₃²⁻.
At the cathode, fluoroaluminate anions produce aluminium metal and fluoride ions.
At the anode, oxofluroaluminate ions release oxygen, forming CO₂.
The overall reaction simplifies to: 2 Al₂O₃ + 3 C → 4 Al + 3 CO₂

Magnesium Production (not detailed in this section)

A separate section discusses magnesium production in more detail.
Energy consumption is mentioned, but this information isn't detailed in this part.

Explore the processes of alumina and aluminium production, focusing on the Bayer and Hall-Héroult methods. Learn about the chemical properties, production statistics, and the role of electrolytic processes in aluminium manufacturing. This quiz will test your knowledge on both production methods and their significance in the global market.