- Created by: Bree-Ffionn
- Created on: 03-09-19 21:00
- Aluminia is a material that retains its strength at high temperatures.
- It is chemically and physically stable at these high temperatures.
- It is a refractory material.
Alumina and aluminium extraction
- Alumina is extracted from bauxite ore using Bayer process.
- Bauxite is crushed to form grains.
- It is then mixed with liquor from the later precipitation stage amd crushed again to make a slurry .
- Bauxite can have a high leel of silica present so it may have to go through the descication process to remove this.
- Hot causstic soda solutiion is used to dissolve the aluminium-bearing minerals, gibbsite, bohmite and diaspore, in the bauxite, to form a sodium aluminate supersaturated solution.
- Conditions for this change due to the composition of the bauxide ores.
- Those with a high gibbsite content need about 140 degree cekcius, while those with a high bohmitic content need a higher temperature between 200 and 280 degree celcius.
- After digestion, slurry is cooled to around 106 degree celcius.
- Then the solids are seperated from the liquids via sedimentation.
- Chemical additives, flocculants are added to help the sedimentation process.
- Further seperation of the pregnant liquor from the bauxite residue is performing using a series of filters to ensiure that the final product is not contaminated with impurities present in the residue.