Bayer Process

After the creation of Bayer process, it has become the primary method for refining alumina. The Bayer process is composed of five steps. The steps can be described like the following series: mixing, digestion, clarification, precipitation and calcination.

First, the crushed ore is mixed with caustic soda in a grinding mill machine. Then, the produced slurry is pumped to a digester. The slurry is heated in the digester to 110-270 degrees for several hours to dissolve the aluminium compounds. After that, the slurry is transferred to a flash tank which reduces the pressure and recovers the heat.

Next, the slurry is pumped to a clarification tank where the impurities can settle at the bottom of the tank. Then, the liquid is pumped to a filter. Now any unwanted impurities are trapped by the filter. The bauxite residue in the clarification tank is taken and filtered to catch any useful residue. Then the remaining residue which called the “red mud” is transferred to a disposal pond. Next, the filtered liquid is moved to precipitation tanks.

In the tanks, seed crystals of alumina hydrate are added from the top of each tank. The crystals attract and attach the dissolved alumina to them while they precipitates. Then, the precipitated crystals are moved to a kiln. The kiln heats the crystals to isolate the alumina from the water molecules. Finally, the dry powder produced is shipped to aluminium smelter factory.