The picture to the right illustrate the "Bayer Process" used at Sherwin Alumina.
Step 1 - Mixing: Crushed and Mixed with Caustic Soda, bauxite is pumped into huge digesters.
Step 2 - Digestion: Under high pressure and heat, the caustic soda dissolves the Alumina, or Aluminum Oxide, in the bauxite to form Sodium Aluminate.
Step 3 - Clarification: While the Sodium Aluminate remains in the solution, iron oxides and other solid impurities drop to the bottom of the settling tank, where, as red mud, they are pumped to a disposal pond.
Step 4 - Precipitation: After the Sodium Aluminate is further cooled, it is agitated and seeded with Aluminum Hydroxide crystals. These form larger crystals, which gradually settle out of the solution. Seed crystals and Sodium Aluminate remaining in the solution are then recirculated.
Step 5 - Calcination: The Aluminum Hydroxide crystals are roasted at more than 1800 degrees F to remove the water. A fine white powder, Alumina, remains half aluminum and half oxygen. It is then ready for transport to a smelter.